{ "sample": "01-jechem-2023-defect-engineering", "threshold": 0.35, "cache_status": { "exists": true, "usable": true, "reason": "cache_page_count_ok", "expected_pdf_pages": 17, "cached_docling_pages": 17, "cached_docling_max_page": 17, "formula_enrichment_enabled": false, "formula_enrichment_scale": 3.0, "formula_nodes": 0, "recognized_formula_nodes": 0 }, "candidate_blocks": [ { "page": 1, "page_count": 17, "bbox": [ 37.59, 248.77, 546.65, 318.04 ], "text": "a Guangzhou Key Laboratory of Materials for Energy Conversion and Storage, Joint Laboratory of Energy and Materials Chemistry (South China Normal University-Guangzhou Tianci New Materials Co., Ltd.), Key Laboratory of Theoretical Chemistry of Environment, Ministry of Education, School of Chemistry, South China Normal University, Guangzhou 510006, Guangdong, China b National Engineering Research Center for Carbohydrate Synthesis, Key Lab of Fluorine and Silicon for Energy Materials and Chemistry of Ministry of Education, Jiangxi Normal University, Nanchang 330022, Jiangxi, China c Guangzhou Huifu Research Institute Co., Ltd, Nanxiang San Lu, Guangzhou 510663, Guangdong, China d Guangdong Provincial Key Laboratory of Quantum Engineering and Quantum Materials, National Demonstration Center for Experimental Physics Education, School of Physics and Telecommunication Engineering, South China Normal University, Guangzhou 510006, Guangdong, China", "category": "metadata", "coverage": 0.0, "words": 125 }, { "page": 1, "page_count": 17, "bbox": [ 202.17, 361.63, 557.65, 541.02 ], "text": "Despite the dazzling theoretical capacity, the devasting electrochemical activity of Li2MnO3 (LMO) caused by the difficult oxidation of Mn4+ impedes its practical application as the lithium-ion battery (LIB) cath- ode. The efficacious activation of the Li2MnO3 by importing electrochemically active Mn3+ ions or mor- phological engineering is instrumental to its lithium storage activity and structural integrity upon cycling. Herein, we propose a conceptual strategy with metal-organic frameworks (MOFs) as self- sacrificial templates to prepare oxygen-deficient Li2MnO3 (Ov-LMO) for exalted lithium storage perfor- mance. Attributed to optimized morphological features, LMO materials derived from Mn-BDC (H2BDC = 1,4-dicarboxybenzene) delivered superior cycling/rate performances compared with their counterparts derived from Mn-BTC (H3BTC = 1,3,5-benzenetricarboxylicacid) and Mn-PTC (H4PTC = pyromellitic acid). Both experimental and theoretical studies elucidate the efficacious activation of primitive LMO materials toward advanced lithium storage by importing oxygen deficiencies. Impressively, Ov-LMO derived from Mn-BDC (Ov-BDC-LMO) delivered intriguing reversible capacities (179.2 mA h g\u00011 at 20 mA g\u00011 after 200 cycles and 100.1 mA h g\u00011 at 80 mA g\u00011 after 300 cycles), which can be attributed to the small particle size that shortens pathways for Li+/electron transport, the enhanced redox activity induced by abundant oxygen vacancies, and the optimized electronic configura- tion that contributes to the faster lithium diffusivity. This work provides insights into the rational design of LMO by morphological and atomic modulation to direct its activation and practical application as an advanced LIB cathode. \u0001 2023 Science Press and Dalian Institute of Chemical Physics, Chinese Academy of Sciences. Published", "category": "metadata", "coverage": 0.76, "words": 271 }, { "page": 1, "page_count": 17, "bbox": [ 37.59, 626.54, 288.7, 676.46 ], "text": "Lithium-ion batteries (LIBs) have become indispensable electro- chemical energy storage and conversion devices due to their remarkable power density, satisfying cyclability, negligible mem- ory effect, and environmental friendliness since the emergence of the intensified energy crisis caused by the dwindling fossil fuel", "category": "scientific_body", "coverage": 0.842, "words": 42 }, { "page": 1, "page_count": 17, "bbox": [ 306.6, 597.12, 557.68, 688.87 ], "text": "[1]. Nevertheless, the development of the next-generation LIBs is bottlenecked by the dissatisfying electrochemical properties of the prevailing electrode materials. Following this, the exploration of high-performance cathodes and the innovation in cathode tech- nology become prerequisites for advanced LIBs, since cathode materials are crucial for the overall performance of LIB systems [2,3]. Relentless endeavors have been devoted to the modification and design of cathode materials for exalting electrochemical prop- erties during recent decades.", "category": "front_summary", "coverage": 0.915, "words": 75 }, { "page": 2, "page_count": 17, "bbox": [ 306.59, 67.43, 557.68, 138.27 ], "text": "space, and suppressed oxygen shearing leading to detrimental structural change, the as-reported oxygen vacancy-enriched LMO materials display expected superiority in lithium storage with superior reversible capacity, pronouncedly higher initial Coulom- bic efficiency, exalted rate capability, and prolonged cycle life [14,19,20], henceforth indicating the effectiveness of the oxygen- deficient strategy in LMO cathode modification.", "category": "scientific_body", "coverage": 0.741, "words": 58 }, { "page": 2, "page_count": 17, "bbox": [ 37.59, 67.44, 288.69, 148.7 ], "text": "(LMO) has been regarded as a promising alternative for the mercantile LIB cathode materials such as LiCoO2 (LCO), Li[NixCoy- Mn1\u0001x\u0001y]O2 (NCM), and LiFePO4 (LFP) due to its superiority in the- oretical capacity (460, 274, \u0003280, and \u0003170 mA h g\u00011 for LMO, LCO, NCM, and LFP, respectively) [4,5]. Despite the dazzling poten- tial to be utilized as a high-capacity LIB cathode, the practical application of LMO is hampered by the electrochemical inactivity related to the untoward oxidation of Mn4+ (less than 50 mA h g\u00011", "category": "scientific_body", "coverage": 0.884, "words": 90 }, { "page": 2, "page_count": 17, "bbox": [ 37.59, 151.11, 288.73, 305.63 ], "text": "for LMO microparticles) and safety hazards (huge irreversible capacity loss of \u0003130 mA h g\u00011 above 4.5 V) related to fatal O2 emission [6]. To tackle these obstacles, extensive efforts have been dedicated to the effectual activation and the optimized morpholog- ical and microstructural properties of LMO. Hitherto, several strategies have been applied to LMO to suppress structural degra- dation, exalt electrochemical activity, and enhance electronic con- ductivity, such as partial doping with other transition metal atoms, surface/interface modification, morphology control, nanorization, microstructural manipulation, construction of multiphase materi- als, utilization of conductive matrices/networks, and so on [7– 10]. Among these strategies, morphological and microstructural regulations are promising methodologies to promote lithium stor- age activity and extend cyclability on the premise of ensuring bat- tery energy density.", "category": "scientific_body", "coverage": 0.901, "words": 125 }, { "page": 2, "page_count": 17, "bbox": [ 306.59, 140.62, 557.72, 399.79 ], "text": "Inspired by these research advances, we systematically develop a multifunctional synthetic protocol to integrate the MOF- templated method and oxygen-deficient strategy for optimizing morphological and atomic structure. The 1,4-dicarboxybenzene-, 1,3,5-benzenetricarboxylicacid-, and pyromellitic acid-based Mn- MOFs (abbreviated as Mn-BDC, Mn-BTC, and Mn-PTC, respectively) were synthesized by solvothermal reaction and were later utilized as self-sacrificial templates to fabricate LMO (denoted as BDC-LMO, BTC-LMO, and PTC-LMO, respectively) by solid-state conversion. Afterward, stearic acid was employed as the reductant to prepare the oxygen vacancy-enriched LMO (denoted as Ov-BDC-LMO, Ov-BTC-LMO, and Ov-PTC-LMO, respectively). Experimentally, Ov-BDC-LMO outperforms its counterparts in electrochemical properties with an elevated specific capacity, boosted ion/elec- tronic conductivity, and remarkable multiplier performance due to the optimized morphological and electronic features. The theo- retical study also verifies the enticing advantages of Ov-LMO including amended lattice configuration, manipulated electronic structure, enhanced electrical conductivity, energetically favorable delithiation, and expedited Li+ migration, which further expounds the plausibility of experimental results. This work envisions a ver- satile strategy to maximize the complementarity of auspicious morphological features retained from MOF precursors and the oxy- gen vacancies facilitating electrochemical activation toward effica- cious modification of LMO for high-performance LIB application.", "category": "scientific_body", "coverage": 0.822, "words": 217 }, { "page": 2, "page_count": 17, "bbox": [ 306.59, 475.4, 557.69, 650.83 ], "text": "The Mn-MOFs with carboxyl-based ligands were prepared by solvothermal reactions according to the previous study [22,23]. Mn(CH3COO)2\u00044H2O (1 mmol) was dissolved in 6 mL of N,N- dimethylformamide (DMF)/methanol (VD: Vm = 5:1) hybrid solvent to obtain solution A, which was repeated three times. H2BDC (1 mmol), H3BTC (1 mmol), and H4PTC (1 mmol) were dissolved in 30 mL of DMF/methanol (VD: Vm = 5:1) to obtain solutions B, C, and D, respectively. Afterward, solution A was slowly poured into solutions B, C, and D, separately, and the mixed solutions were stirred at room temperature for 5 h, and then transferred into a 50 mL Teflon-lined stainless-steel autoclave and heated at 140 \u0003C for 24 h. After being cooled down to room temperature, the MOF was collected by centrifugation with a rotating speed of 10,000 r min\u00011 and washed three times thoroughly with methanol. Finally, the products were dried in an oven at 60 \u0003C for 12 h to obtain the Mn-MOFs powder with H2BDC, H3BTC, and H4PTC as organic ligands (denoted as Mn-BDC, Mn-BTC, and Mn-PTC, respectively).", "category": "metadata", "coverage": 0.889, "words": 194 }, { "page": 2, "page_count": 17, "bbox": [ 306.6, 653.24, 557.7, 755.43 ], "text": "The LMO materials without oxygen vacancy were fabricated via pyrolysis of the Mn-MOF templates with Li2CO3 as the Li source with a molar ratio of Li: Mn = 2.05:1. The dried MOFs were mixed with Li2CO3 by ball-milling and then calcined at 800 \u0003C for 8 h with a ramping rate of 5 \u0003C min\u00011 in air. Finally, the LMO materials with- out oxygen vacancy derived from Mn-BDC, Mn-BTC, and Mn-PTC were obtained (denoted as BDC-LMO, BTC-LMO, and PTC-LMO, respectively). To prepare the oxygen-deficient samples (denoted as Ov-BDC-LMO, Ov-BTC-LMO, and Ov-PTC-LMO, respectively), BDC-LMO, BTC-LMO, and PTC-LMO were calcinated at 340 \u0003C for", "category": "scientific_body", "coverage": 0.949, "words": 122 }, { "page": 3, "page_count": 17, "bbox": [ 306.6, 67.43, 557.69, 201.03 ], "text": "described by the Projected Augmented-Wave (PAW) potentials, while the exchange-correlation interactions were calculated by employing the Perdew-Burke-Enzerhof (PBE) pseudopotentials of Generalized Gradient Approximation (GGA) with a Hubbard U extension (U value) of 3.9 eV for Mn [25,26]. The vdW-D3 method developed by Grimme was employed to describe the van der Waals interaction [27]. The plane-wave energy cutoff was set to 450 eV. The convergence threshold was set to 1.0 \u0005 10\u00015 eV in energy and 0.02 eV per Angstrom in force. The Brillouin zone was modeled by the gamma-centered Monkhorst-Pack scheme, in which a 5 \u0005 3 \u0005 5 grid was adopted for LMO and Ov-LMO. The CINEB method was applied to compute the Li atom diffusion energy barrier.", "category": "metadata", "coverage": 1.0, "words": 130 }, { "page": 3, "page_count": 17, "bbox": [ 37.59, 119.71, 288.69, 347.47 ], "text": "The crystallographic data and phase analyses of the Mn-MOFs and LMO materials were implemented with an X-ray diffraction spectrophotometer (XRD, Ultima IV, Japan) using Cu Ka radiation with a scanning rate of 10\u0003 min\u00011 between 10\u0003 and 90\u0003. Thermo- gravimetric analysis (TGA, STA-409PC, Germany) was measured with an air flow of 10 mL min\u00011 and a ramping rate of 10 \u0003C min\u00011. The elemental configuration and interactions of LMO materials were detected using Raman spectroscopy (Renishaw inVia, UK) with a wavenumber scale of 50–2000 cm\u00011 using excitation light of 532 nm with an argon ion laser beam. The valence state and compositions of the particles were evaluated by X-ray photoelec- tron spectroscopy (XPS, Thermo Scientific K-Alpha+, USA). The elec- tron paramagnetic resonance (EPR) test was conducted at an amplitude of 2 G, a modulation frequency of 100 kHz, and a sweep width of 100 G for 80 s under a dark condition (JES FA200, Japan). The Brunauer-Emmett-Teller (BET) was implemented using an ASAP 2046 surface area and pore size analyzer (USA) at liquid nitrogen temperature (77 K). The morphologies and particle sizes of the obtained samples were analyzed with the field emission scanning electron microscope (FESEM, FEI Quanta 250 FEG, USA) and transmission electron microscopy (TEM, FEI Talos F200X, USA) with an energy-dispersive spectroscopy (EDS) system.", "category": "scientific_body", "coverage": 0.879, "words": 228 }, { "page": 3, "page_count": 17, "bbox": [ 306.6, 255.71, 557.68, 389.31 ], "text": "The synthetic procedure of Ov-LMO materials via solvothermal reaction, solid-state lithiation at high temperature, and low- temperature reduction is schematically illustrated in Fig. 1(a). The high phase purity and crystallinity of Mn-BDC, Mn-BTC, and Mn-PTC were examined by the XRD patterns, as depicted in Fig. S1(a). Simultaneously, the TGA measurement was conducted to investigate the pyrolysis temperatures of the MOF precursors, which indicates that MOF precursors are entirely decomposed at 450–600 \u0003C (Fig. S1b). The MOF precursors were meticulously cal- cined at 800 \u0003C with Li2CO3 as the Li source according to the TGA results to guarantee the high crystallinity of the LMO products [28,29]. Afterward, the Ov-LMO products were prepared by calcina- tion of LMO and stearic acid at a lower temperature of 340 \u0003C.", "category": "scientific_body", "coverage": 1.0, "words": 133 }, { "page": 3, "page_count": 17, "bbox": [ 37.59, 381.23, 288.72, 692.67 ], "text": "Electrochemical measurements of LMO were investigated using CR2032 coin cells. The cathode electrodes were prepared by using as-prepared LMO, acetylene black, and polyvinylidene fluoride (PVDF) with a weight ratio of 7:2:1 dispersed in N-methyl-2- pyrrolidone (NMP). Afterward, the slurry was coated onto alu- minum foil and dried at 110 \u0003C, while the electrodes were prepared as \u000312 mm disks with a mass load of active materials of \u00031.0 mg. In the half-cell system, the metallic Li, Celgard 2400, and a solution with 1 M LiPF6 in ethylene carbonate (EC), diethyl carbonate (DEC), and ethyl methyl carbonate (EMC) (the volume ratio of 1:1:1) were used as the counter electrode, separator, and electrolyte, respec- tively. The coin cells were assembled in an argon-filled glove box (H2O < 0.1 ppm, O2 < 0.1 ppm). The charge/discharge performances were performed by a battery test system (Land CT 2001A, China) between 2.0 and 4.8 V (vs. Li/Li+) at 40 mA g\u00011 and 25 \u0003C. The rate capabilities were assessed with the cell charged/discharged at mul- tiple current densities of 0.2, 0.4, 1, 2, and 5 C (1 C = 200 mA h g\u00011). The long cycling experiments of the LMO materials were evaluated at 25 \u0003C using a charge-discharge rate of 80 mA g\u00011. The cyclic voltammogram (CV) curves were measured from 2.0 to 4.8 V at scan rates of 0.2, 0.4, 0.6, 0.8, and 1.0 mV s\u00011 using an electrochem- ical workstation (CHI-660E, China). The electrochemical impe- dance spectroscopy (EIS) was estimated with an alternating current (AC) amplitude of 5 mV in the frequency ranging from 100 kHz to 0.01 Hz at room temperature. The galvanostatic inter- mittent titration technique (GITT) measurement was carried out to investigate the diffusion coefficient of lithium ions after 2 cycles for activation of the fresh coin cell at the current density of 20 mA g\u00011, during which the cell was alternately discharged/ charged for 4 min coupled with rest intervals of 1.0 h.", "category": "scientific_body", "coverage": 0.937, "words": 352 }, { "page": 5, "page_count": 17, "bbox": [ 306.59, 675.35, 557.69, 746.19 ], "text": "XPS measurements were implemented to elucidate the compo- sitional features and chemical states in LMO and Ov-LMO materi- als. The survey-scan XPS spectra reveal the coexistence of Li, Mn, and O in all samples, in which the C 1s signal at 284.8 eV was uti- lized to calibrate the binding energy (Fig. S4a–c). As presented in Fig. 2(d–f), the high-resolution Li 1s spectra verify the successful lithiation of Mn-MOFs by the as-proposed solid-state conversion", "category": "metadata", "coverage": 0.87, "words": 81 }, { "page": 5, "page_count": 17, "bbox": [ 37.59, 654.43, 288.72, 747.04 ], "text": "slightly shift toward the lower wave-number side with the emer- gence of shoulder peaks at \u0003630 cm\u00011 (Fig. S3a–c). These phenom- ena can be attributed to the strengthened MnAO bonds and the formation of spinel-structure domains in Ov-LMO [11,20]. To effi- caciously confirm the oxygen-deficient texture, EPR measurements were performed for LMO and Ov-LMO, during which the character- istics of both Mn4+ and oxygen vacancies can be identified. As expected, Ov-BDC-LMO (Fig. S3d), Ov-BTC-LMO (Fig. S3e), and Ov-PTC-LMO (Fig. S3f) jointly show broad Lorentzian (g = 1.998)", "category": "scientific_body", "coverage": 0.711, "words": 101 }, { "page": 6, "page_count": 17, "bbox": [ 306.59, 67.43, 557.7, 127.78 ], "text": "tributed on the well-retained primary structure, in turn manifest- ing the negligible destruction of primary particles by the low- temperature reduction [14,38], which ameliorates the surface property, provides abundant active sites, alleviates structural destruction, further enhances the electrochemical activity, and prolongs the cycle life.", "category": "scientific_body", "coverage": 0.975, "words": 44 }, { "page": 6, "page_count": 17, "bbox": [ 37.59, 67.44, 288.7, 159.98 ], "text": "strategy. The core-level O 1s spectra can be deconvoluted into 2 sub-peaks located at 531.8 and 529.3 eV (Fig. 2g–i), correlating to the surficial absorbed and lattice oxygen, respectively, whose intensity ratios (0.73, 0.69, 0.52, 0.41, 0.39, and 0.37 for Ov-BDC- LMO, Ov-BTC-LMO, Ov-PTC-LMO, BDC-LMO, BTC-LMO, and PTC- LMO, respectively) can be distinctly enhanced by oxygen vacancies [20,21]. The lattice oxygen trait is assignable to the O2\u0001 in the Li2MnO3 lattice, while the surficial absorbed oxygen signal origi- nates from the highly reactive peroxo-like (O2", "category": "metadata", "coverage": 0.78, "words": 104 }, { "page": 6, "page_count": 17, "bbox": [ 37.59, 149.47, 288.7, 212.31 ], "text": "2\u0001) oxygen radicals [35,36]. Moreover, the oxygen defects (the ones on the surface and sub-surface particularly) can significantly change the local environment of oxygen in LMO materials and trigger the formation of unbonded structure, thereby facilitating the generation of highly reactive O2", "category": "scientific_body", "coverage": 0.854, "words": 45 }, { "page": 6, "page_count": 17, "bbox": [ 37.59, 199.87, 288.67, 274.28 ], "text": "2\u0001 radicals and hence resulting in the enhanced O2 2\u0001 peak intensities [35]. According to the valence neutrality, Mn shows a single valence of 4+ in LMO and mixture valences of 3+ and 4+ in Ov-LMO. As expected, there are four deconvoluted peaks in the high-resolution Mn 2p spectra of Ov-BDC-LMO (Fig. 2j), Ov-BTC- LMO (Fig. 2k), and Ov-PTC-LMO (Fig. 2l), among which the charac- teristic peaks centered at 654.7 and 643.2 eV are attributed to Mn4+", "category": "metadata", "coverage": 0.925, "words": 84 }, { "page": 6, "page_count": 17, "bbox": [ 306.59, 170.39, 557.71, 410.23 ], "text": "g\u00011, respectively. The pore size distribution curves are exhibited in Fig. S5(b), in which Ov-BDC-LMO displays superior total pore volume compared with its counterparts. The pore sizes of Ov-BDC-LMO are scattered at 1.7–61.2 nm, while the ones of Ov-BTC-LMO and Ov-PTC-LMO are scattered in the range of 1.8– 88.9 and 3.4–53.7 nm, respectively, in turn, manifesting the hierar- chical micro-meso-macro mode for Ov-BDC-LMO and Ov-BTC-LMO as well as the meso-macro mode for Ov-PTC-LMO. The superior porosity is propitious to suppress volume variation, increase active sites, extend diffusion aisles, and enrich surface/interface defects, thereby favoring the diffusion kinetics and pseudocapacitive con- tribution [39,40]. Interestingly, preliminary characterizations jointly expound the higher oxygen defect concentration of Ov-BDC-LMO than Ov-BTC-LMO and Ov-PTC-LMO, which is related to the morphological feature and particle size. Size and morphol- ogy effects can synergistically influence the resultant Ov concentra- tion, during which smaller particle radius and larger surface area can afford more vacancy-acceptable sites and hence promote the Ov formation [41,42], and thus the resultant architectures derived from parent MOFs play a critical role in Ov levels. Bestowed by the enlarged surface area and extended vacancy-accepting layer, more oxygen defects can be generated in the BDC-derived samples during the low-temperature reduction procedure.", "category": "metadata", "coverage": 0.949, "words": 240 }, { "page": 6, "page_count": 17, "bbox": [ 37.59, 276.63, 288.72, 431.15 ], "text": "ions, while the ones centered at 653.3 and 641.8 eV are related to Mn3+ ions [29]. To further estimate the valence states of Mn, the high-resolution XPS spectra of Mn 3s of (Ov-)BDC-LMO (Fig. S4d), (Ov-)BTC-LMO (Fig. S4e), and (Ov-)PTC-LMO (Fig. S4f) are enclosed to calculate the average oxidation state (AOS). The AOS value can be assessed by the formula: AOS = 8.956 \u0001 1.126DE, where DE rep- resents the splitting energy between binding energies of the main peak and its satellite [20,32], by which the AOS values of Ov-BDC- LMO, Ov-BTC-LMO, and Ov-PTC-LMO can be estimated to be +3.55, +3.66, and +3.78, respectively. In contrast, the chemical valence of the Mn element in the oxygen vacancy-free samples can be calcu- lated to be 4.00 according to the above formula, which is in line with the deconvoluted results of the core-level Mn 2p spectrum. These results suggest that the concentration of oxygen defects can significantly manipulate the oxidation states of metal ions.", "category": "metadata", "coverage": 0.842, "words": 181 }, { "page": 6, "page_count": 17, "bbox": [ 306.59, 412.64, 557.7, 755.43 ], "text": "To further unveil the internal architectures of the LMO and Ov-LMO products, the TEM technique was adopted. As disclosed by the TEM images, BDC-LMO (Fig. 4a) and Ov-BDC-LMO (Fig. 4d) feature a layered architecture composed of film-like secondary particles with a diameter of 50–200 nm, which conforms to the SEM characterization. As expected, Fig. 4(b and e) displays the structural peculiarity of BTC-LMO and Ov-BTC-LMO with a larger particle diameter, while Fig. 4(c and f) demonstrates the larger par- ticle size of PTC-LMO and Ov-PTC-LMO. The high-resolution TEM (HRTEM) images of BDC-LMO (Fig. 4g), BTC-LMO (Fig. 4h), PTC- LMO (Fig. 4i), Ov-BDC-LMO (Fig. 4j), Ov-BTC-LMO (Fig. 4k), and Ov-PTC-LMO (Fig. 4l) profoundly record the conspicuous lattice fringes correlating to the (001) facets of the Li2MnO3 phase. Among them, the oxygen-deficient samples exhibit amplified interplanar distances and more distinct lattice distortion, indicating the crystal disarrangements and enlarged lattice parameters induced by the oxygen vacancies [21,43]. Correspondingly, the selected area elec- tron diffraction (SAED) patterns of BDC-LMO (Fig. 4m), BTC-LMO (Fig. 4n), PTC-LMO (Fig. 4o), Ov-BDC-LMO (Fig. 4p), Ov-BTC-LMO (Fig. 4q), and Ov-PTC-LMO (Fig. 4r) jointly feature the polycrys- talline diffraction rings indexed to the representative (001), (130), and (131) facets of the monoclinic Li2MnO3, indicating the satisfying phase purity. In addition, high-angle annular dark-field scanning TEM (HAADF-STEM) and corresponding element map- pings of BDC-LMO (Fig. 4s), BTC-LMO (Fig. 4t), PTC-LMO (Fig. 4u), Ov-BDC-LMO (Fig. 4v), Ov-BTC-LMO (Fig. 4w), and Ov-PTC-LMO (Fig. 4x) illustrate the homogeneous distribution of Mn and O. As mentioned above, the oxygen-deficient texture promotes the for- mation of lattice distortion, which is related to the atomic rear- rangement and the derived regional spinel regimes throughout the holistic layered structure [14,19,44,45]. As a result, Mn3+ ions can exist stably in the Li2MnO3\u0001x lattice by manipulating the atomic configuration and local structure with the integration of", "category": "scientific_body", "coverage": 0.894, "words": 354 }, { "page": 7, "page_count": 17, "bbox": [ 306.59, 475.4, 557.69, 692.67 ], "text": "oxygen-deficient strategy for the activation and optimization of Li2MnO3 as an advanced LIB cathode. Ov-BDC-LMO (Fig. 6a), Ov-BTC-LMO (Fig. 6b), and Ov-PTC-LMO (Fig. 6c) samples exhibit reversible capacities of 179.2, 117.0, and 97.5 mA h g\u00011, respec- tively, at 20 mA g\u00011 after 200 cycles, overperforming their counter- parts without oxygen vacancies (103.2, 62.4, and 17.3 mA h g\u00011 for BDC-LMO, BTC-LMO, and PTC-LMO, respectively). All samples bear prominent capacity increase and large capacity fluctuation over the initial 100 loops, the initial 50 cycles particularly, which can be attributed to the activation process through the phase transfor- mation with the generation of the spinel phase in the layered superstructure [48]. After the entire activation, it is noteworthy that all cathode materials underwent a capacity attenuation, which can be ascribed to the irreversible oxygen shearing and structural degradation upon repetitive (de)lithiation processes [17,49], resulting in inverted U-shaped cycling profiles for (Ov-)LMO sam- ples. Profiting from the facilitated activation induced by the oxygen-deficient nature, suppressed oxygen extraction, and miti- gated adverse phase destruction, the Ov-LMO samples present superior lithium storage capability, enhanced reversibility, and prolonged cycle life.", "category": "scientific_body", "coverage": 0.873, "words": 209 }, { "page": 7, "page_count": 17, "bbox": [ 37.59, 475.4, 288.72, 703.16 ], "text": "the predominant layered structure and minority spinel domain. To support this assumption from the atomic level, the spherical aberration-corrected HAADF-STEM and spherical aberration- corrected annular bright-field STEM(ABF-STEM) images are disclosed in Fig. 5, in which the oxygen-deficient samples exhibit spinel regimes in the layered bulk, thereby elucidating the local structure changes triggered by oxygen deficiencies [46,47]. The HAADF-STEM images can effectively visualize the cations, by which the different traits of layered and spinel structures can be identified with the arrangement of bright dots. LMO materials pre- sent a typical C2/m space group, while both majority C2/m and minority Fd3̅m features appear in Ov-LMO materials, thereby revealing the layered-spinel integrated structure induced by oxy- gen vacancies. Considering the insensitivity of HAADF-STEM to oxygen, ABF-STEM images were employed to visualize the oxygen vacancies in the lattice structures, in which the oxygen positions appearing brighter indicate oxygen vacancies. As expected, oxygen deficiencies can be detected in the Ov-LMO materials, while com- plete oxygen occupancies are available in the LMO counterparts. All these material characterization results verify the successful synthesis of the target products and the efficacious introduction of oxygen vacancies.", "category": "scientific_body", "coverage": 0.755, "words": 204 }, { "page": 8, "page_count": 17, "bbox": [ 306.6, 649.95, 557.7, 752.2 ], "text": "for Ov-BTC-LMO, Ov-PTC-LMO, BDC-LMO, BTC-LMO, and PTC-LMO, respectively) after the rate recovery. It is noteworthy that the Mn- BDC-derived samples outperform their counterparts derived from Mn-BTC and Mn-PTC in both cycling durability and rate capability, which is endowed with the rational selection of organic ligands improving particle growth and the optimized morphological fea- tures favoring the structural integrity during cycling [12,29]. As a supplement to the above deduction, the long-term cycling perfor- mances of Ov-BDC-LMO, Ov-BTC-LMO, and Ov-PTC-LMO at 0.4 C for 300 loops are presented in Fig. S6, which reveal the superior", "category": "metadata", "coverage": 1.0, "words": 109 }, { "page": 8, "page_count": 17, "bbox": [ 37.59, 639.52, 288.7, 752.2 ], "text": "respectively), and Ov-PTC-LMO (110.4, 97.6, 80.7, 57.8, and 39.5 mA h g\u00011 at 0.1, 0.2, 0.4, 1, and 2 C, respectively) at different current densities. In contrast, BDC-LMO (96.2, 76.3, 63.2, 43.4, and 37.9 mA h g\u00011 at 0.1, 0.2, 0.4, 1, and 2 C, respectively), BTC-LMO (80.2, 71.9, 63.8, 50.1, and 39.4 mA h g\u00011 at 0.1, 0.2, 0.4, 1, and 2 C, respectively), and PTC-LMO (71.4, 65.9, 50.5, 27.1, and 13.1 mA h g\u00011 at 0.1, 0.2, 0.4, 1, and 2 C, respectively) deliver sub- par rate capabilities due to their inferior electrochemical activity. Most samples deliver remarkable reversibility when the current density rebounds to 0.1 C, among which Ov-BDC-LMO displays a stable discharge capacity of 218.9 mA h g\u00011 surpassing the capac-", "category": "scientific_body", "coverage": 0.994, "words": 170 }, { "page": 9, "page_count": 17, "bbox": [ 37.59, 665.43, 288.72, 746.76 ], "text": "cycling durability of Ov-BDC-LMO with a reversible capacity of 100.1 mA h g\u00011 outperforming those of Ov-BTC-LMO (95.5 mA h g\u00011) and Ov-PTC-LMO (58.9 mA h g\u00011). Moreover, the cross-sectional SEM images are disclosed in Fig. S7 to embody the alleviated volu- metric fluctuation of the oxygen-deficient and the Mn-BDC- derived samples, further unraveling the exalted electrochemical performance induced by the optimized morphological and microstructural properties.", "category": "scientific_body", "coverage": 0.868, "words": 80 }, { "page": 9, "page_count": 17, "bbox": [ 306.6, 665.43, 557.72, 746.76 ], "text": "The galvanostatic charge/discharge (GCD) profiles of all samples performed at 20 mA g\u00011 were recorded to better demonstrate the working mechanism of the activation process of LMO and Ov-LMO electrodes. As depicted in Fig. 6(g–i) and Fig. S8(a–c), Ov-BDC-LMO, Ov-BTC-LMO, and Ov-PTC-LMO display superior initial Coulombic efficiency (ICE) of 68.6%, 62.7%, and 63.3%, respectively, while BDC-LMO, BTC-LMO, and PTC-LMO distinctly lag behind their oxygen-deficient counterparts with ICE of 34.2%, 39.9%, and", "category": "scientific_body", "coverage": 0.804, "words": 96 }, { "page": 10, "page_count": 17, "bbox": [ 37.59, 575.97, 288.69, 699.92 ], "text": "38.2%, respectively. Two successive charge plateaus can be observed at \u00033.9 and \u00034.4 V in the Ov-LMO samples during the first cycle, while merely a long voltage plateau appears above 4.4 V in the LMO samples, which can be ascribed to the structural reconstruction caused by severe oxygen extraction in the LMO phase and the buffering structural rearrangement in the Ov-LMO phase induced by the oxygen-deficient feature [19]. As the (dis) charge proceeds in the following cycle, the CE values of all samples stabilize at \u000395%, which illustrates the considerable reversibility of the redox reactions. Similar voltage plateau characteristics can be detected after the first cycle in all samples, revealing the redox couples of O2", "category": "scientific_body", "coverage": 0.866, "words": 123 }, { "page": 10, "page_count": 17, "bbox": [ 37.59, 687.49, 288.69, 731.28 ], "text": "2\u0001/O2\u0001, Mn4+/Mn3+, and Mn3+/Mn2+ from high to low voltage regions [50,51]. The GCD profiles at different current den- sities of all samples are also disclosed in Fig. S8(d–i), further testi- fying to the superiority of Ov-BDC-LMO in rate capability.", "category": "scientific_body", "coverage": 0.69, "words": 46 }, { "page": 11, "page_count": 17, "bbox": [ 37.59, 192.95, 288.7, 368.39 ], "text": "To further investigate the lithium diffusion kinetics, the formula DLi+ = R2T2/(2A2n4F4c2r2) was applied, where DLi+, R, T, A, n, F, c, and r symbolize the lithium-ion diffusion coefficient, gas constant, absolute temperature (in K), the area of circular electrodes, the number of electron migration in each mole of the active material, Faraday constant, the molar concentration of Li+, and the Warburg impedance coefficient calculated by the formula Z’ = Rct + Rs +rx\u00011/2, respectively [52]. According to the linear relationship between the real resistance and the reciprocal square root of the angular fre- quency, r values of these samples can be assessed, by which the DLi+ values of Ov-BDC-LMO, Ov-BTC-LMO, Ov-PTC-LMO, BDC-LMO, BTC-LMO, and PTC-LMO before cycling can be further estimated to be 1.44 \u0005 10\u000115, 1.20 \u0005 10\u000115, 3.00 \u0005 10\u000116, 1.19 \u0005 10\u000115, 3.79 \u0005 10\u000116, and 2.38 \u0005 10\u000116 cm2 s\u00011, respectively (Fig. S10a– c). Correspondingly, the DLi+ values after 100 cycles for the above samples can be calculated to be 2.20 \u0005 10\u000115, 2.16 \u0005 10\u000115, 5.10 \u0005 10\u000116, 1.44 \u0005 10\u000115, 4.95 \u0005 10\u000116, and 1.49 \u0005 10\u000116 cm2", "category": "scientific_body", "coverage": 0.751, "words": 209 }, { "page": 11, "page_count": 17, "bbox": [ 37.59, 369.16, 288.72, 472.99 ], "text": "s\u00011, respectively, according to the fitted r values (Fig. S10d–f). The elevated DLi+ values affirm the enhanced lithium diffusivity after cycling, which can be attributed to the favorable kinetics for ion migration triggered by oxygen vacancy doping [53]. Among these samples, PTC-LMO exhibits a reducing DLi+ value during cycling that is numerically smaller than that before cycling due to its structural inferiority. The EIS results show that morphological and microstructural manipulation is conducive to distinguished electronic/ion conductivity for enhanced lithium storage capacity and remarkable rate performance.", "category": "scientific_body", "coverage": 0.793, "words": 91 }, { "page": 11, "page_count": 17, "bbox": [ 37.59, 475.4, 288.71, 567.94 ], "text": "The CV curves were further studied to unveil the working mech- anisms of LMO and Ov-LMO in lithium storage. The CV curves for the initial three cycles of six samples are recorded in Fig. 7(a–f), which differentiate the working mechanisms of LMO and Ov-LMO and fur- ther exhibit the superior electrochemical properties of Ov-LMO. Three redox couples located at 3.3/2.8 V, 3.8/4.1 V, and 4.5/4.1 V can be detected in the CV curves of Ov-LMO, which can be assigned to the redox activities of Mn3+/Mn2+, Mn4+/Mn3+, and O2", "category": "scientific_body", "coverage": 0.939, "words": 103 }, { "page": 11, "page_count": 17, "bbox": [ 37.59, 557.49, 288.7, 651.68 ], "text": "2\u0001/O2\u0001, respectively [50,54], which conform with the GCD curves. It is of note that the oxidation peaks at \u00034 V appear during the first cycle in these CV curves, which is ascribed to the transformation from Mn3+ to Mn4+. In contrast, the LMO samples show more con- spicuous oxidation peaks at \u00034.5 V but hardly show traits of Mn4+/ Mn3+ during anodic scanning in the first cycle, which can be ascribed to the more severe oxygen extraction from the Li2MnO3 lattice and is detrimental to the structural integrity and cycling durability [20,46]. After the first cycle, the Mn3+/Mn2+, Mn4+/Mn3+, and O2", "category": "metadata", "coverage": 0.549, "words": 106 }, { "page": 11, "page_count": 17, "bbox": [ 306.59, 287.12, 557.69, 682.24 ], "text": "The quantitation of pseudocapacitive behaviors can be utilized to interpret the electrochemical kinetics, reflect the Li+ diffusion velocity, and further demonstrate the rate capability of electrode materials [5,52]. With this aim, the CV measurement was also per- formed at different scan rates from 0.2–1.0 mV s\u00011 to differentiate the diffusion-controlled and pseudocapacitive contributions of Ov-LMO and LMO. As demonstrated in Fig. S11(a–c), the CV profiles of Ov-BDC-LMO, Ov-BTC-LMO, and Ov-PTC-LMO show similar fea- tures with increasing current intensities as the sweep rate upgrades, indicating remarkable redox reversibility. The CV pro- files of BDC-LMO, BTC-LMO, and PTC-LMO at different scan rates are also recorded in Fig. S11(d–f) for better comparison, in which inferior symmetry and enlarged potential differences are pre- sented, revealing the subpar electrochemical reversibility. To pre- cisely quantify the pseudocapacitive contribution ratio related to non-Faradaic reactions, the power-law relationship of i = avb and the formula i = k1m + k2m1/2 can be employed, in which i, v, k1m, and k2m1/2 represent the peak current, scan rate, pseudocapacitive-dominant current, and diffusion-controlled cur- rent, respectively [56,57]. Based on the power-law relationship, the b values of peaks 1–4 for these samples can be determined by logarithmically fitting the peak current intensities against scan rates, as disclosed in Fig. S12(a–f). According to the linear fitting results, the estimated b values of Ov-BDC-LMO (0.954, 0.902, 0.825, and 0.830 for peaks 1–4, respectively), Ov-BTC-LMO (0.949, 0.876, 0.815, and 0.818 for peaks 1–4, respectively), and Ov-PTC-LMO (0.879, 0.867, 0.719, and 0.789 for peaks 1–4, respec- tively) are distinctly higher than those of BDC-LMO (0.832, 0.643, 0.588, and 0.518 for peaks 1–4, respectively), BTC-LMO (0.829, 0.603, 0.576, and 0.509 for peaks 1–4, respectively), and PTC- LMO (0.824, 0.532, 0.514, and 0.506 for peaks 1–4, respectively). The b value approaching 1 indicates the capacitive-dominant pro- cess, while the b value close to 0.5 suggests the diffusion- controlled behavior [56]. Therefore, the fitted results of b values demonstrate the preponderant pseudocapacitive contribution of the Ov-LMO materials compared to their primitive counterparts, thereby accelerating the ion diffusion process for more fabulous rate capability.", "category": "scientific_body", "coverage": 0.873, "words": 406 }, { "page": 11, "page_count": 17, "bbox": [ 37.59, 639.24, 288.72, 703.16 ], "text": "2\u0001/O2\u0001 redox couples located at 3.2/2.9 V, 4.2/3.4 V, and 4.6/4.0 V are available, among which the cathodic peaks at 2.9 and 3.4 V show increasing intensities as the cycling extends, elucidating the activation process via transformation from layered to spinel phase [51]. The amplified potential difference and aggravated asymmetry of the Mn4+/Mn3+", "category": "scientific_body", "coverage": 0.841, "words": 67 }, { "page": 11, "page_count": 17, "bbox": [ 306.6, 684.59, 557.67, 755.43 ], "text": "Predictably, the Ov-LMO samples (89.8%, 86.6%, and 79.7% for Ov-BDC-LMO, Ov-BTC-LMO, and Ov-PTC-LMO, respectively) hold superior pseudocapacitive contributions compared to their corre- sponding counterparts (51.9%, 45.2%, and 29.4% for BDC-LMO, BTC-LMO, and PTC-LMO, respectively) at the scan rate of 0.4 mV s\u00011, as depicted in Fig. 7(i–k) and Fig. S11(g–i), respectively. The pseudocapacitive contribution ratios at other scan rates for all", "category": "metadata", "coverage": 1.0, "words": 82 }, { "page": 13, "page_count": 17, "bbox": [ 306.6, 109.27, 557.7, 337.04 ], "text": "Additionally, a series of ex situ characterizations were conducted to further unearth the working mechanisms of the (Ov-)LMO during electrochemical measurements. It is widely sub- stantiated that LMO materials undergo oxygen loss and generation of new spinel phases during cycling, resulting in inverted U-shaped cycling curves [17,47–49]. In brief, the severe phase transforma- tion can cause intensified structural degradation and dissatisfying electrochemical performance. The ex situ XRD patterns of Ov-BDC- LMO (Fig. 8i) verify the phase transformation process as cycling proceeds, in which a negligible spinel trait can be detected before cycling and becomes more prominent after 50 and 100 cycles, indi- cating the formation of new spinel phases during repetitive delithi- ation/lithiation processes [46]. As expected, Ov-BTC-LMO (Fig. S22), Ov-PTC-LMO (Fig. S23), BDC-LMO (Fig. S24), BTC-LMO (Fig. S25), and PTC-LMO (Fig. S26) profoundly bear similar behaviors in local structure variations upon cycling, among which Ov-LMO samples show the suppressed structural change during cycling, while prim- itive LMO samples suffer from serious structural deterioration with the aggravated destruction of primitive layered structures. Hence, the significantly enhanced structural robustness of Ov-LMO origi- nates from the alleviated phase attenuation and maintenance of the local structure.", "category": "scientific_body", "coverage": 0.94, "words": 203 }, { "page": 13, "page_count": 17, "bbox": [ 37.59, 255.71, 288.7, 369.75 ], "text": "The galvanostatic intermittent titration technique (GITT) mea- surement was conducted to further support the effectiveness of the oxygen-deficient strategy for exalted lithium diffusivity of LMO materials. The whole-step profiles of GITT titration of Ov-BDC-LMO (Fig. S19a), Ov-BTC-LMO (Fig. S19b), Ov-PTC-LMO (Fig. S19c), BDC-LMO (Fig. S19d), BTC-LMO (Fig. S19e), and PTC- LMO (Fig. S19f) are recorded, in which the voltage fluctuation dur- ing relaxation in each titration step stands for the overpotential and indicates the polarization degree [45]. Simultaneously, the lower polarization degree represents the superior lithium diffusiv- ity, which can be quantified by employing the formula DLi+ =", "category": "scientific_body", "coverage": 0.765, "words": 106 }, { "page": 13, "page_count": 17, "bbox": [ 306.6, 339.39, 557.68, 410.23 ], "text": "Ex situ XPS spectra were employed to decipher the reaction mechanism during charge/discharge processes of (Ov-)LMO mate- rials during the initial cycle, by which the exalted structural stabil- ity of Ov-LMO can be investigated from the perspective of electron status. As displayed in Fig. 8(j), Mn ions in Ov-BDC-LMO feature a mixed valence state of 3+ and 4+ during the initial discharge pro- cess from 2.4 to 4.7 V. After the discharge process to 2.5 V, Mn3+", "category": "metadata", "coverage": 0.987, "words": 83 }, { "page": 13, "page_count": 17, "bbox": [ 37.59, 386.33, 288.72, 499.01 ], "text": "duration, molecular weight, molar volume, mass load of the active material, and area of the circular electrode, respectively [58,59]. This relationship is schematically demonstrated upon charging, as disclosed in Fig. 8(a–c) and Fig. S19(g–i), corresponding to the voltage response during delithiation processes (Fig. 8d–f and Fig. S20a–c). The above formula is also feasible for the lithiation processes, as depicted in Fig. S20(d–i). Furthermore, the calculated DLi+ values during delithiation and lithiation are portrayed in Fig. 8 (g) and Fig. S21, respectively, showcasing the accelerated lithium ion diffusion induced by the oxygen vacancies, which is in line with the pseudocapacitive investigations.", "category": "scientific_body", "coverage": 0.952, "words": 109 }, { "page": 13, "page_count": 17, "bbox": [ 306.6, 411.0, 557.67, 547.02 ], "text": "ions were partially reduced to Mn2+, corresponding to the sub- peaks at 652.6 and 641.2 eV [60]. For a better comparison, the valence state of Mn in BDC-LMO was studied (Fig. S27), which elaborates the transformation from single (4+ before charging) to hybrid valence (4+/3+ and 4+/3+/2+ when charged to 4.7 V and dis- charged to 2.5 V, respectively) of Mn ions. These findings indicate the oxygen emission in primitive LMO during the first cycle cou- pled with the partial reduction of Mn4+ and transition metal (TM) layer change that facilitates the activation during the following cycles [17,48]. The electron status of oxygen for Ov-BDC-LMO dur- ing the charge/discharge processes was also unveiled by the core- level XPS spectra of O 1s at different charge/discharge states, as delivered in Fig. S28. The increasing intensity of O2", "category": "metadata", "coverage": 0.821, "words": 144 }, { "page": 13, "page_count": 17, "bbox": [ 306.6, 576.48, 557.68, 661.32 ], "text": "2\u0001 feature when charged to 4.7 V and inferior O2\u0001 recovery after the discharge pro- cess (Fig. S29). The different electron configurations of oxygen in Ov-BDC-LMO and BDC-LMO elucidate the relieved lattice oxygen loss, enhanced TM layer stability, and inhibited local structure destruction induced by the oxygen-deficient nature [49,53], thereby favoring the exalted electrochemical activity and extended cyclability.", "category": "scientific_body", "coverage": 0.721, "words": 65 }, { "page": 13, "page_count": 17, "bbox": [ 306.6, 700.41, 557.7, 750.33 ], "text": "DFT calculation was implemented to theoretically verify the superiority of the Ov-LMO materials in lithium storage compared with the parent materials. Herein, the models of LMO (Fig. 9a and Fig. S30a) and Ov-LMO (Fig. 9b and Fig. S30b) were established and optimized to further substantiate the amended crystalline", "category": "scientific_body", "coverage": 1.0, "words": 50 }, { "page": 14, "page_count": 17, "bbox": [ 306.59, 620.08, 557.68, 690.91 ], "text": "and plausibility of the local built-in electric field assumption, thereby verifying the exalted lithium diffusivity related to the adventitious Coulomb force generated by the self-adaptive electric field around the vacancy area [34]. Consequently, it can be deduced that the charge accumulation around the oxygen defect sites elicits the auspicious electric force for expedited lithium ion transfer and unimpeded lithium storage reversibility.", "category": "scientific_body", "coverage": 0.831, "words": 63 }, { "page": 14, "page_count": 17, "bbox": [ 306.59, 693.32, 557.67, 753.67 ], "text": "Electronic conductivity is a crucial prerequisite condition for LIB electrodes, which was holistically investigated by calculating the total density of states (TDOS) profiles bound up with the Fermi level (denoted as Ef). As delivered in Fig. 9(d), both LMO and Ov-LMO exhibit semiconductive characteristics with apparent bandgap of 1.71 and 0.41 eV, respectively, between the valence", "category": "scientific_body", "coverage": 0.807, "words": 61 }, { "page": 16, "page_count": 17, "bbox": [ 37.59, 67.44, 288.71, 221.95 ], "text": "and conduction bands. The reduced band gap and pronouncedly denser DOS adjacent to the Fermi energy level delivered by the Ov-LMO indicate enhanced metallicity and impressive electronic conductivity. To further unravel the electronic states in detail, the partial density of states (PDOS) curves of LMO (Fig. 9e) and Ov-LMO (Fig. 9f) are calculated and compared. Noticeably, the 2p orbital of O and the 3d orbital of Mn appear closer to the vicinity of the valence band, indicating the prominently increased electron activity. This phenomenon can be ascribed to the facilitated excita- tion of the residual electrons around the oxygen-deficient region from the valence to the conduction band and the increased unpaired electrons in the Mn 3d orbital [32,61], which predomi- nantly manipulates the electronic structure and elevates the elec- tronic conductivity toward exceptional electrochemical performance.", "category": "scientific_body", "coverage": 0.842, "words": 137 }, { "page": 16, "page_count": 17, "bbox": [ 306.6, 67.43, 557.71, 284.7 ], "text": "reductant for the introduction of oxygen vacancies to ameliorate the electrochemical activity of LMO as an advanced cathode mate- rial for LIBs. The rational selection of MOF precursors efficaciously modulates the morphological and structural properties of the LMO products, among which Mn-BDC-derived LMO materials outper- form their counterparts due to the optimized morphology with smaller particle size, shortened diffusion aisles, increased active sites, and suppressed volume fluctuation. According to the experi- mental and theoretical findings, the successful introduction of oxy- gen vacancies facilitates the lithium storage activity of LMO materials with exalted reversible capacity, prolonged cycle life, and intriguing rate capability, which can be ascribed to the supe- rior redox activity, alleviated structural degradation related to oxy- gen emission and phase transition, boosted electronic/ion conductivity, and extra pseudocapacitive contribution kinetically favoring lithium storage induced by the oxygen-deficient texture. This study envisions a versatile methodology to amend the mor- phological feature and electronic structure of LMO by integrating the MOF-templated method and oxygen-deficient strategy, which provides a new avenue to activate the LMO material for advanced lithium storage.", "category": "scientific_body", "coverage": 0.84, "words": 179 }, { "page": 16, "page_count": 17, "bbox": [ 37.59, 220.79, 288.73, 368.39 ], "text": "As stated earlier, the ease of Li+ extraction is vital to the recon- struction and activation of the LMO electrodes to sustain electro- chemical activity, especially during the first cycle. To support this statement with more credible quantification, the Li+ extraction process can also be more precisely evaluated by calculating the energy barriers during delithiation, which follows the relationship: DE = E1 \u0001 E2 + E3, where DE, E1, E2, and E3 stand for the energy bar- rier during delithiation, energy after delithiation, energy before delithiation, and the energy of metallic Li utilized for calibration, respectively [62]. According to the relative energy at different states (Fig. S30d), the energy barriers upon delithiation of LMO (Fig. 9g) and Ov-LMO (Fig. 9h) can be mathematically determined to be 5.092 and 3.393 eV, respectively, uncovering the energeti- cally favorable delithiation process triggered by oxygen defects.", "category": "scientific_body", "coverage": 0.815, "words": 139 }, { "page": 16, "page_count": 17, "bbox": [ 306.6, 383.04, 557.67, 485.29 ], "text": "We gratefully acknowledge the financial support from the Spe- cial Funds for the Cultivation of Guangdong College Students’ Sci- entific and Technological Innovation (‘‘Climbing Program” Special Funds, pdjh2023b0145), the Research and Development Plan Pro- ject in Key Fields of Guangdong Province (2020B0101030005), the Applied special project of Guangdong Provincial Science and Technology Plan (2017B090917002), and the Basic and Applied Basic Research Fund of Guangdong Province (2019B1515120027). Furthermore, the authors would like to thank the Shiyanjia lab (https://www.shiyanjia.com) for the TEM test.", "category": "metadata", "coverage": 0.0, "words": 82 }, { "page": 16, "page_count": 17, "bbox": [ 37.59, 370.8, 288.7, 525.31 ], "text": "The experimental observations extensively illuminate the sig- nificantly expedited Li+ diffusion, which can be theoretically expounded by the calculated energy barriers of lithium vacancy migration. As displayed in Fig. 9(i), the relative energies at Sites I–V for LMO are 0, 0.25, 0.566, 0.351, and \u00010.052 eV, respectively. Meanwhile, the corresponding relative energies of 0, 0.211, 0.527, 0.141, and \u00010.089 eV at Sites I–V, respectively, for Ov-LMO are exhibited in Fig. 9(j). According to these findings, the minimum energy barriers for Li+ diffusing to the neighboring Li vacancy in LMO (Fig. S31a) and Ov-LMO (Fig. S31b) can be determined to be 0.566 and 0.527 eV, respectively. This observation anticipates the accelerated lithium diffusion and fast Li+ (de)intercalation kinetics in the oxygen vacancy-enriched lattice, which is endowed with expanded lattice space and extended pathways for ion migration and is adequately supported by experimental results.", "category": "scientific_body", "coverage": 0.929, "words": 160 }, { "page": 16, "page_count": 17, "bbox": [ 37.59, 527.67, 288.7, 692.67 ], "text": "Benefitting from the morphological and microstructural merits, the Ov-BDC-LMO reported in this study outperforms most of the counterparts mentioned in prior works in lithium storage capacity at various current densities, as depicted in Fig. S32. Taking the experimental and theoretical studies into account, the superiority in electrochemical properties of Ov-LMO is conferred by the follow- ing advantageous factors: (i) the enlarged lattice cell volume pro- viding magnified space for Li+ insertion and buffering volume variation; (ii) the modulated atomic arrangement and electronic configuration promoting ion/electronic conductivity; (iii) the ener- getically auspicious delithiation facilitating activation for the boosted redox activity and splendid reversible capacity; (iv) the expedited Li+ transmission contributing to preponderant pseudocapacitive-dominant behaviors and extraordinary rate capability; (v) the rationally tailored morphology exposing more active sites and maximizing the electrode/electrolyte contact.", "category": "scientific_body", "coverage": 0.895, "words": 137 } ], "low_coverage_blocks": [ { "page": 1, "page_count": 17, "bbox": [ 37.59, 248.77, 546.65, 318.04 ], "text": "a Guangzhou Key Laboratory of Materials for Energy Conversion and Storage, Joint Laboratory of Energy and Materials Chemistry (South China Normal University-Guangzhou Tianci New Materials Co., Ltd.), Key Laboratory of Theoretical Chemistry of Environment, Ministry of Education, School of Chemistry, South China Normal University, Guangzhou 510006, Guangdong, China b National Engineering Research Center for Carbohydrate Synthesis, Key Lab of Fluorine and Silicon for Energy Materials and Chemistry of Ministry of Education, Jiangxi Normal University, Nanchang 330022, Jiangxi, China c Guangzhou Huifu Research Institute Co., Ltd, Nanxiang San Lu, Guangzhou 510663, Guangdong, China d Guangdong Provincial Key Laboratory of Quantum Engineering and Quantum Materials, National Demonstration Center for Experimental Physics Education, School of Physics and Telecommunication Engineering, South China Normal University, Guangzhou 510006, Guangdong, China", "category": "metadata", "coverage": 0.0, "words": 125 }, { "page": 16, "page_count": 17, "bbox": [ 306.6, 383.04, 557.67, 485.29 ], "text": "We gratefully acknowledge the financial support from the Spe- cial Funds for the Cultivation of Guangdong College Students’ Sci- entific and Technological Innovation (‘‘Climbing Program” Special Funds, pdjh2023b0145), the Research and Development Plan Pro- ject in Key Fields of Guangdong Province (2020B0101030005), the Applied special project of Guangdong Provincial Science and Technology Plan (2017B090917002), and the Basic and Applied Basic Research Fund of Guangdong Province (2019B1515120027). Furthermore, the authors would like to thank the Shiyanjia lab (https://www.shiyanjia.com) for the TEM test.", "category": "metadata", "coverage": 0.0, "words": 82 } ], "high_risk_body_missing_blocks": [], "front_summary_missing_blocks": [], "back_matter_low_overlap_blocks": [] }