{ "sample": "03-jpowsour-2015-severe-truncation", "threshold": 0.35, "cache_status": { "exists": true, "usable": true, "reason": "cache_page_count_ok", "expected_pdf_pages": 8, "cached_docling_pages": 8, "cached_docling_max_page": 8, "formula_enrichment_enabled": false, "formula_enrichment_scale": 3.0, "formula_nodes": 0, "recognized_formula_nodes": 0 }, "candidate_blocks": [ { "page": 1, "page_count": 8, "bbox": [ 197.23, 550.9, 552.89, 624.97 ], "text": "Succinonitrile (SN) has been used as functional additive to improve the thermal stability and broaden the oxidation electrochemical window of commercial electrolyte 1 M LiPF6/EC/DEC (1:1, by volume) for high- voltage LIBs (cathode: Li1.2Ni0.2Mn0.6O2, anode: Li). 1 wt % SN-based electrolyte showed a wide elec- trochemical oxidation window of 5.4 V vs Liþ/Li and excellent thermal stability demonstrated by ther- mogravimetry (TG) and X-ray photoelectron spectroscopy (XPS), as well as theoretical analysis according to molecular orbital theory. The LNMO (Li1.2Ni0.2Mn0.6O2) battery with 1 wt % SN-based electrolyte showed better cyclability and capacity retention when charged to higher cut-off voltage. The improved battery performance is mainly attributed to the formation of uniform cathode electrolyte interface (CEI)", "category": "front_summary", "coverage": 1.0, "words": 125 }, { "page": 2, "page_count": 8, "bbox": [ 311.53, 155.29, 562.57, 216.47 ], "text": "the equation, then water content drops down which relieves the process of LiPF6 decomposed into HF at the same time. In total, not only does it can eliminate H2O and HF which would promote Mn/ Ni dissolution from the cathode, but also reduce the side reaction due to the formation of non-electrochemical active amide (RCONH2).", "category": "scientific_body", "coverage": 1.0, "words": 56 }, { "page": 2, "page_count": 8, "bbox": [ 311.53, 416.81, 562.58, 487.54 ], "text": "In this paper we studied succinonitrile (SN) as a commercial electrolyte additive to improve the cycling performance and ther- mal stability of the Li1.2Ni0.2Mn0.6O2/Li system in high cut-off voltage. Furthermore, the chargeedischarge capacities of Li1.2Ni0.2Mn0.6O2/Li with different cut-off voltages has been studied, and the effect of SN on the performance of the cells and reactions for the LNMO cathode were also discussed.", "category": "scientific_body", "coverage": 0.896, "words": 71 }, { "page": 2, "page_count": 8, "bbox": [ 311.53, 552.93, 562.63, 665.56 ], "text": "The electrolyte of 1 M LiPF6 dissolved in ethylene carbonate (EC): Diethyl carbonate (DEC) (1:1, by volume), which was pur- chased from Zhangjiagang Guotai Huarong Chemical New Material Co. Ltd (named commercial electrolyte). SN-based electrolytes were prepared simply by mixing succinonitrile (SN, 99%, J&K Chemical) with the prepared electrolyte in various weight ratios in an argon-filled glovebox (H2O < 0.1 ppm, O2 < 0.1 ppm, Mikrouna) and stirring for 24 h at room temperature, We have tested the water content of commercial electrolyte and 1wt % SN-based electrolyte by Karl-fisher method, 8.7 ppm and 7.6 ppm was measured respectively.", "category": "scientific_body", "coverage": 0.901, "words": 105 }, { "page": 3, "page_count": 8, "bbox": [ 301.83, 66.33, 552.9, 126.57 ], "text": "of commercial electrolyte seems high (5 V), in fact, the actual voltage limits of the electrolyte are usually much lower than those obtained with an inert electrode because of the highly catalytic characteristic of the cathode materials [5]. And the trivial change guarantee the feasibility of the EC-DEC/SN mixed solvent for high voltage cathode materials.", "category": "scientific_body", "coverage": 1.0, "words": 57 }, { "page": 3, "page_count": 8, "bbox": [ 32.82, 87.25, 283.91, 157.98 ], "text": "Li1.2Ni0.2Mn0.6O2 electrode material was prepared by copreci- pitation according to the previous work [27]. The electrode con- sisted of Li1.2Ni0.2Mn0.6O2, acetylene black and PVDF in a weight ratio of 8:1:1, coating onto aluminum foil. The active mass loading was more than 1.8 mg/cm2. The Li/Li1.2Ni0.2Mn0.6O2 coin-type half- cells (2025) were assembled in the argon-filled glovebox, and cel- gard 2400 was used as battery separator.", "category": "scientific_body", "coverage": 0.861, "words": 76 }, { "page": 3, "page_count": 8, "bbox": [ 301.83, 129.09, 552.89, 241.66 ], "text": "The highest occupied molecular orbital (HOMO) energy level and the lowest unoccupied molecular orbital (LUMO) energy level can be calculated based on the molecular orbital theory, which reflects the ability to gain or lose electrons. Fig. 2(c) shows the frontier molecular orbitals of EC and DEC, as well as SN, and their energies are also shown using a B3LYP basis set. The energies of the LUMO and HOMO of SN (\u00030.30127 ha, \u00030.04180 ha) are both lower than those of EC (\u00030.25168 ha, \u00030.01248 ha) and DEC (0.23381 ha, 0.00220 ha). It indicates that SN molecules can accept electrons and possess a high oxidation potential, and the introduction of SN can also broaden the oxidation potential of the commercial electrolyte.", "category": "metadata", "coverage": 0.919, "words": 128 }, { "page": 3, "page_count": 8, "bbox": [ 32.82, 191.85, 283.95, 262.58 ], "text": "The electrolytes oxidation/reduction potentials were tested by an electrochemical workstation (CHI660E, Shanghai Chenhua Company) using a linear sweep voltammogram at a scan rate of 1 mV s\u00031 at 25 \u0004C in the voltage range from \u00030.2 V to 6.0 V. The electrolyte was sealed in a glass cell. The working electrode is a platinum wire (99.9%, Ø ¼ 0.1 mm) and the reference and counter electrode is Li foil (99.9%).", "category": "scientific_body", "coverage": 1.0, "words": 75 }, { "page": 3, "page_count": 8, "bbox": [ 32.82, 265.04, 283.95, 325.34 ], "text": "Electrochemical impedance spectra (EIS) were measured with a Zahner Elektrik IM6e impedance analyzer over the frequency range of 10\u00033 Hz ~ 106 Hz. The electrolyte ionic conductivity was tested by Pt conductance electrode from \u000330 \u0004C to 80 \u0004C in the program- mable high-low temperature test chamber (GDJS-100, Wuxi Suoyate Company).", "category": "scientific_body", "coverage": 0.896, "words": 52 }, { "page": 3, "page_count": 8, "bbox": [ 32.83, 505.65, 283.95, 555.46 ], "text": "The surface species on the cycled cathodes was tested by X-ray photoelectron spectroscopy (XPS) using a chemical analysis (ESCA) spectrometer (PHI-1600, USA), radiated with a monochromatized Al-Ka (1486.6 eV) source, and the spectra results were analyzed by XPS-PEAK software.", "category": "scientific_body", "coverage": 0.85, "words": 44 }, { "page": 3, "page_count": 8, "bbox": [ 301.83, 575.32, 552.89, 649.62 ], "text": "and Mn4þ on the cathode, leading to the destruction of the cathode due to the manganese dissolution into electrolyte and the Jahne- Teller crystallographic distortion [31]. In the meantime, the elec- trolyte with redundant SN may form a thick CEI layer leading to a higher Rct value. When taken all these experiment results into ac- count, 1wt % SN-based electrolyte was believed to be the most optimal electrolyte system for the LNMO batteries.", "category": "scientific_body", "coverage": 0.97, "words": 70 }, { "page": 3, "page_count": 8, "bbox": [ 301.83, 652.14, 552.95, 743.79 ], "text": "Thermal stability and cycling performance at high temperature Fig. 4(a) and (b) and show the thermal stability of commercial electrolyte and 1wt % SN-based electrolyte. The TG profile indicates that both of two samples begin to lose weight from ambient tem- perature, but commercial electrolyte decays quickly. When the two samples decomposed 10% of onset amount, the temperature for 1wt % SN-based electrolyte (55.5 \u0004C) is higher than commercial electrolyte (49.2 \u0004C), this is mainly because of the thermal decomposition temperature of SN (267 \u0004C) is higher than the two", "category": "metadata", "coverage": 0.955, "words": 93 }, { "page": 5, "page_count": 8, "bbox": [ 32.82, 251.7, 283.89, 344.73 ], "text": "main solvent EC (248 \u0004C) and DEC (125.8 \u0004C), the addition of SN leads to the tiny overall thermal stability improvement. The DTG profile shows the decomposition rate of the electrolyte, and the two peaks respectively represent the temperature for two mainly components (EC and DEC). From Fig. 3(a) and (b), it is obvious that decomposing temperature in two peaks for 1wt % SN-based elec- trolyte is higher, and the value of decomposing rate is smaller in the meantime. The results show that succinonitrile additive can improve the thermal stability of the commercial electrolyte.", "category": "metadata", "coverage": 0.957, "words": 96 }, { "page": 5, "page_count": 8, "bbox": [ 32.82, 347.19, 283.95, 501.6 ], "text": "To further clarify the thermal stability of the mixed electrolyte, the cycle performance of the half-cells at high temperatures (55 \u0004C) has been investigated. The cells were placed in a battery-testing incubator and tested by a Land battery testing system at a voltage range of 2.0e4.8 V, at a current density of 0.1 C. As shown in Fig. 5, the initial discharge capacity of the Li/Li1.2Ni0.2Mn0.6O2 half-cell containing the 1wt % SN-based electrolyte is 268.7 mAhg\u00031. After 50 cycles, the discharge capacity is higher than 240 mAhg\u00031 and the coulombic efficiency is over 95% from the 2nd cycle. The discharge capacity of Li/Li1.2Ni0.2Mn0.6O2 half-cell with commercial electro- lyte is less than 170mAhg\u00031 after 50 cycles and retains only 66.8% of its initial capacity. The coulombic efficiency of the last few cycles is lower than 90%. By contrast, in the first few cycles, the coulombic efficiency of the cell containing the 1wt % SN-based electrolyte is lower than the cell with commercial electrolyte. It implies that SN-", "category": "scientific_body", "coverage": 0.886, "words": 188 }, { "page": 5, "page_count": 8, "bbox": [ 301.83, 252.99, 552.95, 574.85 ], "text": "derived cathode electrolyte interface (CEI) forming in the first few cycles causes an irreversible capacity loss. The improvement in the thermal stability maybe due to the strong complex formation be- tween the surface metal atoms of Li1.2Ni0.2Mn0.6O2 and nitrile (eCN) groups of SN except for the thermal stability improvement of electrolyte itself [25]. The inset shows the SEM images of the cathode surface with or without SN after 50 cycles. The inset on the right (1wt % SN) shows much more homogeneous CEI layer than the left inset (commercial electrolyte). The better CEI layer ensures the higher capacity retention of battery with electrolyte containing 1wt % SN. Fig. 6 shows the discharge capacity of Li/Li1.2Ni0.2Mn0.6O2 half- cells with or without SN under different upper cut-off voltage. Fig. 6(a), (b), (c) and (d) are corresponding to 2.0e4.8 V, 2.0e4.9 V, 2.0e5.0 V and 2.0e5.2 V respectively. At all present cut-off voltage, the cycle performance of cell with 1wt % SN-based electrolyte is better than that with commercial electrolyte. When the cut-off voltage is between 2.0 and 4.8 or 4.9 V, they exhibited nearly identical cycling characteristics. When charging to 5.0 V, the discharge capacity of cell with 1wt % SN-based electrolyte can remain 223.8 mAhg\u00031 after 50 cycles, while cell with commercial electrolyte discharge capacity drops to 186.2 mAhg\u00031. It is due to the faster degradation rate of EC and DEC at higher voltage. The discharge capacity of cell with 1wt % SN-based electrolyte (2.0e5.2 V) decays faster than when they were charged to 5.0 V, but it is still much better than the cell with commercial electrolyte. The cell with commercial electrolyte nearly broke down after 20 cycles. These results demonstrate that the addition of succinonitrile to the electrolyte solution leads to a remarkably improved cycling sta- bility, which is due to the formation of electronically conductive film on the cathode.", "category": "scientific_body", "coverage": 0.877, "words": 336 }, { "page": 6, "page_count": 8, "bbox": [ 311.53, 592.28, 562.63, 736.25 ], "text": "displayed in Fig. 8(e) and (f). A satellite peak (S1) near 860 eV was observed in both two samples, indicating nickel oxides on the cathode surface [33]. However, there is much difference in Ni 2p3/2 signal. The SN-absent sample signal located at 854.2 eV, suggesting a single valence of Ni2þ. In contrast with SN-absent sample, a shoulder peak of 856 eV identified the existence of Ni3þ in SN- containing sample. In summary, the XPS results prove that the introducing of SN contributes to produce compounds containing Ni3þ and Mn3þ in the cathode surface. The interaction between electronegativity group CN\u0003 and Ni3þor Mn3þ needed for further research. Although it is not accurate to judge the Mn/Ni deposition amount based on the half-peak width area. But the fact can't be ignorable that the area of Mn/Ni peak of 1wt % SN-based electrolyte was respectively 1/3 and 1/2 of commercial electrolyte. It implies", "category": "scientific_body", "coverage": 0.823, "words": 162 }, { "page": 7, "page_count": 8, "bbox": [ 32.82, 462.16, 283.98, 700.25 ], "text": "Succinonitrile-based electrolytes improve the cycling perfor- mance and thermal stability of the Li1.2Ni0.2Mn0.6O2/Li system in high cut-off voltage in this paper. By performing linear sweep voltammetry (LSV), thermogravimetry (TG) and X-ray photoelec- tron spectroscopy (XPS), the results showed that the commercial electrolyte containing 1wt % SN has a better thermal stability and wider electrochemical oxidation window to 5.4 V, which is corre- sponding to the theoretic calculation results. The energies of the LUMO and HOMO of SN are both lower than those of EC and DEC. At a voltage range of 2.0e5.0 V,1wt % SN-based electrolyte was proved to be the optimal proportion for LNMO batteries. SN also has an outstanding ability to form a CEI layer observed from SEM images, which contributes to the alleviation of Mn/Ni dissolution into electrolyte and deposition on the cathode. Cycling tests of Li/ Li1.2Ni0.2Mn0.6O2 half-cells under different upper cut-off voltage confirm that Li/Li1.2Ni0.2Mn0.6O2 half-cells containing 1wt % SN- based electrolyte exhibits a better capacity retention and higher coulombic efficiency than commercial electrolytes. In summary, 1wt % SN-based electrolyte shows a wider electrochemical oxida- tion stability window and better thermal stability, as well as its good compatibility with LNMO electrodes. As a result, deployment of succinonitrile-based electrolyte can lead to long life and safer lithium-ion batteries for automobile and grid applications.", "category": "scientific_body", "coverage": 0.901, "words": 236 } ], "low_coverage_blocks": [], "high_risk_body_missing_blocks": [], "front_summary_missing_blocks": [], "back_matter_low_overlap_blocks": [] }