Long cycle electrolyte for lithium-rich manganese-based lithium ion battery
By introducing nitriles, silanes, fluorinated carbonates, and sulfonates as additives into lithium-rich manganese-based lithium-ion batteries, a stable electrochemical interface membrane is formed, solving the problem of declining cycle performance of lithium-ion batteries and achieving a high-efficiency improvement in cycle performance.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- BEIJING UNIV OF TECH
- Filing Date
- 2024-11-29
- Publication Date
- 2026-05-29
AI Technical Summary
Existing lithium-rich manganese-based lithium-ion batteries suffer from performance degradation due to side reactions in terms of cycle performance, including positive electrode transition metal dissolution, surface structure instability, irreversible oxygen release, and increased negative electrode interface impedance.
Nitrile compounds, silane compounds, fluorinated carbonate compounds, and sulfonate compounds are used as additives to work synergistically in the electrolyte to form stable electrochemical interface films (CEI and SEI) to stabilize the positive and negative electrodes and improve lithium-ion migration efficiency.
It significantly improves the first-cycle coulombic efficiency and cycle performance of lithium-ion batteries, with a capacity retention of no less than 83% after 650 cycles, and some reaching 94%.
Smart Images
Figure HDA0005163533700000011
Abstract
Description
Technical Field
[0001] This invention belongs to the field of lithium-ion battery electrolyte technology, specifically relating to the preparation and application of a lithium-rich manganese-based lithium-ion battery long-cycle electrolyte. Background Technology
[0002] In recent years, the rapid development of science and technology and the continuous progress of human society have brought about serious environmental pollution problems and energy shortage crises. Due to the discontinuity and unpredictability of renewable energy, energy storage technology has become a key link in its full and rational utilization. Lithium-ion batteries, as an electrochemical energy storage technology, have received widespread attention, and the development of lithium-ion batteries with superior performance is of great significance to their application research. Among the cathode materials currently being studied, lithium-rich layered oxide (LLO) cathode materials have attracted researchers' attention and become one of the research hotspots due to their high operating voltage, theoretical capacity, and relatively low cost.
[0003] Electrolytes, acting as the medium for ion transport between the positive and negative electrodes, play a crucial role in the performance of lithium-ion batteries. Side reactions caused by the contact between the positive and negative electrodes and the electrolyte, such as the dissolution of transition metals at the positive electrode, unstable transformations of surface structures, irreversible oxygen release, and increased interfacial impedance, poor kinetics, and lithium dendrite growth at the negative electrode, are the main reasons for the decline in battery cycle performance. Introducing additives is an electrolyte modification strategy with advantages such as low cost, ease of operation, and significant effects. Nitrile compounds have high adsorption energy on the layered oxide positive electrode side, stabilizing the positive electrode and inhibiting transition metal dissolution. Silane compounds can preferentially oxidize and decompose, filling the CEI at the positive electrode and facilitating lithium ion migration; furthermore, their Lewis basic groups can capture H2O or HF, thus preventing interfacial corrosion. Due to the presence of strongly electron-withdrawing fluorine atoms, fluorinated carbonate compounds can preferentially reduce and decompose at the negative electrode, and fluorine-rich inorganic SEIs can prevent the continuous decomposition of carbonate-based electrolytes. Lithium sulfate and alkyl sulfonate SEIs formed by the electron-withdrawing reduction of sulfonates containing high-valence sulfur at the negative electrode improve the ion transport kinetics of SEIs by increasing their ionic conductivity.
[0004] Therefore, from the perspective of constructing a robust and stable CEI and a low-impedance SEI, the development of electrolytes that synergistically combine additives with unique functions is of great significance for improving the long-cycle performance of lithium-rich manganese-based lithium-ion batteries. Summary of the Invention
[0005] The technical problem to be solved by the present invention is to provide a lithium-rich manganese-based lithium-ion battery long-cycle electrolyte.
[0006] To solve the above-mentioned technical problems, the present invention provides the following technical solution:
[0007] A lithium-rich manganese-based lithium-ion battery long-cycle electrolyte is characterized in that the electrolyte comprises an organic solvent, a lithium salt, and additives; wherein the additives comprise one or more of nitrile compounds, silane compounds, fluorinated carbonate compounds, and sulfonate compounds, each additive accounting for 0-5 wt% of the total mass of the electrolyte and none of them being 0, and each additive preferably being 0.5-3 wt%.
[0008] The nitrile compounds are one or more selected from SUN, ADN, HTCN, EGBE, and 1,2,3-tris(2-cyanoxy)propane; the silane compounds are one or more selected from TMSB, TMSP, and TMSPi; and the fluorinated carbonate compounds are fluoroethylene carbonate, fluoropropylene carbonate, and monofluorocarbon. The additive comprises one or more of dimethyl carbonate, methyl trifluoroethyl carbonate, 2,2-difluoroethyl methyl carbonate, and trifluoroethyl ethyl carbonate; the sulfonate compound comprises one or more of 1,3-propanesulfonate lactone, methanedisulfonate methylene ester, propenyl-1,3-sulfonate lactone, and trimethylsilyl methanesulfonate; wherein the concentration of the nitrile compound is 0-5 wt%, the concentration of the silane compound is 0-5 wt%, the concentration of the fluorinated carbonate compound is 0-5 wt%, and the concentration of the sulfonate compound is 0-5 wt%, and none of the above substances is 0.
[0009] The organic solvent is one or more of ethylene carbonate, dimethyl carbonate, diethyl carbonate, methyl ethyl carbonate, sulfolane, dipropyl sulfone, dimethyl sulfoxide, and propylene carbonate mixed in different proportions, preferably a mixture of ethylene carbonate, dimethyl carbonate, and diethyl carbonate.
[0010] The lithium salt is one or more selected from lithium hexafluorophosphate, lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethyl)sulfonyl)imide, lithium tetrafluoroborate, lithium di(oxalate)borate, lithium di(fluorooxalate)borate, and lithium difluorophosphate, preferably lithium hexafluorophosphate. The lithium salt concentration is 0.1–5 mol / L. -1 1 mol L -1 .
[0011] The electrolyte of the present invention is prepared by the following method: at room temperature, in a glove box protected by argon (oxygen and water content <0.1ppm), the lithium salt, the organic solvent and the additive are mixed and stirred for 12 hours to completely dissolve them, resulting in a clear and transparent solution.
[0012] The lithium-rich manganese-based lithium-ion battery long-cycle electrolyte is used to match lithium-rich layered oxide cathode active materials.
[0013] The lithium-ion battery includes a positive electrode, a negative electrode, and the lithium-rich manganese-based lithium-ion battery long-cycle electrolyte described above.
[0014] The positive electrode active material of the lithium-ion battery is a lithium-rich manganese-based layered oxide positive electrode material. The preparation of the positive electrode includes the following steps: grinding and mixing 70-99% by mass of the positive electrode active material and 0.5-29% by mass of the conductive agent acetylene black, adding 0.5-29% by mass of polyvinylidene fluoride (PVDF) binder, adjusting the viscosity with 1-methyl-2-pyrrolidone (NMP), which is not included in the mass percentage composition of the positive electrode material; coating the positive electrode material onto the surface of aluminum foil and drying to obtain the positive electrode.
[0015] The lithium-ion battery negative electrode active material is one or more of the following: lithium metal, lithium metal alloy, natural graphite, artificial graphite, mesophase carbon microspheres, hard carbon, and soft carbon materials. Lithium metal and lithium metal alloy can be directly used as the corresponding negative electrode. The preparation of the negative electrode includes the following steps: grinding and mixing 10-100% by mass of the negative electrode active material and 0-80% by mass of the conductive agent acetylene black; adding 0-80% by mass of polyvinylidene fluoride (PVDF) binder and mixing; adjusting the viscosity with 1-methyl-2-pyrrolidone (NMP), which is not included in the mass percentage composition of the negative electrode material; coating it on the surface of copper foil and drying it to obtain the negative electrode.
[0016] Advantages of this invention: This invention combines additives with unique functions to work synergistically, improving the first-cycle coulombic efficiency and also improving cycle performance, so that the capacity retention rate is not less than 83% after 650 cycles, and some even have a capacity retention rate of 94% after 800 cycles. Attached Figure Description
[0017] Figure 1 These are the cycle retention curves of lithium-rich manganese layered oxide-graphite (LLO|Gr) batteries corresponding to the electrolytes of Comparative Examples 1 and 3 of this invention. Detailed Implementation
[0018] The present invention will be illustrated by specific embodiments below. These embodiments are provided to better understand the present invention and are by no means intended to limit the scope of the present invention.
[0019] The endpoints of the ranges and any values disclosed herein are not limited to the precise ranges or values, and these ranges or values should be understood to include data close to these ranges or values. For numerical ranges, the endpoint values of the various ranges, the endpoint values of the various ranges and individual point values, and individual point values can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.
[0020] Preparation and testing of lithium-ion batteries with lithium-rich cathodes:
[0021] In the embodiments, the electrolyte was prepared at room temperature in an argon-protected glove box (oxygen and water content <0.1ppm). The synergistic lithium salt, the organic solvent, and the electrolyte additive were mixed in a certain proportion and stirred for 12 hours to completely dissolve them, resulting in a clear and transparent solution.
[0022] In this embodiment, the battery assembly uses a standard CR2032 coin cell, with LLO as the positive electrode active material. This positive electrode active material, conductive agent acetylene black, and binder PVDF are mixed and ground in an 8:1:1 ratio to create the positive electrode material, which is then pressed onto an aluminum foil current collector to form the positive electrode. Graphite is used as the negative electrode active material. This negative electrode active material, conductive agent acetylene black, and binder PVDF are mixed and ground in an 8:1:1 ratio to create the negative electrode material, which is then pressed onto a copper foil current collector to form the negative electrode. A glass fiber separator and a selected electrolyte are used, and assembly is completed in a glove box filled with high-purity argon (99.99%) gas, where both moisture and oxygen content are below 0.1 ppm. The assembled battery is sealed under 50 MPa pressure on a coin cell sealing machine and allowed to stand for 12 hours before further testing. The assembled battery is then subjected to constant current charge-discharge testing on a LAND battery tester, with the first charge-discharge current density being 20 mAg. -1 The cutoff voltage is 2.5-4.3V, and the cyclic charge / discharge current density after the second cycle is 200mAg. -1 Cut-off voltage 2.5-4.3V.
[0023] Comparative Example 1
[0024] At room temperature, in an argon glove box, 1 mol L of lithium salt was... -1 LiPF6 was added to a solvent with an EC:DMC:DEC volume ratio of 1:1:1. The mixture was heated and stirred at 40°C for 12 hours to obtain a clear and transparent liquid, which was then allowed to stand at room temperature for use as an electrolyte.
[0025] The battery assembly uses the electrolyte described above, and the electrode fabrication process is the same as the battery assembly process. The assembled battery was then subjected to a constant current charge-discharge test at 25°C using a LAND battery tester, with the first charge-discharge current density being 20 mAg. -1 The cutoff voltage is 2.5-4.3V, and the cyclic charge / discharge current density after the second cycle is 200mAg. -1 The cutoff voltage is 2.5-4.3V. The first-cycle coulombic efficiency is 58.1%, and the capacity retention after 200 cycles is 42.1%.
[0026] Example 1
[0027] At room temperature, in an argon glove box, 1 mol L of lithium salt was...-1 LiPF6 was added to a solvent with an EC:DMC:DEC volume ratio of 1:1:1, along with 2 wt% fluoroethylene carbonate, 1 wt% 1,2,3-tris(2-cyanoxy)propane, 1 wt% tris(trimethylsilane)boronic acid ester, and 1 wt% 1,3-propanesulfonate lactone as a synergistic additive. The mixture was heated and stirred at 40°C for 12 hours to obtain a clear, transparent liquid, which was then allowed to stand before use as an electrolyte.
[0028] The battery assembly uses the electrolyte described above, and the electrode fabrication process is the same as the battery assembly process. The assembled battery was then subjected to a constant current charge-discharge test at 25°C using a LAND battery tester, with the first charge-discharge current density being 20 mAg. -1 The cutoff voltage is 2.5-4.3V, and the cyclic charge / discharge current density after the second cycle is 200mAg. -1 The cutoff voltage is 2.5-4.3V. The first-cycle coulombic efficiency is 81%, and the capacity retention rate is 88.6% after 650 cycles.
[0029] Example 2
[0030] At room temperature, in an argon glove box, 1 mol L of lithium salt was... -1 LiPF6 was added to a solvent with an EC:DMC:DEC volume ratio of 1:1:1, along with 2 wt% fluoroethylene carbonate, 1 wt% 1,3,6-hexanetrionitrile, 1 wt% tris(trimethylsilane)phosphate, and 1 wt% 1,3-propanesulfonate lactone as synergistic additives. The mixture was heated and stirred at 40°C for 12 hours to obtain a clear, transparent liquid, which was then allowed to stand before use as an electrolyte.
[0031] The battery assembly uses the electrolyte described above, and the electrode fabrication process is the same as the battery assembly process. The assembled battery was then subjected to a constant current charge-discharge test at 25°C using a LAND battery tester, with the first charge-discharge current density being 20 mAg. -1 The cutoff voltage is 2.5-4.3V, and the cyclic charge / discharge current density after the second cycle is 200mA g. -1 The cutoff voltage is 2.5-4.3V. The first-cycle coulombic efficiency is 83%, and the capacity retention after 650 cycles is 95.4%.
[0032] Example 3
[0033] At room temperature, in an argon glove box, 1 mol L of lithium salt was... -1 LiPF6 was added to a solvent with an EC:DMC:DEC volume ratio of 1:1:1, along with 2 wt% fluoroethylene carbonate, 1 wt% 1,3,6-hexanetrionitrile, 1 wt% tris(trimethylsilane)borate, and 1 wt% methanedisulfonate. The mixture was heated and stirred at 40°C for 12 hours to obtain a clear and transparent liquid, which was then allowed to stand before use as an electrolyte.
[0034] The battery assembly uses the electrolyte described above, and the electrode fabrication process is the same as the battery assembly process. The assembled battery was then subjected to a constant current charge-discharge test at 25°C using a LAND battery tester, with the first charge-discharge current density being 20 mAg. -1 The cutoff voltage is 2.5-4.3V, and the cyclic charge / discharge current density after the second cycle is 200mA g. -1 The cutoff voltage is 2.5-4.3V. The first-cycle coulombic efficiency is 85.4%, and the capacity retention after 650 cycles is 99.3%. Figure 1 .
[0035] Example 4
[0036] At room temperature, in an argon glove box, 1 mol L of lithium salt was... -1 LiPF6 was added to a solvent with an EC:DMC:DEC volume ratio of 1:1:1, along with 1 wt% fluoroethylene carbonate, 1 wt% 1,3,6-hexanetrionitrile, 1 wt% tris(trimethylsilane)borate, and 1 wt% methanedisulfonate as synergistic additives. The mixture was heated and stirred at 40°C for 12 hours to obtain a clear and transparent liquid, which was then allowed to stand before use as an electrolyte.
[0037] The battery assembly uses the electrolyte described above, and the electrode fabrication process is the same as the battery assembly process. The assembled battery was then subjected to a constant current charge-discharge test at 25°C using a LAND battery tester, with the first charge-discharge current density being 20 mAg. -1 The cutoff voltage is 2.5-4.3V, and the cyclic charge / discharge current density after the second cycle is 200mA g. -1 The cutoff voltage is 2.5-4.3V. The first-cycle coulombic efficiency is 80.9%, and the capacity retention after 650 cycles is 83.5%.
[0038] Example 5
[0039] At room temperature, in an argon glove box, 1 mol L of lithium salt was... -1 LiPF6 was added to a solvent with an EC:DMC:DEC volume ratio of 1:1:1, along with 2 wt% methyltrifluoroethyl carbonate, 1 wt% 1,3,6-hexanetrionitrile, 1 wt% tris(trimethylsilane)borate, and 1 wt% 1,3-propanesulfonate lactone as synergistic additives. The mixture was heated and stirred at 40°C for 12 hours to obtain a clear, transparent liquid, which was then allowed to stand before use as an electrolyte.
[0040] The battery assembly uses the electrolyte described above, and the electrode fabrication process is the same as the battery assembly process. The assembled battery was then subjected to a constant current charge-discharge test at 25°C using a LAND battery tester, with the first charge-discharge current density being 20 mAg. -1 The cutoff voltage is 2.5-4.3V, and the cyclic charge / discharge current density after the second cycle is 200mA g. -1The cutoff voltage is 2.5-4.3V. The first-cycle coulombic efficiency is 83.6%, and the capacity retention after 650 cycles is 86.6%.
[0041] Example 6
[0042] At room temperature, in an argon glove box, 1 mol L of lithium salt was... -1 LiPF6 was added to a solvent with an EC:DMC:DEC volume ratio of 1:1:1, along with 2 wt% methyltrifluoroethyl carbonate, 1 wt% 1,3,6-hexanetrionitrile, 1 wt% tris(trimethylsilane)phosphate, and 1 wt% 1,3-propanesulfonate lactone as synergistic additives. The mixture was heated and stirred at 40°C for 12 hours to obtain a clear, transparent liquid, which was then allowed to stand before use as an electrolyte.
[0043] The battery assembly uses the electrolyte described above, and the electrode fabrication process is the same as the battery assembly process. The assembled battery was then subjected to a constant current charge-discharge test at 25°C using a LAND battery tester, with the first charge-discharge current density being 20 mAg. -1 The cutoff voltage is 2.5-4.3V, and the cyclic charge / discharge current density after the second cycle is 200mA g. -1 The cutoff voltage is 2.5-4.3V. The first-cycle coulombic efficiency is 80.2%, and the capacity retention after 650 cycles is 92.1%.
[0044] Example 7
[0045] At room temperature, in an argon glove box, 1 mol L of lithium salt was... -1 LiPF6 was added to a solvent with an EC:DMC:DEC volume ratio of 1:1:2, along with 2 wt% fluoroethylene carbonate, 1 wt% 1,3,6-hexanetrionitrile, 1 wt% tris(trimethylsilane)phosphate, and 1 wt% 1,3-propanesulfonate lactone as synergistic additives. The mixture was heated and stirred at 40°C for 12 hours to obtain a clear, transparent liquid, which was then allowed to stand before use as an electrolyte.
[0046] The battery assembly uses the electrolyte described above, and the electrode fabrication process is the same as the battery assembly process. The assembled battery was then subjected to a constant current charge-discharge test at 25°C using a LAND battery tester, with the first charge-discharge current density being 20 mAg. -1 The cutoff voltage is 2.5-4.3V, and the cyclic charge / discharge current density after the second cycle is 200mA g. -1 The cutoff voltage is 2.5-4.3V. The first-cycle coulombic efficiency is 83.8%, and the capacity retention after 800 cycles is 94.3%.
Claims
1. A lithium-rich manganese-based lithium-ion battery long-cycle electrolyte, characterized in that, The electrolyte comprises an organic solvent, a lithium salt, and additives; wherein the additives include one or more of nitrile compounds, silane compounds, fluorinated carbonate compounds, and sulfonate compounds, and each additive accounts for 0 to 5 wt% of the total mass of the electrolyte and none of them are 0.
2. The lithium-rich manganese-based lithium-ion battery long-cycle electrolyte according to claim 1, characterized in that, The nitrile compounds are one or more selected from SUN, ADN, HTCN, EGBE, and 1,2,3-tris(2-cyanoxy)propane; the silane compounds are one or more selected from TMSB, TMSP, and TMSPi; and the fluorinated carbonate compounds are fluoroethylene carbonate, fluoropropylene carbonate, and monofluorocarbon. The additive comprises one or more of dimethyl carbonate, methyl trifluoroethyl carbonate, 2,2-difluoroethyl methyl carbonate, and trifluoroethyl ethyl carbonate; the sulfonate compound comprises one or more of 1,3-propanesulfonate lactone, methanedisulfonate methylene ester, propenyl-1,3-sulfonate lactone, and trimethylsilyl methanesulfonate; wherein the concentration of the nitrile compound is 0-5 wt%, the concentration of the silane compound is 0-5 wt%, the concentration of the fluorinated carbonate compound is 0-5 wt%, and the concentration of the sulfonate compound is 0-5 wt%, and none of the above substances is 0.
3. A lithium-rich manganese-based lithium-ion battery long-cycle electrolyte according to claim 1 or 2, characterized in that, Each additive is 0.5-3 wt%.
4. A lithium-rich manganese-based lithium-ion battery long-cycle electrolyte according to claim 1, characterized in that, The organic solvent is one or more of ethylene carbonate, dimethyl carbonate, diethyl carbonate, methyl ethyl carbonate, sulfolane, dipropyl sulfone, dimethyl sulfoxide, and propylene carbonate mixed in different proportions, preferably a mixture of ethylene carbonate, dimethyl carbonate, and diethyl carbonate.
5. A lithium-rich manganese-based lithium-ion battery long-cycle electrolyte according to claim 1, characterized in that, The lithium salt is one or more selected from lithium hexafluorophosphate, lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethanesulfonyl)imide, lithium tetrafluoroborate, lithium dioxalate borate, lithium difluorooxalate borate, and lithium difluorophosphate, preferably lithium hexafluorophosphate; the lithium salt concentration is 0.1–5 mol / L. -1 1 mol L -1 .
6. A method for preparing a lithium-rich manganese-based lithium-ion battery long-cycle electrolyte according to any one of claims 1-5, characterized in that, At room temperature, in an argon-protected glove box (oxygen and water content <0.1ppm), the lithium salt, the organic solvent, and the additive are mixed and stirred for 12 hours to completely dissolve them, resulting in a clear and transparent solution.
7. The application of the lithium-rich manganese-based lithium-ion battery long-cycle electrolyte according to any one of claims 1-5, for use in the field of lithium-rich cathode lithium-ion batteries.
8. The application according to claim 7, used for matching lithium-rich layered oxide cathode active materials.
9. A lithium-ion battery, comprising a positive electrode, a negative electrode, and a lithium-rich manganese-based lithium-ion battery long-cycle electrolyte as described in any one of claims 1-5.
10. A lithium-ion battery according to claim 9, characterized in that, The positive electrode active material of lithium-ion batteries is a lithium-rich manganese-based layered oxide positive electrode material. The preparation of the positive electrode includes the following steps: 70-99% by mass of the positive electrode active material and 0.5-29% by mass of the conductive agent acetylene black are ground and mixed; 0.5-29% by mass of polyvinylidene fluoride (PVDF) binder is added and mixed; the viscosity is adjusted using 1-methyl-2-pyrrolidone (NMP), which is not included in the mass percentage composition of the positive electrode material; the positive electrode material is coated onto the surface of aluminum foil and dried to obtain the positive electrode. The negative electrode active material for lithium-ion batteries is one or more of the following: lithium metal, lithium metal alloy, natural graphite, artificial graphite, mesophase carbon microspheres, hard carbon, and soft carbon materials; lithium metal and lithium metal alloy can be directly used as the corresponding negative electrode; the preparation of the negative electrode includes the following steps: grinding and mixing 10-100% by mass of the negative electrode active material and 0-80% by mass of the conductive agent acetylene black, adding 0-80% by mass of polyvinylidene fluoride (PVDF) binder and mixing, adjusting the viscosity with 1-methyl-2-pyrrolidone (NMP), which is not included in the mass percentage composition of the negative electrode material; coating it on the surface of copper foil and drying it to obtain the negative electrode.