Quick-charging electrolyte and application thereof
By using an electrolyte containing phosphate esters and borate esters as additives in lithium-rich manganese-based lithium-ion batteries, the problem of electrolyte decomposition under high voltage was solved, improving the battery's initial coulombic efficiency and fast charging capability, and enhancing the battery's stability and capacity.
Patent Information
- Application Number
- CN202411803786.0
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-12-09
- Publication Date
- 2026-06-09
AI Technical Summary
Lithium-rich manganese-based lithium-ion batteries suffer from problems such as large initial irreversible capacity, poor cycle stability, poor rate capability, severe voltage decay, and decomposition of traditional carbonate-based electrolytes under high voltage. In particular, electrolyte decomposition is aggravated when the charging cut-off voltage is higher than 4.8V.
A fast-charging electrolyte is used, comprising lithium hexafluorophosphate, organic solvents and additives. By introducing phosphate esters and borate esters into the electrolyte, the active oxygen species on the lithium-rich cathode surface are stabilized, forming a uniform electrode/electrolyte interface, enhancing lithium-ion transport and suppressing interfacial reactions.
It improves the initial coulombic efficiency and fast-charging performance of lithium-rich manganese-based lithium-ion batteries, reduces interface impedance, and enhances battery stability and reversible specific capacity under high voltage.
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Figure CN122177931A_ABST
Abstract
Description
Technical Field
[0001] This application relates to a fast-charging electrolyte and its application, belonging to the field of lithium batteries. Background Technology
[0002] Lithium-ion batteries have led the electric vehicle energy storage system market due to their superior performance, particularly their high gravimetric / volume energy density and long lifespan. While current electric vehicles offer a range exceeding 300 kilometers based on battery capacity, largely meeting daily urban needs, many key parameters such as range, cost, lifespan, charging speed, and safety still lag behind consumer expectations. To meet the standards of next-generation power batteries, various advanced cathodes, anodes, and electrolytes have been proposed and attracted significant attention. Lithium-rich oxides (LLOs) have long been considered the next-generation cathode for lithium-ion batteries because they offer the best rechargeable capacity to date (over 250 mAh g⁻¹) and average discharge potential (>3.5V vs. Li / Li⁺). This high capacity is accumulated through the cation and anion redox reactions of LLOs, while the high manganese content ensures good safety and low cost. Therefore, LLOs are considered a potential cathode that can bridge the energy density gap between traditional layered oxide-based lithium batteries and future lithium-sulfur (Li-S) and lithium-air (Li-O₂) batteries. However, the practical application of lithium-rich manganese-based batteries still faces obstacles such as large initial irreversible capacity, poor cycle stability, poor rate capability, and severe voltage decay during cycling. Furthermore, under conditions where the charging cutoff voltage exceeds 4.8V, traditional carbonate-based electrolytes undergo severe decomposition on the surface of lithium-ion batteries (LLOs). Anion-triggered redox reactive oxygen species can launch nucleophilic attacks on the electrolyte, further exacerbating electrolyte decomposition and interfacial structure deterioration. Therefore, it is urgent to develop and design electrolytes suitable for the surface morphology of LLO cathodes, stabilize the surface lattice structure, enhance initial capacity utilization, and improve the stability of lithium-rich manganese-based lithium-ion batteries. Summary of the Invention
[0003] The purpose of this invention is to provide a fast-charging electrolyte that improves the initial coulombic efficiency of lithium-rich manganese-based electrodes. By stabilizing the active oxygen on the surface of the lithium-rich cathode through electrolyte components, and further forming a uniform, dense electrode / electrolyte interface with fast lithium-ion transport on the electrode surface, this invention can effectively enhance the redox reversibility of lithium-rich cathode anions, reduce interface impedance, and improve the reversible specific capacity and fast-charging capability of high-voltage lithium-rich manganese-based electrodes.
[0004] According to one aspect of this application, a fast-charging electrolyte is provided, comprising an electrolyte, an organic solvent, and additives;
[0005] The electrolyte is selected from at least one of lithium hexafluorophosphate, lithium bis(oxalato)borate, lithium tetrafluoroborate, lithium bis(fluorosulfonyl)imide, and lithium bis(trifluoromethanesulfonyl)imide.
[0006] The organic solvent is selected from at least one of linear organic solvents and cyclic organic solvents;
[0007] The additive is selected from at least one of phosphate esters, sulfonates, and borates.
[0008] The concentration of the electrolyte in the fast-charging electrolyte solution is 0.8–1.5 mol / L;
[0009] The additive has a mass content of 0.5–10 wt%.
[0010] The volume ratio of the linear organic solvent to the cyclic organic solvent is 1 to 5:1;
[0011] The linear organic solvent is selected from at least one of methyl ethyl carbonate, methyl propyl carbonate, dimethyl carbonate, diethyl carbonate, methyl acetate, ethyl acetate, methyl propionate, ethyl propionate, and propyl propionate.
[0012] The cyclic organic solvent is selected from at least one of ethylene carbonate, propylene carbonate, butene carbonate, glycerol carbonate, vinylene carbonate, propylene carbonate, fluoroethylene carbonate, difluoroethylene carbonate, trifluoroethylene carbonate, trifluoropropylene carbonate, and phenyl acetate.
[0013] The phosphate ester compound is selected from at least one of trimethyl phosphate, triethyl phosphate, dimethyl phosphate, tris(hexafluoroisopropyl) phosphate, tris(2,2,2-trifluoroethyl) phosphite, tris(2,2,2-trifluoroethyl) phosphate, and tris(vinyldimethylsilane) phosphate.
[0014] The sulfonate compound is selected from at least one of methyl benzenesulfonate, n-butyl methanesulfonate, 1,3-propenesulfonate lactone, methylene disulfonate, methyl benzenesulfonate, propargyl 2-fluorobenzenesulfonate, and 3-fluoro-1,3-propanesulfonate lactone.
[0015] The borate esters are selected from at least one of tetramethylborate, trimethyl borate, tributyl borate, tri(2-cyanoethyl)borate, tri(2,2,2-trifluoroethyl) borate, and tri(hexafluoroisopropyl)borate.
[0016] According to another aspect of this application, a fast-charging lithium-ion battery is provided, comprising a positive electrode, a negative electrode, a separator, and the fast-charging electrolyte described above.
[0017] According to another aspect of this application, a lithium-rich manganese-based battery is provided, comprising a positive electrode, a negative electrode, a separator, and the aforementioned fast-charging electrolyte.
[0018] The cathode is a lithium-rich manganese-based cathode material.
[0019] The diaphragm is a polypropylene film.
[0020] The negative electrode is at least one of lithium metal, artificial graphite, natural graphite, and hard carbon negative electrode.
[0021] Injecting electrolyte into lithium-rich manganese-based batteries can significantly improve the initial coulombic efficiency and fast-charging performance of the batteries at a high voltage of ≥4.8V.
[0022] The beneficial effects that this application can produce include:
[0023] This invention introduces additives into the electrolyte and utilizes the reaction between the additives and active oxygen species on the surface of the lithium-rich cathode to stabilize the surface lattice oxygen, effectively suppressing irreversible oxygen loss during anion redox processes, and improving the coulombic efficiency in the first cycle and subsequent cycles.
[0024] During the charging process, the electrolyte additive can further decompose on the positive electrode surface and participate in the construction of an inorganic-rich positive electrode-electrolyte interface film (CEI), thereby effectively isolating the positive electrode and the electrolyte and inhibiting the occurrence of interfacial side reactions.
[0025] The additives and solvent components in the electrolyte also have a good synergistic passivation effect on the negative electrode, which can effectively suppress the growth of lithium dendrites, especially under fast charging conditions, ensuring the battery's excellent high-voltage fast charging performance.
[0026] The lithium-ion battery electrolyte provided by this invention is simple, efficient, and highly operable to prepare. Attached Figure Description
[0027] Figure 1 The LSV curves are for the electrolytes of Examples 1, 2, 3 and the control example of the present invention. Detailed Implementation
[0028] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below, but this does not constitute any limitation on this application. Reagents or instruments used, unless otherwise specified, are all conventional products that can be purchased commercially. The present invention covers all alternatives, improvements, and equivalents that may be included within the scope of the claims.
[0029] The features and performance of the present invention will be further described in detail below with reference to embodiments.
[0030] I. Electrolyte Preparation
[0031] Example 1
[0032] Preparation of electrolyte: In an argon-protected glove box (H2O≤0.1, O2≤0.1), organic solvents ethyl methyl carbonate (EMC) and fluoroethylene carbonate (FEC) were mixed in a volume ratio of 7:3 and stirred until homogeneous. Then, lithium electrolyte salt lithium hexafluorophosphate (LiPF6, concentration 1.1 mol / L) was slowly added to the mixed solution and stirred until completely dissolved. Finally, 1 wt% of tris(2,2,2-trifluoroethyl) phosphite additive was added to obtain the electrolyte of this embodiment.
[0033] Example 2
[0034] Preparation of electrolyte: In an argon-protected glove box (H2O≤0.1, O2≤0.1), organic solvents methyl ethyl carbonate and fluoroethylene carbonate were mixed in a volume ratio of 7:3 and stirred until homogeneous. Then, lithium electrolyte salt lithium hexafluorophosphate LiPF6 (concentration 1.1mol / L) was slowly added to the mixed solution and stirred until completely dissolved. Finally, 1wt% of tris(2,2,2-trifluoroethyl) phosphate additive was added to obtain the electrolyte of this embodiment.
[0035] Example 3
[0036] Preparation of electrolyte: In an argon-protected glove box (H2O≤0.1, O2≤0.1), organic solvents methyl ethyl carbonate and fluoroethylene carbonate were mixed in a volume ratio of 7:3 and stirred until homogeneous. Then, lithium electrolyte salt lithium hexafluorophosphate LiPF6 (concentration 1.1mol / L) was slowly added to the mixed solution and stirred until completely dissolved. Finally, 1wt% of tris(2,2,2-trifluoroethyl) borate additive was added to obtain the electrolyte of this embodiment.
[0037] Example 4
[0038] Preparation of electrolyte: In an argon-protected glove box (H2O≤0.1, O2≤0.1), organic solvents methyl ethyl carbonate and difluoroethylene carbonate were mixed in a volume ratio of 7:3 and stirred until homogeneous. Then, lithium electrolyte salt lithium hexafluorophosphate LiPF6 (concentration 1.1mol / L) was slowly added to the mixed solution and stirred until completely dissolved. Finally, 1wt% of tris(2,2,2-trifluoroethyl) phosphite additive was added to obtain the electrolyte of this embodiment.
[0039] Example 5
[0040] Preparation of electrolyte: In an argon-protected glove box (H2O≤0.1, O2≤0.1), organic solvents methyl ethyl carbonate and difluoroethylene carbonate were mixed in a volume ratio of 7:3 and stirred until homogeneous. Then, lithium electrolyte salt lithium hexafluorophosphate LiPF6 (concentration 1.1mol / L) was slowly added to the mixed solution and stirred until completely dissolved. Finally, 1wt% of tris(2,2,2-trifluoroethyl) phosphate additive was added to obtain the electrolyte of this embodiment.
[0041] Example 6
[0042] Preparation of electrolyte: In an argon-protected glove box (H2O≤0.1, O2≤0.1), organic solvents methyl ethyl carbonate and difluoroethylene carbonate were mixed in a volume ratio of 7:3 and stirred until homogeneous. Then, lithium electrolyte salt lithium hexafluorophosphate LiPF6 (concentration 1.1 mol / L) was slowly added to the mixed solution and stirred until completely dissolved. Then, 1 wt% of tris(2,2,2-trifluoroethyl) phosphate additive and 1 wt% of tris(2,2,2-trifluoroethyl) phosphite additive were added to obtain the electrolyte of this embodiment.
[0043] Example 7
[0044] Preparation of electrolyte: In an argon-protected glove box (H2O≤0.1, O2≤0.1), organic solvents methyl ethyl carbonate and vinylene carbonate were mixed in a volume ratio of 7:3 and stirred until homogeneous. Then, lithium electrolyte salt lithium hexafluorophosphate LiPF6 (concentration 1.1mol / L) was slowly added to the mixed solution and stirred until completely dissolved. Finally, 1wt% of tris(2,2,2-trifluoroethyl) phosphite additive was added to obtain the electrolyte of this embodiment.
[0045] Comparative Example 1
[0046] Preparation of electrolyte: In an argon-protected glove box (H2O≤0.1, O2≤0.1), organic solvents ethyl methyl carbonate (EMC) and fluoroethylene carbonate (FEC) were mixed in a volume ratio of 7:3 and stirred until homogeneous. Then, lithium electrolyte salt lithium hexafluorophosphate (LiPF6, concentration 1.1 mol / L) was slowly added to the mixed solution and stirred until completely dissolved to obtain the electrolyte of this control example.
[0047] II. Electrochemical Performance Testing
[0048] The lithium-ion batteries prepared with the electrolytes of Examples 1-7 and Comparative Example 1 were subjected to the following related experiments:
[0049] Electrolyte high-voltage oxidation stability, i.e., linear voltammetric scan (LSV) test: at 25℃, the scan rate is 0.2mV / s, and the voltage test range is 2-5V.
[0050] First-round coulomb efficiency test: At 25℃, charge and discharge tests were conducted at 0.2C, with a voltage range of 2-4.8V.
[0051] Room temperature fast charging performance test: At 25℃, after 3 cycles of 0.2C activation, the voltage range of charging and discharging is 2-4.8V using 3C rate cycling.
[0052] The results of the above electrochemical performance tests are shown in Table 1.
[0053] Table 1. Comparison of electrochemical performance of electrolytes in Examples 1-7 and control examples
[0054]
[0055] Depend on Figure 1 The LSV results show that adding phosphate esters and borate esters to the electrolyte can increase the oxidation potential of the electrolyte, indicating that the electrolyte has better oxidation stability.
[0056] As can be seen from the test results of Examples 1, 3, 5 and the control examples in Table 1, adding phosphate ester additives to the electrolyte can effectively improve the initial coulombic efficiency and first-cycle discharge specific capacity of lithium-rich manganese-based cathodes. This is because phosphate ester additives can act as electrophilic species, undergoing nucleophilic reactions with active oxygen species on the surface of the lithium-rich manganese-based cathode, thereby inhibiting irreversible loss of surface oxygen and improving the first-cycle capacity utilization.
[0057] As can be seen from the test results of Examples 3 and 7 and the control examples in Table 1, adding borate ester additives to the electrolyte can effectively enhance the 3C fast charging performance of lithium-rich manganese-based electrolytes and improve the first coulombic efficiency to a certain extent. This is because the electron-deficient B centers in the borate esters can effectively capture the oxygen intermediates generated during the oxidation process of lithium-rich cathode anions, thereby inhibiting further oxidation of oxygen to oxygen gas and its escape. Furthermore, it can act as a film-forming additive to participate in the construction of the interfacial film, forming a B-rich inorganic CEI layer, improving interfacial stability and accelerating ion transport.
[0058] As can be seen from the test results of Examples 3, 5, and 6 and the control examples in Table 1, the simultaneous addition of phosphate ester and borate ester additives to the electrolyte can significantly improve the initial coulombic efficiency and fast-charging performance. This is attributed to the synergistic stabilization of surface lattice oxygen and interface structure by the two types of additives. Simultaneously, the electrolyte solvent and additives also effectively inhibit the growth of lithium dendrites in the negative electrode, ensuring excellent fast-charging performance.
[0059] In summary, the electrolyte provided by this invention effectively improves the initial coulombic efficiency and high-voltage fast-charging performance of lithium-rich manganese-based lithium-ion batteries by optimizing electrolyte composition and additives and utilizing the synergistic effect between multiple components.
[0060] The above description is merely a few embodiments of this application and is not intended to limit this application in any way. Although this application discloses preferred embodiments as described above, it is not intended to limit this application. Any changes or modifications made by those skilled in the art without departing from the scope of the technical solution of this application using the disclosed technical content are equivalent to equivalent implementation cases and fall within the scope of the technical solution.
Claims
1. A fast-charging electrolyte, characterized in that, It consists of electrolytes, organic solvents, and additives; The electrolyte is selected from at least one of lithium hexafluorophosphate, lithium bis(oxalato)borate, lithium tetrafluoroborate, lithium bis(fluorosulfonyl)imide, and lithium bis(trifluoromethanesulfonyl)imide. The organic solvent is selected from at least one of linear organic solvents and cyclic organic solvents; The additive is selected from at least one of phosphate esters, sulfonates, and borates. The concentration of the electrolyte in the fast-charging electrolyte solution is 0.8–1.5 mol / L; The additive has a mass content of 0.5–10 wt%.
2. The fast-charging electrolyte according to claim 1, characterized in that, The volume ratio of the linear organic solvent to the cyclic organic solvent is 1 to 5:1; The linear organic solvent is selected from at least one of methyl ethyl carbonate, methyl propyl carbonate, dimethyl carbonate, diethyl carbonate, methyl acetate, ethyl acetate, methyl propionate, ethyl propionate, and propyl propionate. The cyclic organic solvent is selected from at least one of ethylene carbonate, propylene carbonate, butene carbonate, glycerol carbonate, vinylene carbonate, propylene carbonate, fluoroethylene carbonate, difluoroethylene carbonate, trifluoroethylene carbonate, trifluoropropylene carbonate, and phenyl acetate.
3. The fast-charging electrolyte according to claim 1, characterized in that, The phosphate ester compound is selected from at least one of trimethyl phosphate, triethyl phosphate, dimethyl phosphate, tris(hexafluoroisopropyl) phosphate, tris(2,2,2-trifluoroethyl) phosphite, tris(2,2,2-trifluoroethyl) phosphate, and tris(vinyldimethylsilane) phosphate. The sulfonate compound is selected from at least one of methyl benzenesulfonate, n-butyl methanesulfonate, 1,3-propenesulfonate lactone, methylene disulfonate, methyl benzenesulfonate, propargyl 2-fluorobenzenesulfonate, and 3-fluoro-1,3-propanesulfonate lactone. The borate esters are selected from at least one of tetramethylborate, trimethyl borate, tributyl borate, tri(2-cyanoethyl)borate, tri(2,2,2-trifluoroethyl) borate, and tri(hexafluoroisopropyl)borate.
4. A fast-charging lithium-ion battery, characterized in that, Includes the fast-charging electrolyte as described in any one of claims 1 to 3.
5. A lithium-rich manganese-based battery, characterized in that, Includes the fast-charging electrolyte as described in any one of claims 1 to 3.