Lithium ion battery
By using a specific ratio of tris(trimethylsilane)phosphate and mannitol carbonate sulfate additives in lithium-ion batteries, a stable passivation layer is generated, which solves the problem of surface moisture in silicon-carbon materials, improves the initial efficiency and high-temperature storage performance of the battery, and extends the battery life.
Patent Information
- Application Number
- CN202511990886.3
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-12-26
- Publication Date
- 2026-02-17
AI Technical Summary
In existing lithium-ion batteries, it is difficult to remove moisture from the surface of silicon-carbon materials, which leads to unstable SEI, high consumption of active lithium during the first charge, severe self-discharge, accelerated degradation of active materials under high-temperature storage, and deterioration of cycle performance.
Tris(trimethylsilane)phosphate (TMSP) and mannitol sulfate (BDD) are used as additives, and a stable passivation layer is generated through a specific electrolyte composition to protect the battery cell, reduce self-discharge, and improve cycle performance.
It improves the initial coulombic efficiency of lithium-ion batteries, reduces self-discharge during high-temperature storage, and ensures long-cycle performance.
Smart Images
Figure BDA0005763070440000031
Abstract
Description
Technical Field
[0001] This invention belongs to the field of battery technology, specifically relating to a lithium-ion battery. Background Technology
[0002] Silicon-carbon materials are considered a next-generation anode material for lithium-ion batteries due to their good structural stability and high theoretical specific capacity, and are now often combined with graphite materials to form anode sheets. However, due to their extremely large specific surface area and residual silanol groups on the surface, silicon-carbon materials readily adsorb water, which is difficult to remove by baking. The residual water adsorbed on the material surface reacts with the passivation layer components at the interface, causing the cell to consume more active lithium during the first charge, and the resulting passivation layer (SEI) is unstable. The instability of the SEI formed during the first charge leads to voltage drop due to cell self-discharge, which degrades the cell's capacity. On the other hand, under high-temperature storage environments, the instability of the cell's SEI also causes the active materials to continuously react with the electrolyte, accelerating the degradation of the cell's active materials and electrolyte decomposition, resulting in increased cell polarization and capacity loss.
[0003] Currently, besides strengthening environmental control, some studies report that adding dehydrating and deacidifying additives to the electrolyte can increase the tolerance margin in the manufacturing process, such as acid anhydrides, isocyanates, or phosphate esters. However, while these additives can improve these problems, they also generate a high-resistance SEI while solving the moisture problem, and may even embed into the negative electrode, causing graphite negative electrode delamination and deteriorating the long-cycle performance of the cell. Therefore, there is an urgent need to improve existing technologies. Summary of the Invention
[0004] The technical problem to be solved by the present invention is to provide a lithium-ion battery with high initial efficiency, low self-discharge at high temperature storage, and long cycle performance.
[0005] The technical solution adopted by the present invention to solve the above problems is as follows:
[0006] A lithium-ion battery includes a positive electrode, a negative electrode, and an electrolyte, wherein the electrolyte comprises a first additive tris(trimethylsilane) phosphate (TMSP) and a second additive mannitol sulfate carbonate (BDD); the lithium-ion battery satisfies the following relationship:
[0007] 0.03≤P*(B-1.4%)*10000*(I / 1.3)≤1.5, and 0<P<1.2%, 0<B<4%, 1.1<I<1.6;
[0008] Where P is the mass percentage of the first additive in the electrolyte, B is the mass percentage of the second additive in the electrolyte, and I is the electrolyte filling coefficient of the battery, in g / Ah.
[0009] In the above technical solution, the first additive in the electrolyte can react with the moisture on the surface of the negative electrode silicon-carbon material inside the cell to protect the interface passivation layer generated during the cell cycling process, thereby improving the cell's initial coulombic efficiency and reducing self-discharge during high-temperature storage; wherein, the second additive in the electrolyte can preferentially generate a stable passivation layer on both the positive and negative electrodes simultaneously, preventing the first additive from being co-intercalated with the graphite negative electrode, thereby deteriorating the cell's cycling performance.
[0010] The lithium-ion battery of the present invention, through the setting of the first additive and the second additive, and the setting of the relationship: 0.03≤P*(B-1.4%)*10000*(I / 1.3)≤1.5, and 0<P<1.2%, 0<B<4%, 1.1<I<1.6, the first additive and the second additive synergistically improve the initial coulombic efficiency of the battery and reduce the self-discharge of the battery during high-temperature storage, and ensure the long-cycle performance of the battery.
[0011] Furthermore, the electrolyte also includes lithium salt and organic solvent; based on the total mass of the electrolyte (100%), the mass percentage of lithium salt does not exceed 18%, and the mass percentage of organic solvent is not less than 65%.
[0012] Further, the lithium salt is one or more selected from lithium hexafluorophosphate, lithium difluorophosphate, lithium difluorooxalate borate, lithium dioxalate borate, lithium difluorosulfonyl imide, lithium ditrifluoromethyl imide, lithium difluorodioxalate phosphate, and lithium nitrate.
[0013] Further, the organic solvent is two or more of the following: ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, methyl ethyl carbonate, methyl formate, ethyl propionate, propyl propionate, methyl butyrate, ethyl butyrate, and ethyl difluoroacetate.
[0014] Furthermore, the electrolyte also includes a third additive, fluoroethylene carbonate; based on the total mass of the electrolyte (100%), the mass percentage of the third additive is not less than 10%.
[0015] Furthermore, the electrolyte also includes a fourth additive, which comprises one or more of adiponitrile, butadionitrile, 1,3,6-hexanetricarbonyl, trans-hexenedionitrile, trans-butenedionitrile, 1,2-di(cyanoethoxy)ethane, and 1,2,3-tri(cyanoethoxy)propane; the mass percentage of the fourth additive is 2%-4% based on the total mass of the electrolyte being 100%.
[0016] Furthermore, the negative electrode includes an active material layer containing not less than 5 wt% silicon-carbon.
[0017] The present invention has the following beneficial effects:
[0018] The lithium-ion battery of the present invention, through the setting of the first additive and the second additive, and the setting of the relationship: 0.03≤P*(B-1.4%)*10000*(I / 1.3)≤1.5, and 0<P<1.2%, 0<B<4%, 1.1<I<1.6, the first additive and the second additive synergistically improve the initial coulombic efficiency of the battery and reduce the self-discharge of the battery during high-temperature storage, and ensure the long-cycle performance of the battery. Detailed Implementation
[0019] To make the technical problems, solutions, and advantages of this invention clearer, a detailed description will be provided below with reference to specific examples. However, the scope of protection of this invention is not limited to the following specific embodiments. The described embodiments are merely some, not all, of the embodiments of this invention, and are not intended to limit the invention. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this invention.
[0020] Unless otherwise defined, all technical terms used herein have the same meaning as commonly understood by those skilled in the art. The technical terms used herein are for the purpose of describing particular embodiments only and are not intended to limit the scope of the invention.
[0021] Unless otherwise specified, all raw materials, reagents, instruments and equipment used in this invention can be purchased from the market or prepared by existing methods.
[0022] This invention is designed for lithium-ion batteries, and includes Examples 1-10 and Comparative Examples 1-8. Some raw materials and parameters in the formulation are shown in Table 1. All contents in the formulation are by mass percentage.
[0023] Table 1. Some raw materials, parameters, and performance test results in the examples and comparative examples.
[0024]
[0025] The preparation method of the lithium-ion battery in Example 1 specifically includes the following steps:
[0026] Preparation of the positive electrode: Lithium cobalt oxide (LiCoO2), carbon black (conductive agent), polyvinylidene fluoride (PVDF) (binder), and carbon nanotubes (CNTs) were mixed in a mass ratio of 98:0.4:1.1:0.5 to obtain a mixture. The mixture was weighed and added to N-methylpyrrolidone solvent at a mass ratio of 0.2%, and stirred thoroughly to form a uniform positive electrode slurry. The positive electrode slurry was coated onto Al foil (positive electrode current collector), dried, and then rolled to a compaction density of 4.20 g / cm³. 3, thus obtaining the positive electrode.
[0027] Preparation of the negative electrode: The negative electrode active materials graphite, silicon carbide, binder styrene-butadiene rubber, polyacrylic acid, thickener lithium carboxymethyl cellulose, and conductive agent carbon nanotubes (CNTs) were weighed in a mass ratio of 86.6:10:1.4:1.5:0.25:0.25. These were then thoroughly mixed in an appropriate amount of deionized water to form a uniform negative electrode slurry. The negative electrode slurry was coated onto the copper foil of the negative electrode current collector, dried, and rolled to a compaction density of 1.6 g / cm³. 3 This yields the negative electrode. The silicon-carbon electrode has a DV50 of 8-11 μm and a specific surface area ≤2 m². 2 / g.
[0028] The diaphragm is made of 9μm thick polyethylene (PE) membrane with an aluminum oxide coating.
[0029] Preparation of electrolyte: Lithium salt: lithium hexafluorophosphate (LiPF6) 15%; First additive: TMSP 0.3%, Second additive: BDD 1.5%, Third additive: fluoroethylene carbonate (FEC) 13%, Fourth additive: succinate (SN) 3%; Solvent equals 100% minus the mass percentage of lithium salt and all additives, with ethylene carbonate: propylene carbonate: ethyl propionate = 1:1:8; Mix the above electrolyte raw materials to obtain the electrolyte.
[0030] After welding the tabs to the positive and negative electrodes, the positive electrode, separator, and negative electrode are stacked in sequence, with the separator acting as an insulator between the positive and negative electrodes. Then, the cells are wound to obtain bare cells. The bare cells are placed in an outer packaging foil aluminum-plastic film, and the prepared electrolyte is injected into the dried bare cells. After vacuum sealing, settling, formation, capacity testing, and aging, a soft-pack lithium-ion battery is obtained.
[0031] The lithium-ion batteries of Examples 2-10 and Comparative Examples 1-8 differ from the lithium-ion battery of Example 1 only in the amount of the first additive TMSP, the second additive mannitol carbonate sulfate, and the liquid injection coefficient. The reduced portions of the first and second additives are replaced by solvents, and the preparation methods are similar.
[0032] The lithium-ion batteries of the above embodiments and comparative examples were subjected to performance tests. The test methods are as follows, and the test results are shown in Table 1.
[0033] 1. First-effect calculation:
[0034] The initial efficiency calculation is equal to the ratio of the battery's initial discharge capacity QA to the sum of the battery's formation charge capacity QB and the initial charge capacity QC, i.e., QA / (QB+QC))*100%.
[0035] 2.35℃ High-Temperature Storage Experiment:
[0036] The batteries obtained in the examples and comparative examples were placed in an environment of 25±2℃ and left to stand for 2 hours to allow the battery body to reach 25±2℃. The batteries were then charged at a constant current of 0.5C to 4.53V with a cutoff current of 0.05C. After being fully charged, the batteries were left to rest for 5 minutes, and then discharged at a constant current of 0.5C to a cutoff voltage of 3.0V. The discharge capacity was recorded as Q0. After resting for 10 minutes, the batteries were charged at a constant current of 0.5C to 4.53V with a cutoff current of 0.05C. After being fully charged, the batteries were placed in an environment of 35±2℃ for 7 days, and then placed in an environment of 25±2℃ for 2 hours. The batteries were then discharged at a constant current of 0.5C to 3V. The discharge capacity was recorded as Q1. The capacity retention rate was Q1 / Q0*100%. The higher the capacity retention rate, the less self-discharge. A retention rate of ≥95% was considered acceptable.
[0037] 3.25℃ ambient temperature cycling experiment:
[0038] The batteries obtained in the examples and comparative examples were placed in an environment of 25±2℃ and left to stand for 2 hours. When the battery body reached 25±2℃, the battery was charged at a constant current of 4C to 4.53V with a cutoff current of 0.05C. After the battery was fully charged, it was left to stand for 5 minutes, and then discharged at a constant current of 0.5C to the cutoff voltage of 3.0V. After the battery was discharged, it was left to stand for 5 minutes. This was recorded as one cycle. The discharge capacity of the third cycle was recorded as the initial capacity Q. When the cycle reached 1000 cycles, the discharge capacity Q1 of the last cycle was recorded. The capacity retention rate was Q1 / Q*100%. If the capacity retention rate after 1000 cycles was ≥80%, it was considered a pass.
[0039] According to the test results in Table 1, compared with the comparative example, the lithium-ion battery of the present invention, through the setting of the first additive and the second additive, and the setting of the relationship: 0.03≤P*(B-1.4%)*10000*(I / 1.3)≤1.5, and 0<P<1.2%, 0<B<4%, 1.1<I<1.6, the battery has good initial efficiency, low high-temperature storage self-discharge and good long cycle performance.
[0040] The preferred embodiments of the present invention have been described in detail above. However, the present invention is not limited to the specific details in the above embodiments. Within the scope of the technical concept of the present invention, various simple modifications can be made to the technical solution of the present invention, and these simple modifications all fall within the protection scope of the present invention.
[0041] It should also be noted that the various specific technical features described in the above embodiments can be combined in any suitable manner without contradiction. To avoid unnecessary repetition, the present invention will not describe the various possible combinations separately.
[0042] Furthermore, various different embodiments of the present invention can be combined in any way, as long as they do not violate the spirit of the present invention, they should also be regarded as the content disclosed by the present invention.
Claims
1. A lithium-ion battery, characterized by, The lithium ion battery comprises a positive electrode, a negative electrode and an electrolyte, the electrolyte comprises a first additive tris(trimethylsilyl) phosphate and a second additive mannitol carbonate sulfate; the lithium ion battery satisfies the following relationship: 0.03 <= P*(B-1.4%)*10000*(I / 1.3) <= 1.5, and 0 < P < 1.2%, 0 < B < 4%, 1.1 < I < 1.6; Wherein, P is the mass percentage content of the first additive in the electrolyte, B is the mass percentage content of the second additive in the electrolyte, and I is the injection coefficient of the battery, unit: g / Ah.
2. The lithium-ion battery of claim 1, wherein, The electrolyte further comprises a lithium salt and an organic solvent; the mass percentage content of the lithium salt is not more than 18% and the mass percentage content of the organic solvent is not less than 65% based on the total mass of the electrolyte.
3. The lithium-ion battery of claim 2, wherein, The lithium salt is one or more of lithium hexafluorophosphate, lithium difluorophosphate, lithium difluoro oxalate borate, lithium bisoxalate borate, lithium bisfluorosulfonylimide, lithium bis(trifluoromethyl) imide, lithium difluoro di-oxalate phosphate and lithium nitrate.
4. The lithium-ion battery of claim 2, wherein, The organic solvent is two or more of ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, methyl ethyl carbonate, methyl formate, ethyl propionate, propyl propionate, methyl butyrate, ethyl butyrate and ethyl difluoroacetate.
5. The lithium-ion battery according to any one of claims 1 to 4, characterized in that, The electrolyte further comprises a third additive fluoroethylene carbonate; the mass percentage content of the third additive is not less than 10% based on the total mass of the electrolyte.
6. The lithium-ion battery according to any one of claims 1 to 4, characterized in that, The electrolyte further comprises a fourth additive, the fourth additive comprises one or more of adiponitrile, butanedinitrile, 1,3,6-hexanetrimethyl nitrile, trans-hexenedinitrile, trans-butenedinitrile, 1,2-di(cyanoethoxy)ethane and 1,2,3-tri(cyanoethoxy)propane; the mass percentage content of the fourth additive is 2%-4% based on the total mass of the electrolyte.
7. The lithium-ion battery of claim 1, wherein, The negative electrode comprises an active material layer, the active material layer contains not less than 5wt% of silicon carbon.