A lithium-ion battery

Abstract

The application relates to the technical field of batteries, in particular to a lithium ion battery. The lithium ion battery comprises an electrolyte, and the electrolyte comprises an additive A, the additive A comprises a substance satisfying the following condition: the oxidation-reduction potential of the substance is lower than the charge cut-off voltage of the lithium ion battery. The electrolyte can activate dead lithium, thereby improving the safety of the lithium ion battery and the cycle performance of the battery.

Description

Technical Field

[0001] This application relates to the field of battery technology, specifically to a lithium-ion battery. Background Technology

[0002] Dendrite growth is present in almost all rechargeable lithium metal batteries, posing a significant obstacle to their practical application. Severe dendrite growth causes some lithium to separate from the current collector and become dead lithium, leading to safety issues and rapid battery degradation. Dead lithium is a serious byproduct that contributes to capacity decay, insufficient lifespan, and thermal runaway in lithium-ion batteries. Currently, industry and academia focus on improving lithium dendrite formation and preventing and reducing the degree of dead lithium; however, research on activating dead lithium to fundamentally eliminate it is still insufficient.

[0003] Since dead lithium leads to capacity decay, insufficient lifespan, and thermal runaway in lithium-ion batteries, reactivating dead lithium is one way to address these issues, as it can slow lithium consumption and improve interface stability. This approach focuses more on resolving existing byproducts rather than slowing down the generation rate to maintain long-term effectiveness. However, there is currently little research on how to reactivate dead lithium. Summary of the Invention

[0004] In view of this, the present invention provides a lithium-ion battery. The electrolyte of this battery, by using additives with a redox potential lower than the charging cutoff voltage, can reactivate dead lithium, thereby improving the battery capacity retention rate.

[0005] To achieve the above-mentioned objectives, the present invention provides the following technical solution:

[0006] This invention provides a lithium-ion battery, which includes a positive electrode, a separator, a negative electrode, and an electrolyte. The electrolyte includes additive A, which comprises a substance that satisfies the following conditions:

[0007] a) Its redox potential is lower than the charging cutoff voltage of lithium-ion batteries.

[0008] The experimental principle of this invention: The relationship between the redox potential of the electrode, the voltage range of the battery, and the redox potential of the medium generally determines the specific role of the redox medium in the battery. The selectable redox potential is one of the key factors promoting widespread application. Therefore, when applied to lithium metal batteries, it is feasible to regulate the reactivation of dead lithium by selecting a redox medium with a suitable redox potential. Specifically, the redox potential of the redox medium should be lower than the charging cutoff voltage to ensure that the cycling reaction reactivates the dead lithium.

[0009] Meanwhile, it is also feasible to adjust the effect of suppressing self-discharge by selecting a redox medium with a suitable redox potential. The additive should also have a higher redox potential than the cathode material to avoid cyclic reactions that lead to self-discharge.

[0010] Preferably, the positive electrode sheet comprises a positive electrode active material; additive A of the present invention comprises a substance that simultaneously satisfies the following conditions:

[0011] a) Its redox potential is lower than the charging cutoff voltage of lithium-ion batteries;

[0012] b) Its redox potential is higher than that of the positive electrode active material.

[0013] In this invention, the "redox potential" refers to the redox potential detected relative to a lithium-ion battery system.

[0014] The mechanism for eliminating dead lithium used in this invention is as follows: Additive A used in this invention can react with dead lithium, which is then oxidized to generate lithium ions (Li). + In this process, lithium ions migrate directionally in the electrolyte to the graphite anode to form a uniform lithium coating. On the other hand, additive A of this invention is reduced to corresponding free radical anions, which then lose electrons, completing a shuttle effect. Through this cyclic process, the activation and elimination of dead lithium are achieved.

[0015] Preferably, the lithium-ion battery includes at least one of lithium iron phosphate battery, lithium cobalt oxide battery, ternary nickel-cobalt-manganese battery, ternary nickel-cobalt-aluminum battery, lithium manganese oxide battery, lithium nickel oxide battery, lithium titanate battery, and nickel-cobalt-manganese-aluminum battery.

[0016] Preferably, the positive electrode active material includes at least one of transition metal oxides, lithium iron phosphate, and lithium-rich manganese-based materials. The chemical formula of the transition metal lithium oxide is Li. 1+x Ni y Co z M (1-y-z) O2, where -0.1≤x≤1; 0≤y≤1, 0≤z≤1, and 0≤y+z≤1; where M is one or more of Mg, Zn, Ga, Ba, Al, Fe, Cr, Sn, V, Mn, Sc, Ti, Nb, Mo, and Zr. For example, positive electrode active materials include lithium iron phosphate (LiFePO4, abbreviated as LFP), lithium cobalt oxide (LiCo2, abbreviated as LCO), lithium manganese oxide (LiMn2O4, abbreviated as LMO), lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminum oxide (LiNiCoAlO2, abbreviated as NCA), and lithium titanate (Li4Ti5O4). 12 (LTO for short), etc.

[0017] In the embodiments provided by the present invention, the lithium-ion battery and the positive electrode active material have a corresponding relationship. For example, the positive electrode active material corresponding to the lithium iron phosphate battery is lithium iron phosphate, the positive electrode active material corresponding to the lithium cobalt oxide battery is lithium cobalt oxide, and the positive electrode active material corresponding to the ternary nickel cobalt aluminum battery is ternary nickel cobalt aluminum.

[0018] In the embodiments provided by the present invention, the lithium-ion battery is a lithium iron phosphate battery. Preferably, additive A includes a substance with a redox potential of 3.4 to 4.0 V; more preferably, additive A includes a substance with a redox potential of 3.4 to 3.8 V.

[0019] Preferably, the lithium-ion battery is a lithium iron phosphate battery, and additive A includes a substance with a redox potential of 3.43 to 3.78 V.

[0020] Preferably, additive A has a redox potential of 3.4–4.0 V, and the substance comprises at least one of the following:

[0021] c) at least one of toluidine blue, tris(4-iodophenyl)amine, 2,4,6-triphenylpyran tetrafluoride boron salt, S-(trifluoromethyl)-dibenzothiophene tetrafluoroboronate, and trifluoromethanesulfonyl chloride; and / or

[0022] d) Derivatives of any one or more of the compounds mentioned in c) above.

[0023] In the embodiments provided by the present invention, the lithium-ion battery is a lithium cobalt oxide battery. Preferably, additive A includes a substance with a redox potential of 3.6 to 4.53 V; more preferably, additive A includes a substance with a redox potential of 3.7 to 4.4 V.

[0024] In the embodiments provided by the present invention, the lithium-ion battery is a lithium manganese oxide battery. Preferably, additive A includes a substance with a redox potential of 3.8 to 4.2 V; more preferably, additive A includes a substance with a redox potential of 3.9 to 4.0 V.

[0025] In the embodiments provided by the present invention, the lithium-ion battery is a ternary nickel-cobalt-manganese battery. Preferably, additive A includes a substance with a redox potential of 3.6 to 4.45 V; more preferably, additive A includes a substance with a redox potential of 3.7 to 4.4 V.

[0026] In the embodiments provided by this invention, the positive electrode active material in the ternary nickel-cobalt-manganese battery is lithium nickel-cobalt-manganese oxide, including but not limited to LiNi. 0.5 Mn 0.2 Co 0.3 O2(NCM523), LiNi 0.6 Mn 0.2 Co 0.2 O2(NCM622), LiNi0.8 Mn 0.1 Co 0.1 At least one of O2 (NCM811).

[0027] In the embodiments provided by the present invention, the lithium-ion battery is a ternary nickel-cobalt-manganese NCM523 battery. Preferably, additive A includes a substance with a redox potential of 3.7 to 4.45 V; more preferably, additive A includes a substance with a redox potential of 3.8 to 4.3 V.

[0028] In the embodiments provided by the present invention, the lithium-ion battery is a ternary nickel-cobalt-manganese NCM622 battery. Preferably, additive A includes a substance with a redox potential of 3.7 to 4.35 V; more preferably, additive A includes a substance with a redox potential of 3.7 to 4.2 V.

[0029] In the embodiments provided by the present invention, the lithium-ion battery is a ternary nickel-cobalt-manganese NCM811 battery. Preferably, additive A includes a substance with a redox potential of 3.7 to 4.25 V; more preferably, additive A includes a substance with a redox potential of 3.7 to 4.1 V.

[0030] In the embodiments provided by the present invention, the lithium-ion battery is a ternary nickel-cobalt-aluminum battery. Preferably, additive A includes a substance with a redox potential of 3.7 to 4.25 V; more preferably, additive A includes a substance with a redox potential of 3.7 to 4.1 V.

[0031] In the embodiments provided by the present invention, the lithium-ion battery is a lithium titanate battery. Preferably, additive A includes a substance with a redox potential of 2.4 to 2.85 V; more preferably, additive A includes a substance with a redox potential of 2.5 to 2.7 V.

[0032] In the embodiments provided by this invention, only lithium iron phosphate batteries are used as an example, and some types of additive A that meet the redox potential conditions are listed. For the aforementioned lithium cobalt oxide batteries, ternary nickel-cobalt-manganese batteries, ternary nickel-cobalt-aluminum batteries, lithium manganese oxide batteries, etc., as long as conditions a) and / or b) above are met, additive A types that meet the above conditions will not be listed here one by one. For example, tris(4-iodophenyl)amine can also be used in lithium cobalt oxide batteries, ternary nickel-cobalt-manganese batteries, ternary nickel-cobalt-aluminum batteries, etc., but the types of additive A are not limited to these.

[0033] Preferably, the concentration of additive A in the electrolyte is 0.01–0.5 mol / L.

[0034] Preferably, the concentration of additive A in the electrolyte is 0.005–0.3 mol / L.

[0035] More preferably, the concentration of additive A in the electrolyte is 0.005 to 0.05 mol / L.

[0036] More preferably, the concentration of additive A in the electrolyte is 0.005 to 0.04 mol / L.

[0037] In this invention, the electrolyte also includes an organic solvent and a lithium salt.

[0038] Preferably, the organic solvent includes carbonates and / or carboxylic esters.

[0039] Preferably, the carbonate is selected from at least one of the following solvents or their fluorinated derivatives: ethylene carbonate (EC), propylene carbonate (PC), dimethyl carbonate, diethyl carbonate (DEC), and methyl ethyl carbonate.

[0040] In specific embodiments provided by the present invention, the fluorinated derivatives of ethylene carbonate include fluoroethylene carbonate (FEC).

[0041] Preferably, the carboxylic acid ester is selected from at least one of the following solvents or their fluorinated derivatives: propyl acetate, n-butyl acetate, isobutyl acetate, n-amyl acetate, isoamyl acetate, propyl propionate (PP), ethyl propionate (EP), methyl butyrate, and ethyl n-butyrate.

[0042] In specific embodiments provided by the present invention, the electrolyte may further include additive B to improve other battery performance, such as cycle performance. Preferably, additive B includes at least one of cyclic carbonate additives, cyclic sulfonyl lactone additives, nitrile additives, and lithium salt additives.

[0043] Preferably, the cyclic carbonate additives include at least one of fluoroethylene carbonate, vinylene carbonate, and ethylene ethylene carbonate.

[0044] Preferably, the cyclic sulfonate lactone additive is selected from at least one of 1,3-propanesulfonate lactone, 1,3-propenesulfonate lactone, 2,4-butanesulfonate lactone, and 1,4-butanesulfonate lactone.

[0045] Preferably, the nitrile additive is selected from at least one of saturated polynitriles, unsaturated alkyl polynitriles, and oxyalkyl nitriles;

[0046] Preferably, the lithium salt additive is selected from at least one of lithium difluorooxalate borate, lithium difluorophosphate, lithium difluorodioxalate phosphate, and lithium dioxalate borate.

[0047] In the embodiments provided by the present invention, the proportion of each organic solvent in the electrolyte can be any proportion.

[0048] In a specific embodiment provided by the present invention, the electrolyte includes ethylene carbonate (EC), diethyl carbonate (DEC) and fluoroethylene carbonate (FEC), and the ratio of EC, DEC and FEC is (1-10):(1-10):(0.1-5).

[0049] Preferably, the lithium salt includes at least one of lithium hexafluorophosphate (LiPF6), lithium difluorophosphate (LiPO2F2), lithium difluorooxalate borate (LiDFOB), lithium bis(fluorosulfonyl)imide (LiTFSI), lithium bis(trifluoromethylsulfonyl)imide, lithium difluorobis(oxalate)phosphate, lithium tetrafluoroborate, lithium bis(oxalate)borate, lithium hexafluoroantimonyate, lithium hexafluoroarsenate, lithium di(trifluoromethylsulfonyl)imide, lithium di(pentafluoroethylsulfonyl)imide, lithium tri(trifluoromethylsulfonyl)methyl, or lithium di(trifluoromethylsulfonyl)imide.

[0050] Preferably, the concentration of lithium salt in the electrolyte is 0.1–10 mol / L.

[0051] In the embodiments provided by the present invention, the concentration of lithium salt in the electrolyte is 1 mol / L.

[0052] The present invention also provides a method for preparing the above-mentioned electrolyte, comprising mixing an organic solvent, a lithium salt and additive A, and optionally adding or not adding additive B.

[0053] The present invention also provides a lithium-ion battery comprising the above-described electrolyte.

[0054] In specific embodiments provided by the present invention, the lithium-ion battery further includes a positive electrode, a negative electrode, and a separator.

[0055] In a specific embodiment provided by the present invention, the positive electrode sheet includes a positive current collector and a positive active material layer coated on at least one side of the positive current collector. The positive active material layer includes a positive active material, a conductive agent, and a binder.

[0056] In a specific embodiment provided by the present invention, the mass percentage of each component in the positive electrode active material layer is: 80wt% to 99.8wt% of positive electrode active material, 0.1wt% to 10wt% of conductive agent, and 0.1wt% to 10wt% of binder.

[0057] Preferably, the mass percentage of each component in the positive electrode active material layer is: 90wt% to 99.6wt% of positive electrode active material, 0.2wt% to 5wt% of conductive agent, and 0.2wt% to 5wt% of binder.

[0058] In a specific embodiment provided by the present invention, the negative electrode sheet includes a negative electrode current collector and a negative electrode active material layer coated on at least one side of the negative electrode current collector. The negative electrode active material layer includes a negative electrode active material, a conductive agent, a thickener, and a binder.

[0059] In the specific embodiment provided by the present invention, the mass percentages of each component in the negative electrode active material layer are: 80wt% to 99.8wt% of negative electrode active material, 0.1wt% to 10wt% of conductive agent, 0.1wt% to 10wt% of thickener, and 0.1wt% to 10wt% of binder.

[0060] Preferably, the mass percentages of each component in the negative electrode active material layer are: 90wt% to 99.6wt% of negative electrode active material, 0.2wt% to 5wt% of conductive agent, and 0.2wt% to 5wt% of binder.

[0061] In the specific embodiment provided by the present invention, the conductive agent is selected from at least one of conductive carbon black, acetylene black, Ketjen black, conductive graphite, conductive carbon fibers, carbon nanotubes, metal powder and carbon fibers.

[0062] In the specific embodiment provided by the present invention, the binder is selected from at least one of polyvinylidene fluoride (PVDF), sodium carboxymethyl cellulose, styrene-butadiene latex, polytetrafluoroethylene and polyethylene oxide.

[0063] In the specific embodiment provided by the present invention, the thickener is selected from one or more of sodium carboxymethyl cellulose (CMC), lithium hydroxymethyl cellulose, methyl cellulose, carboxymethyl cellulose, hydroxyethyl cellulose and hydroxypropyl methyl cellulose.

[0064] Preferably, the positive electrode active material comprises at least one of lithium iron phosphate and lithium cobalt oxide.

[0065] In the specific embodiment provided by the present invention, the negative electrode active material comprises a carbon-based negative electrode material and / or a silicon-based negative electrode material.

[0066] In the specific embodiment provided by the present invention, the carbon-based negative electrode material comprises at least one of artificial graphite, natural graphite, mesocarbon microbeads, hard carbon and soft carbon.

[0067] In the specific embodiment provided by the present invention, the silicon-based negative electrode material is selected from nano-silicon, silicon-oxygen negative electrode material (SiO x (0<x<2)) or at least one of silicon-carbon negative electrode materials.

[0068] In the specific embodiment provided by the present invention, the mass ratio of the carbon-based negative electrode material to the silicon-based negative electrode material in the negative electrode active material is 10:0 to 1:19, for example, 1:19, 1:18, 1:17, 1:16, 1:15, 1:14, 1:13, 1:12, 1:11, 1:10, 1:9, 2:8, 3:7, 4:6, 5:5, 6:4, 7:3, 8:2, 9:1 or 10:0.

[0069] In a specific embodiment provided by the present invention, the battery also includes an outer packaging.

[0070] In a specific embodiment provided by the present invention, the battery is prepared by: stacking a positive electrode, a separator, and a negative electrode to obtain a battery cell, or stacking a positive electrode, a separator, and a negative electrode and then winding them to obtain a battery cell, placing the battery cell in an outer packaging, and injecting the electrolyte of the present invention into the outer packaging to obtain the lithium-ion battery of the present invention.

[0071] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0072] 1. The electrolyte additive used in this invention utilizes a redox additive with a redox potential lower than the charging cutoff voltage to ensure the reactivation of dead lithium during cycling, thereby improving the battery's capacity retention. Simultaneously, the redox potential of this additive should be higher than that of the cathode material to prevent self-discharge during cycling. The test results of Examples 1-5 show a significant improvement in cycle life. Therefore, the electrolyte of this invention can activate dead lithium, thereby improving the safety and cycle performance of lithium-ion batteries.

[0073] 2. The redox additives used in this invention require a low concentration in the electrolyte: the redox additives carry a large number of basic charges and have a large diffusion coefficient in the solvent, thereby reducing the concentration of the redox additives in the electrolyte. For example, the required concentration in Examples 2 and 5 is only 0.005M.

[0074] 3. The electrolyte additive used in this invention only reacts with dead lithium during the charging and discharging process and does not react with any other battery components, thus better eliminating dead lithium.

[0075] 4. The electrolyte additive used in this invention has good solubility in the electrolyte and can generate a shuttle effect in the electrolyte. Attached Figure Description

[0076] Figure 1 The capacity retention curve of the battery in Example 2;

[0077] Figure 2 This refers to the lithium plating situation in the battery of Example 2;

[0078] Figure 3 The lithium plating situation in the battery of Comparative Example 1 is shown. Detailed Implementation

[0079] This invention discloses a lithium-ion battery. Those skilled in the art can refer to the content of this document and appropriately modify the process parameters to achieve its realization. It should be particularly noted that all similar substitutions and modifications are obvious to those skilled in the art and are considered to be included in this invention. The methods and applications of this invention have been described through preferred embodiments. Those skilled in the art can clearly modify or appropriately change and combine the methods and applications described herein without departing from the content, spirit, and scope of this invention to realize and apply the technology of this invention.

[0080] The structural formula of toluidine blue is as follows:

[0081]

[0082] The structural formula of tri(4-iodophenyl)amine is as follows:

[0083]

[0084] The structural formula of 2,4,6-triphenylpyran tetrafluoride boron salt is as follows:

[0085]

[0086] The structural formula of S-(trifluoromethyl)-dibenzothiophene tetrafluoroborate is as follows:

[0087]

[0088] The structural formula of trifluoromethanesulfonyl chloride is as follows:

[0089]

[0090] The reagents, instruments, and materials used in this invention can all be obtained through commercial channels.

[0091] The present invention will be further illustrated below with reference to the embodiments:

[0092] Examples 1-5: Preparation of Lithium Iron Phosphate Batteries

[0093] 1. Preparation of positive electrode sheet

[0094] Lithium iron phosphate, PVDF binder, and acetylene black conductive agent were mixed in a mass ratio of 98:1:1. N-methylpyrrolidone was added and the mixture was stirred under vacuum until it was stable and homogeneous to obtain a positive electrode slurry. The positive electrode slurry was uniformly coated onto aluminum foil. After the aluminum foil was dried at room temperature, it was transferred to a 120°C forced-air oven to dry for 1 hour. Then, it was cold-pressed and slit to obtain a positive electrode sheet.

[0095] 2. Preparation of negative electrode sheet

[0096] The negative electrode active material graphite, conductive agent acetylene black, thickener sodium carboxymethyl cellulose (CMC) solution, and binder styrene-butadiene rubber latex were mixed in a mass ratio of 97:1:1:1. Deionized water was added, and the mixture was stirred under vacuum until it was stable and homogeneous to obtain a negative electrode slurry. The negative electrode slurry was uniformly coated onto copper foil, and the copper foil was dried at room temperature and then transferred to a 120°C forced-air oven for 1 hour. After cold pressing and slitting, the negative electrode sheet was obtained.

[0097] 3. Electrolyte preparation

[0098] Preparation of the basic electrolyte: In an argon-filled glove box (moisture < 10 ppm, oxygen < 10 ppm), ethylene carbonate (EC), diethyl carbonate (DEC), and fluoroethylene carbonate (FEC) were uniformly mixed at a volume ratio of EC:DEC:FEC = 4.5:4.5:1. Lithium hexafluorophosphate (LiPF6) was slowly added to the mixed solution until the molar concentration of LiPF6 reached 1 mol / L, thus obtaining the basic electrolyte for lithium-ion batteries. To evaluate the effect of redox media on lithium metal batteries, additive A from Table 1 was added to the basic electrolyte, resulting in Examples 1–5:

[0099] Table 1. Types, performance parameters, and dosages of additive A in each example.

[0100]

[0101] 4. Preparation of Lithium Iron Phosphate Batteries

[0102] The positive electrode, negative electrode, and separator are wound together to obtain the battery cell. After the battery cell is placed in the packaging shell, the electrolyte prepared in the above steps is injected and the shell is sealed. After processes such as standing, compaction, formation, and degassing, a lithium iron phosphate battery is obtained.

[0103] Comparative Example 1:

[0104] Unlike Examples 1-5, the electrolyte in this comparative example is a basic electrolyte, i.e., additive A in Table 1 is not added.

[0105] Battery performance test 1

[0106] The batteries prepared in the above embodiments and comparative examples were subjected to performance tests.

[0107] Performance testing procedure: Under 25℃ conditions, the battery was directly charged at 3C to 3.65V, then discharged at 2C to 2.0V, and this cycle was repeated 4000 times. Afterwards, the battery was charged at 1C to 3.65V, then discharged at a low rate of 0.1C to 2.0V, and this cycle was repeated 20 times. The battery was then dissected, and the capacity retention rate after the first 4000 cycles was analyzed. After dissection, the batteries of each embodiment and comparative example were observed for lithium plating. The results are shown in Table 2 and... Figure 2-3 :

[0108] Table 2 Performance test results of the cells in the examples and comparative examples

[0109]

[0110] The capacity retention curves of Examples 1 to 5 were selected. Figure 1 The capacity retention curve of Example 2 is shown. After 4000 cycles, it dropped to 83-87%, which is better than Comparative Example 1 (81%), indicating that the capacity retention is significantly improved after adding additive A from Table 1 to the base electrolyte. After dissection, the dead lithium in Examples 1-5 was significantly less than that in Comparative Example 1, indicating that by eliminating some or all dead lithium, the battery capacity retention is improved and the cycle life is increased.

[0111] The concentration of additive A in Examples 1-5 is 0.005-0.3M, which is low and has virtually no impact on the safety of the electrolyte and battery.

[0112] As shown in Table 2, the cycle performance of lithium iron phosphate batteries (Examples 1-5) containing the dead lithium activator (additive A of this invention) was significantly improved. Furthermore, after 20 cycles of low-rate discharge, dissection of the batteries revealed no obvious lithium plating (see Table 2). Figure 2 Comparative Example 1, after undergoing the same process, exhibited a lower capacity retention rate than the Example 1, and after low-rate cycle discharge, the dissected battery showed significant lithium plating (see...). Figure 3 Preliminary results indicate that the dead lithium activators of Examples 1-5 significantly improve the cycling performance of lithium iron phosphate (capacity retention rate increased by 2%-6% after 4000 cycles), and this improvement is achieved through the activation of dead lithium, as the comparative examples show obvious lithium plating, while the examples do not.

[0113] The capacity retention rates of Examples 1 through 5 are mainly determined by the structural type and solubility of additive A.

[0114] Examples 1, 3, and 4 are organic ionic compounds, which have low solubility in organic solvents (such as esters like EC), resulting in higher required concentrations of dead lithium activator and lower effectiveness. Examples 2 and 5 are organic nonionic compounds, which have high solubility in organic solvents (such as esters like EC) and good effectiveness, requiring lower concentrations.

[0115] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A lithium-ion battery, characterized in that, The lithium-ion battery includes a positive electrode, a separator, a negative electrode, and an electrolyte. The positive electrode includes a positive electrode active material, and the electrolyte includes additive A. The redox potential of additive A is 3.4~4.0 V, and additive A includes substances that simultaneously satisfy the following conditions: a) Its redox potential is lower than the charging cutoff voltage of lithium-ion batteries; b) Its redox potential is higher than that of the positive electrode active material; The substance includes at least one of the following: c) At least one of toluidine blue, tris(4-iodophenyl)amine, 2,4,6-triphenylpyran tetrafluoroborate, and S-(trifluoromethyl)-dibenzothiophene tetrafluoroborate; d) Derivatives of any one or more of the compounds in c); The negative electrode sheet includes a negative electrode active material, which includes carbon-based negative electrode material and / or silicon-based negative electrode material; The concentration of additive A in the electrolyte is 0.01~0.5 mol / L.

2. The lithium-ion battery according to claim 1, characterized in that, The lithium-ion battery includes at least one of lithium iron phosphate battery, lithium cobalt oxide battery, ternary nickel-cobalt-manganese battery, ternary nickel-cobalt-aluminum battery, lithium manganese oxide battery, lithium nickel oxide battery, lithium titanate battery, and nickel-cobalt-manganese-aluminum battery.

3. The lithium-ion battery according to any one of claims 1-2, characterized in that, The lithium-ion battery is a lithium iron phosphate battery, and the additive A includes a substance with a redox potential of 3.4~4.0 V.

4. The lithium-ion battery according to claim 3, characterized in that, Additive A includes substances with a redox potential of 3.4 to 3.8 V.

5. The lithium-ion battery according to any one of claims 1-2, characterized in that, The lithium-ion battery is a lithium cobalt oxide battery, and additive A includes a substance with a redox potential of 3.6~4.53V; And / or; the lithium-ion battery is a lithium manganese oxide battery, and additive A includes a substance with a redox potential of 3.8~4.2V; And / or; the lithium-ion battery is a ternary nickel-cobalt-manganese battery, and additive A includes a substance with a redox potential of 3.6~4.45V; And / or; the lithium-ion battery is a ternary nickel-cobalt-aluminum battery, and additive A includes a substance with a redox potential of 3.7~4.25V; And / or; the lithium-ion battery is a lithium titanate battery, and additive A includes a substance with a redox potential of 2.4~2.85V.

6. The lithium-ion battery according to any one of claims 1-2, characterized in that, The lithium-ion battery is a lithium cobalt oxide battery, and additive A includes a substance with a redox potential of 3.7~4.4 V; And / or; the lithium-ion battery is a lithium manganese oxide battery, and additive A includes a substance with a redox potential of 3.9~4.0 V; And / or; the lithium-ion battery is a ternary nickel-cobalt-manganese battery, and additive A includes a substance with a redox potential of 3.7~4.4 V; And / or; the lithium-ion battery is a ternary nickel-cobalt-aluminum battery, and additive A includes a substance with a redox potential of 3.7~4.1 V; And / or; the lithium-ion battery is a lithium titanate battery, and additive A includes a substance with a redox potential of 2.5~2.7 V.

7. The lithium-ion battery according to claim 1, characterized in that, The electrolyte also includes organic solvents and lithium salts.

8. The lithium-ion battery according to claim 1, characterized in that, The electrolyte also includes additive B; Additive B includes at least one of cyclic carbonate additives, cyclic sulfonyl lactone additives, nitrile additives, and lithium salt additives.

9. The lithium-ion battery according to claim 7, characterized in that, The concentration of the lithium salt in the electrolyte is 0.1~10 mol / L.

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