Electrolyte additive, electrolyte and lithium ion battery

Abstract

The invention provides an electrolyte additive, an electrolyte and a lithium ion battery in order to solve the problem that the cycle performance of a lithium ion battery becomes poor under a high-voltage condition in the prior art. In the electrolyte additive provided by the invention, an imidazole group in the compound A has relatively strong water and acid removal performance, forms N + ions, forms ion pairs with anions and can also be complexed with transition metal ions, so that damage of HF to SEI and catalysis of the metal ions to an electrolyte system are avoided, and the electrolyte additive has the advantages that the service life of the electrolyte additive is prolonged, the service life of the electrolyte additive is prolonged, and the service life of the electrolyte additive is prolonged. In addition, active groups in the imidazole ring derivative can form SEI films on the positive electrode and the negative electrode, so that the uniformity and the conductivity of the SEI films are improved; in addition, due to the conjugated structure of the SO2-N-SO2 group, anions have negative charge dispersity and good structural flexibility, SEI membrane breakage caused by volume expansion of silicon-carbon, silicon-oxygen and other negative electrode materials is effectively relieved, and the cycle performance of a battery using the silicon negative electrode material can be improved.

Description

Technical Field

[0001] The invention belongs to the technical field of lithium ion batteries, and in particular relates to an electrolyte additive, an electrolyte and a lithium ion battery. Background Art

[0002] Lithium-ion batteries are widely used in consumer electronics and power batteries due to their high specific energy, fast charging and discharging capabilities, and low self-discharge. As the operating conditions of electronic products and power batteries become more and more complex, the requirements for lithium-ion batteries are also getting higher and higher, especially the requirements for battery capacity and life.

[0003] Lithium-ion secondary batteries generally use a mixed solution of cyclic carbonate and chain carbonate as the electrolyte solvent. During the battery cycle and storage process, the solvent will undergo an irreversible redox reaction with the active surface of the electrode material, resulting in a decrease in battery performance. Therefore, functional additives are generally added to the electrolyte to form a protective film on the electrode surface to prevent the reaction between the solvent and the electrode and improve the cycle performance.

[0004] There are many types of electrolyte additives commonly used in the prior art, including vinylene carbonate (VC), 1,3-propane sultone (PS), etc., which can form a protective film on the electrode surface. However, the stability of these protective films is insufficient, especially during high current charge and discharge cycles and high temperature storage. Part of the components of the protective film will decompose and lose its protective effect. The solvent reacts with the electrode and is consumed, resulting in poor cycle performance of the lithium-ion battery under high voltage, which reduces the overall electrical performance of the lithium-ion battery. Summary of the invention

[0005] Aiming at the problem in the prior art that the cycle performance of lithium ion batteries deteriorates under high voltage conditions, an electrolyte additive, an electrolyte and a lithium ion battery are provided.

[0006] The technical solution adopted by the present invention to solve the above technical problems is as follows:

[0007] In one aspect, the present invention provides an electrolyte additive selected from compound A shown in the following structure;

[0008]

[0009] In one aspect, the present invention provides an electrolyte solution, comprising an organic solvent, an electrolyte salt and the electrolyte solution additive.

[0010] Optionally, based on the total mass of the electrolyte being 100%, the mass percentage of the compound A is 0.01% to 8%.

[0011] Optionally, the electrolyte salt is a lithium salt, and the concentration of the lithium salt in the electrolyte is 0.5M to 2M.

[0012] Optionally, the additive further includes an auxiliary additive, and the mass percentage of the auxiliary additive is 0.1% to 10% based on the total mass of the electrolyte as 100%;

[0013] The auxiliary additive includes one or more of vinylene carbonate, vinyl ethylene carbonate, methylene vinyl carbonate, fluoroethylene carbonate and bisfluoroethylene carbonate.

[0014] In another aspect, the present invention provides a lithium ion battery, comprising a positive electrode, a negative electrode and the above-mentioned electrolyte.

[0015] Optionally, the positive electrode includes a positive electrode material layer, the positive electrode material layer includes a lithium supplement additive, and the lithium supplement additive includes Li x M y O z , where 1≤x≤6, 1≤y≤6, 2≤z≤12, and M includes one or more of Ni, Co, Fe, Cu, Al, Mn, Ti, P, Si, and C.

[0016] Optionally, the mass ratio of the lithium supplement additive in the positive electrode material layer is 0.01% to 5%.

[0017] Optionally, the lithium supplement additive is selected from Li2NiO2.

[0018] Optionally, the positive electrode material layer further includes a positive electrode active material, and the mass ratio of the positive electrode active material in the positive electrode material layer is 80% to 99%.

[0019] The electrolyte additive provided by the present application includes compound A, wherein the imidazole group in compound A has strong water removal and acid removal performance, forming N + ions, and form ion pairs with anions, and can also complex transition metal ions to avoid HF damage to SEI and metal ion catalysis of the electrolyte system. In addition, the active groups in the imidazole ring derivatives can form SEI films at the positive and negative electrodes, improving the uniformity and conductivity of the SEI film; in addition, the conjugated structure of the SO2-N-SO2 group makes the anions have negative charge dispersion and good structural flexibility, which can effectively alleviate the SEI film breakage caused by volume expansion of negative electrode materials such as silicon-carbon and silicon-oxygen, and can improve the cycle performance of batteries with silicon negative electrode materials. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 1 is a DQ / DV curve diagram of the electrolyte additive provided by Example 1 and Comparative Example 1 of the present invention (A is Comparative Example 1; B is Example 1). DETAILED DESCRIPTION

[0021] In order to make the technical problems, technical solutions and beneficial effects solved by the present invention more clearly understood, the present invention is further described in detail below in conjunction with the conductive agent embodiment. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0022] The present invention provides an electrolyte additive, selected from compound A shown in the following structure;

[0023]

[0024] It should be noted that lithium-ion secondary batteries generally use a mixed solution of cyclic carbonate and chain carbonate as the electrolyte solvent. During the battery cycle and storage process, the solvent will undergo an irreversible redox reaction with the active surface of the electrode material, resulting in a decrease in battery performance. Therefore, functional additives are generally added to the electrolyte to form a protective film on the electrode surface to prevent the reaction between the solvent and the electrode and improve the cycle performance.

[0025] There are many types of electrolyte additives commonly used in the prior art, including vinylene carbonate (VC), 1,3-propane sultone (PS), etc., which can form a protective film on the electrode surface. However, the stability of these protective films is insufficient, especially during high current charge and discharge cycles and high temperature storage. Part of the components of the protective film will decompose and lose its protective effect. The solvent reacts with the electrode and is consumed, resulting in poor cycle performance of the lithium-ion battery under high voltage, which reduces the overall electrical performance of the lithium-ion battery.

[0026] The electrolyte additive provided by the present application includes compound A, wherein the imidazole group in compound A has strong water removal and acid removal performance, forming N + ions, and form ion pairs with anions, and can also complex transition metal ions to avoid the damage of HF produced by the decomposition of lithium salts to SEI and the catalysis of metal ions to the electrolyte system. In addition, the active groups in the imidazole ring derivatives can form SEI films at the positive and negative electrodes, improving the uniformity and conductivity of the SEI film; in addition, the conjugated structure of the SO2-N-SO2 group makes the anions have negative charge dispersion and good structural flexibility, which can effectively alleviate the SEI film breakage caused by the volume expansion of negative electrode materials such as silicon-carbon and silicon-oxygen, and can improve the cycle performance of batteries with silicon negative electrode materials.

[0027] Specifically, the synthetic route of compound A is as follows:

[0028]

[0029] Specifically, imidazole solution and triethylamine were added to the dichloromethane solution, and the mixture was stirred evenly. 1 mol of acyl chloride was added dropwise, and the mixture was reacted at 60° C. for 2 h to obtain compound a.

[0030] Compound a and allyl alcohol are added to a dichloromethane solvent, triethylamine is added as a catalyst, and the mixture is stirred evenly. A nucleophilic substitution reaction occurs at 60° C. to obtain compound b.

[0031] Compound b and triethylamine (catalyst) were added to dichloromethane solvent, and sulfonyl chloride was added dropwise, stirred evenly, and reacted at 60° C. to obtain compound c.

[0032] Compound c was added to dichloromethane solvent, and after mixing evenly, catalyst triethylamine was added, and the mixture was stirred evenly. The mixture was reacted at 60° C. to obtain compound d.

[0033] Add R1K to the solution of compound d, stir evenly, react in an ice-water bath for several hours, collect the reaction product compound e, and then add lithium hydroxide to obtain compound A.

[0034] Specifically, the compound A is in the form of white powder, slightly soluble in water at 25°C, and has a density of 1.172 g / cm 3 .

[0035] In another embodiment of the present invention, an electrolyte is provided, comprising an organic solvent, an electrolyte salt and an additive, wherein the additive comprises the electrolyte additive described in the present application.

[0036] Specifically, the organic solvent includes at least one of an ether solvent, a nitrile solvent, a carbonate solvent and a carboxylate solvent; the organic solvent is selected from one or more of ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, methyl formate, ethyl formate, ethyl propionate, propyl propionate, methyl butyrate and tetrahydrofuran;

[0037] In one embodiment, based on the total mass of the electrolyte being 100%, the mass percentage of the compound A is 0.01% to 8%.

[0038] Specifically, the mass percentage of the compound A in the electrolyte can be 0.01%, 0.05%, 0.1%, 2%, 3%, 5%, 6% or 8%; preferably, the mass percentage of the compound A in the electrolyte is 0.05% to 5%, and the mass percentage of the compound A in the electrolyte can be 0.05%, 0.1%, 2%, 3% or 5%.

[0039] In one embodiment, the electrolyte salt is a lithium salt, and the concentration of the lithium salt in the electrolyte is 0.5M to 2M.

[0040] Specifically, when the lithium salt concentration is too low, the conductivity of the electrolyte will also decrease, thereby affecting the rate and cycle performance of the entire battery system. When the lithium salt concentration is too high, the viscosity of the electrolyte is too high, which is also not conducive to improving the rate of the battery system. In a preferred embodiment, the lithium salt concentration is 0.9M to 1.3M.

[0041] Specifically, the lithium salt is selected from one or more of an organic electrolyte salt and an inorganic electrolyte salt; the inorganic lithium salt includes but is not limited to LiPF6, LiBF4, LiSbF6, LiAsF6, LiTaF6, LiAlCl4, Li2B 10 Cl 10 、Li2B 10 F 10 , LiClO4, LiCF3SO3, chelated orthoborate and chelated orthophosphate lithium salts; organic lithium salts include but are not limited to lithium bis(oxalatoborate) [LiB(C2O4)2], lithium bis(malonate) borate [LiB(O2CCH2CO2)2], lithium bis(difluoromalonate) borate [LiB(O2CCF2CO2)2], lithium (malonate oxalate) borate [LiB(C2O4)(O2CCH2CO2)], lithium (difluoromalonate oxalate) borate [LiB(C2O4)(O2CCH2CO2)], lithium (difluoromalonate oxalate) borate [LiB(C2O 4) (O2CCF2CO2)], lithium trioxalatephosphate [LiP(C2O4)3] and lithium tris(difluoromalonate)phosphate [LiP(O2CCF2CO2)3].

[0042] In other embodiments, the lithium salt is selected from fluorine-containing lithium salts, including but not limited to hexafluorophosphate, hexafluoroarsenate, perchlorate, trifluorosulfonyl lithium, difluoro(trifluoromethylsulfonyl)imide lithium, bis(fluorosulfonyl)imide lithium, and tris(trifluoromethylsulfonyl)methyl lithium.

[0043] In one embodiment, the additive further includes an auxiliary additive, and the mass percentage of the auxiliary additive is 0.1% to 10% based on the total mass of the electrolyte as 100%;

[0044] The electrolyte auxiliary additive is an indispensable component of the lithium battery electrolyte. The auxiliary additive improves the electrochemical performance of the battery and extends the service life of the battery. Specifically, the auxiliary additive forms a protective film on the electrode surface, which can effectively prevent direct contact between the electrode material and the electrolyte, reduce the occurrence of side reactions, and thus improve the stability and safety of the battery.

[0045] The auxiliary additives include but are not limited to vinylene carbonate and its derivatives, ethylene carbonate derivatives having non-conjugated unsaturated bonds in their side chains, cyclic carbonates substituted by halogens, and salts of chelated orthoborates and chelated orthophosphates. Specifically, the auxiliary additives include one or more of vinylene carbonate, vinyl ethylene carbonate, methylene carbonate, fluoroethylene carbonate and difluoroethylene carbonate. The addition of the auxiliary additives promotes the formation of the SEI film.

[0046] In another embodiment of the present invention, a lithium-ion battery is provided, comprising a positive electrode, a negative electrode and the above-mentioned electrolyte.

[0047] The lithium-ion battery further comprises a negative electrode and a separator, wherein the separator is disposed between the positive electrode and the negative electrode, and the lithium-ion battery is prepared by a winding process / lamination process.

[0048] The negative electrode comprises a negative electrode material layer, the negative electrode material layer comprises a negative electrode active material, a negative electrode binder and a negative electrode conductor, and the negative electrode active material comprises at least one of a carbon-based negative electrode, a silicon-based negative electrode, a tin-based negative electrode and a lithium negative electrode.

[0049] The electrolyte includes the electrolyte additive described in the present application. The electrolyte additive provided in the present application includes compound A. The imidazole group in compound A has strong water and acid removal performance, forms N+ ions, and forms ion pairs with anions. At the same time, it can also complex transition metal ions to avoid HF's destruction of SEI and metal ion catalysis of the electrolyte system. In addition, the active groups in the imidazole ring derivatives can form SEI films at the positive and negative electrodes, thereby improving the uniformity and conductivity of the SEI film.

[0050] In one embodiment, the positive electrode includes a positive electrode material layer, the positive electrode material layer includes a lithium supplement additive, and the lithium supplement additive includes Li x M y O z , where 1≤x≤6, 1≤y≤6, 2≤z≤12, and M includes one or more of Ni, Co, Fe, Cu, Al, Mn, Ti, P, Si, and C.

[0051] Li is added to the positive electrode material layer x M y O z It can provide lithium source during the first charge to compensate for the lithium consumed by the SEI film and improve the first coulomb efficiency. It is especially suitable for negative electrode materials with low first coulomb efficiency such as silicon carbon and silicon oxygen. x M y O z As the amount of addition increases, the initial efficiency of the battery increases, but Li x M y Oz The structure of positive electrode lithium supplement additives such as (Li2NiO2) is unstable after de-lithiation, and it is easy to react with the electrolyte at a high potential to increase the electrode interface impedance and deteriorate the battery performance. At this time, the electrolyte additive (compound A) is added to the electrolyte of the lithium ion battery including the above-mentioned additives. The electrolyte additive has strong dehydration and deacidification performance to form N + ions, and form ion pairs with anions, and can also complex transition metal ions to avoid HF damage to SEI and metal ions catalysis of the electrolyte system. The active groups in the imidazole ring derivatives can form SEI films at the positive and negative electrodes, improve the uniformity and conductivity of the SEI film, and alleviate the side reactions of the positive electrode lithium supplement additive and the electrolyte under high voltage. In addition, the conjugated structure of the SO2-N-SO2 group makes the anion have negative charge dispersion and good structural flexibility, which effectively alleviates the SEI film breakage caused by volume expansion of negative electrode materials such as silicon carbon and silicon oxygen, thereby improving the cycle performance of silicon negative electrode material batteries; in summary, the electrolyte additive and the lithium supplement additive in the lithium ion battery provided in the present application are used simultaneously, which can effectively make up for the defects of the unstable structure of the lithium supplement additive at high potential after delithiation, and jointly promote the formation of a more flexible and more stable SEI film at the negative electrode interface, while effectively improving the first effect of the battery, and improving the battery cycle performance and high voltage performance.

[0052] In one embodiment, the mass ratio of the lithium supplement additive in the positive electrode material layer is 0.01% to 5%.

[0053] Specifically, the mass ratio of the lithium supplement additive described in the present application in the positive electrode material layer may be 0.01%, 0.05%, 0.1%, 0.5%, 1%, 2%, 3%, 4% or 5%.

[0054] In one embodiment, the lithium supplement additive is selected from Li2NiO2.

[0055] Specifically, after adding the lithium supplement additive Li2NiO2 to the positive electrode material layer, a lithium source can be provided during the first charge of the battery to compensate for the lithium consumed by the SEI film, thereby improving the initial coulombic efficiency. x M y O z As the amount of addition increases, the initial efficiency of the battery also improves.

[0056] In one embodiment, the positive electrode material layer further includes a positive electrode active material, and the mass ratio of the positive electrode active material in the positive electrode material layer is 80% to 99%.

[0057] The positive electrode active material in the positive electrode material layer is a key component of the lithium-ion battery and directly affects the performance of the battery. Specifically, the positive electrode active material is the component responsible for providing lithium ions in the lithium battery, and energy storage and release are achieved through the embedding and de-embedding of lithium ions during the charging and discharging process. There is no special restriction on the type and content of the positive electrode active material, and it can be selected according to actual needs, as long as it can reversibly embed / de-embedding lithium ions.

[0058] In a preferred embodiment, the positive electrode active material may be, but is not limited to, lithium iron phosphate, lithium iron manganese phosphate, lithium cobalt oxide, and ternary LiNi a Co b Mn c At least one of the O2 materials (where a+b+c=1, a≥b).

[0059] The present invention is further described below by way of examples.

[0060] The types and contents of the lithium supplement additives and compound A in the following examples and comparative examples are shown in Table 1.

[0061] Table 1

[0062]

[0063]

[0064] Example 1

[0065] This embodiment is used to illustrate an electrolyte additive, electrolyte and lithium ion battery disclosed in the present invention, including the following steps:

[0066] Preparation of electrolyte: EC (ethylene carbonate), DEC (diethyl carbonate), and PP (propyl propionate) are mixed in a mass ratio of 1:1:1 as an organic solvent, compound A in a mass percentage content as shown in Example 1 in Table 1 is added to the organic solvent, and after mixing evenly, LiPF6 is added to obtain an electrolyte with a LiPF6 concentration of 1.15 mol / L.

[0067] Preparation of positive electrode: positive electrode active material lithium cobalt oxide (LiCoO2), conductive agent CNT (carbon nanotube), binder PVDF (polyvinylidene fluoride) are mixed in a mass ratio of 95:1.5:1.5, and the total amount of positive electrode active material is 97%; stir and mix in N-methylpyrrolidone solvent to form a uniform positive electrode slurry, apply the slurry on the positive electrode current collector aluminum foil, dry, and cold press to obtain the positive electrode.

[0068] Preparation of negative electrode: artificial graphite as negative electrode active material, acetylene black as conductive agent, styrene butadiene rubber as binder and sodium carboxymethyl cellulose as thickener are fully stirred and mixed in a deionized water solvent at a mass ratio of 96:1.2:1.5:1.3 to form a uniform negative electrode slurry, and the slurry is coated on the negative electrode current collector copper foil, dried and cold pressed to obtain the negative electrode.

[0069] Preparation of lithium-ion batteries: Using PE porous polymer film as a separator, stack the positive electrode sheet, separator and negative electrode sheet in order, so that the separator is between the positive and negative electrodes, then wind the electrode sheet and the separator to obtain a roll core, place the roll core in an aluminum-plastic film bag that has been punched and formed, and inject the above-prepared electrolyte into the baked and dried battery cells, and obtain a lithium-ion battery after vacuum packaging, standing, formation and other processes.

[0070] Embodiments 2 to 4

[0071] Examples 2 to 4 are used to illustrate an electrolyte additive, electrolyte and lithium ion battery disclosed in the present invention, including most of the operations in Example 1, except that:

[0072] The content of compound A was added according to the content of Examples 2 to 4 in Table 1.

[0073] Embodiments 5 to 15

[0074] Examples 5 to 15 are used to illustrate an electrolyte additive, electrolyte and lithium ion battery disclosed in the present invention, including most of the operations in Example 1, except that:

[0075] The lithium supplement additive and its content as well as compound A and its content are added according to Examples 5 to 15 described in Table 1.

[0076] Comparative Examples 1-2

[0077] Comparative Examples 1 and 2 are used to compare and illustrate an electrolyte additive, electrolyte and lithium ion battery disclosed in the present invention, including most of the operations in Example 1, except that:

[0078] In Comparative Example 1, no lithium supplement additive and compound A were added.

[0079] The added substances and their contents were added according to Comparative Examples 1 to 2 shown in Table 1.

[0080] Performance Testing

[0081] The following performance tests were performed on Examples 1 to 15 and Comparative Examples 1 to 2 prepared as above:

[0082] First battery efficiency test

[0083] After the battery is filled with electrolyte and left to stand for a period of time, it is charged at 25±2℃. First, the charging current is 0.02C and the charging time is 2H; then it is charged with 0.1C current for 5H, and finally it is charged with 0.5C constant current and constant voltage to 4.45V, and the cut-off current is 0.02C. It is discharged with 0.2C until the discharge cut-off voltage is 3.0V. The final first efficiency = discharge capacity / (charged constant current capacity + constant voltage segment capacity).

[0084] 45℃ Cycle Test

[0085] The test method is: charge the lithium-ion battery to 4.45V at 1C constant current and constant voltage in a 45±2℃ constant temperature box, cut off the current at 0.05C, and then discharge it to 3V at 1C. Perform multiple charge and discharge cycles under the above conditions. Calculate the capacity retention rate of the battery after 600 cycles, with 3 batteries in each group. Record the average value.

[0086] Capacity retention rate (%) = 600 cycles discharge capacity (mAh) / third cycle discharge capacity (mAh) * 100%

[0087] Internal resistance increase rate (%) = internal resistance of the cell after 600 cycles / internal resistance of the cell before cycles * 100% - 1.

[0088] DQ / DV tests were performed on Example 1 and Comparative Example 1, and the results were Figure 1 ;

[0089] Depend on Figure 1 It can be clearly seen from the dQ-dV curve that Example 1 with the addition of compound A has a significant reduction peak at around 3.05V. It is preliminarily judged that Example 1 undergoes a reduction reaction at around 3.05V, that is, it is further believed that compound A can participate in the negative electrode SEI film-forming reaction, improve the uniformity and conductivity of the SEI film, and thus improve the cycle performance of the battery with silicon negative electrode materials.

[0090] The test results obtained are entered in Table 2.

[0091] Table 2

[0092]

[0093] From the test results in Table 2, it can be seen that compared with Example 1, Example 1 has a slightly higher first efficiency and cycle capacity retention rate than Example 1. This is because Compound A is added in Example 1, thereby improving the first efficiency and cycle performance of the battery. Since the content of Compound A in the example is only 0.01%, the first efficiency and cycle performance are not significantly improved; compared with Example 1, after 1% of the lithium supplement additive Li2NiO2 is added to Example 2, the first efficiency of the battery is improved, the cycle performance is slightly improved, and the internal resistance increase rate is deteriorated. This is because the positive electrode lithium supplement additive is unstable at high potential and is prone to side reactions with the electrolyte to increase the electrode interface impedance deterioration; compared with Examples 1 to 4, Examples 5 to 8 have better first efficiency and cycle performance than Examples 1 to 4. This is because Examples 5 to 8 simultaneously add the lithium supplement additive Li2NiO2 and Compound A, which can effectively make up for the defect of the lithium supplement additive being unstable at high potential after delithiation. The two synergistically promote the formation of a more flexible and more stable SEI film at the negative electrode interface, improve the battery cycle performance, and improve the battery performance. The first efficiency of the battery; from the test results of Examples 5, 9 to 11, it can be seen that as the content of compound A in the electrolyte increases, its cycle performance is improved; the first efficiency of Examples 12 to 13 is lower than that of other examples, because the content of the lithium supplement additive is relatively low; in Examples 14 to 15, due to the low content of compound A, the cycle performance of the lithium ion battery is also relatively poor; in summary, it can be seen that the imidazole group of compound A in the electrolyte additive of the present application has strong water and acid removal performance, forms N+ ions, and forms ion pairs with anions, and can also complex transition Metal ions can avoid the damage of HF to SEI and the catalysis of metal ions to the electrolyte system. In addition, the active groups in the imidazole ring derivatives can form SEI films at the positive and negative electrodes, thereby improving the uniformity and conductivity of the SEI films. In addition, in the lithium-ion battery provided by the present application, when compound A is used together with the lithium replenishing additive, the defect of the positive electrode lithium replenishing additive being structurally unstable at high potential after delithiation can be effectively compensated, and the formation of a more flexible and structurally stable SEI film at the negative electrode interface can be jointly promoted, while effectively improving the battery's first efficiency, and improving the battery's cycle performance and high voltage performance.

[0094] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. An electrolyte additive, characterized in that: A compound A selected from the following structures, 2. An electrolyte, characterized in that: The invention comprises an organic solvent, an electrolyte salt and an additive, wherein the additive comprises the electrolyte additive according to claim 1.

3. An electrolyte according to claim 2, characterized in that: Taking the total mass of the electrolyte as 100%, the mass percentage of the compound A is 0.01% to 8%.

4. An electrolyte according to claim 2, characterized in that: The electrolyte salt is a lithium salt, and the concentration of the lithium salt in the electrolyte is 0.5M to 2M.

5. An electrolyte according to claim 2, characterized in that: The additive also includes an auxiliary additive, and the mass percentage of the auxiliary additive is 0.1% to 10% based on the total mass of the electrolyte as 100%; The auxiliary additive includes one or more of vinylene carbonate, vinyl ethylene carbonate, methylene vinyl carbonate, fluoroethylene carbonate and bisfluoroethylene carbonate.

6. A lithium ion battery, characterized in that: The invention comprises a positive electrode, a negative electrode and an electrolyte as claimed in any one of claims 2 to 5.

7. A lithium ion battery according to claim 6, characterized in that: The positive electrode comprises a positive electrode material layer, the positive electrode material layer comprises a lithium supplement additive, and the lithium supplement additive comprises Li x M y O z , where 1≤x≤6, 1≤y≤6, 2≤z≤12, and M includes one or more of Ni, Co, Fe, Cu, Al, Mn, Ti, P, Si, and C.

8. A lithium ion battery according to claim 7, characterized in that: The mass ratio of the lithium supplement additive in the positive electrode material layer is 0.01% to 5%.

9. A lithium ion battery according to claim 7, characterized in that: The lithium supplement additive is selected from Li2NiO2.

10. A lithium ion battery according to claim 7, characterized in that: The positive electrode material layer further includes a positive electrode active material, and the mass ratio of the positive electrode active material in the positive electrode material layer is 80% to 99%.

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