Electrolyte for lithium ion battery and lithium ion battery

Abstract

The invention relates to the technical field of lithium ion batteries, and particularly provides an electrolyte for a lithium ion battery. The invention aims to solve the problems that the method for inhibiting the gas production of the lithium ion battery in the prior art increases the electrolyte cost and possibly affects the battery performance. Therefore, the electrolyte for the lithium ion battery comprises a film-forming additive, a lithium salt and a solvent, and further comprises an active oxygen quenching agent. The electrolyte can effectively inhibit gas production of the lithium battery, and can improve the cycle performance of the lithium battery and prolong the service life of the battery.

Description

Technical Field

[0001] The present application relates to the technical field of lithium ion batteries, and specifically provides an electrolyte for lithium ion batteries and a lithium ion battery. Background Art

[0002] Lithium-ion energy storage batteries provide power for portable or mobile devices. In pursuit of longer service life and higher energy density, positive electrode lithium replenishment technology is usually used to compensate for the active lithium consumed in the first cycle of lithium-ion battery charging and provide an active lithium source for subsequent cycles. However, lithium-replenished batteries will generate more gas during the cycle and storage process, causing battery volume expansion, pole piece / diaphragm misalignment to increase battery polarization, and active oxygen released by lithium replenishers to react with the electrolyte, which is an important reason affecting battery life and safety performance. Therefore, it is particularly important to inhibit gas production in the positive electrode lithium-replenished battery system to improve the safety performance and life of the battery throughout its life cycle.

[0003] The commonly used methods for lithium-ion battery gas production include: 1) adding dehydrating and acid-inhibiting additives; 2) reducing the content of cyclic carbonates in the electrolyte; 3) using fluorinated solvents; 4) adding film-forming additives to build a stable SEI film. Although the above methods inhibit battery gas production to a certain extent, they have the following defects: 1) adding dehydrating and acid-inhibiting agents makes the storage conditions of the electrolyte more stringent, increasing the cost; 2) the gas production of the electrolyte mainly comes from cyclic carbonates. Reducing the use of cyclic carbonates can greatly alleviate the gas production problem of the battery, but it has an adverse effect on the performance of the battery; 3) the use of fluorinated solvents will lead to an increase in production costs; 4) the use of film-forming additives will also increase the cost of the battery. In addition, some additives are not environmentally friendly and there is a risk of environmental pollution.

[0004] Accordingly, this field requires a new technical solution to solve the above technical problems. Summary of the invention

[0005] The present application aims to solve the above technical problem, that is, to solve the problem that the method of suppressing gas production of lithium-ion batteries in the prior art increases the cost of electrolyte and may affect the battery performance.

[0006] In a first aspect, the present application provides an electrolyte for a lithium-ion battery, the electrolyte comprising a film-forming additive, a lithium salt and a solvent, and the electrolyte further comprising an active oxygen quencher.

[0007] In the preferred technical scheme of the electrolyte for lithium-ion batteries, the active oxygen quencher includes one or more of piperidine active oxygen quenchers, pyrrole active oxygen quenchers, sulfone active oxygen quenchers, phenol active oxygen quenchers, and olefin active oxygen quenchers.

[0008] In the preferred technical scheme of the electrolyte for lithium-ion batteries, the piperidine active oxygen quencher includes 2,2,6,6-tetramethyl-1-piperidone; and / or, the pyrrole active oxygen quencher includes 5,5-dimethyl-1-pyrroline-N-oxide; and / or, the sulfone active oxygen quencher includes dimethyl sulfoxide; and / or, the phenol active oxygen quencher includes 2,6-di-tert-butyl-p-cresol; and / or, the olefin active oxygen quencher includes 1,4-cyclohexadiene.

[0009] In the preferred technical solution of the electrolyte for lithium-ion batteries, the electrolyte further comprises a transition metal ion masking agent.

[0010] In the preferred technical solution of the electrolyte for lithium-ion batteries, the transition metal ion masking agent is a nitrile organic compound.

[0011] In the preferred technical scheme of the electrolyte for lithium ion batteries, the nitrile organic matter includes at least one of acetonitrile, succinonitrile, adiponitrile, glutaronitrile, suberonitrile, sebaconitrile, 1,3,6-hexanetricarboxylic acid nitrile, 1,3,5-pentanetrinitrile, p-fluorobenzonitrile, p-methylbenzonitrile, 2-fluoroadiponitrile, 2,2-difluorosuccinonitrile, trinitrile benzene, 2-butenenitrile, dicyanoethylene, 1,4-dinitrile-2-butene, methoxyacetonitrile, methoxypropionitrile, 3-ethoxypropionitrile, bis(nitrile ethyl)sulfone, and 3-(trimethylsilyloxy)propionitrile.

[0012] In the preferred technical solution of the electrolyte for lithium ion batteries, the molar ratio of the active oxygen quencher to the transition metal ion masking agent is active oxygen quencher:transition metal ion masking agent=1:(0.1-1.2).

[0013] In the preferred technical solution of the electrolyte for lithium-ion batteries, the molar ratio of the active oxygen quencher to the transition metal ion masking agent is active oxygen quencher:transition metal ion masking agent=1:(0.2-1).

[0014] In the above-mentioned preferred technical solution for the electrolyte of lithium ion battery, the ratio of the sum of the molar amounts of the active oxygen quencher and the transition metal ion masking agent to the molar amount of the lithium salt is lithium salt: (active oxygen quencher + transition metal ion masking agent) = 1: (0.01-0.05).

[0015] In the preferred technical solution of the electrolyte for lithium-ion batteries, the molar ratio of the lithium salt to the film-forming additive is lithium salt: film-forming additive = 1: (0.01-0.02).

[0016] In the preferred technical solution of the electrolyte for lithium-ion batteries, the molar ratio of the lithium salt to the film-forming additive is lithium salt: film-forming additive = 1:0.02.

[0017] In the preferred technical solution of the electrolyte for lithium-ion batteries, the molar ratio of the lithium salt to the solvent is lithium salt:solvent=1:(1-2).

[0018] In the preferred technical solution of the electrolyte for lithium-ion batteries, the molar ratio of the lithium salt to the solvent is lithium salt: solvent = 1:1.5.

[0019] In the above-mentioned preferred technical scheme of the electrolyte for lithium-ion batteries, the solvent includes at least one of dimethyl carbonate, ethylene carbonate, propylene carbonate, ethyl methyl carbonate, and triethyl phosphate; and / or, the lithium salt includes at least one of lithium bis(fluorosulfonyl)imide, trifluoromethanesulfonylimide, and lithium bis(pentafluoroethylsulfonyl)imide; and / or, the film-forming additive includes at least one of vinylene carbonate and fluoroethylene carbonate.

[0020] In a second aspect, the present application provides a lithium-ion battery, wherein the lithium-ion battery comprises the above-mentioned electrolyte for lithium-ion batteries.

[0021] Compared with the prior art, the electrolyte for lithium-ion batteries of the present application has the following advantages: Beneficial effects:

[0022] 1. An active oxygen quencher is added to the electrolyte of the present application, wherein the active oxygen quencher has a high secondary reaction kinetic constant with active oxygen, and thus can react specifically with active oxygen, quench active oxygen in time, inhibit gas production, and improve battery performance and life.

[0023] 2. A transition metal ion masking agent is also added to the electrolyte. The metal ion masking agent can react with the transition metal, reduce the damage of the transition metal ions to the negative electrode SEI film, increase the battery cycle life, and improve battery performance.

[0024] 3. By controlling the molar ratio of the active oxygen quencher to the transition metal ion masking agent to active oxygen quencher: transition metal ion masking agent = 1: (0.1-1.2), and at the same time, the ratio of the sum of the molar amounts of the active oxygen quencher and the transition metal ion masking agent to the molar amount of the lithium salt is lithium salt: (active oxygen quencher + transition metal ion masking agent) = 1: (0.01-0.05), the battery performance can be maximized.

[0025] 4. The electrolyte of the present application has low cost and is easy to store. The lithium-ion battery using the electrolyte has good gas generation inhibition effect, long battery life and good performance. DETAILED DESCRIPTION

[0026] The preferred embodiments of the present application are described below. It should be understood by those skilled in the art that these embodiments are only used to explain the technical principles of the present application and are not intended to limit the protection scope of the present application.

[0027] In this application, the term "and / or" describes the association relationship of associated objects, indicating that there may be three relationships. For example, A and / or B can mean: A exists alone, A and B exist at the same time, and B exists alone. A and B can be singular or plural. The character " / " generally indicates that the associated objects are in an "or" relationship.

[0028] In this application, "at least one" means one or more, and "plurality" means two or more. "At least one of the following" or similar expressions refers to any combination of these items, including any combination of single items or plural items. For example, "at least one of a, b, or c", or "at least one of a, b, and c" can all mean: a, b, c, ab (i.e., a and b), ac, bc, or abc, where a, b, c can be single or multiple, respectively.

[0029] It should be understood that in the various embodiments of the present application, the size of the serial numbers of the above-mentioned processes does not mean the order of execution, some or all of the steps can be executed in parallel or sequentially, and the execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiments of the present application.

[0030] The terms used in the embodiments of the present application are only for the purpose of describing specific embodiments, and are not intended to limit the present application. The singular forms "a", "said" and "the" used in the embodiments of the present application and the appended claims are also intended to include plural forms, unless the context clearly indicates other meanings.

[0031] The weight of the relevant components mentioned in the embodiment description of the present application can not only refer to the specific content of each component, but also represent the proportional relationship between the weights of the components. Therefore, as long as the content of the relevant components is proportionally enlarged or reduced according to the embodiment description of the present application, it is within the scope disclosed in the embodiment description of the present application. Specifically, the mass described in the embodiment description of the present application can be a mass unit known in the chemical industry such as μg, mg, g, kg, etc.

[0032] The terms "first" and "second" are used only for descriptive purposes to distinguish objects such as substances from each other, and should not be understood as indicating or implying relative importance or implicitly indicating the number of indicated technical features. For example, without departing from the scope of the embodiments of the present application, the first XX may also be referred to as the second XX, and similarly, the second XX may also be referred to as the first XX. Thus, the features defined as "first" and "second" may explicitly or implicitly include one or more of the features.

[0033] The experimental methods in the following examples are conventional methods unless otherwise specified, and the materials, reagents, etc. used in the following examples are commercially available unless otherwise specified.

[0034] The prior art methods for inhibiting gas generation in lithium-ion batteries pointed out in the background art have the problems of increasing the cost of electrolyte and possibly affecting battery performance.

[0035] The present application provides an electrolyte for a lithium-ion battery. By adding an active oxygen quencher, the active oxygen quencher has a high secondary reaction kinetic constant with active oxygen, so it can specifically react with active oxygen, quench active oxygen in time, inhibit gas production, increase the battery cycle life, and improve battery performance.

[0036] Specifically, the electrolyte for lithium-ion batteries of the present application includes a film-forming additive, a lithium salt, a solvent, and an active oxygen quencher.

[0037] Reactive oxygen species quenchers are substances that can react quickly with ROS (reactive oxygen species). They react specifically with ROS to prevent ROS from participating in or initiating further oxidative reactions, thereby quenching ROS. These quenchers usually have high secondary reaction kinetic constants with ROS, which means that they can specifically and quickly bind to and react with ROS. Reactive oxygen species (ROS) are a class of oxygen-containing molecules or ions with strong chemical reactivity, including superoxide anions (O 2 - ), hydroperoxide (H 2 O 2 ), hydroxyl radical (·OH), singlet oxygen, etc.

[0038] The electrolyte of the present application can react specifically with active oxygen by adding an active oxygen quencher, quenching active oxygen in time, thereby inhibiting gas production, increasing the battery cycle life cycle, and improving battery performance. Therefore, the lithium-ion battery using the electrolyte has a good effect of inhibiting gas production, a long battery life, and good cycle performance.

[0039] It should be noted that the present application does not impose any restrictions on the specific components of the active oxygen quencher, as long as the active oxygen quencher can react specifically with active oxygen to quench the active oxygen. In practical applications, those skilled in the art can select the specific components of the active oxygen quencher according to actual needs.

[0040] Preferably, the active oxygen quencher includes one or more of a piperidine active oxygen quencher, a pyrrole active oxygen quencher, a sulfone active oxygen quencher, a phenol active oxygen quencher, and an olefin active oxygen quencher.

[0041] Preferably, the piperidine-based active oxygen quencher includes 2,2,6,6-tetramethyl-1-piperidinone.

[0042] Preferably, the pyrrole active oxygen quencher includes 5,5-dimethyl-1-pyrroline-N-oxide.

[0043] Preferably, the sulfone active oxygen quencher includes dimethyl sulfoxide.

[0044] Preferably, the phenolic active oxygen quencher includes 2,6-di-tert-butyl-p-cresol.

[0045] Preferably, the olefin-based active oxygen quencher includes 1,4-cyclohexadiene.

[0046] Preferably, the electrolyte further comprises a transition metal ion sequestering agent.

[0047] Metal masking agents can complex with transition metals, reduce the damage of transition metal ions to the negative electrode SEI film, increase the battery cycle life, and improve battery performance.

[0048] Preferably, the transition metal ion masking agent is a nitrile organic compound.

[0049] The transition metal ion masking agent is set to a nitrile organic matter, which can complex with the transition metal ions, reduce the damage of the transition metal ions to the negative electrode SEI film, improve the cycle characteristics of the battery, and increase the cycle life of the battery.

[0050] Preferably, the nitrile organic matter includes at least one of acetonitrile (AN), succinonitrile (SN), adiponitrile (ADN), glutaronitrile (GLN), suberonitrile, sebaconitrile, 1,3,6-hexanetricarboxylic acid nitrile, 1,3,5-pentanetrinitrile, p-fluorobenzonitrile, p-methylbenzonitrile, 2-fluoroadiponitrile, 2,2-difluorosuccinonitrile, trinitrile benzene, 2-butenenitrile, dicyanoethylene, 1,4-dinitrile-2-butene, methoxyacetonitrile, methoxypropionitrile, 3-ethoxypropionitrile, bis(nitrileethyl)sulfone, and 3-(trimethylsilyloxy)propionitrile.

[0051] Preferably, the molar ratio of the active oxygen quencher to the transition metal ion masking agent is active oxygen quencher:transition metal ion masking agent=1:(0.1-1.2).

[0052] Specifically, the molar ratio of the active oxygen quencher to the transition metal ion masking agent can be 1:0.1, 1:0.2, 1:0.3, 1:0.4, 1:0.5, 1:0.6, 1:0.7, 1:0.8, 1:0.9, 1:1, 1:1.1 or 1:1.2. In actual application, those skilled in the art can determine the molar ratio of the active oxygen quencher to the transition metal ion masking agent according to actual needs.

[0053] More preferably, the molar ratio of the active oxygen quencher to the transition metal ion masking agent is active oxygen quencher:transition metal ion masking agent=1:(0.2-1).

[0054] Specifically, the molar ratio of the active oxygen quencher to the transition metal ion masking agent can be 1:0.2, 1:0.3, 1:0.4, 1:0.5, 1:0.6, 1:0.7, 1:0.8, 1:0.9 or 1:1. In actual application, those skilled in the art can determine the molar ratio of the active oxygen quencher to the transition metal ion masking agent according to actual needs.

[0055] More preferably, the molar ratio of the active oxygen quencher to the transition metal ion masking agent is active oxygen quencher:transition metal ion masking agent=1:1.

[0056] By controlling the molar ratio of the active oxygen quencher to the transition metal ion masking agent, the effect of inhibiting gas production can be better improved, thereby improving the performance of the lithium-ion battery.

[0057] Preferably, in the electrolyte, the ratio of the sum of the molar amounts of the active oxygen quencher and the transition metal ion masking agent to the molar amount of the lithium salt is lithium salt: (active oxygen quencher + transition metal ion masking agent) = 1: (0.01-0.05).

[0058] The present application does not impose any restrictions on the respective amounts of film-forming additives, lithium salts and solvents. In practical applications, those skilled in the art can set the amounts of film-forming additives, quenching additives, lithium salts and solvents according to actual needs. For example, the film-forming additive: lithium salt: solvent = 0.01:1:1; or, the film-forming additive: lithium salt: solvent = 0.01:1.2:2; or, the film-forming additive: lithium salt: solvent = 0.02:1.2:2, and so on. The adjustment and change of the molar ratio of the film-forming additive, lithium salt and solvent do not deviate from the basic principles of the present application and should be limited within the scope of protection of the present application.

[0059] Preferably, the molar ratio of lithium salt to film-forming additive is lithium salt:film-forming additive=1:(0.01-0.02).

[0060] More preferably, the molar ratio of lithium salt to film-forming additive is lithium salt:film-forming additive=1:0.02.

[0061] Preferably, the molar ratio of lithium salt to solvent is lithium salt:solvent=1:(1-2).

[0062] More preferably, the molar ratio of lithium salt to solvent is lithium salt:solvent=1:1.5.

[0063] Controlling the content of other components in the electrolyte relative to the lithium salt can effectively improve the performance of the resulting lithium-ion battery.

[0064] Preferably, the solvent includes at least one of dimethyl carbonate (DMC), ethylene carbonate (EC), propylene carbonate (PC), ethyl methyl carbonate (EMC), and triethyl phosphate (TEP).

[0065] Preferably, the lithium salt includes at least one of lithium bis(fluorosulfonyl)imide (LiFSI), trifluoromethanesulfonylimide (LiTFSI), and lithium bis(pentafluoroethylsulfonyl)imide (LiBETI).

[0066] Preferably, the film-forming additive includes at least one of vinylene carbonate (VC) and fluoroethylene carbonate (FEC).

[0067] In addition, the present application also provides a lithium-ion battery, which includes the above-mentioned electrolyte for lithium-ion batteries.

[0068] The electrolyte for lithium-ion batteries of the present application is described in detail below through several specific embodiments.

[0069] Example 1

[0070] The components of the electrolyte of this embodiment are added according to the following molar ratio: film-forming additive: (active oxygen quencher + transition metal ion masking agent): lithium salt: solvent = 0.02:0.02:1:1.5.

[0071] Among them, the film-forming additive is vinylene carbonate (VC), the active oxygen quencher is 5,5-dimethyl-1-pyrroline-N-oxide (DMPO), the transition metal ion masking agent is acetonitrile (AN), the lithium salt is lithium bis(fluorosulfonyl)imide (LiFSI), and the solvent is vinyl carbonate (EC).

[0072] The molar ratio of the active oxygen quencher to the transition metal ion masking agent is DMPO:AN=1:0.5.

[0073] Example 2

[0074] The components of the electrolyte of this embodiment are added according to the following molar ratio: film-forming additive: (active oxygen quencher + transition metal ion masking agent): lithium salt: solvent = 0.02:0.02:1:1.5.

[0075] Among them, the film-forming additive is vinylene carbonate (VC), the active oxygen quencher is 2,2,6,6-tetramethyl-1-piperidone (TEMPO), the transition metal ion masking agent is acetonitrile (AN), the lithium salt is lithium bis(fluorosulfonyl)imide (LiFSI), and the solvent is vinyl carbonate (EC).

[0076] The molar ratio of the active oxygen quencher to the transition metal ion masking agent is TEMPO:AN=1:0.5.

[0077] Example 3

[0078] The components of the electrolyte of this embodiment are added according to the following molar ratio: film-forming additive: (active oxygen quencher + transition metal ion masking agent): lithium salt: solvent = 0.02:0.02:1:1.5.

[0079] Among them, the film-forming additive is vinylene carbonate (VC), the active oxygen quencher is 2,6-di-tert-butyl-p-cresol (BHT), the transition metal ion masking agent is adiponitrile (ADN), the lithium salt is lithium bis(fluorosulfonyl)imide (LiFSI), and the solvent is vinyl carbonate (EC).

[0080] The molar ratio of the active oxygen quencher to the transition metal ion masking agent is BHT:ADN=1:0.5.

[0081] Example 4

[0082] The components of the electrolyte of this embodiment are added according to the following molar ratio: film-forming additive: (active oxygen quencher + transition metal ion masking agent): lithium salt: solvent = 0.02:0.02:1:1.5.

[0083] Among them, the film-forming additive is vinylene carbonate (VC), the active oxygen quencher is 5,5-dimethyl-1-pyrroline-N-oxide (DMPO), the transition metal ion masking agent is acetonitrile (AN), the lithium salt is lithium bis(fluorosulfonyl)imide (LiFSI), and the solvent is vinyl carbonate (EC).

[0084] The molar ratio of the active oxygen quencher to the transition metal ion masking agent is DMPO:AN=1:0.2.

[0085] Example 5

[0086] The components of the electrolyte of this embodiment are added according to the following molar ratio: film-forming additive: (active oxygen quencher + transition metal ion masking agent): lithium salt: solvent = 0.02:0.02:1:1.5.

[0087] Among them, the film-forming additive is vinylene carbonate (VC), the active oxygen quencher is 5,5-dimethyl-1-pyrroline-N-oxide (DMPO), the transition metal ion masking agent is acetonitrile (AN), the lithium salt is lithium bis(fluorosulfonyl)imide (LiFSI), and the solvent is vinyl carbonate (EC).

[0088] The molar ratio of the active oxygen quencher to the transition metal ion masking agent is DMPO:AN=1:0.8.

[0089] Example 6

[0090] The components of the electrolyte of this embodiment are added according to the following molar ratio: film-forming additive: (active oxygen quencher + transition metal ion masking agent): lithium salt: solvent = 0.02:0.02:1:1.5.

[0091] Among them, the film-forming additive is vinylene carbonate (VC), the active oxygen quencher is 5,5-dimethyl-1-pyrroline-N-oxide (DMPO), the transition metal ion masking agent is acetonitrile (AN), the lithium salt is lithium bis(fluorosulfonyl)imide (LiFSI), and the solvent is vinyl carbonate (EC).

[0092] The molar ratio of the active oxygen quencher to the transition metal ion masking agent is DMPO:AN=1:1.

[0093] Example 7

[0094] The components of the electrolyte of this embodiment are added according to the following molar ratio: film-forming additive: (active oxygen quencher + transition metal ion masking agent): lithium salt: solvent = 0.02:0.02:1:1.5.

[0095] Among them, the film-forming additive is vinylene carbonate (VC), the active oxygen quencher is 5,5-dimethyl-1-pyrroline-N-oxide (DMPO), the transition metal ion masking agent is acetonitrile (AN), the lithium salt is lithium bis(fluorosulfonyl)imide (LiFSI), and the solvent is vinyl carbonate (EC).

[0096] The molar ratio of the active oxygen quencher to the transition metal ion masking agent is DMPO:AN=1:0.1.

[0097] Example 8

[0098] The components of the electrolyte of this embodiment are added according to the following molar ratio: film-forming additive: (active oxygen quencher + transition metal ion masking agent): lithium salt: solvent = 0.02:0.02:1:1.5.

[0099] Among them, the film-forming additive is vinylene carbonate (VC), the active oxygen quencher is 5,5-dimethyl-1-pyrroline-N-oxide (DMPO), the transition metal ion masking agent is acetonitrile (AN), the lithium salt is lithium bis(fluorosulfonyl)imide (LiFSI), and the solvent is vinyl carbonate (EC).

[0100] The molar ratio of the active oxygen quencher to the transition metal ion masking agent is DMPO:AN=1:1.2.

[0101] Example 9

[0102] The components of the electrolyte of this embodiment are added according to the following molar ratio: film-forming additive: (active oxygen quencher + transition metal ion masking agent): lithium salt: solvent = 0.02:0.05:1:1.5.

[0103] Among them, the film-forming additive is vinylene carbonate (VC), the active oxygen quencher is 5,5-dimethyl-1-pyrroline-N-oxide (DMPO), the transition metal ion masking agent is acetonitrile (AN), the lithium salt is lithium bis(fluorosulfonyl)imide (LiFSI), and the solvent is vinyl carbonate (EC).

[0104] The molar ratio of the active oxygen quencher to the transition metal ion masking agent is DMPO:AN=1:0.5.

[0105] Example 10

[0106] The components of the electrolyte of this embodiment are added according to the following molar ratio: film-forming additive: (active oxygen quencher + transition metal ion masking agent): lithium salt: solvent = 0.02:0.01:1:1.5.

[0107] Among them, the film-forming additive is vinylene carbonate (VC), the active oxygen quencher is 5,5-dimethyl-1-pyrroline-N-oxide (DMPO), the transition metal ion masking agent is acetonitrile (AN), the lithium salt is lithium bis(fluorosulfonyl)imide (LiFSI), and the solvent is vinyl carbonate (EC).

[0108] The molar ratio of the active oxygen quencher to the transition metal ion masking agent is DMPO:AN=1:0.5.

[0109] Embodiment 11

[0110] The components of the electrolyte of this embodiment are added according to the following molar ratio: film-forming additive: (active oxygen quencher + transition metal ion masking agent): lithium salt: solvent = 0.02:0.02:1:1.5.

[0111] Among them, the film-forming additive is fluoroethylene carbonate (FEC), the active oxygen quencher is dimethyl sulfoxide (DMSO), the transition metal ion masking agent is succinonitrile (SN), the lithium salt is trifluoromethanesulfonyl imide (LiTFSI), and the solvent is ethyl methyl carbonate (EMC).

[0112] The molar ratio of the active oxygen quencher to the transition metal ion masking agent is DMSO:SN=1:0.5.

[0113] Example 12

[0114] The components of the electrolyte of this embodiment are added according to the following molar ratio: film-forming additive: active oxygen quencher: lithium salt: solvent = 0.02:0.02:1:1.5.

[0115] Among them, the film-forming additive is vinylene carbonate (VC), the active oxygen quencher is 5,5-dimethyl-1-pyrroline-N-oxide (DMPO), the lithium salt is lithium bis(fluorosulfonyl)imide (LiFSI), and the solvent is ethylene carbonate (EC).

[0116] Comparative Example 1

[0117] The components of the electrolyte of this comparative example are added according to the following molar ratio: film-forming additive: lithium salt: solvent = 0.02:1:1.5.

[0118] Among them, the film-forming additive is vinylene carbonate (VC), the lithium salt is lithium bis(fluorosulfonyl)imide (LiFSI), and the solvent is ethylene carbonate (EC).

[0119] Comparative Example 2

[0120] The components of the electrolyte of this embodiment are added according to the following molar ratio: film-forming additive: transition metal ion masking agent: lithium salt: solvent = 0.02:0.02:1:1.5.

[0121] Among them, the film-forming additive is vinylene carbonate (VC), the transition metal ion masking agent is acetonitrile (AN), the lithium salt is lithium bis(fluorosulfonyl)imide (LiFSI), and the solvent is ethylene carbonate (EC).

[0122] Experimental example

[0123] The electrolytes of Examples 1 to 12 and Comparative Examples 1 to 2 were used to inject and prepare lithium ion batteries, and the prepared lithium ion batteries were tested for electrochemical performance and safety performance. The test results are shown in Tables 1 and 2.

[0124] The steps of preparing the lithium-ion battery are as follows: 995 g of electrolyte is injected into a 280 Ah lithium iron phosphate: lithium-rich nickel oxide (1:0.03 g) / graphite battery to prepare a lithium-ion battery.

[0125] The steps of electrochemical performance test are as follows: Cycle test (using three steel clamps to record expansion force): After the battery is placed in a thermostat with a set temperature of 60°C and allowed to stand for 2 hours, a cycle test is performed: 0.5P to 3.65V, standing for 10 minutes, 0.5P DPto 2.5V, standing for 10 minutes; the negative electrode iron ion concentration after 1000 cycles, the cycle expansion force after 1000 cycles, and the battery capacity after 1000 cycles are tested, and the test results are shown in Table 1. Among them, the initial clamp force is 3000N.

[0126] The steps of the safety performance test are as follows: Overcharge safety test: After the battery is charged to 5.5V at 1C, let it stand for 1 hour to observe whether the battery swells, leaks, smokes, catches fire or explodes, and then determine whether the battery passes the safety performance test. Passing means there is no swelling, leakage, smoke, fire or explosion. The test results are shown in Table 2.

[0127] Table 1 Electrochemical performance test results of the batteries prepared in the examples and comparative examples

[0128] Table 2 Safety performance test results of batteries prepared in the examples and comparative examples

[0129] Comparing the embodiment with the comparative example, it can be seen that:

[0130] From the test results in Table 1 and Table 2, we can see that:

[0131] (1) The capacity retention rate of the batteries of Examples 1 to 12 after 1000 cycles is not less than 81%, which is much higher than the capacity retention rate of the battery of Comparative Example 1 after 1000 cycles. It can be seen that the electrolyte of the present application can effectively improve the cycle performance of the battery.

[0132] (2) The iron ion concentration of the negative electrode of the battery of Examples 1 to 11 and Comparative Example 2 at the 1000th cycle is much lower than the iron ion concentration of the negative electrode of the battery of Comparative Example 1 at the 1000th cycle. It can be seen that the iron ion content can be effectively reduced by adding a transition metal ion masking agent, thereby improving the battery performance. In addition, the 1000th cycle expansion force of the batteries of Examples 1 to 11 is much smaller than the 1000th cycle expansion force of the batteries of Comparative Example 1, the 1000th cycle expansion force of the batteries of Examples 12 and Comparative Example 2 is smaller than the 1000th cycle expansion force of the batteries of Comparative Example 1 but higher than that of Examples 1 to 11, and the batteries of Examples 1 to 11 all pass the overcharge safety test, while the batteries of Examples 12, Comparative Example 1 and Comparative Example 2 fail to pass the overcharge safety test. It can be seen that by simultaneously adding an active oxygen quencher and a transition metal ion masking agent to the electrolyte, the gas production of the battery can be better suppressed, thereby reducing the expansion force of the battery during the cycle and improving the safety performance of the battery; and although only adding an active oxygen quencher or only adding a transition metal ion masking agent can suppress the gas production of the battery to a certain extent, the inhibitory effect is relatively weak, so that the active oxygen quencher and the transition metal ion masking agent are used in combination to have a linkage effect, and preferably, the active oxygen quencher and the transition metal ion masking agent are added to the electrolyte at the same time.

[0133] (3) By comparing Example 1 and Examples 4 to 8, it can be seen that the capacity retention rate of the batteries of Examples 7 and 8 after 1000 cycles is lower than the capacity retention rate of the batteries of other examples after 1000 cycles. Therefore, in actual use, it is necessary to control the addition ratio of the active oxygen quencher and the transition metal ion masking agent. It is preferred that the molar ratio of the active oxygen quencher to the transition metal ion masking agent is 1: (0.1 to 1.2), and it is further preferred that the molar ratio of the active oxygen quencher to the transition metal ion masking agent is 1: (0.2 to 1) to better improve the battery performance.

[0134] So far, the technical solutions of the present application have been described in conjunction with the preferred embodiments, but it is easy for those skilled in the art to understand that the protection scope of the present application is obviously not limited to these specific embodiments. Without departing from the principles of the present application, those skilled in the art can make equivalent changes or substitutions to the relevant technical features, and the technical solutions after these changes or substitutions will fall within the protection scope of the present application.

Claims

1. An electrolyte for a lithium ion battery, characterized in that: The electrolyte comprises a film-forming additive, a lithium salt and a solvent, and the electrolyte further comprises an active oxygen quencher.

2. The electrolyte for lithium ion battery according to claim 1, characterized in that: The active oxygen quencher includes one or more of a piperidine active oxygen quencher, a pyrrole active oxygen quencher, a sulfone active oxygen quencher, a phenol active oxygen quencher, and an olefin active oxygen quencher.

3. The electrolyte for lithium ion battery according to claim 2, characterized in that: The piperidine active oxygen quencher includes 2,2,6,6-tetramethyl-1-piperidinone; And / or, the pyrrole active oxygen quencher includes 5,5-dimethyl-1-pyrroline-N-oxide; And / or, the sulfone active oxygen quencher includes dimethyl sulfoxide; And / or, the phenolic active oxygen quencher includes 2,6-di-tert-butyl-p-cresol; And / or, the olefin active oxygen quencher includes 1,4-cyclohexadiene.

4. The electrolyte for lithium ion battery according to any one of claims 1 to 3, characterized in that: The electrolyte also includes a transition metal ion sequestering agent.

5. The electrolyte for lithium ion battery according to claim 4, characterized in that: The transition metal ion masking agent is a nitrile organic compound.

6. The electrolyte for lithium ion battery according to claim 5, characterized in that: The nitrile organic matter includes at least one of acetonitrile, succinonitrile, adiponitrile, glutaronitrile, suberonitrile, sebaconitrile, 1,3,6-hexanetricarboxylic acid nitrile, 1,3,5-pentanetrinitrile, p-fluorobenzonitrile, p-methylbenzonitrile, 2-fluoroadiponitrile, 2,2-difluorosuccinonitrile, trinitrile benzene, 2-butenenitrile, dicyanoethylene, 1,4-dinitrile-2-butene, methoxyacetonitrile, methoxypropionitrile, 3-ethoxypropionitrile, bis(nitrile ethyl)sulfone, and 3-(trimethylsilyloxy)propionitrile.

7. The electrolyte for lithium ion battery according to claim 4, characterized in that: The molar ratio of the active oxygen quencher to the transition metal ion masking agent is active oxygen quencher:transition metal ion masking agent=1:(0.1-1.2).

8. The electrolyte for lithium ion battery according to claim 7, characterized in that: The molar ratio of the active oxygen quencher to the transition metal ion masking agent is active oxygen quencher:transition metal ion masking agent=1:(0.2-1).

9. The electrolyte for lithium ion battery according to claim 4, characterized in that: The ratio of the sum of the molar amounts of the active oxygen quencher and the transition metal ion masking agent to the molar amount of the lithium salt is lithium salt: (active oxygen quencher+transition metal ion masking agent)=1: (0.01-0.05).

10. A lithium ion battery, characterized in that: An electrolyte for a lithium ion battery comprising any one of claims 1 to 9.

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