JPWO2023000255A5 - - Google Patents

Description

The present application belongs to the technical field of lithium batteries, and particularly relates to electrolytes, lithium ion batteries, battery modules, battery bags, and electrical equipment.

In recent years, with the diversification of lithium-ion battery applications, lithium-ion batteries have been used in energy storage power systems such as hydropower, thermal power, wind power, and solar power plants, power tools, electric bicycles, electric motorcycles, electric vehicles, and military equipment. It is widely applied in various fields such as , aviation, and space.

However, when a lithium ion battery is installed in the above electrical equipment, the actual operating environment temperature of the battery will be higher due to the limited installation space and the influence of heat dissipation of other parts of the electrical equipment. Therefore, if only the cycle performance and storage performance of batteries at room temperature are improved, the actual cycle performance and storage performance of batteries in electrical equipment cannot be effectively improved. Therefore, the development and design of lithium-ion batteries with excellent high-temperature cycle performance are of great practical value.

The present application was made in view of the above-mentioned problems, and provides an electrolytic solution that effectively enhances the high-temperature storage performance and high-temperature cycle performance of a battery, a lithium-ion battery containing the electrolytic solution of the present application, a battery module, a battery bag, and a battery bag. Provide electrical equipment.

To achieve the above object, a first aspect of the present application provides an electrolyte. The electrolyte solution includes an electrolyte salt and an organic solvent, the electrolyte salt includes a lithium salt, the organic solvent includes a cyclic ester , a mass fraction of the lithium salt with respect to the electrolyte solution is W1, and the When the mass fraction of the cyclic ester with respect to the electrolytic solution is W2, 0.2≦W1/W2≦1.06 is satisfied.

In an optional embodiment, in the electrolyte of the present application, the W1/W2 range is from 0.5 to 1.06, optionally from 0.8 to 1.0.

In an optional embodiment, in the electrolyte of the present application, the mass fraction B of the mass of the cyclic ester relative to the mass of the organic solvent is between 5% and 18%, optionally between 13% and 16%.

In an optional embodiment, in the electrolyte of the present application, the lithium salt includes at least one of lithium bis(fluorosulfonyl)imide, lithium hexafluorophosphate, and the cyclic ester includes ethylene carbonate, Contains at least one of propylene carbonate.

In an optional embodiment, in the electrolyte of the present application, the sum of the molar concentration C1 of the lithium bis(fluorosulfonyl)imide and the molar concentration C2 of the lithium hexafluorophosphate is 0.86-1.4M.

In any embodiment, the electrolyte of the present application includes a film-forming additive, wherein the mass fraction of the film-forming additive to the electrolyte is A, and the mass fraction of the cyclic ester to the electrolyte is A. When W2 is, 10≦W2/5+2×A≦16 is satisfied.

A second aspect of the present application provides a lithium ion battery including the electrolyte of the first aspect of the present application, a separator, a negative electrode plate, and a positive electrode plate.

In an optional embodiment, the positive electrode plate includes _LiNix Co _y Mn _z O ₂ as a positive electrode active material, the mass fraction of the cyclic ester with respect to the electrolyte is W2, and the content of the nickel atoms is When x is, 0.5≦W2/(100x)≦0.72 is satisfied, and x+y+z=1 is satisfied.

In an optional embodiment, the positive electrode plate includes _LiNix Co _y Mn _z O ₂ as a positive electrode active material, and considering the electrolyte of the present application, the content x of nickel atoms is 0.5 or more. , optionally 0.65, 0.8, 0.96, provided that x+y+z=1.

In an arbitrary embodiment, in the lithium ion battery of the present application, the amount of the negative electrode material supported on the surface of the 1540.25 mm ² current collector (unit: g) is H, and the mass fraction of the cyclic ester relative to the electrolyte is When the ratio is W2, 20≦W2/H≦166 is satisfied.

This application claims that by limiting the mixing of cyclic ester and lithium salt in the electrolyte of lithium ion batteries, the electrolyte containing both cyclic ester and lithium salt has good electrical conductivity and oxidation resistance. , it has system stability and appropriate viscosity, and can improve the conductivity of the negative electrode interface film, so the high-temperature storage performance, high-temperature cycle performance, and power performance of the lithium-ion battery containing it are significantly improved.

FIG. 1 is a schematic diagram of a lithium ion battery according to an embodiment of the present application. FIG. 2 is an exploded view of the lithium ion battery of one embodiment of the present application shown in FIG. FIG. 3 is a schematic diagram of an electrical equipment using a lithium ion battery as a power source, according to an embodiment of the present application.

EMBODIMENT OF THE INVENTION Hereinafter, embodiments of an electrolytic solution, a lithium ion battery, a battery module, a battery bag, and an electric device of the present application will be specifically described with reference to the drawings. Note that explanation of unnecessary parts will be omitted. For example, detailed explanations of well-known techniques or explanations of identical structures may be omitted. This is to avoid the explanation from being too concise and to provide better understanding to those skilled in the art. Further, the drawings and the following description are only provided to enable those skilled in the art to better understand the present application, and are not intended to limit what is described in the claims.

The "range" disclosed in the present invention is defined by a lower limit value and an upper limit value. The predetermined range is defined by selecting a lower limit value and an upper limit value. The selected lower and upper limits define the limits of the particular range. The range defined in this way may or may not include the limit value, and may be arbitrarily combined. That is, it is possible to define a range by combining an arbitrary lower limit and an arbitrary upper limit. For example, if the ranges 60-120 and 80-110 are listed for a particular parameter, it should be understood that the ranges 60-110 and 80-120 are also predictable. In addition, when the lower limit values are 1 and 2 and the upper limit values are 3, 4, and 5, 1 to 3, 1 to 4, 1 to 5, 2 to 3, 2 to 4, 2 to 5 It is understood that any range of is predictable. In this application, unless otherwise specified, the numerical range "a-b" is shorthand for any combination of real numbers between real number a and real number b. For example, the numerical range "0-5" includes all real numbers between "0-5" described in the specification, and "0-5" is only an abbreviation for a combination of these numbers. Moreover, when a parameter is expressed as an integer of 2 or more, it means that it is an integer such as 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc., for example.

Unless stated otherwise, all embodiments and optional embodiments of this application can be combined into new technical solutions.

Unless otherwise specified, all technical features and optional technical features of the present application can be combined into a new technical solution.

Unless stated otherwise, all steps of this application may be performed sequentially or randomly. Preferably, these steps are performed in sequence. For example, if a method includes step (a) and step (b), the method may be performed in the order of step (a) and step (b), or in the order of step (b) and step (a). This includes doing things. For example, the method may further include step (c). In this case, step (c) can be optionally added to the above method, and step (a), step (b), step (c) can be performed in the order, or step (a), step (c), This includes executing step (b) in this order, or executing step (c), step (a), and step (b) in this order.

Unless stated otherwise, the use of "comprising" and "containing" in this application can be construed as open-ended as well as closed-ended. For example, "comprises" and "include" can be interpreted to include or include other components not listed, or can be interpreted to include or contain only the listed components. be.

Unless stated otherwise, the use of the term "or" in this application has a broad meaning. For example, the phrase "A or B" means "A, B, or A and B." More specifically, if A is true (or exists) and B is false (or non-existent), A is false (or non-existent), and B is true (or exists), or A and B If both are true (or exist), then both satisfy the condition "A or B".

Based on their experience in preparing electrolytes, the inventors of the present application have found that by adding a cyclic ester solvent to the electrolyte of lithium ion batteries, they have significantly increased the dissociability of the lithium salt and increased the conductivity of the entire electrolyte. In addition to improving the composition of the negative electrode interfacial film, we have found that it is possible to suppress further side reactions of the solvent on the negative electrode surface, which is very useful for improving the electrochemical performance of batteries.

However, many experiments have shown that when the cyclic ester solvent is added to the electrolyte, the cyclic ester solvent is more likely to be enriched on the positive electrode surface than when other solvents are added. It was found that the resulting cyclic ester is easily oxidized and decomposed, accelerating the outflow of the solvent component in the electrolyte, generating a large amount of gas, and ultimately deteriorating the cycle performance and storage performance of the battery. In addition, the viscosity of the cyclic ester solvent is much higher than that of other commonly used solvents, which increases the viscosity of the electrolyte, which is disadvantageous for lithium ion transport and reduces the electrochemical performance of the battery. It is also disadvantageous.

Furthermore, the inventors' research has revealed that the storage performance and cycle performance of a lithium ion battery containing a cyclic ester solvent in a high temperature environment is significantly worse than in a room temperature environment. Furthermore, the inventors' research has shown that cyclic ester solvents are enriched on the surface of the positive electrode faster and in larger amounts at high temperatures, and that the decomposition of the enriched cyclic esters on the surface of the positive electrode is also accelerated at high temperatures. Therefore, it was speculated that the cause of deterioration in battery cycle performance and storage performance was the high temperature environment.

The inventors studied this and conducted many experiments. By adjusting the relative content of cyclic ester and lithium salt to the electrolytic solution within a specific range, we can ensure sufficient high conductivity of the electrolytic solution, and the positive electrode of such a cyclic ester solvent can be used as a positive electrode. This effectively suppresses the enrichment rate and amount of esters, reduces oxidative decomposition at the positive electrode, and reduces the viscosity of the electrolyte, making it suitable for lithium-ion batteries using cyclic ester solvents under high temperature conditions. It has been found that the cycle performance, storage performance and power performance of the battery can be improved.

The electrolyte recipe of the present application is particularly suitable for ternary lithium ion batteries with a high content of nickel atoms, and even for ternary lithium ion batteries with a very high content of nickel atoms.

The electrolyte recipe of the present application is particularly suitable for improving the cycle performance, storage performance, and power performance of lithium ion batteries at high temperatures.

[Electrolyte]
A first aspect of the present application provides an electrolyte. The electrolyte solution includes an electrolyte salt containing a lithium salt and an organic solvent containing a cyclic ester , where the mass fraction of the lithium salt to the electrolyte solution is W1, and the mass fraction of the cyclic ester to the electrolyte solution is W1. When the mass fraction is W2, 0.2≦W1/W2≦1.06 is satisfied.

The lithium salts of this application include lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, lithium hexafluoroarsenate, lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethanesulfonyl)imide, trifluoromethanesulfonic acid It is selected from at least one of lithium, lithium difluorophosphate, lithium difluorooxalate borate, lithium bisoxalate borate, lithium difluorobisoxalatophosphate, and lithium tetrafluorooxalatophosphate.

The cyclic ester of the present application is selected from one or more of ethylene carbonate (EC), propylene carbonate (PC), butylene carbonate (BC), and vinyl ethylene carbonate (VEC). Optionally, it is selected from at least one of ethylene carbonate and propylene carbonate.

In addition, when the electrolytic solution contains one or more lithium salts, "the mass fraction of the lithium salt with respect to the electrolytic solution" means the mass fraction of the total mass of all lithium salts with respect to the electrolytic solution. Similarly, when the electrolytic solution contains one or more cyclic esters , "the mass fraction of the cyclic esters relative to the electrolytic solution" refers to the total mass of all cyclic esters relative to the electrolytic solution. means mass fraction.

The present application aims to develop an electrolyte recipe that has good conductivity, oxidation resistance, electrolyte stability and appropriate viscosity, and improves the conductivity of the interfacial film of the negative electrode. A large amount of experiments have shown that if the content of cyclic ester and the content of lithium salt in the electrolyte meet a specific relationship (0.2≦W1/W2≦1.06), the electrolyte will be more beneficial than expected. It has good electrical conductivity, oxidation resistance, electrolyte stability and suitable viscosity, as well as improving the conductivity of the interfacial film of the negative electrode and reducing the enrichment of the cyclic ester solvent at the positive electrode. It has been found that lithium ion batteries have good high-temperature cycle performance and high-temperature storage performance because the oxidation rate and enrichment amount are suppressed and oxidative decomposition at the positive electrode is reduced.

Through a large amount of research conducted by the inventors, in order to make the electrolyte for lithium ion batteries have excellent conductivity, the ratio of lithium salt to cyclic ester , W1/W2, is usually adjusted to 1 for commercially available general-purpose electrolytes. I found out that it should be set to .5 or higher. However, it was found that because the ratio of such lithium salt to cyclic ester was too high, oxidative decomposition at the positive electrode became serious, more gas was generated during high-temperature storage, and high-temperature cycle performance deteriorated. . Despite progress over the past several years, it has not been possible to reduce W1/W2, which is the ratio of lithium salt to cyclic ester solvent in the electrolyte solution of lithium ion batteries, to 1.5 or less. Through extensive experiments, the present application has developed an electrolyte that satisfies 0.2≦W1/W2≦1.06, and such an electrolyte can improve the high-temperature storage performance and high-temperature cycle performance of batteries. Ta. See Table 1 for details.

In some embodiments, optionally in the electrolytes of the present application, the W1/W2 range is from 0.5 to 1.06, optionally from 0.8 to 1.0. See Table 1 for details.

By further limiting the range of W1/W2, the components of the electrolytic solution can be optimized and a good solvent can be prepared. With this solvent, the electrolyte forms an inorganic-organic composite interfacial film with excellent conductivity on the surfaces of the positive and negative electrodes, which improves the high-temperature storage performance and high-temperature cycling performance of the battery, and also increases the power performance. It will be done.

Optionally, the W1/W2 range is a numerical range defined by any of the values listed in Table 1.

In some embodiments, optionally, in the electrolyte of the present application, the mass fraction B of the mass of the cyclic ester relative to the mass of the organic solvent is between 5% and 18%, optionally 13%. ~16%.

Research has shown that in commercially available electrolytes containing cyclic ester solvents, the content of cyclic esters relative to the mass of organic solvent is approximately 20% or more. There is a problem in that the amount of gas generated is large, resulting in poor high-temperature cycle performance. This application significantly improves the high-temperature storage performance, high-temperature cycle performance, and power performance of the battery by appropriately adjusting the composition and content of the electrolytic solution and adjusting the cyclic ester content to 5% to 18%. I raised it. Furthermore, by limiting the numerical range of B to within 13% to 16%, the high temperature cycle performance and high temperature storage performance of the lithium ion battery were further improved. See Table 2 for details.

Optionally, the range for B is a numerical range defined by any of the values listed in Table 2.

In some embodiments, optionally in the electrolytes of the present application, the lithium salt is selected from at least one of lithium bis(fluorosulfonyl)imide, lithium hexafluorophosphate.

In some embodiments, where the molar concentration of the lithium bis(fluorosulfonyl)imide is C1 and the molar concentration of the lithium hexafluorophosphate is C2, the ratio C1/C2 is from 0.05 to 5, optionally from 1 to 3.5.

In this application, since the content of the cyclic carbonate is limited, the dissociability of the lithium salt is limited, which affects the conductivity of the electrolytic solution. Through extensive experiments, the inventors have shown that the conductivity of the electrolyte can be improved by using lithium bis(fluorosulfonyl)imide (LiFSI) instead of _LiPF6 , but the use of LiFSI alone However, it was discovered that the corrosion of aluminum foil was accelerated. However, the inventors used a mixture of LiPF ₆ and LiFSI and further determined that the ratio of the molar concentration C1 of the lithium bis(fluorosulfonyl)imide to the molar concentration C2 of the lithium hexafluorophosphate was C1/ By limiting C2 to an appropriate range, it is possible to compensate for the decrease in conductivity of the electrolyte caused by the decrease in the amount of cyclic ester used, and also to prevent corrosion of lithium salt to aluminum foil, which improves battery performance. It has been found that the high-temperature cycle performance and high-temperature storage performance of can be further improved. See Table 3 for details.

Optionally, the C1/C2 range is a numerical range defined by any of the values listed in Table 3.

In some embodiments, optionally, the sum of the molar concentrations of the lithium bis(fluorosulfonyl)imide and the lithium hexafluorophosphate is from 0.86 to 1.4M, optionally from 1 to 1.4M. It is 4M.

Furthermore, it is necessary to limit the total concentration of LiFSI and LiPF ₆ within an appropriate range. This is because when the concentration of lithium salt is too high, the viscosity of the electrolyte is too large, which not only reduces the high temperature cycle and high temperature storage performance of the battery, but also reduces the battery power performance, and on the contrary, the total concentration is too low. This is because the amount of effective transfer of lithium ions is too small and the high temperature cycle performance and high temperature storage performance of the battery deteriorate. See Table 4 for details.

Optionally, the range of the sum of the molar concentrations of lithium bis(fluorosulfonyl)imide and the lithium hexafluorophosphate is a numerical range defined by any of the values listed in Table 4.

In some embodiments, optionally, the electrolyte of the present application includes a deposition additive, wherein the mass fraction of the deposition additive to the electrolyte is A, and the cyclic ester to the electrolyte is When the mass fraction of is W2, 10≦W2/5+2×A≦16 is satisfied. The film forming additive is selected from at least one of fluoroethylene carbonate (FEC), vinylene carbonate (VC), ethylene sulfate (DTD), and 1,3-propane sultone (PS).

Cyclic ester solvents are involved in the formation of positive and negative electrode films in the formation process of lithium ion batteries, but if films are formed using only cyclic esters , the quality of the formed film may be insufficient, and the quality of the battery may be affected. It is not possible to maintain good cycle performance. When used in combination with film-forming additives, the quality of the formed film can be improved.

Many experiments have shown that when the mass fraction A of the film-forming additive to the electrolyte of the present application and the mass fraction W2 of the cyclic ester to the electrolyte satisfy the above formula of the present application, the prepared electrolyte The solution not only ensures high-quality film formation of the positive and negative electrodes, but also maximizes the effectiveness of the cyclic esters used together (improving the overall conductivity of the electrolyte). A lithium-ion battery using it has good high-temperature cycle performance and high-temperature storage performance, and even better power performance. See Table 5 for details.

Optionally, the range W2/5+2×A is a numerical range defined by any value listed in Table 5, optionally from 11.9 to 13.5.

The lithium ion battery of the present application further includes a positive electrode plate, a separator, and a negative electrode plate.

[Positive plate]
The positive electrode plate includes a positive electrode current collector and a positive electrode film layer disposed on at least one surface of the positive electrode current collector and including a positive electrode active material.

For example, a positive electrode current collector has two opposing surfaces in its own thickness direction, and the positive electrode film layer is applied to either one or both of the two opposing surfaces of the positive electrode current collector. It is installed in layers.

In some embodiments, the positive electrode current collector may be a metal foil or a composite current collector. For example, aluminum foil can be used as the metal foil. The composite current collector may include a polymeric material base layer and a metal layer formed on at least one surface of the polymeric material base layer. Composite current collectors combine metal materials (aluminum, aluminum alloys, nickel, nickel alloys, titanium, titanium alloys, silver and silver alloys, etc.) with polymeric substrates (e.g. polypropylene (PP), polyethylene terephthalate (PET), polyethylene terephthalate (PET), etc.). It can be produced by forming it on a base material such as butylene terephthalate (PBT), polystyrene (PS), or polyethylene (PE).

In some embodiments, the cathode active material can be any battery cathode active material known in the art. By way of example, the positive electrode active material may include at least one of an olivine-structured lithium-containing phosphate, a lithium transition metal oxide, and a respective modification compound. It should be noted that the present application is not limited to these materials, but may use other conventional materials that can be used as positive electrode active materials of batteries. These positive electrode active materials may be used alone or in combination of two or more. Among them, examples of lithium transition metal oxides include lithium cobalt oxide (e.g., LiCoO ₂ ), lithium nickel oxide (e.g., LiNiO ₂ ), lithium manganese oxide (e.g., LiMnO ₂ , LiMn ₂ O ₄ ), lithium Nickel cobalt oxide, lithium manganese cobalt oxide, lithium nickel manganese oxide, lithium nickel cobalt manganese oxide (for example, LiNi _1/3 Co _1/3 Mn _1/3 O ₂ (sometimes simply referred to as NCM ₃₃₃ ), LiNi _0.5 Co _0.2 Mn _0.3 O ₂ (sometimes simply referred to as NCM ₅₂₃ ), LiNi _0.5 Co _0.25 Mn _0.25 O ₂ (sometimes simply referred to as NCM ₂₁₁ ), LiNi _0.6 Co _0.2 Mn _0.2 O ₂ (sometimes simply referred to as NCM ₆₂₂ ), LiNi _0.8 Co _0.1 Mn _0.1 O ₂ (sometimes simply referred to as NCM ₈₁₁ )) , lithium nickel cobalt aluminum oxide (e.g., LiNi _0.85 Co _0.15 Al _0.05 O ₂ ) and modified compounds thereof. Examples of olivine-structured lithium-containing phosphates include lithium iron phosphate (e.g., LiFePO ₄ (sometimes simply referred to as LFP)), a composite material of lithium iron phosphate and carbon, lithium manganese phosphate (e.g., LiMnPO ₄ ), a composite material of lithium manganese phosphate and carbon, a composite material of lithium manganese iron phosphate, and a composite material of lithium manganese iron phosphate and carbon, but is not limited thereto.

In some embodiments, the positive electrode membrane layer may further include an adhesive. For example, the adhesive may be polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoropropene-tetrafluoroethylene. terpolymer of tetrafluoroethylene-hexafluoropropene, and a fluorine-containing acrylic resin.

In some embodiments, the positive electrode membrane layer may optionally further include a conductive agent. For example, the conductive agent may include at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

In some embodiments, a positive plate is manufactured as follows. The above components for producing a positive electrode plate, such as a positive electrode active material, a conductive agent, an adhesive, and any other components are dispersed in a solvent (for example, N-methylpyrrolidone) to obtain a positive electrode slurry, and the positive electrode slurry is further mixed into a positive electrode assembly. A positive electrode plate is obtained by applying it to an electric body and going through processes such as drying and cold pressing.

[Negative electrode plate]
The negative electrode plate includes a negative electrode current collector and a negative electrode film layer disposed on at least one surface of the negative electrode current collector and including a negative electrode active material.

As an example, the negative electrode current collector has two surfaces facing each other in its own thickness direction, and the negative electrode film layer is applied to either one or both of the two opposing surfaces of the negative electrode current collector. It is installed in layers.

In some embodiments, the negative electrode current collector may be a metal foil or a composite current collector. For example, copper foil can be used as the metal foil. The composite current collector may include a polymeric material base layer and a metal layer formed on at least one surface of the polymeric material base layer. Composite current collectors combine metal materials (copper, copper alloys, nickel, nickel alloys, titanium, titanium alloys, silver and silver alloys, etc.) with polymeric substrates (e.g. polypropylene (PP), polyethylene terephthalate (PET), polyethylene terephthalate (PET), etc.). It can be manufactured by forming it on a base material such as butylene terephthalate (PBT), polystyrene (PS), or polyethylene (PE).

In some embodiments, the negative electrode active material can be any battery negative active material known in the art. For example, the negative electrode active material may include at least one of artificial graphite, natural graphite, soft carbon, hard carbon, silicon-based material, tin-based material, lithium titanate, and the like. The silicon-based material can be selected from at least one of elemental silicon, silicon oxide, silicon carbon composite, silicon nitrogen composite, and silicon alloy. The tin-based material can be selected from at least one of elemental tin, tin oxide, and tin alloy. Note that the present application is not limited to these materials, and may use other conventional materials that can be used as negative electrode active materials of batteries. These negative electrode active materials may be used alone or in combination of two or more.

In some embodiments, the negative electrode membrane layer may further include an adhesive. The adhesives include styrene butadiene rubber (SBR), polyacrylic acid (PAA), sodium polyacrylate (PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), and polymethacrylic acid (PMAA). ) and carboxymethyl chitosan (CMCS).

In some embodiments, the negative electrode membrane layer may optionally further include a conductive agent. The conductive agent can be selected from at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

In some embodiments, the negative electrode membrane layer may optionally include other adjuvants, such as, for example, a thickening agent (eg, sodium carboxymethyl cellulose (CMC-Na)).

In some embodiments, a negative plate is manufactured as follows. The above components for producing a negative electrode plate, such as a negative electrode active material, a conductive agent, an adhesive, and any other components are dispersed in a solvent (e.g., deionized water) to obtain a negative electrode slurry, and the negative electrode slurry is further used as a negative electrode current collector. A negative electrode plate is obtained by applying the material to the body and going through processes such as drying and cold pressing.

[Separator]
In some embodiments, the lithium ion battery further includes a separator. In this application, the type of separator is not limited, and any porous structure separator with good chemical stability and mechanical stability well known in the art may be selected.

In some embodiments, the material of the separator can be selected from at least one of glass fiber, nonwoven fabric, polyethylene, polypropylene, and polyvinylidene fluoride. The separator may be a single layer film or a multilayer composite film. It is not limited here. When the separator is a multilayer composite film, the materials of each layer may be the same or different. It is not limited here.

In some embodiments, the positive plate, negative plate and separator are fabricated into an electrode unit by a winding or laminating process.

[Lithium ion battery]
The present application further provides a lithium ion battery comprising the electrolyte of the first aspect of the present application.

In some embodiments, the lithium ion battery of the present application includes a positive electrode plate and the electrolyte of the first aspect of the present application. The positive electrode plate includes a positive electrode material of _LiNix Co _y Mn _z O ₂ , of which x+y+z=1. Among them, when the mass fraction of the cyclic ester with respect to the electrolytic solution is W2 and the content of the nickel atoms is x, 0.5≦W2/(100x)≦0.72 is satisfied.

The lithium ion battery manufactured with the electrolyte of the present application and the Ni-Co-Mn layered ternary cathode active material has significantly enhanced electrochemical performance, and the amount of cyclic ester used in the electrolyte and the ternary cathode active material are significantly improved. There is a corresponding relationship with the content x of nickel atoms in the original positive electrode active material. Generally, the higher the content of nickel atoms in the ternary positive electrode active material, the stronger the activity of the ternary positive electrode active material. However, in the process of battery use, the high content of nickel atoms will cause the ternary cathode active material to accelerate the release of oxygen on the cathode surface, accelerating the oxidative decomposition of cyclic esters and other solvents. . Through many experiments, the inventors of the present application found that when the relationship between the amount of electrolyte used and the nickel atom content x of the present application satisfies 0.5≦W2/(100x)≦0.72, the It can improve the oxygen release problem of nickel batteries and effectively reduce the oxidative decomposition of cyclic esters on the surface of the positive electrode, and the ternary lithium ion batteries manufactured using them have good cycle performance and power performance. I discovered that. See Table 6 for details.

In some embodiments, optionally, the content x of the nickel atoms is 0.5 or more, and optionally, the content x of the nickel atoms is 0.5, 0.65, 0.8, 0. It may be .96. See Table 8 for details.

The electrolyte recipe of the present application is particularly suitable for ternary lithium ion batteries with a high content of nickel atoms, and even ternary lithium ion batteries with a very high content of nickel atoms. As a result, it has good high temperature storage performance, high temperature cycle performance and power performance.

In some embodiments, in the lithium ion battery of the present application, the amount (unit: g) of the negative electrode material supported on the surface of the 1540.25 mm ² current collector is H, and the amount of the cyclic ester relative to the electrolyte is When the mass fraction of is W2, 20≦W2/H≦166 is satisfied, and optionally, 50≦W2/H≦141 is satisfied.

Through many experiments, the inventors of the present application found that a synergistic effect can be exerted by selecting the amount of cyclic ester used in the electrolyte of the present application and the amount H of the negative electrode material supported. When the relationship between the two satisfies 20≦W2/H≦166, the electrochemical performance of the entire lithium ion battery can be significantly improved. See Table 7 for details.

In some embodiments, the lithium ion battery of the present application is a battery with a housing.

In some embodiments, a lithium ion battery may include an outer casing. This sheath is used to seal the electrode unit and electrolyte.

In some embodiments, the exterior of the lithium ion battery may be a hard case, such as a hard plastic case, an aluminum case, a steel case, etc. The exterior of the lithium ion battery may be, for example, a soft pack such as a bag-shaped soft pack. The material of the soft pack may be, for example, plastic such as polypropylene, polybutylene terephthalate and polybutylene succinate.

The present application does not particularly limit the shape of the lithium ion battery, and it may be cylindrical, square, or any other shape. For example, FIG. 1 shows a lithium ion battery 5 having a rectangular structure as an example.

In some embodiments, as shown in FIG. 2, the housing includes a housing 51 and a cover plate 53. Here, the housing 51 includes a bottom plate and a side plate connected to the bottom plate, and the bottom plate and the side plate are configured to surround the storage chamber. The housing 51 has an opening that communicates with the storage chamber, and the cover plate 53 seals the storage chamber by covering the opening. The positive electrode plate, negative electrode plate, and separator can form the electrode unit 52 by a winding process or a lamination process. The electrode unit 52 is enclosed in the storage chamber. The electrolyte infiltrates into the electrode unit 52. The number of electrode units 52 included in the lithium ion battery 5 may be one or more, and can be selected by those skilled in the art according to actual needs.

FIG. 3 shows an example electrical installation. The device may be a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle.

Examples Examples of the present application will be described below. It is to be understood that the following examples described are illustrative and are only illustrative of the present application and not limiting of the present application. In the examples, specific conditions may be omitted based on the techniques, conditions, or product instructions described in literature in the field. It is possible to use commercially available conventional reagents or instruments that are commonly used in this field, although the manufacturer is not specified. Unless otherwise specified, the content of each component in the Examples of the present application is calculated based on a mass that does not contain water of crystallization.

Regarding the terms mentioned below, "the electrolyte of Example 1-1" means the electrolyte used in the manufacturing process of the lithium ion battery of Example 1-1, and "the positive electrode plate of Example 1-1" means the electrolyte used in the manufacturing process of the lithium ion battery of Example 1-1. " means the positive electrode plate used in the manufacturing process of the lithium ion battery of Example 1-1, and "the negative electrode plate of Example 1-1" means the positive electrode plate used in the manufacturing process of the lithium ion battery of Example 1-1. "The separator of Example 1-1" means the separator used in the manufacturing process of the lithium ion battery of Example 1-1, and "the lithium ion battery of Example 1-1" , refers to a lithium ion battery manufactured using the positive electrode, separator, negative electrode, and electrolyte of Example 1-1.

The raw materials according to the examples of this application are as follows.

Nickel cobalt manganese ternary material (LiMO ₂ , M is a solid solution of Ni-Co-Mn, see each example for their ratio)
Artificial graphite (Guangdong Kaijin New Energy Technology Co., Ltd.)
N-methylpyrrolidone (NMP, CAS: 872-50-4, Shanghai Macklin Biological Technology Co., Ltd.)
Polyvinylidene fluoride (CAS: 24937-79-9, Shanghai Macklin Biological Technology Co., Ltd.)
Acetylene black (Guangdong Kaijin New Energy Technology Co., Ltd.)
Carbon black, a conductive agent (Guangdong Kaijin New Energy Technology Co., Ltd.)
Acrylate (CAS:25067-02-1, Shanghai Macklin Biological Technology Co., Ltd.)
Ethylene carbonate (EC, CAS: 96-49-1, Shanghai Macklin Biological Technology Co., Ltd.)
Dimethyl carbonate (DMC, CAS: 616-38-6, Shanghai Macklin Biological Technology Co., Ltd.)
Ethyl methyl carbonate (EMC, CAS: 623-53-0, Shanghai Macklin Biological Technology Co., Ltd.)
Lithium hexafluorophosphate (LiPF ₆ , CAS: 21324-40-3, Guangzhou Tianshi High-tech Materials Co., Ltd.)
Bisfluorosulfonimide lithium salt (LiFSI, CAS: 171611-11-3, Guangzhou Tianshi High-tech Materials Co., Ltd.)
Fluoroethylene carbonate (FEC, CAS: 114435-02-8, Guangzhou Tianshi High-tech Materials Co., Ltd.)

Example 1-1
[Preparation of electrolyte]
In a glove box with an argon gas atmosphere with a water content of less than 10 ppm, add 32.64 g of EC, 60.84 g of EMC, 6.25 g of LiPF ₆ , and 0.15 g of LiFSI to a beaker and stir thoroughly to dissolve. An electrolytic solution of this example was obtained.

[Manufacture of positive electrode plate]
Nickel cobalt manganese ternary material (LiNi _0.8 Co _0.1 Mn _0.1 O ₂ ) as the positive electrode active material, polyvinylidene fluoride as the adhesive, and acetylene black as the conductive agent were mixed in a ratio of 8:1:1. They were mixed in a mass ratio, NMP was added as a solvent, and a positive electrode slurry was obtained by stirring with a vacuum stirrer. This positive electrode slurry was uniformly applied to a positive electrode current collector aluminum foil with a thickness of 13 μm in ^an amount of 0.28 g (dry matter)/1540.25 mm2, and after drying the aluminum foil at room temperature, it was heated at 120 °C. It was transferred to an oven and dried for 1 hour, and then cold pressed and cut to obtain a positive electrode plate.

[Manufacture of negative electrode plate]
Artificial graphite, carbon black as a conductive agent, and acrylate as an adhesive were mixed at a mass ratio of 92:2:6, deionized water was added, and a negative electrode slurry was obtained by stirring with a vacuum stirrer. This negative electrode slurry was uniformly applied to an 8 μm thick negative electrode current collector copper foil in ^an amount of 0.18 g (dry matter)/1540.25 mm2, and after the copper foil was dried at room temperature, it was heated at 120°C. It was transferred to an oven and dried for 1 hour, and then cold pressed and cut to obtain a negative electrode plate.

[Separator]
The separator is Cellgard 2400 (Standard) purchased from Cellgard (Company).

[Manufacture of lithium ion batteries]
The positive electrode plate, the separator, and the negative electrode plate are laminated in this order so that the separator is interposed between the positive electrode plate and the negative electrode plate to play a role of isolation, and is wound to form an electric core. Furthermore, the electric core with a capacity of 4.3Ah was placed on the outer foil, and 8.6g of the electrolyte prepared above was injected into the dried battery, and the processes such as vacuum packaging, leaving, formation, and molding were carried out. Through this process, a lithium-ion battery was obtained.

Example 1-2
For the manufacturing process of the lithium ion battery, reference can be made to Example 1-1 as a whole. The difference is that the electrolyte preparation step involves placing 18.17 g of EC, 72.68 g of EMC, 9 g of LiPF ₆ , and 0.15 g of LiFSI in a beaker in a glove box with an argon gas atmosphere with a water content of less than 10 ppm. In addition, after sufficient stirring and dissolution, the electrolytic solution of this example is obtained.

Example 1-3
For the manufacturing process of the lithium ion battery, reference can be made to Example 1-1 as a whole. The difference is that the electrolyte preparation step involves placing 10.10 g of EC, 81.74 g of EMC, 8 g of LiPF ₆ , and 0.15 g of LiFSI in a beaker in a glove box with an argon gas atmosphere with a water content of less than 10 ppm. In addition, after sufficient stirring and dissolution, the electrolytic solution of this example is obtained.

Example 1-4
For the manufacturing process of the lithium ion battery, reference can be made to Example 1-1 as a whole. The difference is that the electrolyte preparation step consists of 12.83 g of EC, 75.648 g of EMC, 11.38 g of LiPF ₆ , 0.15 g of After LiFSI is added and sufficiently stirred and dissolved, the electrolytic solution of this example is obtained.

Example 1-5
For the manufacturing process of the lithium ion battery, reference can be made to Example 1-1 as a whole. The difference is that the electrolyte preparation step consists of 12.67 g of EC, 74.68 g of EMC, 12.5 g of LiPF ₆ , 0.15 g of After LiFSI is added and sufficiently stirred and dissolved, the electrolytic solution of this example is obtained.

Example 1-6
For the manufacturing process of the lithium ion battery, reference can be made to Example 1-1 as a whole. The difference is that the electrolyte preparation step consists of 9.86 g of EC, 79.74 g of EMC, 10.25 g of LiPF ₆ , 0.15 g of After LiFSI is added and sufficiently stirred and dissolved, the electrolytic solution of this example is obtained.

Comparative example 1
For the manufacturing process of the lithium ion battery, reference can be made to Example 1-1 as a whole. The difference is that the electrolyte preparation step consists of 82.98 g of EC, 4.37 g of EMC, 12.5 g of LiPF ₆ , 0.15 g of After LiFSI is added and sufficiently stirred and dissolved, the electrolytic solution of this example is obtained.

Comparative example 2
For the manufacturing process of the lithium ion battery, reference can be made to Example 1-1 as a whole. The difference is that the electrolyte preparation step consists of 10.44 g of EC, 78.03 g of EMC, 11.38 g of LiPF ₆ , 0.15 g of After LiFSI is added and sufficiently stirred and dissolved, the electrolytic solution of this example is obtained.

Example 2-1
For the manufacturing process of the lithium ion battery, reference can be made to Example 1-1 as a whole. The difference is that the electrolyte preparation step is performed in a glove box with an argon gas atmosphere with a water content of less than 10 ppm, and in a beaker containing 2.93 g of PC, 94.67 g of EMC, 2.25 g of LiPF ₆ , and 0.15 g of After LiFSI is added and sufficiently stirred and dissolved, the electrolytic solution of this example is obtained.

Example 2-2
For the manufacturing process of the lithium ion battery, reference can be made to Example 1-1 as a whole. The difference is that the electrolyte preparation step consists of 4.80 g of PC, 91.29 g of EMC, 3.75 g of LiPF ₆ , 0.15 g of After LiFSI is added and sufficiently stirred and dissolved, the electrolytic solution of this example is obtained.

Example 2-3
For the manufacturing process of the lithium ion battery, reference can be made to Example 1-1 as a whole. The difference is that the electrolyte preparation step involves placing 7.51 g of PC, 86.34 g of EMC, 6 g of LiPF ₆ , and 0.15 g of LiFSI in a beaker in a glove box with an argon gas atmosphere with a water content of less than 10 ppm. In addition, after sufficient stirring and dissolution, the electrolytic solution of this example is obtained.

Example 2-4
For the manufacturing process of the lithium ion battery, reference can be made to Example 1-1 as a whole. The difference is that the electrolyte preparation step consists of 9.25 g of PC, 83.22 g of EMC, 7.38 g of LiPF ₆ , 0.15 g of After LiFSI is added and sufficiently stirred and dissolved, the electrolytic solution of this example is obtained.

Example 2-5
For the manufacturing process of the lithium ion battery, reference can be made to Example 1-1 as a whole. The difference is that the electrolyte preparation step consists of 11.76 g of PC, 78.71 g of EMC, 9.38 g of LiPF ₆ , 0.15 g of After LiFSI is added and sufficiently stirred and dissolved, the electrolytic solution of this example is obtained.

Example 2-6
For the manufacturing process of the lithium ion battery, reference can be made to Example 1-1 as a whole. The difference is that the electrolyte preparation step consists of 13.38 g of PC, 75.84 g of EMC, 10.63 g of LiPF ₆ , 0.15 g of After LiFSI is added and sufficiently stirred and dissolved, the electrolytic solution of this example is obtained.

Example 2-7
For the manufacturing process of the lithium ion battery, reference can be made to Example 1-1 as a whole. The difference is that the electrolyte preparation step consists of 15.72 g of PC, 71.62 g of EMC, 12.5 g of LiPF ₆ , 0.15 g of After LiFSI is added and sufficiently stirred and dissolved, the electrolytic solution of this example is obtained.

Example 2-8
For the manufacturing process of the lithium ion battery, reference can be made to Example 1-1 as a whole. The difference is that the electrolyte preparation step consists of 17.22 g of PC, 68.88 g of EMC, 13.75 g of LiPF ₆ , 0.15 g of After LiFSI is added and sufficiently stirred and dissolved, the electrolytic solution of this example is obtained.

Example 3-1
For the manufacturing process of the lithium ion battery, reference can be made to Example 1-1 as a whole. The difference is that the electrolyte preparation step consists of 13.92 g of EC, 73.55 g of EMC, 12.38 g of LiPF ₆ , 0.15 g of After LiFSI is added and sufficiently stirred and dissolved, the electrolytic solution of this example is obtained.

Example 3-2
For the manufacturing process of the lithium ion battery, reference can be made to Example 1-1 as a whole. The difference is that the electrolyte preparation step _is performed in a glove box with an argon gas atmosphere with a water content of less than 10 ppm. After LiFSI is added and sufficiently stirred and dissolved, the electrolytic solution of this example is obtained.

Example 3-3
For the manufacturing process of the lithium ion battery, reference can be made to Example 1-1 as a whole. The difference is that the electrolyte preparation step consists of 15.5 g of EC, 70.55 g of EMC, 6.25 g of LiPF ₆ , 7.7 g of After LiFSI is added and sufficiently stirred and dissolved, the electrolytic solution of this example is obtained.

Example 3-4
For the manufacturing process of the lithium ion battery, reference can be made to Example 1-1 as a whole. The difference is that the electrolyte preparation step involves placing 15.82 g of EC, 69.94 g of EMC, 5 g of LiPF ₆ , and 9.24 g of LiFSI in a beaker in a glove box with an argon gas atmosphere with a water content of less than 10 ppm. In addition, after sufficient stirring and dissolution, the electrolytic solution of this example is obtained.

Example 3-5
For the manufacturing process of the lithium ion battery, reference can be made to Example 1-1 as a whole. The difference is that the electrolyte preparation step _is performed in a glove box with an argon gas atmosphere with a water content of less than 10 ppm. After LiFSI is added and sufficiently stirred and dissolved, the electrolytic solution of this example is obtained.

Example 3-6
For the manufacturing process of the lithium ion battery, reference can be made to Example 1-1 as a whole. The difference is that the electrolyte preparation step is performed in a glove box with an argon gas atmosphere with a water content of less than ₁₀ ppm. After LiFSI is added and sufficiently stirred and dissolved, the electrolytic solution of this example is obtained.

Example 3-7
For the manufacturing process of the lithium ion battery, reference can be made to Example 1-1 as a whole. The difference is that the electrolyte preparation step _is performed in a glove box with an argon gas atmosphere with a water content of less than 10 ppm. After LiFSI is added and sufficiently stirred and dissolved, the electrolytic solution of this example is obtained.

Example 3-8
For the manufacturing process of the lithium ion battery, reference can be made to Example 1-1 as a whole. The difference is that the electrolyte preparation step is performed in a glove box with an argon gas atmosphere with a water content of less than 10 ppm, and in a beaker containing 16.62 g of EC, 68.43 g of EMC, 1.92 g of LiPF ₆ , and 13.03 g of LiPF 6 . After LiFSI is added and sufficiently stirred and dissolved, the electrolytic solution of this example is obtained.

Example 4-1
For the manufacturing process of the lithium ion battery, reference can be made to Example 1-1 as a whole. The difference is that the electrolyte preparation step is performed in a glove box with an argon gas atmosphere with a water content of less than 10 ppm, and in a beaker containing 10.85 g of EC, 79.39 g of EMC, 4.38 g of LiPF ₆ , and 5.39 g of LiPF 6 . After LiFSI is added and sufficiently stirred and dissolved, the electrolytic solution of this example is obtained.

Example 4-2
For the manufacturing process of the lithium ion battery, reference can be made to Example 1-1 as a whole. The difference is that the electrolyte preparation step is performed in a glove box with an argon gas atmosphere with a water content of less than 10 ppm, and in a beaker containing 13.18 g of EC, 74.97 g of EMC, 5.31 g of LiPF ₆ , and 6.55 g of LiPF 6 . After LiFSI is added and sufficiently stirred and dissolved, the electrolytic solution of this example is obtained.

Example 4-3
For the manufacturing process of the lithium ion battery, reference can be made to Example 1-1 as a whole. The difference is that the electrolyte preparation step consists of 15.5 g of EC, 70.55 g of EMC, 6.25 g of LiPF ₆ , 7.70 g of After LiFSI is added and sufficiently stirred and dissolved, the electrolytic solution of this example is obtained.

Example 4-4
For the manufacturing process of the lithium ion battery, reference can be made to Example 1-1 as a whole. The difference is that the electrolyte preparation step _is performed in a glove box with an argon gas atmosphere with a water content of less than 10 ppm. After LiFSI is added and sufficiently stirred and dissolved, the electrolytic solution of this example is obtained.

Example 4-5
For the manufacturing process of the lithium ion battery, reference can be made to Example 1-1 as a whole. The difference is that the electrolyte preparation step is performed in a glove box with an argon gas atmosphere with a water content of less than 10 ppm, and in a beaker containing 22.48 g of EC, 57.3 g of EMC, 9.06 g of LiPF ₆ , and 11.17 g of LiPF 6 . After LiFSI is added and sufficiently stirred and dissolved, the electrolytic solution of this example is obtained.

Example 5-1
For the manufacturing process of the lithium ion battery, reference can be made to Example 1-1 as a whole. The difference is that the electrolyte preparation step consists of 12.30 g of EC, 72.55 g of EMC, 11.44 g of LiPF ₆ , 0.15 g of LiFSI and 3.55 g of FEC were added and sufficiently stirred to dissolve, and then the electrolytic solution of this example was obtained.

Example 5-2
For the manufacturing process of the lithium ion battery, reference can be made to Example 1-1 as a whole. The difference is that the electrolyte preparation step consists of 10.35 g of EC, 75.87 g of EMC, 9.63 g of LiPF ₆ , 0.15 g of LiFSI and 4 g of FEC were added and sufficiently stirred to dissolve, and then the electrolyte solution of this example was obtained.

Example 5-3
For the manufacturing process of the lithium ion battery, reference can be made to Example 1-1 as a whole. The difference is that the electrolyte preparation step _is performed in a glove box with an argon gas atmosphere with a water content of less than 10 ppm. LiFSI and 4.7 g of FEC were added and sufficiently stirred to dissolve, and then the electrolyte solution of this example was obtained.

Example 5-4
For the manufacturing process of the lithium ion battery, reference can be made to Example 1-1 as a whole. The difference is that the electrolyte preparation step is performed in a glove box with an argon gas atmosphere with a water content of less than 10 ppm, and in a beaker containing 10.76 g of EC, 73.31 g of EMC, 10.13 g of LiPF ₆ , and 0.15 g of LiPF 6 . LiFSI and 5.65 g of FEC were added and sufficiently stirred to dissolve, and then the electrolyte solution of this example was obtained.

Example 5-5
For the manufacturing process of the lithium ion battery, reference can be made to Example 1-1 as a whole. The difference is that the electrolyte preparation step is performed in a glove box with an argon gas atmosphere with a water content of less than 10 ppm, and in a beaker containing 11.03 g of EC, 71.29 g of EMC, 10.63 g of LiPF ₆ , and 0.15 g of LiPF 6 . LiFSI and 6.9 g of FEC were added and sufficiently stirred to dissolve, and then the electrolyte solution of this example was obtained.

Example 5-6
For the manufacturing process of the lithium ion battery, reference can be made to Example 1-1 as a whole. The difference is that the electrolyte preparation step consists of 13.55 g of EC, 66.17 g of EMC, 13.13 g of LiPF ₆ , 0.15 g of LiFSI and 7 g of FEC were added and sufficiently stirred to dissolve, and then the electrolyte solution of this example was obtained.

Example 6-1
For the manufacturing process of the lithium ion battery, reference can be made to Example 1-1 as a whole. The difference is that the ternary material used as the positive electrode active material in this example is LiNi _0.99 Co _0.005 Mn _0.005 O ₂ . In addition, in the electrolyte preparation step, 46.286 g of EC, 39.43 g of EMC, 4.13 g of LiPF ₆ , and 10.16 g of LiFSI were placed in a beaker in a glove box with an argon gas atmosphere with a water content of less than 10 ppm. In addition, after sufficient stirring and dissolution, the electrolytic solution of this example is obtained.

Example 6-2
For the manufacturing process of the lithium ion battery, reference can be made to Example 1-1 as a whole. The difference is that the ternary material used as the positive electrode active material in this example is LiNi _0.69 Co _0.16 Mn _0.15 O ₂ .

In addition, in the electrolyte preparation step, 34.28 g of EC, 51.43 g of EMC, 4.13 g of LiPF ₆ , and 10.16 g of LiFSI were placed in a beaker in a glove box with an argon gas atmosphere with a water content of less than 10 ppm. In addition, after sufficient stirring and dissolution, the electrolytic solution of this example is obtained.

Example 6-3
For the manufacturing process of the lithium ion battery, reference can be made to Example 1-1 as a whole. The difference is that the ternary material used as the positive electrode active material in this example is LiNi _0.47 Co _0.15 Mn _0.38 O ₂ .

In addition, in the electrolyte preparation step, 27.86 g of EC, 57.85 g of EMC, 4.13 g of LiPF ₆ , and 10.16 g of LiFSI were placed in a beaker in a glove box with an argon gas atmosphere with a water content of less than 10 ppm. In addition, after sufficient stirring and dissolution, the electrolytic solution of this example is obtained.

Example 6-4
For the manufacturing process of the lithium ion battery, reference can be made to Example 1-1 as a whole. The difference is that the ternary material used as the positive electrode active material in this example is LiNi _0.32 Co _0.19 Mn _0.57 O ₂ .

In addition, in the electrolyte preparation step, 23.14 g of EC, 62.57 g of EMC, 4.13 g of LiPF ₆ , and 10.16 g of LiFSI were placed in a beaker in a glove box with an argon gas atmosphere with a water content of less than 10 ppm. In addition, after sufficient stirring and dissolution, the electrolytic solution of this example is obtained.

Example 6-5
For the manufacturing process of the lithium ion battery, reference can be made to Example 1-1 as a whole. The difference is that the ternary material used as the positive electrode active material in this example is LiNi _0.25 Co _0.18 Mn _0.57 O ₂ . In addition, in the electrolyte preparation step, 20.06 g of EC, 65.65 g of EMC, 4.13 g of LiPF ₆ , and 10.16 g of LiFSI were placed in a beaker in a glove box with an argon gas atmosphere with a water content of less than 10 ppm. In addition, after sufficient stirring and dissolution, the electrolytic solution of this example is obtained.

Example 7-1
For the manufacturing process of the lithium ion battery, reference can be made to Example 1-1 as a whole. The difference is that the coating amount of the negative electrode slurry in this example was 1.698 mg/1540.25 mm ² . In addition, in the preparation step of the electrolytic solution, in a glove box with an argon gas atmosphere with a water content of less than 10 ppm, 30.57 g of EC, 63.31 g of EMC, and 6.11 g of LiPF ₆ were added to a beaker, stirred thoroughly, and dissolved. After that, the electrolytic solution of this example is obtained.

Example 7-2
For the manufacturing process of the lithium ion battery, reference can be made to Example 1-1 as a whole. The difference is that the coating amount of the negative electrode slurry in this example was 0.873 mg/1540.25 mm ² . In addition, in the preparation step of the electrolytic solution, in a glove box with an argon gas atmosphere with a water content of less than 10 ppm, 17.47 g of EC, 73.80 g of EMC, and 8.73 g of LiPF ₆ are added to a beaker, stirred thoroughly, and dissolved. After that, the electrolytic solution of this example is obtained.

Example 7-3
For the manufacturing process of the lithium ion battery, reference can be made to Example 1-1 as a whole. The difference is that the coating amount of the negative electrode slurry in this example was 0.192 mg/1540.25 mm ² . In addition, in the preparation step of the electrolytic solution, in a glove box with an argon gas atmosphere with a water content of less than 10 ppm, 9.61 g of EC, 82.71 g of EMC, and 7.69 g of LiPF ₆ are added to a beaker, stirred thoroughly, and dissolved. After that, the electrolytic solution of this example is obtained.

Example 7-4
For the manufacturing process of the lithium ion battery, reference can be made to Example 1-1 as a whole. The difference is that the coating amount of the negative electrode slurry in this example was 0.158 mg/1540.25 mm ² . In addition, in the preparation step of the electrolytic solution, in a glove box with an argon gas atmosphere with a water content of less than 10 ppm, 12.67 g of EC, 75.94 g of EMC, and 11.4 g of LiPF ₆ are added to a beaker, stirred thoroughly, and dissolved. After that, the electrolytic solution of this example is obtained.

Example 7-5
For the manufacturing process of the lithium ion battery, reference can be made to Example 1-1 as a whole. The difference is that the coating amount of the negative electrode slurry in this example was 0.115 mg/1540.25 mm ² . In addition, in the preparation step of the electrolytic solution, in a glove box with an argon gas atmosphere with a water content of less than 10 ppm, 12.67 g of EC, 74.67 g of EMC, and 12.67 g of LiPF ₆ were added to a beaker, stirred thoroughly, and dissolved. After that, the electrolytic solution of this example is obtained.

Example 7-6
For the manufacturing process of the lithium ion battery, reference can be made to Example 1-1 as a whole. The difference is that the coating amount of the negative electrode slurry in this example was 0.09 mg/1540.25 mm ² . In addition, in the preparation step of the electrolytic solution, in a glove box with an argon gas atmosphere with a water content of less than 10 ppm, 12.67 g of EC, 74.67 g of EMC, and 12.67 g of LiPF ₆ were added to a beaker, stirred thoroughly, and dissolved. After that, the electrolytic solution of this example is obtained.

Example 7-7
For the manufacturing process of the lithium ion battery, reference can be made to Example 1-1 as a whole. The difference is that the coating amount of the negative electrode slurry in this example was 0.079 mg/1540.25 mm ² . In addition, in the preparation step of the electrolytic solution, in a glove box with an argon gas atmosphere with a water content of less than 10 ppm, 12.67 g of EC, 74.67 g of EMC, and 12.67 g of LiPF ₆ were added to a beaker, stirred thoroughly, and dissolved. After that, the electrolytic solution of this example is obtained.

Example 7-8
For the manufacturing process of the lithium ion battery, reference can be made to Example 1-1 as a whole. The difference is that the coating amount of the negative electrode slurry in this example was 0.058 mg/1540.25 mm ² . In addition, in the preparation step of the electrolytic solution, in a glove box with an argon gas atmosphere with a water content of less than 10 ppm, 9.61 g of EC, 80.3 g of EMC, and 10.09 g of LiPF ₆ are added to a beaker, stirred thoroughly, and dissolved. After that, the electrolytic solution of this example is obtained.

Example 8-1
For the manufacturing process of the lithium ion battery, reference can be made to Example 1-1 as a whole. The difference is that the ternary material used as the positive electrode active material in this example is LiNi _0.5 Co _0.2 Mn _0.3 O ₂ .

In addition, in the preparation step of the electrolytic solution, in a glove box with an argon gas atmosphere with a water content of less than 10 ppm, 16 g of EC, 69.6 g of EMC, and 14.4 g of LiPF ₆ were added to a beaker, stirred thoroughly, and dissolved. , to obtain the electrolyte of this example.

Example 8-2
For the manufacturing process of the lithium ion battery, reference can be made to Example 1-1 as a whole. The difference is that the ternary material used as the positive electrode active material in this example is LiNi _0.65 Co _0.05 Mn _0.3 O ₂ .

In addition, in the preparation step of the electrolytic solution, in a glove box with an argon gas atmosphere with a water content of less than 10 ppm, 16 g of EC, 69.6 g of EMC, and 14.4 g of LiPF ₆ were added to a beaker, stirred thoroughly, and dissolved. , to obtain the electrolyte of this example.

Example 8-3
For the manufacturing process of the lithium ion battery, reference can be made to Example 1-1 as a whole. The difference is that the ternary material used as the positive electrode active material in this example is LiNi _0.85 Co _0.05 Mn _0.1 O ₂ .

In addition, in the preparation step of the electrolytic solution, in a glove box with an argon gas atmosphere with a water content of less than 10 ppm, 16 g of EC, 69.6 g of EMC, and 14.4 g of LiPF ₆ were added to a beaker, stirred thoroughly, and dissolved. , to obtain the electrolyte of this example.

Example 8-4
For the manufacturing process of the lithium ion battery, reference can be made to Example 1-1 as a whole. The difference is that the ternary material used as the positive electrode active material in this example is LiNi _0.96 Co _0.02 Mn _0.02 O ₂ .

In addition, in the preparation step of the electrolytic solution, in a glove box with an argon gas atmosphere with a water content of less than 10 ppm, 16 g of EC, 69.6 g of EMC, and 14.4 g of LiPF ₆ were added to a beaker, stirred thoroughly, and dissolved. , to obtain the electrolyte of this example.

[Measurement of parameters and battery performance]
1. Measurement of initial discharge DCR (Direct Current Resistance) Each of the lithium ion batteries of the above example and comparative example was charged to 4.25V at a charging rate of 1C at 25°C, and then the current was reduced to 0.05C. Constant voltage charging is performed until the value becomes smaller than , and further discharge is performed at a discharge rate of 1C for 30 minutes. At this time, the SOC of the battery is 50% and the voltage is V1. Thereafter, the battery is discharged for 30 seconds at a discharge rate of 4C (the current corresponding to 4C is I). The voltage at this time is assumed to be V2. Initial discharge DCR of a lithium ion battery=(V1-V2)/I. For specific numerical values, refer to Tables 1 to 8.

2. Measurement of cycle performance at 60°C At 60°C, charge the battery at a constant current of 1C to 4.25V, then charge at a constant voltage of 4.25V until the current reaches 0.05C. The capacitance was left standing for a minute, and further discharged to 2.5 V at a constant current of 1 C, and the obtained capacity was defined as the initial capacitance C ₀ . The above steps are repeated and counted for the same battery, and the discharge capacity of the battery after 300 cycles is defined as _C300 . The cycle capacity retention rate of the battery after 300 cycles is P=C ₃₀₀ /C ₀ ×100%.

In the above steps, each of the lithium ion batteries of the example and the comparative example is measured. For specific numerical values, refer to Tables 1 to 8.

3. Measurement of storage performance at 60°C At 25°C, charge the battery at a constant current of 0.5C to 4.25V, then charge at a constant voltage of 4.25V until the current reaches 0.05C. The battery was left standing for 5 minutes, and then discharged to 2.5V at a constant current of 0.5C, and the discharge capacity at this time was defined as the initial capacity _C0 .

Furthermore, charge the above battery to 4.25V with a constant current of 0.5C, then charge it with a constant voltage of 4.25V until the current reaches 0.05C, and then place the battery in an incubator at 60°C. , store it for 60 days and take it out. The removed battery was left in an air atmosphere at 25°C, and after the temperature of the lithium ion battery fell to 25°C, the lithium ion battery was discharged to 2.5V at a constant current of 0.5C, and then The lithium ion battery is charged to 4.25V at a constant current of 0.5V, and finally the lithium ion battery is discharged to 2.5V at a constant current of 0.5V. The discharge capacity at this time is assumed to be C1. The retention rate of high temperature storage capacity of the battery stored for 60 days is M=C1/C ₀ ×100%.

In the above steps, each of the other Examples and Comparative Examples is measured. For specific numerical values, refer to Tables 1 to 8.

As can be seen from Table 1, the high-temperature cycle capacity retention rate and high-temperature storage capacity retention rate of the lithium ion batteries of all the examples above are much higher than those of Comparative Examples 1-2, and all of the examples The initial discharge DCR is lower than that of Comparative Example 1-2.

As can be seen from Examples 1-1 to 1-6, when 0.2≦W1/W2≦1.06, the high-temperature cycle capacity retention rate of the lithium ion battery is higher than 75%, The retention rate of high temperature storage capacity is higher than 80% in all cases. Further, the initial discharge DCR was also suppressed to within 20.5 mΩ in all cases. Further, when 0.8≦W1/W2≦1.0, the high temperature cycle capacity retention rate, high temperature storage capacity retention rate, and initial discharge DCR of the lithium ion battery were further improved.

As can be seen from Examples 2-1 to 2-8, when the value of W1/W2 is constant and the value of B is within the range of 5% to 18%, the high temperature cycle capacity of the lithium ion battery The retention rates of all of them are higher than 75%, and the retention rates of high temperature storage capacity are all higher than 80%. Further, the initial discharge DCR was suppressed to less than 17.2 mΩ in all cases. Furthermore, when the value of B was within the range of 13% to 16%, the high temperature cycle capacity retention rate, high temperature storage capacity retention rate, and initial discharge DCR of the lithium ion battery were further improved.

As can be seen from Examples 3-1 to 3-8, when the values of W1/W2 and C1+C2 are constant values, when the value of C1/C2 is within the range of 0.05 to 5, lithium ion The high temperature cycle capacity retention rates of the batteries are all higher than 78.5%, and the high temperature storage capacity retention rates are all higher than 81%. Further, the initial discharge DCR was suppressed to less than 17 mΩ in all cases. Furthermore, when the value of C1/C2 was within the range of 1 to 3.5, the high temperature cycle capacity retention rate, high temperature storage capacity retention rate, and initial discharge DCR of the lithium ion battery were further improved.

As can be seen from Examples 4-1 to 4-5, when the values of W1/W2 and C1/C2 are constant values, the value of (C1+C2) is within the range of 0.86 to 1.4M. When the high temperature cycle capacity retention rate of the lithium ion battery is higher than 81.5%, and the high temperature storage capacity retention rate of the lithium ion battery is higher than 82.3%. Further, the initial discharge DCR was suppressed to less than 17 mΩ in all cases. Furthermore, when the value of (C1+C2) was within the range of 1 to 1.4, the high temperature cycle capacity retention rate, high temperature storage capacity retention rate, and initial discharge DCR of the lithium ion battery were further improved.

As can be seen from Examples 5-1 to 5-6, when W1/W2 is a constant value and the value of W2/5+2×A is within the range of 10 to 16, the high temperature cycle of the lithium ion battery The capacity retention rates are all higher than 83%, and the high temperature storage capacity retention rates are all higher than 84%. Further, the initial discharge DCR was suppressed to less than 16.5 mΩ in all cases. Furthermore, when the value of W2/5+2×A was within the range of 11.9 to 13.5, the high temperature cycle capacity retention rate, high temperature storage capacity retention rate, and initial discharge DCR of the lithium ion battery were further improved. .

As can be seen from Examples 6-1 to 6-5, when the value of W2/(100x) is within the range of 0.5 to 0.72, the retention rate of high temperature cycle capacity of the lithium ion battery is is higher than 81.3%, and both high temperature storage capacity retention rates are higher than 82%. Further, the initial discharge DCR was suppressed to less than 17 mΩ in all cases.

As can be seen from Examples 7-1 to 7-8, when W1/W2 is a constant value, when the value of W2/H is within the range of 20 to 166, the high temperature cycle capacity of the lithium ion battery is The retention rates are all higher than 81.5%, and the retention rates of high temperature storage capacity are all higher than 81.3%. Further, the initial discharge DCR was suppressed to less than 16.9 mΩ in all cases. Furthermore, when the value of W2/H was within the range of 50 to 141, the high temperature cycle capacity retention rate, high temperature storage capacity retention rate, and initial discharge DCR of the lithium ion battery were further improved.

As can be seen from Examples 8-1 to 8-4, among the current _LiNix Co _y Mn _z O ₂ ternary cathode active materials, commonly used ones, that is, the content of nickel atoms is 0, respectively. .5, 0.65, 0.85, and 0.96 ternary cathode active materials have good high temperature cycle capacity retention, high temperature storage capacity retention, and early discharge. Has DCR.

Note that the present application is not limited to the above embodiments. The above-described embodiments are merely illustrative, and all embodiments that have substantially the same configuration, the same operation, and the same effects as the technical idea of the present application are included within the technical scope of the present application. Furthermore, as long as they do not depart from the gist of the present application, various changes to the embodiments that can be imagined by those skilled in the art and other systems in which some of the components of the embodiments are combined are also included within the scope of the present application. .

5... Lithium ion battery 51... Housing 52... Electrode unit 53... Top cover assembly

Claims (11)

An electrolyte solution containing an electrolyte salt and an organic solvent,
the electrolyte salt includes a lithium salt, the organic solvent includes a cyclic ester ,
When the mass fraction of the lithium salt to the electrolytic solution is W1, and the mass fraction of the cyclic ester to the electrolytic solution is W2, 0.2≦W1/W2≦1.06 is satisfied. electrolyte solution. The electrolytic solution according to claim 1, wherein the range of W1/W2 is 0.5 to 1.06, optionally 0.8 to 1.0. Electrolysis according to claim 1 or 2, characterized in that the mass fraction B of the mass of the cyclic ester with respect to the mass of the organic solvent is 5% to 18%, optionally 13% to 16%. liquid. The electrolyte salt includes at least one of lithium bis(fluorosulfonyl)imide and lithium hexafluorophosphate,
The electrolytic solution according to any one of claims 1 to 3, wherein the cyclic ester contains at least one of ethylene carbonate and propylene carbonate. When the molar concentration of the lithium bis(fluorosulfonyl)imide is C1 and the molar concentration of the lithium hexafluorophosphate is C2, their ratio C1/C2 is 0.05 to 5, optionally 1. ~3.5,
Optionally, (C1+C2) as the sum of the molar concentrations of the lithium bis(fluorosulfonyl)imide and the lithium hexafluorophosphate is 0.86 to 1.4M. Electrolyte. further including film-forming additives,
When the mass fraction of the film-forming additive to the electrolytic solution is A, and the mass fraction of the cyclic ester to the electrolytic solution is W2, 10≦W2/5+2×A≦16 is satisfied. The electrolytic solution according to any one of claims 1 to 5. A lithium ion battery comprising a positive electrode plate, a negative electrode plate, and the electrolytic solution according to any one of claims 1 to 6. The positive electrode plate includes _LiNix Co _y Mn _z O ₂ as a positive electrode active material,
When the mass fraction of the cyclic ester with respect to the electrolytic solution is W2, and the content of nickel atoms is x, 0.5≦W2/(100x)≦0.72 is satisfied,
The lithium ion battery according to claim 7, wherein x+y+z=1 is satisfied. The lithium ion battery according to claim 8, wherein the content x of the nickel atoms is 0.5 or more, optionally 0.65, 0.8, or 0.96. When the amount of negative electrode material supported on the surface of the 1540.25 mm ² current collector (unit: g) is H, and the mass fraction of the cyclic ester with respect to the electrolyte is W2, 20≦W2/H≦ The lithium ion battery according to any one of claims 7 to 9, characterized in that the lithium ion battery satisfies 166. Electrical equipment comprising the lithium ion battery according to any one of claims 7 to 10.