A battery and a battery performance prediction method

Abstract

The application provides a battery, comprising a positive electrode, a negative electrode, an electrolyte and a diaphragm between the positive electrode and the negative electrode, the negative electrode comprising a negative electrode active material, the electrolyte comprising a lithium salt, a solvent and a film-forming additive, when the type of the film-forming additive is one, the added amount of the film-forming additive meets formula (I): 36≤m 添 *ρ 负 *d 负 / ρ 添 ≤90 formula (I); when the type of the film-forming additive is n≥2, the added amount of the film-forming additive meets formula (II), wherein, m 添 is the mass of the film-forming additive corresponding to 100g of the negative electrode active material in the battery, in g; ρ 负 is the density of the negative electrode active material, in g / cm 3 ; d 负 is the average particle size of the negative electrode active material, in μm; ρ 添 is the density of the film-forming additive, in g / cm 3 ; m j is the mass of each film-forming additive corresponding to 100g of the negative electrode active material in the battery, and ρ j is the density of each film-forming additive. The application also provides a battery performance prediction method.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of secondary batteries, in particular to a battery and a battery performance prediction method. BACKGROUND

[0002] During the charging and discharging process of a lithium ion battery, the solid electrolyte interface (SEI) film on the surface of the negative electrode will be damaged, and the repair process of the SEI film will consume lithium in the battery, convert lithium into inactive lithium-containing compounds, thereby causing loss of reversible lithium and reducing the initial efficiency and discharge capacity of the battery. Adding a film-forming additive to the electrolyte can improve the stability of the SEI film, but too high a content of the film-forming additive will result in a thicker SEI film and also reduce the cycle capacity of the battery. There is no universal rule for the amount of film-forming additive to be added, which results in slow progress in the development of new batteries and long research time. SUMMARY

[0003] Therefore, the present application provides a battery, in which a film-forming additive is added according to a specific addition rule, so that the film-forming additive can effectively improve the stability and density of the SEI film and the thickness of the SEI film is moderate, and the battery can have good dynamic performance.

[0004] The first aspect of the present application provides a battery, comprising a positive electrode, a negative electrode, an electrolyte and a separator between the positive electrode and the negative electrode, the negative electrode comprising a negative electrode active material, the electrolyte comprising a lithium salt, a solvent and a film-forming additive,

[0005] When the type of the film-forming additive is one, the amount of the film-forming additive added satisfies formula (I):

[0006] 36≤m 添 *ρ 负 *d 负 / ρ 添 ≤90 formula (I);

[0007] When the type of the film-forming additive is n≥2, the amount of the film-forming additive added satisfies formula (II),

[0008]

[0009] wherein m 添 is the mass of the film-forming additive corresponding to 100 g of the negative electrode active material in the battery, in g; p 负 is the density of the negative electrode active material, in g / cm 3 ; d 负 is the average particle size of the negative electrode active material, in μm; p 添 is the density of the film-forming additive, in g / cm 3 ; mj ρ is the density of each film-forming additive. j ρ is the density of each film-forming additive.

[0010] The battery provided in the present application, when the film-forming additive is a single type of film-forming additive, the content of the film-forming additive meets formula (I), the film-forming additive can not only construct a stable SEI film, but also the thickness of the formed SEI film is moderate, and the resistance of lithium ion transmission is small; when the film-forming additive is multiple types of film-forming additives, if the addition amount of the film-forming additive meets formula (II), different types of film-forming additives can cooperate with each other to construct a stable and moderate-thickness SEI film, so that the lithium ion battery has good kinetic performance and a long cycle life.

[0011] Optionally, the film-forming additive comprises one or more of an olefin-based film-forming additive and a sulfur-based film-forming additive.

[0012] Optionally, the olefin-based film-forming additive comprises one or more of vinylene carbonate, fluoroethylene carbonate and vinyl ethylene carbonate; and the sulfur-based film-forming additive comprises one or more of allyl sulfite, methanediol sulfite and vinyl sulfite.

[0013] Optionally, the film-forming additive comprises vinylene carbonate.

[0014] Optionally, when n≥2, the mass percentage of the vinylene carbonate in the film-forming additive is 40% to 80%.

[0015] Optionally, in formula (I), ρ 添 is 1 g / cm 3 to 2 g / cm 3 ; and in formula (II), ρ j is 1 g / cm 3 to 2 g / cm 3 .

[0016] Optionally, the average particle size d 负 of the negative electrode active material is 1 μm to 50 μm.

[0017] Optionally, the density of the negative electrode active material ρ 负 is 1.8 g / cm 3 to 4.5 g / cm 3 .

[0018] Optionally, the negative active material comprises one or more of graphite, hard carbon, soft carbon, graphene, silicon, silicon oxide compound, silicon metal compound, tin, tin carbon compound, tin oxide compound, tin metal compound, lithium silicon alloy, lithium sodium alloy, lithium potassium alloy, lithium aluminum alloy, lithium tin alloy, lithium indium alloy, lithium titanate, iron oxide, lithium titanium phosphate, and one or more of elements such as titanium, aluminum, zinc, germanium, antimony, and oxides, nitrides, sulfides, and phosphides thereof.

[0019] Optionally, the electrolyte comprises a solvent, and the solvent comprises one or more of dimethyl carbonate, diethyl carbonate, ethylene carbonate, propylene carbonate, methyl ethyl carbonate, methyl propyl carbonate, dipropyl carbonate, and vinylene carbonate.

[0020] Optionally, the electrolyte comprises a lithium salt, and the lithium salt comprises one or more of lithium hexafluorophosphate, lithium perchlorate, lithium tetrafluoroborate, lithium hexafluoroarsenate, lithium hexafluorosilicate, lithium chloroaluminate, lithium bisoxalate borate, lithium trifluoromethylsulfonate, lithium bis-trifluoromethylsulfonylimide, lithium tetraphenylborate, and lithium fluorocarbylsulfonate.

[0021] In a second aspect, the present application provides an electronic device comprising the battery provided in the first aspect of the present application, wherein the battery supplies power to the electronic device.

[0022] In a third aspect, the present application provides a battery performance prediction method, wherein the battery comprises a positive electrode, a negative electrode, an electrolyte, and a separator between the positive electrode and the negative electrode, the negative electrode comprises a negative active material, the electrolyte comprises a lithium salt, a solvent, and a film-forming additive, and the battery performance prediction method comprises:

[0023] predicting the battery performance according to a film-forming factor, wherein the film-forming factor is shown in formula (III):

[0024]

[0025] wherein n is the number of types of film-forming additives, ρ 负 is the density of the negative active material, in units of g / cm 3 ; d 负 is the average particle size of the negative active material, in units of μm; m j is the mass of each film-forming additive corresponding to 100 g of the negative active material in the battery, ρ j is the density of each film-forming additive;

[0026] when n = 1 and the value of the film-forming factor is 36-90, it indicates that the addition amount of the film-forming additive is reasonable, and the battery has good kinetic performance;

[0027] When n≥2 and the value of the film-forming factor is 42-108, it indicates that the addition amount of the film-forming additive is reasonable, and the battery has good kinetic performance.

[0028] The battery performance prediction method provided in the third aspect of the present application predicts the performance of the SEI film formed on the surface of the battery based on the addition amount of the film-forming additive in the battery, thereby predicting the performance of the battery. This method provides a new idea for predicting the performance of the battery and has good application prospects. BRIEF DESCRIPTION OF DRAWINGS

[0029] Figure 1 The structural schematic diagram of the battery provided in an embodiment of the present application is shown. DETAILED DESCRIPTION

[0030] The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor fall within the scope of protection of the present application.

[0031] Batteries have a wide range of applications in the field of portable power sources. With the progress of science and technology, the requirements for battery performance are becoming higher and higher. Adding additives to the battery electrolyte can improve the energy density of the battery and improve the performance of the battery. Film-forming additives can promote the formation of a good SEI film, maintain the stability of the electrode material performance, and improve the battery capacity and cycle performance. If the addition amount of the film-forming additive is too small or the types of the film-forming additive are not properly matched, it will lead to poor stability and compactness of the SEI film on the surface of the negative active material. In the long cycle process, the electrolyte will consume and deteriorate the battery, resulting in a decrease in the cycle performance of the battery. If the addition amount of the film-forming additive is too large, it will lead to the formation of a relatively thick SEI on the surface of the negative active material, and the resistance of lithium ion shuttling will increase. The battery will consume more lithium ions during the formation and capacity test process, thereby reducing the cycle capacity of the battery. Therefore, reasonable addition amount and type matching of the additive are the key to the good dynamic performance and cycle performance of the lithium ion power battery. However, there is no universally applicable rule for the addition amount of the additive at present, which leads to a long research and development cycle of new batteries, high experimental cost, and is not conducive to the development of batteries with high energy density and good cycle performance.

[0032] To improve the electrochemical performance and safety performance of the battery, the present application designs a new battery. The film-forming additive in the battery is added according to a specific addition rule, so that the film-forming additive can effectively improve the stability and compactness of the SEI film, and the thickness of the SEI film is moderate, so that the battery can have good dynamic performance. Please refer to Figure 1 , Figure 1A schematic structural diagram of a battery according to an embodiment of the present application is provided, the battery comprising a positive electrode 10, a negative electrode 20, an electrolyte 40 and a separator 30 between the positive electrode 10 and the negative electrode 20, wherein the negative electrode comprises a negative electrode active material, and the electrolyte comprises a film-forming additive.

[0033] In the battery of the present application, the amount of the film-forming additive added is related to the negative electrode active material, and in the adding rule, the density of the negative electrode active material is ρ 负 , the unit of ρ 负 is g / cm 3 , the average particle size of the negative electrode active material is d 负 , the unit of d 负 is μm, and the amount of the film-forming additive corresponding to 100 g of the negative electrode active material is taken as the amount of the film-forming additive m 添 , the unit of m 添 is g. Wherein, the mass of the film-forming additive corresponding to 100 g of the negative electrode active material m 添 means that when the mass of the negative electrode active material in the battery is m 负 , the mass of the film-forming additive in the battery is m 负 ×m 添 / 100.

[0034] In the present application, the adding rule of the film-forming additive is divided into single type film-forming additive and combined type film-forming additive according to the number of types of the film-forming additive, and the number of types of the film-forming additive is n, n = 1 means that the film-forming additive is single component, and n ≥ 2 means that the film-forming additive is multiple components.

[0035] When n = 1, the density of the film-forming additive is ρ 添 , the unit of ρ 添 is g / cm 3 , and the amount of the film-forming additive m 添 complies with formula (A), and formula (A) is as follows:

[0036]

[0037] In formula (A), represents the volume of the film-forming additive on the surface of a single negative electrode active material, and for a single negative electrode active material, the surface area is When the thickness of the film-forming additive coated on the surface of a single negative electrode active material is 0.06 μm to 0.15 μm, the film-forming additive can form a stable SEI film and the impedance of the SEI film is small, and the lithium ion transmission performance is good.

[0038] Formula (I) can be obtained by simplifying formula (A), and formula (I) is as follows:

[0039] 36 ≤ m 添 * p 负*d 负 / ρ 添 ≤90

[0040] The density ρ of the negative electrode active material in the battery 负 The average particle size d of the negative electrode active material 负 Density ρ of film-forming additives 添 Substituting into equation (I), we can obtain the amount of film-forming additive m corresponding to 100g of negative electrode active material. 添 Range, when the amount of film-forming additive added to the battery is m 添 Within the above range, the battery can exhibit good kinetic performance. When m 添 When the range exceeds the upper limit of 90, the SEI film formed by the film-forming additive has a higher impedance, resulting in poorer battery cycle performance and higher battery cost; when m 添 Below the lower limit of 36, the SEI thickness formed by the film-forming additive is thin, the SEI film stability is poor, and it cannot effectively improve battery performance. Therefore, for single-component film-forming additives, the appropriate addition range of the film-forming additive can be calculated using formula (I), thereby accelerating the battery research and development process and shortening the research and development cycle.

[0041] In this application, formula (III) is named the film-forming factor. The film-forming factor can also be used to evaluate whether the amount of film-forming additive added to the battery is reasonable. Formula (III):

[0042]

[0043] When n = 1, equation (Ⅲ) can be transformed into: m 添 *ρ 负 *d 负 / ρ 添 The average particle size d of the negative electrode active material in the battery 负 Density ρ of negative electrode active material 负 Density ρ of film-forming additives 添 The mass of the film-forming additive relative to 100g of negative electrode active material is m 添 Substituting into equation (Ⅲ), the film-forming factor is calculated. When the film-forming factor is greater than or equal to 36 and less than or equal to 90, the amount of film-forming additive is considered reasonable and the battery has good kinetic performance.

[0044] When n≥2, the film-forming additive consists of multiple components. Let the density of the nth film-forming additive be ρ. j The amount of the nth film-forming additive relative to 100g of negative electrode active material is m. j The amount of film-forming additive relative to 100g of negative electrode active material is m. 添 ,in, ρ 添The unit is g / cm³ 3 m j If the unit is g, then the amount of each component added in the film-forming additive is m. j It conforms to equation (B), which is as follows:

[0045]

[0046] In equation (B), This represents the total volume of the film-forming additive, that is, the sum of the volumes of all components in the film-forming additive. This represents the volume of the film-forming additive on the surface of a single negative electrode active material. For a single negative electrode active material, its surface area is... For film-forming additives with multiple components, when the thickness of the film-forming additive coating on the surface of a single negative electrode active material is 0.07μm to 0.18μm, the film-forming additive can form a stable SEI film with low impedance and good lithium-ion transport performance.

[0047] Simplifying equation (B) yields equation (II), which is as follows:

[0048]

[0049] In formula (II), This is the film-forming factor, which refers to the average particle size d of the negative electrode active material in the battery. 负 Density ρ of negative electrode active material 负 The density ρ of each film-forming additive 添 The mass of each film-forming additive relative to 100g of negative electrode active material is m 添 Substituting the values ​​into the film-forming factor formula, we can obtain the value of the film-forming factor. Based on the value of the film-forming factor, the formulation of the film-forming additive can be adjusted to obtain a film-forming additive formulation with better performance. The specific process is as follows:

[0050] This paper provides an existing film-forming additive formulation by incorporating the film-forming additive formulation into the film-forming factor formulation, specifically by specifying the addition amount m of each component in the film-forming additive. j and the density ρ of each component j Substitute it into the film-forming factor, and use the density ρ of the negative electrode active material in the battery. 负 and the average particle size d of the negative electrode active material 负 Substituting these values ​​into the film-forming factor, we can obtain the values ​​of the film-forming factor.

[0051] Taking film-forming additives including vinylene carbonate (VC), fluoroethylene carbonate (FEC), methylene methanedisulfonate (MMDS), vinyl ethylene carbonate (VEC), propylene sulfite (PS) and diethylene sulfate (DTD) as examples, assuming that the densities of VC, FEC, MMDS, VEC, PS and DTD are ρ1, ρ2, ρ3, ρ4, ρ5 and ρ6 respectively, and the masses of the above components relative to 100 g of the negative active material are m1, m2, m3, m4, m5 and m6 respectively. Then the film-forming factor of the film-forming additive relative to the negative active material is:

[0052] ρ 负 d 负 (m1 / ρ1+m2 / ρ2+m3 / ρ3+m4 / ρ4+m5 / P5+m6 / ρ6)

[0053] When the film-forming factor exceeds the upper limit 108, the SEI film formed by the film-forming additive has a larger impedance, the battery cycle performance is poorer, and the battery cost is also higher. By reducing the addition amount of one or more components in the film-forming additive to make the film-forming factor lower than the upper limit, the impedance of the SEI film can be reduced. When the film-forming factor is lower than the lower limit 42, the SEI film formed by the film-forming additive is relatively thin, the SEI film stability is poor, and the battery performance cannot be effectively improved. By increasing the addition amount of one or more components in the film-forming additive to make the film-forming factor higher than the lower limit, the stability of the SEI film can be improved.

[0054] Therefore, for a film-forming additive with multiple components, the matching degree of the film-forming additive formula and the negative active material can be evaluated by the film-forming factor, so as to screen the film-forming additive formula, which is conducive to quickly obtaining a film-forming additive formula with good matching degree for the battery negative electrode, thereby shortening the research and development cycle of the battery and reducing the research and development cost. Similarly, for a finished battery using multiple film-forming additives, the performance of the battery can also be evaluated by calculating the film-forming factor. When the film-forming factor of the battery is within the range of 42-108, the addition amount of the film-forming additive is reasonable, and the battery also has relatively good kinetic performance.

[0055] It can be seen that the film-forming additive addition rule provided by the present application can quickly realize the screening and control of the addition amount of the film-forming additive, and the film-forming additive addition rule is suitable for a wide variety of additives and has good universality.

[0056] In some embodiments of the present application, the film-forming additive comprises one or more of an olefinic film-forming additive and a sulfur-based film-forming additive. In some embodiments of the present application, the olefinic film-forming additive comprises one or more of vinylene carbonate (VC), fluoroethylene carbonate (FEC), and vinyl ethylene carbonate (VEC). In some embodiments of the present application, the sulfur-based film-forming additive comprises one or more of propylene sulfite (PS), ethylene sulfite (ES), methanedimethanesulfonate (MMDS), and diethyl sulfite (DTD).

[0057] In some embodiments of the present application, the film-forming additive is a single component, and the density p of the film-forming additive is 添 1 g / cm 3 ~ 2 g / cm 3 In some embodiments of the present application, the film-forming additive is a single component, and the density p of the film-forming additive is 添 1.2 g / cm 3 ~ 1.5 g / cm 3 In some embodiments of the present application, the film-forming additive is a plurality of components, and the density p of each of the film-forming additives in the film-forming additive is j 1 g / cm 3 ~ 2 g / cm 3 In some embodiments of the present application, the film-forming additive is a plurality of components, and the density p of each of the film-forming additives in the film-forming additive is j 1.00 g / cm 3 ~ 1.86 g / cm 3 .

[0058] In some embodiments of the present application, the film-forming additive is a single component, for example, the film-forming additive is vinylene carbonate, and the density of the vinylene carbonate is 1.337 g / cm 3 , then the density p of the film-forming additive is 添 1.337 g / cm 3 In some embodiments of the present application, the film-forming additive is a plurality of components, for example, the film-forming additive comprises a first film-forming additive vinylene carbonate, a second film-forming additive propylene sulfite, and a third film-forming additive diethyl sulfite, wherein the density of the vinylene carbonate is 1.337 g / cm 3 , the density of the propylene sulfite is 1.05 g / cm 3 , and the density of the diethyl sulfite is 1.6045 g / cm 3 , then the density p1 of the first film-forming additive is 1.337 g / cm 3 , the density p2 of the second film-forming additive is 1.05 g / cm 3 , and the density p3 of the third film-forming additive is 1.6045 g / cm 3 .

[0059] In some embodiments of the present application, the film-forming additive comprises vinylene carbonate, which can form a solid electrolyte interface film (SEI) on the surface of the negative electrode during the initial charge-discharge of the lithium battery, thereby effectively inhibiting the reaction of solvent molecules with the negative electrode and prolonging the service life of the battery. In some embodiments of the present application, the film-forming additive contains multiple components, i.e., the number n of types of film-forming additives is greater than or equal to 2, and the film-forming additive comprises vinylene carbonate, wherein the mass percentage of vinylene carbonate in the film-forming additive is 40% to 80%, and the mass percentage of vinylene carbonate in the film-forming additive can be, but is not limited to, 40%, 50%, 60%, 70%, or 80%. When the mass percentage of vinylene carbonate in the film-forming additive is 40% to 80%, the film-forming additive can effectively improve the high-temperature stability of the SEI film, and the impedance of the SEI film will not be too large.

[0060] In the battery of the present application, the negative electrode active material comprises one or more of graphite, hard carbon, soft carbon, graphene, silicon, silicon oxide compounds, silicon metal compounds, tin, tin carbon compounds, tin oxide compounds, tin metal compounds, lithium-silicon alloy, lithium-sodium alloy, lithium-potassium alloy, lithium-aluminum alloy, lithium-tin alloy, lithium-indium alloy, lithium titanate, iron oxide, lithium titanium phosphate, and one or more of elements such as titanium, aluminum, zinc, germanium, antimony, and oxides, nitrides, sulfides, and phosphides thereof. In some embodiments of the present application, the negative electrode active material comprises one or more of graphite, hard carbon, soft carbon, graphene, silicon, and silicon oxide compounds, and the addition rules of the film-forming additive of the present application can be better applied to the above-mentioned negative electrode active materials, thereby enabling the additive to effectively protect the negative electrode active material and prolong the service life of the battery.

[0061] In some embodiments of the present application, the average particle size d 负 of the negative electrode active material is 1 μm to 50 μm, and the average particle size d 负 of the negative electrode active material can be, but is not limited to, 1 μm, 5 μm, 10 μm, 12 μm, 15 μm, 20 μm, 25 μm, 35 μm, 40 μm, or 50 μm. When the average particle size of the negative electrode active material is 1 μm to 50 μm, it is beneficial for the deintercalation of lithium ions, and the battery can have higher rate performance. Moreover, the addition rules of the film-forming additive of the present application have higher matching degree for the negative electrode active material with an average particle size of 1 μm to 50 μm, and the appropriate film-forming additive formula can be more accurately screened out.

[0062] In some embodiments of the present application, the negative electrode active material ρ 负 has a density of 1.8 g / cm 3 to 4.5 g / cm 3 . The density of the negative electrode active material ρ 负 may be, but is not limited to, 1.8 g / cm3 2 g / cm3 3 2.3 g / cm3 3 2.7 g / cm3 3 3 g / cm3 3 3.5 g / cm3 3 or 4.5 g / cm3 3 The density of the negative active material ρ 负 When the density of the negative active material is in the above range, the battery made of the negative active material can have a higher energy density and good dynamic performance.

[0063] In the embodiments of the present application, the electrolyte of the battery comprises a lithium salt, a solvent and a film-forming additive. The lithium salt in the electrolyte of the battery comprises one or more of lithium hexafluorophosphate (LiPF6), lithium perchlorate (LiClO4), lithium tetrafluoroborate (LiBF4), lithium hexafluoroarsenate (LiAsF6), lithium hexafluorosilicate (Li2SiF6), lithium chloroaluminate, lithium tetraphenylborate, lithium bisfluorosulfimide (LiFSI), lithium bis-trifluoromethylsulfonylimide (LiTFSI), lithium hexafluoroantimonate (LiSbF6), lithium bis-trifluoromethylsulfonylimide (LiTFSI), lithium bisoxalate borate (LiBOB), lithium difluoro(oxalato)borate (LiDFOB), lithium trifluoromethylsulfonate (LiCF3SO3), lithium perfluorobutylsulfonate (LiC4F9SO3), lithium bis(trifluoromethylsulfonyl)imide (Li(CF3SO2)2N), lithium bis(perfluoroethylsulfonyl)imide (Li(C2F5SO2)2N). In some embodiments of the present application, the lithium salt comprises one or more of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium hexafluoroarsenate, lithium perchlorate, lithium bisoxalate borate, lithium trifluoromethylsulfonate and lithium bis-trifluoromethylsulfonylimide. In the present application, there is no special requirement for the content of the lithium salt in the electrolyte, which can refer to the conventional amount in the art. In some embodiments of the present application, the concentration of the lithium salt in the electrolyte is 0.1 mol / L-5 mol / L, and further, the concentration of the lithium salt in the electrolyte is 1 mol / L-1.5 mol / L.

[0064] In the embodiments of the present application, the solvent in the electrolyte of the battery comprises one or more of a carbonate solvent, an ether solvent and a carboxylic acid ester solvent. The carbonate solvent can be cyclic and / or chain-shaped, and the carboxylic acid ester solvent can be straight-chain and / or branched. In some embodiments of the present application, the organic solvent comprises one or more of ethylene carbonate (EC), propylene carbonate (PC), butylene carbonate, dimethyl carbonate (DMC), methyl ethyl carbonate (EMC), diethyl carbonate (DEC), dipropyl carbonate (DPC), methyl propyl carbonate (MPC), ethyl propyl carbonate, ethyl acetate, propyl acetate, ethyl propionate, ethyl butyrate, etc., but is not limited thereto.

[0065] In the present application, the negative electrode of the battery can be any negative electrode known in the art. In some embodiments of the present application, the current collector of the negative electrode is a copper foil, the negative electrode active material comprises one or more of natural graphite, artificial graphite, hard carbon, soft carbon, lithium titanate, iron oxide, lithium titanium phosphate, titanium dioxide, silicon, silicon monoxide, aluminum, tin and antimony; the binder comprises one or more of polyacrylic acid (PAA), polyvinylidene fluoride (PVDF), carboxymethyl cellulose (CMC) and styrene butadiene rubber (SBR); and the conductive agent comprises one or more of acetylene black, ketjen black, Super-P, carbon nanotubes, carbon nanofibers, activated carbon and graphene. In the present application, the negative electrode can be prepared by any method known in the art.

[0066] In the embodiments of the present application, the positive electrode of the battery comprises a positive electrode active material capable of reversibly intercalating / deintercalating lithium ions. In the present application, the positive electrode of the battery can be any positive electrode known in the art. In some embodiments of the present application, the positive electrode active material can be, but is not limited to, one or more of lithium cobaltate (LiCoO2), lithium iron phosphate (LiFePO4), LiNi 0.33 Co 0.33 Mn 0.33 O2(NCM111), LiNi 0.4 Co 0.2 Mn 0.4 O2(NCM424), LiNi 0.5 Co 0.2 Mn 0.3 O2(NCM523), LiNi 0.6 Co 0.2 Mn 0.2 O2(NCM622), LiNi 0.8 Co 0.1 Mn 0.1 O2(NCM811).

[0067] In the embodiments of the present application, the separator of the battery can be any separator known to those skilled in the art, for example, the separator can be one or more of a polyolefin microporous membrane, polyethylene terephthalate, polyethylene felt, glass fiber felt or ultra-fine glass fiber paper.

[0068] The present application also provides an electronic device comprising the battery provided by the present application, wherein the battery supplies power to the electronic device.

[0069] The technical solutions of the present application are further described below in multiple embodiments.

[0070] Embodiment 1

[0071] Preparation of a battery:

[0072] 1) Preparation of the negative electrode of the battery:

[0073] The negative active material (artificial graphite with a particle size of 12 μm) 100 g, the conductive agent (carbon black) 1 g, and the binder (styrene-butadiene rubber, SBR) 4 g were weighed into 3 g of N-methylpyrrolidone and 110 g of water to form a negative electrode slurry. After the negative electrode slurry was stirred, coated, dried, rolled, and the tab was spot-welded, the battery negative electrode was obtained.

[0074] 2) Preparation of the battery positive electrode

[0075] The lithium iron phosphate, acetylene black, and polyvinylidene fluoride were mixed in a weight ratio of 95:3:2 and added to N-methylpyrrolidone. After stirring to form a uniform slurry, the slurry was stirred, coated, dried, rolled, and the tab was spot-welded to obtain the battery positive electrode.

[0076] 3) Preparation of the electrolyte

[0077] Based on the composition and content of the negative active material, it is derived that ρ 负 = 2.25 g / cm 3 , d 负 = 12 μm, and vinylene carbonate (VC) is used as the film-forming additive, i.e., a single component film-forming additive. The density of vinylene carbonate is 1.337 g / cm 3 . The density of vinylene carbonate, the density of the negative active material, and the average particle size are substituted into formula (I): 36 ≤ m 添 * ρ 负 * d 负 / ρ 添 ≤ 90. It is calculated that the preferred amount of vinylene carbonate added relative to 100 g of artificial graphite is 1.8 g to 4.5 g.

[0078] In an argon glove box, 12% by weight of lithium hexafluorophosphate (LiPF6) was dissolved in a solvent (the solvent was EC: DMC: DEC in a volume ratio of 1:1:1). In units of 100 g of artificial graphite, 1.8 g of vinylene carbonate was added, and the electrolyte of Example 1 was named C1.

[0079] 4) Preparation of the battery:

[0080] The battery negative electrode, the battery positive electrode, and a pp separator with a thickness of 14 μm were wound to form a battery core. After packaging, the electrolyte was injected to obtain the battery. The battery of Example 1 was named S1.

[0081] Example 2

[0082] Example 2 differs from Example 1 in that the film-forming additive of Example 2 includes vinylene carbonate (VC), fluoroethylene carbonate (FEC), and vinyl ethylene carbonate (VEC), wherein the density of VC is 1.337 g / cm 3, the density of FEC is 1.454 g / cm 3 , the density of VEC is 1.294 g / cm 3 , the mass of VC relative to 100 g of artificial graphite is 1.3 g, the mass of FEC relative to 100 g of artificial graphite is 1.3 g, and the mass of MMDS relative to 100 g of artificial graphite is 0.65 g. The total mass of the film-forming additive is 3.25 g, and the electrolyte of Example 2 is named C2.

[0083] The battery is prepared by the same method as Example 1, and the battery of Example 2 is named S2.

[0084] Example 3

[0085] Example 3 is different from Example 1 in that the film-forming additive of Example 3 includes vinylene carbonate (VC), fluoroethylene carbonate (FEC), and methylene methanedisulfonate (MMDS), and the density of MMDS is 1.851 g / cm 3 , wherein the mass of VC relative to 100 g of artificial graphite is 1.3 g, the mass of FEC relative to 100 g of artificial graphite is 0.6 g, and the mass of MMDS relative to 100 g of artificial graphite is 0.45 g. The total mass of the film-forming additive is 2.35 g. The electrolyte of Example 3 is named C3.

[0086] The battery is prepared by the same method as Example 1, and the battery of Example 3 is named S3.

[0087] Example 4

[0088] Example 4 is different from Example 1 in that the film-forming additive of Example 4 includes vinylene carbonate (VC), propylene sulfate (PS), and divinyl sulfate (DTD), and the density of PS is 1.05 g / cm 3 , the density of DTD is 1.6045 g / cm 3 , wherein the mass of VC relative to 100 g of artificial graphite is 1.8 g, the mass of PS relative to 100 g of artificial graphite is 0.9 g, and the mass of DTD relative to 100 g of artificial graphite is 0.45 g. The total mass of the film-forming additive is 3.15 g, and the electrolyte of Example 4 is named C4.

[0089] The battery is prepared by the same method as Example 1, and the battery of Example 4 is named S4.

[0090] Example 5

[0091] Example 5 is different from Example 1 in that the film-forming additive of Example 5 comprises vinylene carbonate (VC) and vinyl sulfate (DTD), wherein the mass of VC relative to 100 g of artificial graphite is 3.6 g, the mass of DTD relative to 100 g of artificial graphite is 0.9 g, the total mass of the film-forming additive is 4.5 g, and the electrolyte of Example 5 is named C5.

[0092] A battery is prepared by using the same method as Example 1, and the battery of Example 5 is named S5.

[0093] Example 6

[0094] Example 6 is different from Example 1 in that the film-forming additive of Example 6 comprises vinylene carbonate (VC) and fluoroethylene carbonate (FEC), wherein the density of VC is 1.337 g / cm 3 , the density of FEC is 1.454 g / cm 3 , the mass of VC relative to 100 g of artificial graphite is 0.5 g, and the mass of FEC relative to 100 g of artificial graphite is 2 g. The total mass of the film-forming additive is 2.5 g, and the electrolyte of Example 6 is named C6.

[0095] A battery is prepared by using the same method as Example 1, and the battery of Example 6 is named S6.

[0096] Example 7

[0097] Example 7 is different from Example 1 in that the particle size of the negative electrode active material of Example 7 is 18 μm.

[0098] Example 8

[0099] Example 8 is different from Example 1 in that the negative electrode active material of Example 8 is silicon-carbon.

[0100] In order to highlight the beneficial effects of the present application, the following comparative examples are provided.

[0101] Comparative Example 1

[0102] The film-forming additive of Comparative Example 1 is vinylene carbonate (VC), which is different from Example 1 in that in Comparative Example 1, the mass of VC relative to 100 g of artificial graphite is 1.3 g. The electrolyte of Example 5 is named C9.

[0103] A battery is prepared by using the same method as Example 1, and the battery of Comparative Example 1 is named S9.

[0104] Comparative Example 2

[0105] The film-forming additive of Comparative Example 2 is vinylene carbonate (VC), and the difference from Example 1 is that in Comparative Example 2, the mass of VC is 6 g relative to 100 g of artificial graphite. The electrolyte of Comparative Example 2 is named C10.

[0106] The battery is prepared by the same method as in Example 1, and the battery of Comparative Example 1 is named S10.

[0107] Comparative Example 3

[0108] The film-forming additive of Comparative Example 3 is vinylene carbonate (VC), fluoroethylene carbonate (FEC) and methylene methanedisulfonate (MMDS), and the difference from Example 3 is that in Comparative Example 3, the mass of VC is 2.4 g, the mass of FEC is 2 g, and the mass of MMDS is 1.8 g relative to 100 g of artificial graphite, and the total mass of the film-forming additive is 6.2 g. The electrolyte of Comparative Example 3 is named C11.

[0109] The battery is prepared by the same method as in Example 1, and the battery of Comparative Example 1 is named S11.

[0110] Comparative Example 4

[0111] The film-forming additive of Comparative Example 4 is vinylene carbonate (VC), fluoroethylene carbonate (FEC) and methylene methanedisulfonate (MMDS), and the difference from Example 3 is that in Comparative Example 4, the mass of VC is 1 g, and the mass of MMDS is 0.8 g relative to 100 g of artificial graphite, and the total mass of the film-forming additive is 1.8 g. The electrolyte of Comparative Example 4 is named C12.

[0112] The battery is prepared by the same method as in Example 1, and the battery of Comparative Example 1 is named S12.

[0113] Effect Example

[0114] To provide strong support for the beneficial effects brought by the technical solutions of the present application, the following tests are provided:

[0115] 1. Battery charge-discharge performance test

[0116] Each experimental soft-pack battery S1-S12 is charged at room temperature with a current of 0.6 A to 3.8 V, and then discharged with a current of 0.6 A to 2.0 V, and the charge capacity and discharge capacity of the battery are recorded, and the charge-discharge efficiency (%) = charge capacity / discharge capacity x 100%. The test results are shown in Table 1.

[0117] Table 1 Performance parameter table of batteries S1-S12

[0118]

[0119]

[0120] As can be seen from Table 1, the additive addition amount in the examples meets the addition rules of the present application, and the obtained battery has a higher discharge efficiency. The film-forming additive addition amount in Comparative Example 1 is too small, so the battery performance improvement effect is limited. The film-forming additive addition amount in Comparative Example 2 is relatively large, and the discharge efficiency of the battery is relatively higher than that of Comparative Example 1, but lower than that of Example 1, that is, too much addition will also reduce the charge and discharge efficiency.

[0121] 2. Battery DC internal resistance test

[0122] The soft package batteries S1-S12 were discharged at room temperature at 0.33C (0.6A) to 2.0V, and charged at 0.33C to 50% SOC (charge capacity 0.9A). 1.5C (2.7A) constant current discharge for 30s, record the voltage before and after discharge, calculate the discharge DCIR (mΩ) = (voltage before discharge - voltage after discharge) / discharge current * 1000. The test results are shown in Table 2.

[0123] Table 2 DC internal resistance test table of batteries S1-S12

[0124] Battery number Discharge DCIR / mΩ S1 52.7 S2 55.6 S3 47.4 S4 54.0 S5 58.3 S6 52.0 S7 54.3 S8 60.0 S9 65.3 S10 83.0 S11 80.3 S12 64.0

[0125] As can be seen from Table 2, in the batteries of Examples 1-8, the additive addition amount is moderate, and the DC internal resistance of the battery is small. The film-forming additive addition amount in Comparative Examples 1 and 4 is too small, and the electrolyte undergoes a side reaction at the negative electrode, the side reaction product adheres to the surface of the negative electrode, hinders the deintercalation of lithium ions, and causes the increase of the battery internal resistance. The film-forming additive addition amount in Comparative Examples 2 and 4 is too large, resulting in too large thickness of the SEI film, too high battery internal resistance, large battery heat loss, and easy heating, which reduces the safety performance.

[0126] 3. Battery high temperature cycle test

[0127] The soft package batteries S1-S12 were charged at 60°C environment at 1C rate (about 1.8A) to 3.8V, and then discharged at 1.8A to 2.0V, the first charge capacity and discharge capacity were recorded; after 500 times of repeated charge and discharge cycles, the discharge capacity of the 500th cycle was recorded, and the capacity retention rate (%) after cycling = discharge capacity after 500 cycles / first discharge capacity x 100%. The test results are shown in Table 3.

[0128] Table 3 High temperature performance table of batteries S1-S12

[0129]

[0130] As can be seen from Table 3, in the batteries of Examples 1-8, the amount of the additive is moderate, and the capacity retention of the batteries is high. In the battery of Example 6, the content of vinylene carbonate in the film-forming additive is low, so the cycle performance of the battery is slightly worse than that of the batteries of other examples, but is still better than that of the batteries of Comparative Examples 1-4. In the batteries of Comparative Examples 1-4, the amount of the film-forming additive is too much or too little, so the capacity retention of the batteries under high-temperature conditions is low, which is not conducive to the safety of the batteries.

[0131] As can be seen from the experiments of Tables 1-3, when the batteries are prepared by using the film-forming additive provided by the application according to the addition rule, the batteries can have good cycle performance and high-temperature resistance, thereby prolonging the service life of the batteries and promoting the application of the batteries.

[0132] The above describes the preferred embodiments of the application, but should not be construed as limiting the scope of the application. It should be pointed out that, for those skilled in the art, without departing from the principles of the application, a number of improvements and refinements can be made, which are also considered to be within the protection scope of the application.

Claims

1. A battery comprising a positive electrode, a negative electrode, an electrolyte, and a separator located between the positive electrode and the negative electrode, wherein the negative electrode comprises a negative electrode active material, and the electrolyte comprises a lithium salt, a solvent, and a film-forming additive, characterized in that, When there is only one type of film-forming additive, the amount of the film-forming additive added conforms to formula (I): 36 ≤ m 添 *ρ 负 *d 负 / ρ 添 ≤ 90 Formula (I); When the number of film-forming additives n≥2, the amount of film-forming additives added conforms to formula (II). Where, m 添 The mass of the film-forming additive corresponding to 100g of the negative electrode active material in the battery is expressed in grams; ρ 负 The density of the negative electrode active material is expressed in g / cm³. 3 ;d 负 The average particle size of the negative electrode active material is expressed in μm; ρ 添 The density of the film-forming additive is expressed in g / cm³. 3 m j ρ represents the mass of each film-forming additive corresponding to 100g of the negative electrode active material in the battery. j This represents the density of each film-forming additive.

2. The battery as described in claim 1, characterized in that, The film-forming additives include one or more of olefin-based film-forming additives and sulfur-based film-forming additives.

3. The battery as described in claim 2, characterized in that, The olefinic film-forming additives include one or more of vinylene carbonate, fluoroethylene carbonate, and ethylene ethylene carbonate; the sulfur-based film-forming additives include one or more of propylene sulfite, methylene disulfonate, and vinyl sulfate.

4. The battery as described in claim 1, characterized in that, The film-forming additive includes vinylene carbonate.

5. The battery as described in claim 4, characterized in that, When n≥2, the vinylene carbonate accounts for 40% to 80% of the mass percentage of the film-forming additive.

6. The battery as claimed in claim 1, characterized in that, In the formula (I), the ρ 添 1g / cm 3 ~2g / cm 3 In the aforementioned formula (II), the ρ j 1g / cm 3 ~2g / cm 3 .

7. The battery as claimed in claim 1, characterized in that, The negative electrode active material includes graphite, hard carbon, soft carbon, graphene, silicon, silicon oxide, silicon metal compound, tin, tin carbon compound, tin oxide, tin metal compound, lithium silicon alloy, lithium sodium alloy, lithium potassium alloy, lithium aluminum alloy, lithium tin alloy, lithium indium alloy, lithium titanate, iron oxide, lithium titanium phosphate, and one or more of the elements titanium, aluminum, zinc, germanium, and antimony, as well as their oxides, nitrides, sulfides, and phosphides.

8. The battery as claimed in claim 1, characterized in that, The average particle size d of the negative electrode active material 负 The range is from 1μm to 50μm.

9. The battery according to any one of claims 1-8, characterized in that, The negative electrode active material ρ 负 Its density is 1.8 g / cm³. 3 ~4.5g / cm 3 .

10. An electronic device, characterized in that, The electronic device includes a battery as described in any one of claims 1-9.

11. A method for predicting battery performance, characterized in that, The battery includes a positive electrode, a negative electrode, an electrolyte, and a separator located between the positive electrode and the negative electrode. The negative electrode includes a negative electrode active material, and the electrolyte includes a lithium salt, a solvent, and a film-forming additive. The battery performance prediction method includes: Battery performance is predicted based on film-forming factors, which are shown in Formula (III): Where n is the number of film-forming additives, ρ 负 The density of the negative electrode active material is expressed in g / cm³. 3 ;d 负 The average particle size of the negative electrode active material is expressed in μm; m j ρ represents the mass of each film-forming additive corresponding to 100g of negative electrode active material in the battery. j The density of each film-forming additive; When n=1 and the value of the film-forming factor is 36-90, it indicates that the amount of film-forming additive added is reasonable and the battery has good kinetic performance. When n≥2 and the value of the film-forming factor is 42~108, it indicates that the amount of film-forming additive added is reasonable and the battery has good kinetic performance.

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