Battery and electronic device

Abstract

The application relates to a battery and an electronic device. The battery comprises a positive electrode sheet, a negative electrode sheet, a diaphragm and an electrolyte. The positive electrode sheet comprises a positive electrode current collector and a positive electrode active material layer arranged on at least one surface of the positive electrode current collector. The positive electrode active material layer comprises a positive electrode active material, a conductive agent, a binder and a positive electrode additive. The positive electrode additive comprises a first lithium salt. The electrolyte comprises an organic solvent, an electrolyte lithium salt and an electrolyte additive. The electrolyte lithium salt or the electrolyte additive comprises a second lithium salt. The second lithium salt is the same as or different from the first lithium salt. The scheme provided by the application can make the battery present excellent high and low temperature performance.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of batteries, in particular to a battery and an electronic device. BACKGROUND

[0002] Lithium ion batteries are widely used in 3C digital, power tools, aerospace, energy storage, electric vehicles and other fields due to their high specific energy, no memory effect, long cycle life and other advantages. The rapid development of electronic information technology and consumer products has put forward higher requirements for high voltage and high energy density of lithium ion batteries.

[0003] In related technologies, ternary positive electrode materials are widely used in portable electronic devices such as mobile phones and notebook computers, electric vehicles, and large energy storage devices due to their high energy density, environmental friendliness, and long cycle life. However, as the limiting voltage of ternary positive electrode materials continues to increase (especially 4.3V+), the oxidation of electrolyte by ternary positive electrode materials is strengthened, and the high-temperature performance of the battery deteriorates seriously, and the long cycle life cannot be guaranteed. In particular, during the long-term cycle charging and discharging process at high voltage, the volume of the positive electrode material will expand and cause serious cracking, and the solvent in the electrolyte will enter the interior of the positive electrode material, causing problems such as oxidation of the electrolyte to produce gas, which ultimately causes serious capacity decay. The deterioration of electrochemical performance in a high-temperature environment will further exacerbate the problem. In a low-temperature working environment, the viscosity of the electrolyte increases, resulting in a decrease in the rate of lithium ion migration and an increase in the interfacial impedance of the battery, which reduces the conductivity of the battery and ultimately leads to a decrease in the low-temperature discharge performance of the battery.

[0004] Therefore, it is urgent to develop a lithium ion battery that takes into account excellent high and low temperature performance. SUMMARY

[0005] To solve or partially solve the problems in the related art, the present application provides a battery and an electronic device that can improve the high and low temperature performance of the battery.

[0006] The first aspect of the present application provides a battery, wherein the battery comprises a positive electrode sheet, a negative electrode sheet, a separator and an electrolyte, the positive electrode sheet comprises a positive electrode current collector and a positive electrode active material layer arranged on at least one surface of the positive electrode current collector, the positive electrode active material layer comprises a positive electrode active material, a conductive agent, a binder and a positive electrode additive, the positive electrode additive comprises a first lithium salt;

[0007] The electrolyte comprises an organic solvent, an electrolyte lithium salt and an electrolyte additive, the electrolyte lithium salt or the electrolyte additive comprises a second lithium salt, and the second lithium salt is the same as or different from the first lithium salt.

[0008] The battery as described above, wherein the second lithium salt is the same as the first lithium salt;

[0009] The electrolyte lithium salt comprises a second lithium salt, and the second lithium salt comprises at least one of lithium hexafluorophosphate; and / or,

[0010] The electrolyte lithium salt comprises a second lithium salt, and the second lithium salt comprises at least one of lithium difluorophosphate, lithium fluoride, lithium bisoxalate borate, lithium tetrafluoroborate, lithium difluorobisoxalate borate, lithium difluorobisoxalate phosphate, lithium tetrafluorobisoxalate phosphate, lithium carbonate, lithium nitrate, lithium phytate, lithium 4,5-dicyano-2-trifluoromethylimidazole, lithium hexafluoroarsenate, lithium perchlorate, lithium trifluorosulfonate, lithium bistrifluoromethylsulfonylimide, lithium tris(trifluoromethylsulfonyl)methide, lithium bisfluorosulfonylimide.

[0011] The battery as described above, wherein the second lithium salt comprises at least one of lithium difluorophosphate, lithium bisoxalate borate, lithium tetrafluoroborate, lithium difluorobisoxalate borate, lithium difluorobisoxalate phosphate, lithium tetrafluorobisoxalate phosphate, lithium 4,5-dicyano-2-trifluoromethylimidazole, lithium bistrifluoromethylsulfonylimide, lithium tris(trifluoromethylsulfonyl)methide.

[0012] The battery as described above, wherein the mass percentage content of the first lithium salt in the positive electrode active material layer is 0.01% to 1%; and / or,

[0013] The mass percentage content of the second lithium salt in the electrolyte is 0.01% to 1%.

[0014] The battery as described above, wherein the electrolyte additive further comprises a ring-annulus additive.

[0015] The battery as described above, wherein the ring-annulus additive comprises at least one of the compounds shown in Structural Formula 1-1 to Structural Formula 1-6:

[0016]

[0017]

[0018] The mass percentage content of the ring-annulus additive in the electrolyte is 0.1% to 4%.

[0019] The battery as described above, wherein the first lithium salt, the second lithium salt, and the ring-annulus additive satisfy the following relationship:

[0020] 0.01≤M b / M a1 ≤400;

[0021] And / or, 0.005≤M b / (M a1 +M a2 )≤200

[0022] The mass percentage content of the ring-annulus additive in the electrolyte is M b The mass percentage content of the first lithium salt in the positive electrode active material layer is M a1 The mass percentage content of the second lithium salt in the electrolyte is M a2 .

[0023] The battery as described above, wherein the first lithium salt, the second lithium salt and the ring-annulus additive satisfy the following relationship:

[0024] 5≤M b / M a1 ≤60;

[0025] And / or, 0.22≤M b / (M a1 +M a2 )≤12.

[0026] The battery as described above, wherein 0.01≤M a1 ≤1; and / or, 0.01≤M a2 ≤1; and / or, 0.1≤M b ≤4.

[0027] The second aspect of the present application provides an electronic device, wherein the electronic device comprises the battery as described above.

[0028] The technical scheme provided in the application can have the following beneficial effects: when the first lithium salt is added to the positive electrode sheet, the first lithium salt can decompose to generate lithium-containing compounds on the surface of the positive electrode active material layer, which can participate in the construction of the CEI film, effectively improving the thermal stability, toughness and lithium ion conductivity of the CEI film, thereby reducing the side reaction between the positive electrode active material and the electrolyte, avoiding the dissolution and structural damage of the positive electrode active material, preventing the oxidation of the electrolyte to produce gas, and thus improving the cycle performance, storage performance and thermal safety performance of the battery at high temperature, and the rich lithium fluoride in the CEI film can improve the rapid transport of lithium ions on the surface of the positive electrode and improve the low-temperature performance of the battery; when the second lithium salt is added to the electrolyte, the second lithium salt not only participates in the construction of the CEI film, but also participates in the construction of the SEI film, thereby simultaneously improving the thermal stability, toughness and lithium ion conductivity of the CEI film and the SEI film of the battery, reducing the probability of side reactions between the electrolyte and the positive and negative electrode active materials, avoiding the decomposition of the electrolyte to produce gas and the structural change of the positive and negative electrode active materials, improving the transport rate and migration rate of lithium ions, and thus improving the high and low temperature performance of the battery; the application separately adds lithium salts to the positive electrode active material and the electrolyte, which can solve the problem of low solubility of lithium salts in the electrolyte, realize high content use, and more greatly exert the performance of lithium salts, and the lithium salt in the positive electrode active material can act as a sustained-release agent and slowly dissolve into the electrolyte during the cycle process to supplement the consumption of lithium salt during the cycle process, thereby improving the cycle performance of the battery; in addition, when the first lithium salt and the second lithium salt are the same, the use amount of the lithium salt can be further expanded, and the negative effect of the lithium salt on the battery impedance can be reduced.

[0029] It should be understood that the general description above and the following detailed description are merely exemplary and explanatory, and are not limiting to the application. DETAILED DESCRIPTION

[0030] The terms used in the present application are merely for the purpose of describing specific embodiments, and are not intended to limit the present application. The singular forms "a", "an" and "the" used in the present application and the appended claims are also intended to include the plural forms, unless the context clearly indicates otherwise. It should also be understood that the term "and / or" used herein means and includes any or all possible combinations of one or more associated listed items.

[0031] It should be understood that, although the terms "first", "second", "third", etc. can be used herein to describe various information, the information should not be limited to these terms. These terms are only used to distinguish one type of information from another type of information. For example, the first information can also be referred to as the second information, and similarly, the second information can also be referred to as the first information without departing from the scope of the present application. Therefore, the features defined with "first", "second" can explicitly or implicitly include one or more of the features. In the description of the present application, the meaning of "a plurality of" is two or more, unless otherwise specifically limited.

[0032] In the related art, in a high-voltage environment, the oxidation of the positive active material to the electrolyte is strengthened, the high-temperature performance of the battery deteriorates seriously, and the long cycle life cannot be guaranteed. Especially in a long-term cycle charging and discharging process at high voltage, the volume of the positive material will expand and cause serious cracking, the solvent in the electrolyte enters the inside of the positive material, causing problems such as oxidation of the electrolyte to produce gas, and ultimately causing serious capacity attenuation. The deterioration of the electrochemical performance in a high-temperature environment will further intensify. In a low-temperature working environment, the viscosity of the electrolyte increases, resulting in a slow lithium ion migration rate and an increase in the battery interface impedance, which reduces the conductivity of the battery, and ultimately leads to a decrease in the low-temperature discharge performance of the battery.

[0033] To solve the above problems, the present application provides a battery, which comprises a positive electrode sheet, a negative electrode sheet, a separator and an electrolyte. The positive electrode sheet comprises a positive electrode current collector and a positive active material layer arranged on at least one surface of the positive electrode current collector. The positive active material layer comprises a positive active material, a conductive agent, a binder and a positive electrode additive. The positive electrode additive comprises a first lithium salt.

[0034] The electrolyte comprises an organic solvent, an electrolyte lithium salt and an electrolyte additive. The electrolyte lithium salt or the electrolyte additive comprises a second lithium salt. The second lithium salt is the same as or different from the first lithium salt.

[0035] In the present application, the selection of the positive electrode current collector is not limited. For example, the positive electrode current collector can be an aluminum foil. The selection of the positive active material is not limited in the present application, and can be selected according to actual needs. For example, a lithium transition metal oxide can be used as the positive active material. The conductive agent and the binder in the positive active material layer of the present application can be selected from conventional materials in the art. The positive electrode additive of the present application comprises a first lithium salt.

[0036] The composition of the negative electrode sheet is not limited in the present application, and can be selected according to actual needs. For example, the negative electrode sheet comprises a negative electrode current collector and a negative active material layer arranged on at least one surface of the negative electrode current collector. The negative active material layer comprises a negative active material, a conductive agent and a binder. The separator of the present application can be selected from conventional materials in the art.

[0037] The electrolyte of the present application comprises an organic solvent, an electrolyte lithium salt and an electrolyte additive. The present application does not limit the selection of the organic solvent, which can be selected according to actual needs, as long as the electrolyte lithium salt and the electrolyte additive can be fully dissolved and have high stability. The electrolyte lithium salt or the electrolyte additive of the present application comprises a second lithium salt, which can be the same as or different from the first lithium salt.

[0038] According to the above-mentioned scheme provided by the present application, after the positive electrode sheet and the electrolyte are applied to the lithium ion battery, the lithium ion battery has excellent high-temperature cycle performance, high-temperature storage performance and low-temperature discharge performance. This is because when the first lithium salt is added to the positive electrode sheet, the first lithium salt can decompose to produce lithium-containing compounds on the surface of the positive electrode active material layer. These substances can participate in the construction of the CEI film, effectively improving the thermal stability, toughness and lithium conductivity of the CEI film, thereby reducing the side reaction between the positive electrode active material and the electrolyte, avoiding the dissolution and structural damage of the positive electrode active material, preventing the oxidation of the electrolyte to produce gas, and further improving the cycle performance and storage performance of the battery at high temperature and the thermal safety performance. At the same time, the rich lithium fluoride in the CEI film can improve the rapid transport of lithium ions on the positive electrode surface and improve the low-temperature performance of the battery; when the electrolyte adds the second lithium salt, the second lithium salt not only participates in the construction of the CEI film, but also participates in the construction of the SEI film, thereby simultaneously improving the thermal stability, toughness and lithium conductivity of the CEI film and the SEI film of the battery, reducing the probability of side reactions between the electrolyte and the positive and negative electrode active materials, avoiding the decomposition of the electrolyte to produce gas and the structural change of the positive and negative electrode active materials, improving the transport rate and migration rate of lithium ions, and further improving the high and low temperature performance of the battery; the present application separately adds lithium salts to the positive electrode active material and the electrolyte, which can solve the problem of low solubility of lithium salts in the electrolyte, realize high content use, and more greatly exert the performance of lithium salts. Moreover, the lithium salt in the positive electrode active material can act as a sustained-release agent and slowly dissolve into the electrolyte during the cycle process to supplement the consumption of lithium salt during the cycle process, thereby improving the cycle performance of the battery; in addition, when the first lithium salt and the second lithium salt are the same, the use amount of lithium salt can be further expanded, and the negative impact of lithium salt on the impedance of the battery can be reduced.

[0039] In a specific embodiment, the second lithium salt is the same as the first lithium salt, and the electrolyte lithium salt comprises the second lithium salt. The second lithium salt comprises lithium hexafluorophosphate.

[0040] In one embodiment, the electrolyte additive comprises a second lithium salt, and the second lithium salt comprises at least one of lithium difluorophosphate, lithium fluoride, lithium bis(oxalato)borate (LiBOB), lithium tetrafluoroborate (LiBF4), lithium difluorobis(oxalato)borate (LiODFB), lithium difluorobis(oxalato)phosphate (LiODFP), lithium tetrafluorobis(oxalato)phosphate (LiTFOP), lithium carbonate, lithium nitrate, lithium phytate, lithium 4,5-dicyano-2-trifluoromethylimidazole (LiTDI), lithium hexafluoroarsenate, lithium perchlorate, lithium trifluorosulfonyl, lithium bis(trifluoromethylsulfonyl)imide (LiTFSI), lithium tris(trifluoromethylsulfonyl)methide, lithium bisfluorosulfonylimide (LiFSI). When the second lithium salt is selected from the above lithium salts, the lithium salt can participate in the construction of the CEI film on the surface of the positive electrode active material layer, and also participate in the construction of the SEI film, thereby simultaneously improving the thermal stability, toughness and lithium ion conductivity of the CEI film and SEI film of the battery, reducing the probability of side reactions between the electrolyte and the positive and negative electrode active materials, improving the transmission rate and migration rate of lithium ions, and thereby improving the high and low temperature performance of the battery.

[0041] In one preferred embodiment, the second lithium salt comprises at least one of lithium difluorophosphate, lithium bis(oxalato)borate, lithium tetrafluoroborate, lithium difluorobis(oxalato)borate, lithium difluorobis(oxalato)phosphate, lithium tetrafluorobis(oxalato)phosphate, lithium 4,5-dicyano-2-trifluoromethylimidazole, lithium bis(trifluoromethylsulfonyl)imide, lithium tris(trifluoromethylsulfonyl)methide. When the second lithium salt is within the above preferred range, the second lithium salt can be better dissolved in the electrolyte, avoiding precipitation or precipitation of the second lithium salt in the electrolyte, and fully exerting the electrochemical effect of the second lithium salt.

[0042] In one embodiment, the mass percentage content of the first lithium salt in the positive electrode active material layer is 0.01% to 1%, for example, the mass percentage content of the first lithium salt in the positive electrode active material layer can be 0.01%, 0.05%, 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9% or 1%, etc. When the mass percentage content of the first lithium salt is within the above range, sufficient lithium-containing compounds and other substances generated by the decomposition of the first lithium salt can effectively improve the thermal stability, toughness and lithium ion conductivity of the CEI film, and avoid insufficient improvement of the thermal stability, toughness and lithium ion conductivity of the CEI film due to insufficient lithium-containing compounds and other substances, thereby further improving the high and low temperature performance of the battery.

[0043] In an embodiment, the second lithium salt has a mass percentage of 0.01% to 1% in the electrolyte. For example, the second lithium salt has a mass percentage of 0.01%, 0.05%, 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, or 1%, etc. When the mass percentage of the second lithium salt is within the above range, the second lithium salt can be completely dissolved in the electrolyte, participate in the construction of the SEI film and the CEI film, further improve the stability and lithium-ion-conducting performance of the SEI film and the CEI film, and make the high and low temperature performance of the battery higher.

[0044] In an embodiment, the electrolyte additive further comprises a bicyclic compound. The bicyclic compound of the present application refers to a compound having two or more ring structures, which are connected by chemical bonds, and can be aromatic rings (such as benzene rings) or other heterocyclic rings. When the electrolyte is added with the bicyclic compound, the bicyclic compound can synergize with the lithium salt to construct a CEI film and a SEI film with high stability, thereby better stabilizing the structure of the positive active material, reducing the dissolution of transition metal ions, avoiding the side reaction between the positive active material and the electrolyte, reducing the decomposition of the electrolyte, and thereby greatly improving the high-temperature cycle performance, high-temperature storage performance, and thermal safety performance of the lithium-ion battery. At the same time, the lithium salt and the bicyclic compound synergize to reduce the negative effect of the bicyclic compound alone on the battery impedance, thereby improving the transport rate and migration rate of lithium ions in the battery, reducing the impedance of the battery, and making the battery have both high and low temperature performance.

[0045] In an embodiment, the bicyclic compound comprises at least one of the compounds shown in Structural Formula 1-1 to Structural Formula 1-6:

[0046]

[0047]

[0048] The bicyclic compound of the present application comprises a five-membered cyclic carbonate group and / or a five-membered cyclic sulfate group. The sulfate group or carbonate group in the bicyclic compound can participate in the formation of an interface film and improve the stability of the interface film. When the bicyclic compound is selected from the above-mentioned compounds, the bicyclic compound and the lithium salt can better synergize to generate a CEI film and a SEI film with higher stability, thereby better stabilizing the structure of the positive active material, reducing the decomposition of the electrolyte, making the high-temperature cycle performance, high-temperature storage performance, and thermal safety performance of the lithium-ion battery higher, and making the transport rate and migration rate of lithium ions in the battery higher and the low-temperature performance of the battery higher.

[0049] In an embodiment, the mass percentage of the dicyclophane additive in the electrolyte is 0.1% to 4%, for example, the mass percentage of the dicyclophane additive in the electrolyte can be 0.1%, 0.2%, 0.5%, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, or 4%, etc. When the mass percentage of the dicyclophane additive is within the above range, the dicyclophane additive can better improve the stability of the CEI film and the SEI film, improve the stability of the positive and negative active materials, avoid structural changes of the positive and negative active materials and decomposition of the electrolyte on the surface of the positive and negative active materials, thereby better improving the high-temperature performance of the battery, and at the same time, avoiding excessive dicyclophane additive leading to excessive impedance of the battery, thereby balancing the high and low temperature performance of the battery.

[0050] In an embodiment, the first lithium salt, the second lithium salt, and the dicyclophane additive satisfy the following relationship:

[0051] 0.01≤M b / M a1 ≤400;

[0052] and / or, 0.005≤M b / (M a1 +M a2 )≤200

[0053] wherein the mass percentage of the dicyclophane additive in the electrolyte is M b %, the mass percentage of the first lithium salt in the positive active material layer is M a1 %, and the mass percentage of the second lithium salt in the electrolyte is M a2 %.

[0054] It can be understood that the above formulas of M b / M a1 , M b / (M a1 +M a2 ) at least satisfy one, or both. M a1 is the mass percentage of the first lithium salt in the positive active material layer, M a2 is the mass percentage of the second lithium salt in the electrolyte, and M b is the mass percentage of the dicyclophane additive in the electrolyte, therefore, M a1 +M a2 refers to the mass percentage of the lithium salt in the entire battery. Therefore, based on experience and experimental findings, the physical meaning of M b / M a1 is the matching degree of the dicyclophane additive in the electrolyte of the battery and the lithium salt in the positive plate; M b / (M a1 +M a2The physical meaning of M b / M a1 , M b / (M a1 +M a2 ) is the matching degree of the bicyclic additive in the electrolyte of the battery and the lithium salt in the whole battery. When M b / M a1 <0.01 and / or M b / (M a1 +M a2 ) <0.005, the ratio of the bicyclic additive to the lithium salt is small, which leads to insufficient improvement of the thermal stability and toughness of the SEI film and the CEI film, resulting in poor improvement of the high-temperature performance and thermal safety performance of the battery, and the structural change of the positive active material also degrades the energy density of the battery to some extent. If M b / M a1 > 400 and / or M a1 / (M a2 +M b ) > 200, the ratio of the bicyclic additive to the lithium salt is too large, which leads to poor lithium ion conductivity of the formed SEI film and CEI film, resulting in low migration rate of lithium ions, degrading the impedance of the battery, and leading to poor low-temperature performance of the battery.

[0055] In a specific embodiment, the first lithium salt, the second lithium salt and the bicyclic additive satisfy the following relationship:

[0056] 5≤M a1 / M b ≤60;

[0057] and / or, 0.22≤M a1 / (M a2 +M b )≤12.

[0058] When M a1 / M b , M a1 / (M a2When the mass percentage content of the first lithium salt in the positive electrode active material layer, the mass percentage content of the second lithium salt in the electrolyte, and the mass percentage content of the bicyclic additive in the electrolyte are within the above ranges, the lithium salt and the bicyclic additive can have a better synergistic effect, the stability, toughness, and lithium-ion-conducting performance of the SEI film and the CEI film generated are better, the stability of the positive and negative electrode active materials is higher, and the transmission rate and migration rate of lithium ions are improved, so that the high and low temperature performance of the battery is better.

[0059] In one specific embodiment, 0.01≤M a1 ≤1, for example, M a1 is 0.01, 0.05, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, or 1, etc.; and / or, 0.01≤M a2 ≤1, for example, M a2 is 0.01, 0.05, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, or 1, etc.; and / or, 0.1≤M b ≤4, for example, M b is 0.1, 0.5, 1, 1.5, 2, 2.5, 3, 3.5, or 4, etc. When the mass percentage content of the first lithium salt in the positive electrode active material layer, the mass percentage content of the second lithium salt in the electrolyte, and the mass percentage content of the bicyclic additive in the electrolyte are within the above ranges, the lithium salt and the bicyclic additive can have a better synergistic effect, the stability, toughness, and lithium-ion-conducting performance of the SEI film and the CEI film generated are better, the stability of the positive and negative electrode active materials is higher, the probability of side reactions between the electrolyte and the positive and negative electrode active materials is reduced, the transmission rate and migration rate of lithium ions are improved, and thus the high and low temperature performance of the battery is further improved.

[0060] In one specific embodiment, the electrolyte further includes a fluorocarbon acid ester, the fluorocarbon acid ester includes at least one of fluoroethylene carbonate, difluoroethylene carbonate (DFEC), and fluoroethylene carbonate, and the mass percentage content of the fluorocarbon acid ester in the electrolyte is 0.3% to 15%. Preferably, the fluorocarbon acid ester includes fluoroethylene carbonate. When the selection and mass percentage content of the fluorocarbon acid ester are within the above ranges, the fluorocarbon acid ester can synergize with the lithium salt and the bicyclic additive to further improve the stability and lithium-ion-conducting performance of the SEI film, so that the negative electrode active material and the electrolyte can be better protected, side reactions of the negative electrode active material and the electrolyte are avoided, and the high and low temperature performance of the battery is better.

[0061] In an embodiment, the electrolyte includes a lithium salt electrolyte, the lithium salt electrolyte includes an organic lithium salt and / or an inorganic lithium salt. Preferably, the lithium salt electrolyte is selected from at least one of the compounds containing fluorine element and lithium element. More preferably, the lithium salt electrolyte is selected from at least one of hexafluorophosphate, hexafluoroarsenate, perchlorate, lithium triflate, lithium bistrifluoromethylsulfonylimide, lithium tris(trifluoromethylsulfonyl)methide, lithium bisfluorosulfonylimide. The molar concentration of the lithium salt electrolyte in the electrolyte is 0.5M-1.5M, for example, 0.5M, 0.6M, 0.7M, 0.8M, 0.9M, 1M, 1.1M, 1.2M, 1.3M, 1.4M or 1.5M, etc. When the selection of the lithium salt electrolyte and the molar concentration are within the above range, the conductivity and stability of the electrolyte can be further improved, thereby further improving the high and low temperature performance of the battery. If the molar concentration of the lithium salt electrolyte is too low, the conductivity of the electrolyte is low, which leads to the deterioration of the cycle performance of the battery; if the molar concentration of the lithium salt electrolyte is too high, the viscosity of the electrolyte is too large, the migration rate of lithium ions is reduced, and the rate performance of the battery is reduced. Preferably, the molar concentration of the lithium salt electrolyte in the electrolyte is 0.8M-1.3M.

[0062] In an embodiment, the electrolyte includes an organic solvent, the organic solvent includes at least two of ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, methyl ethyl carbonate, methyl formate, ethyl formate, ethyl propionate, propyl propionate, methyl butyrate, tetrahydrofuran. When the organic solvent of the electrolyte is selected from the above organic solvents, the viscosity of the electrolyte is lower and the ionic conductivity is higher, which is conducive to improving the migration rate of lithium ions, and the above organic solvents can improve the stability of the electrolyte, avoid the decomposition reaction of the electrolyte, thereby further improving the high and low temperature performance of the battery.

[0063] In an embodiment, the positive electrode active material layer further includes a positive electrode active material, the positive electrode active material includes at least one of lithium cobaltate, lithium nickel manganese cobalt ternary material, lithium iron phosphate, lithium manganate. When the positive electrode active material is selected from the above compounds, the positive electrode active material can fully exert its performance, thereby improving the electrochemical performance of the battery.

[0064] In an embodiment, the battery further includes a negative electrode sheet, the negative electrode sheet includes a negative electrode current collector and a negative electrode active material layer arranged on the surface of the negative electrode current collector, the negative electrode active material layer includes a negative electrode active material, a conductive agent and a binder. The negative electrode active material includes at least one of natural graphite, artificial graphite, mesophase carbon microbeads (MCMB for short), hard carbon, soft carbon, silicon, silicon-carbon composite, Li-Sn alloy, Li-Sn-O alloy, Sn, SnO, SnO2, spinel structure lithiumized TiO2-Li4Ti5O 12 12, Li-Al alloy.

[0065] The negative current collector of the embodiments of the present application is not particularly limited as long as the purpose of the present application can be achieved, and for example, can be a copper foil, a copper alloy foil, a nickel foil, a stainless steel foil, a titanium foil, a foamed nickel, a foamed copper, or a composite current collector, etc.

[0066] The selection of the conductive agent and the binder in the negative active material layer of the embodiments of the present application can be a conventional material in the art.

[0067] In a specific embodiment, the battery further includes a separator, and the embodiments of the present application do not have a particular limitation on the material and shape of the separator as long as the effect of the present application is not significantly impaired. The material of the resin or glass fiber separator can include, but is not limited to, polyolefin, aromatic polyamide, polytetrafluoroethylene, polyether sulfone, etc., and can be set as needed.

[0068] The second aspect of the present application provides an electronic device including the above-mentioned battery. The electronic device has advantages corresponding to the above-mentioned battery, and will not be described again.

[0069] The electronic device of the embodiments of the present application can be a conventional electronic device in the art, and for example, the above-mentioned electronic device can include a mobile device (such as a mobile phone, a notebook computer, etc.), an electric vehicle (such as a pure electric vehicle, a hybrid electric vehicle, a plug-in hybrid electric vehicle, an electric bicycle, an electric scooter, an electric golf cart, an electric truck, etc.), an electric train, a ship and a satellite, an energy storage system, etc., and is not particularly limited.

[0070] In the following, the present application will be further described in detail through specific embodiments.

[0071] Embodiment 1

[0072] 1. Preparation of the positive electrode sheet

[0073] The positive active material NCM622 and the first lithium salt (the type and amount of the additive are shown in Table 1), the conductive agent CNT, and the binder polyvinylidene fluoride were mixed in a weight ratio of 97- M a1 : M a1 : 1.5: 1.5 in an N-methylpyrrolidone solvent to form a uniform positive electrode slurry. The positive electrode slurry was coated on the positive electrode current collector aluminum foil, dried, cold-pressed, and a positive electrode sheet was obtained.

[0074] 2. Preparation of the negative electrode sheet

[0075] The negative active material graphite, the conductive agent acetylene black, the binder styrene-butadiene rubber, and the thickening agent sodium carboxymethyl cellulose were mixed in a mass ratio of 95:2:2:1 in an appropriate amount of deionized water solvent to form a uniform negative electrode slurry. The negative electrode slurry was coated on the negative electrode current collector copper foil, dried, cold-pressed, and a negative electrode sheet was obtained.

[0076] 3. Preparation of electrolyte

[0077] Vinyl carbonate (EC), propylene carbonate (PC), diethyl carbonate (DEC) were mixed in a mass ratio of 2:1:7 to form a mixed solvent, 2% fluoroethylene carbonate (FEC) was added, lithium hexafluorophosphate (LiPF6) was added and mixed uniformly to obtain a mixed solution with a molar concentration of LiPF6 of 1.1M; then based on the total mass of the electrolyte, a second lithium salt and a ring-annular additive (the type and amount of the additive are shown in Table 1) were added to obtain the electrolyte of each example and comparative example.

[0078] 4. Preparation of lithium ion battery

[0079] The above positive electrode sheet, separator and negative electrode sheet were wound to obtain a bare cell. The bare cell was placed in a shell-punched aluminum plastic film to complete the top side sealing. After high-temperature baking, the prepared electrolyte was injected, and then the cell was completed after processes such as standing, formation, capacity distribution and detection.

[0080] The preparation method of the battery provided in Examples 2-38 and Comparative Examples 1-14 was basically the same as that of Example 1, and the specific parameters are shown in Table 1.

[0081] Table 1

[0082]

[0083]

[0084]

[0085]

[0086]

[0087] Test Example

[0088] Battery performance test:

[0089] 45℃ cycle test: the battery was placed in an environment of 45±2℃, and the capacity retention rate of the battery after 700 cycles was calculated according to the standard charge-discharge cycle with a cycle rate of 1C and a charge voltage of 3.0-4.3V. The calculation formula is as follows: the capacity retention rate of the 700th cycle (%) = (the discharge capacity of the 700th cycle) / (the discharge capacity of the first cycle) * 100%, and the results are recorded in Table 2.

[0090] 85℃ storage test: the finished battery was charged to 4.3V at room temperature with 0.5C current, and then was placed in 85℃ environment for 12 hours. The thickness expansion rate (%) = (thickness after storage - thickness before storage) / (thickness before cycling) * 100%. After recovery to room temperature, the battery was discharged to 3.0V with 0.5C current, and the discharge capacity was recorded. The capacity retention rate (%) = (discharge capacity of the first cycle after storage) / (capacity before storage) * 100%.

[0091] -20℃ low temperature discharge test: the battery was charged to 3.0V at 25℃ with 1.0C current, and then was placed at 25℃ for 10min. The battery was discharged to 3.0V at 0.2C at 25℃, and the process was repeated for 3 weeks. The discharge capacity at 0.2C in the third week was recorded as the initial capacity. The battery was charged to 3.0V at 25℃ with 1.0C current, and then was placed at -20℃ for 4h. The battery was discharged to 3.0V at 0.2C, and the discharge capacity was recorded. The calculation formula was as follows: -20℃ discharge capacity retention rate (%) = (discharge capacity) / (initial capacity) * 100%. The results were recorded in Table 2.

[0092] 130℃ thermal shock test: test method: the battery was placed in a 25±2℃ environment, and was subjected to standard charge-discharge cycles at a cycle rate of 1C. After being fully charged, the battery was placed in an oven, and the temperature of the oven was increased to 130℃ at a rate of 5±2℃ / min, and then was maintained for 1h before being stopped. Whether the battery caught fire or exploded was recorded. YES represented that the battery caught fire or exploded, and NO represented that the battery did not catch fire or explode. The results were recorded in Table 2.

[0093] Table 2

[0094]

[0095]

[0096]

[0097] From Table 2, it can be seen that, according to the comparison of Comparative Example 1 and Comparative Example 3, and Comparative Example 2 and Comparative Example 4, the addition of lithium salt in the positive electrode active material layer can effectively improve the high and low temperature performance of the battery.

[0098] According to the comparison of Comparative Example 3 and Example 1, it can be seen that the simultaneous addition of lithium salt in the positive electrode active material layer and the electrolyte can effectively improve the high and low temperature performance of the battery.

[0099] According to the comparison of Example 2 and Examples 1-6, it can be seen that when the positive electrode active material layer comprises lithium salt and the electrolyte comprises lithium salt and a fused ring additive, the lithium salt and the fused ring additive can synergistically act, so that the high and low temperature performance of the battery is better.

[0100] According to the comparison of Examples 2-11, when the lithium salt is selected from the above compounds, the high and low temperature performance of the battery can be improved.

[0101] According to the comparison of Examples 2, 12-16 and Comparative Examples 7, 8, as the mass percentage content of the lithium salt in the positive active material layer increases, the high and low temperature performance of the battery improves, and when the mass percentage content of the lithium salt reaches 0.1%, the high and low temperature performance of the battery reaches the highest, and then the high and low temperature performance of the battery decreases as the content of the lithium salt increases, while the thermal safety performance of the battery improves as the content of the lithium salt increases. In addition, when the mass percentage content of the lithium salt in the positive active material layer is in the range of 0.01%-1%, the high and low temperature performance of the battery is better balanced.

[0102] According to the comparison of Examples 2, 17-21 and Comparative Examples 9, 10, as the mass percentage content of the lithium salt in the electrolyte increases, the high and low temperature performance of the battery improves, and the thermal safety performance of the battery improves. When the mass percentage content of the lithium salt in the electrolyte is in the range of 0.01%-1%, the high and low temperature performance of the battery is better balanced.

[0103] According to the comparison of Examples 2, 22-26, when the lithium salt is selected from the compounds represented by Formula 1-1-Formula 1-6, the high and low temperature performance of the battery can be better improved.

[0104] According to the comparison of Examples 2, 27-32 and Comparative Examples 11, 12, as the mass percentage content of the bicyclic ring additive in the electrolyte increases, the high temperature performance of the battery improves, while the low temperature performance and the thermal safety performance of the battery decrease. When the mass percentage content of the bicyclic ring additive in the electrolyte is in the range of 0.1%-4%, the high and low temperature performance of the battery is better.

[0105] According to the comparison of Examples 2-38 and Comparative Examples 13, 14, when 0.01≤M b / M a1 ≤400 and / or 0.005≤M b / (M a1 +M a2 )≤200, the battery can have excellent high and low temperature performance; according to the comparison of Examples 2, 11-14 and Example 15, the comparison of Examples 2, 20-21 and Examples 17-19, the comparison of Examples 2, 28-32 and Example 31, the comparison of Examples 36 and Examples 34-35, Examples 37-38, when 5≤M b / M a1 ≤60 and / or 0.22≤M b / (M a1 +M a2When the value of the formula (1) is less than or equal to 12, the lithium salt and the bicyclic additive can better synergize, so that the high and low temperature performance of the battery is higher.

[0106] Embodiments of the application have been described above, with the understanding that these descriptions are exemplary only, and are not intended to be exhaustive or to limit the scope of the embodiments disclosed. Many modifications and variations are possible in light of the above teachings. It is contemplated that the use of the terms "including," "comprising," "having," "containing," or "including" and variations thereof, are intended to be equivalent to the term "consisting of" or "consisting of." The use of the term "about" in relation to a geographic location, is intended to be equivalent to the term "approximately." The use of the term "about" in relation to a geographic location, is intended to be equivalent to the term "approximately." The use of the term "about" in relation to a geographic location, is intended to be equivalent to the term "approximately." The use of the term "about" in relation to a geographic location, is intended to be equivalent to the term "approximately." The use of the term "about" in relation to a geographic location, is intended to be equivalent to the term "approximately." The use of the term "about" in relation to a geographic location, is intended to be equivalent to the term "approximately." The use of the term "about" in relation to a geographic location, is intended to be equivalent to the term "approximately." The use of the term "about" in relation to a geographic

Claims

1. A battery, characterized by, The battery comprises a positive electrode sheet, a negative electrode sheet, a separator and an electrolyte, the positive electrode sheet comprises a positive electrode current collector and a positive electrode active material layer arranged on at least one surface of the positive electrode current collector, the positive electrode active material layer comprises a positive electrode active material, a conductive agent, a binder and a positive electrode additive, the positive electrode additive comprises a first lithium salt; The electrolyte comprises an organic solvent, an electrolyte lithium salt and an electrolyte additive, the electrolyte additive comprises a second lithium salt, the second lithium salt is the same as or different from the first lithium salt; the first lithium salt and the second lithium salt are both selected from any one of lithium difluorophosphate, lithium fluoride, lithium bisoxalate borate, lithium tetrafluoroborate, lithium difluorobisoxalate borate, lithium difluorobisoxalate phosphate, lithium tetrafluorobisoxalate phosphate, lithium carbonate, lithium nitrate, lithium phytate, 4,5-dicyano-2-trifluoromethyl imidazole lithium, lithium hexafluoroarsenate, lithium perchlorate, lithium trifluorosulfonyl, lithium bistrifluoromethylsulfonylimide, lithium tris(trifluoromethylsulfonyl)methide, lithium difluorosulfonylimide; the mass percentage content of the first lithium salt in the positive electrode active material layer is 0.01% to 1%; the mass percentage content of the second lithium salt in the electrolyte is 0.01% to 1%; the electrolyte additive further comprises a fused ring type additive, the fused ring type additive comprises at least one of compounds shown in structural formula 1-1 to structural formula 1-6: Formula 1-1 Formula 1-2 Formula 1-3 Formula 1-4 Formula 1-5 Formula 1-6 The mass percentage content of the fused ring type additive in the electrolyte is 0.1% to 4%.

2. The battery of claim 1, wherein, The second lithium salt is the same as the first lithium salt; The electrolyte lithium salt comprises lithium hexafluorophosphate.

3. The battery of claim 1, wherein, The first lithium salt and the second lithium salt are both selected from any one of lithium difluorophosphate, lithium bisoxalate borate, lithium tetrafluoroborate, lithium difluorobisoxalate borate, lithium difluorobisoxalate phosphate, lithium tetrafluorobisoxalate phosphate, 4,5-dicyano-2-trifluoromethyl imidazole lithium, lithium bistrifluoromethylsulfonylimide, lithium tris(trifluoromethylsulfonyl)methide.

4. The battery of claim 1, wherein, The first lithium salt, the second lithium salt and the fused ring type additive satisfy the following relationship formula: 0.01 < M b / M a1 ≤ 400; and / or, 0.005≤M b / (M a1 +M a2 )≤200 The mass percentage content of the ring joint additive in the electrolyte is M b The mass percentage content of the first lithium salt in the positive electrode active material layer is M a1 The mass percentage content of the second lithium salt in the electrolyte is M a2 .

5. The battery of claim 4, wherein, The first lithium salt, the second lithium salt and the fused ring type additive satisfy the following relationship formula: 5≤M b / M a1 ≤60; and / or, 0.22≤M b / (M a1 +M a2 )≤12.

6. The battery according to claim 4 or 5, characterized in that, 0.01≤M a1 ≤1 ; and / or, 0.01≤M a2 ≤1 ; and / or, 0.1≤M b ≤4.

7. An electronic device, comprising: The battery comprises a positive electrode sheet, a negative electrode sheet, a separator and an electrolyte, the positive electrode sheet comprises a positive electrode current collector and a positive electrode active material layer arranged on at least one surface of the positive electrode current collector, the positive electrode active material layer comprises a positive electrode active material, a conductive agent, a binder and a positive electrode additive, the positive electrode additive comprises a first lithium salt;

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