Secondary battery and its manufacturing method, battery module, battery pack, and power consumption device

Abstract

The present application provides a secondary battery and a manufacturing method thereof. The secondary battery includes a positive electrode sheet and an electrolyte, the positive electrode sheet includes a positive electrode current collector and a positive electrode film layer provided on at least one surface of the positive electrode current collector, the porosity of the positive electrode film layer is P, the electrolyte includes a drainage additive, the mass percentage of the drainage additive in the electrolyte relative to the total mass of the electrolyte is a, and the secondary battery satisfies 0.2≦(a*100) / P≦3.5. The secondary battery of the present application improves the porosity to achieve both high energy density and good kinetics, and has improved initial direct current resistance (DCR) and high temperature cycle performance. The present application further provides a battery module, a battery pack, and a power consumption device including the secondary battery of the present application.

Description

[Technical field]

[0001] The present application relates to the technical field of lithium batteries, and in particular to a secondary battery and a manufacturing method thereof, as well as a battery module, a battery pack and a power consuming device including the secondary battery. [Background technology]

[0002] In recent years, as the application scope of lithium ion batteries becomes wider and wider, lithium ion batteries are widely used in energy storage power systems such as hydroelectric, thermal, wind and solar power stations, as well as in many fields such as electric tools, electric bicycles, electric motorcycles, electric vehicles, military equipment, aerospace, etc. As lithium ion batteries have been developed very much, higher requirements are being placed on their energy density, cycle performance and safety performance.

[0003] When designing a high-performance secondary battery, the energy density of the battery can be increased by adopting a thicker coating amount and a higher compression density. With the increase in the thickness or compression density of the coating layer, there is a situation where the porosity gradually decreases from the current collector to the surface of the active material, which causes problems such as low electrolyte infiltration and absorption efficiency, slow lithium ion migration speed, and large internal resistance of the battery, and finally causes problems such as an increase in the initial direct current resistance (DCR) of the battery and poor cycle performance. By adding a pore-forming agent to the preparation of the positive electrode slurry, the porosity of the electrode sheet can be adjusted, the infiltration of the electrolyte in the electrode sheet can be effectively improved, and the migration speed of the lithium ions can be improved. However, since the positive electrode sheet with high porosity is prone to water absorption, it is inevitable that unintended water will be introduced during the manufacture of the battery. In addition, under high temperature conditions, the electrolyte of the lithium ion battery also generates water autocatalytically. In the secondary battery, these unintended waters cause a series of side reactions to rapidly deteriorate the battery performance.

[0004] Therefore, it is necessary to take certain measures to improve the porosity to achieve both high energy density and good kinetics, and to reduce unintentional water in the battery to improve the effect of moisture on the initial direct current resistance (DCR) and high-temperature cycle performance of lithium-ion batteries. Summary of the Invention

[0005] The present application has been made in view of the above problems, and an object of the present application is to provide a secondary battery having improved initial direct current resistance (DCR) and high-temperature cycle performance by solving the problem of improving the porosity to achieve both high energy density and good dynamics while reducing the adverse effect of water in the battery on battery performance, and to provide a manufacturing method for the secondary battery, as well as to provide a battery module, a battery pack, and a power consuming device including the secondary battery of the present application.

[0006] In order to achieve the above object, a first aspect of the present application is a secondary battery including a positive electrode sheet and an electrolyte solution, The positive electrode sheet includes a positive electrode current collector and a positive electrode film layer provided on at least one surface of the positive electrode current collector, the positive electrode film layer having a porosity of P; The electrolyte solution includes a drainage additive, and the mass percentage of the drainage additive in the electrolyte solution is a relative to the total mass of the electrolyte solution; and The secondary battery has a temperature of 0.2≦(a * To provide a secondary battery that satisfies the requirement of 100) / P≦3.5.

[0007] As a result, compared to the prior art, the secondary battery according to the present application has an improved porosity, thereby achieving both high energy density and good kinetics, as well as improved initial direct current resistance (DCR) and high-temperature cycle performance.

[0008] In any embodiment, the secondary battery has a capacitance of 0.4≦(a * 100) / P≦3.3, selectable, 1.0≦(a * 100) / P≦1.7.

[0009] By satisfying the above conditions, the porosity of the secondary battery can be improved to achieve both high energy density and good kinetics, while the initial direct current resistance (DCR) and / or high temperature cycle performance of the secondary battery can be further improved.

[0010] In an optional embodiment, the water drainage additive is at least one selected from a compound of structural formula I, a compound of structural formula II, and an isocyanate compound. [ka]

[0011] In the formula, R1, R2, R3, R4, R5 and R6 are each independently a silyl group having a halogen-substituted or unsubstituted alkyl group or a halogen-substituted or unsubstituted alkyl group, at least one of R1, R2 and R3 is a silyl group having a halogen-substituted or unsubstituted alkyl group, and at least one of R4, R5 and R6 is a silyl group having a halogen-substituted or unsubstituted alkyl group.

[0012] Optionally, R1, R2, R3, R4, R5 and R6 are each independently a silyl group having an unsubstituted C1-C6 alkyl group or an unsubstituted C1-C6 alkyl group, and at least one of R1, R2 and R3 is a silyl group having an unsubstituted alkyl group, and at least one of R4, R5 and R6 is a silyl group having an unsubstituted alkyl group.

[0013] Further optionally, R1, R2, R3, R4, R5 and R6 are each independently a silyl group having a methyl group, an ethyl group, a propyl group or a butyl group, or a methyl group, an ethyl group, a propyl group or a butyl group, and at least one of R1, R2 and R3 is a silyl group having a methyl group, an ethyl group, a propyl group or a butyl group, and at least one of R4, R5 and R6 is a silyl group having a methyl group, an ethyl group, a propyl group or a butyl group.

[0014] and X is phosphorus or boron.

[0015] At least one water-draining additive selected from the group consisting of the compound of formula I, the compound of formula II, and the isocyanate-based compound can effectively reduce the adverse effect of water on the battery performance, so that the secondary battery has improved initial direct current resistance (DCR) and high-temperature cycle performance.

[0016] In any embodiment, the mass percentage a of the drainage additive in the electrolyte is 0.1%-1%, and optionally the mass percentage a of the drainage additive in the electrolyte is 0.3%-0.7%, based on the total mass of the electrolyte. When the mass percentage of the drainage additive in the electrolyte satisfies the above range, it can effectively reduce the adverse effect of water on battery performance, and improve the initial direct current resistance (DCR) and high temperature cycle performance of the secondary battery.

[0017] In any embodiment, the water draining additive is at least one selected from tris(trimethylsilyl)phosphate, tris(trimethylsilyl)phosphite, diethyltrimethylsilylphosphite, tris(trimethylsilyl)borate, hexamethylene diisocyanate, trimethylsilyl isocyanate, tolylene diisocyanate, dicyclohexylmethane diisocyanate and isophorone diisocyanate. By selecting the water draining additive, the initial direct current resistance (DCR) and high temperature cycle performance of the secondary battery can be further improved.

[0018] In an optional embodiment, the porosity P of the positive electrode membrane layer is 20%-70%, and optionally, the porosity P of the positive electrode membrane layer is 30%-50%. When the porosity of the positive electrode membrane layer satisfies the above range, it is favorable for promoting the infiltration of the electrolyte and promoting the transport of lithium ions inside the positive electrode sheet, and the secondary battery has a low initial direct current resistance (DCR).

[0019] In any embodiment, the electrolyte contains a film-forming additive, the mass percentage of the film-forming additive in the electrolyte relative to the total mass of the electrolyte is b, and the secondary battery satisfies 0.03≦a / b≦0.7. By adding the film-forming additive to the electrolyte, the high-temperature cycle performance of the secondary battery can be improved, and the amount of the drainage additive and the film-forming additive in the electrolyte satisfies the above condition, so that the initial direct current resistance (DCR) and the high-temperature cycle performance of the secondary battery can be improved.

[0020] In an optional embodiment, the secondary battery satisfies 0.05≦a / b≦0.5, and optionally satisfies 0.15≦a / b≦0.35. By satisfying the above condition, the adverse effect of water on the battery performance can be further reduced, and the initial direct current resistance (DCR) and high-temperature cycle performance of the secondary battery can be further improved.

[0021] In any embodiment, the film-forming additive is at least one selected from adiponitrile, lithium difluorooxalate borate, vinyl ethylene carbonate, lithium difluorophosphate, lithium tetrafluoroborate, vinylene carbonate, 1,3-propane sultone, and lithium trifluoromethanesulfonate. By selecting the film-forming additive, a protective film (SEI film) is formed on the surface of the positive electrode sheet and the negative electrode sheet, and deterioration of battery performance due to temperature rise is reduced, so that the initial direct current resistance (DCR) and high-temperature cycle performance of the secondary battery can be further improved.

[0022] In any embodiment, the electrolyte comprises a lithium salt, the lithium salt being at least one selected from lithium hexafluorophosphate, lithium difluorooxalate borate and lithium bis(fluorosulfonyl)imide, and the mass percentage of the lithium salt in the electrolyte is 5%-18% relative to the total mass of the electrolyte. By selecting the lithium salt and the content of the lithium salt in the electrolyte, the initial direct current resistance (DCR) and high-temperature cycle performance of the secondary battery can be improved.

[0023] A second aspect of the present application is a method for producing a secondary battery according to the first aspect of the present application, the method including producing a positive electrode sheet, The present invention provides a method for producing a secondary battery, wherein the production of the positive electrode sheet includes forming a positive electrode film layer on at least one surface of a positive electrode current collector, and the positive electrode film layer is formed by applying a positive electrode slurry containing a positive electrode active material and a pore-forming agent to one surface of the positive electrode current collector.

[0024] Therefore, when a high coating amount is ensured, adding a pore-forming agent to the production of the positive electrode sheet is advantageous in improving the porosity of the positive electrode film layer, promoting the infiltration of the electrolyte, and promoting the transport of lithium ions inside the positive electrode sheet, so that the secondary battery has a low initial direct current resistance (DCR). At the same time, adding a water-draining additive to the electrolyte effectively reduces the adverse effects of unintended water (water caused by increasing the porosity of the positive electrode sheet using a pore-forming agent and water generated by the lithium-ion battery at high temperatures), and improves the initial direct current resistance (DCR) and high-temperature cycle performance of the lithium-ion battery.

[0025] In an optional embodiment, the pore-forming agent is at least one selected from oxalic acid, ammonium bicarbonate, ammonium carbonate, urea, ammonium chloride, and ammonium fluoride, and the mass ratio of the pore-forming agent to the positive electrode active material is 1:100-8:100. By selecting the above pore-forming agent, well-distributed pore paths can be formed in the positive electrode sheet, and the amount of the pore-forming agent and the positive electrode active material satisfies the above ratio, which ensures effective infiltration and absorption of the electrolyte, effectively improves the lithium ion migration rate, and makes the secondary battery have good initial direct current resistance (DCR).

[0026] A third aspect of the present application provides a battery module including the secondary battery according to the first aspect of the present application or a secondary battery manufactured by the method according to the second aspect of the present application.

[0027] A fourth aspect of the present application provides a battery pack including the battery module according to the third aspect of the present application.

[0028] A fifth aspect of the present application provides a power consuming device including at least one selected from a secondary battery according to the first aspect of the present application, or a secondary battery manufactured by the method according to the second aspect of the present application, a battery module according to the third aspect of the present application, or a battery pack according to the fourth aspect of the present application.

[0029] The battery module, battery pack and power consuming device of the present application include a secondary battery according to the first aspect of the present application and a secondary battery manufactured by the method according to the second aspect of the present application, and therefore have at least the same advantages as the secondary battery. [Brief description of the drawings]

[0030] [Figure 1] FIG. 1 is a schematic diagram of a secondary battery according to one embodiment of the present application. [Diagram 2] FIG. 2 is an exploded view of the secondary battery shown in FIG. 1 according to one embodiment of the present application. [Diagram 3] FIG. 1 is a schematic diagram of a battery module according to one embodiment of the present application. [Figure 4] FIG. 1 is a schematic diagram of a battery pack according to one embodiment of the present application. [Diagram 5] FIG. 5 is an exploded view of the battery pack shown in FIG. 4 according to one embodiment of the present application. [Figure 6] 1 is a schematic diagram of a power consuming device using a secondary battery as a power source according to one embodiment of the present application. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0031] Hereinafter, with reference to the drawings as appropriate, detailed descriptions will be given of the embodiments specifically disclosing the secondary battery and its manufacturing method, the battery module, the battery pack, and the power consumption device of the present application. However, unnecessary detailed descriptions may be omitted. For example, detailed descriptions of known matters and duplicate descriptions of substantially identical configurations may be omitted. This is to avoid unnecessary redundancy in the following description and to facilitate understanding by those skilled in the art. Note that the accompanying drawings and the following description are provided to enable those skilled in the art to fully understand the present application, and are not intended to limit the subject matter described in the claims.

[0032] The "ranges" disclosed in this application are defined in the form of lower and upper limits, where a given range is defined by selecting one lower limit and one upper limit, and the selected lower and upper limits define the boundaries of the particular range. Such defined ranges may be inclusive or exclusive of the end values, and may be arbitrarily combined, i.e., any lower limit may be combined with any upper limit to form a range. For example, when ranges of 60-120 and 80-110 are recited for a particular parameter, it is understood that ranges of 60-110 and 80-120 are also contemplated. Also, when minimum range values ​​1 and 2 and maximum range values ​​3, 4 and 5 are recited, ranges of 1-3, 1-4, 1-5, 2-3, 2-4 and 2-5 may all be contemplated. In this application, unless otherwise stated, the numerical range "a-b" is represented by the abbreviation of any combination of real numbers between a and b, where a and b are both real numbers. For example, the numerical range "0-5" indicates that all real numbers between "0-5" are listed herein, with "0-5" being an abbreviation for combinations of these numerical values. Furthermore, expressing a parameter as an integer greater than or equal to 2 (≧2) is equivalent to disclosing that the parameter is, for example, the integers 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0033] Unless otherwise stated, all the embodiments and optional embodiments in the present application can be combined with each other to form a new technical solution.

[0034] Unless otherwise stated, all technical features and optional technical features in this application can be combined with each other to form a new technical solution.

[0035] Unless otherwise stated, all steps in the present application may be performed in sequence or randomly, but are preferably performed in sequence. For example, the method includes steps (a) and (b) and may include steps (a) and (b) performed in sequence, or may include steps (b) and (a) performed in sequence. For example, when it is stated that the method may further include step (c), it means that step (c) may be added to the method in any order. For example, the method may include steps (a), (b) and (c), or may include steps (a), (c) and (b), or may include steps (c), (a) and (b), etc.

[0036] Unless otherwise specified, the terms "comprise" and "include" used in this application mean open-ended and may also be closed-ended. For example, the terms "comprise" and "include" can mean "comprise" or "include" other components not listed, or "comprise" or "include" only the listed components.

[0037] Unless otherwise stated, in this application, the term "or" is inclusive. For example, the phrase "A or B" means "A, B, or both A and B." More specifically, any of the following conditions are met: A is true (or exists) and B is false (or does not exist), A is false (or does not exist) and B is true (or exists), or both A and B are true (or exist).

[0038] When designing a high-performance secondary battery, the energy density of the battery can be increased by using a thicker coating amount and a higher compression density. With the increase in thickness or compression density of the coating layer, there is a situation where the porosity gradually decreases from the current collector to the surface of the active material, causing problems such as low electrolyte infiltration and absorption efficiency, slow lithium ion migration speed, and high internal resistance of the battery, and ultimately poor rate performance and cycle performance of the battery. By adding a pore-forming agent during the preparation of the positive electrode slurry, the porosity of the electrode sheet can be adjusted, the infiltration of the electrolyte in the electrode sheet can be effectively improved, and the migration speed of lithium ions can be improved, thereby greatly improving problems such as poor rate performance and poor cycle performance caused by an increase in the compression density or thickness of the positive electrode sheet. However, since a high-porosity positive electrode sheet is prone to water absorption, it is inevitable that unintended water will be introduced during the manufacture of the battery. In addition, the electrolyte of the secondary battery will generate water autocatalytically even under high temperature conditions. In the secondary battery, these unintended waters will cause a series of side reactions to rapidly deteriorate the battery performance. Therefore, it is necessary to take certain measures to improve the initial direct current resistance (DCR) and high-temperature cycle performance of lithium-ion batteries by improving the porosity of the secondary battery to ensure both high energy density and good kinetics, and by reducing unintended water in the battery (water caused by increasing the porosity of the positive electrode sheet using a pore-forming agent and water generated by the secondary battery at high temperatures).

[0039] In response to the above problem, the present application provides a secondary battery including a positive electrode sheet and an electrolyte solution, The positive electrode sheet includes a positive electrode current collector and a positive electrode film layer provided on at least one surface of the positive electrode current collector, the positive electrode film layer having a porosity of P; The electrolyte solution includes a drainage additive, and the mass percentage of the drainage additive in the electrolyte solution is a relative to the total mass of the electrolyte solution; and The secondary battery has a temperature of 0.2≦(a * To provide a secondary battery that satisfies the requirement of 100) / P≦3.5.

[0040] The applicant unexpectedly found that when a thicker coating amount and a higher compression density are adopted to improve the energy density of the battery, the porosity of the positive electrode film layer can be adjusted to effectively improve the infiltration of the electrolyte into the electrode sheet, improve the lithium ion migration speed, and make the secondary battery have a lower initial direct current resistance (DCR); at the same time, the water draining additive in the electrolyte can effectively reduce the adverse effects of unintended water in the battery; and when the porosity of the positive electrode film layer in the secondary battery and the amount of the water draining additive in the electrolyte satisfy the above relationship, a secondary battery that achieves both high energy density, improved initial direct current resistance (DCR), and high temperature cycle performance can be obtained.

[0041] In some embodiments, the secondary battery has a temperature coefficient of 0.4≦(a * 100) / P≦3.3, selectable, 1.0≦(a * 100) / P≦1.7 is satisfied. If the amount of the water draining additive is too small and the porosity of the electrode sheet is too large, excessive moisture is easily introduced into the battery, the water draining effect of the electrolyte is not significant, and the high-temperature cycle of the secondary battery is deteriorated. If the amount of the water draining additive is too large, the porosity of the electrode sheet is too small, and the film formation resistance of the water draining additive is large, the initial direct current resistance (DCR) of the secondary battery is deteriorated. By satisfying the above conditions, it is possible to further improve the initial direct current resistance (DCR) and / or high-temperature cycle performance of the secondary battery while ensuring a high energy density of the secondary battery.

[0042] In some embodiments, the water drainage additive is at least one selected from a compound of formula I, a compound of formula II, and an isocyanate-based compound. [ka]

[0043] In the formula, R1, R2, R3, R4, R5 and R6 are each independently a silyl group having a halogen-substituted or unsubstituted alkyl group or a halogen-substituted or unsubstituted alkyl group, at least one of R1, R2 and R3 is a silyl group having a halogen-substituted or unsubstituted alkyl group, and at least one of R4, R5 and R6 is a silyl group having a halogen-substituted or unsubstituted alkyl group.

[0044] Optionally, R1, R2, R3, R4, R5 and R6 are each independently a silyl group having an unsubstituted C1-C6 alkyl group or an unsubstituted C1-C6 alkyl group, and at least one of R1, R2 and R3 is a silyl group having an unsubstituted alkyl group, and at least one of R4, R5 and R6 is a silyl group having an unsubstituted alkyl group.

[0045] Further optionally, R1, R2, R3, R4, R5 and R6 are each independently a silyl group having a methyl group, an ethyl group, a propyl group or a butyl group, or a methyl group, an ethyl group, a propyl group or a butyl group, and at least one of R1, R2 and R3 is a silyl group having a methyl group, an ethyl group, a propyl group or a butyl group, and at least one of R4, R5 and R6 is a silyl group having a methyl group, an ethyl group, a propyl group or a butyl group.

[0046] and X is phosphorus or boron. At least one water-draining additive selected from the group consisting of the compound of formula I, the compound of formula II, and the isocyanate-based compound can effectively reduce the adverse effect of water on the battery performance, so that the secondary battery has improved initial direct current resistance (DCR) and high-temperature cycle performance.

[0047] In some embodiments, the mass percentage a of the drainage additive in the electrolyte is 0.1%-1%, and optionally the mass percentage a of the drainage additive in the electrolyte is 0.3%-0.7%, based on the total mass of the electrolyte. When the mass percentage of the drainage additive in the electrolyte is within the above range, it can effectively reduce the adverse effect of water on battery performance, and improve the initial direct current resistance (DCR) and high temperature cycle performance of the secondary battery.

[0048] In some embodiments, the water draining additive is at least one selected from tris(trimethylsilyl)phosphate, tris(trimethylsilyl)phosphite, diethyltrimethylsilylphosphite, tris(trimethylsilyl)borate, hexamethylene diisocyanate, trimethylsilyl isocyanate, tolylene diisocyanate, dicyclohexylmethane diisocyanate and isophorone diisocyanate. The water draining additive can combine with water in the secondary battery to prevent destruction of the electrode interface by water, improve the stability of the electrolyte, and improve the performance of the secondary battery. By selecting the above water draining additive, the initial direct current resistance (DCR) and high temperature cycle performance of the secondary battery can be further improved.

[0049] In some embodiments, the porosity P of the positive electrode membrane layer is 20%-70%, and optionally, the porosity P of the positive electrode membrane layer is 30%-50%. When the porosity of the positive electrode membrane layer meets the above range, it is favorable for promoting the infiltration of the electrolyte and promoting the lithium ion transport inside the positive electrode sheet, so that the secondary battery has a low initial direct current resistance (DCR). In this application, the porosity P of the positive electrode membrane layer can be measured according to GB / T 24586-2009, and the porosity in this application is expressed in %.

[0050] In some embodiments, the electrolyte solution includes a film-forming additive, the mass percentage of the film-forming additive in the electrolyte solution is b relative to the total mass of the electrolyte solution, and the secondary battery satisfies 0.03≦a / b≦0.7. The film-forming additive in the electrolyte solution has a good film-forming effect, and can form a solid electrolyte interfacial film (SEI film) by electrochemical reaction on the negative electrode surface during the initial charge and discharge of the lithium battery, effectively inhibit the insertion of solvent molecules, and improve the high-temperature cycle performance of the secondary battery. The amount of the water-draining additive and the film-forming additive in the electrolyte solution satisfies the above conditions, so that the initial direct current resistance (DCR) and the high-temperature cycle performance of the secondary battery can be improved. In the present application, the ratio of the mass percentage a of the water-draining additive in the electrolyte solution to the mass percentage b of the film-forming additive (i.e., a / b) is the ratio of the water-draining additive added to the film-forming additive added when preparing the electrolyte solution. In the present application, the mass percentage a of the water-draining additive in the electrolyte solution and the mass percentage b of the film-forming additive are both shown in %.

[0051] In some embodiments, the secondary battery satisfies 0.05≦a / b≦0.5, and optionally satisfies 0.15≦a / b≦0.35. By satisfying the above conditions, the adverse effect of water on the battery performance can be further reduced, and the initial direct current resistance (DCR) and high-temperature cycle performance of the secondary battery can be further improved.

[0052] In some embodiments, the film-forming additive is at least one selected from adiponitrile, lithium difluorooxalate borate, vinylethylene carbonate, lithium difluorophosphate, lithium tetrafluoroborate, vinylene carbonate, 1,3-propane sultone, and lithium trifluoromethanesulfonate. By selecting the film-forming additive, a protective film (SEI film) is formed on the surface of the positive electrode sheet and the negative electrode sheet, the deterioration of battery performance due to temperature rise is reduced, and the initial direct current resistance (DCR) and high-temperature cycle property of the secondary battery can be further improved.

[0053] In some embodiments, the electrolyte contains a lithium salt, the lithium salt being at least one selected from lithium hexafluorophosphate, lithium difluorooxalate borate, and lithium bis(fluorosulfonyl)imide, and the mass percentage of the lithium salt in the electrolyte is 5%-18% relative to the total mass of the electrolyte. The decomposition of lithium salts such as lithium hexafluorophosphate (LiPF6) is favorable for the formation of a solid electrolyte interface film (SEI film), and can effectively improve the electrode passivation layer, prevent water erosion, reduce side reactions, and extend the battery life. If the content of lithium salt is too high, the viscosity of the electrolyte is too high, making it difficult to infiltrate into the voids, which is unfavorable for the transport of lithium ions, while if the content of substances generated by decomposition (e.g., fluorophosphate and lithium fluoride) is too high, it will deteriorate the initial direct current resistance (DCR) of the secondary battery. If the content of the lithium salt is too low, the components forming the SEI film (e.g., fluorophosphate and lithium fluoride) affect the high-temperature cycle performance of the secondary battery. By selecting the above lithium salt and the content of the lithium salt in the electrolyte, the initial direct current resistance (DCR) and high-temperature cycle performance of the secondary battery can be improved.

[0054] In some embodiments, the electrolyte contains an organic solvent, and the organic solvent is at least one selected from dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, ethylene carbonate, propylene carbonate, fluoroethylene carbonate, and sulfolane. The organic solvent in the electrolyte is favorable for dissociation of lithium salt, improving the conductivity of the electrolyte, and some organic solvent components, such as ethylene carbonate and sulfolane, also participate in the formation of the SEI film to avoid the destruction of the SEI film by water, and improve the stability of the interface.

[0055] A second aspect of the present application is a method for producing a secondary battery according to the first aspect of the present application, the method including producing a positive electrode sheet, The present invention provides a method for producing a secondary battery, wherein the production of the positive electrode sheet includes forming a positive electrode film layer on at least one surface of a positive electrode current collector, and the positive electrode film layer is formed by applying a positive electrode slurry containing a positive electrode active material and a pore-forming agent to one surface of the positive electrode current collector.

[0056] When ensuring a high coating amount, adding a pore-forming agent in the production of the positive electrode sheet is advantageous in improving the porosity of the positive electrode film layer, promoting the infiltration of the electrolyte, and promoting the transport of lithium ions inside the positive electrode sheet, so that the secondary battery has a low initial direct current resistance (DCR); and adding a water-draining additive to the electrolyte effectively reduces the adverse effects of unintended water (water caused by increasing the porosity of the positive electrode sheet using the pore-forming agent and water generated by the lithium-ion battery at high temperatures), improving the initial direct current resistance (DCR) and high-temperature cycle performance of the lithium-ion battery.

[0057] The secondary battery, battery module, battery pack, and power consuming device of the present application will be described below with appropriate reference to the drawings.

[0058] In one embodiment of the present application, a secondary battery is provided.

[0059] Generally, a secondary battery includes a positive electrode sheet, a negative electrode sheet, an electrolyte, and a separator. During the charging and discharging process of the battery, active ions shuttle between the positive electrode sheet and the negative electrode sheet to be inserted and removed. The electrolyte serves to conduct ions between the positive electrode sheet and the negative electrode sheet. The separator is provided between the positive electrode sheet and the negative electrode sheet, and serves mainly to prevent short circuit between the positive electrode and the negative electrode, while allowing ions to pass through. In this application, the group margin of the battery is 88%-98%. [Positive electrode sheet]

[0060] The positive electrode sheet includes a positive electrode current collector and a positive electrode film layer provided on at least one surface of the positive electrode current collector, the positive electrode film layer including the positive electrode active material according to the first aspect of the present application.

[0061] As an example, the positive electrode current collector has two surfaces opposing each other in the thickness direction, and the positive electrode film layer is provided on either one or both of the two opposing surfaces of the positive electrode current collector.

[0062] In some embodiments, the positive electrode current collector may be a metal foil or a composite current collector. For example, the metal foil may be an aluminum foil. The composite current collector may include a polymeric material base layer and a metal layer formed on at least one surface of the polymeric material base layer. The composite current collector may be formed by forming a metal material (aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver, silver alloy, etc.) on a polymeric material substrate (e.g., substrate such as polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE) etc.).

[0063] In some embodiments, the positive electrode active material may be a positive electrode active material for batteries known in the art. As an example, the positive electrode active material may include at least one of lithium-containing phosphates having an olivine structure, lithium transition metal oxides, and modified compounds thereof. The present application is not limited to these materials, and other conventional materials usable as positive electrode active materials for batteries may be used. These positive electrode active materials may be used alone or in combination of two or more. Here, examples of lithium transition metal oxides include lithium cobalt oxide (e.g., LiCoO2), lithium nickel oxide (e.g., LiNiO2), lithium manganese oxide (e.g., LiMnO2, LiMn2O4), lithium nickel cobalt oxide, lithium manganese cobalt oxide, lithium nickel manganese oxide, lithium nickel cobalt manganese oxide (e.g., LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 O2(NCM 333 (may be abbreviated as LiNi 0.5 Co 0.2 Mn 0.3 O2(NCM 523 (may be abbreviated as LiNi 0.5 Co0.25 Mn 0.25 O2(NCM 211 (may be abbreviated as LiNi 0.6 Co 0.2 Mn 0.2 O2(NCM 622 (may be abbreviated as LiNi 0.8 Co 0.1 Mn 0.1 O2(NCM 811 Lithium nickel cobalt aluminum oxide (e.g., LiNi 0.85 Co 0.15 Al 0.05 Examples of lithium-containing phosphates having an olivine structure include, but are not limited to, at least one of lithium iron phosphate (e.g., LiFePO4 (which may be abbreviated as LFP)), a composite material of lithium iron phosphate and carbon, lithium manganese phosphate (e.g., LiMnPO4), a composite material of lithium manganese phosphate and carbon, lithium manganese iron phosphate, and a composite material of lithium manganese iron phosphate and carbon.

[0064] In some embodiments, the pore-forming agent is at least one selected from oxalic acid, ammonium bicarbonate, ammonium carbonate, urea, ammonium chloride, and ammonium fluoride, and the mass ratio of the pore-forming agent to the positive electrode active material is 1:100-8:100. The pore-forming agent is added to the positive electrode slurry, and exists stably at room temperature, and completely decomposes into gas after the positive electrode sheet is dried, forming pore paths in the positive electrode membrane layer, and no other harmful substances remain. By selecting the above pore-forming agent, it is possible to form well-distributed pore paths in the positive electrode sheet. In addition, the amount of the pore-forming agent and the positive electrode active material satisfy the above ratio, which ensures effective infiltration and absorption of the electrolyte, effectively improves the migration speed of lithium ions, and makes the secondary battery have good initial direct current resistance (DCR).

[0065] In some embodiments, the positive electrode membrane layer optionally further comprises a binder. For example, the binder may comprise at least one of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, and fluorine-containing acrylate resin.

[0066] In some embodiments, the positive electrode membrane layer optionally further comprises a conductive agent. For example, the conductive agent may comprise at least one of superconducting carbon, acetylene black, carbon black, ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0067] In some embodiments, the components for producing the positive electrode sheet, such as a positive electrode active material, a pore-forming agent, a conductive agent, a binder, and any other components, are dispersed in a solvent (e.g., N-methylpyrrolidone) to form a positive electrode slurry, and the positive electrode slurry is applied to a positive electrode current collector, followed by steps such as drying and cold pressing to obtain a positive electrode sheet, thereby producing the positive electrode sheet. [Negative electrode sheet]

[0068] The negative electrode sheet includes a negative electrode current collector and a negative electrode film layer including a negative electrode active material provided on at least one surface of the negative electrode current collector.

[0069] For example, the negative electrode current collector has two surfaces opposing each other in the thickness direction, and the negative electrode film layer is provided on either one or both of the two opposing surfaces of the negative electrode current collector.

[0070] In some embodiments, the negative electrode current collector can be a metal foil or a composite current collector. For example, a copper foil can be used as the metal foil piece. The composite current collector can include a polymeric material substrate and a metal layer formed on at least one surface of the polymeric material substrate. The composite current collector can be formed by forming a metal material (copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver, silver alloy, etc.) on a polymeric material substrate (e.g., substrate such as polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE) etc.).

[0071] In some embodiments, the negative electrode active material may be a battery negative electrode active material known in the art. For example, the negative electrode active material may include at least one of artificial graphite, natural graphite, soft carbon, hard carbon, silicon-based material, tin-based material, and lithium titanate. The silicon-based material may be at least one selected from silicon alone, silicon oxygen compounds, silicon carbon composites, silicon nitrogen composites, and silicon alloys. The tin-based material may be at least one selected from tin alone, tin oxygen compounds, and tin alloys. However, the present application is not limited to these materials, and other conventional materials that can be used as a battery negative electrode active material may be used. These negative electrode active materials may be used alone or in combination of two or more.

[0072] In some embodiments, the negative electrode membrane layer optionally further comprises a binder, which may be at least one selected from styrene butadiene rubber (SBR), polyacrylic acid (PAA), sodium polyacrylate (PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), polymethacrylic acid (PMAA), and carboxymethyl chitosan (CMCS).

[0073] In some embodiments, the negative electrode membrane layer optionally further comprises a conductive agent, which may be at least one selected from superconducting carbon, acetylene black, carbon black, ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0074] In some embodiments, the negative electrode membrane layer optionally further comprises other auxiliary agents, such as a thickening agent (eg, sodium carboxymethylcellulose (CMC-Na)). In some embodiments, the components for producing the negative electrode sheet, such as the negative electrode active material, the conductive agent, the binder, and any other components, are dispersed in a solvent (e.g., deionized water) to form a negative electrode slurry, and the negative electrode slurry is applied to a negative electrode current collector, followed by steps such as drying and cold pressing to obtain a negative electrode sheet, thereby producing a negative electrode sheet. [Electrolyte]

[0075] The electrolyte serves to conduct ions between the positive electrode sheet and the negative electrode sheet. The present application does not specifically limit the type of electrolyte, and it can be selected as necessary. The electrolyte may be, for example, liquid, gel, or all solid.

[0076] In some embodiments, an electrolytic solution is used as the electrolyte.

[0077] In some embodiments, the electrolyte solution includes a water-draining additive, and the water-draining additive is at least one selected from a compound of formula I, a compound of formula II, and an isocyanate-based compound. [ka]

[0078] In the formula, R1, R2, R3, R4, R5 and R6 are each independently a silyl group having a halogen-substituted or unsubstituted alkyl group or a halogen-substituted or unsubstituted alkyl group, at least one of R1, R2 and R3 is a silyl group having a halogen-substituted or unsubstituted alkyl group, and at least one of R4, R5 and R6 is a silyl group having a halogen-substituted or unsubstituted alkyl group.

[0079] Optionally, R1, R2, R3, R4, R5 and R6 are each independently a silyl group having a halogen-substituted or unsubstituted C1-C6 alkyl group, or a halogen-substituted or unsubstituted C1-C6 alkyl group; and optionally, R1, R2, R3, R4, R5 and R6 are each independently a silyl group having a methyl group, an ethyl group, a propyl group or a butyl group, or a methyl group, an ethyl group, a propyl group or a butyl group.

[0080] and X is phosphorus or boron.

[0081] In some embodiments, the water drainage additive is at least one selected from tris(trimethylsilyl)phosphate, tris(trimethylsilyl)phosphite, diethyltrimethylsilylphosphite, tris(trimethylsilyl)borate, hexamethylene diisocyanate, trimethylsilyl isocyanate, tolylene diisocyanate, dicyclohexylmethane diisocyanate, and isophorone diisocyanate.

[0082] In some embodiments, the mass percentage a of the drainage additive in the electrolyte is 0.1%-1%, and optionally the mass percentage a of the drainage additive in the electrolyte is 0.3%-0.7%, based on the total mass of the electrolyte. The drainage additive in the electrolyte can effectively reduce the adverse effect of water on battery performance, and improve the initial direct current resistance (DCR) and high temperature cycle performance of the secondary battery.

[0083] In some embodiments, the electrolyte contains a film-forming additive, and the film-forming additive is at least one selected from adiponitrile, lithium difluorooxalate borate, vinyl ethylene carbonate, lithium difluorophosphate, lithium tetrafluoroborate, vinylene carbonate, 1,3-propane sultone, and lithium trifluoromethanesulfonate, and the mass percentage of the film-forming additive in the electrolyte relative to the total mass of the electrolyte is b, and 0.03≦a / b≦0.7, optionally 0.05≦a / b≦0.5, and further optionally 0.15≦a / b≦0.35. By adding the film-forming additive to the electrolyte, a protective film (SEI film) can be formed on the surface of the positive electrode sheet and the negative electrode sheet, and the deterioration of battery performance due to temperature rise can be reduced, and the amount of the water drainage additive and the film-forming additive in the electrolyte satisfies the above conditions, so that the adverse effect of water on battery performance can be further reduced, and the initial direct current resistance (DCR) and high temperature cycle performance of the secondary battery can be improved.

[0084] In some embodiments, the lithium salt is at least one selected from lithium hexafluorophosphate, lithium difluorooxalate borate and lithium bis(fluorosulfonyl)imide, and the mass percentage of the lithium salt in the electrolyte is 5%-18% relative to the total mass of the electrolyte. By selecting the lithium salt and the content of the lithium salt in the electrolyte, the initial direct current resistance (DCR) and high-temperature cycle performance of the secondary battery can be improved.

[0085] In some embodiments, the electrolyte solution contains an organic solvent, and the organic solvent is at least one selected from dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, ethylene carbonate, propylene carbonate, fluoroethylene carbonate, and sulfolane. By selecting the organic solvent, the initial direct current resistance (DCR) and / or high-temperature cycle performance of the secondary battery can be improved.

[0086] In some embodiments, the electrolyte solution optionally further comprises an additive, for example, the additive may include an additive that can improve certain performance of the battery, such as an additive that improves the overcharge performance of the battery, an additive that improves the high or low temperature performance of the battery, etc. [Separator]

[0087] In some embodiments, the secondary battery further includes a separator. In the present application, the type of the separator is not particularly limited, and any known porous structure separator having good chemical stability and mechanical stability can be selected.

[0088] In some embodiments, the material of the separator may be at least one selected from glass fiber, nonwoven fabric, polyethylene, polypropylene, and polyvinylidene fluoride. The separator may be a single-layer film or a multi-layer composite film, and is not particularly limited. When the separator is a multi-layer composite film, the materials of each layer may be the same or different, and is not particularly limited.

[0089] In some embodiments, the positive electrode sheet, the negative electrode sheet, and the separator can be produced into an electrode assembly by a winding process or a lamination process.

[0090] In some embodiments, the secondary battery may have an exterior packaging, which is used to seal the electrode assembly and electrolyte.

[0091] In some embodiments, the exterior of the secondary battery may be a hard case, such as a hard plastic case, an aluminum case, a steel case, etc. The exterior of the secondary battery may be a soft pack, such as a bag-shaped soft pack. The material of the soft bag may be plastic, and examples of the plastic include polypropylene, polybutylene terephthalate, and polybutylene succinate.

[0092] In the present application, the shape of the secondary battery is not particularly limited, and may be cylindrical, rectangular, or any other shape. For example, FIG. 1 shows a secondary battery 5 having a rectangular structure as an example.

[0093] In some embodiments, referring to FIG. 2, the exterior may include a housing 51 and a cover plate 53. The housing 51 may include a bottom plate and a side plate connected to the bottom plate, and the bottom plate and the side plate surround and form a receiving cavity. The housing 51 has an opening communicating with the receiving cavity, and the cover plate 53 can cover the opening to seal the receiving cavity. The positive electrode sheet, the negative electrode sheet and the separator can form an electrode assembly 52 by a winding process or a lamination process. The electrode assembly 52 is packaged in the receiving cavity. The electrolyte is infiltrated into the electrode assembly 52. ​​The number of electrode assemblies 52 included in the secondary battery 5 may be one or more, and can be selected by those skilled in the art according to specific practical needs.

[0094] In some embodiments, the secondary battery may be assembled into a battery module, and the number of secondary batteries included in the battery module may be one or more, and the specific number can be selected by those skilled in the art according to the application and capacity of the battery module.

[0095] Fig. 3 shows an example of a battery module 4. Referring to Fig. 3, in the battery module 4, the multiple secondary batteries 5 may be arranged in sequence along the longitudinal direction of the battery module 4. Of course, they may be arranged in any other manner. Furthermore, the multiple secondary batteries 5 may be fixed by fasteners.

[0096] Optionally, the battery module 4 may further include a case having an accommodation space for accommodating a plurality of secondary batteries 5.

[0097] In some embodiments, the battery modules may be assembled into a battery pack, and the number of battery modules included in the battery pack may be one or more, and the specific number can be selected by those skilled in the art according to the application and capacity of the battery pack.

[0098] 4 and 5 show an example of a battery pack 1. Referring to Fig. 4 and Fig. 5, the battery pack 1 may include a battery box and a plurality of battery modules 4 arranged in the battery box. The battery box may include an upper housing 2 and a lower housing 3, and the upper housing 2 is covered by the lower housing 3 to form an enclosed space for accommodating the battery modules 4. The plurality of battery modules 4 may be arranged in the battery box in any manner.

[0099] The present application further provides a power consuming device including at least one of the secondary battery, battery module, or battery pack according to the present application. The secondary battery, battery module, or battery pack may be used as a power source for the power consuming device, or may be used as an energy storage unit for the power consuming device. The power consuming device may include, but is not limited to, portable devices (e.g., mobile phones, laptops, etc.), electric vehicles (e.g., pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks, etc.), trains, ships and satellites, energy storage systems, etc.

[0100] The power consumption device can be a secondary battery, a battery module or a battery pack according to its usage needs.

[0101] 6 is an example of a power consumption device, such as a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle, etc. To meet the power consumption device's requirements for high power output and high energy density of secondary batteries, a battery pack or a battery module can be adopted.

[0102] Other example devices may be mobile phones, tablet computers, notebook computers, etc. These devices are generally required to be thin and can use secondary batteries as a power source. EXAMPLES

[0103] The following describes the examples of the present application. The examples described below are illustrative and are only for the purpose of explaining the present application, and cannot be understood as limiting the present application. In the examples, specific techniques or conditions are not specified, and are carried out according to the techniques or conditions described in the literature in this field, or according to the product specifications. The reagents or equipment used are all ordinary products available from commercial sources, unless the manufacturer is specified. I. Raw materials

[0104] Tris(trimethylsilyl)phosphate (TMSP, purchased from Sigma-Aldrich) Tris(trimethylsilyl)phosphite (TMSPi, purchased from Sigma-Aldrich) Diethyltrimethylsilylphosphite (C7H 19 O3PSi, purchased from Shanghai Aladdin Bio-Chemical Technology Co., Ltd.)

[0105] Tris(trimethylsilyl) borate (TMSB, purchased from Shanghai Aladdin Biochemical Technology Co., Ltd.) Hexamethylene diisocyanate (HDI, purchased from Shanghai Aladdin Bio-Chemical Technology Co., Ltd.) Trimethylsilyl isocyanate (C4H9NOSi, purchased from Shanghai Aladdin Biochemical Technology Co., Ltd.) Ethylene carbonate (EC, purchased from Shanghai Aladdin Biochemical Technology Co., Ltd.) Propylene carbonate (PC, purchased from Shanghai Aladdin Biochemical Technology Co., Ltd.) Sulfolane (SL, purchased from Shanghai Aladdin Biochemical Technology Co., Ltd.) Dimethyl carbonate (DMC, purchased from Shanghai Aladdin Biochemical Technology Co., Ltd.) Ethyl methyl carbonate (EMC, purchased from Shanghai Aladdin Biochemical Technology Co., Ltd.) Diethyl carbonate (DEC, purchased from Shanghai McKin Biotechnology Co., Ltd.) Vinylene carbonate (VC, purchased from Shanghai McKin Biotechnology Co., Ltd.) Lithium hexafluorophosphate (LiPF6, purchased from Guangzhou Tianci High-Tech Materials Co., Ltd.) 1. Secondary battery manufacturing Example 1 [Negative electrode sheet]

[0106] The negative electrode active material, artificial graphite, the conductive agent, carbon black, the binder, styrene butadiene rubber (SBR), and the thickener, sodium carboxymethylcellulose (CMC), were mixed uniformly in deionized water in a weight ratio of 97:0.5:1.5:1, and then coated on both sides of copper foil, dried, and cold pressed to obtain a negative electrode sheet. The coating amount was 0.2 g / cm. 2 , compressed density is 1.6g / cm 3 It was. [Positive electrode sheet]

[0107] The positive electrode active material lithium iron phosphate (LFP), the conductive agent carbon black, and the binder polyvinylidene fluoride (PVDF) were thoroughly mixed in a weight ratio of 97:0.5:2.5 in an appropriate amount of N-methylpyrrolidone (NMP), and then ammonium carbonate powder, a pore-forming agent, was added and thoroughly mixed and dispersed to form a uniform positive electrode slurry. The mass ratio of the pore-forming agent to the positive electrode active material was 3:100. The positive electrode slurry was applied to the surface of aluminum foil, a positive electrode current collector, and vacuum dried at 110°C for 10 minutes, followed by roll pressing to obtain a positive electrode sheet. The amount of application was 26 mg / cm. 2 , compressed density is 2.5g / cm 3 The amount of coating on one side was adjusted so as to maintain the capacity ratio of the negative electrode to the positive electrode at 1.1. [Electrolyte]

[0108] The electrolyte was prepared in a BRAUN glove box, which was filled with nitrogen gas of 99.999% purity, and the moisture in the glove box was controlled to 5 ppm or less, and the temperature was room temperature. Ethylene carbonate (EC), dimethyl carbonate (DMC), ethyl methyl carbonate (EMC), diethyl carbonate (DEC), tris(trimethylsilyl) borate (TMSB) as a water-removing additive, and lithium hexafluorophosphate (LiPF6) were uniformly mixed in a mass ratio of 25:30:20:14.7:0.3:10 to obtain an electrolyte. Here, the concentration of LiPF6 was 1 mol / L. [Separator]

[0109] A porous polymeric film of polyethylene served as the separator. [Battery manufacturing]

[0110] The positive electrode sheet, separator, and negative electrode sheet are laminated in order, and the separator is placed between the positive electrode sheet and the negative electrode sheet to play the role of isolation, and then rolled up to obtain a bare cell. A bare cell with a capacity of 100 Ah is placed on an exterior foil, and 300 g of the electrolyte prepared above is injected into the dried battery, and the secondary battery of Example 1 is obtained through processes such as vacuum sealing, standing, chemical formation, and shaping. The exterior is a hard housing with a length x width x height of 108 mm x 35.5 mm x 110.5 mm, the housing material is aluminum, the housing thickness is 0.8 mm, and the group tolerance of the battery is 95%. Examples 2-7

[0111] The secondary battery was manufactured in the same manner as in Example 1, except that the mass ratio of the pore-forming agent to the positive electrode active material, and the components and corresponding ratios of the electrolyte were different. Examples 8-12

[0112] The secondary battery was manufactured in the same manner as in Example 1, except that tris(trimethylsilyl)phosphate (TMSP), hexamethylene diisocyanate (HDI), di(trimethylsilyl)phosphite (TMSPi), diethyltrimethylsilylphosphate, and trimethylsilyl isocyanate (C4H9NOSi) were used as the water-removing additives. For details, see Table 1. Examples 13-25

[0113] The secondary battery was manufactured in the same manner as in Example 1, except that the mass ratio of the pore-forming agent to the positive electrode active material, the components of the electrolyte and the corresponding ratios were different. Comparative Example 1

[0114] The secondary battery was manufactured in the same manner as in Example 1, except that the electrolyte did not contain the water-removing additive and the film-forming additive vinylene carbonate (VC), and the components and the corresponding ratios of the electrolyte were different. 2. Testing of relevant parameters

[0115] Positive electrode layer porosity test

[0116] The porosity of the positive electrode membrane layer in the positive electrode sheets of the above examples and comparative examples was measured with reference to GB / T 24586-2009 "Measurement of apparent density, true density and porosity of iron ore" (conventional method). The test process is as follows:

[0117] A certain mass of sample is taken and placed on the AccuPyc II1340 true density meter, the test system is sealed, and helium gas or nitrogen gas is introduced according to the program. The pressure of the gas in the sample chamber and the expansion chamber is detected, and the true volume is calculated based on Bohr's law (PV=nRT) to obtain the porosity of the positive electrode membrane layer of the present application. The results are shown in Table 2. 3. Secondary battery performance testing (1) Measurement of initial direct current resistance (DCR)

[0118] At 25°C, the batteries of the above examples and comparative examples are charged to 3.65V at a constant current of 0.5C, then charged at a constant voltage until the current reaches 0.05C, and then discharged at a constant current of 0.5C for 30 minutes to adjust the battery to 50% SOC. The battery voltage at this time is U1. The battery is discharged at a constant current of 4C for 30 seconds, and samples are taken every 0.1 seconds. The end-of-discharge voltage is U2. The discharge DCR at 50% SOC represents the initial DCR of the battery, and the initial DCR of the battery is (U1-U2) / 4C. The test data is shown in Table 2. (2) Energy density test

[0119] At 25°C, the secondary batteries in the above examples and comparative examples were charged to 3.65V at a constant current of 1 / 3C, then charged to a current of 0.05C at a constant voltage of 3.65V, left to stand for 5 minutes, and then discharged to 2.5V at a constant current of 1 / 3C, and the battery discharge energy at this time was recorded. The battery discharge energy is divided by the battery weight to obtain the battery weight energy density, expressed in Wh / kg. The test data is shown in Table 2. (3) Cycle performance test at 60℃

[0120] At 60°C, the secondary batteries of the above examples and comparative examples were charged to 3.65V at a constant current of 0.5C, and then charged at a constant voltage until the current reached 0.05C. The batteries were left to stand for 5 minutes, and then discharged to 2.5V at a constant current of 1 / 3C. This was the first charge / discharge cycle of the battery, and the discharge capacity at this time was the discharge capacity of the first cycle of the battery. According to the above method, the battery was subjected to 1000 charge / discharge cycles, and the discharge capacity after the battery was cycled 1000 times was recorded. Capacity retention rate (%) after 1000 cycles at 60°C = (discharge capacity after 1000 cycles of the battery / discharge capacity of the first cycle of the battery) x 100%.

[0121] [Table 1]

[0122] [Table 2]

[0123] As can be seen from the above, compared with Comparative Example 1, the secondary batteries of Examples 1-25 of the present application adopt a thicker coating amount and a higher compression density to improve the energy density of the battery, and by adjusting the porosity of the positive electrode film layer, the infiltration of the electrolyte in the electrode sheet can be effectively improved, and the lithium ion migration speed can be improved, so that the secondary battery has a low initial direct current resistance (DCR). At the same time, the water draining additive in the electrolyte can effectively reduce the adverse effect of unintended water in the battery, so that a secondary battery that achieves both high energy density, improved initial direct current resistance (DCR) and high temperature cycle performance can be obtained.

[0124] The present application is not limited to the above-mentioned embodiment. The above-mentioned embodiment is merely illustrative, and anything that has substantially the same configuration as the technical idea within the technical scope of the present application and exhibits similar effects is included in the technical scope of the present application. In addition, various modifications that a person skilled in the art may make to the embodiment, or other forms constructed by combining some of the components in the embodiment, are also included in the scope of the present application, as long as they do not deviate from the gist of the present application. [Explanation of symbols]

[0125] 1 Battery pack 2 Upper case 3 Lower housing 4 Battery Module 5 Secondary battery 51 Housing 52 Electrode Assembly 53 Top cover assembly

Claims

1. A positive electrode sheet and an electrolyte solution are included. The positive electrode sheet includes a positive electrode current collector and a positive electrode film layer provided on at least one surface of the positive electrode current collector, the positive electrode film layer having a porosity of P; The electrolyte solution includes a drainage additive, and the mass percentage of the drainage additive in the electrolyte solution is a relative to the total mass of the electrolyte solution; 0.2≦(a ＊ 100) / P≦3.

5.

2. 0.4≦(a ＊ 100) / P≦3.3, and optionally, 1.0≦(a ＊ 100) / P≦1.

7.

3. The water drainage additive is at least one selected from the group consisting of a compound represented by formula I, a compound represented by formula II, and an isocyanate-based compound; 【Chemistry 1】 During the ceremony, R １ , R ２ , R ３ , R ４ , R ５ and R ６ are each independently a silyl group having a halogen-substituted or unsubstituted alkyl group or a halogen-substituted or unsubstituted alkyl group; R １ , R ２ and R ３ At least one of R is a silyl group having a halogen-substituted or unsubstituted alkyl group; ４ , R ５ and R ６ at least one of is a silyl group having a halogen-substituted or unsubstituted alkyl group; Optionally, the R １ , R ２ , R ３ , R ４ , R ５ and R ６ are each independently a silyl group having an unsubstituted C1-C6 alkyl group or an unsubstituted C1-C6 alkyl group, and R １ , R ２ and R ３ At least one of R is a silyl group having an unsubstituted alkyl group; ４ , R ５ and R ６ at least one of is a silyl group having an unsubstituted alkyl group; Also selectable is R １ , R ２ , R ３ , R ４ , R ５ and R ６ are each independently a silyl group having a methyl group, an ethyl group, a propyl group, or a butyl group, or a methyl group, an ethyl group, a propyl group, or a butyl group, and R １ , R ２ and R ３ At least one of R is a silyl group having a methyl group, an ethyl group, a propyl group, or a butyl group; ４ , R ５ and R ６ at least one of the groups is a silyl group having a methyl group, an ethyl group, a propyl group, or a butyl group; and, 3. The secondary battery according to claim 1, wherein X is phosphorus or boron.

4. The mass percentage a of the drainage additive in the electrolyte is 0.1%-1% relative to the total mass of the electrolyte, and optionally, the mass percentage a of the drainage additive in the electrolyte is 0.3%-0.7%. The secondary battery according to any one of claims 1 to 3.

5. The secondary battery according to any one of claims 1 to 4, characterized in that the water drainage additive is at least one selected from tris(trimethylsilyl)phosphate, tris(trimethylsilyl)phosphite, diethyltrimethylsilylphosphite, tris(trimethylsilyl)borate, hexamethylene diisocyanate, trimethylsilyl isocyanate, tolylene diisocyanate, dicyclohexylmethane diisocyanate and isophorone diisocyanate.

6. The secondary battery according to any one of claims 1 to 5, characterized in that the porosity P of the positive electrode film layer is 20%-70%, and optionally the porosity P of the positive electrode film layer is 30%-50%.

7. The electrolyte solution further includes a film-forming additive, and the mass percentage of the film-forming additive in the electrolyte solution is b relative to the total mass of the electrolyte solution; 7. The secondary battery according to claim 1, wherein 0.03≦a / b≦0.7 is satisfied.

8. 8. The secondary battery according to claim 7, wherein 0.05≦a / b≦0.5 is satisfied, and optionally 0.15≦a / b≦0.35 is satisfied.

9. The film-forming additive is at least one selected from adiponitrile, lithium difluorooxalate borate, vinyl ethylene carbonate, lithium difluorophosphate, lithium tetrafluoroborate, vinylene carbonate, 1,3-propane sultone, and lithium trifluoromethanesulfonate. The secondary battery according to claim 7,

10. The secondary battery according to any one of claims 1 to 9, characterized in that the electrolytic solution contains a lithium salt, the lithium salt being at least one selected from the group consisting of lithium hexafluorophosphate, lithium difluorooxalate borate, and lithium bis(fluorosulfonyl)imide, and the mass percentage of the lithium salt in the electrolytic solution is 5% to 18% with respect to the total mass of the electrolytic solution.

11. A method for producing a secondary battery according to any one of claims 1 to 10, comprising producing a positive electrode sheet, The manufacturing of the positive electrode sheet includes forming a positive electrode film layer on at least one surface of a positive electrode current collector, and the positive electrode film layer is formed by applying a positive electrode slurry containing a positive electrode active material and a pore-forming agent to one surface of the positive electrode current collector. A method for manufacturing a secondary battery.

12. The method for producing a secondary battery according to claim 11, wherein the pore-forming agent is at least one selected from the group consisting of oxalic acid, ammonium bicarbonate, ammonium carbonate, urea, ammonium chloride, and ammonium fluoride, and the mass ratio of the pore-forming agent to the positive electrode active material is 1:100 to 8:

100.

13. A battery module comprising the secondary battery according to claim 1 .

14. A battery pack comprising the battery module according to claim 13.

15. A power consuming device comprising at least one selected from the group consisting of the secondary battery according to any one of claims 1 to 10, the battery module according to claim 13, and the battery pack according to claim 14.

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