Non-aqueous electrolytes and secondary batteries, battery modules, battery packs, and power consumption devices containing them.

Abstract

The present invention provides a non-aqueous electrolyte, and a secondary battery, a battery module, a battery pack, and a power consumption device each containing the non-aqueous electrolyte. The non-aqueous electrolyte includes an electrolyte salt, a non-aqueous solvent, and a first additive, the electrolyte salt includes lithium bisfluorosulfonylimide, lithium tetrafluoroborate, and lithium difluorooxalate borate, the first additive includes fluoroethylene carbonate, and the lithium bisfluorosulfonylimide content A1, the lithium tetrafluoroborate content A2, the lithium difluorooxalate borate content A3, and the fluoroethylene carbonate content B1 based on the total mass of the non-aqueous electrolyte satisfy the following: A1 is 9% to 15%, A1 / A2 is 30 to 1500, A1 / B1 is 3.6 to 15, and A2 / A3 is 0.02 to 30. The secondary battery containing the non-aqueous electrolyte can simultaneously achieve excellent cycle performance, storage performance, safety performance, and dynamic performance.

Description

[Technical Field]

[0001] This application relates to the field of battery technology, and more specifically to non-aqueous electrolytes and secondary batteries, battery modules, battery packs, and power consumption devices containing them. [Background technology]

[0002] In recent years, secondary batteries have been widely applied in various fields, including energy storage and power systems such as hydroelectric, thermal, wind, and solar power plants, as well as power tools, electric bicycles, electric motorcycles, electric vehicles, military equipment, and aerospace. With the increasing application and proliferation of secondary batteries, their overall performance is receiving increasing attention. For example, secondary batteries need to simultaneously meet requirements such as high energy density, long cycle life, high safety performance, and high rate performance. Since the non-aqueous electrolyte plays a crucial role in ion conduction between the positive and negative electrodes and influences the performance of secondary batteries, it is necessary to provide a non-aqueous electrolyte with good overall performance. [Overview of the project]

[0003] The objective of this invention is to provide a non-aqueous electrolyte that can simultaneously achieve good cycle performance, storage performance, heat oven safety performance, and dynamic performance in a secondary battery, as well as a secondary battery, battery module, battery pack, and power consumption device containing the same.

[0004] A first aspect of the present application is a non-aqueous electrolyte comprising an electrolyte salt, a non-aqueous solvent, and a first additive, The aforementioned electrolyte salt is Based on the total mass of the non-aqueous electrolyte, lithium bisfluorosulfonylimide, which has a mass content of A1 in the non-aqueous electrolyte, Based on the total mass of the non-aqueous electrolyte, lithium tetrafluoroborate, whose mass content in the non-aqueous electrolyte is A2, Based on the total mass of the non-aqueous electrolyte, the non-aqueous electrolyte contains lithium difluorooxalate borate, which has a mass content of A3. The first additive comprises fluoroethylene carbonate, whose mass content in the non-aqueous electrolyte is B1, based on the total mass of the non-aqueous electrolyte. The non-aqueous electrolyte provides a non-aqueous electrolyte that satisfies the following conditions: A1 is 9% to 15%, A1 / A2 is 30 to 1500, A1 / B1 is 3.6 to 15, and A2 / A3 is 0.02 to 30.

[0005] As a result of diligent research by the inventors of this invention, a non-aqueous electrolyte using lithium bisfluorosulfonylimide as the main lithium salt employs lithium tetrafluoroborate, lithium difluorooxalate borate, and fluoroethylene carbonate, and by rationally adjusting the content of lithium bisfluorosulfonylimide A1, lithium tetrafluoroborate A2, lithium difluorooxalate borate A3, and fluoroethylene carbonate B1 to A1 / A2 30-1500, A1 / B1 3.6-15, and A2 / A3 0.02-30, the non-aqueous electrolyte simultaneously possesses high thermal stability, high conductivity, and a wide potential window. Furthermore, the non-aqueous electrolyte can inactivate the aluminum foil current collector and form a dense, stable, and low-impedance interfacial film on the surface of the negative electrode active material. As a result, a secondary battery employing the non-aqueous electrolyte of this invention can simultaneously achieve good cycle performance, storage performance, heat oven safety performance, and dynamic performance.

[0006] In any embodiment of the present application, A1 / A2 is 50 to 250, and selectively 50 to 150. When A1 / A2 is within an appropriate range, it helps to fully exhibit the synergistic effect between lithium bisfluorosulfonylimide and lithium tetrafluoroborate. As a result, the non-aqueous electrolyte is less corrosive to the aluminum foil current collector, and the cycle performance and storage performance of the secondary battery can be further improved.

[0007] In any embodiment of the present application, A1 / B1 is 4 to 9, and selectively 4 to 7. When A1 / B1 is within an appropriate range, it helps to fully exhibit the synergistic effect between lithium bisfluorosulfonylimide and fluoroethylene carbonate, and the non-aqueous electrolyte can simultaneously achieve high thermal stability and conductivity. This further improves the cycle performance and heat oven safety performance of the secondary battery.

[0008] In any embodiment of the present application, A2 / A3 is 0.5 to 13.5, and selectively 1 to 10. When A2 / A3 is within an appropriate range, it helps to fully realize the synergistic effect between lithium tetrafluoroborate and lithium difluorooxalate borate, not only to better protect the aluminum foil current collector but also to form a low-impedance organic-inorganic composite interface film on the surface of the negative electrode active material. This further improves the cycle performance and dynamic performance of the secondary battery.

[0009] In any embodiment of the present application, the non-aqueous electrolyte further satisfies the condition that (A2+A3) / B1 is 0.008 to 0.8, and selectively, (A2+A3) / B1 is 0.026 to 0.2. Thereafter, the BF4 in the non-aqueous electrolyte - and DFOB - BF4 ensures the formation of free ions and reduces the association of anions and cations. - and DFOB - This allows for a full improvement in the dynamic performance of secondary batteries.

[0010] In any embodiment of the present application, A1 is 10% to 15%, and selectively 10% to 13%.

[0011] In any embodiment of the present application, A2 is 0.01% to 0.3%, and selectively 0.05% to 0.2%.

[0012] In any embodiment of the present application, A3 is 0.01% to 0.5%, and selectively 0.015% to 0.1%.

[0013] In any embodiment of the present application, B1 is 1.0% to 2.5%, and selectively 1.5% to 2.5%.

[0014] In any embodiment of the present application, the non-aqueous solvent comprises: a first solvent comprising at least one of ethylene carbonate, propylene carbonate, and butylene carbonate, and having a mass content of C1 in the non-aqueous solvent based on the total mass of the non-aqueous solvent; a second solvent comprising at least one of ethyl methyl carbonate, diethyl propyl carbonate, dimethyl carbonate, dipropyl carbonate, methyl propyl carbonate, and ethyl propyl carbonate, and having a mass content of C2 in the non-aqueous solvent based on the total mass of the non-aqueous solvent; and a third solvent comprising at least one of methyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, and ethyl butyrate, and having a mass content of C3 in the non-aqueous solvent based on the total mass of the non-aqueous solvent. The non-aqueous solvent satisfies the following conditions: C1 is 10% to 30%, C2 is 50% to 90%, and C3 is 0% to 20%.

[0015] In any embodiment of the present application, C1 / (C2+C3) is between 0.1 and 0.45, and selectively between 0.2 and 0.3.

[0016] In any embodiment of the present application, the non-aqueous electrolyte comprises at least one of vinylene carbonate, ethylene sulfate, and 1,3-propanesultone, and further comprises a second additive in which the mass content B2 in the non-aqueous electrolyte is 0.05% to 2%, and selectively 0.5% to 2%, based on the total mass of the non-aqueous electrolyte. The second additive helps to further improve the interfacial performance of the positive and / or negative electrodes, thereby further improving at least one of the cycle performance, storage performance, heat oven safety performance, and dynamic performance of the secondary battery.

[0017] In any embodiment of the present application, (A1+B2) / C1 is 0.4 to 1.3, and selectively 0.4 to 0.8. This allows the secondary battery to have excellent cycle performance and avoid deterioration of dynamic performance and power performance.

[0018] In any embodiment of the present application, the non-aqueous electrolyte further comprises at least one of sulfamic acid and its salts, and further comprises a third additive whose mass content B3 in the non-aqueous electrolyte is 0.005% to 0.1%, and selectively 0.005% to 0.05%, based on the total mass of the non-aqueous electrolyte. This helps to improve the cycle performance and dynamic performance of the secondary battery.

[0019] A second aspect of the present invention provides a secondary battery comprising a positive electrode sheet, a negative electrode sheet, and a non-aqueous electrolyte, wherein the non-aqueous electrolyte is the non-aqueous electrolyte of the first aspect of the present invention. As a result, the secondary battery of the present invention can simultaneously achieve good cycle performance, storage performance, heat oven safety performance, and dynamic performance.

[0020] In any embodiment of the present application, the room-temperature conductivity of the non-aqueous electrolyte is x mS / cm, the thickness of the negative electrode sheet is Lμm, and the secondary battery satisfies L ≤ 120 × √(x / 8).

[0021] In any embodiment of the present application, the positive electrode sheet has a molecular formula Li a Ni b Coc Mn d Al e M f O g A h comprising a layered material of MaAlbMncOdAe where M is a doped cation of a transition metal site and A is a doped anion of an oxygen site, where 0.8 ≦ a ≦ 1.2, 0 ≦ b ≦ 1, 0 ≦ c ≦ 1, 0 ≦ d ≦ 1, 0 ≦ e ≦ 1, 0 ≦ f ≦ 0.2, 0 ≦ g ≦ 2, 0 ≦ h ≦ 2, b + c + d + e + f = 1, and g + h = 2.

[0022] In some embodiments of the present application, M is at least one selected from Si, Ti, Mo, V, Ge, Se, Zr, Nb, Ru, Pd, Sb, Ce, Te, and W.

[0023] In some embodiments of the present application, A is at least one selected from F, N, P, and S, and optionally, A is selected from F.

[0024] In some embodiments of the present application, 0 < b < 0.98, and optionally, 0.50 ≦ b < 0.98.

[0025] In some embodiments of the present application, c = 0.

[0026] In some embodiments of the present application, 0 < c ≦ 0.20, and optionally, 0 < c ≦ 0.10.

[0027] In some embodiments of the present application, d = 0 and 0 < e < 0.50, and optionally, d = 0 and 0 < e ≦ 0.10.

[0028] In some embodiments of the present application, e = 0 and 0 < d < 0.50, and optionally, e = 0 and 0 < d ≦ 0.10.

[0029] In some embodiments of the present application, 0 < d < 0.50 and 0 < e < 0.50, and optionally, 0 < d ≦ 0.30 and 0 < e ≦ 0.10.

[0030] A third aspect of the present application provides a battery module including a secondary battery according to the second aspect of the present application.

[0031] A fourth aspect of the present application provides a battery pack including one of the secondary battery of the second aspect of the present application and one of the battery module of the third aspect of the present application.

[0032] A fifth aspect of the present application provides a power consumption device comprising at least one of the secondary battery of the second aspect of the present application, the battery module of the third aspect, and the battery pack of the fourth aspect.

[0033] The secondary battery of this application can simultaneously achieve good cycle performance, storage performance, heat oven safety performance, and dynamic performance. The battery module, battery pack, and power consumption device of this application include the secondary battery provided by this application and therefore have at least the same advantages as the secondary battery described above. [Brief explanation of the drawing]

[0034] To more clearly explain the technical concept of the embodiments of this application, the following is a brief introduction of the drawings necessary for the embodiments of this application. Clearly, the drawings described below represent only a few embodiments of this application, and those skilled in the art can obtain further drawings based on these drawings without requiring any creative effort. [Figure 1] This is a schematic diagram of one embodiment of the secondary battery of the present invention. [Figure 2] Figure 1 is an exploded schematic diagram of an embodiment of a secondary battery. [Figure 3] This is a schematic diagram of one embodiment of the battery module of the present invention. [Figure 4] This is a schematic diagram of one embodiment of the battery pack of the present invention. [Figure 5] Figure 4 is an exploded schematic diagram of an embodiment of the battery pack shown. [Figure 6]This is a schematic diagram of one embodiment of a power consumption device that includes a secondary battery of the present invention as a power source. In the drawing, the proportions are not necessarily drawn according to actual proportions. The symbols are explained below: 1 battery pack, 2 upper housing, 3 lower housing, 4 battery module, 5 secondary battery, 51 case, 52 electrode assembly, 53 cover plate. [Modes for carrying out the invention]

[0035] Hereinafter, embodiments specifically disclosing the non-aqueous electrolyte and secondary batteries, battery modules, battery packs, and power consumption devices containing the same will be described in detail with reference to the drawings as appropriate. However, unnecessary details may be omitted. For example, detailed explanations of already well-known matters and redundant explanations of the same actual structures may be omitted. This is to avoid the following explanation becoming unnecessarily verbose and to facilitate understanding for those skilled in the art. Furthermore, the drawings and the following explanation 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.

[0036] The “range” disclosed herein is limited in the form of a lower limit and an upper limit, and a given range is limited by selecting one lower limit and one upper limit, which in particular define the boundaries of the range. Ranges limited in this manner may or may not include endpoints and can be combined in any way, that is, any lower limit can be combined with any upper limit to form a range. For example, if the ranges 60-120 and 80-110 are listed for a particular parameter, it is understood that the ranges 60-110 and 80-120 are also expected. Similarly, if the minimum range values ​​1 and 2, and the maximum range values ​​3, 4 and 5 are listed, the ranges 1-3, 1-4, 1-5, 2-3, 2-4, and 2-5 are all expected. In this application, unless otherwise stated, the numerical range “a-b” represents a contracted representation of any combination of real numbers between a and b, where a and b are both real numbers. For example, the numerical range "0 to 5" in this specification refers to all real numbers between "0 to 5", and "0 to 5" is a contracted representation of combinations of these numbers. Also, when a parameter is described as being an integer ≥ 2, it is equivalent to disclosing that the parameter is an integer such as 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0037] Unless otherwise specified, all embodiments and optional embodiments of this application can be combined to form new technical solutions, and such technical solutions should be considered to be included in the disclosures of this application.

[0038] Unless otherwise specified, all technical features and selectable technical features of this application can be combined to form new technical solutions, and such technical solutions should be considered to be included in the disclosures of this application.

[0039] Unless otherwise specified, all steps of this invention may be performed sequentially, randomly, and preferably sequentially. For example, when the method includes steps (a) and (b), it means that the method may include steps (a) and (b) performed sequentially, or steps (b) and (a) performed sequentially. For example, when 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 steps (a), (c), and (b), or further include steps (c), (a), and (b), etc.

[0040] Unless otherwise specified, the terms “have,” “equip,” and “include” as used in this application may be open or closed. For example, “have,” “equip,” and “include” may further have, equip, or include other components not listed, or may equip or include only the listed components.

[0041] Unless otherwise specified, the term “or” is inclusive in this application. For example, the phrase “A or B” means “A, B, or both A and B.” More specifically, any of the following conditions satisfy the “A or B” condition: 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).

[0042] In this application, the terms "multiple" and "multiple types" refer to two or more types.

[0043] With the increasing application and widespread use of secondary batteries, their overall performance is receiving more and more attention. Non-aqueous electrolytes are one of the important factors affecting secondary battery performance, and currently, the most widely used non-aqueous electrolyte system is a mixed carbonate solution of lithium hexafluorophosphate. However, lithium hexafluorophosphate has poor thermal stability in high-temperature environments and decomposes at high temperatures to produce PF5. PF5 is a strong Lewis acid and reacts with lone pairs of electrons on oxygen atoms in solvent molecules to decompose the solvent. Furthermore, PF5 is highly sensitive to trace amounts of water in the non-aqueous electrolyte, and upon contact with water, it produces HF, thereby increasing the acidity of the non-aqueous electrolyte, further corroding the positive electrode active material and positive electrode current collector, and leading to the elution of transition metal ions from the positive electrode active material. The transition metal ions from the positive electrode active material then elute and move to the negative electrode, where they are reduced back to the transition metal. The transition metal thus produced acts as a "catalyst," catalyzing the decomposition of the solid electrolyte interphase (SEI) film on the surface of the negative electrode active material and generating by-products. Because some of the by-products are gaseous, the secondary battery expands, affecting its safety performance. Other by-products deposit on the surface of the negative electrode active material, obstructing the lithium ion transmission channel, which increases the impedance of the secondary battery and affects its dynamic performance. Furthermore, to replace the lost interfacial film, the non-aqueous electrolyte and active lithium ions inside the battery are constantly consumed, irreversibly affecting the capacity retention rate of the secondary battery.

[0044] As a surprising discovery made through diligent research by the inventors of this application, when lithium bisfluorosulfonylimide, lithium tetrafluoroborate, lithium difluorooxalate, and fluoroethylene carbonate are simultaneously contained in appropriate amounts in a non-aqueous electrolyte, the secondary battery can simultaneously achieve good cycle performance, storage performance, heat oven safety performance, and dynamic performance. non-aqueous electrolyte

[0045] Specifically, a first embodiment of the present invention provides a non-aqueous electrolyte comprising an electrolyte salt, a non-aqueous solvent, and a first additive. The electrolyte salt comprises lithium bisfluorosulfonylimide (LiFSI) having a mass content of A1 in the non-aqueous electrolyte based on the total mass of the non-aqueous electrolyte, lithium tetrafluoroborate (LiBF4) having a mass content of A2 in the non-aqueous electrolyte based on the total mass of the non-aqueous electrolyte, and lithium difluorooxalate borate (LiDFOB) having a mass content of A3 in the non-aqueous electrolyte based on the total mass of the non-aqueous electrolyte. The first additive comprises fluoroethylene carbonate (FEC) having a mass content of B1 in the non-aqueous electrolyte based on the total mass of the non-aqueous electrolyte. The non-aqueous electrolyte satisfies the following conditions: A1 is 9% to 15%, A1 / A2 is 30 to 1500, A1 / B1 is 3.6 to 15, and A2 / A3 is 0.02 to 30.

[0046] The non-aqueous electrolyte of this invention uses lithium bisfluorosulfonylimide as the main lithium salt, with a mass content of 9% to 15% in the non-aqueous electrolyte. The chemical formula of lithium bisfluorosulfonylimide is F2NO4S2·Li, where the N atom is connected to two electron-withdrawing sulfonyl groups, thereby sufficiently delocalizing the charge on the N atom. Furthermore, lithium bisfluorosulfonylimide has a low lattice energy and is easily dissociated, which can improve the conductivity of the non-aqueous electrolyte and reduce its viscosity. In addition, lithium bisfluorosulfonylimide has good high-temperature resistance and is resistant to hydrolysis, allowing it to form a thinner interfacial film on the surface of the negative electrode active material with lower impedance and higher thermal stability, thereby reducing side reactions between the negative electrode active material and the non-aqueous electrolyte. Therefore, lithium bisfluorosulfonylimide is expected to become one of the next-generation main lithium salts, replacing lithium hexafluorophosphate.

[0047] However, one of the drawbacks of using lithium bisfluorosulfonylimide as the main lithium salt is that it has a voltage of approximately 3.7V vs. Li / Li compared to aluminum foil current collectors.+ This is corrosion. Furthermore, such corrosion progresses further at high temperatures and high voltages. Corrosion of aluminum foil current collectors has a serious impact on the performance of secondary batteries, for example, increasing battery polarization and irreversible capacity loss, and further affecting the safety performance of secondary batteries. Mainly, some solid insoluble corrosion products increase the internal resistance of secondary batteries, and some soluble corrosion products contaminate the non-aqueous electrolyte and accelerate its decomposition, increasing the self-discharge of secondary batteries, and Al produced during the corrosion process. 3+ This is demonstrated by the fact that it can transition to the negative electrode by diffusion and be reduced to aluminum dendrites. Unexpectedly during their research, the inventors discovered another drawback of using lithium bisfluorosulfonylimide as the main lithium salt: lithium bisfluorosulfonylimide reacts with LiC6 at the negative electrode, releasing large amounts of gas (e.g., SO2, NO2) and heat, which affects the safety performance of secondary batteries, particularly the safety performance of heat ovens.

[0048] Consequently, secondary batteries that primarily use lithium bisfluorosulfonylimide as a lithium salt are currently difficult to commercialize.

[0049] As a result of diligent research by the inventors of this invention, a non-aqueous electrolyte using lithium bisfluorosulfonylimide as the main lithium salt employs lithium tetrafluoroborate, lithium difluorooxalate borate, and fluoroethylene carbonate, and by rationally adjusting the content of lithium bisfluorosulfonylimide A1, lithium tetrafluoroborate A2, lithium difluorooxalate borate A3, and fluoroethylene carbonate B1, such that A1 / A2 is 30 to 1500, A1 / B1 is 3.6 to 15, and A2 / A3 is 0.02 to 30, the non-aqueous electrolyte simultaneously possesses high thermal stability, high conductivity, and a wide potential window. Furthermore, the non-aqueous electrolyte can inactivate the aluminum foil current collector and form a dense, stable, and low-impedance interfacial film on the surface of the negative electrode active material. As a result, a secondary battery employing the non-aqueous electrolyte of this invention can simultaneously achieve good cycle performance, storage performance, heat oven safety performance, and dynamic performance.

[0050] The mechanism is not clear, but the inventors speculate that the cause includes several points, including the following:

[0051] Firstly, lithium tetrafluoroborate has an inactivating effect on aluminum foil current collectors, preferentially oxidizing and decomposing on the surface of the aluminum foil current collector to form an additional inactivating film, thereby effectively improving the corrosion of lithium bisfluorosulfonylimide to the aluminum foil current collector. -Because its ionic radius is small and it readily associates with other ions, too much of it reduces the conductivity of the non-aqueous electrolyte. Further discoveries made through diligent research by the inventors show that by rationally adjusting the content of lithium bisfluorosulfonylimide A1 and lithium tetrafluoroborate A2 so that A1 / A2 is between 30 and 1500, the synergistic effect between the two can be fully realized. As a result, the non-aqueous electrolyte has both high thermal stability and high conductivity, and is less likely to corrode the aluminum foil current collector. If A1 / A2 is greater than 1500, the deactivating effect of lithium tetrafluoroborate on the aluminum foil cannot prevent the corrosion of the aluminum foil current collector by lithium bisfluorosulfonylimide, resulting in poor cycle performance of the secondary battery. If A1 / A2 is less than 30, too much lithium tetrafluoroborate significantly reduces the conductivity of the non-aqueous electrolyte, resulting in poor dynamic performance of the secondary battery.

[0052] Secondly, FEC can generate a reductive decomposition reaction at a high potential, forming a flexible and LiF-rich interfacial film on the surface of the negative electrode active material. This suppresses the reductive decomposition of low-potential non-aqueous solvents and the embedding of non-aqueous solvents into the negative electrode active material. Simultaneously, the formed interfacial film contains many chemically stable LiF components, effectively reducing the reaction between LiFSI and LiC6, thereby improving the heat oven safety performance of the secondary battery. Furthermore, FEC can withstand high-voltage oxidation and helps match with the positive electrode active material at high voltages, thereby contributing to an improvement in the energy density of the secondary battery. As a further discovery through diligent research by the inventors, when the lithium bisfluorosulfonylimide content A1 and the fluoroethylene carbonate content B1 are rationally adjusted so that A1 / B1 is between 3.6 and 15, FEC can fully demonstrate its beneficial effects on the heat oven safety performance, cycle performance, and energy density of the secondary battery. If A1 / B1 is greater than 15, the protective effect of FEC on the negative electrode cannot prevent the reaction between LiFSI and LiC6, resulting in poor safety performance of the secondary battery's heat oven. If A1 / B1 is less than 3.6, there is too much LiF in the interfacial film on the surface of the negative electrode active material, significantly increasing the internal resistance of the secondary battery and degrading its dynamic performance.

[0053] Thirdly, the anion of lithium difluorooxalate borate (DFOB - The radius of the bond is small, which reduces the charge transfer resistance of the non-aqueous electrolyte, resulting in relatively high conductivity at both high and low temperatures, and thus widening the potential window of the non-aqueous electrolyte. In the lithium difluorooxalate borate structure, the BO bond is Al 3+By combining with lithium bisfluorosulfonylimide, a further inactivating film can be formed on the surface of the aluminum foil current collector, thereby effectively improving the corrosion of lithium bisfluorosulfonylimide to the aluminum foil current collector. Lithium difluorooxalate borate can further form a low-impedance interfacial film on the surface of the negative electrode active material. At the same time, lithium difluorooxalate borate contains one oxalate group in its molecular structure, and its thermal stability is lower than that of lithium tetrafluoroborate. When heated, it is oxidized to form carbon dioxide gas, so if its content is too high, it reduces the thermal stability of the non-aqueous electrolyte and increases the amount of gas generated in the secondary battery. As a further discovery through diligent research by the inventors, by rationally adjusting the content of lithium tetrafluoroborate A2 and lithium difluorooxalate borate A3 to A2 / A3 of 0.02 to 30, not only can the aluminum foil current collector be better protected, but a low-impedance organic-inorganic composite interfacial film can be formed on the surface of the negative electrode active material, thereby further improving the cycle performance and dynamic performance of the secondary battery. If A2 / A3 is greater than 30, the impedance-reducing effect of lithium difluorooxalate borate on the negative electrode interface is weak and cannot compensate for the deterioration of the secondary battery's dynamic performance caused by lithium tetrafluoroborate. If A2 / A3 is less than 0.02, too much lithium difluorooxalate borate deteriorates the thermal stability of the non-aqueous electrolyte, worsening the secondary battery's storage performance and heat oven safety performance.

[0054] Therefore, it is believed that the secondary battery using the non-aqueous electrolyte of this application can simultaneously achieve good cycle performance, storage performance, heat oven safety performance, and dynamic performance due to the synergistic effect between the above components. Lithium tetrafluoroborate and lithium difluorooxalate borate effectively improve the corrosion of lithium bisfluorosulfonylimide to the aluminum foil current collector, reduce battery polarization, reduce irreversible capacity loss, and improve the cycle performance and storage performance of the secondary battery. Fluoroethylene carbonate effectively reduces the reaction between lithium bisfluorosulfonylimide and LiC6, improving the heat oven safety performance of the secondary battery. Lithium tetrafluoroborate, lithium difluorooxalate borate, and fluoroethylene carbonate form an organic-inorganic composite interface film containing F atoms and B atoms on the surface of the negative electrode active material, reducing the internal resistance of the secondary battery and improving the dynamic performance of the secondary battery.

[0055] In some embodiments, A1 / A2 may be 30-1000, 30-750, 30-500, 30-400, 30-300, 30-250, 30-200, 30-150, 30-100, 30-80, 50-1000, 50-750, 50-500, 50-400, 50-300, 50-250, 50-200, 50-150, 50-120, 50-100, or 50-80.

[0056] In some embodiments, A1 / B1 may be 4-15, 4-14, 4-13, 4-12, 4-11, 4-10, 4-9, 4-8, 4-7, 5-15, 5-14, 5-13, 5-12, 5-11, 5-10, 5-9, 5-8, or 5-7.

[0057] In some examples, A2 / A3 is 0.1~30, 0.1~25, 0.1~20, 0.1~18, 0.1~15, 0.1~13.5, 0.1~12, 0.1~11, 0.1~10, 0.1~9, 0.1~8, 0.1~7, 0.1~6, 0.1~5, 0.5~30, 0.5~25, 0.5~20, 0.5~ The values ​​are 18, 0.5~15, 0.5~13.5, 0.5~12, 0.5~11, 0.5~10, 0.5~9, 0.5~8, 0.5~7, 0.5~6, 0.5~5, 1~30, 1~25, 1~20, 1~18, 1~15, 1~13.5, 1~12, 1~11, 1~10, 1~9, 1~8, 1~7, 1~6, or 1~5.

[0058] When A1 / A2 is within an appropriate range, it helps to fully realize the synergistic effect between lithium bisfluorosulfonylimide and lithium tetrafluoroborate. As a result, the non-aqueous electrolyte is less corrosive to the aluminum foil current collector, and the cycle performance and storage performance of the secondary battery can be further improved.

[0059] When A1 / B1 is within an appropriate range, it helps to fully realize the synergistic effect between lithium bisfluorosulfonylimide and fluoroethylene carbonate. Non-aqueous electrolytes can simultaneously achieve high thermal stability and conductivity, thereby further improving the cycle performance and heat oven safety performance of secondary batteries.

[0060] When A2 / A3 is within an appropriate range, it helps to fully realize the synergistic effect between lithium tetrafluoroborate and lithium difluorooxalate borate. Not only can the aluminum foil current collector be better protected, but a low-impedance organic-inorganic composite interface film can be formed on the surface of the negative electrode active material, thereby further improving the cycle performance and dynamic performance of the secondary battery.

[0061] The anionic radii of lithium tetrafluoroborate and lithium difluorooxalate borate are small, making them difficult to completely dissociate in a non-aqueous electrolyte, and allowing anions and cations to easily associate. Further discoveries made through diligent research by the inventors show that by rationally adjusting the content of lithium tetrafluoroborate A2, lithium difluorooxalate borate A3, and fluoroethylene carbonate B1 to (A2+A3) / B1 between 0.008 and 0.8, the viscosity of the non-aqueous electrolyte becomes appropriate, while maintaining high conductivity. This is possible because FEC has a high dielectric constant, resulting in BF4 in the non-aqueous electrolyte. - and DFOB - This ensures the formation of free ions, reduces the association of anions and cations, and thereby BF4 - and DFOB - This can fully demonstrate its effect in improving the dynamic performance of secondary batteries. Also, when (A2+A3) / B1 is greater than 0.8, BF4 in the non-aqueous electrolyte - and DFOB - The tendency for these compounds to aggregate easily, potentially increasing the viscosity of the non-aqueous electrolyte and reducing its conductivity, and the possibility that (A2+A3) / B1 is less than 0.008, which could reduce the conductivity of the non-aqueous electrolyte due to the high viscosity of the FEC itself, can be effectively avoided. Selectively, in some embodiments, (A2+A3) / B1 is 0.01~0.8, 0.01~0.7, 0.01~0.6, 0.01~0.5, 0.01~0.4, 0.01~0.3, 0.01~0.2, 0.026~0.8, 0.026~0.7, 0.026~0.6, 0.026~0.5, 0.026~0.4, 0.026~0.3, 0.026~0.2, 0.1~0.8, 0.1~0.7, 0.1~0.6, 0.1~0.5, 0.1~0.4, 0.1~0.3, or 0.1~0.2.

[0062] The non-aqueous electrolyte of the present application mainly uses lithium bisfluorosulfonylimide as a lithium salt, and has a high mass content of the same in the non-aqueous electrolyte. In some examples, A1 may be 10%~15%, 11%~15%, 12%~15%, 13%~15%, 9%~14%, 10%~14%, 11%~14%, 12%~14%, 13%~14%, 9%~13%, 10%~13%, 11%~13%, or 12%~13%.

[0063] An increase in the LiBF4 content reduces the conductivity of the non-aqueous electrolyte, which is unfavorable for forming a stable interfacial film on the surface of the negative electrode active material. In some examples, A2 may be 0.01% to 0.3%. Selectively, A2 may be 0.02%~0.3%, 0.02%~0.26%, 0.02%~0.22%, 0.02%~0.2%, 0.02%~0.18%, 0.02%~0.16%, 0.02%~0.14%, 0.02%~0.12%, 0.02%~0.1%, 0.05%~0.3%, 0.05%~0.26%, 0.05%~0.22%, 0.05%~0.2%, 0.05%~0.18%, 0.05%~0.16%, 0.05%~0.14%, 0.05%~0.12%, or 0.05%~0.1%.

[0064] LiDFOB contains one oxalate group in its molecular structure, which oxidizes when heated to form carbon dioxide gas, reducing the thermal stability of the non-aqueous electrolyte. In some examples, A3 may be 0.01% to 0.5%. Selectively, A3 may be 0.01%~0.45%, 0.01%~0.4%, 0.01%~0.35%, 0.01%~0.3%, 0.01%~0.25%, 0.01%~0.2%, 0.01%~0.15%, 0.01%~0.1%, 0.015%~0.45%, 0.015%~0.4%, 0.015%~0.35%, 0.015%~0.3%, 0.015%~0.25%, 0.015%~0.2%, 0.015%~0.15%, or 0.015%~0.1%.

[0065] As the FEC content increases, the viscosity of the non-aqueous electrolyte increases and the conductivity decreases. At the same time, FEC readily decomposes at high temperatures to form HF, which disrupts the structural stability of the positive electrode active material, increases the amount of gas generated in the secondary battery, and affects the storage performance and heat oven safety performance of the secondary battery. In some examples, B1 may be 1.0% to 2.5%. For example, B1 may be 1.1% to 2.5%, 1.2% to 2.5%, 1.3% to 2.5%, 1.4% to 2.5%, 1.5% to 2.5%, 1.6% to 2.5%, 1.7% to 2.5%, 1.8% to 2.5%, 1.9% to 2.5%, or 2% to 2.5%.

[0066] In some embodiments, the non-aqueous solvent includes at least one of the first solvent, the second solvent, and the third solvent.

[0067] The first solvent is a cyclic carbonate compound and may include, for example, at least one of ethylene carbonate (EC), propylene carbonate (PC), and butylene carbonate (BC). Selectively, the first solvent includes ethylene carbonate.

[0068] The second solvent is a chain-like carbonate compound and may include, for example, at least one of ethyl methyl carbonate (EMC), diethyl propyl carbonate (DEC), dimethyl carbonate (DMC), dipropyl carbonate (DPC), methyl propyl carbonate (MPC), and ethyl propyl carbonate (EPC). Selectively, the second solvent may include at least one of ethyl methyl carbonate (EMC), diethyl propyl carbonate (DEC), and dimethyl carbonate (DMC).

[0069] In some embodiments, the non-aqueous solvent comprises at least a first solvent and a second solvent. High content of the electrolyte salt and the first additive increases the viscosity of the non-aqueous electrolyte, reduces its conductivity, and is detrimental to forming a uniform, dense, stable, and low-impedance interfacial film on the surface of the negative electrode active material. The first solvent has a high dielectric constant, thus increasing the conductivity of the non-aqueous electrolyte, and the second solvent has a low viscosity, thus reducing the viscosity of the non-aqueous electrolyte. Therefore, when the non-aqueous solvent simultaneously comprises both the first and second solvents, it helps the non-aqueous electrolyte to have appropriate viscosity and conductivity, and further helps in the transport of lithium ions and the formation of a uniform, dense, stable, and low-impedance interfacial film on the surface of the negative electrode active material.

[0070] In some embodiments, the non-aqueous solvent may further include a third solvent. The third solvent is a carboxylic acid ester compound and may include at least one of the following: methyl formate (MF), methyl acetate (MA), ethyl acetate (EA), propyl acetate (PA), methyl propionate (MP), ethyl propionate (EP), propyl propionate (PP), methyl butyrate (MB), and ethyl butyrate (EB). The third solvent helps the non-aqueous electrolyte to have appropriate viscosity and conductivity and is further advantageous for lithium ion transport. The third solvent may further enhance BF4 in the non-aqueous electrolyte. - and DFOB - This ensures the formation of free ions and helps reduce the association of anions and cations, thereby BF4 - and DFOB - This allows for a full improvement in the capacity retention rate and dynamic performance of secondary batteries.

[0071] The non-aqueous solvent of this application may further include other solvents other than the first, second, and third solvents described above. For example, the other solvent may include sulfone solvents such as sulfolane (SF), dimethyl sulfone (MSM), methyl ethyl sulfone (EMS), and diethyl sulfone (ESE).

[0072] In several embodiments, based on the total mass of the non-aqueous solvent, the mass content of the first solvent in the non-aqueous solvent is C1, the mass content of the second solvent in the non-aqueous solvent is C2, the mass content of the third solvent in the non-aqueous solvent is C3, and the non-aqueous solvent satisfies the following conditions: C1 is 10% to 30%, C2 is 50% to 90%, and C3 is 0% to 20%.

[0073] In some examples, C1 / (C2+C3) is 0.1 to 0.45, and selectively 0.2 to 0.3. When the non-aqueous solvent contains an appropriate amount of the first solvent, and especially when it contains an appropriate amount of ethylene carbonate, the radicals formed by the decomposition of lithium difluorooxalate borate induce ring-opening and polymerization of ethylene carbonate, making the interfacial film formed on the surface of the negative electrode active material denser and smoother, thereby effectively suppressing dendrite growth.

[0074] In some embodiments, the non-aqueous electrolyte further comprises a second additive comprising at least one of vinylene carbonate (VC), ethylene sulfate (DTD), and 1,3-propanesultone (PS). These second additives help to further improve the interfacial properties of the positive and / or negative electrodes, thereby further improving at least one of the cycle performance, storage performance, heat oven safety performance, and dynamic performance of the secondary battery.

[0075] In some embodiments, based on the total mass of the non-aqueous electrolyte, the mass content of the second additive in the non-aqueous electrolyte is B2, and B2 may be 0.05% to 2%. Selectively, B2 is 0.1% to 2%, 0.2% to 2%, 0.3% to 2%, 0.4% to 2%, 0.5% to 2%, 0.6% to 2%, 0.7% to 2%, 0.8% to 2%, 0.9% to 2%, 1% to 2%, 0.1% to 1%, 0.2% to 1%, 0.3% to 1%, 0.4% to 1%, 0.5% to 1%, 0.6% to 1%, 0.7% to 1%, 0.8% to 1%, 0.9% to 1%, or 1% to 1%.

[0076] In some examples, the content of lithium bisfluorosulfonylimide A1, the content of the second additive B2, and the content of the first solvent C1 satisfy the condition that (A1 + B2) / C1 is 0.4 to 1.3, and is selectively between 0.4 and 0.8. The second additive helps to reduce persistent side reactions by forming a film on the surfaces of the positive and negative electrodes, thereby improving at least one of the cycle performance, storage performance, heat oven safety performance, and dynamic performance of the secondary battery. However, if the content of the second additive is high, the interface impedance of the positive electrode and / or the negative electrode increases, affecting the power performance of the secondary battery. Lithium bisfluorosulfonylimide can improve the conductivity and thermal stability of the non-aqueous electrolyte and reduce the interface impedance of the positive electrode and / or the negative electrode, but it causes some corrosion to the aluminum foil current collector, and if its content is high, it affects the cycle performance of the secondary battery. The first solvent has a high dielectric constant and is useful in the dissociation of lithium salts, thus improving the conductivity of the non-aqueous electrolyte to some extent. However, if its content is high, it increases the viscosity of the non-aqueous electrolyte on the one hand, and on the other hand, affects the thermal stability of the non-aqueous electrolyte, thereby affecting the storage performance of the secondary battery. Further research by the inventors has shown that controlling (A1+B2) / C1 between 0.4 and 1.3, and selectively between 0.4 and 0.8, helps to fully exert the synergistic effect between the above components and effectively reduces the defects of each component when used individually, thereby enabling the secondary battery to have excellent cycle performance and avoid deterioration of dynamic performance and power performance.

[0077] In some embodiments, the non-aqueous electrolyte further comprises a third additive comprising at least one of sulfamic acid and its salts. The molecular formula of sulfamic acid is H3NO3S, and the sulfamate comprises at least one of ammonium salts, alkali metal salts, alkaline earth metal salts, and alkaline earth metal salts. For example, the sulfamate may include at least one of ammonium sulfamate, lithium sulfamate, sodium sulfamate, and zinc sulfamate. Selectively, the third additive comprises sulfamic acid, lithium sulfamate, or a combination thereof.

[0078] Sulfamic acid is highly acidic and is typically used to produce lithium bisfluorosulfonylimide. Currently, its application to non-aqueous electrolytes has not been discovered. In a surprising discovery made through further research by the inventors of this invention, when the non-aqueous electrolyte contains an appropriate amount of sulfamic acid and its salts, it helps improve the cycle performance and dynamic performance of secondary batteries. Although the mechanism is not clear, the inventors speculate that sulfamic acid and its salts improve the conductivity and viscosity of the non-aqueous electrolyte, and at the same time, can slowly dissolve metals such as lithium dendrites to some extent. As a result, the amount of elemental lithium, elemental aluminum, and elemental transition metals deposited on the surface of the negative electrode active material can be reduced, allowing the secondary battery to have improved cycle performance and dynamic performance.

[0079] Sulfamic acid and its salts are readily soluble in water and highly acidic. When their content is high, they corrode the positive electrode active material and destroy the stability of the positive electrode interface film and the negative electrode interface film. In some examples, based on the total mass of the non-aqueous electrolyte, the mass content of the third additive in the non-aqueous electrolyte is B3, and B3 is selectively 0.005% to 0.1%, and more selectively 0.005% to 0.05%.

[0080] In some embodiments, the non-aqueous electrolyte may further contain the second and third additives simultaneously.

[0081] In some embodiments, the non-aqueous electrolyte may further contain at least one of the following electrolyte salts: lithium hexafluorophosphate (LiPF6), lithium perchlorate (LiClO4), lithium hexafluoroarsenate (LiAsF6), lithium trifluoromethanesulfonate (LiTFS), lithium difluorophosphate (LiPO2F2), lithium difluorobisoxalate phosphate (LiDFOP), and lithium tetrafluorooxalate phosphate (LiTFOP). These other electrolyte salts can further improve the interfacial properties of the positive and / or negative electrodes, or improve the conductivity or thermal stability of the non-aqueous electrolyte. Selectively, based on the total mass of the non-aqueous electrolyte, the total mass content of these other electrolyte salts in the non-aqueous electrolyte is 1% or less, and more selectively, 0.5% or less.

[0082] The non-aqueous electrolyte of this application can be prepared according to general methods in the art. For example, the additive, the non-aqueous solvent, the electrolyte salt, etc. can be uniformly mixed to obtain the non-aqueous electrolyte. The order in which the materials are added is not particularly limited; for example, the additive, the electrolyte salt, etc. can be added to the non-aqueous solvent and uniformly mixed to obtain the non-aqueous electrolyte.

[0083] In this application, each component in the non-aqueous electrolyte and its content can be measured according to methods known in the art. For example, they can be measured by gas chromatography-mass spectrometry (GC-MS), ion chromatography (IC), liquid chromatography (LC), nuclear magnetic resonance spectroscopy (NMR), etc.

[0084] In the case of testing the non-aqueous electrolyte of this application, the freshly prepared non-aqueous electrolyte may be used directly, or the non-aqueous electrolyte may be obtained from a secondary battery. One exemplary method for obtaining the non-aqueous electrolyte from a secondary battery includes the steps of discharging the secondary battery to its discharge termination voltage (usually the battery is fully discharged for safety), centrifuging it, and then obtaining an appropriate amount of the liquid obtained by centrifugation, i.e., the non-aqueous electrolyte. The non-aqueous electrolyte may also be obtained directly from the filling port of the secondary battery. secondary battery

[0085] A second embodiment of the present invention provides a secondary battery comprising an electrode assembly and a non-aqueous electrolyte, wherein the non-aqueous electrolyte is the non-aqueous electrolyte of the first embodiment of the present invention, thereby enabling the secondary battery of the present invention to simultaneously achieve good cycle performance, storage performance, heat oven safety performance, and dynamic performance.

[0086] The secondary battery of this application may be a lithium secondary battery, and in particular may be a lithium-ion secondary battery.

[0087] An electrode assembly typically includes a positive electrode sheet, a negative electrode sheet, and a separator. The separator is placed between the positive and negative electrode sheets and primarily serves to prevent short circuits between the positive and negative electrodes while simultaneously allowing lithium ions to pass through. [Positive electrode sheet]

[0088] In some embodiments, 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 and containing a positive electrode active material. For example, the positive electrode current collector has two opposing surfaces in its thickness direction, and the positive electrode film layer is provided on one or both of the two opposing surfaces of the positive electrode current collector.

[0089] The positive electrode film layer includes a positive electrode active material. The positive electrode active material can be a positive electrode active material known in the art and used in secondary batteries. For example, the positive electrode active material may include at least one of lithium transition metal oxides, lithium-containing phosphates with an olivine structure, and their respective modified compounds. Examples of lithium transition metal oxides include lithium cobalt oxide, lithium nickel oxide, lithium manganese oxide, lithium nickel cobalt oxide, lithium manganese cobalt oxide, lithium nickel manganese oxide, lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminum oxide, and at least one of these modified compounds. Examples of lithium-containing phosphates with an olivine structure include lithium iron phosphate, a composite material of lithium iron phosphate and carbon, lithium manganese phosphate, a composite material of lithium manganese phosphate and carbon, lithium iron manganese phosphate, a composite material of lithium iron manganese phosphate and carbon, and at least one of their respective modified compounds. The present invention is not limited to these materials, and other conventionally known materials used as positive electrode active materials for secondary batteries can be used. These positive electrode active materials may be used individually or in combination of two or more types.

[0090] In some embodiments, the positive electrode active material has the molecular formula Li a Ni b Co c Mn d Al e M f O g A h The material comprises a layered material where M represents a doped cation at a transition metal site and A represents a doped anion at an oxygen site, where 0.8 ≤ a ≤ 1.2, 0 ≤ b ≤ 1, 0 ≤ c ≤ 1, 0 ≤ d ≤ 1, 0 ≤ e ≤ 1, 0 ≤ f ≤ 0.2, 0 ≤ g ≤ 2, 0 ≤ h ≤ 2, b + c + d + e + f = 1, g + h = 2.

[0091] The molecular formula is Li a Ni b Co c Mn d Al e M f Og A h The layered material of can be selectively doped and modified by M cations, A anions, or both M cations and A anions. The crystal structure of the layered material obtained after doping is more stable, and the electrochemical performance of the secondary battery, such as cycle performance, dynamic performance, etc., can be further improved.

[0092] In some embodiments, M is at least one selected from Si, Ti, Mo, V, Ge, Se, Zr, Nb, Ru, Pd, Sb, Ce, Te, and W.

[0093] In some embodiments, A is at least one selected from F, N, P, and S. Optionally, A is selected from F. After being doped and modified by F, Li a Ni b Co c Mn d Al e M f O g A h The crystal structure of is more stable, whereby the secondary battery can have better cycle performance and dynamic performance.

[0094] The values of a, b, c, d, e, f, g, h satisfy the condition of keeping Li a Ni b Co c Mn d Al e M f O g A h electrically neutral.

[0095] In some embodiments, 0 < b < 0.98. Optionally, 0.50 ≤ b < 0.98, 0.55 ≤ b < 0.98, 0.60 ≤ b < 0.98, 0.65 ≤ b < 0.98, 0.70 ≤ b < 0.98, 0.75 ≤ b < 0.98, or 0.80 ≤ b < 0.98.

[0096] In some embodiments, c = 0.

[0097] In some embodiments, 0 < c ≤ 0.20. Optionally, 0 < c ≤ 0.15, 0 < c ≤ 0.10, 0 < c ≤ 0.09, 0 < c ≤ 0.08, 0 < c ≤ 0.07, 0 < c ≤ 0.06, 0 < c ≤ 0.05, 0 < c ≤ 0.04, 0 < c ≤ 0.03, 0 < c ≤ 0.02 or 0 < c ≤ 0.01. Since cobalt has a low content in the earth's crust, is difficult to mine and is expensive, low cobalt or cobalt-free is an inevitable development trend of the cathode active material. However, cobalt greatly contributes to the diffusion rate of lithium ions in the cathode active material, and low cobalt or cobalt-free reduces the diffusion rate of lithium ions in the cathode active material, affecting the cycle performance of the secondary battery. Researchers are studying to improve the diffusion rate of lithium ions in the low-cobalt or cobalt-free cathode active material, but there is still no good solution at present.

[0098] As an unexpected discovery studied by the inventors of the present application, when the content A2 of lithium tetrafluoroborate and the content A3 of lithium difluoroborate are reasonably adjusted so that A2 / A3 is 0.02 to 30, a low-impedance interfacial film is further formed on the surface of the positive electrode active material, and the B atoms in the structures of lithium tetrafluoroborate and lithium difluoroborate are more likely to bond with the O atoms in the positive electrode active material, thereby reducing the charge transfer resistance of the positive electrode active material and reducing the diffusion resistance of lithium ions in the bulk phase of the positive electrode active material. Therefore, when the non-aqueous electrolyte contains appropriate amounts of lithium tetrafluoroborate and lithium difluoroborate, the low-cobalt or cobalt-free positive electrode active material can have a significantly improved lithium ion diffusion rate, and the lithium ions in the bulk phase of the low-cobalt or cobalt-free positive electrode active material can be timely replenished to the surface, and it is possible to avoid excessive desorption of lithium on the surface of the low-cobalt or cobalt-free positive electrode active material, thereby stabilizing the crystal structure of the low-cobalt or cobalt-free positive electrode active material. Since the crystal structure of the low-cobalt or cobalt-free positive electrode active material is more stable, the probability of problems such as instability of the structural properties, chemical properties or electrochemical properties of the positive electrode active material due to excessive desorption of lithium on the surface of the low-cobalt or cobalt-free positive electrode active material can be significantly reduced. For example, the above problems include the problems of irreversible strain and increased lattice defects of the positive electrode active material.

[0099] In some embodiments, d = 0 and 0 < e < 0.50. Optionally, d = 0 and 0 < e ≤ 0.45, d = 0 and 0 < e ≤ 0.40, d = 0 and 0 < e ≤ 0.35, d = 0 and 0 < e ≤ 0.30, d = 0 and 0 < e ≤ 0.25, d = 0 and 0 < e ≤ 0.20, d = 0 and 0 < e ≤ 0.15, or d = 0 and 0 < e ≤ 0.10.

[0100] In some embodiments, e = 0 and 0 < d < 0.50. Optionally, e = 0 and 0 < d ≦ 0.45, e = 0 and 0 < d ≦ 0.40, e = 0 and 0 < d ≦ 0.35, e = 0 and 0 < d ≦ 0.30, e = 0 and 0 < d ≦ 0.25, e = 0 and 0 < d ≦ 0.20, e = 0 and 0 < d ≦ 0.15, or e = 0 and 0 < d ≦ 0.10.

[0101] In some embodiments, 0 < d < 0.50 and 0 < e < 0.50. Optionally, 0 < d ≦ 0.30 and 0 < e ≦ 0.10.

[0102] In some embodiments, g = 2 and h = 0.

[0103] In some embodiments, g = 0 and h = 2.

[0104] In some embodiments, 0 < g < 2, 0 < h < 2, and g + h = 2.

[0105] As an example, a layered material with the molecular formula Li a Ni b Co c Mn d Al e M f O g A h is LiNi 0.8 Co 0.1 Mn 0.1 O2, LiNi 0.6 Co 0.2 Mn 0.2 O2, LiNi 0.5 Co 0.2 Mn 0.3 O2, LiNi 0.8 Co 0.05 Mn 0.15 O2, LiNi 0.7 Mn 0.3 O2, LiNi 0.69 Co 0.01 Mn 0.3 O2, LiNi 0.68 Co 0.02 Mn 0.3 O2, LiNi 0.65 Co 0.05 Mn0.3 O2, LiNi 0.63 Co 0.07 Mn 0.3 O2, LiNi 0.61 Co 0.09 Mn 0.3 including at least one kind of O2, but not limited thereto.

[0106] Li a Ni b Co c Mn d Al e M f O g A h can be prepared according to the general methods in this field. As an exemplary preparation method, it is a method obtained by mixing a lithium source, a nickel source, a cobalt source, a manganese source, an aluminum source, a precursor of element M, and a precursor of element A and then sintering. The sintering atmosphere may be an oxygen-containing atmosphere, for example, an air atmosphere or an oxygen gas atmosphere. The O2 concentration in the sintering atmosphere is, for example, 70% - 100%. The sintering temperature and sintering time can be adjusted according to the actual situation.

[0107] For example, a lithium source includes, but is not limited to, at least one of lithium oxide (Li2O), lithium phosphate (Li3PO4), lithium dihydrogen phosphate (LiH2PO4), lithium acetate (CH3COOLi), lithium hydroxide (LiOH), lithium carbonate (Li2CO3), and lithium nitrate (LiNO3). For example, a nickel source includes, but is not limited to, at least one of nickel sulfate, nickel nitrate, nickel chloride, nickel oxalate, and nickel acetate. For example, a cobalt source includes, but is not limited to, at least one of cobalt sulfate, cobalt nitrate, cobalt chloride, cobalt oxalate, and cobalt acetate. For example, a manganese source includes, but is not limited to, at least one of manganese sulfate, manganese nitrate, manganese chloride, manganese oxalate, and manganese acetate. For example, an aluminum source includes, but is not limited to, at least one of aluminum sulfate, aluminum nitrate, aluminum chloride, aluminum oxalate, and aluminum acetate. For example, a precursor of element M includes, but is not limited to, at least one of the oxides, nitrate compounds, carbonate compounds, hydroxides, and acetate compounds of element M. For example, a precursor of element A includes, but is not limited to, at least one of the following: ammonium fluoride, lithium fluoride, hydrogen fluoride, ammonium chloride, lithium chloride, hydrogen chloride, ammonium nitrate, ammonium nitrite, ammonium carbonate, ammonium bicarbonate, ammonium phosphate, phosphoric acid, ammonium sulfate, ammonium bisulfite, ammonium sulfite, ammonium hydrogen sulfide, hydrogen sulfide, lithium sulfide, ammonium sulfide, and elemental sulfur.

[0108] In some examples, based on the total mass of the positive electrode film layer, the molecular formula is Li a Ni b Co c Mn d Al e M f O g A h The mass percentage of the layered material is 80% to 99%. For example, if the molecular formula is Li a Nib Co c Mn d Al e M f O g A h The mass percentage of the layered material may be in the range of 80%, 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99%, or any other value above. Selectively, the molecular formula is Li a Ni b Co c Mn d Al e M f O g A h The mass percentages of the layered material are 85%~99%, 90%~99%, 95%~99%, 80%~98%, 85%~98%, 90%~98%, 95%~98%, 80%~97%, 85%~97%, 90%~97%, or 95%~97%.

[0109] In some embodiments, the positive electrode film layer may further selectively include a positive electrode conductive agent. The present application is not particularly limited to the type of positive electrode conductive agent, and as an example, the positive electrode conductive agent includes at least one of superconducting carbon, conductive graphite, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers. In some embodiments, the mass percentage of the positive electrode conductive agent is 5% or less based on the total mass of the positive electrode film layer.

[0110] In some embodiments, the positive electrode film layer may further optionally include a positive electrode adhesive. The present application does not particularly limit the type of positive electrode adhesive, and as an example, the positive electrode adhesive may include at least one of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), a ternary copolymer of vinylidene fluoride-tetrafluoroethylene-propylene, a ternary copolymer of vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene, a copolymer of tetrafluoroethylene-hexafluoropropylene, or a fluorine-containing acrylate resin. In some embodiments, the mass percentage of the positive electrode adhesive is 5% or less based on the total mass of the positive electrode film layer.

[0111] In some embodiments, the positive electrode current collector can be a metal foil sheet or a composite current collector. As an example of a metal foil sheet, aluminum foil can be used. The composite current collector may include a polymer material substrate and a metal material layer formed on at least one surface of the polymer material substrate. As an example, the metal material is at least one selected from aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver, and silver alloy. As an example, the polymer material substrate is selected from polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.

[0112] The positive electrode film layer is typically formed by applying a positive electrode slurry to a positive electrode current collector, drying, and cold pressing. The positive electrode slurry is typically formed by dispersing a positive electrode active material, a selectable conductive agent, a selectable adhesive, and any other components in a solvent and stirring uniformly. The solvent may, but is not limited to, N-methylpyrrolidone (NMP). [Negative electrode sheet]

[0113] In some embodiments, the negative electrode sheet includes a negative electrode current collector and a negative electrode film layer provided on at least one surface of the negative electrode current collector and containing a negative electrode active material. For example, the negative electrode current collector has two opposing surfaces in its thickness direction, and the negative electrode film layer is provided on one or both of the two opposing surfaces of the negative electrode current collector.

[0114] The anode active material can be anode active material used in secondary batteries known in the art. For example, the anode active material includes, but is not limited to, at least one of natural graphite, artificial graphite, soft carbon, hard carbon, silicon-based materials, tin-based materials, and lithium titanate. The silicon-based material may include at least one of elemental silicon, silicon oxide, silicon-carbon composite, silicon-nitrogen composite, and silicon alloy material. The tin-based material may include at least one of elemental tin, tin oxide, and tin alloy material. This application is not limited to these materials, and other conventionally known materials used as anode active materials in secondary batteries may be used. These anode active materials may be used individually or in combination of two or more types.

[0115] In some embodiments, the negative electrode film layer may further selectively include a negative electrode conductive agent. The present application is not particularly limited to the type of negative electrode conductive agent, and as an example, the negative electrode conductive agent may include at least one of superconducting carbon, conductive graphite, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers. In some embodiments, the mass percentage of the negative electrode conductive agent is 5% or less based on the total mass of the negative electrode film layer.

[0116] In some embodiments, the negative electrode film layer may further optionally include a negative electrode adhesive. The present application is not particularly limited to the type of negative electrode adhesive, and as an example, the negative electrode adhesive may include at least one of the following: styrene-butadiene rubber (SBR), water-soluble unsaturated resin SR-1B, aqueous acrylic resin (e.g., polyacrylate PAA, polymethacrylate PMAA, sodium polyacrylate PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), and carboxymethyl chitosan (CMCS). In some embodiments, the mass percentage of the negative electrode adhesive is 5% or less based on the total mass of the negative electrode film layer.

[0117] In some embodiments, the negative electrode film layer may further optionally contain other additives. For example, the other additives may include thickeners such as sodium carboxymethylcellulose (CMC-Na), PTC thermistor materials, etc. In some embodiments, the mass percentage of the other additives is 2% or less based on the total mass of the negative electrode film layer.

[0118] In some embodiments, the negative electrode current collector can be a metal foil sheet or a composite current collector. Copper foil can be used as an example of a metal foil sheet. The composite current collector may include a polymer material substrate and a metal material layer formed on at least one surface of the polymer material substrate. For example, the metal material is at least one selected from copper, copper alloys, nickel, nickel alloys, titanium, titanium alloys, silver, and silver alloys. For example, the polymer material substrate is selected from polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.

[0119] In some embodiments, the room-temperature conductivity of the non-aqueous electrolyte is x mS / cm, the thickness of the negative electrode sheet is Lμm, and the secondary battery satisfies L ≤ 120 × √(x / 8).

[0120] A further discovery made by the inventors of this invention is that when the room-temperature conductivity x mS / cm of the non-aqueous electrolyte and the thickness L μm of the negative electrode sheet satisfy L ≤ 120 × √(x / 8), the non-aqueous electrolyte helps to form a uniform, dense, stable, and low-impedance organic-inorganic composite interface film on the surface of the negative electrode active material. As a result, the secondary battery can have excellent electrochemical performance, and in particular, excellent dynamic performance.

[0121] The negative electrode film layer is typically formed by applying a negative electrode slurry to a negative electrode current collector, drying, and cold pressing. The negative electrode slurry is typically formed by dispersing a negative electrode active material, a selectable conductive agent, a selectable adhesive, and other selectable auxiliary agents in a solvent and stirring uniformly. The solvent may, but is not limited to, N-methylpyrrolidone (NMP) or deionized water. [Separator]

[0122] The separator is placed between the positive electrode sheet and the negative electrode sheet and primarily serves to prevent short circuits between the positive and negative electrodes, while simultaneously allowing lithium ions to pass through. The present invention does not particularly limit the type of separator, and any known porous structure separator having good chemical and mechanical stability can be selected.

[0123] In some embodiments, the material of the separator may include at least one of glass fiber, nonwoven fabric, polyethylene, polypropylene, and polyvinylidene fluoride. The separator may be a single-layer film or a multilayer composite film. If the separator is a multilayer composite film, the materials of each layer may be the same or different.

[0124] In some embodiments, the positive electrode sheet, the separator, and the negative electrode sheet can be manufactured into an electrode assembly by a winding process or a lamination process.

[0125] In some embodiments, the secondary battery may include an outer casing. This casing can be used to seal the electrode assembly and the non-aqueous electrolyte.

[0126] In some embodiments, the casing of the secondary battery may be a hard case, such as a rigid plastic case, an aluminum case, or a steel case. The casing of the secondary battery may also be a soft package, such as a bag-type soft package. The material of the soft package may be plastic, such as at least one of polypropylene (PP), polybutylene terephthalate (PBT), or polybutylene succinate (PBS).

[0127] The shape of the secondary battery of this application is not particularly limited and may be cylindrical, rectangular, or any other shape. Figure 1 shows a rectangular secondary battery 5 as an example.

[0128] In some embodiments, as shown in Figure 2, the exterior may include a case 51 and a cover plate 53. Here, the case 51 includes a bottom plate and side plates connected to the bottom plate, and the bottom plate and side plates surround and form a housing cavity. The case 51 has an opening that communicates with the housing cavity, and the cover plate 53 closes the housing cavity by covering the opening. The positive electrode sheet, negative electrode sheet and separator form an electrode assembly 52 by a winding process or a lamination process. The electrode assembly 52 is sealed in the housing cavity. A non-aqueous electrolyte is impregnated 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 adjusted according to the demand.

[0129] The method for manufacturing the secondary battery of the present invention is known. In some embodiments, a secondary battery can be formed by assembling a positive electrode sheet, a separator, a negative electrode sheet, and a non-aqueous electrolyte. For example, an electrode assembly is formed by winding or laminating a positive electrode sheet, a separator, and a negative electrode sheet, the electrode assembly is placed in an outer casing, dried, and then a non-aqueous electrolyte is injected. A secondary battery is then obtained through processes such as vacuum sealing, standing, chemical formation, and shaping.

[0130] In some embodiments of the present invention, the secondary battery according to the present invention can be assembled into a battery module. The number of secondary batteries included in the battery module may be multiple, and the specific number can be adjusted according to the application and capacity of the battery module.

[0131] Figure 3 is a schematic diagram of an example battery module 4. As shown in Figure 3, in the battery module 4, the multiple secondary batteries 5 may be arranged sequentially along the length of the battery module 4. Of course, they can be arranged in any other manner. The multiple secondary batteries 5 may be further fixed by fasteners.

[0132] Selectively, the battery module 4 further includes a housing having a housing space, and a plurality of secondary batteries 5 are housed in the housing space.

[0133] In some embodiments, the battery modules can be further assembled into a battery pack. The number of battery modules included in the battery pack can be adjusted according to the application and capacity of the battery pack.

[0134] Figures 4 and 5 are schematic diagrams of an example battery pack 1. As shown in Figures 4 and 5, the battery pack 1 may include a battery box and a plurality of battery modules 4 installed in the battery box. The battery box includes an upper housing 2 and a lower housing 3, with the upper housing 2 covering the lower housing 3 and being used to form a sealed space for housing the battery modules 4. The plurality of battery modules 4 can be arranged arbitrarily within the battery box. power consumption equipment

[0135] Embodiments of the present invention further provide a power consumption device comprising at least one of the secondary battery, battery module, or battery pack of the present invention. The secondary battery, battery module, or battery pack may be used as a power source for the power consumption device, or as an energy storage unit for the power consumption device. The power consumption device may be, but is not limited to, mobile devices (e.g., mobile phones, laptop computers, 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.), electric trains, ships and satellites, energy storage systems, etc.

[0136] The aforementioned power consumption device can select a secondary battery, battery module, or battery pack depending on its usage needs.

[0137] Figure 6 is a schematic diagram of an example power consumption device. This power consumption device is a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle, etc. To meet the high power and high energy density requirements of this power consumption device, a battery pack or battery module can be used.

[0138] Other examples of power-consuming devices may include mobile phones, tablet computers, and laptop computers. These power-consuming devices are typically required to be thin and can use rechargeable batteries as their power source. Examples

[0139] The following examples illustrate the disclosures of this application in more detail, and these examples are used solely for illustrative purposes. It will be apparent to those skilled in the art that various modifications and changes can be made within the scope of the disclosures. Unless otherwise specified, all parts, percentages, and ratios described in the following examples are based on mass. Furthermore, all reagents used in the examples can be obtained by purchase or synthesis according to conventional methods and are ready for direct use without further processing. Furthermore, all equipment used in the examples can be obtained by purchase.

[0140] The secondary batteries of Examples 1-43 and Comparative Examples 1-9 were all manufactured using the following method. Fabrication of positive electrode sheet

[0141] LiNi 0.6 Co 0.2 Mn 0.2 O2, carbon black (a conductive agent), and polyvinylidene fluoride (PVDF) (an adhesive) are thoroughly mixed in an appropriate amount of solvent NMP in a weight ratio of 97.5:1.4:1.1 to form a uniform positive electrode slurry. The positive electrode slurry is uniformly applied to the surface of aluminum foil, which is the positive electrode current collector, and then dried and cold-pressed to obtain a positive electrode sheet. Fabrication of negative electrode sheet

[0142] The negative electrode active material, graphite, the adhesive, styrene-butadiene rubber (SBR), the thickener, sodium carboxymethylcellulose (CMC-Na), and the conductive agent, carbon black (Super P), are mixed thoroughly with an appropriate amount of deionized water as a solvent in a weight ratio of 96.2:1.8:1.2:0.8 to form a uniform negative electrode slurry. The negative electrode slurry is uniformly applied to the surface of the copper foil, which is the negative electrode current collector, and then dried and cold-pressed to obtain a negative electrode sheet. Separator

[0143] A porous polyethylene (PE) film is used as the separator. Preparation of non-aqueous electrolyte

[0144] The electrolyte salt and additives are added to a non-aqueous solvent and mixed uniformly to obtain a non-aqueous electrolyte. The composition and content of each component are shown in Tables 1 to 3. In Tables 1 to 3, the content of each electrolyte salt and each additive is based on the total mass of the non-aqueous electrolyte, and the content of the first solvent, second solvent, and third solvent is based on the total mass of the non-aqueous solvent. " / " indicates that the corresponding component was not added. Manufacturing of secondary batteries

[0145] A positive electrode sheet, a separator, and a negative electrode sheet are stacked in order and wound together to obtain an electrode assembly. The electrode assembly is placed in an outer casing, the above-mentioned non-aqueous electrolyte is added, and after processes such as sealing, standing, chemical formation, and aging are carried out, a secondary battery is obtained. Examination process (1) Testing of the room-temperature cycle performance of secondary batteries

[0146] At 25°C, the secondary battery is charged to 4.3V with a constant current of 1C, and then continued charging with a constant voltage until the current drops to 0.05C. At this point, the secondary battery is fully charged, and the charge capacity at this time is recorded and recorded as the first charge capacity. After the secondary battery is left to stand for 5 minutes, it is discharged to 2.8V with a constant current of 1C. This is one charge-discharge cycle, and the discharge capacity at this time is recorded and recorded as the first discharge capacity. The secondary battery is subjected to a cycle charge-discharge test according to the above method, and the discharge capacity after each cycle is recorded. The capacity retention rate (%) of the secondary battery after 600 cycles at 25°C = Discharge capacity after 600 cycles / First discharge capacity × 100%. (2) Testing of the high-temperature cycle performance of secondary batteries

[0147] At 45°C, the secondary battery is charged to 4.3V with a constant current of 1C, and then continued charging with a constant voltage until the current drops to 0.05C. At this point, the secondary battery is fully charged, and the charge capacity at this time is recorded and recorded as the first charge capacity. After the secondary battery is left to stand for 5 minutes, it is discharged to 2.8V with a constant current of 1C. This is one charge-discharge cycle, and the discharge capacity at this time is recorded and recorded as the first discharge capacity. The secondary battery is subjected to a charge-discharge cycle test according to the above method, and the discharge capacity after each cycle is recorded. The capacity retention rate (%) of the secondary battery after 600 cycles at 45°C = Discharge capacity after 600 cycles / First discharge capacity × 100%. (3) Testing of the high-temperature storage performance of secondary batteries

[0148] At 60°C, a secondary battery is charged to 4.3V with a constant current of 1C, and then continued charging with a constant voltage until the current drops to 0.05C. At this time, the volume of the secondary battery is measured by the drainage method and designated as V0. The secondary battery is placed in a constant temperature chamber at 60°C and stored for 30 days. After removal, the volume of the secondary battery is measured by the drainage method and designated as V1. The volume expansion rate (%) of the secondary battery after 30 days of storage at 60°C = [(V1-V0) / V0] × 100%. (4) Test of the initial DC internal resistance of a secondary battery

[0149] At 25°C, the secondary battery is charged to 4.3V with a constant current of 1C, and then continued charging with a constant voltage until the current drops to 0.05C, at which point the secondary battery is fully charged. The secondary battery is discharged with a constant current of 0.5C and adjusted to 50% SOC, and the voltage of the secondary battery at this point is denoted as U1. The secondary battery is discharged with a constant current of 4C I1 for 30 seconds, and a sampling point of 0.1 seconds is adopted, and the discharge end voltage is denoted as U2. The DC internal resistance of the secondary battery at 50% SOC represents the initial DC internal resistance of the secondary battery, and the initial DC internal resistance of the secondary battery (mΩ) = (U1 - U2) / I1. (5) Testing of the safety performance of secondary batteries in a heat oven

[0150] At 25°C, the secondary battery is charged to 4.3V with a constant current of 1C, and then continued charging with a constant voltage until the current drops to 0.05C, at which point the secondary battery is fully charged. The fully charged secondary battery is placed in a sealed, high-temperature box and heated to 100°C at a rate of 5°C / min, held for 1 hour, then heated to 105°C at a rate of 5°C / min, held for 30 minutes. After that, the temperature is increased by 5°C / min, with each subsequent 5°C increase held for 30 minutes, stopping until the secondary battery fails, and the highest temperature before failure T is reached. max Record it. T max The higher the value, the better the heat oven safety performance of the secondary battery.

[0151] To ensure the reliability of the test results, each of the above tests may be performed using at least three parallel samples, and the average value may be used as the test result.

[0152] Tables 1-3 show the preparation parameters for the non-aqueous electrolytes of Examples 1-43 and Comparative Examples 1-9, while Tables 4 and 5 show the test results obtained according to the performance test methods described above for Examples 1-43 and Comparative Examples 1-9.

[0153] [Table 1] [Table 2] [Table 3]

[0154] [Table 4] [Table 5]

[0155] As can be seen from the test results of Comparative Examples 1-9 and Examples 1-43, when a non-aqueous electrolyte mainly using lithium bisfluorosulfonylimide as a lithium salt employs lithium tetrafluoroborate, lithium difluorooxalate borate, and fluoroethylene carbonate, and rationally adjusts the content of lithium bisfluorosulfonylimide A1, lithium tetrafluoroborate A2, lithium difluorooxalate borate A3, and fluoroethylene carbonate B1 to set A1 / A2 to 30-1500, A1 / B1 to 3.6-15, and A2 / A3 to 0.02-30, the secondary battery can simultaneously achieve a high capacity retention rate, low internal resistance, low volume expansion rate, and high heat oven safety performance.

[0156] As can be seen from the test results of Examples 37-41, the inclusion of a second and / or third additive in the non-aqueous electrolyte further helps to improve the overall performance of the secondary battery.

[0157] The inventors further studied the effect of the negative electrode sheet thickness on the secondary battery performance. The preparation of the positive electrode sheet, negative electrode sheet, non-aqueous electrolyte, and secondary battery in Examples 44-47 were all the same as in Example 5, the only difference being the thickness of the negative electrode sheet.

[0158] [Table 6]

[0159] As can be seen from the test results in Table 6, when the room-temperature conductivity x mS / cm of the non-aqueous electrolyte and the thickness Lμm of the negative electrode sheet satisfy L ≤ 120 × √(x / 8), it helps to further improve the overall performance of the secondary battery.

[0160] Furthermore, this application is not limited to the embodiments described above. The embodiments described above are merely illustrative, and any embodiment that has a configuration substantially identical to the technical idea and produces similar effects within the scope of the technical proposal of this application is included in the scope of this application. In addition, forms that add various modifications to the embodiments that can be conceived by a person skilled in the art, without departing from the spirit of this application, and other forms that are constructed by combining some of the components of the embodiments are also included in the scope of this application.

Claims

1. A non-aqueous electrolyte comprising an electrolyte salt, a non-aqueous solvent, and a first additive, The aforementioned electrolyte salt is Based on the total mass of the non-aqueous electrolyte, lithium bisfluorosulfonylimide, which has a mass content of A1 in the non-aqueous electrolyte, Based on the total mass of the non-aqueous electrolyte, lithium tetrafluoroborate, in which the mass content in the non-aqueous electrolyte is A2, Based on the total mass of the non-aqueous electrolyte, the non-aqueous electrolyte contains lithium difluorooxalate borate, which has a mass content of A3. The first additive comprises fluoroethylene carbonate, whose mass content in the non-aqueous electrolyte is B1, based on the total mass of the non-aqueous electrolyte. The non-aqueous electrolyte is a non-aqueous electrolyte that satisfies the following conditions: A1 is 9% to 15%, A1 / A2 is 30 to 1500, A1 / B1 is 3.6 to 15, A2 / A3 is 0.6 to 30, and A3 is 0.01% to 0.2%.

2. A1 / A2 is 50 to 250 and / or A1 / B1 is 4 to 9, and / or The non-aqueous electrolyte according to claim 1, wherein A2 / A3 is 0.6 to 13.

5.

3. The non-aqueous electrolyte according to claim 1, further satisfying that (A2 + A3) / B1 is 0.008 to 0.

8.

4. The non-aqueous electrolyte satisfies at least one of the following conditions (1) to (3). (1) A1 is 10% to 15%, (2) A2 is 0.01% to 0.3%, (3) The non-aqueous electrolyte according to claim 1, wherein B1 is 1.0% to 2.5%.

5. The aforementioned non-aqueous solvent is A first solvent comprising at least one of ethylene carbonate, propylene carbonate, and butylene carbonate, wherein the mass content of the first solvent in the non-aqueous solvent is C1 based on the total mass of the non-aqueous solvent, A second solvent comprising at least one of ethyl methyl carbonate, diethyl propyl carbonate, dimethyl carbonate, dipropyl carbonate, methyl propyl carbonate, and ethyl propyl carbonate, wherein the mass content in the non-aqueous solvent is C2 based on the total mass of the non-aqueous solvent, A third solvent comprising at least one of methyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, and ethyl butyrate, wherein the mass content in the non-aqueous solvent is C3 based on the total mass of the non-aqueous solvent, The non-aqueous electrolyte according to claim 1, wherein the non-aqueous solvent satisfies the following conditions: C1 is 10% to 30%, C2 is 50% to 90%, and C3 is 0% to 20%.

6. The non-aqueous electrolyte comprises at least one of vinylene carbonate, ethylene sulfate, and 1,3-propanesultone, and further comprises a second additive whose mass content in the non-aqueous electrolyte is B2 based on the total mass of the non-aqueous electrolyte. The non-aqueous electrolyte according to claim 1, wherein B2 is 0.05% to 2%.

7. The non-aqueous electrolyte according to claim 6, wherein (A1 + B2) / C1 is 0.4 to 1.

3.

8. The non-aqueous electrolyte contains at least one of sulfamic acid and its salts, and includes a third additive whose mass content in the non-aqueous electrolyte is B3 based on the total mass of the non-aqueous electrolyte. The non-aqueous electrolyte according to claim 1, wherein B3 is 0.005% to 0.1%.

9. A secondary battery comprising a positive electrode sheet, a negative electrode sheet, and a non-aqueous electrolyte as described in claim 1.

10. The secondary battery according to claim 9, wherein the room temperature conductivity of the non-aqueous electrolyte is x mS / cm, the thickness of the negative electrode sheet is L μm, and the secondary battery satisfies L ≤ 120 × √(x / 8).

11. The aforementioned positive electrode sheet has a molecular formula Li ａ Ni ｂ Co ｃ Mn ｄ Al ｅ M ｆ O ｇ A ｈ The secondary battery according to claim 9, comprising a layered material, where M represents a doped cation at a transition metal site and A represents a doped anion at an oxygen site, where 0.8 ≤ a ≤ 1.2, 0 ≤ b ≤ 1, 0 ≤ c ≤ 1, 0 ≤ d ≤ 1, 0 ≤ e ≤ 1, 0 ≤ f ≤ 0.2, 0 ≤ g ≤ 2, 0 ≤ h ≤ 2, b + c + d + e + f = 1, g + h = 2.

12. Li ａ Ni ｂ Co ｃ Mn ｄ Al ｅ M ｆ O ｇ A ｈ satisfies at least one of the following conditions (1) to (8). (1) M is at least one selected from Si, Ti, Mo, V, Ge, Se, Zr, Nb, Ru, Pd, Sb, Ce, Te and W. (2) A is at least one selected from F, N, P and S, (3) 0 < b < 0.98, (4) c = 0, (5) 0 < c ≤ 0.20, (6) d = 0 and 0 < e < 0.50, (7) e = 0 and 0 < d < 0.50, (8) The secondary battery according to claim 11, wherein 0 < d < 0.50 and 0 < e < 0.

50.

13. A battery module including the secondary battery described in claim 9.

14. A battery pack comprising one of the secondary battery described in claim 9 and the battery module described in claim 13.

15. A power consumption device comprising at least one of the secondary battery described in claim 9, the battery module described in claim 13, and the battery pack described in claim 14.

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