Secondary battery and device

Abstract

The present application relates to a secondary battery and a device. The secondary battery comprises an electrolyte; the electrolyte comprises a fluorine-containing additive, and a boron-containing and / or phosphorus-containing additive; on the basis of the total mass of the electrolyte, the mass percentage content of the fluorine-containing additive is X%, and the mass percentage content of the boron-containing and / or phosphorus-containing additive is Z%, wherein -0.4≤Z+0.0005×X2-0.0418×X+0.3106≤0.4; and 10≤X≤50.

Description

Secondary batteries and devices

[0001] This application claims priority to the Chinese patent application filed with the China Patent Office on June 28, 2023, with application number 202310780581.4 and application name “Secondary Batteries and Devices”, the entire contents of which are incorporated by reference into this application. Technical Field

[0002] The present application relates to the field of energy storage, and in particular to a secondary battery and a device. Background Art

[0003] Lithium-ion batteries are widely used in smartphones, unmanned aerial vehicles, hybrid electric vehicles, and other applications. However, with the development of society, low-energy-density lithium-ion batteries using graphite (theoretical specific capacity 372mAh / g) as the negative electrode have been unable to meet the growing demand for long-range battery life. Therefore, the development of high-capacity, high-nickel ternary material positive electrodes adapted to silicon-based materials (silicon-carbon or silicon-oxygen) negative electrodes has become the development direction of high-energy-density lithium-ion batteries.

[0004] Summary of the Invention

[0005] The inventors found that although silicon-based materials have a high theoretical specific capacity, their cycle life is limited by the volume expansion and particle pulverization of silicon-based materials; at the same time, due to the increase in the nickel content of the positive electrode sheet, its high-temperature and room-temperature safety stability continues to decline. When the battery is mechanically damaged, high-energy-density batteries including ternary material positive electrode sheets and silicon-based material negative electrode sheets often experience chain thermal runaway, causing serious safety accidents. In order to alleviate or solve at least one of the above-mentioned problems, by modifying the battery, for example, through the combination of advanced structure, binder, electrolyte, pre-lithiation and silicon-based / graphite design, the volume expansion can be alleviated, the electrode sheet expansion can be improved, and a highly elastic solid electrolyte interface film (SEI film) can be constructed. However, these solutions have limited effects on improving the battery cycle performance, or they sacrifice the capacity of the silicon-based negative electrode sheet to obtain better cycle stability. When the silicon content in the negative electrode sheet is high, the volume expansion and contraction of the silicon-based material are more obvious, and the stability of the electrode and electrolyte interface is poor. In comparison, by optimizing the electrolyte formula to inhibit the continuous adverse side reactions between the electrolyte and the negative electrode material, the volume expansion and particle pulverization of the silicon-based material are alleviated, and the cycle life and hot box safety performance of the high energy density silicon-based negative electrode battery are improved, which is more convenient, efficient and cost-friendly. Therefore, in order to alleviate or solve at least one of the above-mentioned problems, the present application provides a secondary battery, which effectively inhibits the continuous adverse side reactions between the electrolyte and the negative electrode material by controlling the content of fluorine-containing additives, boron-containing and / or phosphorus-containing additives in the secondary battery electrolyte, alleviates the volume expansion and particle pulverization of the silicon-based material, and improves the cycle life and hot box safety performance of the high energy density silicon-based negative electrode battery; and, there is a good synergistic effect between the content of fluorine-containing additives and the content of boron-containing and / or phosphorus-containing additives. The boron-containing and / or phosphorus-containing additives can dissolve the lithium fluoride produced by the fluorine-containing additive cycle, effectively alleviating the problem of large late cycle impedance caused by a high content of fluorine-containing additives, thereby reducing the late cycle impedance and improving the cycle performance and cycle life.

[0006] In one aspect of the present application, a secondary battery is provided, comprising: an electrolyte, wherein the electrolyte comprises a fluorine-containing additive and a boron-containing and / or phosphorus-containing additive; based on the total mass of the electrolyte, the mass percentage of the fluorine-containing additive is X%, and the mass percentage of the boron-containing and / or phosphorus-containing additive is Z%, wherein -0.4≤Z+0.0005×X 2 -0.0418×X+0.3106≤0.4;12≤X≤50.

[0007] Another aspect of the present application provides a device, comprising the secondary battery described in the first aspect.

[0008] The beneficial effects of this application are:

[0009] The present application controls the content of fluorine-containing additives, boron-containing and / or phosphorus-containing additives in the electrolyte of the secondary battery, so that the solid electrolyte interface film (SEI film) on the surface of the negative electrode plate is more dense and stable, effectively inhibits the continuous adverse side reactions between the electrolyte and the negative electrode material, alleviates the volume expansion and particle pulverization of the silicon-based material, and improves the cycle life and hot box safety performance of the high energy density silicon-based negative electrode battery; and there is a good synergistic effect between the content of fluorine-containing additives and the content of boron-containing and / or phosphorus-containing additives. The boron-containing and / or phosphorus-containing additives can dissolve the lithium fluoride produced by the cycle of the fluorine-containing additives, effectively alleviating the problem of large late cycle impedance caused by the high content of fluorine-containing additives, thereby reducing the late cycle impedance, improving the battery power, and then improving the cycle performance and cycle life. Based on the above improvements, the secondary battery of the present application has at least one of the following advantages: high coulombic efficiency, excellent cycle performance and cycle life, and hot box safety performance at high temperatures. DETAILED DESCRIPTION

[0010] To make the purpose, technical solutions, and advantages of this application more clear, the technical solutions of this application will be clearly and completely described below in conjunction with the embodiments. Obviously, the described embodiments are part of the embodiments of this application, rather than all the embodiments. The relevant embodiments described herein are illustrative and are used to provide a basic understanding of this application. The embodiments of this application should not be interpreted as limiting this application.

[0011] the term:

[0012] For the sake of clarity, only some numerical ranges are specifically disclosed herein. However, any lower limit may be combined with any upper limit to form an unspecified range; and any lower limit may be combined with other lower limits to form an unspecified range, and similarly, any upper limit may be combined with any other upper limit to form an unspecified range. In addition, each individually disclosed point or single value may itself serve as a lower limit or upper limit and be combined with any other point or single value, or with other lower limits or upper limits, to form an unspecified range.

[0013] As used herein, the terms "comprises," "comprising," or any other variations thereof are intended to encompass non-exclusive inclusion, such that a process, method, article, or apparatus that includes a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article, or apparatus. In the absence of further limitations, an element defined by the phrase "comprising a ..." does not preclude the presence of additional identical elements in the process, method, article, or apparatus that includes the element.

[0014] In the description herein, unless otherwise specified, “above” and “below” include the number itself.

[0015] Unless otherwise specified, the terms used in this application have the commonly understood meanings commonly understood by those skilled in the art. Unless otherwise specified, the numerical values ​​of the various parameters mentioned in this application can be measured using various measurement methods commonly used in the art (for example, they can be tested according to the methods given in the examples of this application).

[0016] A list of items connected by the terms "at least one of," "at least one of," "at least one of," or other similar terms may mean any combination of the listed items. For example, if items A and B are listed, the phrase "at least one of A and B" means only A; only B; or A and B. In another example, if items A, B, and C are listed, the phrase "at least one of A, B, and C" means only A; or only B; only C; A and B (excluding C); A and C (excluding B); B and C (excluding A); or all of A, B, and C. Item A may contain a single component or multiple components. Item B may contain a single component or multiple components. Item C may contain a single component or multiple components.

[0017] The term "C1-C6 alkyl" includes, but is not limited to, methyl, ethyl, n-propyl, isopropyl, cyclopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, cyclobutyl, n-pentyl, isopentyl, neopentyl, cyclopentyl, methylcyclopentyl, n-hexyl, isohexyl, cyclohexyl, and the like.

[0018] The term "C1-C6 alkoxy" includes, but is not limited to, methoxy, ethoxy, n-propoxy, isopropoxy, n-butoxy, isobutoxy, tert-butoxy, n-pentoxy, isopentoxy, or n-hexoxy, etc.

[0019] The term "C3-C6 alkylsilyl" refers to a silicon group having 3 to 6 carbon atoms, including but not limited to trimethylsilyl and the like.

[0020] The term "C2-C6 alkenyl" includes, but is not limited to, ethenyl, propenyl, butenyl, pentenyl or hexenyl, etc.

[0021] The term "C2-C6 alkynyl" includes, but is not limited to, ethynyl, propynyl, butynyl, pentynyl, hexynyl, and the like.

[0022] The term "C3-C6 cycloalkyl" includes, but is not limited to, cyclopropyl, cyclobutyl, cyclopentyl or cyclohexyl and the like.

[0023] The term "C6-C12 aryl" includes, but is not limited to, phenyl or naphthyl, etc.

[0024] The term "substituted or unsubstituted" means that the functional group following the term may or may not have a substituent. For example, "substituted or unsubstituted C1-C6 alkyl" refers to a C1-C6 alkyl group with a substituent or an unsubstituted C1-C6 alkyl group. The number of substituents may be one or more, and the substituents include at least one of a halogen, an alkyl group, or an aryl group. It should be understood that when the number of substituents is greater than one, the substituents may be the same or different.

[0025] The present application will be further described below in conjunction with specific embodiments. It should be understood that these specific embodiments are only used to illustrate the present application and are not used to limit the scope of the present application.

[0026] Primary and secondary batteries

[0027] The secondary battery provided by the present application includes: an electrolyte, wherein the electrolyte includes a fluorine-containing additive and a boron-containing and / or phosphorus-containing additive; based on the total mass of the electrolyte, the mass percentage of the fluorine-containing additive is X%, and the mass percentage of the boron-containing and / or phosphorus-containing additive is Z%, wherein -0.4≤Z+0.0005×X 2 -0.0418×X+0.3106≤0.4;12≤X≤50.

[0028] The present application controls the content of fluorine-containing additives, boron-containing and / or phosphorus-containing additives in the electrolyte of the secondary battery, so that the solid electrolyte interface film (SEI film) on the surface of the negative electrode sheet is more dense and stable, effectively inhibits the continuous adverse side reactions between the electrolyte and the negative electrode material, alleviates the volume expansion and particle pulverization of the silicon-based material, and improves the cycle life and hot box safety performance of the high energy density silicon-based negative electrode battery. In addition, there is a good synergistic effect between the content of fluorine-containing additives and the content of boron-containing and / or phosphorus-containing additives. On the one hand, the fluorine-containing additives (such as fluorinated carbonates) have a high exothermic temperature with the positive electrode active material. By adding a high percentage of fluorine-containing additives to replace the commonly used ethylene carbonate (EC), the self-heating rate of the battery below 200 degrees Celsius can be effectively reduced, while extending the cycle life of the silicon-based material negative electrode; on the other hand, the boron-containing and / or phosphorus-containing additives can dissolve the lithium fluoride produced by the fluorine-containing additive cycle, effectively alleviating the problem of large late cycle impedance caused by the high content of fluorine-containing additives, thereby reducing the late cycle impedance, improving the battery power, and thus improving the cycle performance and cycle life. Based on the above improvements, the secondary battery of the present application has at least one of the following advantages: high coulombic efficiency, excellent cycle performance and cycle life, and hot box safety performance at high temperatures.

[0029] In some embodiments, Z + 0.0005 × X 2-0.0418×X+0.3106 is -0.4, -0.35, -0.3, -0.25, -0.2, -0.15, -0.1, -0.05, 0, 0.1, 0.15, 0.2, 0.25, 0.35, 0.4 or any value therebetween. In some embodiments, -0.1≤Z+0.0005×X 2 -0.0418×X+0.3106≤0.1. In some embodiments, when Z+0.0005×X 2 If the value of -0.0418×X+0.3106 is too small, it cannot effectively dissolve the lithium fluoride produced by the decomposition of the fluorine-containing additive, thereby affecting its cycle performance. 2 When the value of -0.0418×X+0.3106 is too large, it will cause excessive consumption of active lithium ions, increase the irreversible capacity, reduce the coulombic efficiency, increase the impedance, and affect the electrochemical performance and energy density of the secondary battery.

[0030] In some embodiments, 12≤X≤50. In some embodiments, X is 12, 13, 14, 15, 16, 17, 18, 19, 20, 22, 24, 26, 28, 30, 32, 34, 36, 38, 40, 45, 50 or any value therebetween. In some embodiments, 15≤X≤40. In some embodiments, 18≤X≤30. Thus, the fluorine-containing additive (e.g., fluorinated carbonate) and the positive electrode active material have a high exothermic temperature. By adding a high-quality percentage of fluorine-containing additive to replace the commonly used ethylene carbonate (EC), the self-heating rate of the battery below 200 degrees Celsius can be effectively reduced, while extending the cycle life of the silicon-based negative electrode.

[0031] In some embodiments, 0.01≤Z≤2. In some embodiments, Z is 0.01, 0.02, 0.1, 0.2, 0.4, 0.6, 0.8, 1, 1.2, 1.4, 1.6, 1.8, 2, or any value therebetween. In some embodiments, 0.1≤Z≤1. Boron- and / or phosphorus-containing additives can dissolve lithium fluoride produced by the circulation of fluorine-containing additives, effectively alleviating the problem of large late cycle impedance caused by a high content of fluorine-containing additives, thereby reducing late cycle impedance, improving battery power, and thereby improving cycle performance and cycle life.

[0032] The secondary battery further comprises a negative electrode plate, the negative electrode plate comprises a negative electrode active material layer, the negative electrode active material of the negative electrode active material layer comprises a silicon-based material, and the mass percentage of the silicon-based material is Y% based on the total mass of the negative electrode active material; wherein, -10≤2.09×X-0.025×X 2 +0.004×Y 2+0.016×Y-100×Z-4.738≤10. By controlling the content of fluorine-containing additives, boron- and / or phosphorus-containing additives, and the content of silicon-based materials in the secondary battery electrolyte, the solid electrolyte interface film (SEI film) on the surface of the negative electrode plate is made denser and more stable, further inhibiting the continuous adverse side reactions between the electrolyte and the negative electrode material, further alleviating the volume expansion and particle pulverization of the silicon-based material, and improving the cycle life and hot box safety performance of high-energy-density silicon-based negative electrode batteries. In addition, there is a good synergistic effect among the content of fluorine-containing additives, boron- and / or phosphorus-containing additives, and the content of silicon-based materials in the negative electrode plate. The boron- and / or phosphorus-containing additives can dissolve the lithium fluoride produced by the fluorine-containing additives during circulation, effectively alleviating the problem of high late-cycle impedance caused by a high content of fluorine-containing additives, thereby reducing the late-cycle impedance, improving battery power, and further improving cycle performance and cycle life. In addition, the addition of fluorine-containing additives and boron-containing and / or phosphorus-containing additives acts together on the negative electrode plate containing silicon-based materials to further improve the hot box stability and cycle performance of the secondary battery.

[0033] In some embodiments, 2.09×X-0.025×X 2 +0.004×Y 2 +0.016×Y-100×Z-4.738 is -10, -9.5, -9, -8.5, -8, -7.5, -7, -6.5, -6, -5.5, -5, -4.5, -4, -3.5, -3, -2.5, -2, -1.5, -1, 0, 1, 1.5, 2, 2.5, 3, 3.5, 4, 4.5, 5, 5.5, 6, 6.5, 7, 7.5, 8, 8.5, 9, 9.5, 10, or any value therebetween. In some embodiments, -5≤2.09×X-0.025×X 2 +0.004×Y 2 +0.016×Y-100×Z-4.738≤5. In some embodiments, when 2.09×X-0.025×X 2 +0.004×Y 2 When the value of +0.016×Y-100×Z-4.738 is too small, it cannot effectively dissolve the lithium fluoride produced by the decomposition of the fluorine-containing additive, thereby affecting its cycle performance. 2 +0.004×Y 2 When the value of +0.016×Y-100×Z-4.738 is too large, it will cause excessive consumption of active lithium ions, increase the irreversible capacity, reduce the coulombic efficiency, increase the impedance, and affect the electrochemical performance and energy density of the secondary battery.

[0034] In some embodiments, 0.5≤Y≤60. In some embodiments, X is 0.5, 0.6, 0.7, 0.8, 0.9, 1, 2, 4, 6, 8, 10, 12, 15, 16, 17, 18, 19, 20, 22, 24, 26, 28, 30, 32, 34, 36, 38, 40, 45, 50, 55, 60, or any value therebetween. In some embodiments, 10≤Y≤40.

[0035] In some embodiments, the fluorine-containing additive includes: a fluorinated carbonate additive, wherein the fluorinated carbonate additive includes at least one of the compounds represented by Formula I:

[0036] Wherein, in formula I, R1, R2, R3, and R4 are independently selected from hydrogen, fluorine, substituted or unsubstituted C1-C6 alkyl, substituted or unsubstituted C1-C6 alkoxy, substituted or unsubstituted C2-C6 alkenyl, substituted or unsubstituted C2-C6 alkynyl, substituted or unsubstituted C3-C6 cycloalkyl, or substituted or unsubstituted C6-C12 aryl, wherein the substituted substituents are each independently selected from fluorine, and the R1, R2, R3, and R4 contain at least one fluorine. Thus, the fluorine-containing additive (such as fluorinated carbonate) and the positive electrode active material have a high exothermic temperature. By adding a high-quality percentage of fluorine-containing additive to replace the commonly used ethylene carbonate (EC), the self-heating rate of the battery below 200 degrees Celsius can be effectively reduced, while extending the cycle life of the silicon-based negative electrode.

[0037] In some embodiments, in Formula I, R1, R2, R3, and R4 are independently selected from fluorine, C1-C6 alkyl, and fluorine-substituted C1-C6 alkyl, and R1, R2, R3, and R4 contain at least one fluorine.

[0038] In some embodiments, the fluorine-containing additive includes at least one of the following compounds:

[0039] (fluoroethylene carbonate, FEC), (bis(fluoroethylene carbonate, DFEC), (trifluoromethyl ethylene carbonate, TFEC),

[0040] In some embodiments, the boron-containing and / or phosphorus-containing additive comprises: at least one of a boron-containing additive and a phosphorus-containing additive, wherein the boron-containing additive comprises at least one of the compounds represented by Formula II, and the phosphorus-containing additive comprises at least one of the compounds represented by Formula III and Formula IV:

[0041] Formula IV; wherein, in Formula II, Formula III and Formula IV, R5, R6, R7, R8, R9, R 10 、R 11 、R 12 、R 13 Each independently selected from a substituted or unsubstituted C1-C6 alkyl group, a substituted or unsubstituted C1-C6 alkoxy group, a substituted or unsubstituted C3-C6 alkylsilyl group, a substituted or unsubstituted C2-C6 alkenyl group, or a substituted or unsubstituted C6-C12 aryl group, wherein the substituted substituents are each independently selected from a halogen, and the halogen is selected from fluorine, chlorine, bromine, or iodine. Thus, the boron-containing and / or phosphorus-containing additive can dissolve the lithium fluoride produced by the fluorine-containing additive cycle, effectively alleviating the problem of large late cycle impedance caused by a high content of fluorine-containing additives, thereby reducing the late cycle impedance, improving the battery power, and then improving the cycle performance and cycle life.

[0042] In some embodiments, Formula II is a borate ester additive. This can further improve the composition and structure of the interface film, making the SEI film denser and more stable, allowing it to more effectively exert the above-mentioned effects, thereby further improving the cycle performance and storage performance of the secondary battery.

[0043] In some embodiments, Formula III is a phosphate additive, which can oxidatively decompose and form a positive electrode solid electrolyte interface on the surface of the positive electrode plate, which can effectively reduce the polarization voltage during the charge and discharge process, isolate the contact between the electrolyte and the positive electrode, reduce the decomposition of the electrolyte, and improve the cycle performance and rate performance of the battery. In some embodiments, Formula IV is a phosphite additive, which has an unsaturated phosphate functional group and can react with the active oxygen precipitated from the positive electrode plate to form a saturated phosphate compound, thereby capturing the active oxygen and preventing the electrolyte from being oxidized and decomposed by the precipitated active oxygen. Therefore, the addition of the phosphite additive effectively reduces the precipitation of active oxygen on the positive electrode plate side, can reduce the activity of the precipitated active oxygen, inhibit side reactions such as the oxidative decomposition of the electrolyte, and thus significantly improve the cycle performance of the secondary battery.

[0044] In some embodiments, in Formula II, Formula III and Formula IV, the R5, R6, R7, R8, R9, R 10 、R 11 、R 12 、R 13 Each is independently selected from a substituted or unsubstituted C1-C3 alkyl group, a substituted or unsubstituted C3-C6 alkylsilyl group, a substituted or unsubstituted C2-C3 alkenyl group or a substituted or unsubstituted C6-C12 aryl group, wherein the substituted substituents are each independently selected from fluorine.

[0045] In some embodiments, the boron-containing additive includes at least one of the following compounds:

[0046] (tris(trimethylsilyl)borate, TMSB),

[0047] In some embodiments, the phosphorus-containing additive includes at least one of the following compounds:

[0048] (tris(trimethylsilyl)phosphate, TMSP), (trimethyl phosphate, TMP), (Tris(2,2,2-trifluoroethyl)phosphate, TFEP), (Triphenyl phosphate, TPP).

[0049] In some embodiments, the phosphorus-containing additive includes at least one of the following compounds:

[0050] (tris(trimethylsilyl)phosphite, TMSPi), (trimethyl phosphite, TMPi), (Tris(2,2,2-trifluoroethyl)phosphite, TFEPi), (triphenyl phosphite, TPPi).

[0051] In some embodiments, the fluorine-containing additive includes fluoroethylene carbonate (FEC).

[0052] In some embodiments, the boron-containing and / or phosphorus-containing additive includes at least one of tris(trimethylsilyl)borate (TMSB) and tris(trimethylsilyl)phosphate (TMSP).

[0053] In some embodiments, the electrolyte further comprises a first additive comprising at least one of a cyclic carbonate containing a carbon-carbon double bond, a nitrile compound, and a pyridinium propanesulfonate. In some embodiments, the first additive is selected from at least one of vinylene carbonate (VC), vinyl ethylene carbonate, succinonitrile, adiponitrile, glutaronitrile, and hexanetrinitrile.

[0054] In some embodiments, the weight percentage of the first additive is 0.05%-10% based on the weight of the electrolyte. In some embodiments, the weight percentage of the first additive is 0.05%, 0.5%, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5%, 6%, 7%, 8%, 9%, 10%, or any value therebetween. In some embodiments, the weight percentage of the first additive is 0.1%-5%.

[0055] In some embodiments, the electrolyte further comprises a lithium salt selected from at least one of lithium hexafluorophosphate (LiPF6), lithium tetrafluoroborate (LiBF4), lithium trifluorosulfonyl (LiTf), lithium bis(fluorosulfonyl)imide (LiFSI), lithium trifluoromethanesulfonate, lithium (trifluoromethylsulfonyl)(perfluorobutylsulfonyl)imide (LiFNFSI), lithium bis(trifluoromethylsulfonyl)imide (LiTFSI), lithium bis(pentafluoroethylsulfonate)imide (LiBETI), lithium bis(fluoromalonate)borate (LiBFMB), lithium bis(oxalatoborate) (LiBOB), lithium difluorooxalatoborate (LiDFOB), lithium difluorobis(oxalatophosphate), and lithium 4,5-dicyano-2-(trifluoromethyl)imidazolium (LiTDI).

[0056] In some embodiments, the weight percentage of the lithium salt is 0.05%-20% based on the weight of the electrolyte. In some embodiments, the weight percentage of the lithium salt is 0.05%, 0.5%, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14%, 15%, 16%, 17%, 18%, 19%, 20%, or any value therebetween. In some embodiments, the weight percentage of the lithium salt is 1%-15%.

[0057] In some embodiments, the electrolyte further includes a solvent, and the solvent includes at least one of a linear carbonate, a cyclic carbonate, and a carboxylate.

[0058] In some embodiments, the linear carbonate is selected from at least one of dimethyl carbonate, diethyl carbonate, dipropyl carbonate, ethyl methyl carbonate, methylpropyl carbonate, ethylpropyl carbonate and fluorinated linear carbonate. In some embodiments, the cyclic carbonate includes at least one of ethylene carbonate, propylene carbonate and butylene carbonate. In some embodiments, the carboxylate is selected from at least one of methyl formate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, gamma-butyrolactone and fluorinated carboxylate.

[0059] In some embodiments, the mass percentage of the solvent is 0.05%-80% based on the mass of the electrolyte. In some embodiments, the mass percentage of the solvent is 0.05%, 0.5%, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5%, 6%, 7%, 8%, 9%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80% or any value therebetween. In some embodiments, the mass percentage of the solvent is 20%-70%.

[0060] In some embodiments, the negative electrode active material includes the silicon-based material, or a mixture of the silicon-based material and at least one material selected from the group consisting of carbon-based materials, tin-based materials, phosphorus-based materials, and metallic lithium.

[0061] In some embodiments, the silicon-based material comprises at least one of silicon, a silicon alloy, a silicon oxide, and a silicon carbon compound. In some embodiments, the carbon-based material comprises at least one of graphite, soft carbon, hard carbon, carbon nanotubes, and graphene. In some embodiments, the tin-based material comprises at least one of tin, a tin oxide, and a tin alloy. In some embodiments, the phosphorus-based material comprises phosphorus and / or a phosphorus complex.

[0062] In some embodiments, the negative electrode active material layer further comprises a binder and a conductive agent. In some embodiments, the binder includes, but is not limited to, polyvinyl alcohol, hydroxypropyl cellulose, diacetyl cellulose, polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, ethylene oxide-containing polymers, polyvinyl pyrrolidone, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, styrene-butadiene rubber, acrylated styrene-butadiene rubber, epoxy resin, or nylon.

[0063] In some embodiments, the conductive agent includes, but is not limited to, carbon-based materials, metal-based materials, conductive polymers, and mixtures thereof. In some embodiments, the carbon-based material is selected from natural graphite, artificial graphite, carbon black, acetylene black, Ketjen black, carbon fiber, or any combination thereof. In some embodiments, the metal-based material is selected from metal powder, metal fiber, copper, nickel, aluminum, or silver. In some embodiments, the conductive polymer is a polyphenylene derivative.

[0064] In some embodiments, the negative electrode plate further includes a negative electrode current collector, and the negative electrode current collector includes: copper foil, nickel foil, stainless steel foil, titanium foil, nickel foam, copper foam, a polymer substrate coated with a conductive metal, or any combination thereof.

[0065] In some embodiments, the positive electrode sheet includes a positive electrode active material layer, the positive electrode active material layer includes a positive electrode active material, and the positive electrode active material includes lithium nickel transition metal oxide.

[0066] In some embodiments, the lithium nickel transition metal oxide comprises LiNi x M 1-x At least one of the O2 materials, M is selected from at least one of cobalt, manganese, iron, chromium, titanium, zinc, vanadium, aluminum, zirconium and cerium, 0.1≤x≤1.

[0067] In some embodiments, x is 0.1, 0.15, 0.2, 0.25, 0.3, 0.35, 0.4, 0.45, 0.5, 0.55, 0.6, 0.65, 0.7, 0.75, 0.8, 0.85, 0.9, 0.95, 1, or any value therebetween.

[0068] In some embodiments, the positive electrode active material includes at least one of lithium nickel oxide, lithium nickel cobalt aluminum oxide, lithium nickel cobalt manganese oxide, lithium nickel manganese cobalt magnesium oxide, and lithium nickel manganese oxide.

[0069] In some embodiments, the positive electrode active material layer further includes a binder, and optionally a conductive material. The binder improves the bonding between the positive electrode active material particles and also improves the bonding between the positive electrode active material and the current collector.

[0070] In some embodiments, the binder includes, but is not limited to: polyvinyl alcohol, hydroxypropyl cellulose, diacetyl cellulose, polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, polymers containing ethylene oxide, polyvinyl pyrrolidone, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, styrene-butadiene rubber, acrylated styrene-butadiene rubber, epoxy resin or nylon, etc.

[0071] In some embodiments, the conductive material includes, but is not limited to, carbon-based materials, metal-based materials, conductive polymers, and mixtures thereof. In some embodiments, the carbon-based material is selected from natural graphite, artificial graphite, carbon black, acetylene black, Ketjen black, carbon fiber, or any combination thereof. In some embodiments, the metal-based material is selected from metal powder, metal fiber, copper, nickel, aluminum, or silver. In some embodiments, the conductive polymer is a polyphenylene derivative.

[0072] In some embodiments, the positive electrode sheet further includes a positive electrode current collector, which can be a metal foil or a composite current collector. For example, aluminum foil can be used. 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 polymer substrate.

[0073] In some embodiments, a separator is provided between the positive and negative electrode plates to prevent short circuits. The material and shape of the separator that can be used in the embodiments of the present application are not particularly limited and can be any known prior art material. In some embodiments, the separator comprises a polymer or inorganic material that is stable with the electrolyte of the present application.

[0074] For example, the separator may include a substrate layer and a surface treatment layer. The substrate layer is a non-woven fabric, film, or composite film having a porous structure, and the material of the substrate layer includes at least one of polyethylene, polypropylene, polyethylene terephthalate, or polyimide. Specifically, polypropylene porous film, polyethylene porous film, polypropylene non-woven fabric, polyethylene non-woven fabric, or polypropylene-polyethylene-polypropylene porous composite film can be used.

[0075] A surface treatment layer is provided on at least one surface of the substrate layer. The surface treatment layer may be a polymer layer or an inorganic layer, or a layer formed by mixing a polymer and an inorganic layer.

[0076] The inorganic layer includes inorganic particles and a binder, wherein the inorganic particles include at least one of aluminum oxide, silicon oxide, magnesium oxide, titanium oxide, hafnium dioxide, tin oxide, cerium dioxide, nickel oxide, zinc oxide, calcium oxide, zirconium oxide, yttrium oxide, silicon carbide, boehmite, aluminum hydroxide, magnesium hydroxide, calcium hydroxide, or barium sulfate. The binder includes at least one of polyvinylidene fluoride, a copolymer of vinylidene fluoride and hexafluoropropylene, polyamide, polyacrylonitrile, polyacrylate, polyacrylic acid, polyacrylate, polyvinylpyrrolidone, polyvinyl ether, polymethyl methacrylate, polytetrafluoroethylene, or polyhexafluoropropylene.

[0077] The polymer layer includes a polymer, and the polymer material includes at least one of polyamide, polyacrylonitrile, acrylate polymer, polyacrylic acid, polyacrylate, polyvinylpyrrolidone, polyvinyl ether, polyvinylidene fluoride or poly(vinylidene fluoride-hexafluoropropylene).

[0078] In some embodiments, the method for preparing the secondary battery includes providing an electrode assembly, injecting liquid, packaging, and forming. In some embodiments, the forming temperature is 40° C. to 50° C., for example, 41° C., 42° C., 43° C., 44° C., 45° C., 46° C., 47° C., 48° C., or 49° C.

[0079] In some embodiments, the formation comprises: charging to 4.25V at 0.05C current and standing for 60min, then charging to 4.25V at 0.1C current, and then discharging to 3.0V at 0.2C current under the conditions of a temperature of 40°C-50°C, for example, 45°C, and a pressure of 150kgf-250kgf, for example, 210kgf.

[0080] In some embodiments, the secondary battery is a lithium secondary battery or a sodium secondary battery. In some embodiments, the lithium secondary battery includes, but is not limited to: a lithium metal secondary battery, a lithium ion secondary battery, a lithium polymer secondary battery, or a lithium ion polymer secondary battery.

[0081] In some embodiments, the secondary battery may include an outer packaging, which may be a hard shell, such as a hard plastic shell, an aluminum shell, a steel shell, etc. The outer packaging 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 one or more of polypropylene (PP), polybutylene terephthalate (PBT), polybutylene succinate (PBS), etc.

[0082] In some embodiments, the shape of the secondary battery is not particularly limited, and it can be cylindrical, square, or any other shape.

[0083] In some embodiments, the present application also provides a battery module. The battery module includes the aforementioned secondary battery. The battery module of the present application utilizes the aforementioned secondary battery and therefore has at least the same advantages as the aforementioned secondary battery. The battery module of the present application may include multiple secondary batteries, the specific number of which can be adjusted based on the application and capacity of the battery module.

[0084] In some embodiments, the present application further provides a battery pack comprising the above-mentioned battery module. The number of battery modules contained in the battery pack can be adjusted according to the application and capacity of the battery pack.

[0085] 2. Device

[0086] The present application also provides a device comprising at least one of the above-mentioned secondary battery, battery module or battery pack.

[0087] In some embodiments, the device includes, but is not limited to, electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, power storage systems, etc. To meet the device's requirements for high power and high energy density of secondary batteries, a battery pack or battery module may be used.

[0088] In other embodiments, the device may be a mobile phone, a tablet computer, a laptop computer, etc. The device is generally required to be lightweight and thin, and may use a secondary battery as a power source.

[0089] Examples and Comparative Examples

[0090] Example 1

[0091] Preparation of the electrolyte: In an argon-protected glove box (water <1 ppm, oxygen <1 ppm), ethylene carbonate (EC), propylene carbonate (PC), and diethyl carbonate (DEC) were mixed in a mass ratio of 20:5:45, and 16% of the fluorine-containing additive fluoroethylene carbonate (FEC) and 0.25% of the boron- and / or phosphorus-containing additive tris(trimethylsilyl) phosphate (TMSP) were added to the total mass of the electrolyte. Then, lithium hexafluorophosphate (LiPF6) was added to a molar concentration of 1 mol / L, and the mixture was stirred evenly to obtain the lithium ion battery electrolyte of Example 1.

[0092] Preparation of positive electrode sheet: The ternary high-nickel active material, conductive carbon black and binder polyvinylidene chloride of the positive electrode sheet are mixed in a mass ratio of 97.5:1.5:1.0, and the mixture is dispersed in N-methylpyrrolidone NMP. After sufficient homogenization, it is coated on the two opposite surfaces of aluminum foil. After drying, calendering and vacuum drying, the positive electrode sheet is obtained.

[0093] Preparation of the negative electrode sheet: Graphite, silicon oxide, conductive carbon black, binder (styrene-butadiene rubber, polyacrylic acid) and sodium carboxymethyl cellulose CMCNa are mixed in a mass ratio of 66:30:1:2.4:0.6, and the mixture is dispersed in deionized water. After sufficient homogenization, it is coated on both surfaces of the copper foil, and then dried, calendered and vacuum dried to obtain the negative electrode sheet.

[0094] Preparation of lithium-ion battery: a three-layer diaphragm with a thickness of 11 μm (PE polyethylene porous polymer film as a diaphragm) is placed between the above positive electrode sheet and the negative electrode sheet, and then the sandwich structure consisting of the positive electrode sheet, the diaphragm and the negative electrode sheet is laminated, and then placed in an aluminum-plastic film packaging bag, vacuum baked at 75°C for 48 hours to obtain a battery cell to be injected with liquid, and the above-prepared electrolyte is injected into the battery cell, vacuum packaged, and left to stand at room temperature for 12 hours, and left to stand at a high temperature of 45°C for 12 hours, and then subjected to a capacity splitting step to obtain a lithium-ion battery; wherein the capacity splitting step is: constant current charging at 0.05C for 120 minutes, constant current and constant voltage charging at 0.1C to 4.2V, and discharging at 0.2C to 2.5V, and the formation is completed; high temperature standing for 24 hours, constant current and constant voltage charging at 0.1C to 4.2V, and constant current discharging at 0.2C to 2.5V, and two cycles are performed to complete the capacity splitting.

[0095] Examples 2 to 12 and Comparative Examples 1 to 8

[0096] Examples 2 to 12 and Comparative Examples 1 to 8 are achieved on the basis of Example 1 by adjusting the type and content of additives in the electrolyte, the formation conditions, and the content of silicon-based materials in the negative electrode sheet. Specific adjustment measures and detailed data are shown in Table 1.

[0097] Table 1

[0098] Test Method

[0099] 1. Impedance DCR test

[0100] Before the cycle capacity retention test, the lithium-ion battery was discharged at 1C constant current to 2.5V at 25±2°C, then charged at 0.5C constant current to 4.25V, and then charged at 4.25V to 0.05C constant voltage. Then, it was discharged at 1C constant current to 50% SOC. After standing for 60 minutes, the voltage U1 after the end of the standing period was recorded. Then, it was discharged at 2C constant current for 10 seconds, and the voltage U2 after the discharge was recorded. The 2C current was recorded as I, and it was stood for 60 minutes. According to the formula DCR = (U1-U2) / I, the discharge DCR (impedance) of the battery at 50% SOC was calculated.

[0101] 2. Cycle capacity retention test

[0102] At 25°C, the prepared lithium-ion secondary battery was charged at a constant current rate of 1C to 4.2V, followed by constant voltage charging until the current was less than 0.05C. After standing for 5 minutes, the battery was discharged at a rate of 1C to 2.5V, and the initial discharge capacity was recorded. The lithium-ion secondary battery was cycled 500 times using the above method, and the discharge capacity was recorded each time. The capacity retention rate of the lithium-ion secondary battery after 500 cycles at 25°C = discharge capacity at the 500th cycle / initial discharge capacity × 100%.

[0103] 3. Hot box test

[0104] Preparation stage: Place the prepared lithium-ion battery at 25±2℃ for 5 minutes; then charge it to 4.25V at 1 / 3C with a cut-off current of 1 / 20C; place it for 30 minutes; then charge it to 2.5V at 1 / 3C; place it for another 30 minutes; repeat the above steps, and finally charge it to 4.25V at 1 / 3C with a cut-off current of 1 / 20C to end charging.

[0105] Testing phase: Use a fixture to clamp the treated battery with a preload of 1.5 Nm (using 6 bolts). Place the battery in a temperature chamber, and heat the chamber from ambient temperature to 130 ± 2 °C at a rate of 5 °C / min. Maintain this temperature for 60 minutes. Then, repeat the above steps to continuously increase the chamber temperature until the battery experiences thermal runaway.

[0106] Test results

[0107] Table 2

[0108] It can be seen from Examples 1-12 and Comparative Examples 1-8 that when the content of fluorine-containing additives and the content of boron-containing and / or phosphorus-containing additives in the secondary battery electrolyte meet the preset relationship, the battery has a high capacity retention rate after 500 cycles at 25°C, and the battery impedance DCR (mΩ) and hot box pass temperature are excellent after 500 cycles at 1C at 25°C. As a result, the cycle life and hot box safety performance of high-energy-density silicon-based negative electrode batteries are improved; there is a good synergistic effect between the content of fluorine-containing additives and the content of boron-containing and / or phosphorus-containing additives. The boron-containing and / or phosphorus-containing additives can dissolve the lithium fluoride produced by the fluorine-containing additive cycle, effectively alleviating the problem of large late cycle impedance caused by a high content of fluorine-containing additives, thereby reducing the late cycle impedance, improving battery power, and further improving cycle performance and cycle life. Furthermore, when the content of fluorine-containing additives, boron-containing and / or phosphorus-containing additives, and the content of silicon-based materials of the negative electrode plates in the secondary battery electrolyte meet the preset relationship, the fluorine-containing additives, boron-containing and / or phosphorus-containing additives act together on the negative electrode plates containing silicon-based materials, making the solid electrolyte interface film (SEI film) on the surface of the negative electrode plates more dense and stable, further improving the hot box stability and cycle performance of the secondary battery.

[0109] Comparing Comparative Example 1 and Comparative Example 6, it can be seen that when the percentage of the added boron and / or phosphorus-containing additive is too low or too high, the content of the fluorine-containing additive, the content of the boron and / or phosphorus-containing additive, and the content of the negative electrode silicon-based material do not conform to the preset relationship. For example, if the content of the boron and / or phosphorus-containing additive is too low or not added, the lithium fluoride produced by the decomposition of the fluorine-containing additive cannot be effectively dissolved, thereby affecting its cycle performance and the battery's capacity retention rate is poor; if the content of the boron and / or phosphorus-containing additive is too high, it will cause excessive consumption of active lithium ions, resulting in an increase in irreversible capacity, a decrease in coulombic efficiency, and a significant increase in impedance. Comparing Comparative Example 2, Comparative Example 3, Comparative Example 5, Comparative Example 7 and Comparative Example 8, it can be seen that when the content of the fluorine-containing additive is too high or too low, the content of the fluorine-containing additive, the content of the boron and / or phosphorus-containing additive, and the content of the negative electrode silicon-based material do not conform to the preset relationship. For example, if the fluorine-containing additive content is too low or not added, the battery's capacity retention rate will be significantly reduced and the hot box pass temperature will be low; if the fluorine-containing additive content is too high, the battery's impedance will be significantly increased and the battery power will be significantly reduced. Comparing Comparative Example 4 and Comparative Example 7, it can be seen that when the silicon-based material content is too high or too low, the fluorine-containing additive content and the boron-containing and / or phosphorus-containing additive content will not meet the preset relationship, and the fluorine-containing additive content, the boron-containing and / or phosphorus-containing additive content, and the content of the silicon-based material of the negative electrode will not meet the preset relationship. For example, if the silicon-based material content is too high, the impedance will be significantly increased; if the silicon-based material content is too low, the battery's capacity retention rate will be significantly reduced, the cycle performance will be poor, and the hot box pass temperature will also be significantly reduced.

[0110] Although illustrative embodiments have been shown and described, those skilled in the art should understand that the above embodiments should not be construed as limitations on the present application, and that changes, substitutions, and modifications may be made to the embodiments without departing from the spirit, principles, and scope of the present application.

Claims

1. A secondary battery, characterized in that: include: An electrolyte comprising a fluorine-containing additive, a boron-containing additive and / or a phosphorus-containing additive; Based on the total mass of the electrolyte, the mass percentage of the fluorine-containing additive is X%, and the mass percentage of the boron-containing and / or phosphorus-containing additive is Z%; Where, -0.4≤Z+0.0005×X 2 -0.0418×X+0.3106≤0.4;12≤X≤50.

2. The secondary battery according to claim 1, characterized in that: -0.1≤Z+0.0005×X 2 -0.0418×X+0.3106≤0.1。 3. The secondary battery according to claim 1, characterized in that: 15≤X≤40。 4. The secondary battery according to claim 1, characterized in that: 0.01≤Z≤2。 5. The secondary battery according to any one of claims 1 to 4, characterized in that: 18≤X≤30。 6. The secondary battery according to any one of claims 1 to 4, characterized in that: 0.1≤Z≤1。 7. The secondary battery according to any one of claims 1 to 4, characterized in that: The secondary battery further comprises a negative electrode plate, the negative electrode plate comprises a negative electrode active material layer, the negative electrode active material of the negative electrode active material layer comprises a silicon-based material, and the mass percentage of the silicon-based material is Y% based on the total mass of the negative electrode active material; Among them, -10≤2.09×X-0.025×X 2 +0.004×Y 2 +0.016×Y-100×Z-4.738≤10.

8. The secondary battery according to claim 7, characterized in that: -5≤2.09×X-0.025×X 2 +0.004×Y 2 +0.016×Y-100×Z-4.738≤5。 9. The secondary battery according to claim 7, characterized in that: 0.5≤Y≤60。 10. The secondary battery according to claim 8 or 9, characterized in that: 10≤Y≤40。 11. The secondary battery according to any one of claims 1 to 4, characterized in that: The fluorine-containing additive includes: a fluorinated carbonate additive, and the fluorinated carbonate additive includes at least one of the compounds shown in Formula I: Wherein, in Formula I, R1, R2, R3, and R4 are independently selected from hydrogen, fluorine, substituted or unsubstituted C1-C6 alkyl, substituted or unsubstituted C1-C6 alkoxy, substituted or unsubstituted C2-C6 alkenyl, substituted or unsubstituted C2- C6 alkynyl, substituted or unsubstituted C3-C6 cycloalkyl or substituted or unsubstituted C6-C12 aryl, wherein the substituted substituents are each independently selected from fluorine, and R1, R2, R3, and R4 contain at least one fluorine.

12. The secondary battery according to any one of claims 1 to 4, characterized in that: The boron-containing and / or phosphorus-containing additive comprises: at least one of a boron-containing additive and a phosphorus-containing additive, wherein the boron-containing additive comprises at least one of the compounds shown in formula II, and the phosphorus-containing additive comprises at least one of the compounds shown in formula III and formula IV: Wherein, in Formula II, Formula III and Formula IV, R5, R6, R7, R8, R9, R 10 , R 11 , R 12 , R 13 Each is independently selected from a substituted or unsubstituted C1-C6 alkyl, a substituted or unsubstituted C1-C6 alkoxy, a substituted or unsubstituted C3-C6 alkylsilyl, a substituted or unsubstituted C2-C6 alkenyl or a substituted or unsubstituted C6-C12 aryl, wherein the substituted substituents are each independently selected from a halogen selected from fluorine, chlorine, bromine or iodine.

13. The secondary battery according to claim 11, characterized in that: In Formula I, R1, R2, R3, and R4 are independently selected from fluorine, C1-C6 alkyl, and fluorine-substituted C1-C6 alkyl, and R1, R2, R3, and R4 contain at least one fluorine.

14. The secondary battery according to claim 12, characterized in that: In Formula II, Formula III and Formula IV, R5, R6, R7, R8, R9, R 10 , R 11 , R 12 , R 13 Each is independently selected from a substituted or unsubstituted C1-C3 alkyl, a substituted or unsubstituted C3-C6 alkylsilyl, a substituted or unsubstituted C2-C3 alkenyl or a substituted or unsubstituted C6-C12 aryl, wherein the substituted substituents are each independently selected from fluorine.

15. The secondary battery according to claim 13, characterized in that: The fluorine-containing additive includes at least one of the following compounds:

16. The secondary battery according to claim 14, characterized in that: The boron-containing additive comprises at least one of the following compounds:

17. The secondary battery according to claim 14, characterized in that: The phosphorus-containing additive comprises at least one of the following compounds:

18. The secondary battery according to any one of claims 15 to 17, characterized in that: The secondary battery further satisfies at least one of the following conditions: (a) the fluorine-containing additive comprises fluoroethylene carbonate; (b) The boron-containing and / or phosphorus-containing additive comprises at least one of tris(trimethylsilyl)borate and tris(trimethylsilyl)phosphate.

19. The secondary battery according to claim 7, characterized in that: The secondary battery further satisfies at least one of the following conditions: (c) the electrolyte further includes a first additive, the first additive including at least one of a cyclic carbonate containing a carbon-carbon double bond, a nitrile compound and a pyridinium propanesulfonate, and the mass percentage of the first additive is 0.05%-10% based on the mass of the electrolyte; (d) The negative electrode active material includes the silicon-based material, or a mixture of the silicon-based material and at least one material selected from carbon-based materials, tin-based materials, phosphorus-based materials, and metallic lithium; wherein the silicon-based material includes at least one of silicon, silicon alloys, silicon oxides, and silicon carbon compounds, and the carbon-based material includes graphite, soft carbon, hard carbon, at least one of carbon nanotubes and graphene, the tin-based material comprises at least one of tin, tin oxide and tin alloy, and the phosphorus-based material comprises phosphorus and / or a phosphorus-carbon composite; (e) The secondary battery further comprises a positive electrode sheet, wherein the positive electrode sheet comprises a positive electrode active material layer, wherein the positive electrode active material of the positive electrode active material layer comprises at least one of lithium nickel transition metal oxides; wherein the lithium nickel transition metal oxide comprises LiNi x M 1-x At least one of the O2 materials, M is selected from at least one of cobalt, manganese, iron, chromium, titanium, zinc, vanadium, aluminum, zirconium and cerium, 0.1≤x≤1.

20. A device, characterized in that: The device comprises the secondary battery according to any one of claims 1 to 19.

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