Secondary battery and electronic apparatus

Abstract

A secondary battery and an electronic apparatus. The secondary battery comprises a positive electrode, a negative electrode, and an electrolyte; the negative electrode comprises a negative electrode current collector and a negative electrode material provided on the negative electrode current collector; the particle size of the negative electrode material satisfying Dv10: Dv50: Dv99 = 1: (1.5-2.5): (5-6); the electrolyte comprises diethyl carbonate, ethylene carbonate, and 1,3-propane sultone; relative to 100 parts by mass of the electrolyte, the amount of diethyl carbonate is 0.5 parts by mass to 1.5 parts by mass, the amount of ethylene carbonate is 15 parts by mass to 30 parts by mass, and the amount of 1,3-propane sultone is 0.01 parts by mass to 0.5 parts by mass. The negative electrode material and the electrolyte can improve the overcurrent and over-temperature safety of the secondary battery.

Description

Secondary batteries and electronic devices Technical Field

[0001] This application relates to the field of energy storage, specifically to a secondary battery and electronic device. Background Technology

[0002] As one of the most commercially successful research directions, rechargeable batteries are facing increasing market demands for performance as electronic products and electric vehicles are updated and iterated.

[0003] Specifically, the diversification of product usage scenarios poses increasing challenges to the safety of secondary batteries. The fast pace of urban life has led to higher expectations for the over-temperature and over-current safety of secondary batteries. Therefore, the positive electrode, negative electrode, and electrolyte, as crucial components of secondary batteries, bear the responsibility of improving battery safety. Improving the materials of the positive electrode, negative electrode, and electrolyte, and exploring the compatibility between these components, has become a highly valuable research direction. Summary of the Invention

[0004] This application improves the overcurrent and overtemperature safety of a secondary battery by regulating the negative electrode material and electrolyte in the secondary battery. The inventors of this application discovered that a secondary battery includes a positive electrode, a negative electrode, and an electrolyte. The negative electrode includes a negative electrode current collector and a negative electrode material disposed on the negative electrode current collector. The particle size of the negative electrode material satisfies Dv10:Dv50:Dv99=1:(1.5~2.5):(5~6). The electrolyte includes diethyl carbonate, ethylene carbonate, and 1,3-propanesulfonate lactone. Relative to 100 parts by mass of the electrolyte, diethyl carbonate is 0.5 to 1.5 parts by mass, ethylene carbonate is 15 to 30 parts by mass, and 1,3-propanesulfonate lactone is 0.01 to 0.5 parts by mass. This method can improve the overcurrent and overtemperature safety of the battery, thus completing this application.

[0005] In some embodiments, the mass ratio of diethyl carbonate, ethylene carbonate and 1,3-propanesulfonate lactone is (20-30):(400-500):(1-3).

[0006] In some embodiments, the electrolyte further includes methylene methanedisulfonate and propylene-1,3-sulfonyl lactone, wherein the sum of methylene methanedisulfonate and propylene-1,3-sulfonyl lactone is 0.02 to 1.8 parts by mass relative to 100 parts by mass of the electrolyte.

[0007] In some embodiments, the electrolyte further includes tetramethylborate, wherein the tetramethylborate is 1 to 1.5 parts by weight relative to 100 parts by weight of the electrolyte.

[0008] In some embodiments, the positive electrode includes a positive current collector and a positive electrode material disposed on the positive current collector, the positive electrode material including lithium cobalt oxide.

[0009] In some embodiments, the cathode material also includes one or both of molybdenum and iron.

[0010] In some embodiments, the molybdenum content is between 100 ppm and 2000 ppm by mass, and the iron content is between 100 ppm and 3000 ppm by mass, depending on the mass of the cathode material.

[0011] In some embodiments, the negative electrode material includes silicon-based materials.

[0012] In some embodiments, the silicon-based material includes a composite of silicon-based and carbon-based materials.

[0013] In another aspect of this application, an electronic device is provided that includes the secondary battery described in this application.

[0014] This application improves the overcurrent and overtemperature safety of secondary batteries through a specific combination of negative electrode and electrolyte.

[0015] Additional aspects and advantages of the embodiments of this application will be described, shown, or illustrated in part by way of implementation of the embodiments of this application in the following description. Detailed Implementation

[0016] The embodiments of this application will be described in detail below. These embodiments should not be construed as limiting the scope of this application.

[0017] Unless otherwise expressly stated, the terms used in this application shall have the meanings indicated below.

[0018] This application improves the overcurrent and overtemperature safety of secondary batteries by using a preset negative electrode combined with a preset electrolyte.

[0019] In one embodiment, this application provides a secondary battery comprising a positive electrode, a negative electrode, and an electrolyte as described below.

[0020] electrolyte

[0021] This application relates to a secondary battery and an electronic device. Specifically, this application provides a secondary battery comprising: a positive electrode, a negative electrode, and an electrolyte. The electrolyte used in the secondary battery of this application comprises an electrolyte and a solvent for dissolving the electrolyte. The electrolyte comprises diethyl carbonate, ethylene carbonate, and 1,3-propanesulfonate lactone. Relative to 100 parts by mass of the electrolyte, diethyl carbonate comprises 0.5 to 1.5 parts by mass, ethylene carbonate comprises 15 to 30 parts by mass, and 1,3-propanesulfonate lactone comprises 0.01 to 0.5 parts by mass. The negative electrode comprises a negative electrode current collector and a negative electrode material disposed on the negative electrode current collector. The particle size of the negative electrode material satisfies Dv10:Dv50:Dv99 = 1:(1.5-2.5):(5-6). For example, relative to 100 parts by mass of electrolyte, the mass fraction of diethyl carbonate can be 0.5, 0.6, 0.7, 0.8, 0.9, 1.0, 1.1, 1.2, 1.3, 1.4, 1.5 or any value within the range of any two of the above values; the mass fraction of ethylene carbonate can be 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30 or any value within the range of any two of the above values; and the mass fraction of 1,3-propanesulfonate lactone can be 0.01, 0.03, 0.05, 0.08, 0.10, 0.15, 0.20, 0.25, 0.30, 0.35, 0.40, 0.45, 0.50 or any value within the range of any two of the above values. For example, the particle sizes Dv10, Dv50, and Dv99 of the negative electrode material satisfy the following: when Dv10 is counted as 1, Dv50 can be 1.5, 1.6, 1.7, 1.8, 1.9, 2.0, 2.1, 2.2, 2.3, 2.4, 2.5, or any value within the range of any two of the above values; and Dv90 can be 5.0, 5.1, 5.2, 5.3, 5.4, 5.5, 5.6, 5.7, 5.8, 5.9, 6.0, or any value within the range of any two of the above values.

[0022] When using pre-defined amounts of diethyl carbonate, ethylene carbonate, and 1,3-propanesulfonate lactone in the secondary battery of this application, the inventors discovered that, synergistically with the negative electrode material of the pre-defined particle size in this application, they can improve the overcurrent and overtemperature safety of the secondary battery. It is speculated that this is because, within the content range defined in this application, diethyl carbonate, ethylene carbonate, and 1,3-propanesulfonate lactone can synergistically improve the elasticity and uniformity of the negative electrode interface film with the negative electrode material of the specific particle size in this application, thereby improving the safety of the secondary battery under some overload conditions such as overcurrent and overtemperature. Therefore, this application can improve the overcurrent and overtemperature safety of the secondary battery by using a pre-defined negative electrode combined with a pre-defined electrolyte.

[0023] Specifically, from the perspective of improving the overcurrent and overtemperature safety of secondary batteries, the mass ratio of diethyl carbonate, ethylene carbonate and 1,3-propanesulfonate lactone is (20-30):(400-500):(1-3). For example, the mass contents of diethyl carbonate, ethylene carbonate, and 1,3-propanesulfonate lactone meet the following conditions: when diethyl carbonate is 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, or 30, or any value within the range of any two of the above values; when ethylene carbonate is 400, 410, 420, 430, 440, 450, 460, 470, 480, 490, or 500, or any value within the range of any two of the above values; and when 1,3-propanesulfonate lactone is 1.0, 1.2, 1.4, 1.6, 1.8, 2.0, 2.2, 2.4, 2.6, 2.8, or 3, or any value within the range of any two of the above values. Meeting these conditions helps to further improve overcurrent and overtemperature safety.

[0024] Specifically, from the viewpoint of improving the overcurrent and overtemperature safety of secondary batteries, the electrolyte also includes methylene methane disulfonate and propylene-1,3-sulfonyl lactone. The sum of methylene methane disulfonate and propylene-1,3-sulfonyl lactone is 0.02 to 1.8 parts by mass relative to 100 parts by mass of the electrolyte. For example, the sum of methylene methane disulfonate and propylene-1,3-sulfonyl lactone can be 0.02, 0.06, 0.10, 0.50, 1.00, 1.10, 1.20, 1.30, 1.40, 1.50, 1.60, 1.70, 1.80, or any value within the range of any two of the above values, relative to 100 parts by mass of the electrolyte. Meeting the above conditions helps to further improve overcurrent and overtemperature safety.

[0025] Specifically, in some embodiments, the electrolyte further includes tetramethylborate, wherein the tetramethylborate content is 1 to 1.5 parts by weight relative to 100 parts by weight of the electrolyte. For example, the mass fraction of tetramethylborate relative to 100 parts by weight of the electrolyte can be 1.00, 1.05, 1.10, 1.15, 1.20, 1.25, 1.30, 1.35, 1.40, 1.45, 1.50, or any value within the range of any two of the above values. When the above conditions are met, it helps to further improve the overcurrent and overtemperature safety of the secondary battery.

[0026] In some embodiments, the electrolyte contains one or more of the following substances: ethylene glycol sulfate, 1,2-propanediol sulfate, 1,3-propanediol sulfate, 1,2-butanediol sulfate, 1,3-butanediol sulfate, 1,4-butanediol sulfate, 1,2-pentanediol sulfate, 1,3-pentanediol sulfate, 1,4-pentanediol sulfate, 1,5-pentanediol sulfate, dimethyl sulfate, methyl ethyl sulfate, methyl fluorosulfonate, ethyl trifluoromethanesulfonate, methyl methanesulfonate, ethyl methanesulfonate, and dimethanesulfonic acid. Butyl acetate, methyl 2-(methanesulfonyloxy)propionate, ethyl 2-(methanesulfonyloxy)propionate, 1-fluoro-1,3-propanesulfonic acid lactone, 2-fluoro-1,3-propanesulfonic acid lactone, 3-fluoro-1,3-propanesulfonic acid lactone, 1-methyl-1,3-propanesulfonic acid lactone, 2-methyl-1,3-propanesulfonic acid lactone, 3-methyl-1,3-propanesulfonic acid lactone, 2-propene-1,3-sulfonic acid lactone, 1-fluoro-1-propene-1,3-sulfonic acid lactone, 2-fluoro-1-propene-1,3-sulfonic acid lactone, 3-fluoro-1-propene-1,3-sulfonic acid lactone, 1,3-Synolactone, 1-Fluoro-2-propen-1,3-Synolactone, 2-Fluoro-2-propen-1,3-Synolactone, 3-Fluoro-2-propen-1,3-Synolactone, 1-Methyl-1-propen-1,3-Synolactone, 2-Methyl-1-propen-1,3-Synolactone, 3-Methyl-1-propen-1,3-Synolactone, 1-Methyl-2-propen-1,3-Synolactone, 2-Methyl-2-propen-1,3-Synolactone, 3-Methyl-2-propen-1,3-Synolactone Oxylactone, 1,4-butyrolactone, 1,5-pentanesulfonate lactone, ethylene methanedisulfonate, dimethyl sulfite, methyl ethyl sulfite, lithium difluorophosphate, 1,2-ethylene glycol sulfite, 1,2-propanediol sulfite, 1,3-propanediol sulfite, 1,2-butanediol sulfite, 1,3-butanediol sulfite, 1,4-butanediol sulfite, 1,2-pentanediol sulfite, 1,3-pentanediol sulfite, 1,4-pentanediol sulfite, and 1,5-pentanediol sulfite, etc.

[0027] In some embodiments, the electrolyte further includes an ionizable lithium salt, which includes at least one selected from LiPF6, LiSbF6, LiAsF6, LiClO4, LiN(C2F5SO2)2, CF3SO3Li, LiC(CF3SO2)3, and LiC4BO8. For example, the lithium salt used in the electrolyte of this application includes LiPF6, and the mass percentage of LiPF6 is 9% to 15%, preferably 9% to 13%, and more preferably 9% to 12%, based on the mass of the electrolyte. Meeting the above conditions can further improve the overcurrent and overtemperature safety of the secondary battery.

[0028] In some embodiments, the electrolyte further includes at least one of lithium difluorophosphate (LiPO2F2), lithium difluorooxalate borate (LiDFOB), lithium bis(oxalate borate) (LiBOB), lithium tetrafluoroborate (LiBF4), lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), and lithium bis(fluorosulfonyl)imide (LiFSI).

[0029] In some embodiments, the additives in the electrolyte also include at least one of fluoroether compounds, fluorocarbonate compounds and ether nitrile compounds, such as hydrofluoroether (HFE-458), fluoroethylene carbonate (FEC), etc.

[0030] In some embodiments, the electrolyte may also include a non-aqueous solvent. The non-aqueous solvent may be selected from carbonate compounds, carboxylic acid ester compounds, ether compounds, phosphate ester compounds, other organic solvents, or combinations thereof.

[0031] Optionally, the carbonate compound may be a chain carbonate compound, a cyclic carbonate compound, or a combination thereof. On the other hand, the carbonate compound may also be a fluorinated carbonate compound, a non-fluorinated carbonate compound, or a combination thereof.

[0032] Specifically, examples of chain carbonate compounds are diethyl carbonate (DEC), dimethyl carbonate (DMC), dipropyl carbonate (DPC), methyl propyl carbonate (MPC), ethyl propyl carbonate (EPC), and combinations thereof. Examples of cyclic carbonate compounds are ethylene carbonate (EC), propylene carbonate (PC), butyl carbonate (BC), vinyl ethylene carbonate (VEC), or combinations thereof. Examples of fluorinated carbonate compounds are fluoroethylene carbonate (FEC), 1,2-difluoroethylene carbonate, 1,1-difluoroethylene carbonate, 1,1,2-trifluoroethylene carbonate, 1,1,2,2-tetrafluoroethylene carbonate, 1-fluoro-2-methylethylene carbonate, 1-fluoro-1-methylethylene carbonate, 1,2-difluoro-1-methylethylene carbonate, 1,1,2-trifluoro-2-methylethylene carbonate, trifluoromethylethylene carbonate, or combinations thereof.

[0033] Specifically, examples of carboxylic acid ester compounds are methyl acetate, ethyl acetate, n-propyl acetate, tert-butyl acetate, methyl propionate, ethyl propionate, propyl propionate, γ-butyrolactone, decanoic acid lactone, valerate lactone, mevalonic acid lactone, caprolactone, methyl formate, or combinations thereof.

[0034] Specifically, examples of ether compounds are dibutyl ether, tetraethylene glycol dimethyl ether, diethylene glycol dimethyl ether, 1,2-dimethoxyethane, 1,2-diethoxyethane, ethoxymethoxyethane, 2-methyltetrahydrofuran, tetrahydrofuran, or combinations thereof.

[0035] Specifically, examples of phosphate ester compounds are trimethyl phosphate, triethyl phosphate, trioctyl phosphate, or combinations thereof.

[0036] Specifically, examples of other organic solvents include dimethyl sulfoxide, 1,2-dioxolane, sulfolane, methyl sulfolane, 1,3-dimethyl-2-imidazolium ketone, N-methylpyrrolidone, formamide, dimethylformamide, acetonitrile, or combinations thereof.

[0037] negative electrode

[0038] The negative electrode includes a negative electrode current collector and a negative electrode material disposed on the surface of the negative electrode current collector. The particle size of the negative electrode material in this application satisfies Dv10:Dv50:Dv99=1:(1.5~2.5):(5~6).

[0039] In some embodiments, the rechargeable capacity of the negative electrode material is greater than the discharge capacity of the positive electrode material to reduce the unintentional deposition of lithium metal on the negative electrode during charging.

[0040] In some embodiments, the anode material includes carbon-based anode materials, metal-based anode materials, and anode materials combining these.

[0041] Here, carbon-based anode materials refer to active materials with carbon as the main framework that can insert lithium. Examples of carbon-based anode materials include carbonaceous materials and graphitic materials.

[0042] Examples of carbonaceous materials include easily graphitized carbon and difficult-to-graphitize carbon. Among easily graphitized carbons are carbon materials derived from petroleum or coal using tar pitch as a raw material; specific examples include coke, mesophase carbon microspheres (MCMB), mesophase pitch-based carbon fibers, and pyrolysis-grown carbon fibers. Furthermore, examples of difficult-to-graphitize carbons include carbon materials with amorphous structures, such as glassy carbon; specific examples include phenolic resin sintered bodies, polyacrylonitrile-based carbon fibers, quasi-isotropic carbon, furfuryl alcohol resin sintered bodies (PFA), and hard carbon.

[0043] Furthermore, examples of graphitic materials include natural graphite and artificial graphite. Among these, examples of artificial graphite include: artificial graphite formed by heat-treating carbon containing easily graphitizable carbon primarily at 2800°C or higher; graphitic MCMB formed by heat-treating MCMB at 2000°C or higher; and graphitic mesophase pitch-based carbon fiber formed by heat-treating mesophase pitch-based carbon fiber at 2000°C or higher. Additionally, in this invention application, as a carbon-based negative electrode material, natural graphite whose surface is at least partially coated with amorphous carbon (amorphously coated natural graphite) can be used.

[0044] In addition, the metal-based negative electrode material is an active material containing a metal, and generally refers to an active material that contains an element capable of inserting lithium or alloying with lithium in its structure and has a theoretical current capacity of 500 mAh / g or more per unit mass when inserting lithium or alloying with lithium. As the metal-based negative electrode material, for example, lithium metal, elemental metals capable of forming lithium alloys (such as Ag, Al, Ba, Bi, Cu, Ga, Ge, In, Ni, P, Pb, Sb, Si, Sn, Sr, Zn, and Ti, etc.), their alloys, as well as their oxides, sulfides, nitrides, silicides, carbides, phosphides, etc. can be used. Among them, as the metal-based negative electrode material, an active material containing silicon (silicon-based negative electrode material) is preferred. This is because the use of the silicon-based negative electrode material can increase the capacity of the secondary battery.

[0045] In some embodiments, the negative electrode material includes a silicon-based material.

[0046] In some embodiments, the silicon-based material includes at least one of a composite of a silicon-based substance and a carbon-based substance and silicon oxide (SiOx, 0 < x ≤ 2). The silicon-based substance can be silicon particles, silicon alloy particles, etc. The negative electrode material may further include a carbon material, and the carbon material can be crystalline carbon, amorphous carbon, or a mixture thereof. The crystalline carbon can be graphite, such as amorphous, plate-like, flaky, spherical or fibrous natural graphite and / or artificial graphite, and the amorphous carbon can be soft carbon (low-temperature calcined carbon), hard carbon, mesophase pitch carbide, or calcined coke, etc.

[0047] The composite of the silicon-based substance and the carbon-based substance can be a composite having a structure in which silicon nanoparticles are arranged on the carbon-based substance, a composite in which silicon particles are included on the surface and inside of the carbon-based substance, and a composite in which silicon particles are coated with the carbon-based substance and are included in the carbon-based substance. In the composite of the silicon-based substance and the carbon-based substance, the carbon-based substance can be graphite, graphene, graphene oxide, or a combination thereof.

[0048] The composite of the silicon-based substance and the carbon-based substance can be an active material obtained by dispersing silicon nanoparticles with an average particle size of 200 nm or less on carbon-based substance particles and then coating them with carbon, an active material in which silicon (Si) particles are present on and inside graphite, etc.

[0049] From the viewpoint of improving the battery capacity, silicon-carbon materials, such as composites of porous carbon loaded with silicon, are preferred.

[0050] In addition, the negative electrode material can be used alone or two or more kinds can be used in any ratio in combination.

[0051] The negative electrode may also include a negative electrode binder. The negative electrode binder improves the bonding between negative electrode material particles and the bonding between the negative electrode material and the current collector. There are no particular limitations on the type of negative electrode binder, as long as it is a material stable to the electrolyte or the solvent used in electrode manufacturing. In some embodiments, the negative electrode binder includes a resin binder. Examples of resin binders include, but are not limited to, fluoropolymers, polyacrylonitrile (PAN), polyimide resins, acrylic resins, and polyolefin resins. When preparing the negative electrode slurry using an aqueous solvent, the negative electrode binder includes, but is not limited to, carboxymethyl cellulose (CMC) or its salts, styrene-butadiene rubber (SBR), polyacrylic acid (PAA) or its salts, and polyvinyl alcohol.

[0052] The negative electrode may also include a negative electrode conductive material. For example, negative electrode conductive materials include, but are not limited to, carbon-based materials, metal-based materials, conductive polymers, or any combination thereof. In some embodiments, carbon-based materials include, but are not limited to, natural graphite, artificial graphite, carbon black, acetylene black, Ketjen black, carbon fiber, or any combination thereof. In some embodiments, metal-based materials include, but are not limited to, metal powders or metal fibers, such as copper, nickel, aluminum, or silver. In some embodiments, the conductive polymer may be a polyphenylene derivative.

[0053] As the current collector for retaining the negative electrode material, any known current collector can be used. Examples of negative electrode current collectors include, but are not limited to, metallic materials such as copper, nickel, stainless steel, and nickel-plated steel. In some embodiments, the negative electrode current collector is copper. In some embodiments, the negative electrode current collector is a composite current collector, namely a 12μm composite copper foil (commercially available, a composite current collector made by depositing metallic copper layers on both sides of polyethylene terephthalate (PET) as the base material using an advanced vacuum deposition process).

[0054] The negative electrode can be prepared by coating a negative electrode slurry containing negative electrode material, resin binder, etc. onto a negative electrode current collector, drying it, and then calendering it to form a negative electrode material layer on both sides of the negative electrode current collector, thereby obtaining the negative electrode.

[0055] positive electrode

[0056] The positive electrode includes a positive current collector and a positive electrode material disposed on the surface of the positive current collector.

[0057] The cathode material can be one or more layers. Each layer in a multilayer cathode material can contain the same or different cathode active materials. The cathode active material is any material capable of reversibly inserting and deintercalating lithium ions.

[0058] Specifically, in some embodiments, the positive electrode includes a positive current collector and a positive electrode material disposed on the positive current collector, wherein the positive electrode material includes lithium cobalt oxide. When the above conditions are met, it helps to further improve the overcurrent and overtemperature safety of the secondary battery.

[0059] Specifically, from the perspective of improving the overcurrent and overtemperature safety of secondary batteries, lithium cobalt oxide cathode materials also include one or both of molybdenum and iron. Meeting the above conditions can further improve the overcurrent and overtemperature safety of secondary batteries.

[0060] Specifically, from the perspective of improving the overcurrent and overtemperature safety of secondary batteries, based on the quality of the cathode material, the mass content of molybdenum is 100ppm to 2000ppm, and the mass content of iron is 100ppm to 3000ppm. For example, based on the mass of the cathode material, the molybdenum content can be 100ppm, 200ppm, 300ppm, 400ppm, 500ppm, 600ppm, 700ppm, 800ppm, 900ppm, 1000ppm, 1200ppm, 1400ppm, 1600ppm, 1800ppm, 2000ppm, or any value within the range of any two of the above values. The iron content can be 100ppm, 300ppm, 500ppm, 800ppm, 1000ppm, 1200ppm, 1500ppm, 1800ppm, 2000ppm, 2200ppm, 2500ppm, 2800ppm, 3000ppm, or any value within the range of any two of the above values. Meeting these conditions can further improve the overcurrent and overtemperature safety of the secondary battery.

[0061] Specifically, in some other embodiments, the positive electrode active material comprises a lithium transition metal oxide containing nickel and other transition metals. In the lithium transition metal oxide comprising nickel and other transition metals, the amount of nickel may be 60 mol% or more, for example, 75 mol% or more, for example, 80 mol% or more, for example, 85 mol% or more, or for example, 90 mol% or more, relative to the total moles of the transition metals.

[0062] For example, lithium transition metal oxides can be compounds represented by the following formula 1:

[0063] Formula 1: Li a Ni x Co y M z O 2-b A b, where 0.9 ≤ a ≤ 1.2, 0 ≤ b ≤ 0.2, 0.6 ≤ x < 1, 0 < y ≤ 0.3, 0 < z ≤ 0.3, and x + y + z = 1, M is at least one selected from manganese (Mn), vanadium (V), magnesium (Mg), gallium (Ga), silicon (Si), tungsten (W), molybdenum (Mo), iron (Fe), chromium (Cr), copper (Cu), zinc (Zn), titanium (Ti), aluminum (Al), or boron (B), and A is F, S, Cl, Br, or a combination thereof. For example, the above subscripts can be 0.7 ≤ x < 1, 0 < y ≤ 0.3, and 0 < z ≤ 0.3; 0.8 ≤ x < 1, 0 < y ≤ 0.3, and 0 < z ≤ 0.3; 0.8 ≤ x < 1, 0 < y ≤ 0.2, and 0 < z ≤ 0.2; 0.83 ≤ x < 0.97, 0 < y ≤ 0.15, and 0 < z ≤ 0.15; or 0.85 ≤ x < 0.95, 0 < y ≤ 0.1, and 0 < z ≤ 0.1.

[0064] For example, the lithium transition metal oxide can be at least one compound represented by Formula 2 or Formula 3 below:

[0065] Formula 2: LiNi x Co y Mn z O2, where 0.6 ≤ x ≤ 0.95, 0 < y ≤ 0.2, and 0 < z ≤ 0.1. For example, 0.7 ≤ x ≤ 0.95, 0 < y ≤ 0.3, and 0 < z ≤ 0.3.

[0066] Formula 3: LiNi x Co y Al z O2, where 0.6 ≤ x ≤ 0.95, 0 < y ≤ 0.2, and 0 < z ≤ 0.1. For example, 0.7 ≤ x ≤ 0.95, 0 < y ≤ 0.3, and 0 < z ≤ 0.3. For example, 0.8 ≤ x ≤ 0.95, 0 < y ≤ 0.3, and 0 < z ≤ 0.3. For example, 0.82 ≤ x ≤ 0.95, 0 < y ≤ 0.15, and 0 < z ≤ 0.15. For example, 0.85 ≤ x ≤ 0.95, 0 < y ≤ 0.1, and 0 < z ≤ 0.1.

[0067] For example, the lithium transition metal oxide can be LiNi 0.6 Co 0.2 Mn 0.2 O2, LiNi 0.88 Co 0.08 Mn 0.04 O2, LiNi 0.8 Co 0.15 Mn 0.05 O2, LiNi 0.8 Co 0.1 Mn 0.1 O2, LiNi0.88 Co 0.1 Mn 0.02 O2, LiNi 0.8 Co 0.15 Al 0.05 O2, LiNi 0.8 Co 0.1 Al 0.1 O2 or LiNi 0.88 Co 0.1 Al 0.02 O2.

[0068] According to another embodiment, the positive electrode active material includes at least one active material selected from the group consisting of: Li-Ni-Co-Al (NCA), Li-Ni-Co-Mn (NCM), lithium cobalt oxide (LiCoO2), lithium manganese oxide (LiMnO2), lithium nickel oxide (LiNiO2), and lithium iron phosphate (LiFePO4).

[0069] In some embodiments, the positive electrode further includes a positive electrode conductive material. There is no limitation on the type of positive electrode conductive material; any known conductive material can be used. Examples of positive electrode conductive materials include, but are not limited to, acetylene black, Super-P carbon black, amorphous carbon such as needle coke, carbon nanotubes, and graphene. The above-mentioned positive electrode conductive materials can be used alone or in any combination.

[0070] In some embodiments, the positive electrode also includes a positive electrode binder. There are no particular limitations on the type of positive electrode binder; in the case of a coating method, any material that is soluble or dispersible in the liquid medium used during electrode manufacturing is acceptable. Examples of positive electrode adhesives may include, but are not limited to, one or more of the following: resin-based polymers such as polyethylene, polypropylene, polyethylene terephthalate, polymethyl methacrylate, polyimide, aromatic polyamide, cellulose, and nitrocellulose; rubber-like polymers such as styrene-butadiene rubber (SBR), nitrile rubber (NBR), fluororubber, isoprene rubber, polybutadiene rubber, and ethylene-propylene rubber; thermoplastic elastomer-like polymers such as styrene-butadiene-styrene block copolymers or their hydrides, ethylene-propylene-diene terpolymers (EPDM), styrene-ethylene-butadiene-ethylene copolymers, and styrene-isoprene-styrene block copolymers or their hydrides; soft resin-like polymers such as syndiotactic-1,2-polybutadiene, polyvinyl acetate, ethylene-vinyl acetate copolymers, and propylene-α-olefin copolymers; fluorinated polymers such as polyvinylidene fluoride (PVDF), polytetrafluoroethylene, fluorinated polyvinylidene fluoride, and polytetrafluoroethylene-ethylene copolymers; and polymer compositions with ion conductivity of alkali metal ions (especially lithium ions). The above-mentioned positive electrode adhesive can be used alone or in any combination.

[0071] In some embodiments, the positive electrode further includes a solvent for forming the positive electrode slurry. There is no limitation on the type of solvent used to form the positive electrode slurry, as long as it is capable of dissolving or dispersing the positive electrode active material, conductive material, positive electrode binder, and thickener used as needed. Examples of solvents used to form the positive electrode slurry may include any of aqueous solvents and organic solvents. Examples of aqueous media may include, but are not limited to, mixtures of alcohol and water or water. Examples of organic media may include, but are not limited to, aliphatic hydrocarbons such as hexane; aromatic hydrocarbons such as benzene, toluene, xylene, and methylnaphthalene; heterocyclic compounds such as quinoline and pyridine; ketones such as acetone, methyl ethyl ketone, and cyclohexanone; esters such as methyl acetate and methyl acrylate; amines such as diethylenetriamine and N,N-dimethylaminopropylamine; ethers such as diethyl ether, propylene oxide, and tetrahydrofuran (THF); amides such as N-methylpyrrolidone (NMP), dimethylformamide, and dimethylacetamide; and aprotic polar solvents such as hexamethylphosphoramide and dimethyl sulfoxide.

[0072] In some embodiments, the positive electrode also includes a thickener. Thickeners are typically used to adjust the viscosity of the slurry. In the case of using an aqueous medium, a thickener and a styrene-butadiene rubber (SBR) emulsion can be used for slurry preparation. There are no particular limitations on the type of thickener, and examples include, but are not limited to, carboxymethyl cellulose, methyl cellulose, hydroxymethyl cellulose, ethyl cellulose, polyvinyl alcohol, oxidized starch, phosphorylated starch, casein, and their salts. The aforementioned thickeners can be used alone or in any combination.

[0073] There are no particular limitations on the type of positive electrode current collector; it can be any material known to be suitable for use as a positive electrode current collector. Examples of positive electrode current collectors include, but are not limited to, metallic materials such as aluminum, stainless steel, nickel plating, titanium, and tantalum; and materials such as carbon cloth and carbon paper. In some embodiments, the positive electrode current collector is a metallic material. In some embodiments, the positive electrode current collector is aluminum.

[0074] To reduce the electronic contact resistance between the positive current collector and the positive electrode material, the surface of the positive current collector may include a conductive additive or a conductive coating. Examples of conductive additives include, but are not limited to, noble metals such as carbon, gold, platinum, and silver. Examples of conductive coatings may include a mixture layer containing inorganic oxides, conductive agents, and binders.

[0075] The positive electrode can be manufactured by forming a positive electrode material containing a positive electrode active material and a binder on a current collector. The manufacture of a positive electrode using a positive electrode active material can be carried out by conventional methods, namely, dry mixing the positive electrode active material, binder, and conductive materials and thickeners as needed, forming a sheet, and pressing the resulting sheet onto the positive electrode current collector; or dissolving or dispersing these materials in a liquid medium to form a slurry, coating the slurry onto the positive electrode current collector and drying it, thereby forming the positive electrode material on the current collector, thus obtaining the positive electrode.

[0076] Separating membrane

[0077] To prevent short circuits, a separator is typically placed between the positive and negative electrodes. In this case, the electrolyte of this application is typically used after penetrating into the separator.

[0078] There are no particular limitations on the material and shape of the separator, as long as it does not significantly impair the effectiveness of this application. The separator can be a resin, glass fiber, inorganic material, etc., formed from a material that stabilizes the electrolyte of this application. In some embodiments, the separator includes porous sheets with excellent liquid retention properties and non-woven fabric-like materials. Examples of materials for resin or glass fiber separators include, but are not limited to, polyolefins, aromatic polyamides, polytetrafluoroethylene, and polyethersulfone. In some embodiments, the polyolefin is polyethylene or polypropylene. In some embodiments, the polyolefin is polypropylene. The above-mentioned separator materials can be used alone or in any combination.

[0079] The release membrane can also be a material formed by laminating the above-mentioned materials, examples of which include, but are not limited to, a three-layer release membrane formed by laminating polypropylene, polyethylene, and polypropylene in that order.

[0080] Examples of inorganic materials include, but are not limited to, oxides such as alumina and silicon dioxide, nitrides such as aluminum nitride and silicon nitride, and sulfates (e.g., barium sulfate, calcium sulfate, etc.). Inorganic materials may be in the form of, but are not limited to, particulates and fibrous materials.

[0081] The separator can be in the form of a thin film, examples of which include, but are not limited to, nonwoven fabrics, woven fabrics, and microporous membranes. In the thin film form, the pore size of the separator is 0.01 μm to 1 μm, and the thickness is 5 μm to 50 μm. In addition to the above-mentioned independent thin film separators, the following separators can also be used: separators formed by using a resin-based adhesive to form a composite porous layer containing the above-mentioned inorganic particles on the surface of the positive and / or negative electrodes. For example, a separator formed by using fluororesin as an adhesive to form a porous layer of alumina particles with a particle size of less than 1 μm on both sides of the positive electrode.

[0082] The thickness of the separator is arbitrary. In some embodiments, the thickness of the separator is greater than or equal to 1 μm, greater than or equal to 5 μm, or greater than or equal to 8 μm. In some embodiments, the thickness of the separator is less than or equal to 50 μm, less than or equal to 40 μm, or less than or equal to 30 μm. When the thickness of the separator is within the above ranges, it is beneficial to improve insulation and mechanical strength, and also beneficial to improve the DC resistance characteristics and energy density of the secondary battery.

[0083] This application also provides an electronic device that includes a secondary battery as described in this application.

[0084] The application of the secondary battery in this application is not particularly limited, and it can be used in any electronic device known in the prior art. In some embodiments, the secondary battery of this application can be used in, but is not limited to, laptops, pen input computers, mobile computers, e-book players, portable telephones, portable fax machines, portable copiers, portable printers, headphones, video recorders, LCD TVs, portable cleaners, portable CD players, mini CDs, transceivers, electronic notebooks, calculators, memory cards, portable recorders, radios, backup power supplies, motors, automobiles, motorcycles, electric bicycles, bicycles, lighting fixtures, toys, game consoles, clocks, power tools, flashlights, cameras, household large-capacity batteries, and lithium-ion capacitors, etc.

[0085] The following examples illustrate embodiments of the secondary battery of this application, but this application is not limited to these embodiments. Unless otherwise stated, reagents, software, and instruments involved in the following examples that are not specifically described are all conventional commercially available products or open-source products.

[0086] Preparation of secondary batteries

[0087] 1. Positive Electrode Fabrication: The positive electrode material (97 wt%), conductive carbon black (1.5 wt%), and polyvinylidene fluoride (1.5 wt%) shown in Table 1 were dissolved in N-methylpyrrolidone and mixed to prepare a positive electrode slurry. The positive electrode slurry was uniformly coated onto one surface of a 10 μm thick aluminum foil used as a positive electrode current collector. The aluminum foil was dried at 120°C to obtain a positive electrode sheet with an 80 μm thick positive electrode material layer coated on one side. The above steps were repeated on the other surface of the aluminum foil to obtain a positive electrode sheet with a double-sided coating of the positive electrode material layer. The coated aluminum foil was dried, pressurized, and then cut to the specified size to fabricate the positive electrode.

[0088] 2. Separating membrane: A 12μm thick polyethylene (PE) microporous membrane is selected as the separating membrane.

[0089] 3. Anode Fabrication: The anode material shown in Table 1 (96 wt%) and styrene-butadiene rubber (2 wt%) are mixed and added to a solution obtained by dissolving lithium carboxymethyl cellulose (2 wt%) in deionized water. This mixture is then used to prepare the anode slurry. The anode slurry is coated onto one side of a copper foil, dried, pressure-treated, and then cut to the specified size to fabricate the anode. This application does not impose any particular limitations on the method for controlling the particle size of the anode material, as long as it achieves the purpose of this application. For example, anode materials of different particle sizes can be obtained through mechanical crushing, grinding, sieving, etc.

[0090] 4. Electrolyte preparation: In an argon atmosphere glove box with a water content of less than 10 ppm, ethylene carbonate (content as per Table 1), dimethyl carbonate, and methyl ethyl carbonate (dimethyl carbonate and methyl ethyl carbonate in a mass ratio of 0.5:4) are mixed to obtain a basic solvent. Then, lithium salt LiPF6 and other substances in the electrolyte shown in Table 1 are added to the above basic solvent and mixed evenly to obtain the electrolyte. The mass content of LiPF6 is 14.5% based on the mass of the electrolyte.

[0091] 5. Battery Fabrication: The positive electrode, separator, and negative electrode are stacked sequentially, with the separator acting as a barrier between the positive and negative electrodes. The electrode assembly is then wound up. After welding the tabs, the electrode assembly is placed in an outer aluminum-plastic film package. Moisture is removed at 80°C, and the electrolyte is injected. Following vacuum sealing, settling, formation, shaping, and capacity testing, a lithium-ion battery is obtained. This secondary battery is a pouch-shaped device measuring 30mm wide, 45mm high, and 5mm thick.

[0092] Test methods

[0093] 1. Particle size testing method: Refer to GB / T19077-2016. The specific procedure is as follows: Weigh 1g of sample and mix it thoroughly with 20mL of deionized water and a trace dispersant. Place the mixture in an ultrasonic device and sonicate for 5 minutes. Then pour the solution into the Hydro2000SM sample introduction system for testing. The testing equipment used is a Mastersizer3000 manufactured by Malvern Corporation. During the test, when the laser beam passes through the dispersed particle sample, the particle size is measured by measuring the intensity of the scattered light. The data is then used to analyze and calculate the particle size distribution that forms the scattering spectrum. The refractive index of the particles used in the test is 1.8. Each sample is tested three times, and the final particle size is the average of the three tests, which yields Dv10, Dv50, and Dv99, etc.

[0094] 2. Over-temperature safety test method: The lithium-ion battery is placed in a 25℃ constant temperature chamber and left to stand for 30 minutes to allow it to reach a constant temperature. The lithium-ion battery, having reached a constant temperature, is then charged at a constant current of 0.7C to a voltage of 4.3V, and then charged at a constant voltage of 4.3V to a current of 82.5mA. The thickness of the lithium-ion battery is measured and recorded as T0. The battery is then placed in a 60℃ oven for 10 hours, removed from the oven, and cooled for 1 hour. The thickness of the lithium-ion battery is measured and recorded as T1, with real-time monitoring of the thickness in the oven. The over-temperature safety is evaluated using the value X calculated by the following formula: X = (T1 - T0) / T0 × 100%. In the above formula, the smaller the value of X, the better the over-temperature safety of the secondary battery in this application. The battery is graded (A to D) based on the test results of X, with the following grading criteria:

[0095] A: X is less than 12%;

[0096] B: X is 12% or more but less than 15%;

[0097] C: X is 15% or more but less than 20%;

[0098] D: X is greater than 20%.

[0099] 3. Overcurrent safety test method: At room temperature (25℃), the secondary battery is charged at a constant current of 1C from 10% to 30% of its state of charge (SOC). Then, it is charged at a constant current of 1.5C from 30% to 60% of its SOC. Finally, it is charged at a constant current of 2C from 60% to 90% of its SOC. The temperature of the secondary battery is then monitored using a temperature measuring instrument. The lower the measured temperature of the secondary battery, the better its performance. The secondary batteries are graded (A to D) based on the temperature test results, according to the following grading criteria:

[0100] A: Temperature is less than 50℃;

[0101] B: The temperature is above 50℃ and below 55℃;

[0102] C: Temperature is above 55℃ and below 60℃;

[0103] D: Temperature greater than 60℃.

[0104] Table 1. Composition and performance test results of secondary batteries in Examples 1-14 and Comparative Examples 1-4 of this application.

[0105] Test Results

[0106] Please refer to Table 1 for the above test results. In Table 1, " / " indicates that the substance was not added.

[0107] As shown in Table 1, the negative electrode of this application includes a negative electrode current collector and a negative electrode material disposed on the negative electrode current collector. The particle size of the negative electrode material satisfies Dv10:Dv50:Dv99=1:(1.5~2.5):(5~6). The electrolyte includes diethyl carbonate, ethylene carbonate and 1,3-propanesulfonate lactone. Relative to 100 parts by mass of electrolyte, diethyl carbonate is 0.5 parts by mass to 1.5 parts by mass, ethylene carbonate is 15 parts by mass to 30 parts by mass, and 1,3-propanesulfonate lactone is 0.01 parts by mass to 0.5 parts by mass, which can improve the overcurrent and overtemperature safety of the battery.

[0108] In particular, the mass ratio of diethyl carbonate, ethylene carbonate and 1,3-propanesulfonate lactone is (20-30):(400-500):(1-3), which can further improve the overcurrent and overtemperature safety of the secondary battery.

[0109] Specifically, the electrolyte includes methylene methane disulfonate and propylene-1,3-sulfonyl lactone. The sum of methylene methane disulfonate and propylene-1,3-sulfonyl lactone is 0.02 to 1.8 parts by mass relative to 100 parts by mass of the electrolyte, which can further improve the overcurrent and overtemperature safety of the secondary battery.

[0110] Specifically, the electrolyte includes tetramethylborate, which is 1 to 1.5 parts by mass relative to 100 parts by mass of electrolyte, which can further improve the overcurrent and overtemperature safety of the secondary battery.

[0111] Specifically, the positive electrode includes a positive current collector and a positive electrode material disposed on the positive current collector. The positive electrode material includes lithium cobalt oxide, which can further improve the overcurrent and overtemperature safety of the secondary battery.

[0112] In particular, the cathode material also includes one or more of molybdenum and iron, which can further improve the overcurrent and overtemperature safety of the secondary battery.

[0113] Specifically, based on the quality of the cathode material, the molybdenum content is 100ppm to 2000ppm and the iron content is 100ppm to 3000ppm, which can further improve the overcurrent and overtemperature safety of the secondary battery.

[0114] In particular, the negative electrode material includes silicon-based materials, which can further improve the overcurrent and overtemperature safety of the secondary battery.

[0115] In particular, silicon-based materials, including composites of silicon and carbon, can further improve the overcurrent and overtemperature safety of secondary batteries.

[0116] Throughout this specification, references to "embodiment," "partial embodiment," "one embodiment," "another example," "example," "specific example," or "partial example" mean that at least one embodiment or example in this application includes a specific feature, structure, material, or characteristic described in that embodiment or example. Therefore, descriptions appearing throughout this specification, such as "in some embodiments," "in an embodiment," "in one embodiment," "in another example," "in an example," "in a specific example," or "example," do not necessarily refer to the same embodiments or examples in this application. Furthermore, specific features, structures, materials, or characteristics in this application can be combined in any suitable manner in one or more embodiments or examples.

[0117] Although illustrative embodiments have been demonstrated and described, those skilled in the art should understand that the above embodiments should not be construed as limiting the present application, and that changes, substitutions and modifications can be made to the embodiments without departing from the spirit, principles and scope of the present application.

Claims

1. A secondary battery, comprising a positive electrode, a negative electrode, and an electrolyte, characterized in that, The negative electrode includes a negative electrode current collector and a negative electrode material disposed on the negative electrode current collector, wherein the particle size of the negative electrode material satisfies Dv10:Dv50:Dv99=1:(1.5~2.5):(5~6); The electrolyte comprises diethyl carbonate, ethylene carbonate, and 1,3-propanesulfonate lactone, wherein, relative to 100 parts by weight of the electrolyte, the diethyl carbonate comprises 0.5 to 1.5 parts by weight, the ethylene carbonate comprises 15 to 30 parts by weight, and the 1,3-propanesulfonate lactone comprises 0.01 to 0.5 parts by weight.

2. The secondary battery according to claim 1, characterized in that, The mass ratio of the diethyl carbonate, the ethylene carbonate, and the 1,3-propanesulfonate lactone is (20-30):(400-500):(1-3).

3. The secondary battery according to claim 1 or 2, characterized in that, The electrolyte further includes methylene methane disulfonate and propylene-1,3-sulfonyl lactone, wherein the sum of methylene methane disulfonate and propylene-1,3-sulfonyl lactone is 0.02 to 1.8 parts by mass relative to 100 parts by mass of the electrolyte.

4. The secondary battery according to any one of claims 1 to 3, characterized in that, The electrolyte also includes tetramethylboronic acid ester, wherein the tetramethylboronic acid ester is present in amounts of 1 to 1.5 parts by weight relative to 100 parts by weight of the electrolyte.

5. The secondary battery according to any one of claims 1 to 4, characterized in that, The positive electrode includes a positive electrode current collector and a positive electrode material disposed on the positive electrode current collector, wherein the positive electrode material includes lithium cobalt oxide.

6. The secondary battery according to claim 5, characterized in that, The cathode material also includes one or both of molybdenum and iron.

7. The secondary battery according to claim 6, characterized in that, Based on the mass of the cathode material, the mass content of molybdenum is from 100 ppm to 2000 ppm, and the mass content of iron is from 100 ppm to 3000 ppm.

8. The secondary battery according to any one of claims 1 to 7, characterized in that, The negative electrode material includes silicon-based materials.

9. The secondary battery according to claim 8, characterized in that, The silicon-based materials include composites of silicon-based and carbon-based substances.

10. An electronic device, characterized in that, It includes a secondary battery according to any one of claims 1 to 9.

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