Secondary battery and electronic device

Abstract

The invention provides a secondary battery and an electronic device. The secondary battery comprises a positive pole piece, a negative pole piece and electrolyte; when the secondary battery is charged to 3.6 V, a characteristic peak A exists in a range of 18-19 degrees, a characteristic peak B exists in a range of 15-16 degrees and a characteristic peak C exists in a range of 44-46 degrees in an XRD diffraction pattern of a positive pole piece. The electrolyte comprises a first additive, and the first additive comprises at least one of compounds as shown in a formula I, a formula II, a formula III or a formula IV; based on the mass of the electrolyte, the mass percentage content of the first additive is M%, and M is more than or equal to 0.02 and less than or equal to 6. The positive pole piece has the characteristics, so that the positive pole piece has relatively high structural stability, and meanwhile, the electrolyte comprises the first additive and regulates and controls the value of M in the range, so that the high-temperature storage performance, the high-temperature cycle performance and the floating charge performance of the secondary battery can be improved.

Description

Technical Field

[0001] The present application relates to the field of electrochemical technology, and in particular to a secondary battery and an electronic device. Background Art

[0002] Secondary batteries, such as lithium-ion batteries, have attracted widespread attention due to their high energy density, low maintenance, relatively low self-discharge, long cycle life, no memory effect, stable operating voltage and environmental friendliness, and are widely used in portable electronic devices, power tools and electric vehicles. However, with the rapid development of technology and the diversity of market demand, people have also put forward more requirements for secondary batteries for power supply of electronic products, such as thinner, lighter, more diverse appearance, higher safety, higher power and longer service life.

[0003] The dissolution of transition metals in the positive electrode and the oxygen released by the positive electrode catalyzing the decomposition of the electrolyte will affect the high-temperature storage performance of lithium-ion batteries. How to improve the high-temperature storage performance of lithium-ion batteries has become an urgent problem to be solved. Summary of the invention

[0004] The purpose of this application is to provide a secondary battery and an electronic device to improve the high temperature storage performance of the secondary battery. The specific technical solution is as follows:

[0005] The first aspect of the present application provides a secondary battery, which includes a positive electrode sheet, a negative electrode sheet and an electrolyte; when the secondary battery is charged to 3.6V, in the XRD diffraction spectrum of the positive electrode sheet, there is a characteristic peak A in the range of 18° to 19°, a characteristic peak B in the range of 15° to 16°, and a characteristic peak C at 44° to 46°; the electrolyte includes a first additive, and the first additive includes at least one of the compounds shown in Formula I, Formula II, Formula III or Formula IV;

[0006]

[0007] wherein R1 to R4 are each independently selected from C1 to C4 alkyl groups, C2 to C4 alkenyl groups, C2 to C4 alkynyl groups, C1 to C4 alkoxy groups, C2 to C4 alkenyloxy groups, C2 to C4 alkynyloxy groups or phenyl groups which are unsubstituted or substituted with fluorine atoms; R5 to R8 are each independently selected from hydrogen atoms, fluorine atoms or methyl groups; Y is selected from nitrogen atoms or CR 15 , R 15 is selected from a hydrogen atom, a fluorine atom, a methyl group which is unsubstituted or substituted by a fluorine atom; R9 is selected from a C1 to C5 alkyl group which is unsubstituted or substituted by a fluorine atom, a C2 to C4 alkenyl group, a C2 to C4 alkynyl group, a phenyl group or a benzyl group; X is selected from vinylene, R 10 To R14 Each is independently selected from a hydrogen atom, a fluorine atom or a C1 to C4 alkyl group; based on the mass of the electrolyte, the mass percentage of the first additive is M%, 0.02≤M≤6, preferably 0.06≤M≤0.6. For example, the value of M can be 0.02, 0.05, 0.08, 0.1, 0.3, 0.5, 0.6, 0.8, 1, 1.5, 2, 2.5, 3, 3.5, 4, 4.5, 5, 5.5, 6 or a range consisting of any two of the values.

[0008] The inventors have found that when the positive electrode sheet has the above characteristics and the electrolyte includes the first additive shown in formula I, the silicon-containing group in formula I can combine with the hydrofluoric acid generated by the electrolyte during the cycle, reducing the damage of hydrofluoric acid to the positive electrode material and the negative electrode material, reducing the dissolution of transition metals from the positive electrode and the precipitation at the negative electrode, protecting the negative electrode solid electrolyte interface film (SEI film), thereby improving the high temperature storage performance, high temperature cycle performance and floating charge performance of the secondary battery. When the positive electrode sheet has the above characteristics and the electrolyte includes at least one of the first additives shown in formula II, formula III or formula IV, the structure of the above substance contains a double bond, which can be reduced by electrons on the negative electrode surface before the solvent in the electrolyte to form a dense SEI film, reducing the film formation of the solvent in the electrolyte at the negative electrode, and at the same time reducing the possibility of transition metals dissolved from the positive electrode being reduced by electrons on the negative electrode surface to form transition metal dendrites, thereby helping to protect the interface between the negative electrode sheet and the electrolyte. At the same time, the double bonds in the above substances are easily polymerized into films on the surface of the positive electrode sheet at a higher voltage (e.g., ≥2.8V), reducing the possibility of contact between the solvent in the electrolyte and the high-valent positive metal, reducing the oxidation and decomposition of the solvent in the electrolyte to produce gas, thereby improving the high-temperature storage performance, high-temperature cycle performance, and floating charge performance of the secondary battery. When the value of M is too small, for example, less than 0.02, it is not conducive to the first additive to play the above role, and it is impossible to improve the high-temperature storage performance, high-temperature cycle performance, and floating charge performance of the secondary battery; when the value of M is too large, for example, greater than 6, it will cause too many side reactions to occur in the electrolyte during the secondary battery cycle, which is not conducive to improving the high-temperature storage performance, high-temperature cycle performance, and floating charge performance of the secondary battery. Therefore, regulating the value of M within the scope of this application is conducive to improving the high-temperature storage performance, high-temperature cycle performance, and floating charge performance of the secondary battery. Therefore, the positive electrode plate has the above-mentioned characteristics, which can make the positive electrode plate have higher structural stability. At the same time, the electrolyte includes the first additive and the value of the first additive content M is regulated within the above-mentioned range. The first additive can polymerize into a film on the surface of the positive electrode plate and the negative electrode plate to improve the interface stability of the positive electrode plate and the negative electrode plate. Combined with the positive electrode plate with the above-mentioned characteristics, the first additive can passivate the oxygen element and transition metal element in the positive electrode plate, delay the decomposition of the electrolyte, and improve the high-temperature storage gas production problem of the secondary battery, thereby improving the high-temperature storage performance, high-temperature cycle performance and floating charge performance of the secondary battery.

[0009] In this application, there is no particular restriction on the charging rate of "charging the secondary battery to 3.6V", as long as the purpose of this application can be achieved. For example, the charging rate can be 0.1C to 2C, for example, the charging rate can be 0.1C, 0.2C, 0.5C, 0.8C, 1C, 1.2C, 1.5C, 1.8C, 2C or a range consisting of any two values ​​therein. In this application, "high temperature" means greater than or equal to 45°C.

[0010] In some embodiments of the present application, Formula I includes at least one of the following compounds:

[0011]

[0012] When the positive electrode plate has the above characteristics and the electrolyte includes the first additive shown in formula I, the silicon-containing group in formula I can combine with the hydrofluoric acid generated in the electrolyte system during the cycle process, which is more conducive to reducing the damage of hydrofluoric acid to the positive electrode material and the negative electrode material, reducing the dissolution of transition metals from the positive electrode and the precipitation at the negative electrode, and better protecting the negative electrode solid electrolyte interface film (SEI film), thereby further improving the high temperature storage performance, high temperature cycle performance and floating charge performance of the secondary battery.

[0013] In some embodiments of the present application, Formula II includes at least one of the following compounds:

[0014]

[0015] In some embodiments of the present application, Formula III includes at least one of the following compounds:

[0016]

[0017] In some embodiments of the present application, Formula IV includes at least one of the following compounds:

[0018]

[0019] When the positive electrode plate has the above characteristics and the electrolyte includes at least one of the first additives shown in Formula II, Formula III or Formula IV, the structure of the above substance contains double bonds, which can be reduced by electrons on the surface of the negative electrode before the solvent in the electrolyte to form a dense SEI film, which is more conducive to reducing the film formation of the solvent in the electrolyte on the negative electrode, and at the same time can reduce the possibility of transition metals dissolved from the positive electrode being reduced by electrons on the surface of the negative electrode to form transition metal dendrites, thereby helping to protect the interface between the negative electrode plate and the electrolyte. In addition, substances containing double bonds are more likely to polymerize and form films on the surface of the positive electrode plate at higher voltages, thereby reducing the possibility of contact between the solvent in the electrolyte and the high-valent positive metal, reducing the oxidation and decomposition of the solvent in the electrolyte to produce gas, and further improving the high-temperature storage performance, high-temperature cycle performance and floating charge performance of the secondary battery.

[0020] In some embodiments of the present application, when the secondary battery is charged to 3.6V, the XRD diffraction spectrum of the positive electrode sheet has a characteristic peak D in the range of 36° to 38°. On the basis of the characteristic A, characteristic peak B and characteristic peak C in the XRD diffraction spectrum of the positive electrode sheet, the XRD diffraction spectrum of the positive electrode sheet also has the above-mentioned characteristic peak D, which is beneficial to further improve the stability of the positive electrode sheet and reduce the dissolution of transition metals in the positive electrode sheet, thereby being more beneficial to improving the high temperature storage performance, high temperature cycle performance and floating charge performance of the secondary battery.

[0021] In some embodiments of the present application, the positive electrode sheet includes a positive electrode current collector and a positive electrode material layer disposed on at least one surface of the positive electrode current collector, the positive electrode material layer includes a first positive electrode active material and a second positive electrode active material; the first positive electrode active material is a lithium manganese composite oxide, for example, may include but is not limited to LiMnO2, Li 0.95 MnO 1.95 F 0.05 The second positive electrode active material includes lithium cobalt oxide (LiCoO2), lithium iron phosphate (LiFePO4), lithium iron manganese phosphate (LiMn 0.5 Fe 0.5 PO4) or at least one of nickel cobalt manganese oxide. Nickel cobalt manganese oxide may include but is not limited to LiNi 0.8 Co 0.1 Mn 0.1 O2(NCM811), LiNi 0.6 Co 0.2 Mn 0.2 O2(NCM622), LiNi 0.5 Co 0.2 Mn 0.3 O2(NCM523), LiNi 1 / 3 Co 1 / 3 Mn 1 / 3O2(NCM333) or LiNi 0.9 Co 0.05 Mn 0.05 O2 (NCM955) at least one. The positive electrode plate includes the first positive electrode active material and the second positive electrode active material. When the two materials are used at the same time, the Mn element in the delithiation product of the first positive electrode active material can be mostly in the form of Mn 4+ The presence of Mn can reduce the dissolution of Mn caused by the Jahn-Teller effect, reduce the risk of the dissolved Mn element destroying the SEI film, and further improve the stability of the positive electrode sheet. At the same time, the first positive electrode active material and the second positive electrode active material have good compatibility, which is beneficial to reduce the side reaction between the first positive electrode active material and the second positive electrode active material, thereby being more beneficial to improving the high temperature storage performance, high temperature cycle performance and floating charge performance of the secondary battery.

[0022] In some embodiments of the present application, based on the mass of the positive electrode material layer, the content of the lithium manganese composite oxide material is P%, 1≤P≤30, 1≤P / M≤300, preferably 10≤P / M≤100, 2≤P≤20. For example, the value of P can be 1, 3, 5, 8, 10, 13, 15, 17, 20, 22, 25, 26, 28, 30 or a range consisting of any two of the values, and the value of P / M can be 1, 3, 5, 8, 10, 13, 15, 20, 22, 25, 28, 30, 50, 80, 100, 130, 150, 200, 220, 250, 270, 300 or a range consisting of any two of the values. By regulating the values ​​of P and P / M within the above range, the synergistic effect between the first positive electrode active material and the first additive can be better exerted, the transition metal elements and oxygen elements in the positive electrode plate under high potential can be stabilized, a positive electrode solid electrolyte interface film (CEI film) with good performance can be formed on the surface of the positive electrode plate, and a SEI film with good performance can be formed on the surface of the negative electrode plate, thereby reducing the dissolution of the Mn element in the first positive electrode active material and its deposition on the surface of the negative electrode plate, thereby better improving the high temperature storage performance, high temperature cycle performance and floating charge performance of the secondary battery.

[0023] In some embodiments of the present application, based on the mass of the positive electrode material layer, the mass percentage of the second positive electrode active material is Q%, 60≤Q≤95. For example, the value of Q can be 60, 63, 66, 68, 70, 72, 75, 78, 80, 83, 85, 88, 90, 93, 95 or a range consisting of any two of these values. By regulating the value of Q within the above range, it is beneficial to improve the stability of the positive electrode sheet while making the second positive electrode active material and the first positive electrode active material have better compatibility, and it is more beneficial to reduce the side reactions between the first positive electrode active material and the second positive electrode active material while increasing the amount of active lithium, thereby further improving the high temperature storage performance, high temperature cycle performance and floating charge performance of the secondary battery.

[0024] In some embodiments of the present application, the electrolyte further includes a second additive, the second additive includes at least one of 1,3-propane sultone (PS), 1,3-propylene sultone (PES), vinyl sulfate (DTD), 1,3-propylene glycol sulfate (PCS), 2,4-butane sultone (BS) or methylene disulfonate (MMDS), and the mass percentage of the second additive is N%, 0.01≤N≤3, preferably 0.1≤N≤1 based on the mass of the electrolyte. For example, the value of N can be 0.01, 0.03, 0.05, 0.08, 0.1, 0.3, 0.5, 0.6, 0.8, 1 or a range consisting of any two of the values. On the basis of the electrolyte including the first additive, a second additive is further introduced and the value of N is regulated within the above range. The second additive can undergo oxidation reaction at the positive electrode before the first additive, which can further improve the stability of the CEI film and reduce the side reaction between the positive electrode plate and the electrolyte, thereby making the secondary battery have good high-temperature cycle performance while further improving its high-temperature storage performance and floating charge performance.

[0025] The electrolyte of the present application also includes a lithium salt. The present application does not particularly limit the type of lithium salt, as long as the purpose of the present application can be achieved. For example, the lithium salt may include but is not limited to lithium hexafluorophosphate (LiPF6), lithium tetrafluoroborate (LiBF4), lithium difluorophosphate (LiPO2F2), lithium trifluoromethanesulfonyl imide (LiTFSI), lithium bis (fluorosulfonyl) imide (LiFSI), lithium bis oxalate borate (LiBOB) or lithium difluoro oxalate borate (LiDFOB). The present application does not particularly limit the content of lithium salt in the electrolyte, as long as the purpose of the present application can be achieved. Exemplarily, based on the mass of the electrolyte, the mass percentage of the lithium salt is 8% to 15%, for example, the mass percentage of the lithium salt can be 8%, 9%, 10%, 11%, 13%, 15% or a range consisting of any two of the values.

[0026] The electrolyte of the present application also includes a non-aqueous solvent. The present application does not particularly limit the type of non-aqueous solvent, as long as the purpose of the present application can be achieved, for example, it may include but is not limited to at least one of carbonate compounds, carboxylate compounds, ether compounds or other non-aqueous solvents. The above-mentioned carbonate compounds may include but are not limited to at least one of chain carbonate compounds or cyclic carbonate compounds. The above-mentioned chain carbonate compounds may include but are not limited to at least one of dimethyl carbonate, diethyl carbonate (DEC), dipropyl carbonate, methyl propyl carbonate, ethyl propyl carbonate or ethyl methyl carbonate. The above-mentioned cyclic carbonate compounds may include but are not limited to at least one of ethylene carbonate (EC), propylene carbonate (PC), butylene carbonate or vinyl ethylene carbonate. The above-mentioned carboxylate compounds may include but are not limited to at least one of methyl formate, methyl acetate, ethyl acetate, n-propyl acetate, tert-butyl acetate, methyl propionate, ethyl propionate (EP), propyl propionate, γ-butyrolactone, decanolactone, valerolactone or caprolactone. The above-mentioned ether compound may include but is not limited to at least one of ethylene glycol dimethyl ether, dibutyl ether, tetraethylene glycol dimethyl ether, diethylene glycol dimethyl ether, 1,2-dimethoxyethane, 1,2-diethoxyethane, 1-ethoxy-1-methoxyethane, 2-methyltetrahydrofuran or tetrahydrofuran. The above-mentioned other non-aqueous solvents may include but are not limited to at least one of dimethyl sulfoxide, 1,2-dioxolane, cyclopentane, methyl cyclopentane, 1,3-dimethyl-2-imidazolidinone, N-methyl-2-pyrrolidone, dimethylformamide, acetonitrile, trimethyl phosphate, triethyl phosphate or trioctyl phosphate. The present application has no particular restrictions on the content of the non-aqueous solvent in the electrolyte, as long as the purpose of the present application can be achieved. Exemplarily, based on the mass of the electrolyte, the mass percentage of the non-aqueous solvent is 76% to 91.98%. For example, the mass percentage of the non-aqueous solvent can be 76%, 78%, 79%, 80%, 82%, 85%, 86%, 87.5%, 90%, 91%, 91.98% or a range consisting of any two of these values.

[0027] In some embodiments, the electrolyte includes a first additive, a lithium salt and a non-aqueous solvent, the mass percentages of the first additive and the lithium salt are as described above, the mass percentage of the non-aqueous solvent can be 79% to 91.98%, and the secondary battery includes the above electrolyte to improve the high temperature storage performance, high temperature cycle performance and floating charge performance of the secondary battery.

[0028] In some embodiments, the electrolyte includes a first additive, a second additive, a lithium salt and a non-aqueous solvent, the mass percentages of the first additive, the second additive and the lithium salt are as described above, the mass percentage of the non-aqueous solvent can be 76% to 91.97%, and the secondary battery includes the above electrolyte to further improve the high temperature storage performance, high temperature cycle performance and floating charge performance of the secondary battery.

[0029] In the present application, the positive electrode material layer can be arranged on one surface in the thickness direction of the positive electrode current collector, or on two surfaces in the thickness direction of the positive electrode current collector. It should be noted that the "surface" here can be the entire area of ​​the surface of the positive electrode current collector, or it can be a partial area of ​​the surface of the positive electrode current collector. This application has no special restrictions, as long as the purpose of this application can be achieved. This application has no special restrictions on the positive electrode current collector, as long as the purpose of this application can be achieved. For example, the positive electrode current collector may include aluminum foil, aluminum alloy foil or a composite current collector (such as an aluminum-carbon composite current collector). This application has no special restrictions on the thickness of the positive electrode current collector and the positive electrode material layer, as long as the purpose of this application can be achieved. For example, the thickness of the positive electrode current collector is 5μm to 20μm, and the thickness of the single-sided positive electrode material layer is 30μm to 120μm.

[0030] The cathode material layer of the present application may also include a conductive agent and a binder. The present application has no particular restrictions on the conductive agent, as long as the purpose of the present application can be achieved. For example, the conductive agent may include but is not limited to at least one of conductive carbon black (Super P), carbon nanotubes (CNTs), carbon fibers, flake graphite, graphene, metal materials or conductive polymers, and the conductive carbon black may include but is not limited to at least one of acetylene black or Ketjen black. The above-mentioned carbon nanotubes may include but are not limited to single-walled carbon nanotubes and / or multi-walled carbon nanotubes. The above-mentioned carbon fibers may include but are not limited to vapor-grown carbon fibers (VGCF) and / or nano-carbon fibers. The above-mentioned metal materials may include but are not limited to metal powders and / or metal fibers, and specifically, the metal may include but is not limited to at least one of copper, nickel, aluminum or silver. The above-mentioned conductive polymers may include but are not limited to at least one of polyphenylene derivatives, polyaniline, polythiophene, polyacetylene or polypyrrole. The present application has no particular restrictions on the binder, as long as the purpose of the present application can be achieved. For example, the binder may include but is not limited to at least one of polyacrylic acid, sodium polyacrylate, potassium polyacrylate, lithium polyacrylate, polyimide, polyvinyl alcohol, carboxymethyl cellulose, sodium carboxymethyl cellulose, lithium carboxymethyl cellulose, polyamide-imide, styrene-butadiene rubber or polyvinylidene fluoride (PVDF). The present application has no particular restrictions on the mass percentage of the conductive agent and the binder in the positive electrode material layer, as long as the purpose of the present application can be achieved. For example, based on the mass of the positive electrode material layer, the mass percentage of the conductive agent can be 0% to 5%, and the mass percentage of the binder can be 1.0% to 5%.

[0031] In the present application, there is no particular restriction on the preparation method of the positive electrode sheet, as long as the purpose of the present application can be achieved. For example, it can be prepared by the following method: a first positive electrode active material, a second positive electrode active material, a conductive agent, and a binder are mixed, N-methylpyrrolidone (NMP) is added and stirred evenly, and a positive electrode slurry with a solid content of 65wt% to 85wt% is obtained. The positive electrode slurry is evenly coated on one surface of the positive electrode collector, and a positive electrode sheet coated with a positive electrode material layer on one side is obtained after drying. Then the above coating steps are repeated on the other surface of the positive electrode collector, and a positive electrode sheet coated with a positive electrode material layer on both sides is obtained after drying. After coating is completed, the positive electrode sheet is obtained by cold pressing and cutting.

[0032] The present application has no special restrictions on the negative electrode plate, as long as the purpose of the present application can be achieved. For example, the negative electrode plate includes a negative electrode current collector and a negative electrode material layer arranged on at least one surface of the negative electrode current collector. In the present application, the negative electrode material layer can be arranged on one surface in the thickness direction of the negative electrode current collector, or on two surfaces in the thickness direction of the negative electrode current collector. It should be noted that the "surface" here can be the entire area of ​​the negative electrode current collector or a partial area of ​​the negative electrode current collector. The present application has no special restrictions, as long as the purpose of the present application can be achieved. The negative electrode material layer of the present application contains negative electrode active materials. The present application has no special restrictions on the types of negative electrode active materials, as long as the purpose of the present application can be achieved. For example, the negative electrode active material can include natural graphite, artificial graphite, mesophase microcarbon beads (MCMB), hard carbon, soft carbon, silicon, silicon-carbon composites, SiO x (0<x≤2), Li-Sn alloy, Li-Sn-O alloy, Sn, SnO, SnO2, spinel structure lithium titanate Li4Ti5O 12 , Li-Al alloy or lithium metal. In the present application, there is no particular restriction on the thickness of the negative electrode current collector and the negative electrode material layer, as long as the purpose of the present application can be achieved. For example, the thickness of the negative electrode current collector is 4 μm to 12 μm, and the thickness of the single-sided negative electrode material layer is 30 μm to 160 μm.

[0033] The negative electrode material layer of the present application may also contain a conductive agent, a binder and a dispersant. The present application has no particular restrictions on the mass ratio of the negative electrode active material, the conductive agent and the binder in the negative electrode material layer, as long as the purpose of the present application can be achieved. The present application has no particular restrictions on the conductive agent and the binder, as long as the purpose of the present application can be achieved. For example, the conductive agent and the binder may be at least one of the conductive agents in the above-mentioned positive electrode material layer. The thickener may include, but is not limited to, at least one of sodium carboxymethyl cellulose or lithium carboxymethyl cellulose.

[0034] In the present application, there is no particular limitation on the preparation method of the negative electrode sheet, as long as the purpose of the present application can be achieved. For example, it can be prepared by the following method: the negative electrode active material, the binder, and the thickener are mixed, and deionized water is added and stirred evenly to obtain a negative electrode slurry with a solid content of 40wt% to 65wt%. The negative electrode slurry is evenly coated on one surface of the negative electrode collector, and after drying, a negative electrode sheet coated with a negative electrode material layer on one side is obtained. Then, the above coating steps are repeated on the other surface of the negative electrode collector, and after drying, a negative electrode sheet coated with a negative electrode material layer on both sides is obtained. After coating, the negative electrode sheet is obtained by cold pressing and cutting.

[0035] The secondary battery of the present application also includes a separator. The present application has no particular restrictions on the separator, as long as the purpose of the present application can be achieved. For example, the material of the separator may include but is not limited to polyethylene (PE), polypropylene (PP)-based polyolefins (PO), polyesters (e.g., polyethylene terephthalate (PET) film), cellulose, polyimide (PI), polyamide (PA), spandex or at least one of aramid. The type of separator may include at least one of a woven membrane, a non-woven membrane, a microporous membrane, a composite membrane, a rolled membrane or a spun membrane. In some embodiments, the separator may include a substrate layer and a surface treatment layer. The substrate layer may be a non-woven fabric, a film or a composite membrane having a porous structure, and the material of the substrate layer may include at least one of polyethylene, polypropylene, polyethylene terephthalate or polyimide. Optionally, a polypropylene porous membrane, a polyethylene porous membrane, a polypropylene non-woven fabric, a polyethylene non-woven fabric or a polypropylene-polyethylene-polypropylene porous composite membrane may be used. Optionally, a surface treatment layer is provided on at least one surface of the substrate layer, and the surface treatment layer can be a polymer layer or an inorganic layer, or a layer formed by a mixed polymer and an inorganic substance. In some embodiments, the inorganic layer includes inorganic particles and a binder. The present application has no particular restrictions on inorganic particles, such as inorganic particles can 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 present application has no particular restrictions on binders, such as binders can be at least one of the above-mentioned binders. In some embodiments of the present application, the polymer layer includes a polymer, and the material of the polymer includes at least one of polyamide, polyacrylonitrile, acrylate polymer, polyacrylic acid, polyacrylate, polyvinyl pyrrolidone, polyvinyl ether or polyvinylidene fluoride or poly (vinylidene fluoride-hexafluoropropylene). In the present application, there is no particular limitation on the thickness of the separator as long as the purpose of the present application can be achieved. For example, the thickness of the separator may be 3 μm to 30 μm.

[0036] The secondary battery also includes a shell for accommodating a positive electrode plate, a separator, a negative electrode plate and an electrolyte, as well as other components known in the field of secondary batteries, and this application does not limit the above-mentioned other components. This application does not particularly limit the shell, and it can be a shell known in the art, as long as the purpose of this application can be achieved. For example, the shell can be a hard shell or a flexible shell. The material of the hard shell can be metal, and this application does not limit the type of metal. A metal hard shell known in the art can be used, as long as the purpose of this application can be achieved. The flexible shell can be a metal plastic film, such as an aluminum plastic film, a steel plastic film, etc.

[0037] The present application does not particularly limit the type of secondary battery, which may include any device that undergoes an electrochemical reaction. For example, the secondary battery may include, but is not limited to: a lithium ion battery, a sodium ion battery, a lithium polymer secondary battery, and a lithium ion polymer secondary battery.

[0038] The preparation process of the secondary battery of the present application is well known to those skilled in the art, and there is no particular limitation in the present application. For example, the preparation process of the secondary battery may include but is not limited to the following steps: stacking the positive electrode sheet, the separator and the negative electrode sheet in order, and winding, folding and other operations as needed to obtain an electrode assembly of a winding structure, placing the electrode assembly in a shell, injecting the electrolyte into the shell and sealing it to obtain a secondary battery. Alternatively, stacking the positive electrode sheet, the separator and the negative electrode sheet in order, and then fixing the four corners of the entire laminated structure with tape to obtain an electrode assembly of a laminated structure, placing the electrode assembly in a shell, injecting the electrolyte into the shell and sealing it to obtain a secondary battery. In addition, overcurrent protection elements, guide plates, etc. may also be placed in the shell as needed to prevent the pressure inside the secondary battery from rising and overcharging and discharging.

[0039] The second aspect of the present application provides an electronic device, which includes the secondary battery provided by the first aspect of the present application. The secondary battery provided by the first aspect of the present application has good high-temperature storage performance, high-temperature cycle performance and floating charge performance, so that the electronic device of the present application has a long service life and good performance.

[0040] The present application does not particularly limit the type of electronic device, which can be any electronic device known in the prior art. In some embodiments, the electronic device can include but is not limited to a laptop computer, a pen-input computer, a mobile computer, an electronic book player, a portable phone, a portable fax machine, a portable copier, a portable printer, a head-mounted stereo headset, a video recorder, an LCD television, a portable cleaner, a portable CD player, a mini-disc, a transceiver, an electronic notepad, a calculator, a memory card, a portable recorder, a radio, a backup power supply, a motor, a car, a motorcycle, a power-assisted bicycle, a bicycle, a lighting fixture, a toy, a game console, a clock, an electric tool, a flashlight, a camera, a large household battery and a lithium-ion capacitor, etc.

[0041] Beneficial effects of this application:

[0042] The present application provides a secondary battery and an electronic device. The secondary battery includes a positive electrode sheet, a negative electrode sheet and an electrolyte; when the secondary battery is charged to 3.6V, in the XRD diffraction spectrum of the positive electrode sheet, there is a characteristic peak A in the range of 18° to 19°, a characteristic peak B in the range of 15° to 16°, and a characteristic peak C at 44° to 46°. The electrolyte includes a first additive, the first additive includes at least one of the compounds shown in Formula I, Formula II, Formula III or Formula IV; based on the mass of the electrolyte, the mass percentage of the first additive is M%, and 0.02≤M≤6. The positive electrode plate has the above characteristics, which can make the positive electrode plate have higher structural stability. At the same time, the electrolyte includes the first additive and the value of M is regulated within the above range. The first additive can polymerize into a film on the surface of the positive electrode plate and the negative electrode plate to improve the interface stability of the positive electrode plate and the negative electrode plate. Combined with the positive electrode plate with the above characteristics, the first additive can passivate the oxygen element and transition metal element in the positive electrode plate, delay the decomposition of the electrolyte, and improve the high-temperature storage gas production problem of the secondary battery, thereby improving the high-temperature storage performance, high-temperature cycle performance and floating charge performance of the secondary battery. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] The drawings described herein are used to provide further understanding of the present application and constitute a part of the present application. The illustrative embodiments of the present application and their descriptions are used to explain the present application and do not constitute improper limitations on the present application.

[0044] Figure 1 is the X-ray diffraction spectrum of the positive electrode sheet of Example 1-1;

[0045] Figure 2 This is the X-ray diffraction spectrum of the positive electrode sheet of Example 1-48. DETAILED DESCRIPTION

[0046] In order to make the purpose, technical scheme, and advantages of the present application more clearly understood, the present application is further described in detail with reference to the accompanying drawings and examples. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments. All other embodiments obtained by those skilled in the art based on the present application belong to the scope of protection of the present application.

[0047] It should be noted that in the following content, the present application is explained by taking a lithium-ion battery as an example of a secondary battery, but the secondary battery of the present application is not limited to a lithium-ion battery.

[0048] Example

[0049] The following examples and comparative examples are given to more specifically describe the embodiments of the present application. Various tests and evaluations were performed according to the following methods. In addition, unless otherwise specified, "parts" and "%" are based on mass.

[0050] Test methods and equipment:

[0051] X-ray diffraction (XRD) test:

[0052] The lithium-ion battery was charged to 3.6V at 1C and then disassembled. The positive electrode was taken out and the positive electrode sample was obtained after cleaning and drying. The XRD spectrum of the positive electrode sample was tested using an X-ray diffraction tester (PANalytical, XPert Pro MPD, the Netherlands), and the test conditions were set as follows: Cu Kα radiation The working current was 250 mA, continuous scanning was adopted, the working voltage was 40 kV, the scanning range 2θ was 10° to 70°, the step length was 0.1°, and the scanning speed was 0.2 s / step.

[0053] Test of the content of each component in the electrolyte:

[0054] The lithium-ion battery was discharged at a constant current of 1C to 2.5V and then disassembled, the electrolyte was collected, and the removed positive electrode sheet, negative electrode sheet, and isolation membrane were centrifuged. The liquid obtained after centrifugation and the above electrolyte were evenly mixed, and then tested using a gas chromatography-mass spectrometer (instrument model: Agilent 8890) and an ion chromatography (instrument model: AQUION ion chromatography) to obtain each component in the electrolyte and test its content.

[0055] High temperature storage performance test:

[0056] At 25°C, the lithium-ion battery was charged to 3.6V at a constant current of 0.5C, and then charged to a current of 0.05C at a constant voltage. The thickness of the lithium-ion battery was tested and recorded as D0. Finally, the lithium-ion battery was placed in a 60°C oven for storage for 180 days and then taken out to monitor the thickness at this time, which was recorded as D. The 60°C storage thickness expansion rate of the lithium-ion battery (%) = (D-D0) / D0×100%.

[0057] High temperature cycle performance test:

[0058] At 45°C, the lithium-ion battery is charged to 3.6V at 1C, charged to 0.05C at 3.6V, and then discharged to 2.5V at a constant current of 1C. This is a cycle process, and the first discharge capacity is recorded as C1. The charge and discharge cycle is repeated for 1000 times, and the discharge capacity of the 1000th cycle is recorded as C2. The 45°C / 1000 cycle capacity retention rate (%) of the lithium-ion battery is C2 / C1×100%.

[0059] Floating charge performance test:

[0060] The lithium-ion battery was discharged at 0.5C to 2.5V at 25°C, then charged to 3.6V at 1C, and charged to 0.05C at a constant voltage of 3.6V. The thickness of the lithium-ion battery was tested and recorded as D2. It was placed in a 45°C oven and charged at a constant voltage of 3.6V for 50 days. The thickness change was monitored at this time and the thickness was recorded as D3. The 45°C float charge thickness expansion rate of the lithium-ion battery (%) = (D3-D2) / D2×100%. The test should be stopped if the thickness expansion rate is greater than 50%.

[0061] Example 1-1

[0062] <Preparation of Electrolyte>

[0063] In an argon atmosphere glove box with a water content of <10ppm, non-aqueous solvents ethylene carbonate (EC), propylene carbonate (PC), diethyl carbonate (DEC), ethyl propionate (EP), and propyl propionate (PP) are mixed uniformly in a mass ratio of 1:1:1:1:1, and then lithium salt LiPF6 is dissolved in the non-aqueous solvent, and finally the first additive formula III-3 is added and mixed uniformly to obtain an electrolyte. Based on the mass of the electrolyte, the mass percentage of the lithium salt is 12.5%, the mass percentage of the first additive is shown in Table 1, and the rest is non-aqueous solvent.

[0064] <Preparation of positive electrode sheet>

[0065] The first positive electrode active material LiMnO2, the second positive electrode active material LiFePO4, the binder PVDF and the conductive agent conductive carbon black are mixed in a mass ratio of 6:90.4:2.1:1.5, and N-methylpyrrolidone (NMP) is added as a solvent to prepare a slurry with a solid content of 75wt%, and the positive electrode slurry is obtained after vacuum stirring. The positive electrode slurry is evenly coated on one surface of a positive electrode current collector aluminum foil with a thickness of 10μm, and dried at 120°C to obtain a positive electrode sheet with a single-sided coating of a positive electrode material layer. The coating weight of the positive electrode material layer is 267.8mg / 1540mm 2 After cold pressing, cutting and welding of the tabs, a positive electrode sheet with a specification of 74 mm × 867 mm is obtained for standby use. The thickness of the single-sided positive electrode material layer is 42 μm.

[0066] <Preparation of negative electrode sheet>

[0067] The negative electrode active material artificial graphite, the binder styrene butadiene rubber (SBR), and the thickener sodium carboxymethyl cellulose (CMC) were mixed in a weight ratio of 97.4:1.4:1.2, and deionized water was added as a solvent to prepare a slurry with a solid content of 45wt%. The negative electrode slurry was obtained after being stirred evenly by a vacuum mixer. The negative electrode slurry was evenly coated on one surface of a negative electrode current collector copper foil with a thickness of 6μm, and dried at 120°C to obtain a negative electrode sheet with a single-sided coating of a negative electrode material layer. The coating weight of the negative electrode material layer was 142mg / 1540mm 2 After cold pressing, cutting and welding of the pole ears, a negative electrode sheet with a specification of 78 mm × 875 mm is obtained for use. The thickness of the single-sided negative electrode material layer is 54.5 μm.

[0068] <Preparation of Separator Film>

[0069] PVDF and alumina ceramics were mixed in a mass ratio of 9:1, deionized water was added as a solvent, and a ceramic layer slurry with a solid content of 25wt% was prepared, and the slurry was evenly coated on one surface of a 12μm thick polyethylene porous film substrate, and dried to obtain a separator with a single-sided coating of a 2μm alumina ceramic layer. Thereafter, the above coating steps were repeated on the other surface of the substrate to obtain a separator with a double-sided coating of a 2μm alumina ceramic layer, and the porosity of the separator was 39%.

[0070] <Preparation of lithium-ion batteries>

[0071] The prepared positive electrode sheet, separator, and negative electrode sheet are stacked in order, so that the separator is placed between the positive electrode sheet and the negative electrode sheet to play an isolating role, and then wound to obtain the electronic assembly; after welding the pole ear, the electrode assembly is placed in an aluminum-plastic film packaging bag, placed in an 85°C vacuum oven for 12 hours to remove moisture, and the above-prepared electrolyte is injected. After vacuum packaging, standing, formation, shaping, capacity testing, secondary packaging and other processes, a lithium-ion battery is obtained. Among them, the formation process is as follows: the first cycle of charge and discharge is carried out at 45±5°C, and the process is as follows: first, charge at a constant current rate of 0.1C for 10 minutes, then charge at a constant current rate of 0.5C to a specified voltage of 4.6V, then charge at a constant voltage until the current is less than or equal to 0.05C, and then discharge at a constant current rate of 0.5C to 2.5V.

[0072] Example 1-2 to Example 1-61

[0073] Except for adjusting the parameters according to Table 1, the rest is the same as Example 1-1. When the mass percentage of the first additive and the mass percentage of the non-aqueous solvent are changed accordingly, the mass percentage of the lithium salt remains unchanged.

[0074] Example 2-1 to Example 2-17

[0075] Except for adjusting the parameters according to Table 2, the rest is the same as Example 1-1.

[0076] Example 3-1 to Example 3-16

[0077] Except for adjusting the parameters according to Table 3, the rest is the same as Example 1-56.

[0078] Example 4-1 to Example 4-11

[0079] The same as Example 1-1 except that the second additive is added in <Preparation of Electrolyte> and the parameters are adjusted according to Table 4. When the mass percentage of the second additive and the mass percentage of the non-aqueous solvent are changed accordingly, the mass percentage of the first additive and the lithium salt remain unchanged.

[0080] Comparative Example 1

[0081] Except that the first additive is not added in <Preparation of Electrolyte>, the mass percentage of the non-aqueous solvent is changed accordingly, and the mass percentage of the lithium salt remains unchanged, the rest is the same as Example 1-1.

[0082] Comparative Example 2

[0083] Except that the first positive electrode active material is not added in <Preparation of Positive Electrode Sheet>, the mass percentage of the second positive electrode active material is changed accordingly, and the mass percentage of the binder and the conductive agent remain unchanged, the rest is the same as Example 1-1.

[0084] Comparative Example 3

[0085] Except that the first additive is not added in <Preparation of Electrolyte>, the mass percentage of the non-aqueous solvent is changed accordingly, and the mass percentage of the lithium salt remains unchanged, the rest is the same as Comparative Example 2.

[0086] Comparative Example 4 to Comparative Example 5

[0087] Except that the mass percentage of the first additive is adjusted according to Table 1, the mass percentage of the non-aqueous solvent is changed accordingly, and the mass percentage of the lithium salt remains unchanged, the rest is the same as Example 1-1.

[0088] The preparation parameters and performance parameters of each embodiment and comparative example are shown in Tables 1 to 4.

[0089] Table 1

[0090]

[0091]

[0092]

[0093] Note: In Table 1, “\” means there is no relevant parameter or the corresponding substance does not exist.

[0094] It can be seen from Examples 1-1 to 1-61 that in the XRD diffraction spectrum of the positive electrode sheet, there is a characteristic peak A in the range of 18° to 19°, a characteristic peak B in the range of 15° to 16°, and a characteristic peak C at 44° to 46°. At the same time, the electrolyte includes the first additive and the value of M is regulated within the scope of the present application. The lithium-ion battery has a lower 60°C storage thickness expansion rate, a higher 45°C / 1000 cycle capacity retention rate, and a lower 45°C floating charge thickness expansion rate, indicating that the lithium-ion battery has better high-temperature storage performance, high-temperature cycle performance, and floating charge performance. The electrolyte of Comparative Example 1 does not include the first additive, the positive electrode sheet of Comparative Example 2 does not have the above-mentioned characteristic peak in its XRD spectrum, the electrolyte of Comparative Example 3 does not include the first additive and its positive electrode sheet does not have the above-mentioned characteristic peak in its XRD spectrum, the value of M in Comparative Examples 4 and 5 is not within the scope of the present application, and the lithium-ion batteries of the above-mentioned comparative examples have a higher 60°C storage thickness expansion rate, a lower 45°C / 1000 cycle capacity retention rate and a higher 45°C float charge thickness expansion rate, indicating that the high temperature storage performance, high temperature cycle performance and float charge performance of the lithium-ion batteries are worse.

[0095] The type of the first additive usually affects the high temperature storage performance, high temperature cycle performance and floating charge performance of the lithium ion battery. It can be seen from Examples 1-1 to 1-51 that the selection of the first additive within the scope of the present application can make the lithium ion battery have a lower 60°C storage thickness expansion rate, a higher 45°C / 1000 cycle capacity retention rate and a lower 45°C floating charge thickness expansion rate, indicating that the lithium ion battery has good high temperature storage performance, high temperature cycle performance and floating charge performance.

[0096] The value of M usually affects the high temperature storage performance, high temperature cycle performance and floating charge performance of the lithium-ion battery. It can be seen from Example 1-1, Example 1-52 to Example 1-61, Comparative Example 4 and Comparative Example 5 that when the value of M is too small, such as Comparative Example 4, when the value of M is too large, such as Comparative Example 8, the lithium-ion battery of the above comparative example has a higher 60°C storage thickness expansion rate, a lower 45°C / 1000 cycle capacity retention rate and a higher 45°C floating charge thickness expansion rate, indicating that when the value of M is not within the scope of this application, the high temperature storage performance, high temperature cycle performance and floating charge performance of the lithium-ion battery are worse. Therefore, by regulating the value of M within the scope of this application, the lithium-ion battery can have a lower 60°C storage thickness expansion rate, a higher 45°C / 1000 cycle capacity retention rate and a lower 45°C floating charge thickness expansion rate, indicating that the lithium-ion battery has good high temperature storage performance, high temperature cycle performance and floating charge performance.

[0097] The type of the first positive electrode active material usually affects the high temperature storage performance, high temperature cycle performance and floating charge performance of the lithium ion battery. It can be seen from Examples 1-1 and 1-51 that the selection of the first positive electrode active material within the scope of the present application can make the lithium ion battery have a lower 60°C storage thickness expansion rate, a higher 45°C / 1000 cycle capacity retention rate and a lower 45°C floating charge thickness expansion rate, indicating that the lithium ion battery has good high temperature storage performance, high temperature cycle performance and floating charge performance.

[0098] from Figure 1 It can be seen that in the XRD diffraction spectrum of the positive electrode sheet of Example 1-1, there is a characteristic peak A in the range of 18° to 19°, a characteristic peak B in the range of 15° to 16°, and a characteristic peak C in the range of 44° to 46°.

[0099] from Figure 2 It can be seen that in the XRD diffraction spectrum of the positive electrode sheet of Example 1-48, there is a characteristic peak A in the range of 18° to 19°, a characteristic peak B in the range of 15° to 16°, and a characteristic peak C in the range of 44° to 46°.

[0100] Table 2

[0101]

[0102]

[0103] Note: “\” in Table 2 means there is no relevant parameter or the corresponding substance does not exist.

[0104] The inclusion of characteristic peak D in the positive electrode plate usually affects the high temperature storage performance, high temperature cycle performance and floating charge performance of the lithium ion battery. It can be seen from Examples 1-1, 1-6, 1-19, 2-1 to 1-17 that the inclusion of characteristic peak D in the positive electrode plate can make the lithium ion battery have a lower 60°C storage thickness expansion rate, a higher 45°C / 1000 cycle capacity retention rate and a lower 45°C floating charge thickness expansion rate, indicating that the lithium ion battery has good high temperature storage performance, high temperature cycle performance and floating charge performance.

[0105] The type of the second positive electrode active material usually affects the high temperature storage performance, high temperature cycle performance and floating charge performance of the lithium ion battery. It can be seen from Example 1-1, Example 2-3, Example 2-7, Example 2-11, and Example 2-15 that the selection of the second positive electrode active material within the scope of the present application can make the lithium ion battery have a lower 60°C storage thickness expansion rate, a higher 45°C / 1000 cycle capacity retention rate, and a lower 45°C floating charge thickness expansion rate, indicating that the lithium ion battery has good high temperature storage performance, high temperature cycle performance, and floating charge performance.

[0106] Table 3

[0107]

[0108]

[0109] The values ​​of P and Q usually affect the high temperature storage performance, high temperature cycle performance and floating charge performance of lithium-ion batteries. It can be seen from Examples 1-1, 3-1 to 3-16 that by adjusting the values ​​of P and Q within the scope of this application, the lithium-ion battery can have a lower 60°C storage thickness expansion rate, a higher 45°C / 1000 cycle capacity retention rate and a lower 45°C floating charge thickness expansion rate, indicating that the lithium-ion battery has good high temperature storage performance, high temperature cycle performance and floating charge performance.

[0110] The value of P / M usually affects the high temperature storage performance, high temperature cycle performance and floating charge performance of lithium-ion batteries. It can be seen from Example 1-1, Example 1-52 to Example 1-61, and Example 3-1 to Example 3-16 that by adjusting the value of P / M within the scope of this application, the lithium-ion battery can have a lower 60°C storage thickness expansion rate, a higher 45°C / 1000 cycle capacity retention rate, and a lower 45°C floating charge thickness expansion rate, indicating that the lithium-ion battery has good high temperature storage performance, high temperature cycle performance, and floating charge performance.

[0111] Table 4

[0112]

[0113]

[0114] Note: “\” in Table 4 means there is no relevant parameter or the corresponding substance does not exist.

[0115] The electrolyte further includes a second additive and the value of N usually affects the high temperature storage performance, high temperature cycle performance and floating charge performance of the lithium ion battery. It can be seen from Examples 1-1, 4-1 to 4-7 that further introducing the second additive into the electrolyte and regulating the value of N within the scope of the present application can make the lithium ion battery have a lower 60°C storage thickness expansion rate, a higher 45°C / 1000 cycle capacity retention rate and a lower 45°C floating charge thickness expansion rate, indicating that the lithium ion battery has good high temperature storage performance, high temperature cycle performance and floating charge performance.

[0116] The type of the second additive usually affects the high temperature storage performance, high temperature cycle performance and floating charge performance of the lithium ion battery. It can be seen from Examples 4-1, 4-8 to 4-11 that the selection of the second additive within the scope of the present application can make the lithium ion battery have a lower 60°C storage thickness expansion rate, a higher 45°C / 1000 cycle capacity retention rate and a lower 45°C floating charge thickness expansion rate, indicating that the lithium ion battery has good high temperature storage performance, high temperature cycle performance and floating charge performance.

[0117] The above description is only a preferred embodiment of the present application and is not intended to limit the present application. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present application shall be included in the scope of protection of the present application.

Claims

1. A secondary battery comprising a positive electrode sheet, a negative electrode sheet and an electrolyte; When the secondary battery is charged to 3.6V, in the XRD diffraction spectrum of the positive electrode sheet, there is a characteristic peak A in the range of 18° to 19°, a characteristic peak B in the range of 15° to 16°, and a characteristic peak C at 44° to 46°; The electrolyte includes a first additive, wherein the first additive includes at least one of the compounds represented by Formula I, Formula II, Formula III or Formula IV; in, R1 to R4 are each independently selected from C1 to C4 alkyl, C2 to C4 alkenyl, C2 to C4 alkynyl, C1 to C4 alkoxy, C2 to C4 alkenyloxy, C2 to C4 alkynyloxy or phenyl which are unsubstituted or substituted by fluorine atoms; R5 to R8 are each independently selected from a hydrogen atom, a fluorine atom or a methyl group; Y is selected from a nitrogen atom or CR 15 , R 15 A group selected from a hydrogen atom, a fluorine atom, and a methyl group which is unsubstituted or substituted with a fluorine atom; R9 is selected from C1 to C5 alkyl, C2 to C4 alkenyl, C2 to C4 alkynyl, phenyl or benzyl groups which are unsubstituted or substituted by fluorine atoms; X is selected from vinylene, R 10 To R 14 Each is independently selected from a hydrogen atom, a fluorine atom or a C1 to C4 alkyl group; Based on the mass of the electrolyte, the mass percentage of the first additive is M%, and 0.02≤M≤6.

2. The secondary battery according to claim 1, wherein The formula I comprises at least one of the following compounds: The formula II comprises at least one of the following compounds: The formula III comprises at least one of the following compounds: The formula IV comprises at least one of the following compounds:

3. The secondary battery according to claim 1, wherein 0.06≤M≤0.6。 4. The secondary battery according to any one of claims 1 to 3, wherein When the secondary battery is charged to 3.6V, a characteristic peak D exists in the range of 36° to 38° in the XRD diffraction spectrum of the positive electrode.

5. The secondary battery according to any one of claims 1 to 3, wherein The positive electrode sheet includes a positive electrode current collector and a positive electrode material layer disposed on at least one surface of the positive electrode current collector, wherein the positive electrode material layer includes a first positive electrode active material and a second positive electrode active material; The first positive electrode active material is a lithium manganese composite oxide; the second positive electrode active material includes at least one of lithium cobalt oxide, lithium iron phosphate, lithium iron manganese phosphate or lithium nickel cobalt manganese oxide.

6. The secondary battery according to claim 5, wherein Based on the mass of the positive electrode material layer, the content of the lithium manganese composite oxide material is P%, 1≤P≤30; 1≤P / M≤300.

7. The secondary battery according to claim 6, which satisfies at least one of the following characteristics: (a) 10≤P / M≤100; (b)2≤P≤20.

8. The secondary battery according to claim 5, wherein Based on the mass of the positive electrode material layer, the mass percentage of the second positive electrode active material is Q%, and 60≤Q≤95.

9. The secondary battery according to any one of claims 1 to 3, wherein The electrolyte further includes a second additive, wherein the second additive includes at least one of 1,3-propane sultone, 1,3-propylene sultone, vinyl sulfate, 1,3-propylene glycol sulfate, 2,4-butane sultone or methylene methane disulfonate. Based on the mass of the electrolyte, the mass percentage of the second additive is N%, and 0.01≤N≤3.

10. The secondary battery according to claim 9, wherein 0.1≤N≤1。 11 . An electronic device comprising the secondary battery according to claim 1 .

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