Secondary battery and electronic equipment

Abstract

The invention relates to a secondary battery and electronic equipment, and belongs to the technical field of electrochemistry. The secondary battery comprises a positive pole piece and a negative pole piece, the positive pole piece comprises a positive current collector and a positive material layer arranged on at least one side surface of the positive current collector, and the positive material layer comprises a positive active material; the negative electrode plate comprises a negative electrode current collector and a negative electrode material layer arranged on at least one side surface of the negative electrode current collector, and the negative electrode material layer comprises a negative electrode active material; the positive electrode active material and / or the negative electrode active material comprise / comprises a core material and a coating layer located on at least part of the surface of the core material, and the coating layer comprises a single ion conductor polymer and an inorganic solid electrolyte. The secondary battery has good dynamic performance and excellent cycle performance.

Description

Technical Field

[0001] This application relates to the field of electrochemical technology, and in particular to a secondary battery and electronic device. Background Technology

[0002] Compared to traditional liquid batteries, solid-state batteries have higher energy density and better safety. However, the solid-solid interface contact inside solid-state batteries is mostly point contact, resulting in a small contact area. Even in some battery systems, the interface contact may initially be surface contact, but as the solid-state battery is charged and discharged, the inevitable volume expansion of the electrode material leads to deterioration of the interface contact and a decrease in interface stability, resulting in poor cycle performance of the battery. Summary of the Invention

[0003] The purpose of this application is to overcome the shortcomings of the prior art and provide a secondary battery and electronic device.

[0004] To achieve the above objectives, the technical solution adopted in this application is as follows:

[0005] The first aspect of this application provides a secondary battery, including a positive electrode, an electrolyte, and a negative electrode. The positive electrode includes a positive current collector and a positive electrode material layer disposed on at least one side surface of the positive current collector, the positive electrode material layer including a positive active material. The negative electrode includes a negative current collector and a negative electrode material layer disposed on at least one side surface of the negative current collector, the negative electrode material layer including a negative active material. The positive active material and / or the negative active material includes a core material and a coating layer located on at least a portion of the surface of the core material, the coating layer including a single-ion conductor polymer and an inorganic solid electrolyte.

[0006] This application uses positive or negative electrode active particles as core materials and forms a stable solid interface coating layer on the surface of the core material through the interaction of a single-ion conductor with an inorganic solid electrolyte. The solid interface coating layer has good mechanical strength and flexibility, which can not only enhance the mechanical strength of the positive or negative electrode active particles to alleviate the stress generated by their volume expansion during charging and discharging and thus enhance their structural stability, but also reduce the side reactions on the surface of the positive or negative electrode active particles and construct efficient ion transport channels to enhance the migration ability of cations, thereby improving the kinetic performance and cycle performance of the secondary battery.

[0007] In some embodiments of this application, the infrared spectrum of the positive or negative electrode active material shows a wavenumber of 900 cm⁻¹. -1 Up to 2500cm -1An infrared absorption peak is present at the location. The infrared absorption peaks in this wavenumber range are mainly characteristic peaks of carboxylic acid groups (-COO-), sulfonic acid groups (-SO3-), sulfonyl groups (-SO2N(-)SO2), and borate groups (-BO3-). Carboxylic acid groups, sulfonic acid groups, sulfonyl groups, or borate groups can all promote the dissociation of lithium ions and interact with lithium ions to promote lithium ion transport.

[0008] In some embodiments of this application, the transmittance of the infrared absorption peak is 20% to 60%. The transmittance of the infrared absorption peak can reflect, to some extent, the amount of carboxylic acid groups, sulfonic acid groups, sulfonyl groups, or boric acid groups in the positive or negative electrode active material. Studies have found that by controlling the infrared transmittance of the infrared absorption peak within the above range, the battery can obtain better energy density and kinetic performance.

[0009] In some embodiments of this application, the mass percentage of the inorganic solid electrolyte is 0.5% to 2% based on the mass of the positive electrode material layer; and / or, the mass percentage of the inorganic solid electrolyte is 0.5% to 2% based on the mass of the negative electrode material layer. By controlling the mass percentage of the inorganic solid electrolyte in the positive or negative electrode material layer within the above range, the cycle stability and kinetic performance of the battery can be better improved.

[0010] In some embodiments of this application, the surface of the inorganic solid electrolyte contains polar functional groups, including at least one of hydroxyl, carboxyl, sulfonic acid, and amide groups. The presence of these polar functional groups on the surface of the inorganic solid electrolyte particles results in better mechanical properties when interacting with the single-ion conductor polymer, thereby improving the mechanical stability of the interfacial coating and reducing the volume expansion of the active particles (i.e., the core material) during charge-discharge cycles.

[0011] In some embodiments of this application, the ratio of the average particle size of the nuclear material to the average particle size of the inorganic solid electrolyte is between 10 and 500. By adjusting the ratio of the average particle size of the nuclear material to the average particle size of the inorganic solid electrolyte within the above range, the energy density and cycle stability of the battery can be better improved.

[0012] In some embodiments of this application, the average particle size of the core material in the positive electrode active material is 10 μm to 50 μm; and / or, the average particle size of the core material in the negative electrode active material is 10 μm to 20 μm. By controlling the average particle size of the core material in the positive and negative electrode active materials within the above ranges, the energy density, kinetic performance, and cycle stability of the battery can be better improved.

[0013] In some embodiments of this application, the single-ion conductor polymer includes at least one of carboxylic acid type single-ion conductor polymer, sulfonic acid type single-ion conductor polymer, sulfonyl type single-ion conductor polymer, and boric acid type single-ion conductor polymer.

[0014] In some embodiments of this application, the secondary battery satisfies at least one of the following conditions:

[0015] (1) The average thickness of the coating layer is 0.1 μm to 2 μm; by adjusting the average thickness of the coating layer within the above range, it is more beneficial to improve the energy density, cycle stability and dynamic performance of the battery.

[0016] (2) The average particle size of the inorganic solid electrolyte is 100nm to 500nm. By adjusting the average particle size of the inorganic solid electrolyte within the above range, the battery can obtain better energy density and cycle stability.

[0017] (3) Inorganic solid electrolytes include at least one of the following compounds or compounds containing doped elements: Li with NASICON structure 1+x1 Al x1 Ge 2-x1 (PO4)3, Li 1+x2 Al x2 Ti 2-x2 (PO4)3, Li with perovskite structure 3x3 La 2 / 3- x3 TiO3, Li 3 / 8 Sr 7 / 16 Ta 3 / 4 Hf 1 / 4 O3, Li 2x4-y1 Sr 1-x4 Ta y1 Zr 1-y1 O3, Li with anti-perovskite structure 3-2x5 M x5 HalO, anti-perovskite structure Li3OCl, LISICON structure Li 4-x6 Si 1-x6 P x6 O4, Li 14 ZnGe4O 16 Li with garnet structure 7- x7 La3Zr 2-x7 O 12Wherein, 0 < x1 ≤ 0.75, 0 < x2 ≤ 0.5, 0.1 ≤ x3 ≤ 0.3, 0.25 ≤ y1 ≤ 1, x4 = 0.75y1, 0 ≤ x5 ≤ 0.01, 0.5 ≤ x6 ≤ 0.6, 0 ≤ x7 < 1, M includes at least one of Mg, Ca, Sr or Ba, Hal includes at least one of Cl or I; the doping element includes at least one of Sn, Si, Ge, Sr, Ta or Ce.

[0018] A second aspect of this application provides an electronic device that includes the secondary battery provided in the first aspect of this application.

[0019] Compared with the prior art, the beneficial effects of this application are as follows:

[0020] This application uses positive or negative electrode active particles as core materials and forms a stable solid interface coating layer on the surface of the core material through the interaction of a single-ion conductor with an inorganic solid electrolyte. The solid interface coating layer has good mechanical strength and flexibility, which can not only enhance the mechanical strength of the positive or negative electrode active particles to alleviate the stress generated by their volume expansion during charging and discharging and thus enhance their structural stability, but also reduce the side reactions on the surface of the positive or negative electrode active particles and construct efficient ion transport channels to enhance the migration ability of cations, thereby improving the kinetic performance and cycle performance of the secondary battery. Attached Figure Description

[0021] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other embodiments can be obtained based on these drawings.

[0022] Figure 1 This is a schematic diagram of positive electrode active material or negative electrode active material particles in a secondary battery according to an embodiment of this application. Detailed Implementation

[0023] To better illustrate the purpose, technical solution, and advantages of this application, the following description, in conjunction with specific embodiments and comparative examples, aims to provide a detailed understanding of the content of this application, rather than limiting it. All other embodiments obtained by those skilled in the art without inventive effort are within the protection scope of this application. Unless otherwise specified, the experimental reagents and instruments involved in the implementation of this application are all commonly used reagents and instruments.

[0024] It should be noted that, in the specific embodiments of this application, lithium-ion batteries are used as an example of secondary batteries to explain this application, but the secondary batteries in this application are not limited to lithium-ion batteries.

[0025] In a first aspect of the present application, a secondary battery is provided, which includes a positive electrode sheet, an electrolyte, and a negative electrode sheet. The positive electrode sheet includes a positive electrode current collector and a positive electrode material layer provided on at least one surface of the positive electrode current collector. The positive electrode material layer includes a positive electrode active material; the negative electrode sheet includes a negative electrode current collector and a negative electrode material layer provided on at least one surface of the negative electrode current collector. The negative electrode material layer includes a negative electrode active material; the positive electrode active material and / or the negative electrode active material includes a core material and a coating layer located on at least part of the surface of the core material. The coating layer includes a single-ion conductor polymer and an inorganic solid electrolyte.

[0026] In the present application, the positive or negative electrode active particles are used as the core material, and a stable solid-state interface coating layer is formed on the surface of the core material through the interaction between the single-ion conductor and the inorganic solid electrolyte. The solid-state interface coating layer has good mechanical strength and flexibility. It can not only enhance the mechanical strength of the positive or negative electrode active particles to relieve the stress generated by volume expansion during charge and discharge to enhance its structural stability, but also reduce the side reactions on the surface of the positive or negative electrode active particles, and construct an efficient ion transport channel to enhance the migration ability of cations, thereby improving the kinetic performance and cycling performance of the secondary battery.

[0027] There is no particular limitation on the type of the negative electrode active particles in the present application, as long as the purpose of the present application can be achieved. For example, the negative electrode active particles can be natural graphite, artificial graphite, mesocarbon microbeads (MCMB), hard carbon, soft carbon, silicon, silicon-carbon composite, SiO x (0.5 < x < 1.6), or at least one of them. In addition, there is no particular limitation on the type of the positive electrode active particles in the present application, as long as the purpose of the present application can be achieved. For example, the positive electrode active particles can be at least one of lithium cobalt oxide (LCO), lithium nickel cobalt manganese oxide (NCM811, NCM622, NCM523, NCM111), lithium nickel manganese aluminate, lithium iron phosphate, lithium vanadium phosphate, lithium cobalt phosphate, lithium manganese phosphate, lithium manganese iron phosphate, lithium iron silicate, lithium vanadium silicate, lithium cobalt silicate, lithium manganese silicate, spinel-type lithium manganate, spinel-type lithium nickel manganate, and lithium titanate.

[0028] There is no particular limitation on the type of the secondary battery in the present application. It can include any device that undergoes an electrochemical reaction, including liquid batteries, semi-solid batteries, and solid-state batteries. The secondary battery in the present application can include, but is not limited to, lithium metal secondary batteries, lithium-ion secondary batteries (lithium-ion batteries), lithium polymer secondary batteries, lithium-ion polymer secondary batteries (lithium-ion polymer batteries), etc.

[0029] In some embodiments of the present application, in the infrared spectrum of the positive electrode active material or the negative electrode active material, at a wavenumber of 900 cm -1 to 2500 cm -1An infrared absorption peak is present at the location. The infrared absorption peaks in this wavenumber range are mainly characteristic peaks of carboxylic acid groups (-COO-), sulfonic acid groups (-SO3-), sulfonyl groups (-SO2N(-)SO2), and borate groups (-BO3-). Carboxylic acid groups, sulfonic acid groups, sulfonyl groups, or borate groups can all promote the dissociation of lithium ions and interact with lithium ions to promote lithium ion transport.

[0030] In some embodiments of this application, the transmittance of the infrared absorption peak is between 20% and 60%. For example, the transmittance of the infrared absorption peak can be 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, or a range of any two of these values. The transmittance of the infrared absorption peak can, to some extent, reflect the amount of carboxylic acid groups, sulfonic acid groups, sulfonyl groups, or borate groups in the positive or negative electrode active material. Studies have found that by controlling the infrared transmittance of the infrared absorption peak within the above-mentioned range, the battery can achieve better energy density and kinetic performance.

[0031] In some embodiments of this application, the inorganic solid electrolyte content is 0.5% to 2% by mass, based on the mass of the positive electrode material layer; and / or, the inorganic solid electrolyte content is 0.5% to 2% by mass, based on the mass of the negative electrode material layer. For example, the mass percentage of inorganic solid electrolyte in the positive electrode material layer can be 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1%, 1.1%, 1.2%, 1.3%, 1.4%, 1.5%, 1.6%, 1.7%, 1.8%, 1.9%, 2%, or any combination of two of these values; the mass percentage of inorganic solid electrolyte in the negative electrode material layer can be 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1%, 1.1%, 1.2%, 1.3%, 1.4%, 1.5%, 1.6%, 1.7%, 1.8%, 1.9%, 2%, or any combination of two of these values. By controlling the mass percentage of inorganic solid electrolyte in the positive or negative electrode material layer within the above ranges, the cycle stability and kinetic performance of the battery can be better improved.

[0032] In some embodiments of this application, the surface of the inorganic solid electrolyte contains polar functional groups, including at least one of hydroxyl, carboxyl, sulfonic acid, and amide groups. The presence of these polar functional groups on the surface of the inorganic solid electrolyte particles results in better mechanical properties when interacting with the single-ion conductor polymer, thereby improving the mechanical stability of the interfacial coating and reducing the volume expansion of the active particles (i.e., the core material) during charge-discharge cycles.

[0033] In some embodiments of this application, the ratio of the average particle size of the core material to the average particle size of the inorganic solid electrolyte is between 10 and 500. The ratio of the average particle size of the core material to the average particle size of the inorganic solid electrolyte in the positive or negative electrode active material can be 10, 30, 33.3, 50, 100, 150, 166.7, 200, 250, 300, 350, 400, 450, 500, or a range of any two of these values. Preferably, the ratio of the average particle size of the core material to the average particle size of the inorganic solid electrolyte is between 30 and 200. By controlling the ratio of the average particle size of the core material to the average particle size of the inorganic solid electrolyte within the above range, the energy density and cycle stability of the battery can be better improved.

[0034] In some embodiments of this application, the average particle size of the core material in the positive electrode active material is from 10 μm to 50 μm, for example, it can be 10 μm, 15 μm, 20 μm, 25 μm, 30 μm, 35 μm, 40 μm, 45 μm, 50 μm, or any two of these values; and / or, the average particle size of the core material in the negative electrode active material is from 10 μm to 20 μm, for example, it can be 10 μm, 11 μm, 12 μm, 13 μm, 14 μm, 15 μm, 16 μm, 17 μm, 18 μm, 19 μm, 20 μm, or any two of these values. By controlling the average particle size of the core material in the positive and negative electrode active materials within the above ranges, the energy density, kinetic performance, and cycle stability of the battery can be better improved.

[0035] In some embodiments of this application, the single-ion conductor polymer includes at least one of carboxylic acid type single-ion conductor polymers, sulfonic acid type single-ion conductor polymers, sulfonyl type single-ion conductor polymers, and boric acid type single-ion conductor polymers. For example, the single-ion conductor polymer can be at least one of polyester sulfonate, copolymer of benzene sulfonate and PEO, P(STFSILi)-b-PEO-bP(STFSILi), polyurethane single-ion conductor, PSTFSI / PEO, LiPSsTFSI / PEO, LiBAMB-PETMP, LiPVAOB, and LiPSIPA (lithium-modified poly(benzenesulfonylimide ester amide benzenesulfonamide) / PVDF-HFP).

[0036] In some embodiments of this application, the secondary battery satisfies at least one of the following conditions:

[0037] (1) The average thickness of the coating layer is 0.1 μm to 2 μm, for example, it can be 0.1 μm, 0.2 μm, 0.3 μm, 0.5 μm, 1 μm, 2 μm or any two of these values; by adjusting the average thickness of the coating layer within the above range, it is more beneficial to improve the energy density, cycle stability and dynamic performance of the battery.

[0038] (2) The average particle size of the inorganic solid electrolyte is 100nm to 500nm; for example, the average particle size of the inorganic solid electrolyte can be 100nm, 150nm, 200nm, 250nm, 300nm, 350nm, 400nm, 450nm, 500nm or any two of these values; by adjusting the average particle size of the inorganic solid electrolyte within the above range, the battery can obtain better energy density and cycle stability.

[0039] (3) Inorganic solid electrolytes include at least one of the following compounds or compounds containing doped elements: Li with NASICON structure 1+x1 Al x1 Ge 2-x1 (PO4)3, Li 1+x2 Al x2 Ti 2-x2 (PO4)3, Li with perovskite structure 3x3 La 2 / 3- x3 TiO3, Li 3 / 8 Sr 7 / 16 Ta 3 / 4 Hf 1 / 4 O3, Li 2x4-y1 Sr 1-x4 Ta y1 Zr 1-y1 O3, Li with anti-perovskite structure 3-2x5 M x5 HalO, anti-perovskite structure Li3OCl, LISICON structure Li 4-x6 Si 1-x6 P x6 O4, Li 14 ZnGe4O 16 Li with garnet structure 7- x7 La3Zr 2-x7 O 12Wherein, 0 < x1 ≤ 0.75, 0 < x2 ≤ 0.5, 0.1 ≤ x3 ≤ 0.3, 0.25 ≤ y1 ≤ 1, x4 = 0.75y1, 0 ≤ x5 ≤ 0.01, 0.5 ≤ x6 ≤ 0.6, 0 ≤ x7 < 1, M includes at least one of Mg, Ca, Sr or Ba, Hal includes at least one of Cl or I; the doping element includes at least one of Sn, Si, Ge, Sr, Ta or Ce.

[0040] The negative electrode sheet in the secondary battery of this application includes a negative electrode current collector and a negative electrode material layer located on at least one side surface of the negative electrode current collector. The negative electrode material layer comprises a negative electrode active material, a negative electrode binder, and a negative electrode dispersant. This application does not impose any particular limitation on the mass ratio of the negative electrode active material, the negative electrode binder, and the negative electrode dispersant in the negative electrode material layer. Those skilled in the art can select them according to actual needs, as long as the purpose of this application can be achieved.

[0041] The aforementioned "negative electrode material layer located on at least one surface of the negative electrode current collector" means that the negative electrode material layer can be located on one surface of the negative electrode current collector along its own thickness direction, or it can be located on two surfaces of the negative electrode current collector along its own thickness direction. The "surface" can be the entire area of ​​the negative electrode current collector surface, or it can be a part of the negative electrode current collector surface. This application has no particular limitation, as long as the purpose of this application can be achieved.

[0042] This application does not impose any particular restrictions on the negative electrode current collector, as long as it achieves the purpose of this application. For example, the negative electrode current collector may include, but is not limited to, copper foil, aluminum foil, nickel foil, stainless steel foil, titanium foil, foamed nickel, foamed copper, carbon-coated aluminum foil, carbon-coated copper foil, lithium-copper composite current collector, carbon-copper composite current collector, nickel-copper composite current collector, titanium-copper composite current collector, etc. This application also does not impose any particular restrictions on the thickness of the negative electrode current collector or the negative electrode material layer on its surface, as long as it achieves the purpose of this application.

[0043] This application does not impose any particular restrictions on the types of negative electrode binders and negative electrode dispersants, as long as they can achieve the purpose of this application. For example, negative electrode binders may include, but are not limited to, polyacrylates, polyimides, polyamides, polyamide-imides, polyvinylidene fluoride, styrene-butadiene rubber, sodium alginate, polyvinyl alcohol, polytetrafluoroethylene, polyacrylonitrile, sodium carboxymethyl cellulose, potassium carboxymethyl cellulose, sodium hydroxymethyl cellulose, potassium hydroxymethyl cellulose, etc.; negative electrode dispersants may include, but are not limited to, carboxymethyl cellulose, sodium carboxymethyl cellulose, etc.

[0044] The positive electrode in the secondary battery of this application includes a positive current collector and a positive electrode material layer located on at least one side surface of the positive current collector. The positive electrode material layer comprises a positive electrode active material, a positive electrode binder, and a positive electrode conductive agent. This application does not impose any particular limitation on the mass ratio of the positive electrode active material, the positive electrode binder, and the positive electrode conductive agent in the positive electrode material layer. Those skilled in the art can select them according to actual needs, as long as the purpose of this application can be achieved.

[0045] The aforementioned "positive electrode material layer located on at least one surface of the positive electrode current collector" means that the positive electrode material layer can be located on one surface of the positive electrode current collector along its own thickness direction, or it can be located on two surfaces of the positive electrode current collector along its own thickness direction. The "surface" can be the entire area of ​​the surface of the positive electrode current collector, or it can be a part of the surface of the positive electrode current collector. This application has no particular limitation, as long as the purpose of this application can be achieved.

[0046] This application does not impose any particular restrictions on the positive electrode current collector, as long as it achieves the purpose of this application. For example, the positive electrode current collector may include, but is not limited to, copper foil, aluminum foil, nickel foil, stainless steel foil, titanium foil, carbon-coated aluminum foil, carbon-coated copper foil, lithium-copper composite current collector, carbon-copper composite current collector, nickel-copper composite current collector, titanium-copper composite current collector, etc. This application does not impose any particular restrictions on the thickness of the positive electrode current collector or the positive electrode material layer on the surface of the positive electrode current collector, as long as it achieves the purpose of this application.

[0047] This application does not impose any particular restrictions on the types of positive electrode binders and positive electrode conductive agents, as long as they can achieve the purpose of this application. For example, positive electrode binders may include, but are not limited to, polyacrylates, polyimides, polyamides, polyamide-imides, polyvinylidene fluoride, styrene-butadiene rubber, sodium alginate, polyvinyl alcohol, polytetrafluoroethylene, polyacrylonitrile, sodium carboxymethyl cellulose, potassium carboxymethyl cellulose, sodium hydroxymethyl cellulose, potassium hydroxymethyl cellulose, etc.; positive electrode conductive agents may include, but are not limited to, conductive carbon black, carbon nanotubes, carbon fibers, flake graphite, Ketjen black, graphene, metallic materials (copper, nickel, aluminum, or silver), conductive polymers (polyphenylene derivatives, polyaniline, polythiophene, polyacetylene, or polypyrrole), etc.

[0048] The secondary battery of this application also includes a separator, which separates the positive electrode and the negative electrode to prevent internal short circuits in the secondary battery. The separator allows electrolyte ions to pass freely without affecting the electrochemical charging and discharging process. This application does not impose any particular limitations on the separator, as long as it can achieve the purpose of this application. For example, the material of the separator can include, but is not limited to, polyethylene, polyolefins mainly composed of polypropylene, polyesters (such as polyethylene terephthalate membranes), cellulose, polyimide, polyamide, spandex, aramid, etc.; the type of separator can include woven membranes, nonwoven membranes, microporous membranes, composite membranes, rolled membranes, spun membranes, etc.

[0049] The diaphragm of this application may include a base membrane and a coating on at least one surface of the base membrane. The base membrane may be a nonwoven fabric or composite membrane with a porous structure. For example, the base membrane may be a polypropylene porous membrane, a polyethylene porous membrane, a polypropylene nonwoven fabric, a polyethylene nonwoven fabric, a polypropylene-polyethylene-polypropylene porous composite membrane, etc. The coating may be a polymer layer, an inorganic layer, or a mixture layer formed by a polymer and an inorganic material. The inorganic particles in the coating may include at least one of alumina, 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.

[0050] The secondary battery of this application also includes an electrolyte, which comprises a lithium salt and an organic solvent. This application does not impose any particular limitation on the mass percentage of lithium salt and organic solvent in the electrolyte, as long as the purpose of this application is achieved. This application does not impose any particular limitation on the type of lithium salt, as long as the purpose of this application is achieved, lithium salts known in the art can be used, such as lithium hexafluorophosphate, lithium bis(fluorosulfonyl)imide, lithium bis(fluorosulfonyl)imide, lithium difluorophosphate, lithium bis(oxalato)borate, lithium difluorooxalato)borate, etc. This application does not impose any particular limitation on the organic solvent, as long as the purpose of this application is achieved. For example, the organic solvent can include carbonate compounds, carboxylic acid ester compounds, ether compounds, or other organic solvents (such as dimethyl sulfoxide, 1,2-dioxolane, sulfolane, methyl sulfolane, 1,3-dimethyl-2-imidazolium ketone, N-methyl-2-pyrrolidone, formamide, dimethylformamide, acetonitrile, trimethyl phosphate, triethyl phosphate, trioctyl phosphate, or phosphate esters).

[0051] The second aspect of this application provides an electronic device that includes the secondary battery provided in the first aspect of this application. This application does not particularly limit the specific types of electronic devices; for example, electronic devices may include, but are not limited to, laptops, pen-based computers, mobile computers, e-book players, portable telephones, portable fax machines, portable copiers, portable printers, stereo 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, large household batteries, and lithium-ion capacitors, etc.

[0052] To clearly understand the technical solution of this application, the following detailed description of this application is provided in conjunction with specific embodiments and comparative examples. These embodiments should not be construed as limiting the scope of protection claimed in this application.

[0053] Test methods and equipment

[0054] 1. Infrared absorption peak transmittance test

[0055] The positive or negative electrode sheet was immersed and rinsed in DMC (dimethyl carbonate) (to remove the electrolyte), dried, and then the positive or negative electrode material layer powder was scraped off. The powder was then measured using a NEXUS FT-IR670 Fourier transform infrared spectrometer in the wavenumber range of 400-4000 cm⁻¹. -1 Infrared spectrum; then, based on the light intensity ratio before and after transmission through the sample, the transmittance is calculated: T = (I sample / I background )×100%, where I is the light intensity value.

[0056] 2. Average particle size test

[0057] The positive or negative electrode sheet was cut and polished by a cross-section polisher (model IB-09010CP) using high-energy ion beam. The obtained cross-section samples were observed under a scanning electron microscope (SEM). The positive electrode active material particles, negative electrode active material particles, and inorganic solid electrolyte particles were identified based on the measured element types. The average particle size of the core material and the average particle size of the inorganic solid electrolyte were also measured.

[0058] 3. Test of the mass percentage of inorganic solid electrolyte in the electrode material layer

[0059] The test was conducted using an inductively coupled plasma optical emission spectrometer (ICP-OES). 3g of the positive electrode material layer powder was dissolved in 30mL of aqua regia (obtained by mixing 36% hydrochloric acid and 65% nitric acid in a volume ratio of 3:1) for digestion. The digested solution was then injected into an inductively coupled plasma optical emission spectrometer (Thermo Fisher iCAP PRO XP ICP-OES) for testing. The mass percentage of inorganic solid electrolyte in the positive electrode material layer was obtained by the test.

[0060] 4. Average thickness test of the coating layer

[0061] The electrode material layer was sliced ​​using focused ion beam (FIB) and then characterized using a high-resolution transmission electron microscope (HRTEM, model Talos F200X). Within the same selected area (500,000x magnification), the thickness of the coating layer on the surface of the core material was measured at five randomly selected locations. The arithmetic mean of the coating layer thickness at the five different locations was calculated to obtain the average thickness of the coating layer.

[0062] 5. Ratio Performance Test

[0063] At 25℃, a lithium-ion full battery was charged at a constant current of 0.5C to 4.45V, then charged at a constant voltage of 4.45V until the current reached 0.025C. After resting for 5 minutes, it was discharged at a constant current of 0.5C to 3V, and the discharge capacity was recorded as the 0.5C discharge capacity. After resting for 5 minutes, it was charged again at a constant current of 0.5C to 4.45V, then charged at a constant voltage of 4.45V until the current reached 0.025C. After resting for 5 minutes, it was discharged at a constant current of 3C to 3V, and the discharge capacity was recorded as the 3C discharge capacity. The 3C discharge capacity retention rate of the lithium-ion battery (%) = 3C discharge capacity / 0.5C discharge capacity × 100%.

[0064] 6. Cyclic performance test

[0065] At 25℃, the lithium-ion full battery was charged at a constant current of 0.5C to 4.45V, then charged at a constant voltage of 4.45V to 0.025C, allowed to stand for 5 minutes, and then discharged at a constant current of 0.5C to 3V. This constitutes one charge-discharge cycle. The discharge capacity of the first cycle is recorded as C0. 100 charge-discharge cycles are performed in the same manner, and the discharge capacity after the 100th cycle is recorded as C100. The capacity retention rate (%) of the lithium-ion battery after 100 cycles = C100 / C0 × 100%.

[0066] Example 1

[0067] <Preparation of the positive electrode>

[0068] (1) Inorganic solid electrolyte particles and cage-type polysilsesquioxane (POSS) were added to NMP solvent at a mass ratio of 3:1, and after being stirred and dispersed at room temperature, they were centrifuged and dried to obtain modified inorganic solid electrolyte particles.

[0069] (2) The positive electrode active particles, conductive carbon black (Super P) and positive electrode binder (polyvinylidene fluoride) are mixed in a mass ratio of 97:1.4:1.6. N-methylpyrrolidone (NMP) is added as a solvent to prepare a positive electrode slurry with a solid content of 72wt%. After vacuum stirring, the positive electrode slurry is obtained.

[0070] (3) After uniformly mixing the precursor of the single-ion conductor polymer and the modified inorganic solid electrolyte particle dispersion slurry (solvent is NMP), it is added to the positive electrode slurry (the total amount of the single-ion conductor polymer precursor and the modified inorganic solid electrolyte particles is 1% by mass relative to the positive electrode active particles). The single-ion conductor polymer precursor undergoes an in-situ crosslinking reaction on the surface of the positive electrode active particles to form a coating layer (structural schematic diagram is shown below). Figure 1 As shown), the modified cathode slurry was obtained;

[0071] (4) The modified positive electrode slurry was uniformly coated on one side of a 12 μm thick aluminum foil used as a positive electrode current collector, and dried at 85°C to obtain a positive electrode sheet with a single-sided coated positive electrode material layer. The coating weight of the positive electrode material layer was 19 mg / cm³. 2 Then, the above steps are repeated on the other side of the aluminum foil to obtain a positive electrode sheet with a double-sided coating of positive electrode material. After cold pressing, cutting, and slitting, it is dried under vacuum at 85℃ for 4 hours to obtain a positive electrode sheet with dimensions of 74mm × 867mm for later use. The compaction density of the positive electrode material layer after cold pressing is 4.2 g / cm³. 3 .

[0072] <Preparation of Negative Electrode Sheets>

[0073] A negative electrode active material (graphite), styrene-butadiene rubber (SBP), and sodium carboxymethyl cellulose (CMC) were thoroughly mixed in an appropriate amount of deionized water at a weight ratio of 97:2:1 to form a uniform negative electrode slurry with a solid content of 40 wt%. The negative electrode slurry was coated onto one side of a copper foil current collector and dried at 85°C. After cold pressing, cutting, and slitting, it was dried under vacuum at 120°C for 12 hours to obtain a single-sided coated negative electrode sheet. The above steps were repeated on the other side of the copper foil in the single-sided coated negative electrode sheet to obtain a double-sided coated negative electrode sheet. This was then cold-pressed, cut, and slitting, and dried under vacuum at 120°C for 12 hours to obtain a negative electrode sheet with dimensions of 78 mm × 875 mm for later use. The compaction density of the negative electrode material layer after cold pressing was 1.7 g / cm³. 3 .

[0074] <Preparation of Electrolyte>

[0075] In an argon-atmospheric glove box with a water content of less than 10 ppm, ethylene carbonate (EC), ethyl methyl carbonate (EMC), and diethyl carbonate (DEC) were mixed uniformly at a weight ratio of EC:EMC:DEC = 30:50:20 to obtain a base solvent. Then, lithium hexafluorophosphate (LiPF6) was added to the base solvent and mixed uniformly to obtain the electrolyte. The lithium salt content was 12.5% ​​by mass, with the remainder being the base solvent.

[0076] <Preparation of the diaphragm>

[0077] A porous polyethylene (PE) film with a thickness of 7 μm (supplied by Celgard) was used as the separator.

[0078] <Preparation of Lithium-ion Full Batteries>

[0079] The positive electrode, separator, and negative electrode are stacked in sequence, with the separator positioned between the positive and negative electrodes to provide insulation. This is then wound to form the electrode assembly. After welding the tabs, the electrode assembly is placed in an aluminum-plastic film packaging bag, dried at 80°C, and then injected with electrolyte. Following vacuum sealing, settling, formation, shaping, and capacity testing, a soft-pack lithium-ion battery is obtained, which is a lithium-ion full battery.

[0080] Examples 2 to 3

[0081] Except for the type of positive electrode active particles in the <Preparation of Positive Electrode Sheet>, which is different from that in Example 1, the rest is the same as in Example 1.

[0082] Examples 4 to 5

[0083] Except for the difference in the average particle size of the positive electrode active particles in the <Preparation of Positive Electrode Sheet> compared to Example 1, the rest is the same as in Example 1.

[0084] Examples 6 to 7

[0085] Except for the type of inorganic solid electrolyte particles used in the <Preparation of Positive Electrode Sheet>, which is different from that in Example 1, the rest is the same as in Example 1.

[0086] Examples 8 to 9

[0087] Except for the difference in the average particle size of the inorganic solid electrolyte particles in the <Preparation of Positive Electrode Sheet> compared to Example 1, the rest is the same as in Example 1.

[0088] Example 10

[0089] Except for the difference in the modified inorganic solid electrolyte particles used in the <Preparation of Positive Electrode Sheet> compared to Example 1, the rest is the same as in Example 1; the modified inorganic solid electrolyte particles were prepared by the following method:

[0090] (1) Preparation of silane solution: Carboxypropyltriethoxysilane was dissolved in anhydrous ethanol to obtain a silane solution with a concentration of 2wt%;

[0091] (2) Grafting reaction: The inorganic solid electrolyte particles were immersed in a silane solution and stirred at 80°C for 4 hours. After the reaction was completed, the inorganic solid electrolyte particles were washed multiple times with an anhydrous solvent to remove unreacted silane. Then, they were dried under vacuum at 60°C to obtain the modified inorganic solid electrolyte particles.

[0092] Example 11

[0093] Except for the difference in the modified inorganic solid electrolyte particles used in the <Preparation of Positive Electrode Sheet> compared to Example 1, the rest is the same as in Example 1; the modified inorganic solid electrolyte particles were prepared by the following method:

[0094] (1) Preparation of silane solution: Silane reagent 3-(trimethoxysilyl)propane-1-sulfonic acid was dissolved in anhydrous ethanol, and triethylamine was added as catalyst to obtain silane solution; wherein the concentration of silane reagent was 3wt% and the concentration of triethylamine was 0.2wt%.

[0095] (2) Grafting reaction: The inorganic solid electrolyte particles were immersed in a silane solution and stirred at 70°C for 12 hours. After the reaction was completed, the inorganic solid electrolyte particles were washed multiple times with anhydrous solvent to remove unreacted silane. Then, they were vacuum dried at 60°C to obtain the modified inorganic solid electrolyte particles.

[0096] Examples 12 to 13

[0097] Except for the fact that the amount of modified inorganic solid electrolyte particles added was adjusted in the <Preparation of Positive Electrode Sheet> so that the mass percentage of inorganic solid electrolyte in the positive electrode material layer was different from that in Example 1, the rest was the same as in Example 1.

[0098] Examples 14 to 15

[0099] Except for the type of single-ion conductor polymer used in the <Preparation of Positive Electrode>, which is different from that in Example 1, the rest is the same as in Example 1.

[0100] Examples 16 to 17

[0101] In addition to controlling the mass content of the single-ion conductor polymer precursor in the modified positive electrode slurry during the preparation of the positive electrode sheet, the positive electrode active material was able to achieve a wavenumber of 900 cm⁻¹. -1 Up to 2500cm -1 The transmittance of the infrared absorption peak at the location is different from that in Example 1, but the rest is the same as in Example 1.

[0102] Examples 18 to 19

[0103] Except for the difference in the preparation of the positive electrode sheet, where the average thickness of the coating layer in the positive electrode active material differs from that in Example 1 by adjusting the mass content of the single-ion conductor polymer precursor in the modified positive electrode slurry, the rest is the same as in Example 1. Increasing the mass content of the single-ion conductor polymer precursor can increase the average thickness of the coating layer in the positive electrode active material.

[0104] Example 20

[0105] Except for the fact that the inorganic solid electrolyte particles were not modified in the <Preparation of Positive Electrode Sheet> (that is, the precursor of the single-ion conductor polymer and the inorganic solid electrolyte particle dispersion slurry were directly added to the positive electrode slurry), the rest is the same as in Example 1.

[0106] Comparative Example 1

[0107] Except for the preparation of the positive electrode sheet, which differs from Example 1, the rest is the same as Example 1;

[0108] <Preparation of the positive electrode>

[0109] The positive electrode active particles (NCM811), conductive carbon black (Super P) and positive electrode binder (polyvinylidene fluoride) were mixed at a mass ratio of 97:1.4:1.6. N-methylpyrrolidone (NMP) was added as a solvent to prepare a positive electrode slurry with a solid content of 72wt%. The slurry was then stirred evenly under vacuum to obtain the positive electrode slurry.

[0110] The positive electrode slurry was uniformly coated onto one side of a 12 μm thick aluminum foil used as a positive electrode current collector, and then dried at 85°C to obtain a positive electrode sheet with a single-sided coating of the positive electrode material layer. The coating weight of the positive electrode material layer was 19 mg / cm³. 2 Then, the above steps are repeated on the other side of the aluminum foil to obtain a positive electrode sheet with a double-sided coating of positive electrode material. After cold pressing, cutting, and slitting, it is dried under vacuum at 85℃ for 4 hours to obtain a positive electrode sheet with dimensions of 74mm × 867mm for later use. The compaction density of the positive electrode material layer after cold pressing is 4.2 g / cm³. 3 .

[0111] Comparative Example 2

[0112] Except for the preparation of the positive electrode sheet, which differs from Example 1, the rest is the same as Example 1;

[0113] Positive electrode active particles (NCM811), conductive carbon black (Super P), and positive electrode binder (polyvinylidene fluoride) were mixed at a mass ratio of 97:1.4:1.6. N-methylpyrrolidone (NMP) was added as a solvent to prepare a positive electrode slurry with a solid content of 72 wt%. After vacuum stirring, the slurry was obtained. A precursor of a single-ion conductor polymer (1% by mass relative to the positive electrode active particles) was added to the positive electrode slurry. The precursor of the single-ion conductor polymer crosslinked in situ on the surface of the positive electrode active particles to form a coating layer, resulting in a modified positive electrode slurry.

[0114] The modified positive electrode slurry was uniformly coated onto one side of a 12 μm thick aluminum foil used as a positive electrode current collector, and then dried at 85°C to obtain a positive electrode sheet with a single-sided coated positive electrode material layer. The coating weight of the positive electrode material layer was 19 mg / cm³. 2Then, the above steps are repeated on the other side of the aluminum foil to obtain a positive electrode sheet with a double-sided coating of positive electrode material. After cold pressing, cutting, and slitting, it is dried under vacuum at 85℃ for 4 hours to obtain a positive electrode sheet with dimensions of 74mm × 867mm for later use. The compaction density of the positive electrode material layer after cold pressing is 4.2 g / cm³. 3 .

[0115] Table 1

[0116]

[0117]

[0118] Table 2

[0119]

[0120] Table 3

[0121]

[0122] In Table 3, " / " indicates that there are no relevant parameters.

[0123] According to the data in Tables 1, 2 and 3, the capacity retention rate of the lithium-ion full batteries in Examples 1 to 20 after 100 cycles is greater than or equal to 91%, and the capacity retention rate under 3C discharge conditions is greater than or equal to 90%, indicating that the secondary battery of this application has both good kinetic performance and excellent cycle performance.

[0124] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit the scope of protection of the present invention. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the essence and scope of the technical solutions of the present invention.

Claims

1. A secondary battery, comprising a positive electrode and a negative electrode, characterized in that, The positive electrode includes a positive current collector and a positive electrode material layer disposed on at least one surface of the positive current collector, the positive electrode material layer including a positive active material; the negative electrode includes a negative current collector and a negative electrode material layer disposed on at least one surface of the negative current collector, the negative electrode material layer including a negative active material; the positive active material and / or the negative active material includes a core material and a coating layer located on at least a portion of the surface of the core material, the coating layer including a single-ion conductor polymer and an inorganic solid electrolyte.

2. The secondary battery as described in claim 1, characterized in that, In the infrared spectrum of the positive or negative electrode active material, at a wavenumber of 900 cm⁻¹ -1 Up to 2500cm -1 An infrared absorption peak is present at the location.

3. The secondary battery as described in claim 2, characterized in that, The transmittance of the infrared absorption peak is 20% to 60%.

4. The secondary battery as described in claim 1, characterized in that, Based on the mass of the positive electrode material layer, the mass percentage of the inorganic solid electrolyte is 0.5% to 2%. And / or, based on the mass of the negative electrode material layer, the mass percentage of the inorganic solid electrolyte is 0.5% to 2%.

5. The secondary battery as described in claim 1, characterized in that, The surface of the inorganic solid electrolyte contains polar functional groups, including at least one of hydroxyl, carboxyl, sulfonic acid, and amide groups.

6. The secondary battery as described in claim 1, characterized in that, The ratio of the average particle size of the nuclear material to the average particle size of the inorganic solid electrolyte is 10 to 500.

7. The secondary battery as described in claim 1, characterized in that, The average particle size of the core material in the positive electrode active material is 10 μm to 50 μm; and / or, The average particle size of the core material in the negative electrode active material is 10 μm to 20 μm.

8. The secondary battery as described in claim 1, characterized in that, The single-ion conductor polymer includes at least one of carboxylic acid type single-ion conductor polymer, sulfonic acid type single-ion conductor polymer, sulfonyl type single-ion conductor polymer, and boric acid type single-ion conductor polymer.

9. The secondary battery as described in claim 1, characterized in that, The secondary battery satisfies at least one of the following conditions: (1) The average thickness of the coating layer is 0.1 μm to 2 μm; (2) The average particle size of the inorganic solid electrolyte is 100 nm to 500 nm; (3) The inorganic solid electrolyte comprises at least one of the following compounds or compounds containing doped elements: Li with NASICON structure 1+x1 Al x1 Ge 2-x1 (PO4)3, Li 1+x2 Al x2 Ti 2-x2 (PO4)3, Li with perovskite structure 3x3 La 2 / 3- x3 TiO3, Li 3 / 8 Sr 7 / 16 Ta 3 / 4 Hf 1 / 4 O3, Li 2x4-y1 Sr 1-x4 Ta y1 Zr 1-y1 O3, Li with anti-perovskite structure 3-2x5 M x5 HalO, anti-perovskite structure Li3OCl, LISICON structure Li 4-x6 Si 1-x6 P x6 O4, Li 14 ZnGe4O 16 Li with garnet structure 7- x7 La3Zr 2-x7 O 12 Wherein, 0 < x1 ≤ 0.75, 0 < x2 ≤ 0.5, 0.1 ≤ x3 ≤ 0.3, 0.25 ≤ y1 ≤ 1, x4 = 0.75y1, 0 ≤ x5 ≤ 0.01, 0.5 ≤ x6 ≤ 0.6, 0 ≤ x7 < 1, M includes at least one of Mg, Ca, Sr or Ba, Hal includes at least one of Cl or I; the doping element includes at least one of Sn, Si, Ge, Sr, Ta or Ce.

10. An electronic device, characterized in that, Includes the secondary battery as described in any one of claims 1 to 9.

Images