Secondary battery and electronic device

Abstract

The invention belongs to the field of electrochemistry, and particularly discloses a secondary battery and an electronic device. The invention provides a secondary battery which comprises a negative pole piece, the negative pole piece comprises a current collector and a dielectric response layer, the dielectric response layer is arranged on at least one surface of the current collector, or the negative pole piece comprises the current collector, lithium metal and the dielectric response layer, the lithium metal is arranged between the current collector and the dielectric response layer; the relative dielectric constant of the dielectric response layer is 2-37; the dielectric response layer comprises an inorganic dielectric material and an organic polymer. According to the invention, the dielectric response layer is added in the negative electrode plate, and the dielectric response layer can inhibit lithium precipitation of the negative electrode, delay generation of lithium dendrites and improve the dynamic performance and cycle performance of the battery.

Description

Technical Field

[0001] The present application belongs to the field of electrochemistry, and specifically relates to a secondary battery and an electronic device. Background Art

[0002] With the rapid development of portable electronic devices (such as mobile phones and laptops) and new energy vehicles, there is a growing demand for lithium-ion and other secondary batteries with excellent electrical properties, such as high energy density, high discharge voltage, and high power. In particular, lithium-ion and other secondary batteries are required to have high energy density and high power in a short period of time to meet the demanding conditions that require long-term, repeated charging and discharging with high current in a short period of time. This allows secondary batteries to have a fast charging mode, making people's lives more convenient.

[0003] In lithium metal batteries, during charging, lithium ions are deintercalated from the positive electrode active material, conducted through the electrolyte, and deposited at the negative electrode. High-current rapid charging can easily lead to localized charge accumulation at the negative electrode, resulting in high tip voltages at these locations and uneven lithium deposition. Research has shown that unevenly deposited lithium metal tends to grow into dendrites. When dendrites break and lose electrical contact with the electrode, they lead to loss of active lithium and a decrease in capacity. Dendrite growth also increases interfacial impedance, polarization, and battery charge and discharge efficiency. Furthermore, dendrite growth can lead to battery short circuits and even extreme conditions such as combustion or explosion. Rapid charging, in particular, can accelerate uneven lithium deposition, dendrite growth, and electrolyte-mediated side reactions, resulting in a reduced battery cycle life. Therefore, there is a continued need to develop solutions that can inhibit lithium deposition at the negative electrode and improve the cycling stability of lithium secondary batteries to meet the demands of rapid charging. Summary of the Invention

[0004] In view of the above-mentioned problems existing in the prior art, the present application provides a secondary battery and an electronic device to improve the lithium plating phenomenon at the negative electrode and increase the cycle life of the secondary battery.

[0005] In a first aspect, the present application provides a secondary battery comprising a negative electrode plate, the negative electrode plate comprising a current collector and a dielectric response layer, the dielectric response layer being disposed on at least one surface of the current collector, or the negative electrode plate comprising a current collector, lithium metal and a dielectric response layer, the lithium metal being disposed between the current collector and the dielectric response layer; the relative dielectric constant of the dielectric response layer is 2 to 37; the dielectric response layer comprises an inorganic dielectric material and an organic polymer; the current collector comprises any one of copper foil, titanium foil, stainless steel, carbon paper and graphene paper.

[0006] The negative electrode sheet of the present application contains a dielectric response layer. During the charge and discharge process, the surface of the negative electrode lithium metal is in an electric field. Due to the presence of dielectric polarization, the dielectric response layer will generate a built-in electric field in the response layer. The built-in electric field can change the surrounding electric field and affect the surrounding charge distribution, thereby playing a role in uniform ion flux and reducing the local charge accumulation to present a high tip voltage. It can inhibit the lithium precipitation of the negative electrode, delay the generation of lithium dendrites, improve the kinetic performance, and significantly improve the cycle performance of the battery. At the same time, when the relative dielectric constant of the dielectric response layer is between 2 and 37, not only is the built-in electric field strength generated by the dielectric response layer sufficient to improve the charge distribution of the negative electrode, but it can also avoid the built-in electric field response generated by it being too strong, causing severe disturbances in the surrounding electric field, achieving a good uniform ion flux effect, and improving the kinetic performance and cycle performance of the battery.

[0007] In some embodiments, the inorganic dielectric material comprises 0.5% to 50% by weight of the dielectric response layer. Within this range, the dielectric response layer in the battery can effectively inhibit lithium deposition, further improving the battery's kinetics and cycling performance.

[0008] In some embodiments, the average particle size of the inorganic dielectric material is 0.01 μm to 20 μm. Below the above average particle size of the inorganic dielectric material, the dielectric response layer in the battery can effectively inhibit lithium plating, further improving the battery's kinetic performance and cycle performance.

[0009] In some embodiments, the inorganic dielectric material includes at least one of barium titanate or metal-doped barium titanate; the metal-doped barium titanate includes at least one of Li, Sr, Ca, Zr, Sn, La, Nd, or Sm. Using these inorganic dielectric materials, the dielectric response layer in the battery can effectively inhibit lithium plating, further improving the battery's kinetic and cycling performance.

[0010] In some embodiments, the thickness of the dielectric response layer is 1 μm to 30 μm. Under the above-mentioned thickness of the dielectric material, the dielectric response layer in the battery can effectively inhibit lithium plating and further improve the kinetic performance and cycle performance of the battery.

[0011] In some embodiments, the organic polymer includes at least one of polyacrylonitrile, polyvinylidene fluoride, polyethylene oxide, polyvinylidene fluoride-co-hexafluoropropylene, polylactic acid, or polyurea. Using these organic polymers, the dielectric response layer in the battery can better physically inhibit lithium deposition, further improving the battery's kinetic and cycling performance.

[0012] In some embodiments, the dielectric response layer further comprises a single-ion conductor polymer, the single-ion conductor polymer comprising at least one of polyacrylonitrile-lithium salt, polyethylene oxide-lithium salt, or polyvinylidene fluoride-co-hexafluoropropylene-lithium salt. Adding a single-ion conductor to the dielectric response layer can increase the ionic conductivity of the dielectric response layer, reduce concentration polarization, and further enhance the dielectric response layer's ability to inhibit lithium deposition. Using the aforementioned single-ion conductors, the dielectric response layer in the battery exhibits a greater ability to inhibit lithium deposition, further improving the battery's kinetic and cycling performance.

[0013] In some embodiments, the weight percentage of the single-ion conductor polymer is 10% to 70% based on the weight of the dielectric response layer. Setting the single-ion conductor polymer content within this range can further improve the battery's kinetic and cycling performance by further suppressing lithium deposition through the dielectric response layer.

[0014] In some embodiments, the mass ratio of the inorganic dielectric material to the single-ion conductive polymer in the dielectric response layer is 1:(0.1-0.7). When the mass ratio of the inorganic dielectric material to the single-ion conductive polymer is within the above range, the dielectric response layer can be more effective in suppressing lithium deposition, further improving the kinetic performance and cycle performance of the battery.

[0015] In a second aspect, an electronic device includes a secondary battery.

[0016] Beneficial effects of the present application: The present application adds a dielectric response layer at a specific position in the negative electrode plate. The dielectric response layer can inhibit lithium plating at the negative electrode, delay the formation of lithium dendrites, and improve the kinetic performance and cycle performance of the battery. DETAILED DESCRIPTION

[0017] To better illustrate the purpose, technical solutions, and advantages of this application, the technical solutions of this application will be clearly and completely described below in conjunction with the embodiments. Obviously, the embodiments described are only part of the embodiments of this application, rather than all the embodiments. The embodiments described herein are illustrative and are used to provide a basic understanding of this application. The embodiments of this application should not be interpreted as limiting this application.

[0018] For the sake of clarity, only some numerical ranges are specifically disclosed herein. However, any lower limit may be combined with any upper limit to form an unspecified range; and any lower limit may be combined with other lower limits to form an unspecified range, and similarly, any upper limit may be combined with any other upper limit to form an unspecified range. In addition, each individually disclosed point or single value may itself serve as a lower limit or upper limit and be combined with any other point or single value, or with other lower limits or upper limits, to form an unspecified range.

[0019] In the description herein, unless otherwise stated, "above", "below" include this number. Unless otherwise stated, the terms used in this application have the well-known meanings generally understood by those skilled in the art. Unless otherwise stated, the numerical value of each parameter mentioned in this application can be measured with various measuring methods commonly used in this area. In the description herein, the list of the items connected by the term "at least one of", "at least one of", "at least one of", "at least one of" or other similar terms can mean any combination of the listed items.

[0020] In order to improve the problem of lithium plating in the negative electrode of the battery, the present application provides a secondary battery, including a negative electrode plate, wherein the negative electrode plate includes a current collector and a dielectric response layer, and the dielectric response layer is arranged on at least one surface of the current collector, or the negative electrode plate includes a current collector, lithium metal and a dielectric response layer, and the lithium metal is arranged between the current collector and the dielectric response layer; the relative dielectric constant of the dielectric response layer is 2 to 37; the dielectric response layer includes an inorganic dielectric material and an organic polymer; the current collector includes any one of copper foil, titanium foil, stainless steel, carbon paper and graphene paper.

[0021] The negative electrode sheet of the present application contains a dielectric response layer. During the charge and discharge process, the surface of the negative electrode lithium metal is in an electric field. Due to the presence of dielectric polarization, the dielectric response layer will generate a built-in electric field in the response layer. The built-in electric field can change the surrounding electric field and affect the surrounding charge distribution, thereby playing a role in uniform ion flux and reducing the local charge accumulation to present a high tip voltage. It can inhibit the lithium precipitation of the negative electrode, delay the generation of lithium dendrites, improve the kinetic performance, and significantly improve the cycle performance of the battery. At the same time, when the relative dielectric constant of the dielectric response layer is between 2 and 37, not only is the built-in electric field strength generated by the dielectric response layer sufficient to improve the charge distribution of the negative electrode, but it can also avoid the built-in electric field response generated by it being too strong, causing severe disturbances in the surrounding electric field, achieving a good uniform ion flux effect, and making the battery have better kinetic performance and cycle stability.

[0022] In some embodiments, the relative dielectric constant of the dielectric responsive layer is 2 to 25, specifically, it can be 2, 4, 6, 8, 10, 12, 14, 16, 18, 20, 22, 24, 25, or a range consisting of any two of these values.

[0023] In some embodiments, the relative dielectric constant of the dielectric response layer is 12.5 to 14, specifically, 12.5, 13, 13.5, 14, or a range consisting of any two of these values. The relative dielectric constant of the dielectric response layer within the above range can further improve the negative electrode lithium plating phenomenon and further improve the kinetic performance and cycle performance of the battery.

[0024] In some embodiments, based on the mass of the dielectric response layer, the mass percentage of the inorganic dielectric material is 0.5% to 50%, specifically, it can be 0.5%, 1.5%, 5%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, or a range consisting of any two of these values. Within the above-mentioned content range of the inorganic dielectric material, the dielectric response layer in the battery can effectively inhibit lithium plating and improve the cycle performance of the battery. The mass percentage of the inorganic dielectric material can be measured by ICP (inductively coupled plasma) to test the metal element content in the inorganic dielectric material, and then converted to obtain the mass percentage of the inorganic dielectric material.

[0025] In some embodiments, the inorganic dielectric material has an average particle size of 0.01 μm to 20 μm, specifically 0.01 μm, 0.05 μm, 1 μm, 2 μm, 3 μm, 4 μm, 5 μm, 6 μm, 7 μm, 8 μm, 9 μm, 10 μm, 11 μm, 12 μm, 13 μm, 14 μm, 15 μm, 16 μm, 17 μm, 18 μm, 19 μm, 20 μm, or a range consisting of any two of these values. The differences in microstructure and dynamic dielectric response of inorganic dielectric materials with different particle sizes can affect the functionality of the dielectric response layer. When the average particle size of the inorganic dielectric material is within the above range, the probability of forming local "dielectric islands" can be reduced, thereby reducing the probability of local electric field concentration caused by sudden changes in the dielectric constant around the "dielectric islands", which leads to preferential deposition of lithium ions at the particle boundaries and the formation of dendrites. At the same time, it is more conducive to the formation of a continuous dielectric network, further effectively homogenizing the electric field, better suppressing local current density fluctuations, effectively inhibiting lithium plating, and further improving the cycle performance of the battery. The average particle size of the inorganic dielectric material can be tested using a laser particle size analyzer.

[0026] In some embodiments, the relative dielectric constant of the inorganic dielectric material is greater than 100, specifically 110 to 4800, specifically 110, 500, 1000, 1500, 2000, 3000, 3500, 4000, 4500, 4800, or a range consisting of any two of these values.

[0027] In some embodiments, the inorganic dielectric material includes at least one of barium titanate or metal element-doped barium titanate; in the metal element-doped barium titanate, the doped metal element includes at least one of Li, Sr, Ca, Zr, Sn, La, Nd or Sm.

[0028] In some embodiments, the metal element doped barium titanate comprises at least one compound having the following chemical formula: Li z Ba 1-zTiO3、Li z BaTi 1-z O3、Ba 1-x M x Ti 1-y N y O3、Li z Ba 1-x-z M x Ti 1-y N y O3、Li z Ba 1- x M x Ti 1-y-z N y O3, M and N are doping metal elements, M and N are independently selected from at least one of Sr, Ca, Zr, Sn, La, Nd or Sm, x and y are doping molar ratios, 0≤x≤0.2, 0≤y≤0.2, 0≤z≤0.1.

[0029] By using the above-mentioned inorganic dielectric materials, the dielectric response layer in the battery can effectively inhibit lithium plating and further improve the cycle performance of the battery.

[0030] In some embodiments, based on the total mass of the barium titanate doped with the metal element, the mass percentage of the doped metal element is 0.01%-5%. Specifically, it can be 0.01%, 0.05%, 0.1%, 0.5%, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5%, or a range consisting of any two of these values.

[0031] Inorganic dielectric materials can be obtained in a conventional manner, and can be obtained using commercial products or homemade methods. More specifically, for example, the inorganic dielectric material is lithium-doped barium titanate, and the preparation method of the lithium-doped barium titanate comprises the following steps: dissolving tetraisopropoxytitanium in isopropanol, and then adding barium hydroxide, lithium carbonate and ammonia water to obtain a mixture; transferring the mixture to a reactor and reacting it at 180 to 220°C for 8 to 24 hours. After the reaction is completed, the solvent is removed to obtain a solid intermediate; and then the solid intermediate is reacted at 500 to 700°C for 0.5 to 2 hours to obtain the lithium-doped barium titanate. In some embodiments, the molar ratio of the tetraisopropoxytitanium, barium hydroxide and lithium carbonate is 1:1:(0.1-1), and the concentration of the tetraisopropoxytitanium in the mixture is 0.5-2 mol / L, and the concentration of the ammonia water is 1-3 mol / L. For example, the inorganic dielectric material is a Li, Ca and Zr doped barium titanate based dielectric material, and the specific preparation method thereof includes the following steps: 0.85 Ca 0.15 Ti 0.9 Zr0.1 BaCO3, TiO2, CaCO3 and ZrO2 raw materials are weighed in a stoichiometric ratio of O3, and the BaCO3, TiO2, CaCO3 and ZrO2 raw materials are ball-milled in ethanol for the first time to obtain a mixed material; the mixed material is calcined for the first time; after the calcination is completed, lithium carbonate is added, ball-milled for a second time, and dried; after drying, the mixture is calcined for a second time in an air atmosphere for 1 to 3 hours to obtain a Li-, Ca- and Zr-doped barium titanate-based dielectric material. In some embodiments, the first ball milling time is 4 to 8 hours, the first calcination temperature is 1100°C to 1300°C, and the first calcination time is 1 to 3 hours; the second ball milling time is 4 to 8 hours, the second calcination temperature is 1300°C to 1500°C, and the second calcination time is 1 to 3 hours; the amount of lithium carbonate added is 0.01% to 0.5% of the total mass of BaCO3, TiO2, CaCO3 and ZrO2.

[0032] In some embodiments, the thickness of the dielectric response layer is 1 μm to 30 μm, specifically 1 μm, 5 μm, 10 μm, 15 μm, 20 μm, 25 μm, 30 μm, or a range consisting of any two of these values. Within the above-mentioned thickness of the dielectric material, the dielectric response layer in the battery can effectively inhibit lithium plating, and the negative electrode plate can have higher energy density and kinetic performance, which can further improve the cycle performance of the battery.

[0033] In some embodiments, the relative dielectric constant of the organic polymer is greater than 5, specifically 5-80, specifically 5, 10, 20, 30, 40, 50, 60, 70, 80, or a range consisting of any two of these values.

[0034] In some embodiments, the organic polymer includes at least one of polyacrylonitrile (PAN), polyvinylidene fluoride (PVDF), polyethylene oxide (PEO), polyvinylidene fluoride-co-hexafluoropropylene (PVDF-HFP), polylactic acid (PLA) or polyurea (PU). The above-mentioned organic polymer itself has a certain dielectric response function, but its dielectric response strength is generally lower than that of the inorganic dielectric material. It cooperates with the inorganic dielectric material to make the built-in electric field generated by the dielectric response layer uniform and of appropriate strength, and the above-mentioned organic polymer has good film-forming properties and can be used as a matrix for dispersing the inorganic dielectric material, so that the inorganic dielectric material in the dielectric response layer is evenly dispersed, which is beneficial for the dielectric response layer to exhibit a better lithium precipitation inhibition function; in addition, the above-mentioned organic polymer has good binding force with lithium metal or current collector, which can make the dielectric response layer well attached to lithium metal or current collector, which is beneficial for the dielectric response layer to contact with lithium metal or current collector, which is beneficial for improving the lithium precipitation inhibition effect, thereby improving the cycle stability of the battery.

[0035] In some embodiments, in the dielectric response layer, the mass ratio of the inorganic dielectric material to the organic polymer is 1:(1-20), which can specifically be 1:1, 1:3, 1:5, 1:7, 1:9, 1:11, 1:13, 1:15, 1:17, 1:20, or a range consisting of any two of these values. When the mass ratio of the inorganic dielectric material to the organic polymer is within the above range, the dielectric response layer can have a better effect in suppressing lithium plating, further improving the cycle stability of the battery.

[0036] In some embodiments, the dielectric responsive layer further comprises a single ion conductor polymer.

[0037] In some embodiments, the dielectric response layer is composed of a composite layer and a single ion conductor polymer layer stacked together, the composite layer is composed of an inorganic dielectric material and an organic polymer, and the single ion conductor polymer layer is composed of a single ion conductor polymer.

[0038] In some embodiments, the dielectric responsive layer is composed of a blended distribution of an inorganic dielectric material, an organic polymer, and a single ion conductor polymer.

[0039] In some embodiments, the single-ion conductor polymer includes at least one of polyacrylonitrile-lithium salt (PAN-LiX), polyethylene oxide-lithium salt (PEO-LiX), polyvinylidene fluoride-hexafluoropropylene-lithium salt (PVDF-HEP-LiX), lithium polystyrene sulfonate (LiPSS), and lithium polyacrylate (LiPAA). When the dielectric response layer also contains a single-ion conductor polymer, the single-ion conductor polymer has a high lithium ion transference number, which can increase the lithium ion transference number of the dielectric response layer, further uniformize the negative electrode ion flux, enable the dielectric response layer to better inhibit lithium precipitation, and further improve the cycle performance of the battery.

[0040] In some embodiments, the single ion conductor polymer includes at least one of polyacrylonitrile-lithium (4-styrenesulfonyl) (trifluoromethylsulfonyl) imide (PAN-LiSTFSI) or polyethylene oxide-lithium 1-(3-(methacryloyloxy)propylsulfonyl)-1-(trifluoromethylsulfonyl) imide (PEO-LiMTFSI).

[0041] In some embodiments, based on the mass of the dielectric response layer, the mass percentage of the single-ion conductor polymer is 10% to 70%, specifically, it can be 10%, 20%, 30%, 40%, 50%, 60%, 70%, or a range consisting of any two of these values. By setting the content of the single-ion conductor within the above range, the dielectric response layer in the battery has a better effect of inhibiting lithium precipitation, which can further improve the cycle performance of the battery. The content of the single-ion conductor polymer in the dielectric response layer can be measured by combining TGA and ICP-MS to obtain the content of inorganic dielectric materials, organic matter and lithium elements in the dielectric response layer, and the lithium element content is used to convert the mass percentage of the single-ion conductor polymer.

[0042] In some embodiments, in the dielectric response layer, the mass ratio of the inorganic dielectric material to the single ion conductor polymer is 1:(0.1-0.7), which can be specifically 1:0.1, 1:0.2, 1:0.3, 1:0.4, 1:0.5, 1:0.6, 1:0.7, or a range consisting of any two of these values.

[0043] When the mass ratio of the inorganic dielectric material to the single-ion conductor polymer is within the above range, the dielectric response layer can have a better effect of inhibiting lithium precipitation, further improving the cycle stability of the battery.

[0044] The dielectric response layer can be provided on the surface of the negative electrode current collector or the surface of the lithium metal in a conventional manner. For example, the dielectric response layer can be provided on the surface of the current collector or the surface of the lithium metal by coating, pressing or rolling. For example, the following steps may be specifically included: dispersing the inorganic dielectric material and the organic polymer in an organic solvent to obtain a mixture; then coating the mixture on the current collector or the lithium metal sheet by coating, drying, and obtaining the dielectric response layer. In some embodiments, the organic solvent includes at least one of dimethylacetamide (DMAc), N-methylpyrrolidone (NMP) or acetonitrile (ACN). In some embodiments, in the mixture, the total mass percentage of the inorganic dielectric material and the organic polymer is 2% to 20%.

[0045] When the dielectric response layer includes a single-ion conductor polymer, the preparation method of the dielectric response layer includes the following steps: dispersing an inorganic dielectric material and an organic polymer in an organic solvent to obtain a mixture; then coating the mixture on a current collector or a metal lithium sheet by coating, and drying to obtain a composite layer of the inorganic dielectric material and the organic polymer; then coating a single-ion conductor precursor solution on the surface of the composite layer of the inorganic dielectric material and the organic polymer, performing a polymerization reaction to form a single-ion conductor polymer layer, and obtaining the dielectric response layer.

[0046] In some embodiments, the single ion conductor precursor solution includes an organic lithium salt, a monomer, and an initiator, wherein the initiator includes a photoinitiator and a thermal initiator.

[0047] In some embodiments, the raw materials of the single ion conductor polymer include an organic lithium salt, a monomer, and a modifier.

[0048] In some embodiments, the photoinitiator includes the photoinitiator 1-hydroxycyclohexylphenyl ketone.

[0049] In some embodiments, the organic lithium salt includes at least one of lithium bis(trifluoromethanesulfonyl)imide, lithium difluoroborate malonate, lithium sulfonate, lithium methyltrifluoromethanesulfonyl imide, or lithium trifluoromethanesulfonate.

[0050] In some embodiments, the monomer comprises a polymer monomer comprising at least one of polyethylene glycol diacrylate (PEGDA), polycarbonate (PC), polyethylene oxide (PEO), polyvinylidene fluoride-hexafluoropropylene (PVDF-HEP), lithium polystyrene sulfonate (PSS), or polyacrylic acid (PAA).

[0051] More specifically, the dielectric response layer includes the following preparation method:

[0052] S1. Mix (CO)2Cl2, DMF and acetonitrile evenly;

[0053] S2. Subsequently, 4-vinylbenzenesulfonate was added under an inert gas atmosphere, and the mixture was stirred at room temperature for 12 to 48 hours to obtain solution A;

[0054] S3, dissolving triethylamine, 4-dimethylaminopyridine and trifluoromethanesulfonamide in acetonitrile, and stirring at room temperature for 0.5 h to 3 h to obtain solution B;

[0055] S4. In an ice bath, gradually add the B solution dropwise to the A solution while stirring. After the addition is complete, stir at room temperature for 4 to 24 hours; then remove the solvent by rotary evaporation to obtain a solid intermediate;

[0056] S5, dissolving the solid intermediate in dichloromethane, washing with an aqueous solution of NaHCO3, an aqueous solution of HCl, and an aqueous solution of K2CO3 in sequence, and then drying to obtain KSTFSI;

[0057] S6, dissolving the KSTFSI in acetonitrile to obtain a KSTFSI solution; dissolving LiClO4 in acetonitrile to obtain a LiClO4 solution; adding the LiClO4 solution to the KSTFSI solution, the entire process is carried out under an argon environment, and stirring at room temperature for 4h to 24h; filtering, removing the solvent, recrystallizing and drying to obtain LiSTFSI;

[0058] S7, mixing the LiSTFSI, PEGDA, PC and photoinitiator in a glove box to obtain a precursor solution;

[0059] S7. Dispersing an inorganic dielectric material and an organic polymer in an organic solvent to obtain a mixture; then coating the mixture on a current collector or a metal lithium sheet, and drying to obtain a composite layer of the inorganic dielectric material and the organic polymer; then coating the precursor solution on the surface of the composite layer of the inorganic dielectric material and the organic polymer, and performing a polymerization reaction under ultraviolet light to form a single ion conductor polymer layer to obtain a dielectric response layer.

[0060] In some embodiments, the molar ratio of (CO)2Cl2 and DMF is (20-30):1, the volume ratio of (CO)2Cl2 and acetonitrile is 1:(15-30); the molar ratio of (CO)2Cl2, 4-vinylbenzenesulfonate, triethylamine, 4-dimethylaminopyridine and trifluoromethanesulfonamide is (40-50):(35-40):(100-120):(40-50):(35-40); the LiClO4 solution and The volume of the KSTFSI solution is 1:(2-10), the concentration of LiClO4 in the LiClO4 solution is 0.1-1 mol / L, and the concentration of KSTFSI in the KSTFSI solution is 0.01-0.8 mol / L; the mass ratio of the LiSTFSI, PEGDA, PC and photoinitiator is LiSTFSI:PEGDA:PC:photoinitiator = (0.1-0.5):1:(1-5):(0.001-1).

[0061] For another example, the preparation method of the dielectric response layer includes the following steps: dispersing raw materials of an inorganic dielectric material, an organic polymer and a single-ion conductor polymer in an organic solvent to obtain a mixture; then coating the mixture on a current collector or a metal lithium sheet by coating, and drying to obtain a dielectric response layer.

[0062] More specifically, the method for preparing the dielectric response layer comprises the following steps:

[0063] S1. Synthesis of polymer particles NPS: Using a three-necked flask equipped with a condenser reflux and a nitrogen inlet, add water to the three-necked flask, heat to 70-90°C, and purge with nitrogen to remove oxygen;

[0064] S2. Three feeds are added simultaneously, labeled as feed 1, feed 2, and feed 3, wherein feed 1 contains LiMTFSI, a reducing agent, and water; feed 2 contains methyl methacrylate and a cross-linking agent; and feed 3 contains an oxidizing agent and water. The entire feeding process lasts for 1 to 5 hours, and the reaction is continued under a nitrogen environment for 0.5 to 5 hours. The polymer nanoparticles (NPS) are then obtained by filtration and dialysis.

[0065] S3. BaTiO3 and PAN are dissolved in DMAc to obtain a mixture A; the NPS, PEO, LiTFSI and DMAc are mixed to obtain a mixture B; the mixture A and the mixture B are mixed to obtain a mixture; and the mixture is coated on a current collector or a metal lithium sheet by coating, and dried to obtain a dielectric response layer.

[0066] In some embodiments, in step S1, the weight portion of water is 10-200 parts; in step S2, the total weight portions of feed 1, feed 2 and feed 3 are 5-20 parts, 8-15 parts and 8-12 parts respectively, and the mass ratio of LiMTFSI, methyl methacrylate, cross-linking agent, reducing agent, oxidizing agent and water is (0.5-1.5): (5-15): (0.05-0.5): (0.05-0.5): (0.05-0.5): (1 0-30), the cross-linking agent includes ethylene glycol dimethacrylate, the reducing agent includes ascorbic acid, and the oxidizing agent includes tert-butyl hydroperoxide; in step S3, the mass ratio of the NPS, PEO and LiTFSI is (9-12): (60-70): (20-30), the total mass of the NPS, PEO and LiTFSI accounts for 2% to 8% of the mass of the mixture B, and the mass ratio of the mixture A to the mixture B is (8-10): 1.

[0067] In some embodiments, when the dielectric response layer is disposed on the surface of the current collector, the dielectric response layer is close to the negative electrode plate.

[0068] In some embodiments, the secondary battery further comprises an electrolyte, wherein the electrolyte comprises an organic solvent, a lithium salt, and an additive. The present application does not impose any specific restrictions on the types of the organic solvent and the lithium salt, and they can be selected according to actual needs.

[0069] In some embodiments, the organic solvent may be at least one of 1,3-dioxolane (DOL), dimethyl ether (DME), ethylene carbonate (EC), fluoroethylene carbonate (FEC), methyl formate (MF), methyl acetate (MA), ethyl acetate (EA), propylene carbonate (PC), ethyl methyl carbonate (EMC), diethyl carbonate (DEC), dimethyl carbonate (DMC), dipropyl carbonate (DPC), methyl propyl carbonate (MPC), ethyl propyl carbonate (EPC), butylene carbonate (BC), propyl acetate (PA), methyl propionate (MP), ethyl propionate (EP), propyl propionate (PP), methyl butyrate (MB), ethyl butyrate (EB), 1,4-butyrolactone (GBL), sulfolane (SF), dimethyl sulfone (MSM) or diethyl sulfone (ESE).

[0070] In some embodiments, the lithium salt can be at least one of lithium hexafluorophosphate (LiPF6), lithium bisfluorosulfonyl imide (LiFSI), lithium tetrafluoroborate (LiBF4), lithium perchlorate (LiClO4), lithium hexafluoroarsenate (LiAsF6), lithium bistrifluoromethanesulfonyl imide (LiTFSI), lithium difluorophosphate (LiPO2F2), lithium difluorobisoxalatophosphate (LiDFOP), lithium tetrafluorooxalatophosphate (LiTFOP), lithium trifluoromethanesulfonate (LiTFS), lithium difluorooxalatoborate (LiDFOB), or lithium dioxalatoborate (LiBOB).

[0071] In some embodiments, the secondary battery further includes a positive electrode sheet, and the positive electrode sheet includes a positive electrode active material layer.

[0072] In some embodiments, the positive electrode active material layer includes a positive electrode active material, and the positive electrode active material includes at least one of lithium cobalt oxide, lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminum oxide, lithium iron phosphate, lithium-rich manganese-based material, lithium manganese oxide, lithium iron manganese phosphate, lithium vanadium phosphate, lithium cobalt phosphate, lithium manganese phosphate, lithium iron silicate, lithium vanadium silicate, lithium cobalt silicate or lithium manganese silicate.

[0073] In some embodiments, based on the total mass of the positive electrode sheet, the mass percentage of the positive electrode active material is 50%-99%.

[0074] In some embodiments, the positive electrode sheet further includes a binder and a conductive agent.

[0075] In some embodiments, the adhesive includes at least one of styrene-butadiene rubber (SBR), water-based acrylic resin, carboxymethyl cellulose (CMC), polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), polyvinyl butyral (PVB), ethylene-vinyl acetate copolymer (EVA) or polyvinyl alcohol (PVA), but is not limited to the above types, and the adhesive can be selected according to actual needs.

[0076] In some embodiments, based on the total mass of the positive electrode sheet, the mass percentage of the binder is less than or equal to 5%.

[0077] In some embodiments, the conductive agent includes at least one of graphite, acetylene black, carbon black, Ketjen black, carbon nanotubes, graphene, or carbon nanofibers, but is not limited to the above. The conductive agent can be selected according to actual needs.

[0078] In some embodiments, the conductive agent has a mass percentage of 1% to 3% based on the total mass of the positive electrode sheet.

[0079] Positive electrode sheets can be prepared using conventional methods in the art. For example, the preparation method includes the following steps: mixing a solvent, a conductive agent, a binder, and a positive electrode active material to obtain a positive electrode slurry; coating the positive electrode slurry on the surface of a current collector, drying, and cold pressing to obtain a positive electrode sheet.

[0080] In some embodiments, the solvent may include N-methylpyrrolidone (NMP), but is not limited thereto.

[0081] In some embodiments, the secondary battery includes a separator, the material of which may include, but is not limited to, at least one of polyethylene (PE), polypropylene (PP)-based polyolefins (PO), polyesters (such as polyethylene terephthalate (PET) film), cellulose, polyimide (PI), polyamide (PA), spandex, or aramid. The separator may be a woven membrane, a nonwoven membrane, a microporous membrane, a composite membrane, a rolled membrane, or a spun membrane.

[0082] In some embodiments, the separator may have a thickness of 5 μm to 500 μm.

[0083] The secondary battery of the present application can be prepared according to conventional methods in the field; for example, the preparation method may specifically include the following steps: a structure containing a positive electrode sheet, a separator and a negative electrode sheet is stacked and wound to obtain an electrode assembly; the electrode assembly is placed in a packaging shell, an electrolyte is injected and the shell is sealed to obtain a secondary battery.

[0084] In a second aspect, the present application provides an electronic device comprising the aforementioned secondary battery. The electronic device of the present application can be used in various fields, including electronic products, energy storage, power batteries, and electric vehicles, such as mobile phones, laptops, power tools, video recorders, backup power supplies, electric vehicles, electric motorcycles, game consoles, cameras, and drones. It is particularly suitable for electronic devices requiring fast charging, greatly facilitating people's lives.

[0085] In order to better illustrate the purpose, technical solutions and advantages of this application, this application will be further described below through specific comparative examples and embodiments.

[0086] Ingredients Description:

[0087] 1. Inorganic dielectric materials

[0088] Barium titanate powder (BTO-1): average particle size 0.05 μm;

[0089] Barium titanate powder (BTO-2): average particle size 0.5 μm;

[0090] Barium titanate powder (BTO-3): average particle size 5 μm.

[0091] Lithium-doped barium titanate: represented by 0.03Li-0.97BaTiO3 (Li molar percentage is 3%), with an average particle size of 0.1 μm; its synthesis method comprises the following steps: S1, first dissolving 40 mmol of tetraisopropoxytitanium (Ti(i-PrO)4) in 30 mL of isopropanol, and then adding 40 mmol of Ba(OH)2·8H2O, 0.62 mmol of Li2CO3 and 17 mL of ammonia solution (concentration is 6.5 M) to obtain a mixture;

[0092] S2. Add the mixture into an autoclave lined with polytetrafluoroethylene, seal it, heat it to 200°C, and react at this temperature for 12 hours;

[0093] S3. After the reaction is completed, the autoclave is taken out and cooled to room temperature. The solution is removed using a rotary evaporator, and then the precipitate is calcined at 600° C. for 1 hour to obtain lithium-doped barium titanate, which is recorded as 0.03Li-0.97BaTiO3.

[0094] Doped barium titanate-based dielectric materials: Li-doped-Ba 0.85 Ca 0.15 Ti 0.9 Zr 0.1 O3 (Li content: 0.05wt%), average particle size 10μm; the synthesis method comprises the following steps:

[0095] S1, according to Ba 0.85 Ca 0.15 Ti 0.9 Zr 0.1 The raw materials were weighed in the stoichiometric ratio of O3, and then BaCO3, TiO2, CaCO3 and ZrO2 powders were ball-milled in anhydrous ethanol for 6 h;

[0096] S2. The ball-milled mixed powder was calcined at 1200°C for 2 hours. After calcination, 0.3 wt% of Li2CO3 powder was added, and the mixture was ball-milled again for 6 hours, and then dried.

[0097] S3. After drying, calcining in an air atmosphere at 1475° C. for 2 hours to obtain a doped barium titanate-based dielectric material.

[0098] 2. Basement membrane

[0099] Polyacrylonitrile (PAN, molecular weight: 50,000-300,000 g / mol), polyvinylidene fluoride (PVDF, molecular weight: 100,000-700,000 g / mol), polyethylene oxide (PEO, molecular weight: 100,000-5,000,000 g / mol), polyvinylidene fluoride-co-hexafluoropropylene (PVDF-HFP, molecular weight: 100,000-800,000 g / mol), polylactic acid (PLA, molecular weight: 50,000-200,000 g / mol), polyurea (PU, molecular weight: 20,000-500,000 g / mol).

[0100] 3. Single ion conductor polymer

[0101] Polyacrylonitrile-lithium (4-styrenesulfonyl) (trifluoromethanesulfonyl) imide (PAN-LiSTFSI) is synthesized by irradiating its precursor solution under 365nm ultraviolet light for 10 minutes. The synthesis method of the precursor solution comprises the following steps:

[0102] S1, (CO) 2 Cl 2 (46.6 mmol, 4 mL) and DMF (2 mmol, 9 μL) were dissolved in 80 mL of dry acetonitrile and stirred at room temperature for 5 hours;

[0103] S2. Subsequently, 4-vinylbenzenesulfonate (38.8 mmol, 8 g) was added under an inert gas atmosphere, and the above mixture was stirred at room temperature for 24 h, which was recorded as solution A;

[0104] S3. Dissolve triethylamine (TEA, 116.2 mmol, 16.2 mL), 4-dimethylaminopyridine (DMAP, 48.1 mmol, 5.4 g), and trifluoromethanesulfonamide (38.8 mmol, 5.78 g) in 60 mL of dry acetonitrile and stir at room temperature for 1 hour to form a colorless solution, which is recorded as solution B.

[0105] S4. Gradually add solution B dropwise to solution A while maintaining an ice bath and stirring vigorously. Then, stir at room temperature for 16 hours.

[0106] S5. The solvent was then removed by rotary evaporation, and the resulting solid was dissolved in 100 mL of dichloromethane, washed three times with 40 mL of a 4 wt% aqueous NaHCO solution, and then washed with 40 mL of a 3 wt% aqueous HCl solution. The acidic monomer was then neutralized with an excess of a 0.5 mol / L aqueous KCO solution, and the final product was dried in a vacuum drying oven at 60 ° C for 24 h to obtain the intermediate product KSTFSI.

[0107] S6. Preparation of LiSTFSI from KSTFSI: KSTFSI powder (8.5 mmol, 3 g) was added to 100 mL of dry acetonitrile and stirred under argon protection until the powder was completely dissolved; LiClO4 (8.5 mmol, 0.91 g) was then dissolved in 20 mL of dry acetonitrile; the LiClO4 solution was added to the KSTFSI solution using a syringe; the entire process was carried out under argon environment and stirred at room temperature for 12 hours; the white KClO4 precipitate generated by the reaction was filtered out, the solvent was removed by rotary evaporation, the obtained white solid was recrystallized in deionized water, and then dried in a vacuum oven at 60°C for 10 hours to obtain white LiSTFSI powder.

[0108] S7. LiSTFSI, PEGDA, PC and photoinitiator HPK (1-hydroxycyclohexylphenyl ketone, 0.2 wt%) were mixed in a glove box to prepare a precursor solution, wherein the mass ratio of LiSTFSI, PEGDA and PC was LiSTFSI:PEGDA:PC=0.3:1:3.25.

[0109] Polyethylene oxide-lithium 1-(3-(methacryloyloxy)propylsulfonyl)-1-(trifluoromethylsulfonyl)imide (PEO-LiMTFSI) is prepared from polymer particles (NPS), PEO (average molecular weight 900,000 g / mol), and LiTFSI, including the following preparation steps:

[0110] S1. Synthesis of polymer particles NPS: Using a three-necked flask equipped with a condenser reflux and a nitrogen inlet, add 70 g of high-purity water to the flask, preheat to 80°C, and purge with nitrogen for 20 minutes to remove oxygen;

[0111] S2. Three feeds were added simultaneously: feed 1: containing the functional comonomer LiMTFSI (lithium 1-(3-(methacryloyloxy)propylsulfonyl)-1-(trifluoromethylsulfonyl)imide, 1 g), ascorbic acid (reducing agent, 0.228 g) and water (10 g); feed 2: containing the main monomer methyl methacrylate (MMA, 9.196 g) and the crosslinking agent ethylene glycol dimethacrylate (EGDMA, 0.184 g); feed 3: containing tert-butyl hydroperoxide (TBHP, oxidizing agent, 0.116 g) and water (10 g); the entire feeding process lasted for 3 hours, and the reaction was continued under nitrogen for 1 hour;

[0112] S3, the obtained polymer nanoparticle NPS dispersion is filtered through an 80 μm nylon mesh to remove agglomerated nanoparticles, and the emulsion is purified by dialysis to remove unreacted ionic substances to obtain polymer nanoparticles NPS;

[0113] S4. Mixing polymer nanoparticles NPS, PEO, and LiTFSI in DMAc to obtain a mixture B, wherein the mass ratio of polymer nanoparticles NPS, PEO, and LiTFSI is 10:67.5:22.5, and the total mass of polymer nanoparticles NPS, PEO, and LiTFSI accounts for 5% of the mass of mixture B.

[0114] Example 1

[0115] (1) Negative electrode: BaTiO3 (BTO-1, 0.05 μm) powder and PAN were dissolved in DMAc and stirred at room temperature for 24 h to obtain a mixture in which the mass ratio of BTO-1 to PAN was 1:2 and the mass proportion of PAN and BTO-1 in the mixture was 5%; the mixture was then scraped onto the surface of a 100 μm lithium metal foil on one side, dried, and the solvent was removed to obtain a composite layer containing PAN and BaTiO3 on one surface of the lithium metal foil. A single ion conductor (PAN-LiSTFSI) precursor solution is then coated on the surface of the composite layer. The precursor solution includes LiSTFSI, PEGDA, PC (polycarbonate) and photoinitiator HPK (1-hydroxycyclohexylphenyl ketone). Subsequently, the composite layer is irradiated with 365nm ultraviolet light for 10 minutes to form a single ion conductor polymer layer on the composite layer. The composite layer is dried under inert gas and the tabs are welded to obtain a negative electrode sheet containing a dielectric response layer on one side of the lithium metal foil. The thickness of the dielectric response layer is 5μm, and the mass of the single ion conductor polymer layer accounts for 10% of the mass of the dielectric response layer. The other relevant parameters of the dielectric response layer are shown in Table 1.

[0116] (2) The positive electrode active material lithium iron phosphate, acetylene black conductive agent, and polyvinylidene fluoride binder are mixed in a weight ratio of 96:2:2, and an appropriate amount of N-methylpyrrolidone (NMP) solvent is added. Then, the mixture is stirred evenly under the action of a vacuum mixer to obtain a positive electrode slurry with a solid content of 70wt%. Artificial graphite, styrene-butadiene rubber, and sodium carboxymethyl cellulose are mixed with deionized water in a mass ratio of 96:2:2, stirred evenly, and formulated into a negative electrode slurry with a solid content of 45wt%. The positive electrode slurry is evenly coated on one side of the aluminum foil with a single-sided coating thickness of 40μm. After drying, the above steps are repeated on the other side of the aluminum foil. After welding the tabs, a double-sided coated positive electrode sheet is obtained.

[0117] (3) In a dry argon atmosphere glove box, 1,3-dioxolane (DOL) and dimethyl ether (DME) were mixed in a mass ratio of 1:1 to obtain a base solvent. A fluorinated lithium salt, LiTFSI, was then added to the base solvent, dissolved, and mixed uniformly to obtain an electrolyte. The mass percentage of the fluorinated lithium salt, LiTFSI, was 40% based on the mass of the electrolyte, with the remainder being the base solvent.

[0118] (4) stacking the positive electrode sheet, the separator (PE), and the negative electrode sheet in order, wherein the separator is placed between the positive electrode sheet and the negative electrode sheet to play an isolating role, and the dielectric response layer of the negative electrode sheet is close to the separator, and then winding to obtain an electrode assembly;

[0119] (5) The electrode assembly is placed in an outer packaging aluminum-plastic film, the electrolyte is injected, and the battery is packaged. After the formation, degassing, and trimming processes, a lithium-ion battery is obtained.

[0120] Example 2

[0121] Compared with Example 1, in step (1), the mass ratio of BTO-1 and PAN was changed, and the single ion conductor polymer layer was not prepared on the composite layer containing PAN and BaTiO3. The composite layer of PAN and BaTiO3 was used as the dielectric response layer, as shown in Table 1. The rest was the same.

[0122] Example 3

[0123] Compared with Example 1, in step (1), the mass ratio of BTO-1 and PAN was changed, as shown in Table 1, and the rest were the same.

[0124] Example 4

[0125] Compared with Example 1, in step (1), 0.03Li-0.97BaTiO3 is used in equal amounts to replace BTO-1, as shown in Table 1, and the rest are the same.

[0126] Example 5

[0127] Compared with Example 1, in step (1), Li-doped-Ba 0.85 Ca 0.15 Ti 0.9 Zr 0.1 O3 replaces BTO-1 in equal amounts, as shown in Table 1, and the rest are the same.

[0128] Example 6

[0129] Compared with Example 1, in step (1), BTO-2 (average particle size 0.5 μm) was used in equal amounts to replace BTO-1, as shown in Table 1, and the rest was the same.

[0130] Example 7

[0131] Compared with Example 1, in step (1), BTO-3 (average particle size 5 μm) was used in equal amounts to replace BTO-1, as shown in Table 1, and the rest was the same.

[0132] Example 8

[0133] Compared with Example 1, in step (1), BaTiO3 (BTO-1, 0.05 μm) powder and PVDF were dissolved in NMP and stirred at room temperature for 24 h to obtain a mixture, as shown in Table 1. The rest was the same.

[0134] Example 9

[0135] Compared with Example 1, in step (1), BaTiO3 (BTO-1, 0.05 μm) powder and PEO were dissolved in ACN and stirred at room temperature for 24 h to obtain a mixture, as shown in Table 1. The rest was the same.

[0136] Example 10

[0137] Compared with Example 1, in step (1), BaTiO3 (BTO-1, 0.05 μm) powder and PVDF-HFP were dissolved in NMP and stirred at room temperature for 24 h to obtain a mixture, as shown in Table 1. The rest was the same.

[0138] Example 11

[0139] Compared with Example 1, this embodiment uses PEO-LiMTFSI single ion conductor polymer, and the specific preparation process is as follows:

[0140] (1) Negative electrode:

[0141] BaTiO3 (BTO-1, 0.05 μm) powder and PAN were dissolved in DMAc and stirred at room temperature for 24 h to obtain a mixture A, wherein the mass ratio of BTO-1 to PAN was 1:2, and the mass proportion of PAN and BTO-1 in the mixture A was 5%.

[0142] The polymer nanoparticles NPS, PEO, and LiTFSI were mixed in DMAc to obtain a mixture B, wherein the mass ratio of the polymer nanoparticles NPS, PEO, and LiTFSI was 10:67.5:22.5, and the total mass of the polymer nanoparticles NPS, PEO, and LiTFSI accounted for 5% of the mass of the mixture B.

[0143] Mixture A and mixture B were mixed evenly, and the mass ratio of mixture A to mixture B was 9:1. The mixture was then scraped onto the surface of a 100 μm lithium metal foil on one side. After drying and removing the solvent, the tabs were welded to obtain a negative electrode sheet containing a dielectric response layer on one side of the lithium metal foil. The thickness of the dielectric response layer was 5 μm. The other relevant parameters of the dielectric response layer are detailed in Table 1.

[0144] (2)-(5): Same as Example 1.

[0145] Examples 12-14

[0146] Compared with Example 1, in step (1), the mass proportions of PAN and PAN-LiSTFSI in the dielectric response layer are changed, as shown in Table 1, and the rest are the same.

[0147] Examples 15-16

[0148] Compared with Example 1, in step (1), the thickness of the dielectric response layer is changed, as shown in Table 1, and the rest is the same.

[0149] Example 17

[0150] Compared with Example 10, the mass ratio of BTO-1 and PVDF-HFP was changed as shown in Table 1, and the rest were the same.

[0151] Comparative Example 1

[0152] The negative electrode sheet of this comparative example does not have a dielectric response layer, and the specific preparation process is as follows:

[0153] (1) Lithium metal foil is used as the negative electrode.

[0154] (2) The positive electrode active material lithium iron phosphate, acetylene black conductive agent, and polyvinylidene fluoride binder are mixed in a weight ratio of 96:2:2, and an appropriate amount of N-methylpyrrolidone (NMP) solvent is added. Then, the mixture is stirred evenly under the action of a vacuum mixer to obtain a positive electrode slurry with a solid content of 70wt%. Artificial graphite, styrene-butadiene rubber, and sodium carboxymethyl cellulose are mixed with deionized water in a mass ratio of 96:2:2, stirred evenly, and formulated into a negative electrode slurry with a solid content of 45wt%. The positive electrode slurry is evenly coated on one side of the aluminum foil with a single-sided coating thickness of 40μm. After drying, the above steps are repeated on the other side of the aluminum foil. After welding the tabs, a double-sided coated positive electrode sheet is obtained.

[0155] (3) In a dry argon atmosphere glove box, 1,3-dioxolane (DOL) and dimethyl ether (DME) were mixed in a mass ratio of 1:1 to obtain a base solvent. A fluorinated lithium salt, LiTFSI, was then added to the base solvent, dissolved, and mixed uniformly to obtain an electrolyte. The mass percentage of the fluorinated lithium salt, LiTFSI, was 40% based on the mass of the electrolyte, with the remainder being the base solvent.

[0156] (4) Stacking the positive electrode sheet, separator (PE), and negative electrode sheet in order, placing the separator between the positive electrode sheet and the negative electrode sheet to play a role of isolation, and then winding to obtain an electrode assembly;

[0157] (5) The electrode assembly is placed in an outer packaging aluminum-plastic film, the electrolyte is injected, and the battery is packaged. After the formation, degassing, and trimming processes, a lithium-ion battery is obtained.

[0158] Performance testing:

[0159] (1) Relative dielectric constant of dielectric response layer: The relative dielectric constant of dielectric response layer was calculated by using Keysight E4990A impedance analyzer from 20 Hz to 10 MHz, with the 100 Hz measurement value selected.

[0160] (2) Lithium-ion battery cycle performance test: The lithium-ion battery was placed in a 25°C constant temperature box, charged at a constant current rate of 0.2C to 3.7V, then charged at a constant voltage of 3.7 to a current of 0.05C, and then discharged at a constant current rate of 0.2C to 2.5V. This is one charge and discharge cycle. The lithium-ion battery was charged and discharged 100 times according to the above method, and the discharge capacity of the lithium-ion battery in the first cycle and the discharge capacity of the 100th cycle were recorded. The cycle capacity retention rate = discharge capacity of the 100th cycle / discharge capacity of the first cycle × 100%.

[0161] (3) Cycling performance of lithium-ion batteries under high-rate charging (fast charging mode): Place the lithium-ion battery in a 25°C constant temperature box, charge it to 3.7V at a constant current rate of 2C, then charge it at a constant voltage of 3.7V to a current of 0.05C, and then discharge it to 2.5V at a constant current rate of 0.5C. This is one charge and discharge cycle. The lithium-ion battery is charged and discharged 100 times according to the above method, and the discharge capacity of the first cycle and the discharge capacity of the 100th cycle of the lithium-ion battery are recorded. The cycle capacity retention rate = discharge capacity of the 100th cycle / discharge capacity of the first cycle × 100%

[0162] The test results of the relative dielectric constant of the dielectric response layer and the cycle capacity retention rate of the lithium-ion battery are shown in Table 1.

[0163] Table 1

[0164]

[0165]

[0166] It can be seen from the above Examples 1-17 and Comparative Example 1 that adding a dielectric response layer to the negative electrode sheet can inhibit lithium plating at the negative electrode. During the charge and discharge process, the negative electrode lithium metal surface is in an electric field. Due to the presence of dielectric polarization, the dielectric response layer will generate a built-in electric field in the response layer. The built-in electric field can change the surrounding electric field and affect the surrounding charge distribution, thereby playing a role in uniform ion flux and reducing local charge accumulation to present a high tip voltage. It can inhibit lithium plating at the negative electrode, delay the generation of lithium dendrites, improve kinetic performance, and significantly improve the cycle performance of the battery, so that the battery capacity remains above 78% after 100 cycles. At the same time, by changing the type and content of the inorganic dielectric material, organic polymer and single ion conductor polymer, the relative dielectric constant of the dielectric response layer, the strength of the built-in electric field and the degree of uniform ion flux are different, thereby affecting its effect of inhibiting lithium plating, and the battery can obtain better cycle performance.

[0167] In addition, it can be seen from Examples 1, 2, 11 and 12 that when the dielectric response layer contains a single-ion conductor polymer, the inorganic dielectric material in the dielectric response layer can perform electric field regulation, homogenize the electric field distribution on the electrode surface, and reduce the local current density; and the single-ion conductor polymer, with its high lithium ion migration number, ensures rapid and uniform transmission of lithium ions, significantly reduces concentration polarization, and can improve the charge and discharge efficiency at high rates. Under the synergistic effect of the two, it is more conducive to inhibiting the formation of lithium dendrites, especially dendrite formation at high rates, thereby achieving the purpose of significantly improving the cycle life of the battery in the fast charging mode.

[0168] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present application and are not intended to limit the scope of protection of the present application. Although the present application has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solutions of the present application may be modified or replaced by equivalents without departing from the essence and scope of the technical solutions of the present application.

Claims

1. A secondary battery comprising a negative electrode plate, characterized in that: The negative electrode plate includes a current collector and a dielectric response layer, wherein the dielectric response layer is provided on at least one surface of the current collector. Or the negative electrode plate includes the current collector, lithium metal and the dielectric response layer, and the lithium metal is arranged between the current collector and the dielectric response layer; The relative dielectric constant of the dielectric response layer is 2 to 37; the dielectric response layer contains an inorganic dielectric material and an organic polymer; and the current collector includes any one of copper foil, titanium foil, stainless steel, carbon paper and graphene paper.

2. The secondary battery according to claim 1, wherein Based on the mass of the dielectric response layer, the mass percentage of the inorganic dielectric material is 0.5% to 50%.

3. The secondary battery according to claim 1, wherein The average particle size of the inorganic dielectric material is 0.01 μm to 20 μm.

4. The secondary battery according to claim 1, wherein The inorganic dielectric material includes at least one of barium titanate or metal element-doped barium titanate; in the metal element-doped barium titanate, the doped metal element includes at least one of Li, Sr, Ca, Zr, Sn, La, Nd or Sm.

5. The secondary battery according to any one of claims 1 to 4, wherein The dielectric response layer has a thickness of 1 μm to 30 μm.

6. The secondary battery according to any one of claims 1 to 4, wherein The organic polymer includes at least one of polyacrylonitrile, polyvinylidene fluoride, polyethylene oxide, polyvinylidene fluoride-co-hexafluoropropylene, polylactic acid or polyurea.

7. The secondary battery according to any one of claims 1 to 4, wherein The dielectric response layer further contains a single ion conductor polymer, which includes at least one of polyacrylonitrile-lithium salt, polyethylene oxide-lithium salt or polyvinylidene fluoride-co-hexafluoropropylene-lithium salt.

8. The secondary battery according to claim 7, wherein Based on the mass of the dielectric response layer, the mass percentage of the single ion conductor polymer is 10% to 70%.

9. The secondary battery according to claim 7, wherein In the dielectric response layer, the mass ratio of the inorganic dielectric material to the single ion conductor polymer is 1:(0.1-0.7).

10. An electronic device, characterized in that: A secondary battery comprising the secondary battery according to any one of claims 1 to 9.

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