Electrochemical device comprising a positive electrode plate and electrical device

Abstract

An electrochemical device, namely a lithium-ion battery, comprising: a positive electrode plate having a positive electrode current collector and a positive electrode active material layer provided on at least one surface of the positive electrode current collector, wherein the positive electrode current collector comprises stainless steel, aluminum, nickel, titanium, burned carbon, or aluminum; a negative electrode plate having a negative electrode current collector and a negative electrode active material layer provided on at least one surface of the negative electrode current collector, wherein the negative electrode active material layer comprises a negative electrode active material, and wherein the negative electrode current collector comprises copper, stainless steel, aluminum, nickel, titanium, burned carbon, or an aluminum-cadmium alloy;a separator between the positive electrode plate and the negative electrode plate, the separator comprising at least one of the following materials: polyethylene, polypropylene, polyvinylidene fluoride, aramid, polyethylene terephthalate, polytetrafluoroethylene, polyacrylonitrile, polyimide, polyamide, polyester, and natural fiber; characterized in that the positive electrode active material layer has a positive electrode active material comprising a ternary positive electrode active material; a particle size change rate of the positive electrode active material, a roughness of the positive electrode plate, and a porosity of the positive electrode plate satisfy the following relationship: 1.2≤D / (R / 5+P / 2)≤3.5;where D is the particle size change rate of DV50 in %, before and after the positive electrode active material is held at a pressure of 35 KN for 30 seconds, and DV50 is a particle size that corresponds to 50% of a cumulative volume distribution percentage of the positive electrode active material; R is the roughness of the positive electrode plate in nm; and P is the porosity of the positive electrode plate in %.

Description

BACKGROUNDTechnical FieldThe present invention relates to the field of electrochemical technology, and more particularly to a positive electrode plate, an electrochemical device including the positive electrode plate, and an electronic device.Description of the Prior ArtLithium ion batteries have advantages of high specific energy, light weight, long life and lack of memory. They are used in various civil electric appliances and electric vehicles, power storage, mobile power supply and other fields. With the wide range of applications of lithium ion batteries, the discharge performance of lithium ion batteries at low temperatures has been increasingly demanded.At low temperatures, the decrease in lithium ion transfer rate is the major cause of the decrease in discharge power of lithium ion batteries. The properties of the positive electrode active material, the negative electrode active material, the electrolyte solution, and the current collector may all cause a decrease in the transmission rate of lithium ions. The influence of the positive electrode active material is relatively more important. At low temperatures, the decrease in conductivity of the electrolyte solution results in a decrease in the transport rate of lithium ions in the positive electrode active material and a decrease in the discharge capacity of the lithium ion battery at low temperatures. In ternary positive electrode active materials with high nickel content, the conductivity of lithium ions decreases at low temperature and also leads to an increase in resistance, leading to a decrease in the discharge performance of the battery and more severe problems in rapid discharges.Therefore, it is of great importance to develop lithium ion batteries for low temperatures which can be used in severe cold or in North fields to extend the fields of application and the scope of lithium ion batteries.SUMMARYAn object of the present invention is to overcome the disadvantages of the prior art and to provide a positive electrode plate, an electrochemical device comprising the positive electrode plate, and an electrical device. The capacity retention rate at low temperatures and the performance of the electrochemical device at high discharge rates at low temperatures are to be improved significantly after the positive electrode plate is attached to the electrochemical device. The invention is defined by the features of the independent claims. Advantageous embodiments are the subject of the dependent claims.In order to achieve the above object, the present invention provides, in a first aspect of the present invention, a positive electrode plate including a positive electrode current collector and a positive electrode active material layer provided on at least one surface of the positive electrode current collector. The positive electrode active material layer includes a positive electrode active material, and the positive electrode active material includes a ternary positive electrode active material. A particle size change rate of the positive electrode active material, the roughness of the positive electrode plate, and a porosity of the positive electrode plate satisfy the following relationship: wherein D is the particle size change rate D V50 in % before and after the positive electrode active material is maintained at a pressure of 35 KN for 30 seconds, and D V50 is a particle size corresponding to 50% of a cumulative volume distribution percentage of the positive electrode active material. R is the roughness of the positive electrode plate in nm. P is the porosity of the positive electrode plate in %.In a preferred embodiment of the present invention, the particle size change rate of the positive electrode active material, the roughness of the positive electrode plate, and the porosity of the positive electrode plate satisfy the following relationship:In a preferred embodiment of the present invention, the particle size change rate (D) of the positive electrode active material is between 60% and 90%.In a preferred embodiment of the present invention, the particle size change rate (D) of the positive electrode active material is between 65% and 80%.In a further preferred embodiment of the present invention, the roughness (R) of the positive electrode plate is in the range from 80 nm to 200 nm.In a further preferred embodiment of the present invention, the roughness (R) of the positive electrode plate is in the range from 100 nm to 150 nm.In a preferred embodiment of the present invention, the porosity (P) of the positive electrode plate is in the range of 15% to 35%.In another preferred embodiment of the present invention, the porosity (P) of the positive electrode plate is in the range of 18% to 25%.In a preferred embodiment of the present invention, the particle size (D V50) of the positive electrode active material ranges from 3 μm to 8 μm.In a preferred embodiment of the present invention, the ternary positive electrode active material has the formula LiNi x Co y Mn (1-x-y) O 2, wherein 0.7≤x<1, 0<y≤0.3, and 0<x+y<1.In a second aspect, the invention provides an electrochemical device comprising the positive electrode plate as described above.In a third aspect, the present invention provides an electrical device comprising the electrochemical device as described above.The invention has the following advantageous effects.The present invention provides a positive electrode plate, an electrochemical device including the positive electrode plate, and an electrical device. By controlling the roughness of the positive electrode plate, the porosity of the positive electrode plate, and the particle size change rate of the positive electrode active material, the present invention can significantly improve the capacity retention rate at low temperatures and the discharge performance of the electrochemical device at high temperatures after the positive electrode plate is attached to the electrochemical device.DESCRIPTION OF THE EMBODIMENTSIn order to make the objects, technical solutions, and advantages of the embodiments of the invention clearer, the technical solutions in the embodiments of the invention will be described clearly and fully below. Of course, the examples described are only a part of the invention and not all examples. On the basis of the examples according to the invention, all other examples which the person skilled in the art receives without inventive complexity also fall within the scope of protection of the invention.The present invention includes, among the technical features disclosed herein, both a closed technical solution consisting of the above-mentioned features and an open technical solution including the above-mentioned features.In the present invention, reference is made to numerical ranges which, unless otherwise stated, are to be considered continuous and include both the minimum and maximum values of the range and any value between the minimum and maximum values. When a range refers to an integer, it also includes any integer between the minimum and maximum values of the range. When a plurality of regions are given for describing a feature or a property, the regions may also be combined. In other words, unless otherwise stated, all ranges disclosed herein also include all sub-ranges included therein.In the present invention, the specific methods for dispersing and stirring the treatment are not particularly limited.Unless the reagents or instruments used in the invention are specified by the manufacturer, they are commercially available products which are commercially available.Note that in the content of the present application, the present application is explained using a lithium ion secondary battery as an example of an electrochemical device, but the electrochemical device of the present application is not limited to the lithium ion secondary battery.Positive electrode plate or positive pole pieceAn example of the present invention provides a positive electrode plate including a positive electrode current collector and a positive electrode active material layer provided on at least one surface of the positive electrode current collector. The positive electrode active material layer includes a positive electrode active material, and the positive electrode active material includes a ternary positive electrode active material.The particle size change rate D of the positive electrode active material, the positive electrode plate roughness R, and the positive electrode plate porosity P satisfy the following relationship:In the above relationship, D is the particle size change rate of D V50 in % before and after the positive electrode active material is maintained at a pressure of 35 KN for 30 seconds. R is the roughness of the positive electrode plate in nm, and P is the porosity of the positive electrode plate in %.In the present invention, the particle size change rate (D) of the positive electrode active material is calculated from the change in the particle size (D V50) of the positive electrode active material before and after holding for 30 seconds at a pressure of 35 KN. In the present application, the positive electrode active material includes primary particles and / or secondary particles, wherein "primary particles" denotes a primary structure of individual particles, i.e., single-crystalline particles, and "secondary particles" denotes an aggregate in which primary particles are aggregated by physical or chemical bonding between primary particles, i.e., a secondary structure.The particle size change rate of the positive electrode active material is related to the particle strength of the positive electrode active material and the degree of the content of the secondary particles (which also corresponds to the degree of single crystallization). When the positive electrode active material is subjected to the pressure, the secondary particles of the positive electrode active material may be broken into a plurality of smaller particles, or deformation or breakage of the primary particles and / or the secondary particles may occur. In general, when the particle size change rate of the positive electrode active material is low, it means that the higher the strength of the representative particle, or the lower the proportion of the secondary particles, the higher the degree of single crystallization. The higher particle size change rate means a relatively low particle strength or a relatively high proportion of secondary particles.The particle size change rate of the positive electrode active material should be in an appropriate range. For the positive electrode active material, a higher particle size change rate tends to mean that there are more pores and voids within the positive electrode active material layer that may be formed by the rolling step during preparation of the positive electrode plate. The pores and cavities within the positive electrode active material layer may be microscopically small cracks, cavities or cavities within the positive electrode active material particles or gaps between the particles. By the presence of pores and voids, the diffusion path of ions inside the particles is shortened, the intercalation / deintercalation rate of ions is increased, and the discharge performance of the lithium ion battery at low temperatures is improved. Moreover, during charging and discharging of the lithium ion battery, the positive electrode active material undergoes volume expansion and contraction, and the higher particle size change rate can offer more space to accommodate the volume change, thereby reducing the risk of stress concentration and damage, and thus improving the electrochemical performance of the positive electrode plate after long-term cycles at low temperature.The particle size change rate of the positive electrode active material should not be too high. The positive electrode active material needs an appropriate particle thickness to ensure that the material has good structural strength and stability. At low temperatures, the material inside the battery tends to become brittle. A positive electrode active material having too high a particle size change rate may not provide sufficient mechanical support due to its low structural strength and stability, leading to structural damage to the positive electrode plate and thus degrading the electrochemical performance of the battery at low temperatures. In addition, in a low temperature environment, the diffusion rate of the ions slows down, resulting in a decrease in the electrochemical reaction rate of the battery. When the particle size change rate of the positive electrode active material is too high, the proportion of the secondary particles may be too large, resulting in a decrease in the density of the active material and impairing the charge and ion transport in the positive electrode plate, thereby decreasing the capacity of the battery at low temperature. The particle size change rate of the positive electrode active material should not be too low. Too low a particle size change rate is often related to the heterogeneity of the internal structure of the particles. Too strong a bond between the transition metal and the oxygen leads to an increase in the lithium ion transport potential. Too low a particle size change rate may mean that there are too few pores and voids within the positive electrode active material layer. Too long a diffusion path of the ions inside the particles is not conducive to the high discharge capacity of lithium-ion batteries at low temperatures. Moreover, when the particle size change rate is too low, the stress (lattice expansion / contraction) generated by the positive electrode plate upon repeated charging and discharging tends to concentrate locally, which is not conducive to long-term storage and use of the cell at low temperatures.The roughness of the positive electrode plate and the porosity of the positive electrode plate also have a great influence on the electrochemical performance of the battery at low temperatures.The roughness of the positive electrode plate influences the contact performance between the electrode and the electrolyte solution. In a low temperature environment, the electrochemical reaction rate is slow. An appropriate roughness means that the area of contact between the surface of the positive electrode active material layer in the positive electrode plate and the electrolyte solution is relatively larger, which facilitates the transport of ions in the positive electrode plate, promotes the low-temperature electrochemical reaction, and thus improves the capacity retention rate of the battery at low temperatures. The roughness of the positive electrode plate should not be too small, otherwise it is difficult to make a uniform and complete contact area between the active particles and the electrolyte solution to ensure the normal migration of the lithium ions. However, too high a roughness may result in excessive accumulation of the electrolyte solution on the surface of the positive electrode highly oxidizing active material and excessive side reactions of the electrolyte solution on the surface of the positive electrode active material, thereby decreasing the capacity retention rate of the battery. An excessively high roughness may also result in an uneven distribution of the electric field on the surface of the positive electrode plate, which exacerbates the phenomenon of electrode polarization. Particularly at low temperatures, the degree of electrode polarization generally increases, which affects the electrochemical performance of the battery. Moreover, the excessively high roughness may also mean that there are too many pores in the positive electrode plate, resulting in reduced electrical connection and increased resistance, which deteriorates the low temperature performance of the battery.The porosity of the positive electrode plate mainly affects the diffusion space of the electrolyte solution and the area of contact with the positive electrode active material. An appropriate porosity can increase the area of contact between the electrolyte solution and the positive electrode active material, promote ion transport and reaction, and improve low-temperature electrochemical reaction efficiency. However, too high a porosity is not conducive to increase in the energy density of the cell and also has the problem of excessive consumption of electrolyte solution. Too high a porosity may result in a decrease in electrical connection within the positive electrode plate, resulting in a decrease in conductivity and an increase in resistance of the positive electrode plate, thus impairing high discharge performance of the battery at low temperatures. The porosity should not be too low. With low porosity, the electrolyte solution is difficult to flow into the interior of the electrode plate, resulting in uneven wetting, and in regions where the electrolyte solution is excessively enriched, lithium precipitates are generated, which pose a safety risk. This leads to safety risks, since the lithium separates easily. In areas with insufficient wetting, on the other hand, the migration of lithium ions is hindered and the gram capacity is abnormal.With respect to the positive electrode plate, adjustment of the roughness of the positive electrode plate and the porosity of the positive electrode plate can be achieved by adjustment of the particle size and shape, the coating design, the particle size distribution, and the stacking mode of the positive electrode active material, or by adjustment of the coating and rolling conditions of the positive slurry during preparation of the positive electrode plate, or by adjustment of addition of components such as a binder and a dispersant in the positive electrode active material layer, or by performing a surface treatment and a filling treatment of the positive electrode plate.Moreover, the particle size change rate of the positive electrode active material, the roughness of the positive electrode plate, and the porosity of the positive electrode plate also interact specifically. When the porosity of the positive electrode plate is high, the surface of the positive electrode plate may have a specific concave-convex structure, so that the roughness of the positive electrode plate increases. The particle size change rate of the positive electrode active material reflects the particle strength and the proportion of the secondary particles of the positive electrode active material. The degree of the content of secondary particles affects the size of the porosity and the roughness. The particle thickness has an effect on the formation of microcracks, cavities or cavities in the particles of the positive electrode active material and thus also on the porosity of the positive electrode plate.In consideration of the fact that the particle size change rate of the positive electrode active material, the roughness of the positive electrode plate, and the porosity of the positive electrode plate all affect and mutually affect the low-temperature electric power of the battery to some extent. It is difficult to achieve a battery with high capacity retention at low temperature and high discharge performance at low temperature by the control of a single variable. In the present invention, by rationally controlling the particle size change rate D of the positive electrode active material, the roughness R of the positive electrode plate, and the porosity P of the positive electrode plate, the following relationship is satisfied: 1.2≤D / (R / 5+P / 2)≤3.5, so that the battery including the positive electrode plate has a high capacity retention rate at low temperatures and has good discharge performance at low temperatures and high rates.In the present invention, the value of D / (R / 5+P / 2) may be, for example, 1.2, 1.3, 1.5, 1.6, 1.8, 2.0, 2.5, 2.8, 3.0, 3.2, 3.4 or 3.5 or an interval between two of the above values.In one implementation, the particle size change rate D of the positive electrode active material, the positive electrode plate roughness R, and the positive electrode plate porosity P satisfy the following relationship: 1.7≤D / (R / 5+P / 2)≤2.5.In one implementation, the particle size change rate D of the positive electrode active material is in the range of 60% to 90%. For example, D is 60%, 62%, 65%, 70%, 75%, 80%, 85%, 88%, or 90%.In a preferred embodiment, the particle size change rate D of the positive electrode active material is between 65% and 80%.Within the above range of the particle size change rate, the positive electrode active material has an appropriate particle strength and an appropriate amount of secondary particles, whereby it can be ensured that the positive electrode plate has good structural strength and stability, and at the same time, the positive electrode plate can have appropriate pores and voids, which contributes to improvement of the high-rate discharge performance and the capacity retention rate of the battery at low temperature.With respect to the method for determining the particle size change rate D, the present invention is not limited, and a person skilled in the art would have been able to determine the particle size change rate of the positive electrode active material by conventional technical means. By way of example, D can be determined using the following method.The lithium ion battery is disassembled to obtain a positive electrode plate. The positive electrode plate is soaked in DMC (dimethyl carbonate) at normal temperature for 60 minutes. It is taken out and dried at normal temperature and an atmospheric humidity of ≤15%. The positive electrode active material layer is scraped off the surface of the current collector to perform calcination at 500° C. for 3 hours, so that the conductive agent, the binder, the surface-side reaction products, and the remaining electrolyte solution are removed and the positive electrode active material after the post-treatment is obtained.The positive electrode active material is dispersed in an aqueous solution containing 3% sodium hexametaphosphate as a dispersant, and this solution is continuously stirred with a glass rod for 10 cycles. All samples are quickly poured into a sample pool to conduct a D V50- test using a particle size distribution instrument and obtain a Dv50 value before pressure retention recorded as D V50 before pressure.Then, the solid-liquid separation and drying are performed on the mixture containing the positive electrode active material to obtain the positive electrode active material again, and the positive electrode active material is maintained under a pressure of 35 KN by the powder compressor for 30 seconds. After the pressure is maintained, the positive electrode active material is taken out to again conduct a D V50- test in a particle size tester according to the above-mentioned method to obtain a pressure-maintained D V50- value recorded as D V50 after the pressure.The particle size change rate D of the positive electrode active material is obtained by calculation:In the above calculation, D V50 is the particle size in μm corresponding to 50% of the cumulative volume distribution percentage of the positive electrode active material.The particle size change rate of the positive electrode active material depends on various factors, and can be controlled by changing the precursor of the positive electrode active material, the pulverization conditions, and the conditions for the heat treatment in the preparation. It is also possible to obtain a positive electrode active material having a certain particle size change rate by sieving the mass.In one implementation, the positive electrode plate has a roughness R in the range of 80 nm to 200 nm. For example, R may be 80 nm, 90 nm, 100 nm, 120 nm, 150 nm, 180 nm, 190 nm, or 200 nm.In a preferred embodiment, the positive electrode plate has a roughness R in the range from 100 nm to 150 nm.When the roughness is within the above-mentioned preferred range, the positive electrode plate has good contact performance with the electrolytic solution, the battery has high electrochemical reaction efficiency, and the phenomenon of electrode polarization is not exacerbated. The battery has a high capacity retention rate at low temperatures and a high discharge performance at low temperatures.As for the method for determining the roughness R, the present invention is not limited, and a person skilled in the art would have been able to determine the roughness of the positive electrode plate by the usual technical means. For example, R can be determined by the following method.The lithium ion battery is disassembled to obtain a positive electrode plate. The disassembled positive electrode plate is soaked in a solvent (DMC) to clean the remaining electrolyte solution. The solvent is changed every 4 hours. The remaining electrolyte solution is continuously purified 3 times. The positive electrode plate is taken out and dried to obtain an electrode plate sample.A clean and flat 40 mm×40 mm electrode plate sample is selected and fixed on a sample platform of the scanning force microscope. The surface of the positive electrode active material layer of the electrode plate sample is contacted with a scanning force microscope probe and automatically scanned. After completion of the test, obtain the roughness of the electrode plate sample via an "image Ra" value in a "result" of a software test. At least three different sites of the same electrode plate sample are selected for the parallel test and the average value, namely the roughness of the positive electrode plate, is calculated.In one implementation, the positive electrode plate has a porosity P in the range of 15% to 30%. For example, the P may be 15%, 16%, 18%, 20%, 23%, 25%, 28%, 29%, or 30%.In a preferred embodiment, the porosity P of the positive electrode plate is in the range of 18% to 25%.In the context of the present invention, the method for determining the porosity P is not restricted. One skilled in the art would have been able to determine the porosity of the positive electrode plate by the usual technical means. For example, P can be determined by the following method.The lithium ion battery is disassembled to obtain a positive electrode plate. The disassembled positive electrode plate is soaked in a solvent (DMC) to clean the remaining electrolyte solution. The solvent is changed every 4 hours. The remaining electrolyte solution is continuously purified 3 times. The positive electrode plate is taken out, dried and cut into a wafer having a diameter of 12 mm by a punching machine to obtain an electrode plate sample.An electrode plate sample having a diameter of 12 mm is weighed. The electrode plate sample is put in the hexadecane solution and soaked for 1 hour, then taken out. After the solution is blotted on the surface of a filter paper, the electrode plate sample is reweighed. The rate of change of mass of the electrode plate sample before and after soaking in hexadecane is calculated, namely the porosity of the positive electrode plate.In one implementation, the particle size D V50 of the positive electrode active material is 3 μm to 8 μm.In a preferred implementation, the particle size D V50 of the positive electrode active material is in the range of 5 μm to 7.5 μm.When the particle size D V50 of the positive electrode active material is within the above-mentioned preferred range, the positive electrode plate has higher capacity performance and energy density at low temperature and better discharge capacity at high rate.In one implementation, the ternary positive electrode active material has the formulaIn the context of the present invention, the method for preparing LiNi x Co y Mn (1-x-y) O 2 is not restricted. A person skilled in the art can prepare a positive electrode active material using the customary technical means. For example, the precursor of the positive electrode active material and the lithium source are mixed and subjected to sintering treatment to obtain a positive electrode active material.The positive electrode active material precursor may be one or more oxides, hydroxides, and carbonates containing Ni, Co, and Mn in a stoichiometric ratio, for example, hydroxides containing Ni, Co, and Mn in a stoichiometric ratio. The positive electrode active material precursor can be obtained by a method known in the art, for example, by a co-precipitation method, a gel method, or a solid phase method.As an example, a Ni source, a Co source and a Mn source are dispersed in a solvent to obtain a mixed solution. The mixed solution, the strong base solution and the complexing agent solution are simultaneously pumped into a stirred reaction vessel, wherein the pH of the reaction solution is controlled to 10-13 and the temperature in the reaction vessel is controlled to 25°C -90°C. The mixture is protected by an inert gas during the reaction. After completion of the reaction, aging, filtration, deashing and vacuum drying are carried out to obtain a hydroxide containing Ni, Co and Mn.In some examples of the invention, the Ni source comprises at least one of nickel sulfate, nickel nitrate, nickel chloride, nickel oxalate, or nickel acetate, and / or the Co source comprises at least one of cobalt sulfate, cobalt nitrate, cobalt chloride, cobalt oxalate, or cobalt acetate; and / or the Mn source comprises at least one of manganese sulfate, manganese nitrate, manganese chloride, manganese oxalate, or manganese acetate, and / or the Li source comprises at least one of lithium oxide (Li 2 O), lithium phosphate (Li 3 PO 4), lithium dihydrogen phosphate (LiH 2 PO 4), lithium acetate (CH 3 COOLi), lithium hydroxide (LiOH), lithium carbonate (Li 2 CO 3) or lithium nitrate (LiNO 3).The positive electrode active material precursor and the lithium source may be mixed with a ball mill mixer or a high-speed mixer. The mixed material is introduced into an atmospheric sintering furnace for sintering. The sintering atmosphere is an oxygen-containing atmosphere such as an air atmosphere or an oxygen atmosphere.In addition, the positive electrode active material may also be subjected to a coating process. Specifically, a coating material is applied to the surface of the positive electrode active material by dry coating (high-temperature solid phase method). The surface of the positive electrode active material is partially or completely coated with a coating layer formed by the coating material. The coating layer includes at least one element (hereinafter referred to as "coating element") selected from the group consisting of aluminum (Al), titanium (Ti), tungsten (W), boron (B), phosphorus (P), cobalt (Co), yttrium (Y), and silicon (Si).In addition to the positive electrode active material, the positive electrode active material layer may also include a conductive agent and a binder.The conductive agent is used to ensure the electrical conductivity in the electrode. Any conductive agent may be used without particular limitation as long as it has a suitable electric conductivity without causing adverse chemical changes in the battery. This preferably includes carbon fibers such as carbon nanofibers, carbon black such as acetylene black and Ketjen black, and carbon materials such as activated carbon, graphite, mesoporous carbon, fullerenes, and carbon nanotubes.The binder improves the adhesion between the particles of the positive electrode active material and the adhesion between the positive electrode active material and the current collector. Suitable binders for use in embodiments are fluoropolyolefin-based binders, the polyvinylidene fluoride (PVDF), vinylidene fluoride copolymers, or modified (e.g., carboxylic acid, acrylic acid, acrylonitrile, etc.) Derivatives thereof and the like may include, but are not limited to.In the present invention, the positive electrode current collector is not particularly limited as long as it is electrically conductive without causing adverse chemical changes in the battery, and the positive electrode current collector includes, for example, stainless steel, aluminum, nickel, titanium, fired carbon or aluminum or stainless steel surface-treated with any one of carbon, nickel, titanium, silver, etc.In the context of the present invention, the positive electrode plate can be prepared by the customary methods of the prior art. For example, a positive electrode active material, a conductive agent, and a binder are dispersed in a solvent. The solvent may be N-methylpyrrolidone, NMP or deionized water to form a uniform positive slurry. The positive slurry is applied to a positive electrode current collector. After drying, rolling and the like, a positive electrode plate is obtained.Electrochemical DeviceAccording to an example of the present invention, an electrochemical device is provided. The electrochemical device includes the positive electrode plate as described above, a negative electrode plate and an electrolyte solution.The negative electrode plate of the present invention includes a negative electrode current collector and a negative electrode active material layer provided on at least one surface of the negative electrode current collector. The negative electrode active material layer includes a negative electrode active material and may also include a conductive agent and / or a binder.The negative electrode current collector is not particularly limited in the present invention as long as it has high conductivity without causing adverse chemical changes in the battery. For example, copper, stainless steel, aluminum, nickel, titanium, fired carbon, copper, or stainless steel surface-treated with carbon, nickel, titanium, silver, or the like, or an aluminum-cadmium alloy may be used.As for the negative electrode active material, the kind of the negative electrode active material in the examples of the present invention is not specifically limited and can be selected according to practical requirements. The negative electrode active material may be, for example, one or more of natural graphite, artificial graphite, mesophase carbon microspheres (MCMB), hard carbon, soft carbon, silicon, silicon-carbon composite, SiOm (0<m<2, e.g., m=1), Li-Sn alloy, Li-Sn-O alloy, Sn, SnO, SnO2, spinel-structured lithium titanate Li 4 Ti 5 O 12, Li-Al alloy, and metallic lithium.The examples of the present invention do not particularly limit the types of the conductive agent and the binder in the negative electrode active material layer, and can be selected according to practical requirements. The conductive agent includes, for example, one or more of graphite, superconducting carbon, acetylene black, carbon black, ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers. The binder includes one or more of styrene-butadiene rubber, polyvinylidene fluoride, polytetrafluoroethylene, polyvinyl butyral, aqueous acrylic resin, and carboxymethyl cellulose. The negative electrode active material layer may optionally also comprise a thickener such as carboxymethylcellulose.The electrolyte solution of the present invention may be any electrolyte solution suitable for use in electrochemical energy storage devices in the prior art. The electrolyte solution includes an electrolyte and a solvent. The electrolyte solution may generally comprise a lithium salt.More specifically, the lithium salt includes at least one of lithium hexafluorophosphate (LiPF 6), lithium tetrafluoroborate (LiB 4), lithium perchlorate (LiClO 4), lithium hexafluoroarsenate (LiAsF 6), lithium bisfluorosulfonimide (LiFSI), lithium bistrifluoromethosulfonimide (LiTFSI), lithium triflate (LiTFS), lithium difluorooxalate borate (LiDFOB), lithium dioxalate borate (LiBO), lithium difluorophosphate (LiPO 2 F 2), Lithium difluorooxalate phosphate (LiDFOP) and lithium tetrafluorooxalate phosphate (LiTFOP). The concentration of the electrolyte in the electrolyte solution may be 0.5 mol / L to 5 mol / L.In some embodiments, the solvent may be selected from at least one of ethylene carbonate (EC), propylene carbonate (PC), ethylmethyl carbonate (EMC), diethyl carbonate (DEC), dimethyl carbonate (DMC), dipropyl carbonate (DPC), methylpropyl carbonate (MPC), ethylpropyl carbonate (EPC), butylene carbonate (BC), fluoroethylene carbonate (FEC), methyl formate (MF), methyl acetate (MA), ethyl acetate (EA), 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), methylethyl sulfone (EMS), and diethyl sulfone (ESE). The solvent may be contained in an amount of 70 to 98% by weight based on the weight of the electrolyte solution.In addition, the electrolyte solution may include additives. Specifically, the additive may include a membrane-forming additive for the negative electrode plate, and the additive may include a membrane-forming additive for the positive electrode plate, and the additive may include an additive capable of improving specific characteristics of the battery, e.g., an additive for improving overcharge characteristics of the battery, an additive for improving high-temperature characteristics of the battery, or an additive for improving low-temperature characteristics of the battery, etc.The electrochemical device may further include a separator disposed between the positive electrode plate and the negative electrode plate to separate the positive electrode plate and the negative electrode plate from each other and prevent the positive electrode plate and the negative electrode plate from contacting each other and causing a short circuit. The separator may be any material known in the art that is useful as a separator for electrochemical energy storage devices. In particular, the separator comprises at least one of the following materials: polyethylene, polypropylene, polyvinylidene fluoride, aramid, polyethylene terephthalate, polytetrafluoroethylene, polyacrylonitrile, polyimide, polyamide, polyester and natural fiber.Electrical DeviceExamples of the present invention provide an electrical device comprising the electrochemical device described above. The electrochemical device serves as a power supply for the electrical device.The electrical device refers to any device that can use and convert electrical energy into mechanical energy, thermal energy, light energy, etc., such as an electric motor, an electric heat engine, an electrical light source, etc. The electrical device can include, but is not limited to, a mobile device, an electric vehicle, an electric train, a ship and satellite, an energy storage system, etc. The mobile device may be a mobile telephone, a notebook, an unmanned aerial vehicle or drone, a sweeping robot, an electric cigarette, etc. The electric vehicle may be a pure electric vehicle, a hybrid electric vehicle, a plug-in hybrid electric vehicle, an electric bicycle, an electric scooter, an electric golf cart, an electric truck, or the like.The invention is further illustrated by the following specific examples.Example 1This example provides a lithium ion battery, and the specific preparation method is as follows.(1) Preparation of positive electrode plateStep (1.1): According to the molar ratio of the individual elements Li, Ni, Co and Mn in the chemical formula LiNi 0.9 Coo.osMn 0.05 O 2 nickel sulfate, cobalt sulfate, manganese sulfate and lithium carbonate are respectively weighed. The lithium carbonate is slightly present in excess. The ratio between the molar amount of lithium carbonate and the total molar amount of nickel sulfate, cobalt sulfate and manganese sulfate (Li / Me) is shown in Table 1Step (1.2): Nickel sulfate, cobalt sulfate and manganese sulfate are each dissolved in deionized water. Each metal solution is transferred through a piping into a reaction vessel to form a mixed metal solution, introducing nitrogen as a shielding gas. An aqueous NaOH solution is added as precipitant and ammonia as complexing agent to the mixed metal solution. The ammonia concentration and the addition amount of the solution are adjusted to control the pH of the solution (i.e., the pH of the precursor reaction). After the 10-hour reaction, the product is filtered and dried to obtain a ternary precursor. The pH of the precursor reaction and the drying temperature (i.e., the drying temperature of the precursor) are shown in Table 1.Step (1.3): The ternary precursor is mixed with a part of lithium carbonate (20 wt % of lithium carbonate) to perform the pre-sintering. The pre-sintering atmosphere is an oxygen-containing atmosphere (oxygen throughput 120 m 3 / h). The pre-sintering time is 3 hours, and the pre-sintering temperature is shown in Table 1. After cooling, the pre-sintered product is mixed with the remaining lithium carbonate (80 wt % lithium carbonate) and the high-temperature sintering is carried out. The high temperature sintering atmosphere is an oxygen-containing atmosphere. The controlled oxygen flow rate and the temperature and time duration of the high temperature sintering are given in Table 1.Step (1.4): The sintered material is ground, crushed and sieved to obtain a ternary positive electrode active material.Step (1.5): A positive electrode active material, a binder (polyvinylidene fluoride), and a conductive agent (carbon black) are mixed in a mass ratio of 97:1:2. N-methylpyrrolidone (NMP) is added to the mixture and stirred under the action of a vacuum stirrer until the mixed system forms a positive slurry having uniform flowability. The positive slurry is uniformly applied to the positive electrode current collector (aluminum foil). The positive electrode current collector coated with the positive slurry is placed in a furnace for drying, and then rolled and cut to obtain a positive electrode plate.(2) Preparation of Negative Electrode PlateA negative electrode active material (artificial graphite), a conductive agent (CNT), a thickener (carboxymethylcellulose, CMC), and a binder (styrene-butadiene rubber, SBR) are mixed in a mass ratio of 96:2:1:1. A negative slurry is prepared in a wet process using a vacuum stirrer. The negative slurry is uniformly applied to a negative electrode current collector (a copper foil). The negative slurry coated with the negative electrode current collector is placed in a furnace for drying, and then rolled and cut to obtain a negative electrode plate.(3) Preparation of the electrolyte solutionEthylene carbonate (EC) and ethyl methyl carbonate (EMC) are mixed in a weight ratio of 1:1 to obtain an organic solvent, and then sufficiently dried lithium salt LiPF 6 is dissolved in the mixed organic solvent to prepare an electrolyte solution having a concentration of 1 mol / L.(4) Preparation of the separatorA polyethylene (PE) separator coated with ceramic and polyvinylidene fluoride is used.(5) Preparation of the batteryThe prepared positive electrode plate, the separator, and the negative electrode plate are wound to obtain a bare cell without liquid injection. The bare cell is placed in an outer packaging film. The above-mentioned prepared electrolytic solution is injected into the dried bare cell. This is vacuum-packaged, laid up, shaped, sorted, and subjected to other processes to obtain a lithium ion battery.Examples 2-13 and Comparative Examples 1-3Examples 2 to 13 and Comparative Examples 1 to 3 each provide a lithium ion battery whose preparation method is similar to that of Example 1, except that in the preparation of the positive electrode plate, the reaction pH value of the precursor, the drying temperature of the precursor, Li / Me, the oxygen flow rate for high-temperature sintering, the temperature, and the time period are shown in Table 1.Examples 14 and 16Examples 14 and 16 each provide a lithium ion battery whose preparation method is similar to that of Example 1, except that: (a) In step (1.1) and step (1.2), the pH of the precursor reaction, the drying temperature of the precursor, and Li / Me are shown in Table 1. (b) In step (1.3), the ternary precursor is mixed with the entire lithium carbonate, pre-sintered, and directly sintered at high temperature. The high temperature sintering atmosphere is an oxygen-containing atmosphere. The control of the oxygen throughput and the temperature and duration of the high-temperature sintering are listed in Table 1.Example 15Examples 14 and 15 each provide a lithium ion battery whose preparation method is similar to that of Example 1, except that: (a) In step (1.1) and step (1.2), the pH of the precursor reaction, the drying temperature of the precursor, and Li / Me are shown in Table 1; (b) In step (1.3), the ternary precursor is mixed with a part of the lithium carbonate (30% by weight of lithium carbonate) to perform the pre-sintering. The pre-sintering atmosphere is an oxygen-containing atmosphere (the oxygen flow rate is 120 m3 / h). The pre-sintering time is 3 hours. The temperature before sintering is shown in Table 1. After cooling, the pre-sintered product is mixed with the remaining lithium carbonate (70% by weight of lithium carbonate) and subjected to high-temperature sintering. The high temperature sintering atmosphere is an oxygen-containing atmosphere. The control of the oxygen throughput and the temperature and duration of the high-temperature sintering are given in Table 1.Examples 17 and 18Examples 17 and 18 each provide a lithium ion battery, the preparation method of which is similar to that of Example 1, and the details of which are described below.Example 17: According to the molar ratio of the individual elements Li, Ni, Co and Mn in the chemical formula LiNi 0,8 Co 0,1 Mn 0,1 O 2 nickel sulfate, cobalt sulfate, manganese sulfate and lithium carbonate are weighed in. The lithium carbonate is slightly present in excess. The control of the pH of the precursor reaction, the drying temperature of the precursor, Li / Me, the oxygen flow rate for high temperature sintering, the temperature and the time period are shown in Table 1.Example 18: According to the molar ratio of the individual elements Li, Ni, Co and Mn in the chemical formula LiNi 0,7 Co 0,2 Mn 0,1 O2, nickel sulfate, cobalt sulfate, manganese sulfate and lithium carbonate are weighed. The lithium carbonate is slightly present in excess. The control of the pH of the precursor reaction, the drying temperature of the precursor, the Li / Me, the oxygen flow rate for high temperature sintering, the temperature and the time period are shown in Table 1.Further, in each of the examples and comparative examples of the present invention, the roughness and porosity of the positive electrode plate are adjusted by controlling the conditions of the positive slurry coating and the rolling in combination with the use of various positive electrode active materials.

[0126] Table 1

[0126] Table 1Example 19,71251,2 535020080010Example 29,31301,2 04202307508Example 310,51201,1 53302107808,5Example 410,11151,1 830022083012Example 59,41251,1 54001608109Example 611,21301,2 338020082011Example 711,41151,3 535018079012Example 89,51251,1 537015070010Example 910,31151,3 23302508508Example 109,91301,2 83201707709,5Example 119,61151,1 23801907409Example 129,71301,1 540021075011Example 1312,11151,335022080010,5Example 1411,81101,2 8 / 22078012Example 1512,31151,1 53302308607,5Example 169,41101,1 / 16070012,5Example 1710,61301,3 13002008308,5Example 1810,31201,3 738024084010Comparative example 19,91301,1 940020076011Comparative example 211,41101,2 54202208208The end of the comparison was complete10,21501,235025081012Example 3For each of Examples and Comparative Examples, the roughness and porosity of the positive electrode plate and the D V50 and the particle size change rate of the positive electrode active material are measured as shown in Table 2, and the above-mentioned measurement methods are as follows:D V50 and the particle size change rate of the positive electrode active materialThe lithium ion battery is disassembled to obtain a positive electrode plate. The positive electrode plate is soaked in DMC (dimethyl carbonate) at normal temperature for 60 minutes, taken out, and dried at normal temperature with an air humidity of ≤15%. The positive electrode active material layer is scraped off the surface of the current collector to perform calcination at 500° C. for 3 hours, so that the conductive agent, the binder, the surface-side reaction products, and the remaining electrolyte solution are removed and the positive electrode active material after the post-treatment is obtained.The positive electrode active material is dispersed in an aqueous solution containing 3% sodium hexametaphosphate as a dispersant, and this solution is continuously stirred with a glass rod for 10 cycles. All samples are rapidly poured into a sample pool for a particle size distribution instrument to perform a D V50- test and obtain a Dv50 before pressurization recorded as D V50 before the pressure, namely, the Dv50 of the positive electrode active material.Then, the solid-liquid separation and drying are performed on the mixture containing the positive electrode active material to obtain the positive electrode active material again, and the positive electrode active material is maintained under a pressure of 35 KN in a powder compressor for 30 seconds. After the pressure is maintained, the positive electrode active material is taken out to again conduct a D V50- test in a particle size tester according to the above-mentioned method to obtain a D V50 after maintaining the pressure, which is recorded as D V50 after the pressure.The particle size change rate D of the positive electrode active material is obtained by calculation:D V50 is the particle size in μm corresponding to 50% of the cumulative volume distribution percentage of the positive electrode active material.Roughness of Positive Electrode PlateThe lithium ion battery is disassembled to obtain a positive electrode plate. The disassembled positive electrode plate is soaked in a solvent (DMC) to clean the remaining electrolyte solution. The solvent is changed every 4 hours. The remaining electrolyte solution is continuously purified 3 times. The positive electrode plate is taken out and dried to obtain an electrode plate sample.A clean and flat 40 mm×40 mm electrode plate sample is selected and fixed on a scanning force microscope sample platform. An atomic force microscope probe touches the surface of the electrode plate sample and performs automatic scanning. After completion of the test, obtain the roughness of the electrode plate sample via an "image Ra" value in a "result" of test software. At least three different sites of the same electrode plate sample are selected for the parallel test and the average value, namely the roughness of the positive electrode plate, is calculated.Porosity of Positive Electrode PlateThe lithium ion battery is disassembled to obtain a positive electrode plate. The disassembled positive electrode plate is soaked in a solvent (DMC) to clean the remaining electrolyte solution. The solvent is changed every 4 hours. The remaining electrolyte solution is continuously purified 3 times. The positive electrode plate is taken out, dried and cut into a wafer of 12 mm in diameter by a sheet punch to obtain an electrode plate sample.An electrode plate sample having a diameter of 12 mm is weighed. The electrode plate sample is placed in the hexadecane solution and soaked for 1 hour, then taken out. After the solution is blotted on the surface of a filter paper, the electrode plate sample is reweighed. The rate of change of mass of the electrode plate sample before and after soaking in hexadecane is calculated, i.e. the porosity of the positive electrode plate.

[0140] Table 2

[0140] Table 2Example 16,568,111422,771,99Example 26,96613518,211,83Example 35,871,510320,352,32Example 46,177,811019,32,46Example 57,272,214724,21,74Example 64,862,811328,51,70Example 74,483,49533,292,34Example 86,876,717416,521,78Example 95,579,610218,742,67Example 107,565,114524,941,57Example 117,78319133,71,51Example 127,362,117234,531,20Example 134,07883212,88Example 144,188,98617,173,45Example 154,693,612113,33,03Example 167,486,1230391,31Example 176,2639721,12,10Example 186,460,58318,92,32Comparative Example 17,161198331,09Comparative Example 25,189,681,315,23,76Comparative Example 36,24612732,11,11The lithium ion batteries prepared in the examples and comparative examples are subjected to power tests according to the following projects and methods.(1) Capacity Maintenance Rate in -10°C CycleThe lithium ion battery is placed in an environment of -10° C. and is standing until the lithium ion battery reaches a constant temperature. At -10°C, the lithium ion battery is charged to 4.3V at a constant current of 0.2C, and the lithium ion battery is charged to a current of 0.05C at a constant voltage. The lithium ion battery is discharged to 2.75 V at 0.33 C, and this capacity is taken as the initial capacity C 0. This step is repeated for 500 cycles and the capacity of 500 cycles is recorded as C1. The capacity retention rate for the low temperature cycle is calculated: capacity retention rate for the low temperature cycle=C1 / C0×10%.(2) Discharge power at 5°CThe lithium ion battery is set up in an environment of 5° C. until the lithium ion battery reaches a constant temperature. The lithium ion battery is charged to 4.3V at 5°C with a constant current / voltage of 0.33C, set aside for 10 minutes, and discharged to a shutdown voltage of 2.8V with a constant current of 0.33C, and the discharge capacity is recorded as C3. The lithium ion battery is charged at 5°C to 4.3V with a constant current / voltage of 0.33C, set aside for 10 minutes and charged with a constant current of 2C to a cut-off voltage of 2.8V, and the discharge capacity is recorded as C4. The capacity retention rate for the discharge capacity is calculated according to the following formula: capacity retention rate for the discharge capacity=C4 / C3×100%.The test results are shown in Table 3.

[0147] Table 3

[0147] Table 3Capacity Maintenance Rate in -10° C. Cycle (%)5°C Rate of discharge powerExample 195,2%98,5%Example 294,0%98,0%Example 393,7%98,1%Example 493,1%98,9%Example 594,4%99,1%Example 690,8%96,2%Example 791,6%96,5%Example 891,9%97,8%Example 989,0%94,9%Example 1088,5%95,4%Example 1185,5%94,2%Example 1286,2%93,6%Example 1386,8%92,9%Example 1487,3%92,5%Example 1584,6%91,0%Example 1683,9%91,2%Example 1789,5%95,3%Example 1888,1%95,8%Comparative Example 170,3%84,2%Comparative Example 272,7%82,1%Comparative Example 366,8%84,5%For the lithium ion battery manufactured in each example of the present invention, the capacity retention rate after 500 cycles at -10° C. ≥ 83%, and the capacity retention rate in a 2 C. rate discharge at 5° C. ≥ 91%. It is found that the lithium ion battery comprising the positive electrode plate of the present invention has significantly improved electrochemical performance at low temperatures, particularly, excellent capacity retention rate at low temperatures and discharge performance at high rates at low temperatures.From Examples 6 to 8 in combination with Examples 1 to 5 and Examples 11 to 14 in combination with Comparative Examples 9 and 10, it is understood that the capacity retention rate at low temperature cycles and the discharge performance of the lithium ion battery at high temperatures are relatively better when the particle size change rate of the positive electrode active material, the roughness, and the porosity of the positive electrode plate satisfy the preferred range of the present invention.From Examples 9 to 10 in combination with Examples 1 to 5, it can be seen that the capacity retention rate at low temperatures and the discharge performance of the lithium ion battery at high temperatures are relatively higher when the positive electrode plate satisfies a value of D / (R / 5+P / 2) of 1.7 to 2.5.According to the test results of Comparative Examples 1 to 3, even when the roughness and porosity of the positive electrode plate or the particle size change rate of the positive electrode active material are in appropriate ranges, when the D / (R / 5+P / 2) value of the positive electrode plate exceeds the range of 1.2 to 3.5, the lithium ion battery including the positive electrode plate has poor electrochemical performance at low temperatures, with a capacity retention rate at low temperatures of not more than 72.7%, and a capacity retention rate at low temperatures at discharge of not more than 84.5%.

Claims

An electrochemical device, namely a lithium ion battery, comprising a positive electrode plate having a positive electrode current collector and a positive electrode active material layer provided on at least one surface of the positive electrode current collector, wherein the positive electrode current collector comprises stainless steel, aluminum, nickel, titanium, fired carbon or aluminum, a negative electrode plate comprising a negative electrode current collector and a negative electrode active material layer provided on at least one surface of the negative electrode current collector, wherein the negative electrode active material layer comprises a negative electrode active material, and wherein the negative electrode current collector comprises copper, stainless steel, aluminum, nickel, titanium, fired carbon or an aluminum-cadmium alloy; a separator between the positive electrode plate and the negative electrode plate, the separator comprising at least one of polyethylene, polypropylene, polyvinylidene fluoride, aramid, polyethylene terephthalate, polytetrafluoroethylene, polyacrylonitrile, polyimide, polyamide, polyester, and natural fiber; characterized in that the positive electrode active material layer has a positive electrode active material comprising a ternary positive electrode active material; a particle size change rate of the positive electrode active material, a roughness of the positive electrode plate, and a porosity of the positive electrode plate satisfy the following relationship: 1.2≤D / (R / 5+P / 2)≤3.5; _ner1 - wherein D is the particle size change rate of D V50 in % before and after the positive electrode active material is maintained at a pressure of 35 KN for 30 seconds, and D V50 is a particle size corresponding to 50% of a cumulative volume distribution percentage of the positive electrode active material; R is the roughness of the positive electrode plate in nm; and P is the porosity of the positive electrode plate in %.The electrochemical device according to claim 1, characterized in that the particle size change rate of the positive electrode active material, the roughness of the positive electrode plate, and the porosity of the positive electrode plate satisfy the following relationship: 1.7 ≤ D / ( R / 5 + P / 2) ≤ 2.

5. Electrochemical device according to one of the preceding claims, characterized in that D is in the range from 60% to 90%.Electrochemical device according to one of the preceding claims, characterized in that D is in the range from 65% to 80%.Electrochemical device according to one of the preceding claims, characterized in that R is in the range from 80 nm to 200 nm.Electrochemical device according to one of the preceding claims, characterized in that R is in the range from 100 nm to 150 nm.Electrochemical device according to one of the preceding claims, characterized in that P is between 15% and 35%.Electrochemical device according to one of the preceding claims, characterized in that P is in the range from 18% to 25%.Electrochemical device according to one of the preceding claims, characterized in that D V50 is in the range from 3 μm to 8 μm.Electrochemical device according to one of the preceding claims, characterized in that the ternary positive electrode active material has the formula LiNi x Co y Mn (1-x-y) O 2 where 0.7≤x<1, 0<y≤0.3, and 0<x+y<1.Electrochemical device according to one of claims 1 to 9, characterised in that the ternary positive electrode active material has the formula LiNi x Co y Mn (1-x-y) O 2 wherein 0.8≤x<1, 0<y≤0.3, and 0<x+y<1.Electrochemical device according to one of Claims 1 to 9, characterized in that the ternary positive electrode active material has the formula LiNi x Co y Mn (1-x-y) O 2 where 0.9≤x<1, 0<y≤0.3, and 0<x+y<2.The electrochemical device according to any one of the preceding claims, wherein the positive electrode active material layer may comprise a conductive agent and a binder in addition to the positive electrode active material.The electrochemical device according to any one of the preceding claims, wherein the conductive means comprises carbon fibers, carbon black and / or carbon materials.The electrochemical device of any preceding claim, wherein the binder is a fluoropolyolefin-based binder.The electrochemical device of any preceding claim, wherein the negative electrode active material comprises one or more of natural graphite, artificial graphite, mesophase carbon microspheres, MCMB, hard carbon, soft carbon.Electrochemical device according to one of the preceding claims, wherein the negative electrode active material comprises one or more of the following materials: silicon, silicon-carbon composite material and SiOm with 0<m<2, e.g. m=1.The electrochemical device according to any one of the preceding claims, wherein the negative electrode active material comprises one or more of the following materials: Li-Al alloy and metallic lithium.The electrochemical device according to any one of the preceding claims, wherein the negative electrode active material comprises one or more of the following materials: spinel-structured lithium titanate Li 4 Ti 5 O 12, Li-Sn alloy, Li-Sn-O alloy, Sn, SnO and SnO 2.The electrochemical device of any preceding claim, wherein the negative electrode active material comprises a conductive agent.The electrochemical device of claim 20, wherein the conductive agent of the negative electrode plate comprises one or more of graphite, superconducting carbon, acetylene black, carbon black, ketjen black, carbon spots, carbon nanotubes, graphene, and carbon nanofibers.The electrochemical device of any preceding claim, wherein the negative electrode active material comprises a binder.The electrochemical device of claim 22, wherein the binder of the negative electrode plate comprises one or more of styrene-butadiene rubber, polyvinylidene fluoride, polytetrafluoroethylene, polyvinyl butyral, aqueous acrylic resin, and carboxymethylcellulose.The electrochemical device according to any one of the preceding claims, wherein the negative electrode active material layer comprises a thickener, e.g. carboxymethylcellulose.Electrochemical device according to any one of the preceding claims, comprising an electrolyte solution and an electrolyte, respectively, wherein the electrolyte solution comprises an electrolyte and a solvent.The electrochemical device of claim 25, wherein the electrolyte comprises a lithium salt.The electrochemical device of claim 26, wherein the lithium salt comprises at least one of lithium hexafluorophosphate or LiPF 6, lithium tetrafluoroborate or LiF 4, lithium perchlorate or LiClO 4, lithium hexafluoroarsenate or LiAsF 6, lithium bisfluorosulfonimide or LiFSI, lithium bistrifluoromethosulfonimide or LiTFSI, lithium triflate or LiTFS, lithium difluorooxalate borate or LiDFOB, lithium dioxalate or LiBO, lithium difluorophosphate or LiPO 2 F 2, Lithium difluorooxalate phosphate or LiDFOP and lithium tetrafluorooxalate phosphate or LiTFOP.The electrochemical device according to any one of claims 25 to 27, wherein the concentration of the electrolyte in the electrolyte solution is 0.5 to 5 mol / L.Electrochemical device according to any one of claims 25 to 28, wherein the solvent is at least one of ethylene carbonate or EC, propylene carbonate or PC, ethylmethyl carbonate or EMC, diethyl carbonate or DEC, dimethyl carbonate or DMC, dipropyl carbonate or DPC, methylpropyl carbonate or MPC, ethylpropyl carbonate or EPC, butylene carbonate or BC, fluoroethylene carbonate or FEC, methyl formate or MF, methyl acetate or MA, ethyl acetate or EA, propyl acetate or PA, methyl propionate or MP, ethyl propionate or EP, propyl propionate or PP, methyl butyrate or MB, The compounds of the invention are preferably used in the preparation of a compound of formula I. Ethyl butyrate or EB, 1,4-butyrolactone or GBL, sulfolane or SF, dimethyl sulfone or MSM, methylethyl sulfone or EMS and diethyl sulfone or ESE.The electrochemical device according to any one of claims 25 to 29, wherein the solvent is contained in an amount of 70 to 98% by weight based on the weight of the electrolyte solution.The electrochemical device according to any one of claims 25 to 30, wherein the electrolyte solution comprises a membrane-forming additive for the negative electrode plate and a membrane-forming additive for the positive electrode plate.Use of an electrochemical device according to one of the preceding claims as a power supply for an electrical device, the electrical device comprising: electric motor, heat engine, light source, vehicle, train, ship, satellite, energy storage system, mobile telephone, notebook, unmanned aerial vehicle, sweeping robot, or electric cigarette.The use of claim 32, wherein the vehicle is a pure electric vehicle, a hybrid electric vehicle, a plug-in hybrid electric vehicle, an electric bicycle, an electric scooter, an electric golf cart, or an electric truck.An electrical device, characterized in that it comprises the electrochemical device according to any one of claims 1 to 31.The electrical device of claim 34, wherein the electrochemical device serves as a power supply for the electrical device.Electrical device according to Claim 35, which is designed as an electric motor, heat engine, light source, vehicle, train, ship, satellite, energy storage system, mobile telephone, notebook, unmanned aerial vehicle, sweeping robot or electric cigarette.The electrical device of claim 36, wherein the vehicle is a pure electric vehicle, a hybrid electric vehicle, a plug-in hybrid electric vehicle, an electric bicycle, an electric scooter, an electric golf cart, or an electric truck.