Electrode and preparation method thereof, electrochemical device and electronic device

Abstract

The invention discloses an electrode, a preparation method thereof, an electrochemical device and an electronic device. The electrode comprises a current collector and an active material layer arranged on at least one surface of the current collector; thermogravimetric analysis is carried out on the active material layer at the temperature rising speed of 10 DEG C / min in an inert atmosphere, and the result of the thermogravimetric analysis shows that the mass change of the active material layer at the temperature of 200 DEG C to 350 DEG C is 0% to 0.2%. The active material layer of the electrode has good conductivity, so that the thickness of the active material layer is increased while the performance is not deteriorated, and the electric energy density is improved.

Description

[0001] This application is a divisional application of a Chinese patent application with the application number 202180026343.3, the filing date of November 15, 2021, and the invention title of "Electrode and Its Preparation Method, Electrochemical Device and Electronic Device". Technical Field

[0002] This application relates to the field of electrochemical energy storage, and in particular to an electrode and its preparation method, an electrochemical device and an electronic device. Background Art

[0003] Electrochemical devices, such as lithium-ion batteries, have advantages such as high energy density, high power, and long cycle life, and are widely used in various fields. With the development of technology, the requirements for the energy density of electrochemical devices are getting higher and higher. To improve the energy density of electrochemical devices, in some technologies, the capacity or voltage of the active material is increased, and in other technologies, the content of the active material per unit volume is increased, and the content of the inactive material is reduced. By reducing the thickness of the current collector or the separator, reducing the proportion of the inactive material in the formulation, and preparing a thicker electrode, etc., the proportion of the inactive substance can be reduced. However, in the actual application process, the thicknesses of the current collector and the separator have been reduced to nearly the limit. Therefore, only the electrode thickness can be increased. However, if the electrode thickness is increased too much, it may affect the performance of the electrochemical device. Therefore, it is impossible to significantly increase the electrode thickness. Therefore, how to increase the electrode thickness as much as possible to increase the capacity of the electrochemical device while ensuring the performance of the electrochemical device is an urgent problem to be solved. Summary of the Invention

[0004] Some embodiments of this application provide an electrode and its preparation method, an electrochemical device and an electronic device. Among them, under an inert atmosphere, the active material layer of the electrode is subjected to thermogravimetric analysis at a heating rate of 10 °C / min. The result of the thermogravimetric analysis shows that the mass change of the active material layer is 0% to 0.2% at 200 °C to 350 °C, thereby improving the conductivity of the active material layer, and further being beneficial to increasing the thickness of the active material layer to improve the energy density of the electrochemical device.

[0005] In some embodiments of the present application, an electrode is proposed, which includes a current collector and an active material layer disposed on at least one surface of the current collector; under an inert atmosphere, thermogravimetric analysis is performed on the active material layer at a heating rate of 10 °C / min. The results of the thermogravimetric analysis show that the mass change of the active material layer is 0% to 0.2% at 200 °C to 350 °C, indicating that the content of polymer compounds with a decomposition temperature lower than 350 °C in the active material layer in the present application is zero or extremely low, which is beneficial to improving the ion and electron conduction in the active material layer. In some embodiments, the polymer compounds with a decomposition temperature lower than 350 °C come from the binder and / or thickener in the electrode. In some embodiments, the active material layer hardly contains polymer compounds with a low decomposition temperature, which is beneficial to improving the conductivity and thus improving the energy density.

[0006] In some embodiments of the present application, the results of the thermogravimetric analysis show that the number of weight loss peaks of the active material layer is 0 at 200 °C to 350 °C, and the number of weight loss peaks of the active material layer is not less than 1 at 350 °C to 800 °C. This indicates that the active material layer in the present application has good conductivity, which is beneficial to increasing the thickness of the electrode, and thus beneficial to increasing the capacity and energy density of the electrochemical device.

[0007] In some embodiments, the results of the thermogravimetric analysis show that the mass change of the active material layer is 0.21% to 13% at 350 °C to 800 °C. In some embodiments, the results of the thermogravimetric analysis show that the mass change of the active material layer is 0.77% to 3.4% at 350 °C to 800 °C.

[0008] In some embodiments of the present application, the electrode is a negative electrode. In some embodiments, the electrode is a negative electrode, and the compaction density ρ of the active material layer ≥ 0.6 g / cm 3 , and a higher compaction density is beneficial to increasing the energy that can be stored per unit volume of the electrochemical device. In some embodiments, the thickness h of the active material layer on one side of the current collector ≥ 10 μm, and a thicker thickness is beneficial to carrying more active materials, thereby increasing the energy density of the electrochemical device. In some embodiments, the adhesion force F between the active material layer and the current collector satisfies: 300 N / m ≥ F ≥ 0.5 N / m, which can ensure that there is sufficient adhesion force between the active material layer and the current collector, and can also prevent the problem of decreased conductivity caused by excessive binder required due to excessive adhesion force. In some embodiments, the resistivity of the active material layer is 0.01 Ω·cm to 50 Ω·cm, indicating that the active material layer of the present application has good conductivity, which is beneficial to the charge and discharge performance of the electrochemical device. In some embodiments, the active material layer includes a negative electrode material, and the negative electrode material includes at least one of lithium titanate, silicon monoxide, graphite, silicon, or hard carbon.

[0009] In some embodiments of the present application, the compaction density ρ of the active material layer satisfies: 1.85 g / cm3 1.83 g / cm ≥ ρ ≥ 1.0 g / cm 3 , which is beneficial to improving the energy density of the electrochemical device. In some embodiments, the thickness h of the active material layer on one side of the current collector satisfies: 1500 μm ≥ h ≥ 15 μm, which is beneficial to preventing the shedding of the active material layer while improving the energy density of the electrochemical device. In some embodiments, the adhesion force F between the active material layer and the current collector satisfies: 150 N / m ≥ F ≥ 1 N / m, thereby ensuring conductivity while increasing the adhesion force.

[0010] In some embodiments of the present application, the compaction density ρ of the active material layer satisfies: 1.83 g / cm 3 1.83 g / cm ≥ ρ ≥ 1.0 g / cm 3 . In some embodiments of the present application, the thickness h of the active material layer on one side of the current collector satisfies: 150 μm ≥ h ≥ 30 μm. In some embodiments of the present application, the adhesion force F between the active material layer and the current collector satisfies: 20 N / m ≥ F ≥ 1 N / m.

[0011] In some embodiments of the present application, the active material layer includes a conductive agent, and the conductive agent includes at least one of carbon nanotubes, carbon fibers, acetylene black, graphene, Ketjen black, or conductive carbon black. In some embodiments, the active material layer includes a conductive agent, and based on the total mass of the active material layer, the mass percentage content of the conductive agent in the active material layer is 0% to 2%.

[0012] In some embodiments, the active material layer includes a polymer compound, and the polymer compound includes at least one of polyethylene oxide, polypropylene oxide, polyvinylidene fluoride, polytetrafluoroethylene, polyacrylonitrile, polyimide, polysiloxane, polyacrylic acid, polypropylene derivatives, sodium carboxymethyl cellulose, lithium carboxymethyl cellulose, poly-N-methylpyrrolidone, polyvinylpyrrolidone, styrene acrylate, or styrene-butadiene rubber. In some embodiments, the active material layer includes a polymer compound, and based on the total mass of the active material layer, the mass percentage content of the polymer compound in the active material layer is 0.22% to 14%. In some embodiments of the present application, the active material layer includes a polymer compound, and based on the total mass of the active material layer, the mass percentage content of the polymer compound in the active material layer is 0.8% to 3.5%.

[0013] In some embodiments of the present application, a method for preparing an electrode is proposed, which can be used to manufacture any electrode in the present application, including: coating a slurry of an active material layer on at least one surface of a current collector, drying, and cold pressing to obtain an initial electrode; processing the initial electrode to obtain an electrode; wherein, processing the initial electrode includes: performing plasma treatment on the initial electrode in a vacuum environment, with a plasma power of 0.5 kW to 5 kW, the gas source including at least one of nitrogen, argon, or carbon tetrafluoride, a gas flow rate of 3000 sccm to 5000 sccm, a temperature of 20 °C to 60 °C, and a processing time of 1 min to 60 min; or, performing heat treatment on the initial electrode in a vacuum or inert gas environment, with a heat treatment temperature of 200 °C to 400 °C and a heat treatment time of not less than 5 min; or, performing laser bombardment on the initial electrode in a vacuum or inert gas environment, with a laser intensity of 25 W to 30 W and a processing time of 1 s to 600 s.

[0014] In some embodiments of the present application, the initial electrode is subjected to plasma treatment in a vacuum environment, with a plasma power of 1 kW to 3 kW and a processing time of 15 min to 30 min. In some embodiments of the present application, the initial electrode is subjected to plasma treatment in a vacuum environment, with a plasma power of 3 kW to 5 kW and a processing time of 1 min to 15 min. In some embodiments of the present application, the initial electrode is subjected to heat treatment in a vacuum or inert gas environment, with a heat treatment temperature of 200 °C to 250 °C and a heat treatment time of 180 min to 300 min. In some embodiments of the present application, the initial electrode is subjected to heat treatment in a vacuum or inert gas environment, with a heat treatment temperature of 250 °C to 350 °C and a heat treatment time of 5 min to 180 min.

[0015] The present application also proposes an electrochemical device, including an electrode; the electrode is any electrode in the present application, or the electrode is an electrode prepared by the preparation method of the present application. The present application proposes an electronic device, including the electrochemical device proposed in the present application.

[0016] An electrode proposed in the embodiments of the present application includes a current collector and an active material layer disposed on at least one surface of the current collector; under an inert atmosphere, thermogravimetric analysis is performed on the active material layer at a heating rate of 10 °C / min, and the results of the thermogravimetric analysis show that the mass change of the active material layer is 0% to 0.2% at 200 °C to 350 °C, which indicates that in the electrode proposed in the embodiments of the present application, the active material layer has good conductivity, which is beneficial to increasing the thickness of the active material layer without deteriorating the performance, thereby being beneficial to improving the energy density of the electrochemical device. Description of the Drawings

[0017] In conjunction with the accompanying drawings and with reference to the following specific embodiments, the above and other features, advantages, and aspects of the various embodiments of the present disclosure will become more apparent. Throughout the drawings, the same or similar reference numerals denote the same or similar elements. It should be understood that the drawings are schematic and the elements and elements are not necessarily drawn to scale.

[0018] Figure 1 It is a schematic diagram of an electrode according to an embodiment of the present disclosure. Specific embodiments

[0019] The following embodiments can enable those skilled in the art to understand the present application more comprehensively, but do not limit the present application in any way.

[0020] In order to improve the energy density of an electrochemical device, in some technologies, the energy density of the electrochemical device is improved by increasing the thickness of the active material layer in the electrode. However, increasing the thickness of the active material layer in the electrode may deteriorate the conductivity of the active material layer due to the excessive thickness of the active material layer. In order to improve the conductivity of the active material layer, in some technologies, a structure of multiple active material layers is adopted. However, the composite cold pressing process of multiple single-layer structures is complex, and it is impossible to avoid the change of the original compaction density and porosity of each single layer during the secondary cold pressing process, and the interface between layers is prone to film peeling due to poor bonding, which affects the conduction of electrons and ions and deteriorates the cycling performance. In other technologies, laser drilling is used for the active material layer. However, the efficiency of laser drilling is low, the cost is high, and the energy density is easily lost during the drilling process. In other technologies, a pore-forming agent solution is coated on the electrode surface, but this cannot avoid the dissolution of the electrode surface, and the depth of the pores formed by the pore-forming agent is limited, and the improvement of the side near the current collector is limited. The above technologies solve the ion transport from the electrolyte to the surface of the active material through different methods, but the ion transport from the surface of the active material to the inside of the active material layer remains unchanged, and the obstacle to ion transport still exists, and the improvement effect is not good.

[0021] Some embodiments of the present application provide an electrode that can improve the conductivity of the active material layer of the electrode, thereby facilitating the improvement of the energy density of the electrochemical device using the electrode. In some embodiments, the electrode may be an electrode sheet; the electrode includes a current collector and an active material layer located on one or both sides of the current collector; under an inert atmosphere, thermogravimetric analysis is performed on the active material layer at a heating rate of 10 °C / min, and the results of the thermogravimetric analysis show that the mass change of the active material layer is 0% to 0.2% at 200 °C to 350 °C.

[0022] In some embodiments, if the active material layer contains a high molecular compound with a low decomposition temperature (for example, a high molecular compound with a decomposition temperature below 350°C), such as a polymeric thickener, when performing thermogravimetric analysis in the range of 200°C to 350°C, a weight loss peak will be generated due to thermal decomposition. However, in the present application, the mass change of the active material layer at 200°C to 350°C is 0% to 0.2%. This indicates that the active material layer in the embodiments of the present application hardly contains high molecular compounds with a low decomposition temperature, which can avoid the influence of high molecular compounds with a low decomposition temperature in the active material layer on the conductivity of the active material layer, thereby improving the conduction performance of the active material layer for ions and electrons. Thus, when increasing the thickness of the active material layer to improve the energy density of the electrochemical device, due to the good conductivity of the active material layer, the electrical performance of the electrochemical device will not deteriorate due to the increase in the thickness of the active material layer. It can be seen that the electrode proposed in the embodiments of the present application, due to the good conductivity of the active material layer, is beneficial to improving the performance of the electrochemical device using the electrode and is beneficial to increasing the energy density.

[0023] In some embodiments of the present application, the results of thermogravimetric analysis show that the number of weight loss peaks of the active material layer at 200°C to 350°C is 0, which indicates that there are hardly any high molecular compounds with a low decomposition temperature in the embodiments of the present application. In some embodiments of the present application, the results of thermogravimetric analysis show that the number of weight loss peaks of the active material layer at 350°C to 800°C is not less than 1, which indicates that there are high molecular compounds with a high decomposition temperature (decomposed into high molecular compounds with a temperature of 350°C to 800°C) in the active material layer of the present application. This is because high molecular compounds are needed in the active material layer to bond the substances in the active material layer together and adhere between the current collectors.

[0024] In some embodiments of the present application, the results of thermogravimetric analysis show that the mass change of the active material layer at 350°C to 800°C is 0.21% to 13%. This indicates that the content of high molecular compounds with a high decomposition temperature is not zero, which is beneficial to ensuring the overall cohesion of the active material layer and the adhesion force with the current collector, and preventing excessive high molecular compounds from affecting the conductivity. Optionally, the results of thermogravimetric analysis show that the mass change of the active material layer at 350°C to 800°C is 0.77% to 3.4%, so as to balance the requirements of conductivity and adhesion force.

[0025] In some embodiments of the present application, the electrode is a negative electrode, such as the negative electrode of an electrochemical device. In some embodiments, the electrode is a negative electrode, the active material layer is the active material layer of the negative electrode, and the current collector is the current collector of the negative electrode. The current collector can be copper foil, aluminum foil, steel foil, etc., and no limitation is made thereto. In some embodiments, the compaction density ρ of the active material layer ≥ 0.6 g / cm 3, A higher compaction density indicates that the mass of the active material layer carried per unit volume of the electrode is larger. The more the mass of the active material layer, the more conducive it is to increasing the energy that can be stored per unit volume, thereby increasing the energy density. In some embodiments, the compaction density ρ of the active material layer satisfies: 1.85 g / cm 3 ≥ρ≥0.65 g / cm 3 , which is conducive to increasing the energy density. In some embodiments, by limiting the compaction density of the active material layer to be not less than 0.65 g / cm 3 , the energy density can be further ensured, while limiting the compaction density of the negative electrode active material layer to be not greater than 1.85 g / cm 3 can prevent the particles in the active material layer from breaking due to excessive compaction density, which increases the consumption of the electrolyte and deteriorates the cycle performance. Optionally, 1.83 g / cm 3 ≥ρ≥1.0 g / cm 3 .

[0026] In some embodiments, the thickness h of the active material layer on one side of the current collector satisfies h≥10 μm. In some embodiments, a thicker active material layer is conducive to increasing the proportion of the active material layer, thereby increasing the energy density. In some embodiments of the present application, the thickness h of the active material layer on one side of the current collector satisfies: 1500 μm≥h≥15 μm. By limiting the thickness of the active material layer to be not less than 15 μm, the thickness of the negative electrode active material layer can be ensured, thereby increasing the energy density. By limiting the thickness of the negative electrode active material layer to be not greater than 1500 μm, the problem that the negative electrode active material layer may detach from the current collector due to excessive thickness can be prevented. Optionally, 150 μm≥h≥30 μm.

[0027] In some embodiments, the adhesion force F between the active material layer and the current collector satisfies: 300 N / m≥F≥0.5 N / m. If the adhesion force between the active material layer and the current collector is too small, it may cause the active material layer to detach from the current collector, thereby deteriorating the conductivity. If the adhesion force between the active material layer and the current collector is too large, it will increase the demand for the binder and is also not conducive to the conductivity. Optionally, the adhesion force F between the active material layer and the current collector satisfies: 150 N / m≥F≥1 N / m. Optionally, 20 N / m≥F≥1 N / m.

[0028] In some embodiments, the resistivity of the active material layer is from 0.01 Ω·cm to 50 Ω·cm, which indicates that the negative electrode active material layer of the application has good conductivity and is conducive to the electrical performance. In some embodiments, the negative electrode active material layer includes a negative electrode material, and the negative electrode material includes at least one of lithium titanate, silicon monoxide, graphite, silicon, or hard carbon. The negative electrode material can be, for example, a combination of at least two of the above materials.

[0029] In some embodiments of the present application, the active material layer includes a conductive agent, and the conductive agent includes at least one of carbon nanotubes, carbon fibers, acetylene black, graphene, Ketjen black, or conductive carbon black. The conductive agent can increase the conductivity of the active material layer. Among them, the carbon nanotubes can be single-walled carbon nanotubes or multi-walled carbon nanotubes. Single-walled carbon nanotubes can increase long-range electron conduction, while reducing the coating area of the binder on the active material, reducing the ion transport resistance, and improving the kinetic performance. In some embodiments, the active material layer includes a conductive agent. Based on the total mass of the active material layer, the mass percentage of the conductive agent in the active material layer is 0% to 2%. In some embodiments, the mass percentage of the conductive agent in the active material layer in the embodiments of the present application can be 0%. This is because in the embodiments of the present application, the active material layer does not have high molecular compounds with low decomposition temperatures. High molecular compounds with low decomposition temperatures can be from the binder and / or thickener in the electrode, and it already has good conductivity. Therefore, the conductive agent can be not added, and the mass percentage of the conductive agent is limited to not higher than 2%, so as to avoid the capacity decline of the active material layer caused by too high a content of the conductive agent.

[0030] In some embodiments of the present application, the active material layer includes a high molecular compound, and the high molecular compound includes at least one of polyethylene oxide, polypropylene oxide, polyvinylidene fluoride, polytetrafluoroethylene, polyacrylonitrile, polyimide, polysiloxane, polyacrylic acid, polypropylene derivatives, sodium carboxymethyl cellulose, lithium carboxymethyl cellulose, poly-N-methylpyrrolidone, polyvinylpyrrolidone, styrene acrylate, or styrene-butadiene rubber. The high molecular compound can be at least one of a binder or a thickener.

[0031] In some embodiments of the present application, the active material layer includes a high molecular compound. Based on the total mass of the active material layer, the mass percentage of the high molecular compound in the active material layer is 0.22% to 14%. If the mass percentage of the high molecular compound is too low, it may lead to insufficient adhesion between the active material layer and the current collector. If the mass percentage of the high molecular compound is too high, it may affect the conductivity of the active material layer. Optionally, the mass percentage of the high molecular compound in the active material layer is 0.8% to 3.5%.

[0032] In some embodiments of the present application, the high molecular compound (which can be a binder) is distributed in a dot-like or surface-like manner on the surface of the active material (such as the negative electrode material) of the active material layer, and aggregates on the surface of the active material or between the particles of the active material. There is a lot of exposure of the active material, and the hindrance to electron and ion transport is small, which is beneficial to ensuring conductivity.

[0033] In some embodiments, please refer to Figure 1, the electrode includes a current collector 10 and an active material layer. The active material layer includes an active material 20, a conductive agent 30, and a binder 40. The conductive agent may include a zero-dimensional conductive agent, a one-dimensional conductive agent, and a two-dimensional conductive agent. The binder 40 may include a first binder and a second binder. Among them, by using conductive agents of different dimensions, the gaps between the active materials can be fully filled, thereby improving the overall conductivity.

[0034] In some embodiments of the present application, a method for preparing an electrode is proposed, which can be used to manufacture any electrode of the present application, including: coating a slurry of the active material layer on at least one surface of the current collector, drying, and cold pressing to obtain an initial electrode; processing the initial electrode to obtain an electrode; wherein, processing the initial electrode includes: performing plasma treatment on the initial electrode in a vacuum environment, with a plasma power of 0.5 kW to 5 kW, the gas source including at least one of nitrogen, argon, or carbon tetrafluoride, a gas flow rate of 3000 sccm to 5000 sccm, a temperature of 20 °C to 60 °C, and a processing time of 1 min to 60 min; or, performing heat treatment on the initial electrode in a vacuum or inert gas environment, with a heat treatment temperature of 200 °C to 400 °C and a heat treatment time of not less than 5 min; or, performing laser bombardment on the initial electrode in a vacuum or inert gas environment, with a laser intensity of 25 W to 30 W and a processing time of 1 s to 600 s.

[0035] In the method for preparing an electrode proposed in the embodiments of the present application, by processing the initial electrode, high-molecular compounds with a low decomposition temperature in the active material layer can be removed, which is beneficial to improving the conductivity of the electrochemical device and further beneficial to improving the energy density. In some embodiments of the present application, the active material layer of the electrode includes an active material, a conductive agent, and a binder, and does not contain high-molecular compounds with a low decomposition temperature (such as high-molecular binders and / or thickeners with a low decomposition temperature), avoiding the hindrance of high-molecular compounds to the transmission of electrons and ions.

[0036] In some embodiments of the present application, plasma treatment is performed on the initial electrode in a vacuum environment, with a plasma power of 1 kW to 3 kW and a processing time of 15 min to 30 min. By increasing the plasma power, the processing time can be reduced. In other embodiments of the present application, plasma treatment is performed on the initial electrode in a vacuum environment, with a plasma power of 3 kW to 5 kW and a processing time of 1 min to 15 min.

[0037] In some embodiments of the present application, the initial electrode is heat-treated in a vacuum or inert gas environment, with the heat treatment temperature ranging from 200°C to 250°C and the heat treatment time ranging from 180 min to 300 min. In other embodiments of the present application, the initial electrode is heat-treated in a vacuum or inert gas environment, with the heat treatment temperature ranging from 250°C to 350°C and the heat treatment time ranging from 5 min to 180 min. The heat treatment time for the initial electrode is related to the heat treatment temperature. Increasing the heat treatment temperature can reduce the heat treatment time, and extending the heat treatment time can lower the heat treatment temperature.

[0038] In some embodiments of the electrochemical device of the present application, it includes an electrode; the electrode is the electrode of any one of the present application; or, the electrode is an electrode prepared by the preparation method proposed in the present application. In some embodiments, the electrochemical device includes a positive electrode, a negative electrode, and a separator disposed between the positive electrode and the negative electrode. In some embodiments, the negative electrode can be any of the above electrodes. In some embodiments, the current collector of the positive electrode can use Al foil. Of course, other current collectors commonly used in the art can also be used.

[0039] In some embodiments, the separator includes at least one of polyethylene, polypropylene, polyvinylidene fluoride, polyethylene terephthalate, polyimide, or aramid. For example, polyethylene includes at least one selected from high-density polyethylene, low-density polyethylene, or ultra-high molecular weight polyethylene. In particular, polyethylene and polypropylene have a good effect on preventing short circuits and can improve the stability of the battery through the shut-off effect. In some embodiments, the thickness of the separator is in the range of about 5 μm to 50 μm.

[0040] In some embodiments, the surface of the separator may further include a porous layer. The porous layer is disposed on at least one surface of the separator. The porous layer includes inorganic particles and a binder. The inorganic particles are selected from at least one of aluminum oxide (Al2O3), silicon dioxide (SiO2), magnesium oxide (MgO), titanium dioxide (TiO2), hafnium dioxide (HfO2), tin dioxide (SnO2), cerium dioxide (CeO2), nickel oxide (NiO), zinc oxide (ZnO), calcium oxide (CaO), zirconium oxide (ZrO2), yttrium oxide (Y2O3), silicon carbide (SiC), boehmite, aluminum hydroxide, magnesium hydroxide, calcium hydroxide, or barium sulfate. In some embodiments, the pores of the separator have a diameter in the range of about 0.01 μm to 1 μm. The binder of the porous layer is selected from at least one of polyvinylidene fluoride, copolymer of vinylidene fluoride-hexafluoropropylene, polyamide, polyacrylonitrile, polyacrylate, polyacrylic acid, polyacrylate salt, sodium carboxymethyl cellulose, polyvinylpyrrolidone, polyethylene ether, polymethyl methacrylate, polytetrafluoroethylene, or polyhexafluoropropylene. The porous layer on the surface of the separator can improve the heat resistance, antioxidant property, and electrolyte infiltration property of the separator, and enhance the adhesion between the separator and the electrode sheet.

[0041] In some embodiments of the present application, the electrochemical device may be wound or stacked. In some embodiments, the positive electrode and / or negative electrode of the electrochemical device may be a multi-layer structure formed by winding or stacking, or may be a single-layer structure formed by stacking a single positive electrode, a separator, and a single negative electrode.

[0042] In some embodiments, the electrochemical device includes a lithium-ion battery, but the present application is not limited thereto. In some embodiments, the electrochemical device may further include an electrolyte. The electrolyte may be one or more of a gel electrolyte, a solid electrolyte, and an electrolytic solution, and the electrolytic solution includes a lithium salt and a non-aqueous solvent. The lithium salt is selected from one or more of LiPF6, LiBF4, LiAsF6, LiClO4, LiB(C6H5)4, LiCH3SO3, LiCF3SO3, LiN(SO2CF3)2, LiC(SO2CF3)3, LiSiF6, LiBOB, or lithium difluoroborate. For example, LiPF6 is selected as the lithium salt because it has high ionic conductivity and can improve the cycling performance.

[0043] The non-aqueous solvent may be a carbonate compound, a carboxylate compound, an ether compound, other organic solvents, or a combination thereof. The carbonate compound may be a linear carbonate compound, a cyclic carbonate compound, a fluorinated carbonate compound, or a combination thereof.

[0044] Examples of the linear carbonate compound are diethyl carbonate (DEC), dimethyl carbonate (DMC), dipropyl carbonate (DPC), methyl propyl carbonate (MPC), ethyl propyl carbonate (EPC), methyl ethyl carbonate (MEC), and combinations thereof. Examples of the cyclic carbonate compound are ethylene carbonate (EC), propylene carbonate (PC), butylene carbonate (BC), vinylene ethylene carbonate (VEC), or combinations thereof. Examples of the fluorinated carbonate compound are fluoroethylene carbonate (FEC), 1,2-difluoroethylene carbonate, 1,1-difluoroethylene carbonate, 1,1,2-trifluoroethylene carbonate, 1,1,2,2-tetrafluoroethylene carbonate, 1-fluoro-2-methylethylene carbonate, 1-fluoro-1-methylethylene carbonate, 1,2-difluoro-1-methylethylene carbonate, 1,1,2-trifluoro-2-methylethylene carbonate, trifluoromethyl ethylene carbonate, or combinations thereof.

[0045] Examples of the carboxylate compound are methyl acetate, ethyl acetate, n-propyl acetate, tert-butyl acetate, methyl propionate, ethyl propionate, propyl propionate, γ-butyrolactone, decanolide, valerolactone, mevalonolactone, caprolactone, methyl formate, or combinations thereof.

[0046] Examples of the ether compound are dibutyl ether, tetraethylene glycol dimethyl ether, diethylene glycol dimethyl ether, 1,2-dimethoxyethane, 1,2-diethoxyethane, ethoxymethoxyethane, 2-methyltetrahydrofuran, tetrahydrofuran, or a combination thereof.

[0047] Examples of other organic solvents are dimethyl sulfoxide, 1,2-dioxolane, sulfolane, methylsulfolane, 1,3-dimethyl-2-imidazolidinone, N-methyl-2-pyrrolidone, formamide, dimethylformamide, acetonitrile, trimethyl phosphate, triethyl phosphate, trioctyl phosphate, and phosphate esters, or a combination thereof.

[0048] In some embodiments of the present application, taking a lithium-ion battery as an example, a positive electrode, a separator, and a negative electrode are wound or stacked in sequence to form an electrode assembly, and then the electrode assembly is encapsulated in, for example, an aluminum plastic film, an electrolyte is injected, formed, and encapsulated to make a lithium-ion battery. Then, the performance of the prepared lithium-ion battery is tested.

[0049] Those skilled in the art will understand that the preparation methods of the above-described electrochemical devices (e.g., lithium-ion batteries) are only examples. Other methods commonly used in the art can be adopted without departing from the content disclosed in the present application.

[0050] The present application provides an electronic device, including an electrochemical device; the electrochemical device is the electrochemical device of any one of the present application. The electronic device of the embodiments of the present application is not particularly limited, and it can be any electronic device known in the prior art. In some embodiments, the electronic device may include, but is not limited to, a notebook computer, a pen-input computer, a mobile computer, an e-book player, a portable phone, a portable fax machine, a portable copier, a portable printer, a head-mounted stereo headset, a video recorder, a liquid crystal TV, a portable cleaner, a portable CD player, a mini-disc, a transceiver, an electronic notepad, a calculator, a memory card, a portable recorder, a radio, a backup power supply, a motor, an automobile, a motorcycle, a moped, a bicycle, a drone, a lighting fixture, a toy, a game console, a clock, a power tool, a flash, a camera, or a large household battery, etc.

[0051] Some specific examples and comparative examples are listed below to better illustrate the present application, where a lithium-ion battery is used as an example.

[0052] Example 1

[0053] Preparation of the positive electrode sheet: The positive electrode material lithium cobaltate, polyvinylidene fluoride (PVDF), and the conductive agent carbon nanotubes (CNT) are mixed in a mass ratio of 97.5:1:4.5, using N-methylpyrrolidone (NMP) as a solvent to prepare a slurry, and the slurry is stirred evenly to form a slurry of the positive electrode active material layer. The slurry is uniformly coated on the positive electrode current collector aluminum foil, and after drying, the positive electrode sheet is obtained.

[0054] Preparation of the negative electrode plate: Graphite as the negative electrode material, styrene acrylate as the binder, styrene butadiene rubber as the binder, carbon nanotubes as the conductive agent, and sodium carboxymethyl cellulose as the thickener are mixed in a mass ratio of 98.56:0.62:0.62:0.2:1. Using deionized water as the solvent, a slurry for the negative electrode active material layer is formed. Copper foil is used as the negative electrode current collector, and the slurry of the negative electrode active material layer is coated on the negative electrode current collector and dried at 90 °C. The dried electrode plate is heat-treated at a temperature of 360 °C for a heat treatment time of 10 min, and the negative electrode plate is obtained after the heat treatment.

[0055] Preparation of the separator: The separator is polyethylene (PE) with a thickness of 8 μm.

[0056] Preparation of the electrolyte: In an environment with a water content of less than 10 ppm, lithium hexafluorophosphate and a non-aqueous organic solvent (ethylene carbonate (EC): diethyl carbonate (DEC): propylene carbonate (PC): propyl propionate (PP): vinylene carbonate (VC) = 20:30:20:28:2, weight ratio) are formulated in a weight ratio of 8:92 to form the electrolyte.

[0057] Preparation of the lithium-ion battery: The positive electrode plate, the separator, and the negative electrode plate are stacked in sequence, with the separator placed in the middle of the positive electrode plate and the negative electrode plate to play a role in isolation, and then wound to obtain an electrode assembly. The electrode assembly is placed in an outer packaging aluminum-plastic film, dehydrated at 80 °C, then the above-mentioned electrolyte is injected and encapsulated, and after processes such as formation, degassing, and edge trimming, the lithium-ion battery is obtained.

[0058] The relevant parameters of Example 1 are as follows: The negative electrode active material layer includes graphite, styrene acrylate, styrene butadiene rubber, and CNT. The mass percentages of graphite, styrene acrylate, styrene butadiene rubber, and CNT are 98.56%, 0.62%, 0.62%, and 0.2% respectively. The binder of the negative electrode active material is styrene acrylate and styrene butadiene rubber with a mass ratio of 1:1. The mass content of the polymer compound in the negative electrode active material layer is 1.24%, and the compaction density of the negative electrode active material layer is 1.75 g / cm 3, the thickness of the active material layer on one side of the current collector of the negative electrode is 75 μm, the adhesion between the active material layer of the negative electrode and the current collector is 11 N / m, the resistivity of the active material layer of the negative electrode is 0.1 Ω·cm, the negative electrode material is graphite, the conductive agent is carbon nanotube (CNT), the mass percentage content of the conductive agent in the active material layer of the negative electrode is 0.2%, the number of weight loss peaks of the active material layer of the negative electrode at 200°C to 350°C is 0, the mass change at 200°C to 350°C is 0.10%, the number of weight loss peaks at 350°C to 800°C is 2, and the mass change at 350°C to 800°C is 1.25%. The positive electrode active material layer includes lithium cobaltate, PVDF, and CNT. Among them, the mass percentage contents of lithium cobaltate, PVDF, and CNT are 97.5%, 1%, and 1.5%, respectively. The thickness of one side of the positive electrode is 63 microns, and the tap density is 4.12 g / cm 3 .

[0059] Other embodiments are based on the steps of Embodiment 1 with parameter changes. The specific changed parameters are shown in the following table. In each embodiment, the same amount of sodium carboxymethyl cellulose is added to the slurry of the negative electrode active material layer and then removed by heat treatment.

[0060] Comparative Example 1

[0061] Preparation of the negative electrode sheet: Mix the negative electrode material graphite, the binder styrene acrylate, and the thickener sodium carboxymethyl cellulose in a mass ratio of 97:2:1.0, use deionized water as the solvent to form a slurry of the negative electrode active material layer, use copper foil as the negative electrode current collector, coat the slurry of the negative electrode active material layer on the negative electrode current collector, and dry it at 90°C to obtain the negative electrode sheet.

[0062] The remaining preparation steps of Comparative Example 1 are the same as those of Embodiment 1. The parameter differences between Comparative Example 1 and Embodiment 1 are shown in the table below.

[0063] Comparative Example 2

[0064] Preparation of the negative electrode sheet: Mix the negative electrode material graphite, the conductive agent carbon nanotube, the binder styrene butadiene rubber, and the thickener sodium carboxymethyl cellulose in a mass ratio of 97.2:0.3:1.5:1.0, use deionized water as the solvent to form a slurry of the negative electrode active material layer, use copper foil as the negative electrode current collector, coat the slurry of the negative electrode active material layer on the negative electrode current collector, and dry it at 90°C to obtain the negative electrode sheet.

[0065] The remaining preparation steps of Comparative Example 2 are the same as those of Embodiment 1. The parameter differences between Comparative Example 2 and Embodiment 1 are shown in the table below.

[0066] Comparative Example 3

[0067] Preparation of the negative electrode sheet: The negative electrode material graphite, the conductive agent carbon nanotubes, the binder polyacrylate, and the thickener sodium carboxymethyl cellulose were mixed according to a mass ratio of 94.9:0.1:4:1.0. Using deionized water as a solvent, a slurry for the negative electrode active material layer was formed. Copper foil was used as the negative electrode current collector, and the slurry of the negative electrode active material layer was coated on the negative electrode current collector and dried at 90 °C to obtain the negative electrode sheet.

[0068] The remaining preparation steps of Comparative Example 3 were the same as those of Example 1. The parameter differences between Comparative Example 3 and Example 1 are shown in the following table.

[0069] The test methods of the present application are described below.

[0070] 1. Thermogravimetric test

[0071] The battery was discharged to 3.0 V, and the battery was disassembled to obtain the negative electrode sheet. The negative electrode sheet was soaked in DMC (dimethyl carbonate) for 12 to 24 hours, and then the DMC was replaced and the negative electrode sheet was soaked for another 12 to 24 hours, and dried at 80 °C to 100 °C. The active material layer powder at the corresponding position was scraped from the surface of the negative electrode sheet for testing. Thermogravimetric analysis was used to measure the active material layer of the negative electrode of the prepared lithium-ion battery, and the mass change and the number of weight loss peaks during the thermogravimetric analysis were tested. The test range was 200 °C to 350 °C and 350 °C to 800 °C, the heating rate was 10 °C / min, and the test atmosphere was an inert atmosphere.

[0072] 2. Resistivity test

[0073] A resistance tester was used to test the resistivity of the active material layer. The upper and lower plane controllable pressure probes were used to directly measure the negative electrode sheet. An alternating current was applied to the test positive electrode sheet or negative electrode sheet, and a certain pressure (0.35 T) was applied to the test active material layer at the same time to obtain the overall resistance in the thickness direction of the negative electrode sheet. At the same time, the area (A) and thickness (l) of the tested negative electrode sheet were collected, and the resistivity of the tested negative electrode sheet was deduced according to the resistivity calculation formula (ρ = R * A / l). 3. Alternating current resistance test

[0074] An alternating current with a small current of 1 kHz was applied to the positive and negative electrodes of the battery, and the alternating current resistance value of the battery was obtained by measuring the voltage response.

[0075] 4. 25 °C direct current resistance DCR test

[0076] At 25 °C, the lithium-ion battery is charged at a constant current of 0.5C to 4.45V, and then charged at a constant voltage to 0.05C; it is left standing for 30 min; it is discharged at 0.1C for 3 h until the state of charge of the battery is 70% SOC (record the corresponding discharge end voltage value U1), and it is discharged at 1C for 1 s (record the corresponding discharge end voltage value U2). Among them, "1C" is the current value that completely discharges the battery capacity within 1 hour. The DCR of the battery at 70% SOC is calculated according to the following formula: DCR = (U1 - U2) / (1C - 0.1C).

[0077] 5. Test of rate performance

[0078] In an environment of 25 °C, the battery is discharged at a constant current to 3V, and the first charge and discharge are carried out. The constant current charging is carried out at a charging current of 0.7C until the upper limit voltage is 4.48V, and then the constant voltage charging is carried out to 0.05C. Then, the constant current discharge is carried out at a discharge current of 0.2C until the final voltage is 3V. At this time, the discharge capacity at 0.2C is recorded. Then, the battery is repeatedly charged at a charging current of 0.7C until the upper limit voltage is 4.48V, and then the constant voltage charging is carried out to 0.05C. Then, the discharge rate is set to 3C for constant current discharge until the final voltage is 3V. At this time, the discharge capacity at 3C is recorded.

[0079] Retention rate of 3C discharge capacity = (3C discharge capacity / discharge capacity at 0.2C) × 100%

[0080] 6. Test of cycle performance

[0081] Charge at a rate of 0.5C to 4.2V, change to constant voltage charging at 4.21V until the current drops to 0.025C. After standing for 5 minutes, discharge at a rate of 0.5C to 3.0V, which completes one cycle. Record the discharge capacity as the capacity of the lithium-ion battery. Repeat 1000 cycles and record the discharge capacity as the remaining capacity of the lithium-ion battery. Retention rate of 1000-cycle capacity = remaining capacity / initial capacity × 100%.

[0082] Table 1

[0083]

[0084]

[0085]

[0086] Note: In the tables of this application, the active material layer is the active material layer of the negative electrode, the adhesion force is the adhesion force between the active material layer of the negative electrode and the current collector, and the contents in the tables are all mass percentages. The parameters not shown in the examples and comparative examples in Table 1 are the same as those in Example 1.

[0087] Please refer to Table 1, which shows the preparation parameters and performance test results of Examples 1 to 9 and Comparative Examples 1 to 3. The preparation parameters not shown in Table 1 are the same. It can be seen from Table 1 that the mass change of the negative electrode active material layer in Examples 1 to 9 is 0% to 0.2% at 200°C to 350°C, the number of weight loss peaks of the negative electrode active material layer at 200°C to 350°C is 0, and the number of weight loss peaks at 350°C to 800°C is not 0. In Comparative Examples 1 to 9, the mass change of the negative electrode active material layer at 200°C to 350°C is greater than 0.2%, the number of weight loss peaks of the negative electrode active layer at 200°C to 350°C is not 0, and the number of weight loss peaks at 350°C to 800°C is also not 0. It can be seen from Table 1 that the AC resistance and DC resistance of the lithium-ion batteries in Examples 1 to 9 are significantly smaller than those in Comparative Examples 1 to 3, and the capacity retention rate after 3C rate discharge in Examples 1 to 9 is significantly higher than that in Comparative Examples 1 to 3. From the above data, it can be seen that when the active material layer is subjected to thermogravimetric analysis at 200°C to 350°C, when the mass change of the negative electrode active material layer at 200°C to 350°C is 0% to 0.2%, the conductivity of the active material layer can be improved, thereby reducing the resistance of the electrochemical device, which is beneficial to improving the rate performance. This is because the negative electrode active material layer in Examples 1 to 9 was heat-treated to remove high molecular compounds with low decomposition temperatures, thereby improving the conductivity. Therefore, the lithium-ion batteries all have good conductivity and rate performance.

[0088] As shown in Comparative Examples 1 to 3, as the mass change during the thermogravimetric analysis process at 200°C to 350°C increases, the AC resistance and DC resistance of the lithium-ion battery increase. This may be because the mass change during the thermogravimetric process at 200°C to 350°C reflects the content of high molecular compounds with low decomposition temperatures, and an increase in the content of high molecular compounds with low decomposition temperatures is not conducive to the conductivity of the lithium-ion battery.

[0089] As shown in Examples 1 to 4, the number of weight loss peaks of the negative electrode active material layer at 350°C to 800°C is related to the type of binder, and one type of binder corresponds to one weight loss peak. When the binder is styrene acrylate, the AC resistance and DC resistance are the smallest, and the 3C discharge capacity retention rate is the highest.

[0090] As shown in Examples 5 to 9, as the mass change during thermogravimetric analysis at 350°C to 800°C increases for the negative electrode active material layer, the conductivity of the lithium-ion battery begins to decrease, and the 3C discharge capacity retention rate slightly decreases. This may be because the mass change during the thermogravimetric process from 350°C to 800°C reflects the content of high decomposition temperature polymer binders. An increase in the content of the binder is not conducive to the conductivity and discharge performance of the lithium-ion battery. The higher the mass percentage content of the binder, the greater the binding force, but the higher the AC resistance and DC resistance, and it also affects the 3C discharge capacity retention rate. However, if the binding force is too small, it may cause separation between the negative electrode active material layer and the current collector.

[0091] Table 2

[0092]

[0093]

[0094] The parameter differences between Examples 7, 10 to 17 and Example 1 are only the data shown in Table 2, and the parameters not shown are the same as those in Example 1.

[0095] As shown in Examples 10, 11, 7, 12 to 13, as the compaction density of the negative electrode active material layer increases, the binding force increases, the resistivity decreases, the AC resistance gradually decreases, the DC resistance first increases and then decreases, the 3C discharge capacity retention rate first decreases and then increases, and the 1000-cycle capacity retention rate first decreases and then increases. This may be because the increase in compaction density reduces the distance for ion and electron transport between particles, thereby improving conductivity and reducing resistance. However, when the compaction density is too large, it may lead to insufficient electrolyte infiltration, which may be unfavorable for the performance of the lithium-ion battery.

[0096] As shown in Examples 14, 15, 7, 16 to 17, as the thickness of the active material layer on one side of the negative electrode current collector increases, the binding force of the lithium-ion battery decreases, the AC resistance and DC resistance increase, and the 3C discharge capacity retention rate and the 1000-cycle capacity retention rate decrease. This may be because the increase in the thickness of the negative electrode active material layer leads to an increase in the path for ion and electron transport, so it is not conducive to conductivity and deteriorates the kinetic performance. However, if the thickness of the negative electrode active material layer is too small, the capacity that the negative electrode can store will be reduced, which is not conducive to the energy density. Therefore, the balance between the performance and capacity density of the lithium-ion battery is considered.

[0097] Table 3

[0098]

[0099]

[0100] The parameter differences between Examples 18 to 28 and Example 1 are only the data shown in Table 3, and the parameters not shown are the same as those in Example 1.

[0101] As shown in Examples 18 to 22, when the negative electrode material is silicon monoxide, lithium titanate, graphite, silicon, or hard carbon, the lithium-ion battery has relatively balanced performance. Among them, when the negative electrode material is hard carbon, the performance is the best, but the tap density is relatively low. When the negative electrode material is graphite, the comprehensive performance is the best.

[0102] As shown in Examples 23 to 27, when the conductive agent is conductive carbon black, acetylene black, Ketjen black, carbon nanotubes, graphene, or carbon fiber, the lithium-ion battery has relatively low resistivity, AC resistance, and DC resistance, and the 3C discharge capacity retention rate is relatively high. It can be seen that when the conductive agent includes the above materials, the performance requirements of the lithium-ion battery can be met.

[0103] As shown in Examples 7, 20, and 28, by adjusting the content of carbon nanotubes in the active material layer, the resistivity of the active material layer of the negative electrode is adjusted. As the amount of the conductive agent in the active material layer of the negative electrode increases, the resistivity decreases, the AC resistance and DC resistance of the lithium-ion battery both decrease, and the 3C discharge capacity retention rate increases. This is because the improvement of the resistivity of the active material layer improves the conductivity of the lithium-ion battery and enhances the performance of the lithium-ion battery. However, too much conductive agent may lead to a decrease in energy density.

[0104] The above description is only the preferred embodiments of the present application and the description of the applied technical principles. Those skilled in the art should understand that the disclosed scope of the present application is not limited to the technical solutions formed by the specific combination of the above technical features, but also covers other technical solutions formed by any combination of the above technical features or their equivalent features. For example, the technical solutions formed by mutually replacing the above features with the technical features having similar functions disclosed in the present application.

Claims

1. An electrode, characterized in that, Comprising: a current collector and an active material layer provided on at least one surface of the current collector; under an inert atmosphere, performing thermogravimetric analysis on the active material layer at a heating rate of 10 °C / min, the result of the thermogravimetric analysis shows that the mass change of the active material layer is 0% to 0.2% at 200 °C to 350 °C, the result of the thermogravimetric analysis shows that the number of weight loss peaks of the active material layer is not less than 1 at 350 °C to 800 °C, and the result of the thermogravimetric analysis shows that the mass change of the active material layer is 0.21% to 13% at 350 °C to 800 °C.

2. The electrode according to claim 1, characterized in that, The result of the thermogravimetric analysis shows that the number of weight loss peaks of the active material layer is 0 at 200 °C to 350 °C.

3. The electrode according to claim 1, characterized in that, The result of the thermogravimetric analysis shows that the mass change of the active material layer is 0.77% to 3.4% at 350 °C to 800 °C.

4. The electrode according to claim 1, characterized in that, The electrode is a negative electrode.

5. The electrode according to claim 4, characterized in that, The electrode satisfies at least one of the following conditions: (a) The compaction density ρ of the active material layer ≥ 0.6 g / cm 3 ; (b) The thickness h of the active material layer on one side of the current collector satisfies h≥10 μm; (c) The adhesion force F between the active material layer and the current collector satisfies: 300 N / m≥F≥0.5 N / m; (d) The resistivity of the active material layer is 0.01 Ω·cm to 50 Ω·cm; (e) The active material layer includes a negative electrode material, and the negative electrode material includes at least one of lithium titanate, silicon monoxide, graphite, silicon, or hard carbon.

6. The electrode according to claim 4, characterized in that, The electrode satisfies at least one of the following conditions: (f) The compaction density ρ of the active material layer satisfies: 1.85 g / cm 3 ≥ ρ ≥ 0.65 g / cm 3 ; (g) The thickness h of the active material layer on one side of the current collector satisfies: 1500 μm≥h≥15 μm; (h) The adhesion force F between the active material layer and the current collector satisfies: 150 N / m≥F≥1 N / m.

7. The electrode according to claim 4, characterized in that, The electrode satisfies at least one of the following conditions: (i) The compaction density ρ of the active material layer satisfies: 1.83 g / cm 3 ≥ ρ ≥ 1.0 g / cm 3 ; (j) The thickness h of the active material layer on one side of the current collector satisfies: 150 μm≥h≥30 μm; (k) The adhesion force F between the active material layer and the current collector satisfies: 20 N / m≥F≥1 N / m.

8. The electrode according to claim 1, characterized in that, The active material layer includes a conductive agent, and the conductive agent includes at least one of carbon nanotubes, carbon fibers, acetylene black, graphene, Ketjen black, or conductive carbon black.

9. The electrode according to claim 1, characterized in that, The active material layer includes a conductive agent, and based on the total mass of the active material layer, the mass percentage content of the conductive agent in the active material layer is 0% to 2%.

10. The electrode according to claim 1, characterized in that, The active material layer includes a polymer compound, and the polymer compound includes at least one of polyethylene oxide, polypropylene oxide, polyvinylidene fluoride, polytetrafluoroethylene, polyacrylonitrile, polyimide, polysiloxane, polyacrylic acid, polypropylene derivatives, sodium carboxymethyl cellulose, lithium carboxymethyl cellulose, polymethylpyrrolidone, polyvinylpyrrolidone, styrene acrylate, or styrene-butadiene rubber.

11. The electrode according to claim 1, characterized in that, The active material layer includes a polymer compound, and based on the total mass of the active material layer, the mass percentage content of the polymer compound in the active material layer is 0.22% to 14%.

12. The electrode according to claim 1, characterized in that, The active material layer includes a polymer compound. Based on the total mass of the active material layer, the mass percentage of the polymer compound in the active material layer is 0.8% to 3.5%.

13. A method for preparing the electrode according to any one of claims 1 to 12, characterized in that, Comprising: Coating a slurry of the active material layer on at least one surface of a current collector, drying, and cold pressing to obtain an initial electrode, wherein the active material layer of the initial electrode includes a polymer compound with a high decomposition temperature having a decomposition temperature of 350°C to 800°C; Processing the initial electrode and ensuring that the active material layer contains the polymer compound with the high decomposition temperature after processing to obtain the electrode; Wherein, processing the initial electrode includes: Performing plasma treatment on the initial electrode in a vacuum environment, with a plasma power of 0.5 kW to 5 kW, the gas source including at least one of nitrogen, argon, or carbon tetrafluoride, a gas flow rate of 3000 sccm to 5000 sccm, a temperature of 20°C to 60°C, and a processing time of 1 min to 60 min; Or, Performing heat treatment on the initial electrode in a vacuum or inert gas environment, with a heat treatment temperature of 200°C to 400°C and a heat treatment time of not less than 5 min; Or, Performing laser bombardment on the initial electrode in a vacuum or inert gas environment, with a laser intensity of 25 W to 30 W and a processing time of 1 s to 600 s.

14. The preparation method according to claim 13, wherein, Performing plasma treatment on the initial electrode in a vacuum environment, with a plasma power of 1 kW to 3 kW and a processing time of 15 min to 30 min; Or, Performing plasma treatment on the initial electrode in a vacuum environment, with a plasma power of 3 kW to 5 kW and a processing time of 1 min to 15 min.

15. The preparation method according to claim 13, wherein, Performing heat treatment on the initial electrode in a vacuum or inert gas environment, with a heat treatment temperature of 200°C to 250°C and a heat treatment time of 180 min to 300 min; or, Performing heat treatment on the initial electrode in a vacuum or inert gas environment, with a heat treatment temperature of 250°C to 350°C and a heat treatment time of 5 min to 180 min.

16. An electrochemical device, wherein, Comprising an electrode; The electrode is the electrode according to any one of claims 1 to 12, or, The electrode is an electrode prepared by using the preparation method according to any one of claims 13 to 15.

17. An electronic device, wherein, Comprising the electrochemical device according to claim 16.

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