Positive functional electrode, electrode preparation method and battery

Abstract

The embodiment of the invention provides a positive functional electrode, an electrode preparation method and a battery, and the electrode preparation method comprises the following steps: mixing a first phosphate material and a conductive agent according to a first preset proportion to obtain a first mixed solution, adding a first preset solvent into the first mixed solution to form a first conductive slurry, adding a first adhesive into the first conductive slurry to form a PTC effect coating; mixing a second phosphate material and a conductive agent according to a preset second preset proportion to obtain a second mixed solution; adding a second preset solvent into the second mixed solution to form second conductive slurry, and adding a second adhesive into the second conductive slurry to form an active material; a current collector is coated with a PTC effect coating and an active material in sequence in a layered coating mode, so that the positive functional electrode is prepared. The positive functional electrode provided by the invention can optimize the safety performance of the battery without causing loss of electrical properties such as energy density and the like.

Description

Technical Field

[0001] The present application relates to the technical field of batteries, and particularly to a positive functional electrode, a method for preparing an electrode, and a battery. Background Art

[0002] With the rapid development of lithium-ion battery technology, higher requirements are put forward for the power performance, rate performance, safety performance, etc. of the battery. In order to improve the safety of lithium-ion batteries and reduce the risk of thermal runaway, a positive temperature coefficient (PTC) resistance element can usually be used outside the battery or a PTC material (such as various polymers like polyethylene, polymethyl methacrylate, etc.) can be introduced inside. When the battery temperature rises, the PTC effect is excited to destroy the electronic conduction network, increase the internal resistance, and prevent the occurrence of thermal runaway. However, the additional introduction of PTC materials will cause losses in electrical properties such as the energy density, power characteristics, and cycle life of the battery. Summary of the Invention

[0003] The embodiments of the present application provide a method for preparing an electrode, an electronic device, and a storage medium, which can avoid the problem of losses in electrical properties such as the energy density, power characteristics, and cycle life of the battery while introducing PTC materials.

[0004] The present application provides a positive functional electrode, comprising:

[0005] A current collector;

[0006] A PTC effect layer, the PTC effect layer is disposed on the current collector, and the PTC effect layer includes a first binder;

[0007] An active layer, the active layer is disposed on the PTC effect layer, and the active layer includes a second binder.

[0008] Optionally, in some embodiments of the present application, the mass ratio of the first binder and the mass ratio of the second binder satisfy:

[0009]

[0010] wherein, the is the mass ratio of the first binder, and the is the mass ratio of the second binder.

[0011] Optionally, in some embodiments of the present application, the volume resistivity of the PTC effect layer and the volume resistivity of the active layer satisfy:

[0012]

[0013] wherein, the ρ PTC is the volume resistivity of the PTC effect layer, and the ρ Activeis the volume resistivity of the active layer.

[0014] In a second aspect, an electrode preparation method provided by an embodiment of the present application includes:

[0015] Mix a first phosphate material and a conductive agent according to a preset first ratio to obtain a first mixed solution;

[0016] Add a first preset solvent to the first mixed solution to form a first conductive paste, and add a first binder to the first conductive paste to form a PTC effect coating;

[0017] Mix a second phosphate material and a conductive agent according to a preset second ratio to obtain a second mixed solution;

[0018] Add a second preset solvent to the second mixed solution to form a second conductive paste, and add a second binder to the second conductive paste to form an active material;

[0019] Adopt a layered coating method to sequentially coat the PTC effect coating and the active material on the current collector to prepare a positive electrode functional electrode.

[0020] Optionally, in some embodiments of the present application, the adding a first preset solvent to the first mixed solution to form a first conductive paste, and adding a first binder to the first conductive paste to form a PTC effect coating includes:

[0021] Perform high-speed dispersion on the first mixed solution based on a preset duration;

[0022] Add a first preset solvent to the first mixed solution after high-speed dispersion to form a first conductive paste, and add a first binder to the first conductive paste to form a PTC effect coating.

[0023] Optionally, in some embodiments of the present application, the first binder is a polyvinylidene fluoride binder in a first crystalline form, and the mass ratio of the first binder is 0.02 - 0.5.

[0024] Optionally, in some embodiments of the present application, the adding a second preset solvent to the second mixed solution to form a second conductive paste, and adding a second binder to the second conductive paste to form an active material includes:

[0025] Perform high-speed dispersion on the second mixed solution based on a preset duration;

[0026] Add a second preset solvent to the second mixed solution after high-speed dispersion to form a second conductive paste, and add a second binder to the second conductive paste to form a PTC effect coating.

[0027] Optionally, in some embodiments of the present application, the second adhesive is a polyvinylidene fluoride adhesive in a second crystalline form, and the mass ratio of the second adhesive is 0.01 - 0.3.

[0028] Optionally, in some embodiments of the present application, the PTC effect coating and the active material are sequentially coated on the current collector by a layer-by-layer coating method to prepare a positive electrode functional electrode, including:

[0029] By a layer-by-layer coating method, the PTC effect coating and the active material are sequentially coated on the current collector to sequentially form a PTC effect layer and an active layer on the current collector, obtaining a positive electrode functional electrode.

[0030] In a third aspect, the present application further provides a battery, including a negative electrode functional electrode and the positive electrode functional electrode according to any one of the above.

[0031] The embodiments of the present application provide a positive electrode functional electrode, an electrode preparation method, and a battery. In this electrode preparation method, a first phosphate material and a conductive agent are mixed according to a preset first ratio to obtain a first mixed solution. Then, a first preset solvent is added to the first mixed solution to form a first conductive paste, and a first adhesive is added to the first conductive paste to form a PTC effect coating. Next, a second phosphate material and a conductive agent are mixed according to a preset second ratio to obtain a second mixed solution. Then, a second preset solvent is added to the second mixed solution to form a second conductive paste, and a second adhesive is added to the second conductive paste to form an active material. Finally, the PTC effect coating and the active material are sequentially coated on the current collector by a layer-by-layer coating method to prepare a positive electrode functional electrode. In the positive electrode functional electrode provided by the present application, the first phosphate material and the conductive agent act as the conductive network of the PTC effect coating, and at the same time, the second phosphate material is used as the active material, which can optimize the battery safety performance without causing losses in electrical properties such as energy density. The first adhesive will undergo a phase change and volume expansion at high temperatures, thereby destroying the electron flow conductive network when the battery overheats, increasing the internal resistance of the electrode, and preventing thermal runaway. Description of the Drawings

[0032] To more clearly illustrate the technical solutions in the embodiments of the present application, the following will briefly introduce the drawings required for the description of the embodiments. Obviously, the following drawings are only some embodiments of the present application. For those skilled in the art, without creative efforts, other drawings can be obtained based on these drawings.

[0033] Figure 1 It is a schematic flow chart of the electrode preparation method provided by the embodiments of the present application;

[0034] Figure 2 It is a schematic structural diagram of the positive electrode functional electrode provided by the embodiment of the present application. Detailed implementation manners

[0035] Next, the technical solutions in the embodiments of the present application will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative efforts belong to the scope of protection of the present application.

[0036] The embodiment of the present application provides a positive electrode functional electrode, an electrode preparation method, and a battery.

[0037] The following will be described in detail respectively. It should be noted that the description order of the following embodiments does not limit the priority order of the embodiments.

[0038] An electrode preparation method includes: mixing a first phosphate material and a conductive agent according to a preset first ratio to obtain a first mixed solution; adding a first preset solvent to the first mixed solution to form a first conductive paste, and adding a first binder to the first conductive paste to form a PTC effect coating; mixing a second phosphate material and a conductive agent according to a preset second ratio to obtain a second mixed solution; adding a second preset solvent to the second mixed solution to form a second conductive paste, and adding a second binder to the second conductive paste to form an active material; and sequentially coating the PTC effect coating and the active material on a current collector by a layer-by-layer coating method to prepare a positive electrode functional electrode.

[0039] Please refer to Figure 1 , Figure 1 which is a schematic flow chart of the electrode preparation method provided by the embodiment of the present application. The specific process of this electrode preparation method can be as follows:

[0040] 101. Mix a first phosphate material and a conductive agent according to a preset first ratio to obtain a first mixed solution.

[0041] When the first phosphate material is used as the cathode material of a lithium-ion battery, it refers to a type of phosphate compound that can reversibly intercalate and deintercalate lithium ions. Optionally, in some embodiments of the present application, the first phosphate material can be: lithium iron phosphate (LiFePO4), lithium manganese phosphate (LiMnPO4), lithium cobalt phosphate (LiCoPO4), and lithium nickel phosphate (LiNiPO4). It can also be phosphates of other metal elements, such as lithium vanadium phosphate (LiVOPO4), etc. Specifically, it can be selected according to the actual situation and is not limited here. Conductive agents usually have high electrical conductivity, good chemical stability, and good compatibility with electrode materials. Optionally, the conductive agent can be: carbon black, which has good electrical conductivity and chemical stability and can form a three-dimensional conductive network to improve the electron transfer rate of the electrode; graphite, which has high electrical conductivity and a layered structure; graphene, which is a two-dimensional carbon material with extremely high electrical conductivity and mechanical strength. Graphene can form a highly conductive network, significantly improving the electron transfer rate of the electrode. The layered structure of graphite helps the intercalation and deintercalation of lithium ions and also improves electron conductivity; carbon nanotubes (Carbon Nanotubes, CNTs), which have excellent electrical conductivity and mechanical properties; vapor grown carbon fibers (Vapor Grown Carbon Fibers, VGCF), which is a carbon fiber material with a high aspect ratio and has good electrical conductivity and chemical stability. VGCF can form a highly conductive network, improving the electron transfer rate and cycle stability of the electrode. Carbon nanotubes can form a highly conductive network, improving the electron transfer rate and cycle stability of the electrode; conductive polymers, such as polyaniline (PANI), polypyrrole (PPy), etc. These conductive polymers can form a conductive network in the electrode to improve electron conductivity. Conductive polymers can also provide additional mechanical support to improve the structural stability of the electrode

[0042] For example, specifically, select the first phosphate material (such as lithium iron phosphate LiFePO4) and the conductive agent (such as graphite, carbon black, graphene, carbon nanotubes, or VGCF). According to the requirements and expected performance of the battery design, determine the mass ratio of the first phosphate material to the conductive agent (i.e., the first preset ratio). This first preset ratio can be 1:0.01 or 1:0.5, that is, the mass ratio of the first phosphate material to the conductive agent is between 2 and 100. Specifically, it can be set according to the actual situation. Then, put the first phosphate material and the conductive agent into a mixing container according to the preset ratio to form a first mixed solution.

[0043] 102. Add a first preset solvent to the first mixed solution to form a first conductive paste, and add a first binder to the first conductive paste to form a PTC effect coating.

[0044] The first preset solvent refers to the solvent used for preparing the conductive paste of the PTC effect coating. This solvent is pre-selected to ensure that the electrode material, conductive agent, and binder can be uniformly mixed to form a paste with appropriate viscosity and rheological properties, so that it can be uniformly coated on the current collector through the coating process.

[0045] The first preset solvent can be N-methyl-2-pyrrolidone (NMP), which has good solubility and moderate volatility and is suitable for the preparation of pastes of various battery materials. It can also be other organic solvents such as dimethylformamide (DMF), dimethylacetamide (DMAC), etc.

[0046] The first conductive paste is a mixture prepared for the positive electrode functional electrode, which includes active material, conductive agent, binder, and solvent. The first conductive paste is a key component in the electrode coating process, and its quality and performance directly affect the electrochemical performance of the battery.

[0047] For example, specifically, an appropriate first solvent such as NMP (N-methyl-2-pyrrolidone) is selected to dissolve the binder and help form a uniform paste. Then, a solvent is added to the first mixed solution, and the first conductive paste is formed by stirring or other dispersion means. The viscosity and uniformity of the first conductive paste are crucial for the subsequent coating process. Then, a first binder such as β-phase PVDF (polyvinylidene fluoride) is added to the first conductive paste. The β-phase PVDF undergoes a phase change and volume expansion at high temperatures, thus destroying the electron flow conduction network when the battery overheats, increasing the internal resistance of the electrode, and preventing thermal runaway. By adding the first binder, the first conductive paste is transformed into a coating with PTC effect. This coating has good conductivity at normal operating temperatures, while when the battery temperature rises abnormally, it can increase the internal resistance through the PTC effect and reduce the risk of thermal runaway.

[0048] Optionally, in some embodiments of the present application, the step "adding a first preset solvent to the first mixed solution to form a first conductive paste, and adding a first binder to the first conductive paste to form a PTC effect coating" may specifically include:

[0049] Based on a preset duration, perform high-speed dispersion on the first mixed solution;

[0050] Add a first preset solvent to the first mixed solution after high-speed dispersion to form a first conductive paste, and add a first binder to the first conductive paste to form a PTC effect coating.

[0051] For example, specifically, a high-speed dispersion device (such as an ultrasonic processor, a high-speed mixer, or a ball mill) is used to disperse the first mixed solution. The dispersion time is preset to ensure sufficient mixing uniformity of the materials. The dispersion time can vary according to different material properties and the desired dispersion effect. Then, a first preset solvent, such as NMP (N-methyl-2-pyrrolidone), is gradually added to the first mixed solution after high-speed dispersion to form a first conductive paste. Finally, a first binder, namely β-phase - PVDF (polyvinylidene fluoride), is added to the first conductive paste. β-phase - PVDF undergoes a phase change and volume expansion at high temperatures, thereby destroying the electron flow conduction network when the battery overheats, increasing the internal resistance of the electrode, and preventing thermal runaway.

[0052] Optionally, in some embodiments of the present application, the first binder is a polyvinylidene fluoride binder in the first crystalline form (i.e., β-phase - PVDF binder), and the mass ratio of the first binder is 0.02 - 0.05. For example, 2 grams of β-phase - PVDF binder (i.e., a mass ratio of 0.02) is added to 100 grams of the first conductive paste, or 5 grams of β-phase - PVDF binder (i.e., a mass ratio of 0.5) is added to 100 grams of the first conductive paste. More binder can provide stronger adhesion, but too much binder may reduce the active material content of the electrode and affect the energy density of the battery. An appropriate amount of β-phase - PVDF binder can provide sufficient thermal protection at high temperatures to prevent thermal runaway, which can be adjusted according to the actual situation and will not be elaborated here.

[0053] 103. Mix the second phosphate material and the conductive agent according to a preset second preset ratio to obtain a second mixed solution.

[0054] For example, specifically, a suitable phosphate material is selected as the active component of the electrode, which may be different from the material used in the PTC effect coating, such as lithium manganese phosphate (LiMnPO4) or other types of phosphates. Then, a conductive agent, such as carbon black, graphene, carbon nanotubes (CNT), etc., is selected to improve the electronic conductivity of the electrode. It should be noted that in steps 101 and 103, the conductive agent can be the same or different, and can be specifically selected according to the actual situation. Then, according to the requirements and expected performance of the battery design, the mass ratio of the second phosphate material to the conductive agent (i.e., the second preset ratio) is determined. After putting the second phosphate material and the conductive agent into a mixing container according to the preset ratio, they are mixed by a mixer or other mixing equipment to form a uniform second mixed solution.

[0055] 104. Add a second preset solvent to the second mixed solution to form a second conductive paste, and add a second binder to the second conductive paste to form an active material.

[0056] For example, specifically, a second preset solvent is selected, such as NMP (N-methyl-2-pyrrolidone) or others, which is used to dissolve the binder and help form a uniform slurry. Then, the second preset solvent is added to the second mixed solution, and through stirring or other dispersion means, a second conductive slurry is formed. An α-phase-PVDF binder is added to the second conductive slurry to form an active material. The α-phase-PVDF provides good bonding performance during the operation of the battery.

[0057] Optionally, in some embodiments of the present application, the step of "mixing the second phosphate material and the conductive agent according to a preset second ratio to obtain a second mixed solution" may specifically include:

[0058] Based on a preset duration, the second mixed solution is subjected to high-speed dispersion;

[0059] A second preset solvent is added to the second mixed solution after high-speed dispersion to form a second conductive slurry, and a second binder is added to the second conductive slurry to form a PTC effect coating.

[0060] For example, specifically, a high-speed dispersion device is used to disperse the second mixed solution, and the dispersion time is based on the preset duration to ensure uniform mixing of the materials. Then, the second preset solvent, such as NMP (N-methyl-2-pyrrolidone), is gradually added to the second mixed solution after high-speed dispersion, so that the mixture is transformed into a second conductive slurry, which has good rheological properties and is convenient for coating. Optionally, in some embodiments of the present application, the second binder is α-phase-PVDF (polyvinylidene fluoride), and the α-phase-PVDF is used for the active material coating to provide good adhesion and electrochemical stability. Then, an α-phase-PVDF binder is added to the second conductive slurry, and the second conductive slurry is transformed into an active material coating for the positive functional electrode of the battery.

[0061] Optionally, in some embodiments of the present application, the second binder is a polyvinylidene fluoride binder in a second crystalline form, and the mass ratio of the second binder is 0.01 - 0.3.

[0062] The mass ratio of the second binder being 0.01 - 0.3 means that in 100 grams of the second conductive slurry, the addition amount of α-phase-PVDF is between 0.01 grams and 30 grams. For example, 10 grams of the second binder is added to 100 grams of the second conductive slurry, that is, a second binder with a mass ratio of 0.1 is added to form an active material.

[0063] 105. By using a layer-by-layer coating method, the PTC effect coating and the active material are sequentially coated on the current collector to prepare a positive functional electrode.

[0064] For example, specifically, a current collector material such as aluminum foil or copper foil is selected. Then, a PTC effect coating is applied, and then the PTC effect coating is uniformly applied on one side of the current collector. This step can use a doctor blade coating, spraying or other coating techniques. After coating, the PTC effect coating needs to be dried at an appropriate temperature and time to remove the solvent and cure the adhesive. Then, an active material is applied on the already dried PTC effect coating, whereby two different functional layers, namely a PTC effect layer and an active material layer, are formed on the same side of the same current collector. This structure allows the electrode to have excellent electrochemical performance under normal operating conditions, while improving safety through the PTC effect under overheating conditions.

[0065] Optionally, in some embodiments of the present application, the step of "using a layered coating method to sequentially coat a PTC effect coating and an active material on a current collector to prepare a positive electrode functional electrode" may specifically include:

[0066] Using a layered coating method to sequentially coat a PTC effect coating and an active material on a current collector to sequentially form a PTC effect layer and an active layer on the current collector, thereby obtaining a positive electrode functional electrode.

[0067] The embodiments of the present application provide a method for preparing an electrode. After mixing a first phosphate material and a conductive agent in a preset first preset ratio to obtain a first mixed solution, a first preset solvent is added to the first mixed solution to form a first conductive paste, and a first binder is added to the first conductive paste to form a PTC effect coating. Then, a second phosphate material and a conductive agent are mixed in a preset second preset ratio to obtain a second mixed solution. Then, a second preset solvent is added to the second mixed solution to form a second conductive paste, and a second binder is added to the second conductive paste to form an active material. Finally, a layered coating method is used to sequentially coat the PTC effect coating and the active material on a current collector to prepare a positive electrode functional electrode. In the positive electrode functional electrode provided by the present application, the first phosphate material and the conductive agent are used as the conductive network of the PTC effect coating, and at the same time, the second phosphate material is used as the active material, which can optimize the battery safety performance without causing losses in electrical properties such as energy density. The first binder will undergo a phase change and volume expansion at high temperatures, thereby destroying the electron flow conductive network when the battery overheats, increasing the internal resistance of the electrode, and preventing thermal runaway.

[0068] In addition, the embodiments of the present application also provide a positive electrode functional electrode, as Figure 2 shown, specifically:

[0069] The positive electrode functional electrode may include a current collector 201, a PCT effect layer 202, and an active layer 203. The positive electrode functional electrode is made by using the electrode preparation method of any of the above embodiments. Among them, the PCT effect layer 202 is disposed on the current collector 201. The PCT effect layer 202 includes a first binder, and the active layer 203 is disposed on the PCT effect layer 202. The active layer 203 includes a second binder.

[0070] Optionally, in some embodiments of the present application, the mass ratio of the first binder to the mass ratio of the second binder satisfies:

[0071]

[0072] Wherein, is the mass ratio of the first binder, is the mass ratio of the second binder.

[0073] Optionally, in some embodiments of the present application, the volume resistivity of the PTC effect layer 202 and the volume resistivity of the active layer 203 satisfy:

[0074]

[0075] Wherein, ρ PTC is the volume resistivity of the PCT effect layer 202, and ρ Active is the volume resistivity of the active layer 203.

[0076] An embodiment of the present application provides a positive electrode functional electrode, including: a current collector 201, a PCT effect layer 202, and an active layer 203. The positive electrode functional electrode is made by using the electrode preparation method of any of the above embodiments. Among them, the PCT effect layer 202 is disposed on the current collector 201. The PCT effect layer 202 includes a first binder, and the active layer 203 is disposed on the PCT effect layer 202. The active layer 203 includes a second binder. In the positive electrode functional electrode provided by the present application, a first phosphate material and a conductive agent are used as the conductive network of the PCT effect layer 202. At the same time, a second phosphate material is used as the active layer 203, which can optimize the battery safety performance without causing loss of electrical properties such as energy density. The first binder will undergo a phase change and volume expansion at high temperatures, thereby destroying the electron flow conductive network when the battery overheats, increasing the internal resistance of the electrode, and preventing thermal runaway.

[0077] The present application further provides a battery, including a negative electrode functional electrode and the positive electrode functional electrode of any of the above.

[0078] To facilitate further understanding of the solution of the present application, the following takes the preparation process as an example for specific description, specifically as follows:

[0079] This application provides a positive functional electrode, which contains at least two types of coatings:

[0080] PTC (PTC-Coating) effect coating. The PTC effect coating includes a PTC coating material, a binder, and a conductive agent. The PTC coating material is phosphate material A, the binder is β-phase - PVDF, and the conductive agent is one or more of graphite, carbon black, graphene, carbon nanotubes, and VGCF. The thickness of the PTC effect coating is 0.5 - 80 μm; Active material (Active-Coating) coating. The active material coating includes an active material, a binder, and a conductive agent. The active material is phosphate material B, the binder is α-phase - PVDF, and the conductive agent is one or more of graphite, carbon black, graphene, carbon nanotubes, and VGCF. The thickness of the active material coating is 0.5 - 100 μm.

[0081] 1. Preparation of positive functional electrode

[0082] (1) Mix phosphate material A and the conductive agent according to a mass ratio of 1:(0.01 - 0.5), disperse them in NMP to make a conductive paste, and after high-speed dispersion for 0.5 - 1.5 hours, add a β-phase - PVDF binder with a mass ratio of (0.02 - 0.5) to prepare the PTC effect coating, with the paste viscosity of 800 - 10000 mPa·s;

[0083] (2) Mix phosphate material B and the conductive agent according to a mass ratio of 1:(0.01 - 0.7), disperse them in NMP to make a conductive paste, and after high-speed dispersion for 0.5 - 1.5 hours, add an α-phase - PVDF binder with a mass ratio of (0.01 - 0.3) to prepare the active material coating, with the paste viscosity of 500 - 12000 mPa·s;

[0084] (3) Coating the prepared PTC effect coating and active material coating on both sides of the current collector in a layered coating manner on the aluminum foil current collector to prepare the positive functional electrode, represents the mass ratio of β-phase - PVDF in the PTC effect coating, represents the mass ratio of α-phase - PVDF in the active material coating, and the mass ratio of β-phase - PVDF satisfies ρPTC represents the volume resistivity of the PTC effect coating, ρActive represents the volume resistivity of the active material coating, and the volume resistivity of the dressing layer satisfies SPTC represents the particle size distance of phosphate material A in the PTC effect coating, SActive represents the particle size distance of phosphate material B in the active material coating, and the particle size distance ratio of the materials satisfies

[0085] Among them, the thickness of the aluminum foil current collector substrate is 12-16 μm, the weight of the substrate is 0.5-1.5 g, the coating thickness is 0.5-80 μm, and the coating width is 50-1000 mm;

[0086] 2. Preparation of the negative electrode functional electrode

[0087] The negative electrode active material used for the negative electrode functional electrode can be one or more of carbon-based negative electrodes (graphitized carbon, amorphous carbon, carbon nanomaterials, etc.) and non-carbon-based negative electrodes (titanium-based materials, tin-based materials, silicon-based materials, etc.); Using a carbon-based negative electrode or a non-carbon-based negative electrode as the negative electrode active material, the negative electrode material, conductive agent, and binder are homogenized to form a negative electrode slurry, and then the above negative electrode slurry is coated on both sides of the negative electrode current collector to prepare the negative electrode functional electrode, where the proportion of the negative electrode material is 80-99%, and the single-sided surface density of the negative electrode active coating is 30-500 g / m2.

[0088] 3. Electrical performance testing

[0089] (1) Energy density

[0090] The tested battery is charged at a constant current and constant voltage of 0.33C to 3.7V, cut off at 0.05C, and then discharged at 0.33C to 2.5V. Record the capacity, average voltage, and battery mass, and calculate the energy density of the battery according to the following formula: Energy density = Capacity * Average voltage / Battery mass.

[0091] (2) DC impedance

[0092] The tested battery is charged at a constant current and constant voltage of 0.33C to 3.7V, cut off at 0.05C, then discharged at 0.33C for 90 minutes, left standing for 60 minutes, and record the voltage V1 at the end of the standing; then discharge at 1C (current I) for 30 seconds, and record the voltage V2 at the end of the discharge. Calculate the DC impedance of the battery according to the following formula: DC impedance = |V1 - V2| / I.

[0093] (3) Cycle performance

[0094] The tested battery is placed in a constant temperature oven at 25°C, charged at a constant current and constant voltage of 0.5C, cut off at 0.05C, and then discharged at 1C until 80% SOH, and record the number of cycles.

[0095] (4) Safety performance

[0096] After the tested battery is fully charged, it is placed in a thermal box test cabinet and heated at a rate of 5°C / min to 155°C and left standing for 1 hour. Observe whether there is fire / smoke, and record the OCV after the test ends.

[0097] 4. Experimental control

[0098] (1) Conventional electrode battery: The positive electrode paste is uniformly prepared by combining LiFePO4, binder α-phase - PVDF, and conductive agent acetylene black in a mass ratio of 98:1:1. Then, the above positive electrode paste is coated on both sides of the positive electrode current collector. The average surface density of the single side of the positive electrode active coating it includes is 230 g / m2. Subsequently, a conventional battery is prepared by stacking a separator, a graphite negative electrode, a positive electrode plate, a separator, a graphite negative electrode, and a separator in sequence.

[0099] (2) Self-regulating function electrode battery: The PTC effect coating paste is uniformly prepared by combining LiFePO4, binder β-phase - PVDF, and conductive agent acetylene black in a mass ratio of 30:60:10. Then, the above PTC effect coating paste is coated on both sides of the positive electrode current collector. The average surface density of the single side of the PTC effect coating it includes is 90 g / m2. The active material coating paste is uniformly prepared by combining LiFePO4, binder α-phase - PVDF, and conductive agent acetylene black in a mass ratio of 98:1:1. Then, the above active material coating paste is coated on both sides of the positive electrode current collector. The average surface density of the single side of the active material coating it includes is 150 g / m2. Subsequently, a self-regulating function electrode battery is prepared by stacking a separator, a graphite negative electrode, a self-regulating function positive electrode plate, a separator, a graphite negative electrode, and a separator in sequence.

[0100] The first battery only contains conventional electrodes. After fully charging the first battery, it is placed in a thermal chamber test cabinet and heated to 155°C at a heating rate of 5°C / min, and then left standing for 1 h. It is observed that there is no fire / smoke phenomenon in the battery. After the test, the open circuit voltage (OCV) is measured to be 2.80 V, which conforms to the safety performance data in the document.

[0101] Using a standard battery charge-discharge test device, the assembled first battery is charged at a constant current and constant voltage with a current of 0.33C, and the charging cut-off voltage is set to 3.7V. When the charging current drops to 0.05C, the charging stops. Then, it is discharged at a current of 0.33C to 2.5V. During the charge-discharge process, the capacity, average voltage, and mass of the first battery are recorded. The battery capacity of the first battery is 10 Ah, the average voltage is 3.62V, and the battery mass is 200 g (0.2 kg). According to the energy density calculation formula: energy density = capacity × average voltage ÷ battery mass, the energy density of the first battery is calculated to be 181 Wh / kg.

[0102] DC impedance test: First, charge the battery at a constant current and voltage of 0.33C until 3.7V, with the charging cut-off current being 0.05C. Then, discharge it at a current of 0.33C for 90 minutes, let it rest for 60 minutes after discharge, and record the terminal voltage V1 at this time. Next, discharge it at a current of 1C for 30 seconds and record the discharge terminal voltage V2. The terminal voltage V1 = 3.5V, the discharge terminal voltage V2 = 3.4637V, and the discharge current I = 1A. According to the DC impedance calculation formula: DC impedance = |V1 - V2| ÷ I, the calculated DC impedance of this battery is 38.3%.

[0103] Cycling performance test: Place the battery in an incubator at 25°C and charge it at a constant current and voltage of 0.5C, with the charging cut-off current being 0.05C. After charging is completed, discharge it at a current of 1C, and perform such charge and discharge cycles. Continuously monitor the state of health (SOH) of the battery. When the SOH of the battery drops to 80%, record the number of cycles as 5000 times.

[0104] Safety performance test: Put the fully charged conventional electrode battery into a thermal chamber test cabinet, set the heating rate to 5°C / min, raise the temperature to 155°C, and let it stand at this temperature for 1 hour. During the test, observe whether there are any abnormal phenomena such as the battery catching fire or smoking. After the test, measure the open circuit voltage (OCV) of the battery. It is found that there is a fire phenomenon and the OCV is 2.65V.

[0105] The second battery includes a self-regulating function electrode (i.e., the positive electrode function electrode provided in the embodiments of the present application). Charge the second battery at a constant current and voltage of 0.33C until 3.7V, cut off at 0.05C, and then discharge it at 0.33C to 2.5V. Record the battery capacity of the battery as 15Ah, the average voltage as 2.4V, and the battery mass as 0.2kg. According to the formula "energy density = capacity * average voltage / battery mass", the calculated energy density is 180Wh / kg, which is close to the data in the document.

[0106] DC impedance test: Charge the battery at a constant current and voltage of 0.33C until 3.7V, cut off at 0.05C, then discharge it at 0.33C for 90 minutes, let it rest for 60 minutes, and record the terminal voltage V1 at rest; then discharge it at a current of 1C for 30 seconds and record the discharge terminal voltage V2. The terminal voltage V1 = 3.4V, the discharge terminal voltage V2 = 3.3638V, and the discharge current I = 1A. Calculate according to the formula "DC impedance = |V1 - V2| / I", and the obtained DC impedance is 36.2%, which is consistent with the document data.

[0107] Cyclic performance test: Place the battery in an incubator at 25°C, charge it at a constant current and constant voltage of 0.5C until cutoff at 0.05C, then discharge it at 1C until the state of health (SOH) of the battery reaches 80%. Record the number of cycles as 5300 times, which is consistent with the data in the document.

[0108] Specifically, it is shown in Table 1 as follows:

[0109]

[0110] Table 1

[0111] The above has introduced in detail a positive electrode functional electrode, an electrode preparation method, and a battery provided by an embodiment of the present application. Specific examples are used in this article to elaborate on the principle and implementation manner of the present application. The description of the above embodiments is only used to help understand the method and its core idea of the present application; at the same time, for those skilled in the art, according to the idea of the present application, there will be changes in the specific implementation manner and application scope. In summary, the content of this specification should not be construed as a limitation to the present application.

Claims

1. A positive functional electrode, characterized in that: include: current collector; A PTC effect layer, wherein the PTC effect layer is disposed on the current collector, and the PTC effect layer comprises a first adhesive; An active layer is disposed on the PTC effect layer, and the active layer includes a second adhesive.

2. The positive functional electrode according to claim 1, characterized in that: The mass ratio of the first adhesive and the mass ratio of the second adhesive satisfy: Among them, the is the mass ratio of the first adhesive, is the mass ratio of the second adhesive.

3. The positive functional electrode according to claim 1, characterized in that: The volume resistivity of the PTC effect layer and the volume resistivity of the active layer satisfy: Among them, the PTC is the volume resistivity of the PTC effect layer, the ρ Active is the volume resistivity of the active layer.

4. A method for preparing an electrode, characterized in that: include: Mixing the first phosphate material and the conductive agent according to a first preset ratio to obtain a first mixed solution; Adding a first preset solvent to the first mixed solution to form a first conductive paste, and adding a first adhesive to the first conductive paste to form a PTC effect coating; Mixing the second phosphate material and the conductive agent according to a second preset ratio to obtain a second mixed solution; Adding a second preset solvent to the second mixed solution to form a second conductive paste, and adding a second adhesive to the second conductive paste to form an active material; The PTC effect coating and the active material are coated on the current collector in sequence in a layered coating manner to prepare a positive functional electrode.

5. The electrode preparation method according to claim 4, characterized in that: The step of adding a first preset solvent to the first mixed solution to form a first conductive paste, and adding a first adhesive to the first conductive paste to form a PTC effect coating comprises: Based on a preset time, the first mixed solution is dispersed at a high speed; A first preset solvent is added to the first mixed solution after high-speed dispersion to form a first conductive paste, and a first adhesive is added to the first conductive paste to form a PTC effect coating.

6. The electrode preparation method according to claim 5, characterized in that: The first adhesive is a polyvinylidene fluoride adhesive in a first crystal form, and the mass ratio of the first adhesive is 0.02-0.

5.

7. The electrode preparation method according to claim 4, characterized in that: The step of adding a second preset solvent to the second mixed solution to form a second conductive paste, and adding a second adhesive to the second conductive paste to form an active material comprises: Based on a preset time, dispersing the second mixed solution at a high speed; A second preset solvent is added to the second mixed solution after high-speed dispersion to form a second conductive paste, and a second adhesive is added to the second conductive paste to form a PTC effect coating.

8. The electrode preparation method according to claim 7, characterized in that: The second adhesive is a polyvinylidene fluoride adhesive in a second crystal form, and the mass ratio of the second adhesive is 0.01-0.

3.

9. The electrode preparation method according to any one of claims 4 to 8, characterized in that: The method of layered coating is used to sequentially coat the PTC effect coating and the active material on the current collector to prepare a positive functional electrode, including: The PTC effect coating and the active material are coated on the current collector in sequence by layered coating, so as to form a PTC effect layer and an active layer on the current collector in sequence, thereby obtaining a positive functional electrode.

10. A battery comprising a negative functional electrode, characterized in that: It also comprises the positive functional electrode as claimed in any one of claims 1 to 3.

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