A positive electrode, a battery, and an electrical device

Abstract

This application provides a positive electrode sheet, a battery, and an electrical device, including a positive electrode current collector and a positive electrode active layer located on at least one side of the positive electrode current collector. The positive electrode active layer includes a first active layer and a second active layer located on the side of the first active layer opposite to the positive electrode current collector. The positive electrode sheet satisfies the following conditions: This application can simultaneously improve the rate performance and capacity of the battery.

Description

Technical Field

[0001] This application relates to the field of batteries, and more particularly to a positive electrode, a battery, and an electrical device. Background Technology

[0002] The positive electrode is a crucial component of a battery and significantly impacts its electrochemical performance. Currently, the internal ionic conductivity of the positive electrode is low, hindering the transport of active ions and resulting in poor rate performance. Optimizing the internal ionic conductivity by reducing the thickness of the positive electrode, however, leads to a decrease in battery capacity. Therefore, existing battery technologies generally suffer from the inability to simultaneously improve both rate performance and capacity, a problem that urgently needs to be addressed. Summary of the Invention

[0003] This application provides a positive electrode, a battery, and an electrical device that can simultaneously improve the rate performance and capacity of the battery.

[0004] In a first aspect, embodiments of this application provide a positive electrode sheet, including a positive current collector and a positive active layer located on at least one side of the positive current collector, the positive active layer including a first active layer and a second active layer located on the side of the first active layer opposite to the positive current collector, the positive electrode sheet satisfying:

[0005] ,

[0006] Wherein, d1 is the thickness of the first active layer in μm, d2 is the thickness of the second active layer in μm, σ1 is the ionic conductivity of the first active layer in mS / cm, σ2 is the ionic conductivity of the second active layer in mS / cm, ρ1 is the porosity of the first active layer in % and ρ2 is the porosity of the second active layer in %

[0007] In one possible implementation, d1 is 20μm to 50μm; preferably, d1 is 30μm to 50μm.

[0008] In one possible implementation, d2 is 20μm to 80μm; preferably, d2 is 30μm to 80μm.

[0009] In one possible implementation, σ1 is 0.01 mS / cm to 0.1 mS / cm; preferably, σ1 is 0.02 mS / cm to 0.1 mS / cm; and / or, σ2 is 0.02 mS / cm to 0.11 mS / cm.

[0010] In one possible implementation, ρ1 is 19% to 28%; and / or, ρ2 is 23% to 35%.

[0011] In one possible implementation, the ratio of d2 to d1 is greater than or equal to 1.

[0012] In one possible implementation, the first active layer and the second active layer each independently comprise a positive electrode active material and a solid electrolyte.

[0013] Secondly, embodiments of this application provide a battery including the aforementioned positive electrode sheet, wherein the battery is any one of a single cell, a battery module, and a battery pack.

[0014] In one possible implementation, the battery includes a solid-state battery.

[0015] Thirdly, embodiments of this application provide an electrical device including the battery described above.

[0016] This application provides a positive electrode sheet, a battery, and an electrical device, wherein the positive electrode sheet satisfies the following: By synergistically optimizing the relationship between the thickness of the first active layer and the second active layer, the relationship between ionic conductivity and porosity, the microstructure and conductive network of the positive electrode sheet can be coordinated and controlled, the solid-solid interface contact efficiency can be optimized, the ion transport capability of the positive electrode sheet can be improved, and the rate performance of the battery can be enhanced. At the same time, the effective utilization of the positive electrode active material in the positive electrode sheet can be ensured, and the capacity of the battery can be improved. Therefore, this application can simultaneously improve the rate performance and capacity of the battery. Detailed Implementation

[0017] To enable those skilled in the art to better understand the solutions of this invention, the following provides a more detailed description of this application. The specific embodiments listed below are merely descriptions of the principles and features of this invention; the examples are only for explaining the invention and are not intended to limit its scope. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without inventive effort are within the scope of protection of this invention.

[0018] In view of this, embodiments of the present invention provide a positive electrode sheet, including a positive current collector and a positive active layer located on at least one side of the positive current collector. The positive active layer includes a first active layer and a second active layer located on the side of the first active layer opposite to the positive current collector. The positive electrode sheet satisfies the following:

[0019] ,

[0020] Wherein, d1 is the thickness of the first active layer in μm, d2 is the thickness of the second active layer in μm, σ1 is the ionic conductivity of the first active layer in mS / cm, σ2 is the ionic conductivity of the second active layer in mS / cm, ρ1 is the porosity of the first active layer in % and ρ2 is the porosity of the second active layer in %

[0021] According to the inventors' research, a positive electrode sheet that meets the above structure and conditions can simultaneously improve the rate performance and capacity of the battery. The reason for this is that by synergistically optimizing the relationship between the thickness of the first active layer and the second active layer, the relationship between ionic conductivity and porosity, the microstructure and conductive network of the positive electrode sheet can be controlled in a coordinated manner, optimizing the solid-solid interface contact efficiency, improving the ion transport capability of the positive electrode sheet, and improving the rate performance of the battery. At the same time, it can ensure the effective utilization of the positive electrode active material in the positive electrode sheet and improve the battery's capacity utilization.

[0022] Specifically, the thickness of the positive electrode active layer within the aforementioned range can balance the battery's capacity and kinetic performance. A suitable thickness of the positive electrode active layer can increase the loading of the positive electrode active material and shorten the active ion transport path. By synergistically limiting the thickness d1 of the first active layer and the thickness d2 of the second active layer, the transport kinetics of active ions within the positive electrode sheet can be improved. A suitable positive electrode sheet ionic conductivity can improve the transport efficiency of active ions, reduce interface impedance, and enhance the battery's rate performance. Appropriate ρ1 and ρ2 can optimize the solid-solid interface contact, reduce interface impedance, and prevent the breakage of the positive electrode active material, reduce internal defects in the positive electrode sheet, and ensure the full utilization of the positive electrode sheet's capacity. Therefore, by synergistically limiting d1, d2, σ1, σ2, ρ1, and ρ2, the above relationships can be kept within the range of 1 to 3, thus balancing the improvement of the battery's rate performance and capacity.

[0023] In addition, d1 and d2 within the above range can take into account the stress changes caused by the volume change of the positive electrode during cycling. At the same time, appropriate ρ1 and ρ2 can alleviate the volume expansion of the positive electrode active material during charging and discharging, thereby improving the cycle life of the battery.

[0024] In this embodiment of the invention, It can be a range consisting of 1, 2, 3, or any two of them. If the value is less than 1, the thickness, electronic conductivity, and porosity of the first active layer are too small, and / or the thickness, electronic conductivity, and porosity of the second active layer are too large. This is detrimental to optimizing the solid-solid interface contact efficiency of the second active layer. Simultaneously, it hinders the migration of active ions within the positive electrode, leading to a decrease in the battery's rate performance. A large difference in the concentration of active ions between the first and second active layers will result in capacity decay. If the value is greater than 3, the thickness, electronic conductivity, and porosity of the first active layer are too large and / or the thickness, electronic conductivity, and porosity of the second active layer are too small. The migration rate of active ions in the second active layer is too slow, the diffusion of active ions during the charging and discharging process is restricted, concentration polarization is easily triggered, and capacity decay is caused.

[0025] In this embodiment of the invention, a positive active layer can be provided on one side of the positive current collector, or a positive active layer can be provided on both sides of the positive current collector in the thickness direction.

[0026] In this embodiment of the invention, d1, d2, σ1, σ2, ρ1, and ρ2 can be measured by the following method: Take the above-mentioned positive electrode sheet:

[0027] (1) Test method for d1 and d2: d1 and d2 can be measured by taking a cross-section of the positive electrode active layer with a scanning electron microscope (SEM). SEM is a conventional method used in this field and is not limited here.

[0028] (2) Test methods for ρ1 and ρ2: The total porosity ρ of the positive electrode active layer is measured by mercury intrusion porosimetry. The second active layer is scraped off, and the porosity ρ1 of the first active layer is measured by mercury intrusion porosimetry. Then ρ2 = ((d1+d2)×ρ-ρ1×d1) / d2. Mercury intrusion porosimetry is a conventional method for measuring porosity in this field and is not restricted here.

[0029] (3) Test methods for σ1 and σ2: The electrochemical workstation was used to test and obtain the Nyquist impedance spectrum of the positive electrode. The distance between the x-coordinate of the inflection point of the slope change in the diffusion part and the inflection point of the slope change in the high frequency part in the Nyquist impedance spectrum was read by linear fitting and taken as 1 / 3R. ele +1 / 3R ion The mid-frequency component was fitted by a straight line, and its intersection with the horizontal axis was used as R. ele ×R ion / (R) ion +R ele The ionic impedance value R0 (Ω) of the positive electrode active layer is calculated based on these two values. The result is then expressed as σ = L / (R × A), where R is the ionic impedance value (Ω) and A is the apparent surface area of ​​the corresponding positive electrode sample (cm²). 2 The ionic conductivity of the positive electrode active layer was calculated as σ0 = (d1 + d2) / (R0 × A), where (d1 + d2) is the thickness of the positive electrode active layer (cm).

[0030] After scraping off the second active layer, electrochemical workstation was used to perform tests, obtaining the Nyquist impedance spectrum of the first active layer. Linear fitting was used to read the distance between the x-coordinates of the inflection points of the diffusion slope abrupt change and the high-frequency slope abrupt change in the Nyquist impedance spectrum as 1 / 3R. ele +1 / 3R ion The mid-frequency component was fitted by a straight line, and its intersection with the horizontal axis was used as R. ele ×R ion / (R ion +R ele The ionic impedance value R1 (Ω) of the first active layer is calculated based on these two values. The ionic conductivity of the first active layer is then calculated using σ1 = d1 / (R1×A), where d1 is the thickness (cm) of the first active layer.

[0031] Then, based on 1 / σ0=1 / σ1+1 / σ2, the ionic conductivity σ2 of the second active layer is obtained;

[0032] Where A is the measured apparent area (cm²) of the corresponding positive electrode active layer. 2 R can be measured using a micrometer. ele R is the electronic impedance value. ion This represents the ionic impedance value.

[0033] In some embodiments, d1 is 20μm to 50μm, for example, it can be a range of 20μm, 30μm, 40μm, 50μm or any combination thereof. If d1 is not less than 20μm, it can avoid insufficient positive electrode active material and is more conducive to improving battery capacity. If d1 is not greater than 50μm, it can further improve the internal transport rate of active ions in the positive electrode sheet. Therefore, if d1 is 20μm to 50μm, it is more conducive to balancing the improvement of battery capacity and rate.

[0034] In some preferred embodiments, d1 is 30μm~50μm, further balancing the improvement of the battery's rate performance and capacity.

[0035] In some embodiments, d2 is 20μm to 80μm, for example, it can be a range of 20μm, 30μm, 40μm, 50μm, 60μm, 70μm, 80μm or any combination thereof. If d2 is not less than 20μm, it can further increase the loading of the positive electrode active material. If d2 is not greater than 80μm, it is more conducive to balancing the diffusion of active ions from the electrolyte side to the inside of the positive electrode sheet and the conduction of electrons from the positive electrode current collector to the first and second active layers, avoiding capacity decay and rate performance reduction due to limited diffusion of active ions. Therefore, d2 is 20μm to 80μm, which can further balance the loading of the positive electrode active material and the length of the active ion transport path.

[0036] In some preferred embodiments, d2 is 30μm~80μm, which is more conducive to balancing the loading of positive electrode active material and the active ion transport rate.

[0037] At the same time, through the coordinated operation of d1 and d2, the thickness of the positive electrode active layer is ensured, the battery capacity is improved, and the transport rate of active ions inside the positive electrode sheet, i.e., the first active layer, is ensured.

[0038] In some embodiments, σ1 is 0.01 mS / cm to 0.1 mS / cm, for example, it can be a range of 0.01 mS / cm, 0.02 mS / cm, 0.05 mS / cm, 0.1 mS / cm or any combination thereof. If σ1 is not less than 0.01 mS / cm, it can further reduce the impedance of the first active layer and improve the rate performance of the battery. If σ1 is not greater than 0.1 mS / cm, it can avoid the decrease in the proportion of positive electrode active material in the first active layer, which would lead to the capacity decay of the battery. Therefore, σ1 of 0.01 mS / cm to 0.1 mS / cm is more conducive to improving the rate performance and capacity of the battery.

[0039] In some preferred embodiments, σ1 is 0.02mS / cm to 0.1mS / cm, which is more conducive to the utilization of battery capacity and the improvement of battery rate performance.

[0040] In some embodiments, σ2 is 0.02 mS / cm to 0.11 mS / cm, for example, it can be a range of 0.02 mS / cm, 0.05 mS / cm, 0.1 mS / cm, 0.11 mS / cm, or any combination thereof. σ2 is not less than 0.02 mS / cm, which can further improve the transport rate of active ions in the second active layer and synergistically construct the ion-conducting network of the positive electrode. σ2 is not greater than 0.11 mS / cm, which can avoid the decrease in the proportion of positive electrode active material in the second active layer, and at the same time, avoid reducing the solid-solid interface contact efficiency. Therefore, σ2 of 0.02 mS / cm to 0.11 mS / cm is more conducive to improving the active ion transport efficiency of the positive electrode active layer and improving the battery capacity and rate performance.

[0041] In some embodiments, ρ1 is 19% to 28%, for example, it can be a range of 19%, 24%, 27%, 28% or any two of them. ρ1 not less than 19% can further reduce the resistance to active ion transport in the first active layer. ρ1 not greater than 28% can further help to increase the compaction density of the positive electrode, improve the contact between the first active layer and the positive current collector, and improve the structural stability of the positive electrode. Therefore, ρ1 of 19% to 28% can further improve the structural stability of the positive electrode and improve the active ion transport rate and capacity utilization of the positive electrode.

[0042] In some embodiments, ρ2 is 23% to 35%, for example, it can be a range of 23%, 27%, 30%, 34%, 35% or any two of them. ρ2 not less than 23% is more conducive to the entry and exit of active ions on the surface of the positive electrode during charging and discharging. ρ2 not greater than 35% can further improve the solid-solid interface contact efficiency. At the same time, it avoids excessive porosity of the second active layer, which is not conducive to the overall capacity utilization of the positive electrode. Therefore, ρ2 of 23% to 35% can further improve the rate performance and capacity of the battery.

[0043] In one possible implementation, the ratio of d2 to d1 is greater than or equal to 1. For example, it can be a range of 1, 1.5, 2, 3, 5, 8, 10, or any two of them. This is more conducive to balancing the loading of positive electrode active material in the positive electrode and the internal transport rate of active ions in the positive electrode, thereby improving the battery's capacity and rate performance.

[0044] In some embodiments, the first active layer and the second active layer each independently include a positive electrode active material and a solid electrolyte, which can further optimize the rate performance and capacity of the battery.

[0045] In some embodiments, the positive electrode active material may include LiNi x Co y M 1−x−y O2, wherein 0≤x≤1, 0≤y≤1, and M is at least one of manganese or aluminum; the positive electrode active material may include one or more of lithium cobalt oxide, lithium nickel oxide, lithium manganese oxide, lithium nickel manganese oxide, lithium nickel cobalt manganese oxide, and lithium nickel cobalt aluminum oxide, but is not limited thereto.

[0046] Specifically, the positive electrode active material may include LiCoO2, LiNiO2, LiMnO2, LiMn2O4, and LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 O2 (NCM333), LiNi 0.5 Co 0.2 Mn 0.3 O2 (NCM523), LiNi 0.6 Co 0.2 Mn 0.2 O2 (NCM622), LiNi 0.8 Co 0.1 Mn 0.1 O2 (NCM811), LiNi 0.85 Co 0.15 Al 0.05 One or more of O2.

[0047] Specifically, the positive electrode active material can also be modified, for example by coating, doping or other surface modification techniques, to slow down the reaction between the positive electrode active material and the electrolyte material and improve its ion transport capability.

[0048] In some embodiments, the solid electrolyte (first solid electrolyte) in the first active layer and the second active layer may include a sulfide solid electrolyte, which may include Li2S-P2S5, Li6PS5Cl (LPSCl), Li 5.5 PS 4.5 Cl 1.5 , Li6PS5Br (LPSBr), Li6PS5I, Li 11 Si2PS 12 Li 10 SnP2S 12 Li 10 GeP2S 12 Li 3.25 Ge 0.25 P 0.75 S4, Li 10 Ge(P 1-x Sb x )2S 12 Li 6.6 Ge 0.6 P 0.4 One or more of S5I can further improve the effective ionic conductivity of the positive electrode and increase the battery rate.

[0049] Specifically, the positive electrode active layer may also include a positive electrode conductive agent and a positive electrode binder. The positive electrode conductive agent and the positive electrode binder can be conventional materials in the art. For example, the positive electrode conductive agent may include one or more of conductive carbon black (Super P), vapor-grown carbon fiber (VGCF), carbon nanotubes (CNT), and activated carbon. The positive electrode binder may include one or more of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), polyisobutylene (PIB), styrene-butadiene-styrene block copolymer (SBS), styrene-ethylene-butene-styrene block copolymer (SEBS), styrene-butadiene rubber (SBR), nitrile rubber (NBR), hydrogenated nitrile rubber (HNBR), and polyacrylic acid (PAA), but is not limited thereto.

[0050] The embodiments of this application may employ conventional positive current collectors in the art, for example, positive current collectors may include aluminum foil.

[0051] In this embodiment, the positive electrode sheet can be prepared by a coating method. Specifically, the positive electrode active material, positive electrode conductive agent, positive electrode binder, first solid electrolyte, and other components used to form the positive electrode active layer can be dispersed in a positive electrode solvent, such as N-methylpyrrolidone (NMP), to prepare a positive electrode slurry. The first active layer and the second active layer can be prepared by sequentially preparing the first positive electrode slurry and the second positive electrode slurry according to the steps described above. Then, the slurry is coated onto the surface of the positive electrode current collector using a conventional double-layer coating method. After drying, rolling, and other processes, the positive electrode sheet is obtained. The coating, drying, and rolling processes involved are conventional operations for preparing positive electrode sheets using the coating method and are not particularly limited thereto.

[0052] In some embodiments, the porosity and ionic conductivity of the first and second active layers can be controlled by adjusting the types and mass ratios of the positive electrode active material, solid electrolyte, conductive agent, and binder in the first and second active layers, or by adjusting the particle size D of the positive electrode active material and solid electrolyte in the first and second active layers. v 50 is used to regulate the porosity and ionic conductivity of the first and second active layers.

[0053] This invention also provides a battery, including the above-mentioned positive electrode sheet. The battery can be any one of a single cell, a battery module, and a battery pack. The battery has advantages corresponding to the above-mentioned positive electrode sheet, which will not be elaborated further.

[0054] In some embodiments, the battery described above includes a solid-state battery.

[0055] Specifically, when the battery is a single cell, it generally includes a cell and a casing for encapsulating the cell. The cell includes a positive electrode, a negative electrode, and a solid electrolyte membrane located between the positive and negative electrodes. The solid electrolyte membrane includes a second solid electrolyte. The cell can be a stacked cell, meaning it is composed of alternating layers of a positive electrode, a solid electrolyte membrane, and a negative electrode.

[0056] Specifically, the solid electrolyte (second solid electrolyte) in the solid electrolyte membrane may include one or more of the following: sulfide solid electrolyte (or sulfide ion conductor, sulfide-type solid electrolyte) and oxide solid electrolyte (oxide solid ion conductor).

[0057] The solid electrolyte in the positive electrode (first solid electrolyte) and the solid electrolyte in the solid electrolyte membrane (second solid electrolyte) can be the same or different.

[0058] In general, the solid electrolyte membrane in this application can be prepared by conventional methods in the art, such as by pressing a second solid electrolyte into a pressing mold (or solid battery mold) to obtain a solid electrolyte membrane.

[0059] In this embodiment of the invention, conventional negative electrode sheets in the art can be used, and there are no particular limitations. Specifically, the negative electrode sheet includes a negative current collector and a negative active layer located on at least one side surface of the negative current collector. Specifically, the negative active layer can be provided on one side surface of the negative current collector, or negative active layers can be provided on both opposite sides of the negative current collector in the thickness direction.

[0060] Specifically, the negative electrode active layer may include a negative electrode active material, a negative electrode conductive agent, and a negative electrode binder, all of which can be conventional materials in the art. For example, the negative electrode active material may include graphite; the negative electrode conductive agent may include one or more of conductive carbon black, carbon nanotubes (CNT), acetylene black, graphene, Ketjen black, and carbon fiber, with carbon fiber including vapor-grown carbon fiber (VGCF); the negative electrode binder may include one or more of sodium carboxymethyl cellulose (CMC), styrene-butadiene rubber (SBR), polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, ethylene oxide-containing polymers, polyvinylpyrrolidone, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, polyamide-imide, polyvinyl alcohol, and sodium polyacrylate.

[0061] In addition, the negative electrode active layer may also include a third solid electrolyte, which may include a sulfide solid electrolyte and / or an oxide solid electrolyte.

[0062] In this embodiment of the invention, the solid electrolytes in any two of the positive electrode, negative electrode, and solid electrolyte membrane can be the same or different, that is, any two of the first solid electrolyte, second solid electrolyte, and third solid electrolyte can be the same or different.

[0063] The embodiments of this application may employ conventional negative electrode current collectors in the art, for example, negative electrode current collectors may include copper foil.

[0064] In this embodiment, the negative electrode sheet can be prepared by conventional methods in the art, such as by coating. Specifically, components used to form the negative electrode coating, such as the negative electrode active material, negative electrode conductive agent, negative electrode binder, and third solid electrolyte, can be dispersed in a negative electrode solvent, such as water, to prepare a negative electrode slurry. This slurry is then coated onto the surface of the negative electrode current collector, and after drying, rolling, and other processes, the negative electrode sheet is obtained. The coating, drying, and rolling processes involved are conventional operations for preparing negative electrode sheets using the coating method, and are not particularly limited thereto.

[0065] The embodiments of this application can be prepared by conventional methods in the art. For example, positive electrode, solid electrolyte membrane and negative electrode can be stacked alternately to obtain a stacked cell. Then the cell is placed in a casing and after conventional processes such as encapsulation, standing, formation and capacity testing, a single cell is obtained.

[0066] Specifically, when the battery is a battery module or battery pack, the battery includes at least two interconnected individual cells. The battery module and battery pack have advantages corresponding to the positive electrode mentioned above, which will not be elaborated further.

[0067] Generally, battery modules and battery packs comprise multiple batteries, which are connected as individual cells to form battery modules or battery packs. These batteries can be electrically connected using methods conventional in the art, such as series connection, parallel connection, or a hybrid connection including both of these methods, without particular limitation.

[0068] This invention also provides an electrical device including the battery described above. This electrical device has advantages corresponding to the positive electrode plate described above, which will not be elaborated further.

[0069] The electrical equipment used in the embodiments of the present invention can be conventional electrical equipment in the art, such as power equipment (e.g., electric vehicles, electric cars), electronic equipment (e.g., mobile phones, tablets, laptops, digital cameras, etc.), wearable devices (e.g., watches, bracelets, VR glasses, etc.), energy storage power stations, etc., and there are no particular limitations on this.

[0070] The present invention will be further described below through specific embodiments.

[0071] Example 1

[0072] 1. Preparation of positive electrode sheet

[0073] 90 wt% of NCM811 ternary cathode material (Ni, Co, Mn molar ratio of 8:1:1), 8 wt% of LPSCl sulfide solid electrolyte, 1 wt% of NBR, and 1 wt% of VGCF, i.e., the mass ratio of NCM811, LPSCl, NBR, and VGCF is 90:8:1:1, are added to the solvent NMP and stirred thoroughly to form the first cathode slurry. 80 wt% of NCM811 ternary cathode material, 18 wt% of LPSCl, 1 wt% of NBR, and 1 wt% of VGCF, i.e., the mass ratio of NCM811, LPSCl, NBR, and VGCF is 80:18:1:1, are added to the solvent NMP and stirred thoroughly to form the second cathode slurry.

[0074] The first positive electrode slurry and the second positive electrode slurry are coated on the front and back surfaces of the aluminum foil using a double-layer coating method. After drying, rolling, cutting and other processes, the positive electrode sheet is obtained. The thickness d1 of the first active layer is 20 μm and the thickness d2 of the second active layer is 80 μm.

[0075] 2. Battery assembly

[0076] A lithium indium alloy negative electrode sheet was placed in a mold with a diameter of 1 cm, then 100 mg of LPSCl sulfide solid electrolyte powder was placed in the mold and pressed under a pressure of 70 MPa. Then, a positive electrode sheet was placed in the mold and pressed under a pressure of 300 MPa to obtain a mold battery.

[0077] The above-mentioned production process is carried out in an inert atmosphere glove box with a water content of <1ppm and an oxygen content of <1ppm.

[0078] Example 2

[0079] The difference from Example 1 is that in the preparation of the positive electrode, the mass ratio of NCM811, LPSCl, SBR, and SuperP in the first positive electrode slurry is 85:13:1:1, and the mass ratio of NCM622 (Ni, Co, and Mn in a molar ratio of 6:2:2), LPSCl, SBR, and SuperP in the second positive electrode slurry is 80:18:1:1; the thickness d1 of the first active layer is 40 μm, the thickness d2 of the second active layer is 40 μm, and the remaining conditions and steps are the same as in Example 1, as detailed in Table 1.

[0080] Example 3

[0081] The difference from Example 1 is that in the preparation of the positive electrode, the mass ratio of NCM811, LPSBr, HNBR, and VGCF in the first positive electrode slurry is 82:16:1:1, and the mass ratio of NCM811, LPSBr, NBR, and VGCF in the second positive electrode slurry is 76:18:1:5; the thickness d1 of the first active layer is 30 μm, and the thickness d2 of the second active layer is 60 μm. The remaining conditions and steps are the same as in Example 1, as detailed in Table 1.

[0082] Example 4

[0083] The difference from Example 1 is that in the preparation of the positive electrode, the mass ratio of NCM811, LPSCl, HNBR, and SuperP in the first positive electrode slurry is 92:6:1:1, and the mass ratio of NCM811, LPSCl, SBR, and SuperP in the second positive electrode slurry is 83:12:2:3; the thickness d1 of the first active layer is 20 μm, and the thickness d2 of the second active layer is 50 μm. The remaining conditions and steps are the same as in Example 1, as detailed in Table 1.

[0084] Example 5

[0085] The difference from Example 1 is that in the preparation of the positive electrode, the mass ratio of NCM622, LPSCl, NBR, and SuperP in the first positive electrode slurry is 84:12:1.5:2.5, and the mass ratio of NCM523 (Ni, Co, and Mn in a molar ratio of 5:2:3), LPSCl, SBR, and SuperP in the second positive electrode slurry is 80:13:3:4; the thickness d1 of the first active layer is 30 μm, the thickness d2 of the second active layer is 30 μm, and the remaining conditions and steps are the same as in Example 1, as detailed in Table 1.

[0086] Example 6

[0087] The difference from Example 1 is that in the preparation of the positive electrode, the mass ratio of NCM811, LPSCl, and SuperP in the first positive electrode slurry is 85:12:1:2, and the mass ratio of NCM622, LPSBr, HNBR, and SuperP in the second positive electrode slurry is 80:16:1:3; the thickness d1 of the first active layer is 50 μm, the thickness d2 of the second active layer is 50 μm, and the remaining conditions and steps are the same as in Example 1, as detailed in Table 1.

[0088] Example 7

[0089] The difference from Example 1 is that in the preparation of the positive electrode, the mass ratio of NCM811, LPSCl, HNBR, and SuperP in the first positive electrode slurry is 88:10:1:1, and the mass ratio of NCM622, LPSCl, HNBR, and SuperP in the second positive electrode slurry is 82:16:1:1; the thickness d1 of the first active layer is 30 μm, and the thickness d2 of the second active layer is 60 μm. The remaining conditions and steps are the same as in Example 1, as detailed in Table 1.

[0090] Example 8

[0091] The difference from Example 1 is that in the preparation of the positive electrode, the mass ratio of NCM811, LPSBr, NBR, and VGCF in the first positive electrode slurry is 84:14.5:1:0.5, and the mass ratio of NCM622, LPSBr, NBR, and SuperP in the second positive electrode slurry is 80:18.5:1:0.5; the thickness d1 of the first active layer is 40 μm, and the thickness d2 of the second active layer is 50 μm. The other conditions and steps are the same as in Example 1, as detailed in Table 1.

[0092] Example 9

[0093] The difference from Example 1 is that in the preparation of the positive electrode, the mass ratio of NCM811, LPSBr, NBR, and VGCF in the first positive electrode slurry is 83:16:0.5:0.5, and the mass ratio of NCM811, LPSBr, NBR, and SuperP in the second positive electrode slurry is 88:11:0.5:0.5; the thickness d1 of the first active layer is 20 μm, and the thickness d2 of the second active layer is 40 μm. The other conditions and steps are the same as in Example 1, as detailed in Table 1.

[0094] Example 10

[0095] The difference from Example 1 is that in the preparation of the positive electrode, the mass ratio of NCM811, LPSBr, NBR, and VGCF in the first positive electrode slurry is 88:11.5:1:0.5, and the mass ratio of NCM811, LPSBr, NBR, and SuperP in the second positive electrode slurry is 82:16:1:1; the thickness d1 of the first active layer is 30 μm, and the thickness d2 of the second active layer is 20 μm. The other conditions and steps are the same as in Example 1, as detailed in Table 1.

[0096] Comparative Example 1

[0097] The difference from Example 1 is that in the preparation of the positive electrode, the mass ratio of NCM811, LPSCl, NBR, and VGCF in the first positive electrode slurry is 90:8:1:1, and the mass ratio of NCM811, LPSCl, NBR, and VGCF in the second positive electrode slurry is 80:18:1:1; the thickness d1 of the first active layer is 60 μm, and the thickness d2 of the second active layer is 20 μm. The remaining conditions and steps are the same as in Example 1, as detailed in Table 1.

[0098] Comparative Example 2

[0099] The difference from Example 1 is that in the preparation of the positive electrode, the mass ratio of NCM811, LPSCl, SBR, and SuperP in the first positive electrode slurry is 82:15:1:2, and the mass ratio of NCM811, LPSCl, SBR, and SuperP in the second positive electrode slurry is 87:9:1:3; the thickness d1 of the first active layer is 50 μm, the thickness d2 of the second active layer is 50 μm, and the remaining conditions and steps are the same as in Example 1, as detailed in Table 1.

[0100] Comparative Example 3

[0101] The difference from Example 1 is that in the preparation of the positive electrode sheet, the mass ratio of NCM811, LPSCl, NBR, SBR, and SuperP in the first positive electrode slurry is 86:10:1:1:2, and the mass ratio of NCM523, LPSCl, NBR, SBR, and SuperP in the second positive electrode slurry is 82:15:1:1:1; the thickness d1 of the first active layer is 70 μm, and the thickness d2 of the second active layer is 20 μm. The remaining conditions and steps are the same as in Example 1, as detailed in Table 1.

[0102] Comparative Example 4

[0103] The difference from Example 1 is that in the preparation of the positive electrode, the mass ratio of NCM811, LPSCl, SBR, and SuperP in the first positive electrode slurry is 80:10:5:5, and the mass ratio of NCM811, LPSCl, SBR, and SuperP in the second positive electrode slurry is 75:15:5:5; the thickness d1 of the first active layer is 80 μm, the thickness d2 of the second active layer is 80 μm, and the remaining conditions and steps are the same as in Example 1, as detailed in Table 1.

[0104] Comparative Example 5

[0105] The difference from Example 1 is that in the preparation of the positive electrode, the mass ratio of NCM811, LPSCl, SBR, and SuperP in the first positive electrode slurry is 93:5:1:1, and the mass ratio of NCM811, LPSCl, SBR, and SuperP in the second positive electrode slurry is 87:11:1:1; the thickness d1 of the first active layer is 20 μm, and the thickness d2 of the second active layer is 80 μm. The remaining conditions and steps are the same as in Example 1, as detailed in Table 1.

[0106] The positive electrode's d1, d2, σ1, σ2, ρ1, ρ2, particle size of the positive electrode active material, and particle size D of the solid electrolyte. v The test method for 50 is as described above and will not be repeated here. The results are shown in Table 1.

[0107] The first-cycle discharge capacity and rate performance of the batteries in each embodiment and comparative example were tested according to the following procedure, and the results are shown in Table 1.

[0108] (1) Battery first discharge capacity test: Take the mold battery prepared above, apply a pressure of 20 MPa to the battery, charge it at 0.1C to 3.7V at room temperature (25℃), charge it at a constant voltage of 3.7V until the charging current is less than or equal to 0.05C. After standing for 10 minutes, discharge it at 0.1C to 2.0V, and record the discharge capacity at this time as the battery first discharge capacity.

[0109] (2) Battery rate performance (rate charging capacity retention rate) test: Apply a pressure of 20 MPa to the battery and charge it to 3.7V at room temperature (25℃) at 0.1C. Then charge it at a constant voltage of 3.7V until the current is less than or equal to 0.05C. Then discharge it to 2.0V at 0.1C. Record the 0.1C charging capacity as C0. Then charge it to 3.7V at 0.2C and then discharge it to 2.0V at 0.1C. Then charge it to 3.7V at 0.33C and then discharge it to 2.0V at 0.1C. Then charge it to 3.7V at 0.5C and then discharge it to 2.0V at 0.1C. Record the 0.5C charging capacity as C1. The 0.5C charging capacity retention rate is C1 / C0×100%.

[0110] Table 1. Parameters of the positive electrode and battery performance

[0111]

[0112] Compared to Comparative Examples 1-5, the positive electrode sheets in Examples 1-10 satisfy the following: It can simultaneously improve the rate performance and capacity of the battery.

[0113] Finally, it should be noted that other embodiments of the invention will readily occur to those skilled in the art upon consideration of the specification and practice of the invention disclosed herein. This invention is intended to cover any variations, uses, or adaptations of the invention that follow the general principles of the invention and include common knowledge or customary techniques in the art not disclosed herein, and is not limited to what has been described above. Various modifications and changes can be made without departing from its scope. The scope of the invention is limited only by the appended claims.

Claims

1. A positive electrode plate, characterized in that, The cathode includes a positive current collector and a positive active layer located on at least one side of the positive current collector. The positive active layer includes a first active layer and a second active layer located on the side of the first active layer opposite to the positive current collector. The positive electrode sheet satisfies the following: ， Wherein, d1 is the thickness of the first active layer in μm, d2 is the thickness of the second active layer in μm, σ1 is the ionic conductivity of the first active layer in mS / cm, σ2 is the ionic conductivity of the second active layer in mS / cm, ρ1 is the porosity of the first active layer in % and ρ2 is the porosity of the second active layer in % 2. The positive electrode sheet according to claim 1, characterized in that, d1 is 20μm~50μm; preferably, d1 is 30μm~50μm.

3. The positive electrode sheet according to claim 1 or 2, characterized in that, d2 is 20μm~80μm; preferably, d2 is 30μm~80μm.

4. The positive electrode sheet according to any one of claims 1-3, characterized in that, σ1 is 0.01 mS / cm to 0.1 mS / cm; preferably, σ1 is 0.02 mS / cm to 0.1 mS / cm. And / or, σ2 is 0.02mS / cm~0.11mS / cm.

5. The positive electrode sheet according to any one of claims 1-4, characterized in that, ρ1 is 19%~28%; And / or, ρ2 is 23%~35%.

6. The positive electrode sheet according to any one of claims 1-5, characterized in that, The ratio of d2 to d1 is greater than or equal to 1.

7. The positive electrode sheet according to any one of claims 1-6, characterized in that, The first active layer and the second active layer each independently include a positive electrode active material and a solid electrolyte.

8. A battery, characterized in that, The battery includes the positive electrode sheet according to any one of claims 1-7, wherein the battery is any one of a single cell, a battery module, and a battery pack.

9. The battery according to claim 8, characterized in that, The battery includes a solid-state battery.

10. An electrical appliance, characterized in that, Includes the battery as described in claim 8 or 9.

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