A positive electrode sheet, a battery, and an electric device

Abstract

The embodiment of the application provides a positive electrode sheet, a battery and a power utilization device, the positive electrode sheet comprises a current collector and a positive electrode material layer, the positive electrode material layer is arranged on at least one side of the current collector; the positive electrode material layer comprises a positive electrode active material, a solid-state electrolyte, a lithium salt and a binder; in the positive electrode material layer, the mass content of the solid-state electrolyte is W1%, the mass content of the lithium salt is W2%, and the mass content of the binder is W3%; the D50 of the solid-state electrolyte is D mu m; the positive electrode sheet satisfies the following relationship: 0.4 <= <= 3. Through the content and particle size of the solid-state electrolyte, the content of the lithium salt and the binder satisfy the relationship, a highly optimized ion transmission network is formed in the positive electrode material layer, so that the positive electrode sheet has higher ion conductivity, more excellent rate performance and more stable positive electrode interface; further, the solid-state lithium ion battery has lower polarization, releases higher capacity and has excellent cycle performance.

Description

Technical Field

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

[0002] Lithium-ion batteries, as core energy storage devices in the new energy field, are widely used in power batteries, energy storage batteries, and other scenarios. Improving their performance and optimizing their manufacturing processes have always been key research areas in the industry. The cathode, as a crucial component of lithium-ion batteries, undertakes the core functions of lithium-ion insertion / extraction, electron transport, and energy conversion. Its ionic conductivity directly determines the battery's rate performance and cycle stability.

[0003] Currently, lithium-ion battery cathode sheets are typically prepared by coating a mixture of cathode active material, conductive agent, binder, and necessary additives onto the surface of the current collector. Existing technologies mainly improve the ionic conductivity of cathode sheets through optimization of conductive agents, but the oxygen-containing functional groups on the surface of conventional carbon conductive agents can accelerate the decomposition of solid electrolytes, increase the internal resistance of the battery, and affect the electrochemical performance of the battery.

[0004] Therefore, there is an urgent need to develop a positive electrode with high ionic conductivity to improve the rate performance and cycle performance of batteries. Summary of the Invention

[0005] This application provides a positive electrode, a battery, and an electrical device, aiming to improve the ionic conductivity of existing positive electrode to enhance the rate performance and cycle performance of the battery.

[0006] In a first aspect, this application provides a positive electrode sheet, including a current collector and a positive electrode material layer, wherein the positive electrode material layer is disposed on at least one side of the current collector; the positive electrode material layer includes a positive electrode active material, a solid electrolyte, a lithium salt, and a binder; In the positive electrode material layer, the mass content of the solid electrolyte is W1%, the mass content of the lithium salt is W2%, and the mass content of the binder is W3%; the D50 of the solid electrolyte is Dμm. The positive electrode plate satisfies the following relationship: 0.4≤ ≤3.

[0007] In this application, the solid electrolyte exhibits high ionic conductivity, constructing a continuous and efficient lithium-ion transport pathway between and around the positive electrode active material particles. The addition of lithium salt during the fiberization process of the electrode preparation embeds it onto the fiber surface of the binder, forming an interface modification layer that assists ion transport and fills the gaps between the positive electrode active materials, thereby improving ion transport in the composite positive electrode. The content and particle size of the solid electrolyte, and the contents of the lithium salt and binder, satisfy 0.4 ≤ With a concentration of ≤3, the addition of binder and lithium salt is synergistically optimized with the content and particle size of solid electrolyte. This forms a highly optimized ion transport network inside the cathode material layer, resulting in a cathode electrode with higher ion conductivity, better rate performance, and a more stable cathode interface. Furthermore, this enables solid-state lithium-ion batteries to have lower polarization, release higher capacity, and exhibit excellent cycle performance.

[0008] Optionally, the mass content W1% of the solid electrolyte is 5%-20%. By limiting the mass content W1% of the solid electrolyte to between 5% and 20%, a continuous and efficient ion transport network is formed in the cathode material layer, thereby significantly improving the lithium-ion transport rate. Simultaneously, this range avoids the dilution effect of excessive solid electrolyte content on the cathode active material, ensuring that the energy density of the electrode is not significantly affected. Furthermore, an appropriate amount of solid electrolyte also helps maintain the structural stability of the cathode material layer, preventing increased electrode brittleness or processing difficulties caused by excessive solid electrolyte. By controlling W1% within this specific range, the cathode sheet can better satisfy the aforementioned relationship, thereby maintaining high ionic conductivity while preserving the structural stability and energy density of the electrode, thus optimizing the overall performance of the cathode sheet.

[0009] Optionally, the D50 of the solid electrolyte is 0.1-4 μm. By limiting the D50 of the solid electrolyte to a specific range, this application ensures uniform dispersion and close packing of solid electrolyte particles in the cathode material layer. This optimized particle size distribution allows the solid electrolyte particles to effectively fill the gaps between cathode active material particles, forming a continuous and efficient ion conduction network. Simultaneously, an appropriate D50 avoids interruptions in ion transport paths due to excessively large particles, and also avoids agglomeration or excessive binder requirements that may result from excessively small particles, thereby reducing interfacial impedance. This particle size control, along with the synergistic effect of the mass content and overall relationship of each component (cathode active material, lithium salt, binder) in the cathode material layer, jointly promotes the rapid migration of lithium ions within the cathode material layer, significantly improving the ionic conductivity of the cathode sheet.

[0010] Optionally, the mass content W2% of the lithium salt is 1%-10%. Limiting the mass content range of the lithium salt ensures that it provides sufficient ion carriers while avoiding negative impacts on other key components of the cathode material layer. This precise content control, combined with the mass content of the solid electrolyte and binder, and the D50 of the solid electrolyte, allows the cathode sheet to satisfy the relevant relationships, achieving an optimal balance between ionic conductivity, mechanical stability, and electrochemical stability, significantly improving the overall performance of the cathode sheet.

[0011] Optionally, the binder content W3% is 0.5%-3% by mass. By controlling the binder content within the range of 0.5%-3%, it is ensured that the cathode material layer has sufficient mechanical strength to resist stress during charging and discharging, while maintaining open ion transport channels, allowing lithium ions to migrate efficiently in the network composed of solid electrolyte and lithium salt. This precise content control enables the cathode sheet to achieve excellent ion transport performance while maintaining structural integrity, thereby providing the battery with stable electrochemical cycling and high-rate charge-discharge capability.

[0012] Optionally, the positive electrode active material includes a positive electrode active material and a solid electrolyte coating layer, wherein the solid electrolyte coating layer coats the surface of the positive electrode active material. By forming a solid electrolyte coating layer on the surface of the positive electrode active material, a continuous and efficient ion transport channel is established between the positive electrode active material and the solid electrolyte in the positive electrode material layer. This solid electrolyte coating layer, acting as an intermediate interface layer, effectively reduces the interfacial impedance between the positive electrode active material and other components in the positive electrode material layer. Because the coating layer is directly and tightly attached to the surface of the positive electrode active material, it can compensate for the problems of insufficient interfacial contact, local voids, or uneven contact that may exist in traditional mixing methods, thereby significantly improving the transport efficiency of lithium ions between the positive electrode active material and the solid electrolyte. This structural optimization not only ensures rapid ion migration within the solid electrolyte but also solves the transport bottleneck at the interface, making the ion transport path within the entire positive electrode material layer smoother, thereby improving the overall electrochemical performance of the positive electrode sheet.

[0013] Optionally, the thickness of the solid electrolyte coating layer is 10-50 nm. Controlling the thickness of the solid electrolyte coating layer to 10-50 nm ensures that the coating layer fully covers the surface of the positive electrode active material, providing an effective ion conduction path and protective barrier, while avoiding increased interfacial resistance and performance inhibition of the active material caused by excessive thickness. This optimized coating layer thickness achieves an optimal balance of interfacial impedance between the positive electrode active material and the solid electrolyte, thereby significantly improving the overall ionic conductivity and electrochemical stability of the positive electrode.

[0014] Optionally, the solid electrolyte includes Li a M b X c X' dM is selected from at least one of Ga, Y, In, Mg, Sr, Sc, Sn, Pb, Ti, Zr, Hf, Nb, Ta, W, Fe, Ru, Al, and lanthanide metals; X includes at least one of F, Cl, and Br; X' is selected from at least one of halide ions, N ions, oxygen-containing anion groups, and pseudohalogen anions; 0.5≤a≤5, 0.2≤b≤4, c+d=a+bε, and ε is the weighted average valence of element M; the specific crystal structure and ion conduction mechanism of the above solid electrolyte give it high ionic conductivity and chemical stability, which can further improve the ionic conductivity of the positive electrode.

[0015] And / or, the lithium salt includes at least one of lithium hexafluorophosphate, lithium bis(trifluoromethanesulfonyl)imide, lithium bis(trifluoromethanesulfonyl)imide, lithium bis(oxalateborate), lithium bis(fluorooxalateborate), lithium tetrafluoroborate, lithium perchlorate, and lithium hexafluoroarsenate; the above lithium salts have high ionic conductivity and good electrochemical stability, thereby improving the ionic conductivity of the positive electrode.

[0016] And / or, the binder comprises at least one of polytetrafluoroethylene, polytetrafluoroethylene derivatives, polyvinylidene fluoride (PVDF), styrene-butadiene rubber (SBR), hydrogenated nitrile butadiene rubber (HNBR), polystyrene acrylate (PAA), carboxymethyl cellulose (CMC), polyamide (PAI), polyvinyl alcohol (PVA), polyethyleneimine (PEI), polyimide (PI), polyvinylpyrrolidone (PVP), polymethacrylate (PAMA), and polyethylene oxide (PEO). The above binders exhibit good adhesion, and after fiberization, their aspect ratio is greater than 1, enabling them to better bond the positive electrode active material, solid electrolyte, and lithium salt particles together.

[0017] Secondly, this application provides a battery including the aforementioned positive electrode. By selecting the aforementioned positive electrode, the rate performance and cycle stability of the battery are improved. It should be noted that the battery can be a stacked or wound battery.

[0018] Thirdly, this application provides an electrical device including the battery described above. By using the battery described above, which has high rate performance and good cycle stability, the battery life of the electrical device is improved. Attached Figure Description

[0019] Figure 1 This is an electron microscope image of a cross-section of a positive electrode sheet provided in Embodiment 1 of this application. Detailed Implementation

[0020] To make the technical problems, technical solutions, and beneficial effects solved by this application clearer, the following detailed description is provided in conjunction with embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the scope of this application.

[0021] like Figure 1 As shown, one embodiment of this application provides a positive electrode sheet, including a current collector and a positive electrode material layer, wherein the positive electrode material layer is disposed on at least one side of the current collector; the positive electrode material layer includes a positive electrode active material, a solid electrolyte, a lithium salt, and a binder; In the positive electrode material layer, the mass content of the solid electrolyte is W1%, the mass content of the lithium salt is W2%, and the mass content of the binder is W3%; the D50 of the solid electrolyte is Dμm. The positive electrode plate satisfies the following relationship: 0.4≤ ≤3.

[0022] In this embodiment, the solid electrolyte exhibits high ionic conductivity, constructing a continuous and efficient lithium-ion transport path between and around the positive electrode active material particles. The addition of lithium salt during the fiberization process of the electrode preparation embeds it onto the fiber surface of the binder, forming an interface modification layer that assists ion transport and fills the gaps between the positive electrode active materials, thereby improving ion transport in the composite positive electrode. The content and particle size of the solid electrolyte, and the contents of the lithium salt and binder, satisfy 0.4 ≤ A density of ≤3 achieves synergistic optimization between the amount of binder and lithium salt added, the content of solid electrolyte, and the particle size. This creates a highly optimized ion transport network within the cathode material layer, resulting in higher ion conductivity, superior rate performance, and a more stable cathode interface. Furthermore, this leads to lower polarization, higher capacity release, and excellent cycle performance in solid-state lithium-ion batteries. If the relative content of binder and lithium salt is too low, it may result in insufficient mechanical strength or poor ion conductivity of the cathode material layer; if the relative content is too high, it may increase the proportion of inactive components in the cathode material layer, thereby increasing internal resistance. Simultaneously, the D50 of the solid electrolyte ensures the effectiveness of the ion transport path, avoiding the risks of excessively long transport distances due to excessively large particle size or interfacial side reactions due to excessively small particle size.

[0023] In some embodiments, the mass content W1% of the solid electrolyte is 5%-20%. If W1% is too low, the solid electrolyte may be discontinuously distributed in the cathode material layer, forming a bottleneck for ion transport and thus limiting the rapid migration of lithium ions. If W1% is too high, it may dilute the proportion of the cathode active material, reduce the energy density of the electrode, and may adversely affect the mechanical strength and processing performance of the electrode. By limiting the mass content W1% of the solid electrolyte to between 5% and 20%, a continuous and efficient ion transport network is formed in the cathode material layer, thereby significantly improving the lithium ion transport rate. At the same time, this range avoids the dilution effect of excessive solid electrolyte content on the cathode active material, ensuring that the energy density of the electrode is not significantly affected. In addition, an appropriate amount of solid electrolyte also helps maintain the structural stability of the cathode material layer, preventing increased electrode brittleness or processing difficulties caused by excessive solid electrolyte. By controlling W1% within this specific range, the cathode sheet can better satisfy the aforementioned relationship, thereby maintaining the structural stability and energy density of the electrode while ensuring high ionic conductivity, thus optimizing the overall performance of the cathode sheet.

[0024] Specifically, the mass content of the solid electrolyte includes any one of the following values: 5%, 7%, 9%, 11%, 13%, 15%, 17%, 19%, and 20%, and the range between any two values.

[0025] In some embodiments, the content of characteristic elements in W1 and W2 is tested by inductively coupled plasma atomic emission spectrometry; W3 is detected by thermogravimetric analysis.

[0026] In some embodiments, the D50 of the solid electrolyte is 0.1-4 μm. If the D50 is too large, the solid electrolyte particles may not be able to uniformly fill the voids in the cathode material layer, resulting in discontinuous ion transport paths and increased interfacial resistance. Conversely, if the D50 is too small, the particles may tend to agglomerate, increasing the specific surface area, which may trigger unnecessary side reactions or require more binder to maintain structural stability, while excessive binder may hinder ion transport. By limiting the D50 of the solid electrolyte to a specific range, this application ensures uniform dispersion and close packing of solid electrolyte particles in the cathode material layer. This optimized particle size distribution allows the solid electrolyte particles to effectively fill the voids between cathode active material particles, forming a continuous and efficient ion conduction network. At the same time, an appropriate D50 avoids interruption of ion transport paths due to excessively large particles, and also avoids agglomeration or excessive binder requirements that may be caused by excessively small particles, thereby reducing interfacial resistance. This particle size control, along with the synergistic effect of the mass content and overall relationship of each component (positive electrode active material, lithium salt, binder) in the positive electrode material layer, jointly promotes the rapid migration of lithium ions within the positive electrode material layer, significantly improving the ionic conductivity of the positive electrode sheet.

[0027] Specifically, the D50 of the solid electrolyte includes any single value from 0.1μm, 0.5μm, 1μm, 1.5μm, 2μm, 2.5μm, 3μm, 3.5μm, and 4μm, as well as the range between any two values. D50 is the median particle size, representing the particle diameter at which the cumulative particle size distribution reaches 50%, and can be determined using a laser particle size analyzer.

[0028] In some embodiments, the mass content W2% of the lithium salt is 1%-10%. When the lithium salt content is below 1%, the concentration of mobile lithium ions in the positive electrode material layer may be insufficient, leading to a decrease in ionic conductivity and thus affecting the rate performance of the battery. Conversely, when the lithium salt content is above 10%, excessive lithium salt may interact adversely with the binder or solid electrolyte, such as causing plasticization of the binder or decomposition of the solid electrolyte, thereby increasing the internal resistance of the battery and impairing the long-term stability of the positive electrode material layer. In this embodiment, the mass content range of 1%-10% ensures that the lithium salt provides sufficient ion carriers while avoiding negative impacts on other key components of the positive electrode material layer. This precise content control, combined with the mass content of the solid electrolyte and binder, as well as the D50 of the solid electrolyte, allows the positive electrode sheet to satisfy the relevant formula, thereby achieving an optimal balance between ionic conductivity, mechanical stability, and electrochemical stability, significantly improving the overall performance of the positive electrode sheet.

[0029] Specifically, the mass content of lithium salt includes any one value from 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, and 10%, and the range between two such values.

[0030] In some embodiments, the mass content of the binder W3% is 0.5%-3%. If the binder content is less than 0.5%, the bonding force inside the positive electrode material layer is insufficient, which may lead to particle detachment, thereby weakening the structural stability of the positive electrode sheet. Conversely, if the binder content is higher than 3%, excessive binder may fill the pores inside the positive electrode material layer, forming a dense barrier layer, significantly increasing the resistance of lithium ion transport paths and reducing ionic conductivity. By controlling the mass content of the binder within the range of 0.5%-3%, it is ensured that the positive electrode material layer has sufficient mechanical strength to resist stress during charging and discharging, while maintaining open ion transport channels, allowing lithium ions to migrate efficiently in the network composed of solid electrolyte and lithium salt. This precise content control enables the positive electrode sheet to achieve excellent ion transport performance while maintaining structural integrity, thereby providing the battery with stable electrochemical cycling and high-rate charge-discharge capability.

[0031] Specifically, the mass content of the adhesive includes any one of the following values: 0.5%, 1%, 2%, 3%, and a range between two values.

[0032] In some embodiments, the positive electrode active material includes a positive electrode active material and a solid electrolyte coating layer, wherein the solid electrolyte coating layer coats the surface of the positive electrode active material. By forming a solid electrolyte coating layer on the surface of the positive electrode active material, a continuous and efficient ion transport channel is established between the positive electrode active material and the solid electrolyte in the positive electrode material layer. This solid electrolyte coating layer, acting as an intermediate interface layer, effectively reduces the interfacial impedance between the positive electrode active material and other components in the positive electrode material layer. Because the coating layer is directly and tightly attached to the surface of the positive electrode active material, it can compensate for the problems of insufficient interfacial contact, local voids, or uneven contact that may exist in traditional mixing methods, thereby significantly improving the transport efficiency of lithium ions between the positive electrode active material and the solid electrolyte. This structural optimization not only ensures rapid ion migration within the solid electrolyte but also solves the transport bottleneck at the interface, making the ion transport path within the entire positive electrode material layer smoother, thereby improving the overall electrochemical performance of the positive electrode sheet.

[0033] It should be noted that the solid electrolyte in the solid electrolyte coating layer can be the same as or different from the solid electrolyte in the cathode material layer.

[0034] Specifically, the solid electrolyte coating layer can be coated using atomic layer deposition (ALD) or sol-gel methods.

[0035] In some embodiments, the thickness of the solid electrolyte coating layer is 10-50 nm. If the coating layer is too thin, it may not completely cover the surface of the positive electrode active material, resulting in poor protection or discontinuous ion transport paths. Conversely, if the coating layer is too thick, it significantly increases the transport distance of lithium ions within the coating layer, thereby increasing interfacial resistance and suppressing the performance of the positive electrode active material. Therefore, controlling the thickness of the solid electrolyte coating layer to 10-50 nm ensures that the coating layer can fully cover the surface of the positive electrode active material, providing an effective ion conduction path and protective barrier, while avoiding increased interfacial resistance and performance suppression caused by excessive thickness. This optimized coating layer thickness achieves an optimal balance of interfacial impedance between the positive electrode active material and the solid electrolyte, thereby significantly improving the overall ionic conductivity and electrochemical stability of the positive electrode.

[0036] Specifically, the thickness of the solid electrolyte coating includes any single value from 10 nm, 15 nm, 10 nm, 25 nm, 30 nm, 35 nm, 40 nm, 45 nm, and 50 nm, as well as a range between any two values. The thickness of the coating can be precisely measured and verified using high-resolution transmission electron microscopy (HRTEM) or scanning electron microscopy (SEM).

[0037] In some embodiments, the solid electrolyte in the solid electrolyte coating layer and the solid electrolyte in the cathode material layer each independently include Li a M b X c X' d Wherein, M is selected from at least one of Ga, Y, In, Mg, Sr, Sc, Sn, Pb, Ti, Zr, Hf, Nb, Ta, W, Fe, Ru, Al, and lanthanide metals; X includes at least one of F, Cl, and Br; X' is selected from at least one of halide ions, N ions, oxygen-containing anion groups, and pseudohalo anions; 0.5≤a≤5, 0.2≤b≤4, c+d=a+bε, and ε is the weighted average valence of element M.

[0038] The aforementioned solid electrolytes possess specific crystal structures and ion conduction mechanisms. Among these, element M, acting as a framework or dopant, can modulate the crystal structure and lithium-ion vacancy concentration, thereby influencing the lithium-ion migration pathway and activation energy. Elements X and X', as the primary anions, affect the movement of lithium ions within the crystal lattice through their electronegativity and ionic radius. For example, smaller halide ions may form a more compact lattice, while larger halide ions may provide larger ion channels. Nitrogen ions, oxygen-containing anionic groups, and pseudohalogen anions can further optimize the crystal structure and charge distribution of the solid electrolyte, thereby improving ionic conductivity and chemical stability.

[0039] In some embodiments, the oxygen-containing anionic group includes O 2- S 2- CN - CO3 2- PO4 3- P2O7 4- SO4 2- At least one of the following, the pseudohalogen anion is selected from SCN. - PF6 - NH2 - AlF4 - or BF4 - At least one of them.

[0040] In some embodiments, the halide solid electrolyte is selected from Li₂MnCl₄, Li₂ZnCl₄, Li₂ZrOCl₄, LiYbF₄, LiAlF₄, Li₃YCl₆, Li₃InCl₆, and Li₃InCl₄. 5.5 F 0.5 Li3TaCl6, Li 0.388 Ta 0.238 La 0.475 Cl3, Li6CoCl8, LiYBr 5.7 F 0.3 At least one of LiNbOCl4 and LiTaOCl4.

[0041] In some embodiments, the ionic conductivity of the halide solid electrolyte is greater than 1 mS / cm.

[0042] In some embodiments, the lithium salt includes at least one selected from lithium hexafluorophosphate, lithium bis(trifluoromethanesulfonyl)imide, lithium bis(trifluoromethanesulfonyl)imide, lithium bis(oxalateborate), lithium bis(fluorooxalateborate), lithium tetrafluoroborate, lithium perchlorate, and lithium hexafluoroarsenate. The above lithium salts exhibit high ionic conductivity and good electrochemical stability, thereby improving the ionic conductivity of the positive electrode.

[0043] In some embodiments, the binder includes at least one selected from polytetrafluoroethylene (PTFE), PTFE derivatives, polyvinylidene fluoride (PVDF), styrene-butadiene rubber (SBR), hydrogenated nitrile butadiene rubber (HNBR), polystyrene acrylate (PAA), carboxymethyl cellulose (CMC), polyamide (PAI), polyvinyl alcohol (PVA), polyethyleneimine (PEI), polyimide (PI), polyvinylpyrrolidone (PVP), polymethyl methacrylate (PAMA), and polyethylene oxide (PEO). The above binders exhibit good adhesion, and after fiberization, their aspect ratio is greater than 1, enabling them to better bond the positive electrode active material, solid electrolyte, and lithium salt particles together.

[0044] In some embodiments, the positive electrode material layer further includes a conductive agent, which includes at least one selected from Ketjen black, graphite, hard carbon, soft carbon, carbon nanotubes, graphene, porous carbon, superconducting carbon black, acetylene black, furnace black, and whisker carbon nanotubes. By adding a conductive agent to construct a continuous electron conduction network in the positive electrode sheet, the electron conduction efficiency of the electrode sheet is improved. The types of conductive agents in the positive electrode material layer can be the same or different. For example, graphite and carbon nanotubes can be selected in the positive electrode material layer to ensure both electron conduction efficiency and uniform dispersion of the conductive agent, avoiding performance inconsistencies caused by agglomeration, while also helping to improve bonding strength.

[0045] Furthermore, different types of conductive agents can be combined and used, such as Ketjenblack and carbon nanotubes, carbon nanotubes and graphene, and carbon nanotubes, graphene and porous carbon, to improve electron conduction efficiency and dispersion through synergistic effects.

[0046] In some embodiments, the positive electrode active material includes at least one selected from lithium nickel manganese cobalt oxide, lithium iron manganese phosphate, lithium iron phosphate, lithium manganese oxide, lithium cobalt oxide, lithium nickel oxide, lithium-rich manganese-based oxide, lithium nickel manganese oxide, lithium vanadium phosphate, and lithium vanadium oxide phosphate. By using the above-mentioned active materials in combination, the safety performance and energy density of the battery can be further improved.

[0047] In some embodiments, the positive electrode active material includes at least one of monocrystalline particles and polycrystalline particles. The combined use of monocrystalline and polycrystalline particles further improves the energy density of the battery.

[0048] In some embodiments, the mass content of the positive electrode active material in the positive electrode material layer is 50%-95%, and the content of the conductive agent is 0.1%-10%.

[0049] In a preferred embodiment, the mass content of the positive electrode active material in the positive electrode material layer is 70%-95%, and the content of the conductive agent is 0.1%-5%.

[0050] In some embodiments, the current collector includes one of pure aluminum current collector, porous current collector, composite current collector, and carbon-coated current collector. A suitable current collector can be selected according to different performance requirements.

[0051] One embodiment of this application provides a method for preparing the positive electrode sheet as described above, comprising the following steps: The positive electrode active material, solid electrolyte, lithium salt and conductive agent are mixed, and then a binder is added. The mixture is dispersed at 0-40℃, and then heated to perform fibrillation treatment to obtain a mixture. The mixture is then calendered into a film to obtain the positive electrode film.

[0052] The positive electrode film and the current collector are hot-pressed together to obtain the positive electrode sheet.

[0053] Compared to existing processes, the above preparation method eliminates the need for kneading and mixing; the mixture can be directly processed into a film after fibrillation, improving production efficiency. No solvent is used during the preparation process, and when the solid electrolyte is a chloride solid electrolyte, the halide solid electrolyte does not decompose, maintaining a good crystal structure.

[0054] Specifically, the fibrillation treatment apparatus includes, but is not limited to, at least one of a high-speed planetary mixer, an air jet mill, and a screw extruder, with a fibrillation treatment time of 0.1-24 h and a fibrillation treatment temperature of 40-200 °C, preferably 60-150 °C.

[0055] The calendering temperature is 25-200℃. Preferably, the calendering temperature is 60-150℃. Specifically, the calendering equipment can be a pair of heated rollers or a multi-stage roller system.

[0056] The temperature for hot-pressing the composite membrane with the current collector 1 is 40-200℃, preferably 60-150℃.

[0057] In one embodiment, the mixing temperature of the first active material, the first conductive agent, and the first binder is 0-40°C, preferably 10-35°C; the mixing time is 0.1-24 hours, preferably 0.1-5 hours.

[0058] In a preferred embodiment, the fibrillation treatment temperature is 60-150°C and the treatment time is 0.1-5 hours.

[0059] In a preferred embodiment, the calendering temperature is 60-150°C. The temperature at which the first positive electrode material layer 2 and the current collector 1 are hot-pressed is 40-200°C, preferably 60-150°C.

[0060] One embodiment of this application provides a battery including a positive electrode sheet as described above, or a positive electrode sheet prepared by the above-described preparation method. By selecting the above-described positive electrode sheet, the rate performance and cycle stability of the battery are improved. It should be noted that the battery can be a stacked or wound battery. Specifically, the battery can be a semi-solid-state battery or a solid-state battery.

[0061] The battery also includes a negative electrode and an electrolyte membrane.

[0062] In some embodiments, the negative electrode includes at least one of graphite negative electrode, silicon-carbon negative electrode, lithium metal negative electrode, and alloy negative electrode.

[0063] In some embodiments, the electrolyte membrane includes at least one of oxide solid electrolyte, sulfide solid electrolyte, halide solid electrolyte and polymer electrolyte.

[0064] Polymer electrolytes include, but are not limited to, PEO (polyethylene oxide), PVDF (polyvinylidene fluoride), PVDF-HFP (polyvinylidene fluoride-hexafluoropropylene), PMMA (polymethyl methacrylate), and PAN (polyacrylonitrile).

[0065] In some embodiments, the diaphragm is selected from materials such as polypropylene (PP), polyethylene (PE), and composite membranes thereof. Further, at least one side of the diaphragm is provided with a coating, which includes at least one of oxide solid electrolyte, alkaline oxide, and polymer.

[0066] The oxide solid electrolyte includes at least one of the following: NASICON (sodium fast ion conductor) type solid electrolyte, garnet type solid electrolyte, and perovskite type solid electrolyte. The alkaline oxide includes at least one of alumina, silicon oxide, zirconium oxide, titanium oxide, and boehmite; the polymer includes at least one of polyvinylidene fluoride (PVDF), polyvinylidene fluoride-hexafluoropropylene (PVDF-HFP), polymethyl methacrylate (PMMA), and aramid fiber.

[0067] One embodiment of this application provides an electrical device including the battery described above. By using the battery described above, which has high rate performance and good cycle stability, the battery life of the electrical device is improved. Exemplary examples include, but are not limited to, mobile devices (e.g., mobile phones, laptops, etc.), electric vehicles (e.g., pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks, etc.), electric trains, ships and satellites, energy storage systems, aircraft, and robots.

[0068] The present application will be further illustrated by the following examples.

[0069] Example 1 This embodiment illustrates the positive electrode sheet, positive electrode sheet, and battery disclosed in this application, and includes the following operation steps: 1. Preparation of positive electrode sheet The positive electrode active material is NCM811 coated with Li3InCl6. The positive electrode active material, conductive carbon black, VGCF carbon nanotubes, PTFE binder, Li3InCl6 solid electrolyte, and LiTFSI lithium salt are added to a high-speed mixer in a mass ratio of 80:2.5:2.5:2:10:3. After thorough mixing at below 20°C, the mixture is subjected to high-speed fiberization at 85°C to obtain a fiberized mixture. The mixture is then calendered into a film using a roller press at 100°C until the areal loading of the film reaches 16 mg / cm². 2 .

[0070] The diaphragm and current collector were hot-pressed at 100°C, and then rolled to obtain a compaction density of 3.5 g / cm³.3 The positive electrode plate.

[0071] The cross-sectional SEM morphology of the positive electrode is as follows: Figure 1 As shown.

[0072] 2. Negative electrode plate The negative electrode is a lithium metal negative electrode.

[0073] 3. Electrolyte membrane The electrolyte is a sulfide and halide bilayer electrolyte, with the sulfide in contact with the lithium anode and the halide in contact with the solid composite cathode.

[0074] 4. Battery manufacturing An electrolyte membrane is placed between the positive and negative electrode sheets prepared above. Then, the sandwich structure consisting of the positive electrode sheet, negative electrode sheet and electrolyte membrane is stacked, encapsulated with an aluminum-plastic film, and the battery is obtained after formation.

[0075] Example 2 Example 2 is used to illustrate the positive electrode sheet and battery disclosed in this application, including most of the operating steps in Example 1 above, except that: the positive electrode active material is NCM811 coated with Li3InCl6, and the solid electrolyte is LiNbOCl4.

[0076] Examples 3-22, Comparative Examples 1-4 Examples 3-22 and Comparative Examples 1-4 are used to illustrate the positive electrode sheet and battery disclosed in this application, including most of the operating steps in Example 1 above, except that the formulation in Table 1 is used.

[0077] Comparative Example 5 Comparative Example 5 is used to illustrate the positive electrode sheet and battery disclosed in this application, including most of the operating steps in Example 1, except that the positive electrode active material is uncoated NCM811.

[0078] Comparative Example 6 Comparative Example 6 is used to illustrate the positive electrode and battery disclosed in this application, including most of the operating steps in Example 1, except that: the positive electrode active material is NCM811 coated with Li3InCl6, and the solid electrolyte is Li 1.4 Al 0.4 Ti 1.6 (PO4)3.

[0079] Comparative Example 7 Comparative Example 7 is used to illustrate the positive electrode sheet and battery disclosed in this application, including most of the operating steps in Example 1, except that the positive electrode material layer does not contain a solid electrolyte.

[0080] Comparative Example 8 Comparative Example 8 is used to illustrate the positive electrode sheet and battery disclosed in this application, including most of the operating steps in Example 1, except that the positive electrode material layer does not contain lithium salt.

[0081] Table 1 Performance testing I. The following performance tests were performed on the positive electrode sheets and batteries prepared in the above embodiments and comparative examples: 1. Positive Electrode Ionic Conductivity: The room temperature ionic conductivity of the composite positive electrode was tested using electrochemical impedance spectroscopy (EIS) in conjunction with an electron-blocking symmetrical cell. The specific steps are as follows: In a glove box with water and oxygen content <0.1 ppm, the positive electrodes prepared in the examples and comparative examples were cut into circular pieces with an area of ​​S, and their thickness was measured to be L. This electrode was placed between two pure solid electrolyte layers (electro-insulating layers) of uniform thickness, and stainless steel wafers were attached to both sides as blocking electrodes, assembling a symmetrical cell sample. The sample was placed in a test mold and a set constant pressure (e.g., 250 MPa) was applied. The assembled test sample was placed in a 25°C constant temperature chamber and allowed to stand for 2 hours. Electrochemical impedance spectroscopy was performed using an electrochemical workstation, with the AC perturbation voltage amplitude set to 10 mV and the scanning frequency range from 1 MHz to 0.1 Hz. Under the same conditions, the background ionic impedance of the two pure solid electrolyte layers was measured separately and recorded as R0. The total ionic impedance R1 of the test sample was obtained by fitting the test spectrum using an equivalent circuit. The ionic conductivity of the composite positive electrode is calculated using the following formula: σ = L / (R1-2R0) / S.

[0082] 2. Cyclic test: The first cycle is performed at a rate of 0.05C, followed by a charge-discharge cycle test at 0.1C. The first cycle discharge capacity and capacity retention rate after 100 cycles of the example and comparative batteries are recorded.

[0083] Specifically, the charge-discharge cycle test involves charging at 0.1C to 4.3V at 25°C, discharging at 0.1C, and discharging to 2.8V.

[0084] 3. Rate performance test: The cells prepared in the examples and comparative examples were subjected to constant current charge and discharge for 3 cycles at rates of 0.1C, 0.5C, 1C and 3C, with a charge and discharge voltage range of 2.8-4.3V. The capacity retention rate at the 3C rate was recorded.

[0085] The test results are shown in Table 2.

[0086] Table 2 Figure 1The cross-sectional SEM image of Example 1 shows that sheet-like halide solid electrolytes are uniformly distributed around the positive electrode particles. Simultaneously, strip-shaped whisker-like carbon nanotubes and a fine filament network of binders are also visible.

[0087] As shown in Table 2, the test results of Examples 1-22 and Comparative Examples 5-8 indicate that when the positive electrode material layer does not contain a solid electrolyte or when no solid electrolyte coating layer is provided around the positive electrode active material, the ionic conductivity of the electrode decreases significantly, the capacity release decreases significantly, and the cycle performance and rate performance deteriorate. When the positive electrode material layer does not contain lithium salt, the ionic conductivity of the electrode decreases, and the capacity, cycle performance, and rate performance of the battery cell decrease. The solid electrolyte selected in the positive electrode material layer is Li. 1.4 Al 0.4 Ti 1.6 When Li is used instead of the halide solid electrolyte of this application, Li 1.4 Al 0.4 Ti 1.6 The ionic conductivity of (PO4)3 is insufficient, lower than that of halide solid electrolytes. The ionic conductivity of composite electrodes decreases, resulting in lower first-cycle discharge capacity and reduced cycle and rate performance.

[0088] The test results of Examples 1-22 and Comparative Examples 1-4 show that the formula 0.4 ≤ The positive electrode prepared in examples ≤3 exhibits higher ionic conductivity, higher first-cycle discharge capacity, and better rate and cycle performance. Furthermore, the test results of Examples 1-18 show that when the mass content of the solid electrolyte W1% is 5%-20%, D50 is 0.1-4 μm, the mass content of the lithium salt W2% is 1%-10%, and the mass content of the binder W3% is 0.5%-3%, the positive electrode has good ionic conductivity, and the battery has good cycle and rate performance. The test results of Examples 1 and Examples 19-22 show that when a solid electrolyte coating layer is provided around the positive electrode active material, and the thickness of the solid electrolyte coating layer is 10-50 nm, the ionic conductivity of the positive electrode is further improved.

[0089] In this application, the term "and / or" is merely a description of the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, A and B existing simultaneously, or B existing alone. Additionally, in this application, the character " / " generally indicates that the preceding and following related objects have an "or" relationship.

[0090] The above description is merely a preferred embodiment of this application and is not intended to limit this application. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. A positive electrode plate, characterized in that, It includes a current collector and a positive electrode material layer, wherein the positive electrode material layer is disposed on at least one side of the current collector; the positive electrode material layer includes a positive electrode active material, a solid electrolyte, a lithium salt, and a binder; In the positive electrode material layer, the mass content of the solid electrolyte is W1%, the mass content of the lithium salt is W2%, and the mass content of the binder is W3%; the D50 of the solid electrolyte is Dμm. The positive electrode plate satisfies the following relationship: 0.4≤ ≤3。 2. The positive electrode sheet according to claim 1, characterized in that, The mass content W1% of the solid electrolyte is 5%-20%.

3. The positive electrode sheet according to claim 1, characterized in that, The solid electrolyte has a D50 of 0.1-4 μm.

4. The positive electrode sheet according to claim 1, characterized in that, The mass content of the lithium salt, W2%, is 1%-10%.

5. The positive electrode sheet according to claim 1, characterized in that, The mass content of the adhesive W3% is 0.5%-3%.

6. The positive electrode sheet according to claim 1, characterized in that, The positive electrode active material includes a positive electrode active substance and a solid electrolyte coating layer, wherein the solid electrolyte coating layer coats the surface of the positive electrode active substance.

7. The positive electrode sheet according to claim 6, characterized in that, The thickness of the solid electrolyte coating layer is 10-50 nm.

8. The positive electrode sheet according to claim 1, characterized in that, The solid electrolyte includes Li a M b X c X' d Wherein, M is selected from at least one of Ga, Y, In, Mg, Sr, Sc, Sn, Pb, Ti, Zr, Hf, Nb, Ta, W, Fe, Ru, Al, and lanthanide metals; X includes at least one of F, Cl, and Br; X' is selected from at least one of halide ions, N ions, oxygen-containing anion groups, and pseudohalo anions; 0.5≤a≤5, 0.2≤b≤4, c+d=a+bε, and ε is the weighted average valence of element M; And / or, the lithium salt includes at least one of lithium hexafluorophosphate, lithium bis(trifluoromethanesulfonyl)imide, lithium bis(trifluoromethanesulfonyl)imide, lithium bis(oxalateborate), lithium bis(fluorooxalateborate), lithium tetrafluoroborate, lithium perchlorate, and lithium hexafluoroarsenate. And / or, the adhesive comprises at least one of polytetrafluoroethylene, polytetrafluoroethylene derivatives, polyvinylidene fluoride, styrene-butadiene rubber, hydrogenated nitrile rubber, polystyrene ester, hydroxymethyl cellulose, polyamide, polyvinyl alcohol, polyethyleneimine, polyimide, polyvinylpyrrolidone, polymethacrylate, and polyethylene oxide.

9. A battery, characterized in that, Including the positive electrode sheet as described in any one of claims 1-8.

10. An electrical device, characterized in that, Includes the battery as described in claim 9.

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