Positive plate and battery

Abstract

The invention relates to the technical field of batteries, in particular to a positive plate and a battery, the positive plate comprises a positive current collector, a functional layer located on the surface of the positive current collector and a positive active material layer located on the surface of the functional layer; the functional layer comprises first lithium conducting particles, and the first lithium conducting particles comprise inorganic oxide particles and solid electrolyte materials coating the surfaces of the inorganic oxide particles; n positive active material particles are arranged on any cross section, perpendicular to the plane of the positive current collector, in the positive active material layer along the thickness direction of the positive current collector; the thickness of the functional layer is Dg, and the unit is mu m; n and Dg satisfy the relational expression: 0.6 < = N / Dg < = 40. By arranging the functional layer containing the first lithium conducting particles, a continuous transverse lithium conducting passage can be formed at the bottom of the active material layer by means of the solid electrolyte coating material of the first lithium conducting particles, the problem of lithium concentration balance among the active material particles at the bottom layer of the positive electrode is effectively solved, and the low-temperature performance of the lithium battery is improved.

Description

Technical Field

[0001] This invention relates to the field of battery technology, specifically to a positive electrode and a battery. Background Technology

[0002] Lithium-ion batteries have been widely used in many fields due to their advantages such as high energy density, long cycle life, high operating voltage, no memory effect, low self-discharge, and environmental friendliness. Currently, the development of lithium battery technology mainly focuses on improving energy density, extending cycle life, enhancing safety, and reducing costs. However, the performance of lithium batteries still faces severe challenges in low-temperature environments.

[0003] The impact of low temperature on lithium-ion transport on the positive electrode side is mainly reflected in changes in the transport path. In the bottom region near the current collector, due to the sharp drop in electrolyte ionic conductivity at low temperatures, lithium ions are transported primarily through the solid-phase network. Simultaneously, the high viscosity of the electrolyte significantly inhibits the lateral (along the current collector plane) migration of lithium ions between adjacent active material particles. This loss of lateral transport capability makes it difficult to achieve local concentration equilibrium at the bottom of the positive electrode active layer through ion migration; in other words, the "lateral lithium balance mechanism" almost fails.

[0004] Currently, conventional current collector coatings (such as ceramics, carbon coatings, or uncoated aluminum foil) lack lateral lithium conduction capabilities, causing lithium intercalation depth gradients among positive electrode active material particles due to differences in their microenvironment. Low temperatures further amplify this inhomogeneity: the sharp drop in electrolyte ionic conductivity blocks the lithium-ion redistribution pathway between particles via the electrolyte. Insufficiently intercalated particles cannot obtain lithium ions from adjacent saturated particles, resulting in the overall lithium intercalation capacity of the positive electrode falling below the theoretical value. This leads to a sharp drop in discharge voltage plateau and significant capacity decay. Summary of the Invention

[0005] To address the aforementioned issues, this invention provides a positive electrode sheet and a battery. The positive electrode sheet of this invention, by setting a functional layer containing first lithium-conducting particles between the positive electrode current collector and the positive electrode active material layer, can form a continuous lateral lithium-conducting path at the bottom of the positive electrode active material layer with the help of the first lithium-conducting particles, effectively improving the lithium concentration balance problem among the active material particles at the bottom of the positive electrode, thereby enhancing the low-temperature performance of the lithium battery.

[0006] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0007] A first aspect of the present invention provides a positive electrode sheet, the positive electrode sheet comprising a positive current collector, a functional layer located on the surface of the positive current collector, and a positive active material layer located on the surface of the functional layer, the functional layer being located between the positive current collector and the positive active material layer;

[0008] The functional layer includes a first lithium-conducting particle, which includes inorganic oxide particles and a solid electrolyte material coated on the surface of the inorganic oxide particles.

[0009] In the positive electrode active material layer, on any cross section perpendicular to the plane of the positive electrode current collector, N positive electrode active material particles are arranged along the thickness direction of the positive electrode current collector; the thickness of the functional layer is Dg, in μm;

[0010] The N and Dg satisfy the following relationship: 0.6≤N / Dg≤40.

[0011] A second aspect of the present invention provides a battery comprising the positive electrode sheet described in the first aspect of the present invention.

[0012] By employing the above technical solution, the present invention has at least the following advantages compared with the prior art:

[0013] Studies have found that by incorporating solid electrolyte materials into the positive electrode active material, it is possible to replace part of the electrolyte and act as a lithium-ion transport channel at low temperatures. However, to completely improve the problem of insufficient and uneven lithium intercalation in the positive electrode active material layer, it is necessary to improve the lithium-ion transport capacity of the bottom layer of the positive electrode active material and form a continuous lithium conduction path in the bottom layer of the positive electrode active material. To form a continuous lithium conduction path, a large amount of solid electrolyte material needs to be incorporated into the positive electrode active material layer. Common solid electrolyte materials are unstable under high voltage, and the metal will slowly dissolve and migrate to the negative electrode to participate in the reaction. Moreover, the increased amount of solid electrolyte material will also lead to higher battery costs. Based on this, the positive electrode sheet of the present invention provides a functional layer containing first lithium-conducting particles between the positive electrode current collector and the positive electrode active material layer. The first lithium-conducting particles include inorganic oxide particles and solid electrolyte material coated on the surface of the inorganic oxide particles. With the help of a small amount of solid electrolyte material on the surface of the first lithium-conducting particles, a continuous lateral lithium-conducting path can be formed at the bottom of the positive electrode active material layer, effectively improving the lithium concentration balance problem among the active material particles at the bottom of the positive electrode and improving the low-temperature performance of the lithium battery. By introducing lithium-conducting particles coated with inorganic oxides by solid electrolyte with a current equalization function, the present invention can reduce the amount of solid electrolyte material used while ensuring the lithium conduction effect. In addition, combined with the functional layer being located at the bottom, the high voltage borne by the solid electrolyte material and its contact with the electrolyte can be reduced, thereby effectively reducing the amount of metal dissolution and hindering the migration of dissolved metal ions to the negative electrode, further improving the low-temperature performance, cycle stability and safety of the lithium battery. Furthermore, an increase in the amount of solid electrolyte material will lead to an increase in the water content in the positive electrode active material layer. Reducing the amount of solid electrolyte material is beneficial to improving the high-temperature performance and safety performance of the battery.

[0014] Furthermore, the inorganic oxide particle core in the first lithium-ion particle coating structure can immobilize PF6 in the electrolyte. - It can neutralize the hydrofluoric acid generated by the electrolyte reaction, thereby slowing down the corrosion of the solid electrolyte material coating structure by the components in the electrolyte, thereby further reducing the metal dissolution of the solid electrolyte and improving the stability of the solid electrolyte during the cycling process.

[0015] Furthermore, the number N of active material particles in the thickness direction of the positive electrode is a key factor affecting low-temperature performance. The thicker the electrode, the more severe the lithium intercalation / deintercalation polarization phenomenon of the bottom layer particles at low temperatures, and the more significant the battery performance degradation. Therefore, for thick electrodes, the thickness (Dg) of the functional layer needs to be increased accordingly to effectively alleviate bottom layer polarization. However, for relatively thin electrodes (small N value), an excessively thick functional layer is not only unhelpful, but may also cause the aforementioned side effects due to the excessive introduction of solid electrolyte material. Based on this, the present invention further controls the ratio between the number N of positive electrode active material particles and the thickness Dg of the functional layer to meet a specific range. By matching the optimal Dg for different N values, the degree of intercalation between the functional layer and the positive electrode active material layer can be increased, thereby further improving the lithium balance problem of the bottom layer of the positive electrode, providing a continuous lithium conduction path, and improving the low-temperature performance and stability of the lithium battery.

[0016] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein. Attached Figure Description

[0017] Figure 1 The figure shown is a schematic cross-sectional view of the positive electrode sheet provided in an embodiment of the present invention.

[0018] Figure 2 The diagram shown is a cross-sectional view of the interface region between the positive electrode active material layer and the functional layer in a positive electrode sheet provided by an embodiment of the present invention. Figure 1 .

[0019] Figure 3 The diagram shown is a cross-sectional view of the interface region between the positive electrode active material layer and the functional layer in a positive electrode sheet provided by an embodiment of the present invention. Figure 2 .

[0020] Figure description: 1 is the positive current collector, 2 is the functional layer, 3 is the positive active material layer, and 4 is the positive electrode tab. Detailed Implementation

[0021] The following provides a detailed description of specific embodiments of the present invention. It should be understood that the specific embodiments described herein are for illustrative and explanatory purposes only and are not intended to limit the invention. Unless otherwise specified herein, data ranges include endpoints.

[0022] It should be noted that the numerical designations such as "first" and "second" in this disclosure are only used to distinguish different substances or methods of use, and do not represent a difference in order.

[0023] Terminology Explanation

[0024] In this invention, the terms "battery", "lithium battery", "lithium-ion battery" and "lithium-ion secondary battery" all have the same meaning and refer to lithium-ion secondary batteries.

[0025] The first aspect of the present invention provides a positive electrode, such as Figure 1 As shown, the positive electrode sheet includes a positive current collector 1, a functional layer 2 located on the surface of the positive current collector 1, and a positive active material layer 3 located on the surface of the functional layer 2. The functional layer 2 is located between the positive current collector 1 and the positive active material layer 3. Figure 1 In one embodiment shown, a positive electrode tab 4 is further disposed on the positive current collector 1 of the positive electrode sheet. The functional layer 2 and the positive active material layer 3 can be located on one or both sides of the positive current collector 1 along the thickness direction of the positive electrode sheet. Figure 1 The diagram shows the functional layer 2 and the positive electrode active material layer 3 located on both sides of the positive electrode current collector 1 along the thickness direction of the positive electrode sheet.

[0026] In this invention, the functional layer 2 includes a first lithium-conducting particle, which comprises inorganic oxide particles and a solid electrolyte material coated on the surface of the inorganic oxide particles. The solid electrolyte material coats the surface of the inorganic oxide particles, forming a first lithium-conducting particle with a coating structure. Because the solid electrolyte material coats the surface of the inorganic oxide particles, when different first lithium-conducting particles come into contact with each other, the solid electrolyte material on the surface preferentially contacts each other, thereby facilitating the formation of a continuous lithium-conducting pathway. Furthermore, the coating structure design can significantly reduce the amount of solid electrolyte material used.

[0027] Research has found that by incorporating solid electrolyte materials into the positive electrode active material, it is possible to replace part of the electrolyte to function as a lithium-ion transport channel at low temperatures. However, common solid electrolyte materials such as Li 1+x Al x Ti 2-x (PO4)3(LATP), Li 1+x Al x Ge 2-x (PO4)3(LAGP), Li 10GeP2S 12 Li6PS5Cl (LPSC) and LiCoO2 (LCO) are unstable under high voltage. 0.8 Co 0.1 Mn 0.1 When high-voltage layered oxide cathode materials such as O2 (NCM811) are mixed in, metals slowly dissolve and migrate to the anode to participate in the reaction. Due to polarization differences in the vertical direction, the surface voltage of the cathode is generally higher further away from the current collector. After mixing with the cathode, metal dissolution in the solid electrolyte in the region far from the current collector increases the SEI film on the anode, reducing thermal stability. Furthermore, the surface layer has high kinetics and is largely unaffected by temperature. Therefore, when the cathode is mixed in the whole, the surface solid electrolyte has little effect and is more prone to decomposition, leading to a decrease in cell performance. Based on this, mixing solid electrolyte materials into the bottom layer of the cathode active material can be considered. However, to completely improve the insufficient and uneven lithium intercalation in the cathode active material layer, a large amount of solid electrolyte material needs to be mixed into the cathode active material layer to form a continuous lithium conduction path in the bottom layer, effectively improving the lithium-ion transport capacity of the bottom layer. However, this mixing method introduces excessive solid electrolyte material, causing a series of problems associated with solid electrolytes at high voltages. Moreover, the increased amount of solid electrolyte material also leads to higher battery costs.

[0028] Based on this, the positive electrode sheet of the present invention provides a functional layer containing first lithium-conducting particles between the positive electrode current collector and the positive electrode active material layer. The first lithium-conducting particles include inorganic oxide particles and solid electrolyte material coated on the surface of the inorganic oxide particles. This allows a continuous lateral lithium-conducting pathway to be formed at the bottom of the positive electrode active material layer by means of a small amount of solid electrolyte material on the surface of the first lithium-conducting particles. This effectively improves the lithium concentration balance problem among the active material particles at the bottom of the positive electrode and enhances the low-temperature performance of the lithium battery. By introducing lithium-conducting particles coated with inorganic oxides by solid electrolyte with a current equalization function, the present invention can reduce the amount of solid electrolyte material used while ensuring the lithium-conducting effect. In addition, the functional layer is located at the bottom layer, which can reduce the high voltage borne by the solid electrolyte material and its contact with the electrolyte, thereby effectively reducing the amount of metal dissolution and hindering the migration of dissolved metal ions to the negative electrode, further improving the low-temperature performance, cycle stability and safety of the lithium battery.

[0029] Furthermore, increasing the amount of solid electrolyte material leads to an increase in the water content in the positive electrode active material layer. This is because during the production process of solid electrolyte, the surface of its particles contains a large amount of bound water, free water, and hydroxyl groups. Although a baking process is performed before liquid injection, it is difficult to completely remove the internal water. Experimental results show that when all solid electrolytes are used to coat a 3μm thick coating and active material is coated on the surface, even after 24 hours of high-temperature baking, the water content of the electrode is still >300ppm, while the uncoated group is around 50ppm. Excessive water content will lead to the deterioration of the high-temperature performance of the cell. This invention, by setting lithium-conducting particles with a coating structure, can effectively reduce the amount of solid electrolyte material used, thereby avoiding an increase in the water content in the coating, which is beneficial to improving the high-temperature performance and safety performance of the battery.

[0030] In summary, the functional layer of this invention can achieve a continuous lithium conduction path, balance the lithium ion insertion depth between different active material particles under low-temperature conditions, thereby improving the problem of uneven current distribution inside the electrode, reducing the risk of local overcharging or over-discharging, and improving the cycle stability and safety of the battery. Compared with the existing technology of mixing, it can achieve a continuous lithium conduction path with a small amount of solid electrolyte, and the coating has a lower water content.

[0031] Furthermore, in addition to the special lithium-conducting effect of the solid electrolyte material on the surface, the inorganic oxide particles in the core of the coating structure of the first lithium-conducting particle of the present invention also have the effect of improving the stability of the solid electrolyte. This is because the inorganic oxide particles in the coating structure of the first lithium-conducting particle can fix PF6 in the electrolyte and neutralize the hydrofluoric acid generated by the electrolyte reaction, thereby slowing down the corrosion of the solid electrolyte material coating structure by the components in the electrolyte, thereby further reducing the metal dissolution of the solid electrolyte and improving the stability of the solid electrolyte during the cycling process.

[0032] Furthermore, in this invention, N positive electrode active material particles are arranged along the thickness direction of the positive electrode current collector 1 on any cross-section of the positive electrode active material layer 3 perpendicular to the plane of the positive electrode current collector 1, such as... Figure 2 and Figure 3 As shown, Figure 2 and Figure 3This is a schematic diagram of the cross-sectional structure of the interface region between the positive electrode active material layer and the functional layer in the positive electrode sheet. As can be seen from the figure, the positive electrode active material particles in the positive electrode active material layer are arranged along the thickness direction of the positive electrode current collector. Specifically, the number N of positive electrode active material particles can be obtained by observing the SEM image of the positive electrode active material layer at the same angle. When obtaining the number N, in order to avoid the problem of uneven thickness at different sites of the positive electrode active material layer, values ​​can be taken from multiple sites, and then the average value of the multiple sites can be calculated, which is the number N. The thickness of the functional layer is Dg, in μm. The thickness of the functional layer can also be obtained by observing the SEM image of the positive electrode active material layer. Similarly, in order to avoid the problem of uneven thickness at different sites of the functional layer, values ​​can be taken from multiple sites, and then the average value of the multiple sites can be calculated, which is the thickness Dg of the functional layer. The N and Dg satisfy the following relationship: 0.6 ≤ N / Dg ≤ 40, for example, 0.6, 0.7, 0.8, 0.9, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, or any two of the above values. In one example, 0.7 ≤ N / Dg ≤ 20.

[0033] The thicker the positive electrode, the more positive active material particles there are. This leads to a greater problem of lithium insertion / extraction polarization at the bottom layer of the electrode under low-temperature conditions, resulting in poorer low-temperature battery performance. Therefore, the lithium insertion / extraction polarization problem at the bottom layer of thick electrodes can be improved by appropriately increasing the thickness of the functional layer. However, electrodes with fewer positive active material particles do not require an excessively thick functional layer, which would lead to an increase in the amount of solid electrolyte material used, thus causing the aforementioned problems. Based on this, this invention further controls the ratio between the number of positive active material particles N and the thickness Dg of the functional layer to meet a specific range, making it applicable to positive electrode sheets of different thicknesses. Furthermore, by matching appropriate functional layer thickness Dg to different numbers of positive active material particles N, the degree of intercalation between the functional layer and the positive active material layer at their interface can be increased. Figure 2 and Figure 3 As shown, the problem of lithium deintercalation polarization and uneven lithium intercalation is more serious in electrodes with thicker positive electrode active material layers. By controlling the N / Dg relationship, the degree of mutual intercalation between the functional layer and the positive electrode active material layer can be further increased, improving the lithium balance problem in the bottom layer of the thick electrode active material, thereby providing a continuous lithium conduction path for the bottom layer of the thick electrode to improve the low-temperature performance and stability of lithium batteries.

[0034] In summary, the positive electrode sheet of the present invention, by placing a functional layer containing a first lithium-conducting particle with a special structure between the positive electrode active material layer and the positive electrode current collector, can more effectively improve the lithium balance problem of the bottom layer of the positive electrode, provide a lateral lithium concentration balance path for the bottom active material, and improve the battery performance at low temperatures. At the same time, placing the functional layer at the bottom layer can reduce the voltage borne by the solid electrolyte, reduce the contact with the electrolyte, and the dissolved metal ions are covered and blocked by the positive electrode active material layer, making it more difficult for them to reach the negative electrode to participate in the reaction, which is conducive to improving battery safety. In addition, by reducing the amount of solid electrolyte, the cost and water content in the coating can also be reduced.

[0035] In this invention, N positive electrode active material particles are arranged along the thickness direction of the positive electrode current collector on any cross-section perpendicular to the plane of the positive electrode current collector in the positive electrode active material layer. In one specific embodiment, 5 ≤ N ≤ 50, for example, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, or 50. In a preferred embodiment, 10 ≤ N ≤ 20. If the number of positive electrode active material particles N is greater than 50, it will exacerbate the lithium imbalance problem at the bottom layer and reduce low-temperature performance. At the same time, if the positive electrode active material layer is too thick, it will accumulate greater internal stress, leading to a decrease in the bonding force between the active layer and the current collector, resulting in problems such as cracking, delamination, or even detachment, which will reduce cycle performance and safety performance. If the number of positive electrode active material particles N is less than 5, it means that the amount of active layer is too small, which will lead to a decline in the cycle performance of the battery.

[0036] In one specific embodiment, based on the total mass of the functional layer, the mass content of the solid electrolyte material is 1%-50%, for example, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5%, 5.5%, 6%, 7%, 8%, 9%, 10%, 15%, 20%, 30%, 35%, 40%, 45%, or 50%. The method for testing the mass content percentage of the solid electrolyte material in the functional layer is as follows: the active material layer is gently scraped away to completely expose the functional layer; XRD (X-ray diffraction analysis) is used to determine the type of solid electrolyte material and characteristic metals in the functional layer; SEM-EDS (scanning electron microscopy-X-ray spectroscopy) is used to determine the content of characteristic elements; and the mass content of the solid electrolyte in the layer is determined according to its molecular formula. In a preferred embodiment, based on the total mass of the functional layer, the mass content of the solid electrolyte material is 3%-20%. If the solid electrolyte material accounts for less than 1% of the total mass, low-temperature lithium equilibrium failure will occur due to the breakage of the lithium conduction pathway. Furthermore, the inorganic oxides, not fully covered by the solid electrolyte material, are susceptible to corrosion by HF, leading to decreased stability. Conversely, if the solid electrolyte material accounts for more than 50% of the total mass, excessive solid electrolyte will exacerbate metal dissolution, increasing the water content of the electrode, deteriorating high-temperature performance, and increasing costs. This invention, by further controlling the solid electrolyte material content within a suitable range, can form a continuous lateral lithium conduction pathway by covering the surface of inorganic oxide particles with an appropriate amount of solid electrolyte material. This effectively improves the lithium concentration equilibrium problem at low temperatures in the bottom layer of the cathode, avoids metal dissolution caused by increased contact area between the solid electrolyte and the electrolyte, and reduces material costs.

[0037] In one specific embodiment, the average thickness of the shell formed by the solid electrolyte material coating the surface of the inorganic oxide particles is 10 nm to 1500 nm, for example, 10 nm, 20 nm, 30 nm, 40 nm, 50 nm, 60 nm, 70 nm, 80 nm, 90 nm, 100 nm, 200 nm, 300 nm, 400 nm, 500 nm, 600 nm, 700 nm, 800 nm, 900 nm, 1000 nm, 1100 nm, 1200 nm, 1300 nm, 1400 nm, 1500 nm, or within any two of the above values. The method for testing the average thickness is as follows: Take a sample (positive electrode sheet), scrape off the positive electrode active material layer on the surface, and continue scraping to obtain the functional layer material. Use a focused ion beam (FIB) to slice the inorganic oxide particles coated with solid electrolyte material in the functional layer material, and then perform SEM testing. In the SEM image at a magnification of 5,000x, arbitrarily select 10 sites on the same particle to be tested, and use Digital Micrograph to measure the thickness of the shell formed by the solid electrolyte material. After removing the maximum and minimum values, take the average value to obtain the average thickness of the shell formed by the solid electrolyte material coating the surface of the inorganic oxide particles. If the shell thickness is less than 500nm or the SEM accuracy is difficult to measure, TEM can be used instead, with a magnification of 50,000-200,000x, and the measurement method is the same as above. In a preferred embodiment, the average thickness of the shell formed by the solid electrolyte material coating the surface of the inorganic oxide particles is 30nm to 300nm. If the thickness is less than 10nm, incomplete coating will lead to breakage in the lithium conduction pathway. Furthermore, an excessively thin shell will result in reduced mechanical strength, making it prone to breakage during rolling and diminishing the improvement in low-temperature performance. Conversely, if the thickness exceeds 1500nm, the internal areas of the shell will be unable to participate in lithium conduction, leading to partial material failure, increased costs, and the first lithium-conducting particles exceeding the optimal particle size range, causing agglomeration and affecting lithium conduction. This invention, by controlling the thickness of the shell formed by the solid electrolyte material coating, can further achieve complete coating of the inorganic oxide particle surface, avoiding lithium conduction breakage, ensuring the surface lithium conduction characteristics of the first lithium-conducting particles, preventing ineffective accumulation and material waste inside the shell, and minimizing material costs.

[0038] In one specific embodiment, the median particle size Dv50 of the first lithium-conducting particle is 0.3 μm to 7 μm, for example, 0.3 μm, 0.4 μm, 0.5 μm, 0.6 μm, 0.7 μm, 0.8 μm, 0.9 μm, 1 μm, 1.2 μm, 1.4 μm, 1.6 μm, 1.8 μm, 2 μm, 2.5 μm, 3 μm, 3.5 μm, 4 μm, 4.5 μm, 5 μm, 5.5 μm, 6 μm, 6.5 μm, or 7 μm. The median particle size Dv50 of the first lithium-conducting particle refers to the particle size corresponding to 50% of the cumulative volume distribution in the particle size distribution, which can be measured by a laser particle size analyzer. In a preferred embodiment, the median particle size Dv50 of the first lithium-conducting particle is 1 μm to 4 μm.

[0039] In one specific embodiment, the specific surface area of ​​the first lithium-conducting particle is 20 m². 2 / g~140m 2 / g, for example, 20m 2 / g、30m 2 / g、40m 2 / g, 50m 2 / g、60m 2 / g、70m 2 / g、80m 2 / g、90m 2 / g, 100m 2 / g、110m 2 / g、120m 2 / g、130m 2 / g or 140m 2 / g. The specific surface area of ​​the first lithium-conducting particle can be measured using the BET test method, as follows: The positive electrode sheet is immersed in dimethyl carbonate (DMC) solvent for 10 minutes. The surface active material layer is carefully scraped off with a scraper to expose the functional layer. The functional layer is then scraped again and immersed in DMC solvent for 1 hour. The liquid containing the functional layer components is filtered using filter paper to remove small-sized conductive agents, lithium salts dissolved in DMC, and binders. The remaining material is the lithium-conducting particle. The lithium-conducting particle is baked at 300°C for 30 minutes to obtain lithium-conducting particle powder as a test sample. The surface area is measured using a TriStar II surface area analyzer, with N2 as the adsorbed gas. In a preferred embodiment, the specific surface area of ​​the first lithium-conducting particle is 40 m². 2 / g~100m 2 / g.

[0040] Introducing an inorganic oxide particle and solid electrolyte material into a functional coating on the surface of the positive electrode current collector can synergistically improve the coating's chemical stability and electrochemical performance. Inorganic oxide particles possess excellent chemical stability, reacting with hydrofluoric acid to broaden the voltage operating window of the solid electrolyte and improve the stability of the functional layer at high voltages. The solid electrolyte material in the coating layer more effectively conducts lithium, reducing the amount of solid electrolyte used and lowering operating costs. However, excessively small particle size leads to an increased specific surface area of ​​the first lithium-conducting particles, increasing the contact area between the solid electrolyte material coating the inorganic oxide particles and the electrolyte, accelerating the decomposition of the solid electrolyte material on the particle surface. Conversely, excessively large particle size results in a smaller specific surface area of ​​the first lithium-conducting particles, making it difficult to form abundant lithium conduction pathways and affecting the improvement in low-temperature performance. Therefore, by further controlling the median particle size Dv50 and specific surface area of ​​the first lithium-conducting particles within a suitable range, the present invention can improve the contact effect between the first lithium-conducting particles and avoid excessive contact area between the solid electrolyte material and the electrolyte, which would cause the metal of the solid electrolyte material to dissolve and decompose, affecting the stability of the solid electrolyte lithium-conducting structure.

[0041] In one specific embodiment, the inorganic oxide particles include one or more of the following: aluminum oxide (Al2O3), titanium oxide (TiO2), magnesium oxide (MgO), silicon dioxide (SiO2), zirconium oxide (ZrO2), boehmite (AlOOH), yttrium oxide (Y2O3), lanthanum oxide (La2O3), cerium oxide (CeO2), neodymium oxide (Nd2O3), tantalum oxide (Ta2O5), niobium oxide (Nb2O5), zinc oxide (ZnO), tin oxide (SnO2), tungsten oxide (WO3), vanadium oxide (V2O5), nickel oxide (NiO), cobalt oxide (CoO), manganese oxide (MnO2), gallium oxide (Ga2O3), indium oxide (In2O3), and hafnium oxide (HfO2).

[0042] In one specific embodiment, the median particle size Dv50 of the inorganic oxide particles is 0.2 μm to 5 μm, for example, 0.2 μm, 0.3 μm, 0.4 μm, 0.5 μm, 0.6 μm, 0.7 μm, 0.8 μm, 0.9 μm, 1 μm, 2 μm, 3 μm, 4 μm, or 5 μm. In a preferred embodiment, the median particle size Dv50 of the inorganic oxide particles is 0.8 μm to 3.0 μm. If the particle size of the inorganic oxide particles is less than 0.2 μm, the particles are prone to agglomeration, resulting in uneven coating of the solid electrolyte material; if the particle size of the inorganic oxide particles exceeds 5 μm, the overall particle size of the first lithium-conducting particles will be too large, causing breakpoints in the lithium-conducting path, and the excessively large inorganic oxide particles will also cause stress concentration and scratches on the current collector, resulting in a decrease in the mechanical properties of the electrode. The present invention controls the median particle size Dv50 of the inorganic oxide particles within this range, which not only reserves sufficient coating space for the solid electrolyte shell, but also ensures that the overall particle size of the first lithium conductive particles falls within the matching range, thereby avoiding uneven coating of the solid electrolyte material. Furthermore, the requirement for sphericity of the inorganic oxide particles can also reduce scratch damage to the aluminum foil during rolling.

[0043] In one specific embodiment, the sphericity of the inorganic oxide particles is greater than 0.7, preferably greater than 0.8.

[0044] Due to the sintering process of the solid electrolyte in the first lithium-ion particles, the first lithium-ion particles produced are generally blocky structures full of edges and corners. When they are coated on the surface of the positive electrode current collector aluminum foil, they may cause certain damage to the positive electrode current collector aluminum foil during the rolling stage of the electrode, resulting in abnormalities such as electrode strip breakage and cycle breakage. Therefore, this invention further controls the sphericity of the inorganic oxide particles to be greater than 0.7, and combines the solid electrolyte material with the surface of the near-spherical inorganic oxide particles during the synthesis process, which can improve the external shape of the first lithium-ion particles and reduce their damage to the positive electrode current collector aluminum foil.

[0045] In one specific embodiment, the surface of the inorganic oxide particles further includes dimethylsiloxane (-(CH3)2-Si-O-), trimethylsilyl (-Si(CH3)3), and octylsilyl (-SiC8H) groups. 17The coating contains at least one group selected from dimethylsilanol (-Si(CH3)2-OH) and 3-aminopropylsilyl (-SiC3H6NH2). By grafting a silane coupling agent onto the surface of inorganic oxide particles for surface hydrophobic treatment, the core principle is to reduce the adsorption of moisture from the environment by the particles through the hydrophobic properties of the silane coupling agent, thereby reducing the water absorption capacity of the solid electrolyte material. This reduces the water content in the coating, preventing the deterioration of battery performance at high temperatures due to excessive water content in the solid electrolyte, thus improving the battery's thermal safety performance. Furthermore, the reduced water content in the coating decreases the reaction between water and the electrolyte to generate hydrofluoric acid (HF), further mitigating the corrosion of the solid electrolyte coating structure by HF, reducing the amount of metal leaching from the solid electrolyte, and improving its cycle stability.

[0046] In one specific embodiment, the surface of the inorganic oxide particles is further provided with a conductive coating, which includes at least one of a conductive oxide-based coating material, a carbon-based coating material, and a metal-based coating material. Specifically, the conductive oxide-based coating material includes at least one of antimony tin oxide (ATO), indium tin oxide (ITO), fluorine-doped tin oxide (FTO), and aluminum-doped zinc oxide (AZO); the carbon-based coating material includes at least one of amorphous carbon and carbon quantum dots (CQDs); and the metal-based coating material includes at least one of nano-silver (Ag), nano-gold (Au), nano-copper (Cu), and nickel (Ni). The average thickness of the conductive coating is less than 10 nm, for example, 10 nm, 9 nm, 8 nm, 7 nm, 6 nm, 5 nm, 4 nm, 3 nm, 2 nm, or 1 nm. In one specific embodiment, the average thickness of the conductive coating is 3 nm to 8 nm. By adding a conductive coating to the surface of inorganic oxide particles, the intrinsic conductivity of the first lithium-conducting particles can be improved, achieving a balance between lithium conduction and conductivity. This retains the lithium-ion transport capability of the solid electrolyte while filling the electronic conduction gaps between particles, improving the conductive path between the current collector and the active material layer, further reducing charge-discharge polarization and ohmic heat, and avoiding the impact on battery performance due to obstructed electronic conduction. The thickness is controlled to be less than 10nm because if it is too thick, it will encroach on the coating space of the solid electrolyte, which may lead to discontinuous lithium conduction pathways and easily cause particle agglomeration; if it is too thin, it will not be able to form a complete conductive layer and will be difficult to effectively exert its conductive function. By controlling the thickness within this range, the conductivity and lithium conduction functions can be balanced, ensuring the overall performance of the functional layer.

[0047] In one specific embodiment, based on the total mass of the functional layer, the mass content of the inorganic oxide particles is 50%-95%, for example, 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, or 95%. In a preferred embodiment, based on the total mass of the functional layer, the mass content of the inorganic oxide particles is 60%-86%. If the mass content of the inorganic oxide particles is less than 50%, the number of basic particles supporting the solid electrolyte material is too small, the solid electrolyte loses sufficient adhesion sites, and is prone to agglomeration or distribution gaps in the functional layer, resulting in breakpoints in the lithium conduction pathway and making it impossible to balance the lithium concentration of the underlying active material at low temperatures. If the mass content of the inorganic oxide particles exceeds 95%, the proportion of solid electrolyte will decrease under the extrusion of the basic particles supporting the solid electrolyte material, and the proportion of other additives (conductive agents, binders) will also be insufficient. The former will lead to the complete failure of the lithium conduction pathway, and the latter will hinder electron conduction and make the coating easy to fall off after rolling, affecting the safety performance of the battery. This invention, by further controlling the mass content ratio of inorganic oxide particles, can provide sufficient particles as a carrier matrix, ensuring that the solid electrolyte material can be uniformly coated on the particle surface. This avoids uneven dispersion, local accumulation, or gaps in the solid electrolyte due to insufficient carrier matrix, thereby ensuring that the solid electrolyte shells of adjacent particles can fully contact each other and form a continuous lateral lithium conduction path. At the same time, it can avoid excessive compression of the solid electrolyte, conductive agent, and binder ratio by the carrier particles, and ensure smooth electron conduction and that the adhesion between the functional layer and the current collector is not affected.

[0048] In one specific embodiment, the solid electrolyte material includes one or more of the following: lithium lanthanum zirconium oxide (LLZO), lithium titanium aluminum phosphate (LATP), lithium lanthanum titanium oxide (LLTO), lithium aluminum titanium phosphorus oxide (LAGP), lithium germanium phosphorus sulfide (LGPS), lithium phosphorus sulfide chloride (LPSC), lithium phosphorus sulfide nitrogen (LPSN), lithium tin phosphorus sulfide (LSPS), lithium silicon phosphorus sulfide (LSiPS), lithium germanium aluminum phosphate (LAGS), and halide electrolytes. Among these, halide electrolytes include, for example, Li3YCl3Br3 and Li2ZrCl6. It should be noted that solid electrolyte materials are compounds that possess surface ion conductivity in a solid state, including but not limited to the substances mentioned above.

[0049] Solid electrolyte materials should generally contain migratable active ions (Li+, Na+, Na+). + Mg 2+ (at least one of the following), for lithium-ion battery systems, Li in the solid electrolyte + The molar percentage is not less than 5%, such as Li1.3Al0.3Ti1.7(PO4)3. The material consists of metal cations (such as Li, La, Zr, Ti, Al, etc.) and non-metal anions (such as O). 2- S2- PO4 3- This results in a composite structure with a rigid framework (such as garnet-type, NASICON-type, or tetrahedral structures). The material is electrically neutral overall, with a charge balance between cations and anions. Al can be doped. 3+ Ga 3+ Ta 5+ By adjusting the lattice parameters with elements, solid electrolyte materials can replace traditional liquid electrolytes to achieve ion migration between the positive and negative electrodes. Furthermore, solid electrolyte materials exhibit less change in lithium-ion transport rate at low temperatures compared to liquid electrolytes and pose no flammability risk. This invention, by setting a functional layer in the positive electrode and introducing coated particles composed of solid electrolyte materials with current-equalizing properties and inorganic oxide particles, enables the application of conventional solid electrolytes in high-voltage positive electrode systems. While maintaining lithium conductivity, it also improves the stability of the solid electrolyte against high-voltage degradation and chemical degradation by reaction with hydrofluoric acid in the electrolyte.

[0050] In one specific embodiment, 0.5μm ≤ Dg ≤ 10μm, for example, 0.5μm, 1μm, 2μm, 3μm, 4μm, 5μm, 6μm, 7μm, 8μm, 9μm, or 10μm. In a preferred embodiment, 1μm ≤ Dg ≤ 5μm. In the functional layer of the present invention, Dg ≥ 0.5μm ensures that the first lithium-conducting particles can be uniformly spread within the functional layer, which is beneficial for forming a continuous lateral lithium-conducting path of particle stacking, avoiding incomplete particle coverage and lithium-conducting breakpoints due to excessively thin coating, and meeting the basic requirement of balanced lithium concentration of the bottom active material particles; Dg ≤ 10μm avoids the functional layer from encroaching on the space of the positive electrode active material layer, thereby ensuring the battery energy density and cycle performance.

[0051] In one specific embodiment, the functional layer further includes a conductive agent and an adhesive, and the sum of the mass content percentages of the conductive agent and the adhesive, based on the total mass of the functional layer, is 2%-15%, for example, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14% or 15%.

[0052] In a preferred embodiment, the combined mass content of the conductive agent and the adhesive is 4%-10%.

[0053] The presence of conductive agents can fill the electronic conduction gap between inorganic oxide particles and solid electrolyte, preventing increased electrode polarization due to obstructed electronic conduction. Binders can firmly bond inorganic oxide particles, solid electrolyte materials, and conductive agents to the surface of the positive electrode current collector, preventing coating peeling during coating, rolling, and cycling. Therefore, the content of the above-mentioned functional layer additives should not be too low. However, excessive additive content can also reduce the content of solid electrolyte materials. Therefore, this invention, by further controlling the sum of the conductive agent and binder content in the functional layer, can help increase the proportion of solid electrolyte materials in the functional layer, thereby further improving the lithium replenishment effect of the functional layer. It can also control the additive content to avoid it being too low, thereby reducing the obstruction to lithium-ion diffusion, optimizing the ion transport path, enhancing fast-charging performance, and reducing coating cracking and peeling during cycling.

[0054] In one specific embodiment, the inorganic oxide particles are further provided with a conductive coating, which includes antimony-doped tin dioxide. In this case, the first conductive lithium particles themselves have a certain conductivity, and other types of conductive agents may not be added, that is, the mass content of conductive agents may be 0%.

[0055] In one specific embodiment, the conductive agent includes one or more of acetylene black, Ketjen black, superconducting carbon black (Super P), carbon nanotubes (CNTs), graphene, carbon fibers, metal powder (MP), metal nanowires (MN), conductive graphite (CGO), and expanded graphite (EGO). Graphene further includes graphene oxide (GO) and reduced graphene oxide (RGO), and carbon fibers further include vapor-grown carbon fibers (VGCFs) and carbon nanofibers (CNFs).

[0056] In one specific embodiment, the adhesive includes one or more of the following: polyvinylidene fluoride (PVDF), styrene-butadiene rubber (SBR), sodium carboxymethyl cellulose (CMC), hydroxypropyl methyl cellulose (HPMC), polyacrylic acid (PAA), polyethylene oxide (PEO), polytetrafluoroethylene (PTFE), ethylene-vinyl acetate copolymer (EVA), polyvinylpyrrolidone (PVP), sodium alginate (SA), chitosan (CS), polyvinylidene fluoride-hexafluoropropylene (PVDF-HFP), polyimide (PI), polyvinyl alcohol (PVA), polymethyl methacrylate (PMMA), polyacrylonitrile (PAN), polypropylene emulsion (LA132), hydrogenated nitrile butadiene rubber (HNBR), and β-cyclodextrin polymer (β-CDp).

[0057] A second aspect of the present invention provides a battery comprising the positive electrode sheet described in the first aspect of the present invention.

[0058] According to the battery of the present invention, the battery further includes a negative electrode, a separator, and an electrolyte. The present invention does not have special requirements for the negative electrode, separator, and electrolyte in the battery, and conventional designs can be selected. For example, the negative electrode active material of the negative electrode sheet is selected from hard carbon, soft carbon, graphite, silicon carbide, etc.; the negative electrode conductive agent is selected from carbon nanotubes (CNT), conductive carbon black (Super P), acetylene black, Ketjen black, and conductive graphite, etc.; the negative electrode binder is selected from polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), polyacrylic acid (PAA), sodium alginate, styrene-butadiene rubber (SBR), sodium carboxymethyl cellulose (CMC), etc.; the negative electrode dispersant is selected from lithium carboxymethyl cellulose (CMC-Li), etc.; the separator is selected from polypropylene separator (PP), polyimide separator (PI), polyethylene separator (PE), ceramic coated separator, etc.; the electrolyte contains lithium salt and organic solvent, wherein the lithium salt is selected from iPF6, and the organic solvent is selected from ethylene carbonate (EC), dimethyl carbonate (DMC), diethyl carbonate (DEC), methyl ethyl carbonate (EMC), etc., which will not be elaborated further in this invention.

[0059] The present invention will be described in detail below through embodiments. The embodiments described herein are only a part of the embodiments of the present invention, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

[0060] Example 1

[0061] 1. Preparation of functional layers:

[0062] A lithium aluminum titanium phosphate (LATP)-coated fumed alumina core-shell material (first lithium-conducting particles, wherein the median particle size Dv50 of the inorganic oxide particles is 1.5 μm and the sphericity of the inorganic oxide particles is 0.9), PVDF, carbon black, and carbon nanotubes were mixed in NMP solvent at a mass ratio of 90:6:3:1 and a uniform functional layer slurry was prepared by high-speed stirring. The solid content of the functional layer slurry was 25%. Subsequently, the functional layer slurry was coated onto both sides of a 10 μm thick aluminum foil using a 150-mesh gravure roller, with an areal density of 4.0 g / m². 2 After coating, a baking process is performed to obtain a functional layer with lithium-ion conductivity. The median particle size (Dv50) of the first lithium-ion conductive particles is 0.8 μm, and the specific surface area of ​​the first lithium-ion conductive particles is approximately 40 m². 2 / g; Based on the total mass of the functional layer, the content of solid electrolyte material LATP accounts for 15% of the total mass of the functional layer, and the content of fumed alumina accounts for 75% of the total mass of the functional layer; The average thickness of the shell formed by the solid electrolyte material is 50nm.

[0063] 2. Preparation of the positive electrode sheet:

[0064] Lithium cobalt oxide, PVDF, carbon black, and carbon nanotubes were mixed in NMP solvent at a mass ratio of 98:1:0.8:0.2 and a uniform positive electrode active material slurry was prepared by high-speed stirring. Subsequently, this slurry was coated onto both surfaces of the prepared functional layer using an extrusion coating method. After coating, the electrode sheet underwent baking, rolling, and slitting processes to finally obtain a positive electrode sheet with a functional layer on the aluminum foil surface. The single-sided thickness Dg of the functional layer on the current collector side after rolling is 2 μm, and the single-sided thickness of the positive electrode active material layer on the current collector side is 40 μm. The average number of lithium cobalt oxide particles on any cross-section of the positive electrode active material layer is 10, meaning that an average of 10 positive electrode active material particles are arranged along the thickness direction of the positive electrode current collector. Calculations show that N / Dg = 5.

[0065] 3. Preparation of the negative electrode sheet:

[0066] Artificial graphite, styrene-butadiene rubber (SBR) binder, and lithium carboxymethyl cellulose (CMC-Li) dispersant were mixed in deionized water at a mass ratio of 97.5:2:0.5 and mixed with a high-speed mixer to form a uniform negative electrode slurry. Subsequently, the slurry was coated onto both surfaces of a copper foil using an extrusion coating machine. After coating, the foil was successively baked, rolled, and slit to obtain a negative electrode sheet with uniform structure and good adhesion.

[0067] 4. Battery assembly:

[0068] A 6μm thick polypropylene (PP) base film is used as the separator, with a 2μm ceramic coating applied to both sides. A 2μm adhesive layer is then applied over the ceramic coating to improve the separator's thermal stability and interfacial adhesion. Lithium hexafluorophosphate (LiPF6) is used as the lithium salt in the electrolyte system at a concentration of 1.0 M / L. The solvents are ethylene carbonate (EC), diethyl carbonate (DEC), and methyl ethyl carbonate (EMC) in a volume ratio of 1:1:1. The positive and negative electrode sheets and the commonly used separator are stacked sequentially and wound into a core, which is then encapsulated using an aluminum-plastic film. After encapsulation, the battery is baked to remove moisture, and then undergoes processes such as electrolyte injection, resting, formation, secondary encapsulation, and sorting to finally obtain the finished lithium battery.

[0069] Example 2 group

[0070] The preparation method of this set of embodiments is the same as that of Embodiment 1, except that the coating amount of functional layer slurry is changed, so that the thickness Dg of the functional layer in the positive electrode sheet is changed, as shown in Table 1.

[0071] Example 3 Group

[0072] The preparation method of this set of embodiments is the same as that of Embodiment 1, except that the coating amount of functional layer slurry and / or positive electrode active material slurry is changed, so that the thickness Dg of the functional layer and / or the number N of positive electrode active material particles are changed, as detailed in Table 1.

[0073] Example 4 group

[0074] The preparation method of this set of embodiments is the same as that of Embodiment 1. The difference is that the amount of solid electrolyte material added during the preparation of the first lithium conductive particle is changed, so that the average thickness of the shell formed by the solid electrolyte material coating the surface of the inorganic oxide particle is changed. See Table 1 for details.

[0075] Example 5 group

[0076] The preparation method of this set of embodiments is the same as that of Embodiment 1, except that the specific selection of inorganic oxide particles, median particle size Dv50, sphericity and solid electrolyte material are changed, as detailed in Table 1.

[0077] Comparative Example 1

[0078] The comparative examples in this group follow the preparation method of Example 1, except that the coating amount of the functional layer slurry and / or the positive electrode active material slurry is changed, so that the thickness Dg of the functional layer and / or the number N of the positive electrode active material particles are changed, as detailed in Table 1.

[0079] Comparative Example 2

[0080] This comparative example follows the preparation method of Example 1, except that the preparation methods of the functional layer and the positive electrode are changed, so that the solid electrolyte material is dispersed in the functional coating in a mixed form and does not form a coating on the surface of the inorganic oxide particles.

[0081] Table 1

[0082]

[0083]

[0084] Test case

[0085] 1. Battery -20℃ low temperature discharge test:

[0086] The batteries obtained in the examples and comparative examples were charged and discharged at room temperature at a charge-discharge rate of 1C and a charge-discharge range of 3.0V to 4.5V, with a charging cut-off current of 0.05C. Five charge-discharge cycles were performed for pre-activation. Then, the batteries were discharged at a rate of 0.25C to 3.0V, and the discharge capacity was recorded as Q2. The batteries were charged at a rate of 1C to 4.5V at room temperature with a cut-off current of 0.05C. The fully charged batteries were left to stand at -20°C for 4 hours. Then, the batteries were discharged at -20°C at a rate of 0.25C to 3.0V, and the discharge capacity was recorded as Q1. The capacity retention rate was calculated, and the results are shown in Table 2.

[0087] The calculation formula used is as follows: Capacity retention rate (%) at -20℃ = Q1 / Q2 × 100.

[0088] 2. Battery 45℃ cycle test:

[0089] The batteries obtained in the examples and comparative examples were subjected to 500 charge-discharge cycles at 45°C with a charge-discharge rate of 1C / 1C and a charge-discharge cutoff voltage of 3.0V to 4.5V. The cycle discharge capacity was recorded and divided by the discharge capacity of the first cycle to obtain the battery capacity retention rate (%). The battery thickness after cycling was recorded and divided by the battery thickness before cycling to obtain the battery thickness change rate (%). The results are shown in Table 2.

[0090] 3. Battery safety performance test:

[0091] The batteries obtained in the above embodiments and comparative examples, in a fully charged state, were placed in an oven and heated at a temperature rise rate of 5±2℃ / min. When the temperature inside the oven reached 130℃, it was kept constant for 60 minutes. The test was considered passed if the batteries did not catch fire or explode. Each group of 20 batteries was tested, and the number of batteries that passed the test was recorded as n. n / 20 means that n out of the 20 batteries passed the test. The results are recorded in Table 2.

[0092] Table 2

[0093]

[0094]

[0095] As can be seen from Table 2, the positive electrode sheet of the present invention, by setting a functional layer containing first lithium-conducting particles between the positive electrode current collector and the positive electrode active material layer, can form a continuous lateral lithium-conducting path at the bottom of the positive electrode active material layer with the help of the first lithium-conducting particles, effectively improving the lithium concentration balance problem among the active material particles at the bottom of the positive electrode, thereby improving the low-temperature performance of the lithium battery; and by controlling the N / Dg ratio within the range, by matching the optimal Dg for different N values, the degree of inter-intercalation between the functional layer and the positive electrode active material layer can be increased, thereby further improving the lithium balance problem at the bottom of the positive electrode, and further improving the low-temperature performance, cycle stability and safety of the lithium battery.

[0096] The preferred embodiments of the present invention have been described in detail above; however, the present invention is not limited thereto. Within the scope of the inventive concept, various simple modifications can be made to the technical solutions of the present invention, including combinations of various technical features in any other suitable manner. These simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within the protection scope of the present invention.

Claims

1. A positive electrode sheet characterized by comprising: The positive electrode sheet comprises a positive electrode current collector, a functional layer on the surface of the positive electrode current collector, and a positive electrode active material layer on the surface of the functional layer, the functional layer being between the positive electrode current collector and the positive electrode active material layer; The functional layer comprises first lithium-conducting particles, the first lithium-conducting particles comprising inorganic oxide particles and solid-state electrolyte material coated on the surface of the inorganic oxide particles; In any cross section of the positive electrode active material layer perpendicular to the plane of the positive electrode current collector, N positive electrode active material particles are arranged along the thickness direction of the positive electrode current collector; the thickness of the functional layer is Dg, in units of μm; The N and Dg satisfy the following relationship: 0.6≤N / Dg≤40.

2. The positive electrode sheet according to claim 1, wherein Based on the total mass of the functional layer, the mass content of the solid-state electrolyte material is 1%-50%, preferably 3%-20%.

3. The positive electrode sheet according to claim 1, wherein The average thickness of the shell formed by the solid-state electrolyte material coating on the surface of the inorganic oxide particles is 10 nm-1500 nm, preferably 30 nm-300 nm.

4. The positive electrode sheet according to claim 1, wherein The median particle size Dv50 of the first lithium-conducting particles is 0.3 μm-7 μm, preferably 1 μm-4 μm; And / or, the specific surface area of the first lithium-guiding particles is 20 m 2 / g to 140 m 2 / g, preferably 40 m 2 / g to 100 m 2 / g.

5. The positive electrode sheet according to claim 1, wherein The inorganic oxide particles comprise one or more of aluminum oxide, titanium oxide, magnesium oxide, silicon dioxide, zirconium oxide, boehmite, yttrium oxide, lanthanum oxide, cerium oxide, neodymium oxide, tantalum oxide, niobium oxide, zinc oxide, tin oxide, tungsten oxide, vanadium oxide, nickel oxide, cobalt oxide, manganese oxide, gallium oxide, indium oxide, and hafnium oxide; And / or, the median particle size Dv50 of the inorganic oxide particles is 0.2 μm-5 μm, preferably 0.8 μm-3.0 μm; And / or, the sphericity of the inorganic oxide particles is greater than 0.7, preferably greater than 0.

8.

6. The positive electrode sheet according to claim 1, wherein The surface of the inorganic oxide particles further comprises at least one of dimethylsiloxane groups, trimethylsilyl groups, octylsilyl groups, dimethylsilanol groups, and 3-aminopropylsilyl groups; And / or, the surface of the inorganic oxide particles is further provided with a conductive coating, the conductive coating comprising at least one of conductive oxide-based coating materials, carbon-based coating materials, and metal-based coating materials; the thickness of the conductive coating is less than 10 nm; And / or, based on the total mass of the functional layer, the mass content of the inorganic oxide particles is 50%-95%, preferably 60%-86%.

7. The positive electrode sheet according to claim 1, wherein The solid-state electrolyte material comprises one or more of lithium lanthanum zirconium oxide, titanium aluminum lithium phosphate, lithium lanthanum titanium oxide, lithium aluminum titanium phosphorus oxide, lithium germanium phosphorus sulfur, lithium phosphorus sulfur chloride, lithium phosphorus sulfur nitrogen, lithium tin phosphorus sulfur, lithium silicon phosphorus sulfur, germanium aluminum lithium phosphate, and halide electrolyte.

8. The positive electrode sheet according to claim 1, wherein 0.5 μm≤Dg≤10 μm, preferably 1 μm≤Dg≤5 μm.

9. The positive electrode sheet according to claim 1, wherein The functional layer further comprises a conductive agent and a binder, and the mass content of the conductive agent and the binder is 2%-15%, preferably 4%-10%, based on the total mass of the functional layer; The conductive agent comprises one or more of acetylene black, ketjen black, superconducting carbon black, carbon nanotubes, graphene, carbon fibers, metal powders, metal nanowires, conductive graphite, and expanded graphite. The adhesive includes one or more of polyvinylidene fluoride, styrene-butadiene rubber, sodium carboxymethyl cellulose, hydroxypropyl methyl cellulose, polyacrylic acid, polyethylene oxide, polytetrafluoroethylene, ethylene-vinyl acetate copolymer, polyvinylpyrrolidone, sodium alginate, chitosan, polyvinylidene fluoride-hexafluoropropylene, polyimide, polyvinyl alcohol, polymethyl methacrylate, polyacrylonitrile, polypropylene emulsion, hydrogenated nitrile rubber, and β-cyclodextrin polymer.

10. A battery, characterized by The battery includes the positive electrode sheet of any one of claims 1-9.

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