Secondary battery, power utilization device, positive electrode material and preparation method of positive electrode material

Abstract

The invention provides a secondary battery, a power utilization device, a positive electrode material and a preparation method of the positive electrode material, and the secondary battery comprises a positive electrode plate, a negative electrode plate, an isolating membrane arranged between the positive electrode plate and the negative electrode plate, and an electrolyte, the positive pole piece comprises a positive current collector and a positive film layer which is arranged on at least one surface of the positive current collector and comprises a positive material; the positive electrode material comprises a lithium-containing transition metal oxide, a solid electrolyte layer coated on the outer surface of the lithium-containing transition metal oxide, and a fluxing layer located between the lithium-containing transition metal oxide and the solid electrolyte layer, and in the lithium-containing transition metal oxide, based on the total mole number of metal elements except lithium, the total mole number of the metal elements except lithium is 1-10. The molar ratio of the Ni element is larger than or equal to 80% and smaller than or equal to 100%, and the fluxing layer comprises one or more of alkali metal oxide, alkaline earth metal oxide and aluminum oxide. The secondary battery in the present application has improved cycle performance and storage performance.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of batteries, in particular to a secondary battery, a power utilization device, a positive electrode material and a preparation method thereof. BACKGROUND

[0002] In recent years, with the application range of secondary batteries becoming more and more extensive, secondary batteries are widely used in energy storage power supply systems such as hydropower, thermal power, wind power and solar power stations, and in many fields such as electric tools, electric bicycles, electric motorcycles, electric vehicles, aerospace, etc. Due to the great development of secondary batteries, higher requirements are put forward for their capacity and cycle stability.

[0003] The positive electrode sheet, as an important component of the secondary battery, its performance affects the performance of the secondary battery to a certain extent. At present, due to the high gram capacity of lithium-containing transition metal oxides such as high-nickel materials, they are usually used as positive active materials, but the high-nickel material has poor interface stability during charging and discharging, which is not conducive to the cycle performance and storage performance of the secondary battery. SUMMARY

[0004] The present application is made in view of the above-mentioned problems, and aims to provide a secondary battery, a power utilization device, a positive electrode material and a preparation method thereof. The secondary battery in the present application has improved cycle performance and storage performance.

[0005] In order to achieve the above-mentioned purpose, the first aspect of the present application provides a secondary battery, comprising: a positive electrode sheet, a negative electrode sheet, a separator arranged between the positive electrode sheet and the negative electrode sheet and an electrolyte, the positive electrode sheet comprising a positive electrode current collector and a positive electrode film layer arranged on at least one surface of the positive electrode current collector and comprising a positive electrode material, the positive electrode material comprising a lithium-containing transition metal oxide, a solid-state electrolyte layer coated on the outer surface of the lithium-containing transition metal oxide and a fluxing layer located between the lithium-containing transition metal oxide and the solid-state electrolyte layer, in the lithium-containing transition metal oxide, the mole percentage of Ni element is greater than or equal to 80% and less than or equal to 100% based on the total moles of metal elements other than lithium; the fluxing layer comprises one or more of alkali metal oxides, alkaline earth metal oxides and aluminum oxides.

[0006] In the present application, a fluxing layer is arranged between the lithium-containing transition metal oxide and the solid electrolyte layer. Since the fluxing layer comprises one or more of alkali metal oxides, alkaline earth metal oxides, and aluminum oxides, the fluxing layer can form molten metal oxides when heated. Thus, at high temperatures, the fluxing layer can exchange atoms with the lithium-containing transition metal oxide and the metal atoms in the solid electrolyte layer, form covalent bonds, and thus promote the fusion of the interface between the lithium-containing transition metal oxide and the solid electrolyte, improve the adhesion and stability of the solid electrolyte layer on the surface of the lithium-containing transition metal oxide, and improve the stability of the positive electrode material. Thus, it is beneficial to the cycle performance and storage performance of the secondary battery.

[0007] In some embodiments, the fluxing layer comprises alkali metal oxides and / or alkaline earth metal oxides. The above-mentioned oxides can form a molten state when heated, and have strong reactivity and atomic exchange ability. Therefore, using the above-mentioned materials as the fluxing layer is more conducive to promoting the fusion of the interface between the lithium-containing transition metal oxide and the solid electrolyte, and thus more conducive to the cycle performance and storage performance of the secondary battery.

[0008] In some embodiments, the fluxing layer comprises one or more of MgO, CaO, Al2O3, SrO, BaO, Na2O, and K2O. The above-mentioned oxides can form a molten state when heated, and have strong reactivity and atomic exchange ability. Therefore, using the above-mentioned materials as the fluxing layer is more conducive to promoting the fusion of the interface between the lithium-containing transition metal oxide and the solid electrolyte, and thus more conducive to the cycle performance and storage performance of the secondary battery.

[0009] In some embodiments, the mass fraction of the fluxing layer in the positive electrode material is 0.01wt% to 0.2wt%. Alternatively, the mass fraction of the fluxing layer in the positive electrode material is 0.02wt% to 0.1wt%. Thus, the adhesion and stability of the solid electrolyte layer on the surface of the lithium-containing transition metal oxide can be improved without affecting the gram capacity of the positive electrode material, i.e., the cycle performance, storage performance, and capacity of the secondary battery are taken into account.

[0010] In some embodiments, the thickness of the fluxing layer is 5nm to 30nm. Thus, the adhesion and stability of the solid electrolyte layer on the surface of the lithium-containing transition metal oxide can be improved without affecting the gram capacity of the positive electrode material, i.e., the cycle performance, storage performance, and capacity of the secondary battery are taken into account.

[0011] In some embodiments, the solid electrolyte layer comprises a chemical formula Li d M2X d+3The material comprises, wherein 1≤d≤6, M2 includes one or more of Al, Ga, In, Y, Zr, Nb, Sc, Ti, Mn, and La, and X includes one or more of halogens, S, O, and P. The above materials exhibit high ionic conductivity, which can enhance the diffusion rate of active ions at the interface between lithium-containing transition metal oxides and solid electrolytes, thereby reducing polarization and improving the cycle performance of secondary batteries.

[0012] In some embodiments, the solid electrolyte layer comprises an oxide solid electrolyte and / or a phosphate solid electrolyte. Oxide solid electrolytes and / or phosphate solid electrolytes have high ionic conductivity, which can enhance the diffusion rate of active ions at the interface between the lithium-containing transition metal oxide and the solid electrolyte, thereby reducing polarization and improving the cycle performance of the secondary battery.

[0013] In some embodiments, the solid electrolyte layer accounts for 0.05 wt% to 1 wt% of the mass of the cathode material. This allows for an increase in the diffusion rate of active ions at the interface between the lithium-containing transition metal oxide and the solid electrolyte without excessively affecting the specific capacity of the cathode material, thus balancing the cycle performance and capacity of the secondary battery.

[0014] In some embodiments, the thickness of the solid electrolyte layer is 50 nm to 200 nm. This allows for an increase in the diffusion rate of active ions at the interface between the lithium-containing transition metal oxide and the solid electrolyte without excessively affecting the specific capacity of the cathode material, thus balancing the cycle performance and capacity of the secondary battery.

[0015] In some embodiments, the lithium-containing transition metal oxide includes the chemical formula Li a Ni b M1 c The O2 material, wherein M1 includes one or more of Co, Mn, Al, Mg, Ti, and Zr, with 0.6≤a≤1.1, 0.8≤b≤1, and 0≤c≤0.2. The above-mentioned lithium-containing transition metal oxides exhibit high capacity, which is beneficial for further improving battery capacity.

[0016] In some implementations, 0.9 ≤ b ≤ 1. This results in a higher specific capacity for the cathode material, which is beneficial for improving the energy density of the secondary battery.

[0017] In some embodiments, the lithium-containing transition metal oxide includes LiNi. 0.8 Co 0.1 Mn 0.1 O2 and / or LiNi 0.9 Co 0.05 Mn 0.05 O2. The aforementioned lithium-containing transition metal oxides have higher specific capacity, which is more conducive to improving the energy density of secondary batteries.

[0018] In some embodiments, the volumetric particle size distribution of the cathode material is 8 μm ≤ Dv50 ≤ 15 μm. A volumetric particle size distribution within this range is beneficial for achieving a higher compaction density.

[0019] In some implementations, the compaction density of the cathode material at 3t is greater than or equal to 3g / cc. This is beneficial for further improving the energy density of the secondary battery.

[0020] In some embodiments, the negative electrode sheet includes a negative current collector and a negative electrode film layer disposed on at least one surface of the negative current collector and including a negative electrode material, wherein the negative electrode material includes one or more of graphite, soft carbon, hard carbon, and silicon carbon.

[0021] The second aspect of this application provides an electrical device, including the secondary battery provided in the first aspect.

[0022] A third aspect of this application provides a cathode material, comprising a lithium-containing transition metal oxide, a solid electrolyte layer coated on the outer surface of the lithium-containing transition metal oxide, and a fluxing layer located between the lithium-containing transition metal oxide and the solid electrolyte layer. In the lithium-containing transition metal oxide, the molar percentage of Ni element is greater than or equal to 80% and less than or equal to 100% based on the total molar number excluding lithium. The fluxing layer comprises one or more of alkali metal oxides, alkaline earth metal oxides, and aluminum oxides.

[0023] In this application, a fluxing layer is provided between the lithium-containing transition metal oxide and the solid electrolyte layer. Since the fluxing layer includes one or more of alkali metal oxides, alkaline earth metal oxides, and aluminum oxides, it includes metal oxides that can form a molten state when heated. Thus, at high temperatures, the fluxing layer can exchange atoms with the lithium-containing transition metal oxide and the metals in the solid electrolyte to form covalent bonds. This promotes the interfacial fusion between the lithium-containing transition metal oxide and the solid electrolyte, improves the adhesion and stability of the solid electrolyte layer on the surface of the lithium-containing transition metal oxide, and thus improves the stability of the cathode material. This is beneficial to the cycle performance and storage performance of the secondary battery.

[0024] In some embodiments, the fluxing layer comprises alkali metal oxides and / or alkaline earth metal oxides. Optionally, the fluxing layer comprises one or more of MgO, CaO, Al2O3, SrO, BaO, Na2O, and K2O. Further optionally, the aforementioned oxides are capable of forming a molten state upon heating and possess strong reactivity and atom exchange capacity. Therefore, using these materials as the fluxing layer is more conducive to promoting interfacial fusion between the lithium-containing transition metal oxide and the solid electrolyte, thereby improving the cycle performance and storage performance of the secondary battery.

[0025] In some embodiments, the flux layer accounts for 0.01 wt% to 0.2 wt% of the cathode material by mass. Optionally, it is 0.02 wt% to 0.1 wt%. Thus, it is possible to improve the adhesion and stability of the solid electrolyte layer on the lithium-containing transition metal oxide surface without affecting the specific capacity of the cathode material, that is, to balance the cycle performance, storage performance and capacity of the secondary battery.

[0026] In some embodiments, the thickness of the flux layer is 5 nm to 30 nm. This allows for improved adhesion and stability of the solid electrolyte layer on the lithium-containing transition metal oxide surface without affecting the specific capacity of the cathode material, thus balancing the cycle performance, storage performance, and capacity of the secondary battery.

[0027] In some embodiments, the solid electrolyte layer comprises Li d M2X d+3 The material comprises, wherein 1≤d≤6, M2 includes one or more of Al, Ga, In, Y, Zr, Nb, Sc, Ti, Mn, and La, and X includes one or more of halogens, S, O, and P. The above materials exhibit high ionic conductivity, which can enhance the diffusion rate of active ions at the interface between lithium-containing transition metal oxides and solid electrolytes, thereby reducing polarization and improving the cycle performance of secondary batteries.

[0028] In some embodiments, the solid electrolyte layer comprises an oxide solid electrolyte and / or a phosphate solid electrolyte. Oxide solid electrolytes and / or phosphate solid electrolytes have high ionic conductivity, which can enhance the diffusion rate of active ions at the interface between the lithium-containing transition metal oxide and the solid electrolyte, thereby reducing polarization and improving the cycle performance of the secondary battery.

[0029] In some embodiments, the solid electrolyte layer accounts for 0.05 wt% to 1 wt% of the mass of the cathode material. This allows for an increase in the diffusion rate of active ions at the interface between the lithium-containing transition metal oxide and the solid electrolyte without excessively affecting the specific capacity of the cathode material, thus balancing the cycle performance and capacity of the secondary battery.

[0030] In some embodiments, the thickness of the solid electrolyte layer is 50 nm to 200 nm. This allows for an increase in the diffusion rate of active ions at the interface between the lithium-containing transition metal oxide and the solid electrolyte without excessively affecting the specific capacity of the cathode material, thus balancing the cycle performance and capacity of the secondary battery.

[0031] In some embodiments, the lithium-containing transition metal oxide includes the chemical formula Li a Ni b M1 cThe O2 material, wherein M1 includes one or more of Co, Mn, Al, Mg, Ti, and Zr, with 0.6≤a≤1.1, 0.8≤b≤1, and 0≤c≤0.2. The above-mentioned lithium-containing transition metal oxides exhibit high capacity, which is beneficial for further improving battery capacity.

[0032] In some implementations, 0.9 ≤ b ≤ 1. This results in a higher specific capacity for the cathode material, which is beneficial for improving the energy density of the secondary battery.

[0033] In some embodiments, the volumetric particle size distribution of the cathode material is 8 μm ≤ Dv50 ≤ 15 μm. A volumetric particle size distribution within this range is beneficial for achieving a higher compaction density.

[0034] In some implementations, the compaction density of the cathode material at 3t is greater than or equal to 3g / cc. This is beneficial for further improving the energy density of the secondary battery.

[0035] The fourth aspect of this application provides a method for preparing a cathode material, comprising the following steps: S1, mixing a transition metal precursor material with a lithium source and a fluxing material uniformly, and then performing a first sintering treatment to obtain a lithium-containing transition metal oxide and a fluxing layer located on the outer surface of the lithium-containing transition metal oxide, wherein the fluxing material includes one or more of alkali metal oxides, alkali metal hydroxides, alkaline earth metal oxides, alkaline earth metal hydroxides, aluminum oxides, and aluminum hydroxides; S2, mixing the lithium-containing transition metal oxide and the fluxing layer obtained in step S1 uniformly with a solid electrolyte material, and then performing a second sintering treatment to obtain a solid electrolyte layer coated with the fluxing layer.

[0036] In this application, a lithium-containing transition metal oxide and a flux layer located on the outer surface of the lithium-containing transition metal oxide are prepared through a first sintering process. A solid electrolyte layer covering the flux layer is then formed through a second sintering process. Since the flux material includes one or more of alkali metal oxides, alkali metal hydroxides, alkaline earth metal oxides, alkaline earth metal hydroxides, aluminum oxides, and aluminum hydroxides, it can form a molten state when heated. Thus, during the first and second sintering processes, the flux material melts, accelerating the exchange of metal atoms between the transition metal precursor material and the solid electrolyte layer, forming covalent bonds. This promotes interfacial fusion between the lithium-containing transition metal oxide and the solid electrolyte, improving the adhesion and stability of the solid electrolyte layer on the lithium-containing transition metal oxide surface, thereby enhancing the stability of the formed cathode material. The secondary battery prepared using the method provided in this application exhibits improved cycle performance and storage performance.

[0037] In some embodiments, in step S1, the fluxing material includes one or more of alkali metal oxides, alkali metal hydroxides, alkaline earth metal oxides, and alkaline earth metal hydroxides. These fluxing materials are more likely to form a molten state upon heating and possess strong reactivity. During the first and second sintering processes, the fluxing material more easily accelerates the exchange between metal atoms in the lithium-containing transition metal oxide and the solid electrolyte, while simultaneously forming covalent bonds. Therefore, it is more conducive to promoting interfacial fusion between the lithium-containing transition metal oxide and the solid electrolyte, thereby improving the stability of the cathode material and, consequently, enhancing the cycle performance and storage performance of the secondary battery.

[0038] In some embodiments, the fluxing material includes one or more of MgO, CaO, Al2O3, SrO, BaO, Na2O, K2O, NaOH, and KOH. These oxides can form a molten state upon heating and possess strong reactivity and atom exchange capacity. Therefore, using these materials as fluxing materials is more conducive to promoting interfacial fusion between lithium-containing transition metal oxides and the solid electrolyte, thereby improving the stability of the cathode material.

[0039] In some embodiments, the flux layer accounts for 0.01 wt% to 0.2 wt% of the mass of the cathode material. This allows for improved adhesion and stability of the solid electrolyte layer on the lithium-containing transition metal oxide surface without affecting the specific capacity of the cathode material, thus balancing the cycle performance, storage performance, and capacity of the secondary battery.

[0040] In some embodiments, the solid electrolyte layer accounts for 0.05 wt% to 1 wt% of the mass of the cathode material. This allows for an increase in the diffusion rate of active ions at the interface between the lithium-containing transition metal oxide and the solid electrolyte without excessively affecting the specific capacity of the cathode material, thus balancing the cycle performance and capacity of the secondary battery.

[0041] In some embodiments, in step S1, the lithium source is one or more of LiOH·H2O, Li2CO3, Li2SO4, LiNO3, LiC2O4, and CH3COOLi.

[0042] In some embodiments, the molar ratio of lithium in the lithium source to metal in the transition metal precursor material is 1.0 to 1.2. This is beneficial for maximizing the specific capacity of the lithium-containing transition metal oxide.

[0043] In some embodiments, in step S2, the second sintering treatment is carried out at 500°C to 700°C for 4 to 10 hours. This facilitates the formation of a solid electrolyte coating layer on the surface of the flux layer.

[0044] In some embodiments, in step S1, the first sintering treatment satisfies one or more of the following characteristics: (1) the sintering temperature is 600℃~800℃, (2) the sintering time is 8h~18h, (3) the heating rate is 0.5℃ / min~5℃ / min, and (4) the sintering atmosphere is air or oxygen. This facilitates the formation of lithium-containing transition metal oxides and the formation of a solid electrolyte coating layer on the surface of the lithium-containing transition metal oxides. Attached Figure Description

[0045] Figure 1 This is a schematic diagram of the positive electrode material according to one embodiment of this application.

[0046] Figure 2 This is a schematic diagram of a battery cell according to one embodiment of this application.

[0047] Figure 3 yes Figure 2 An exploded view of a battery cell according to one embodiment of this application is shown.

[0048] Figure 4 This is a schematic diagram of a battery module according to one embodiment of this application.

[0049] Figure 5 This is a schematic diagram of a battery pack according to one embodiment of this application.

[0050] Figure 6 yes Figure 5 An exploded view of a battery pack according to one embodiment of this application is shown.

[0051] Figure 7 This is a schematic diagram of an electrical device that uses a secondary battery as a power source according to one embodiment of this application.

[0052] Explanation of reference numerals in the attached figures:

[0053] 10 Lithium-containing transition metal oxide; 20 Fluxing layer; 30 Solid electrolyte layer; 1 Battery pack; 2 Upper housing; 3 Lower housing; 4 Battery module; 5 Battery cell; 51 Housing; 52 Electrode assembly; 53 Top cover assembly. Detailed Implementation

[0054] The following detailed description, with appropriate reference to the accompanying drawings, discloses embodiments of the secondary battery, power-consuming device, positive electrode material, and preparation method thereof of this application. However, unnecessary detailed descriptions may be omitted. For example, detailed descriptions of well-known matters and repetitive descriptions of practically identical structures may be omitted. This is to avoid unnecessarily lengthy descriptions and to facilitate understanding by those skilled in the art. Furthermore, the accompanying drawings and the following description are provided for the purpose of enabling those skilled in the art to fully understand this application and are not intended to limit the subject matter of the claims.

[0055] The "range" disclosed in this application is defined by a lower limit and an upper limit. A given range is defined by selecting a lower limit and an upper limit, which define the boundaries of a particular range. Ranges defined in this way can include or exclude endpoints and can be arbitrarily combined; that is, any lower limit can be combined with any upper limit to form a range. For example, if ranges of 60-120 and 80-110 are listed for a specific parameter, it is expected that ranges of 60-110 and 80-120 are also included. Furthermore, if minimum range values ​​of 1 and 2 are listed, and if maximum range values ​​of 3, 4, and 5 are listed, then the following ranges are all expected: 1-3, 1-4, 1-5, 2-3, 2-4, and 2-5. In this application, unless otherwise stated, the numerical range "ab" represents a shortened representation of any combination of real numbers between a and b, where a and b are real numbers. For example, the numerical range "0-5" indicates that all real numbers between "0-5" have been listed in this article; "0-5" is simply a shortened representation of these numerical combinations. Furthermore, when a parameter is stated as an integer ≥2, it is equivalent to disclosing that the parameter is, for example, an integer such as 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0056] Unless otherwise specified, all embodiments and optional embodiments of this application can be combined to form new technical solutions.

[0057] Unless otherwise specified, all technical features and optional technical features of this application may be combined to form new technical solutions.

[0058] Unless otherwise specified, all steps in this application may be performed sequentially or randomly, preferably sequentially. For example, if the method includes steps (a) and (b), it means that the method may include steps (a) and (b) performed sequentially, or it may include steps (b) and (a) performed sequentially. For example, if the method may also include step (c), it means that step (c) may be added to the method in any order. For example, the method may include steps (a), (b), and (c), or it may include steps (a), (c), and (b), or it may include steps (c), (a), and (b), etc.

[0059] Unless otherwise specified, the terms used in this application have the common meanings as commonly understood by those skilled in the art.

[0060] Unless otherwise specified, the values ​​of the parameters mentioned in this application can be determined using various testing methods commonly used in the art, for example, according to the testing methods given in this application.

[0061] Currently, to achieve higher energy density, lithium-containing transition metal oxides, such as high-nickel materials, are commonly used as cathode materials. However, during cycling and storage, high-nickel materials exhibit electrochemical activity at the Ni interface under high state of charge (SOC). 4+ High content, Ni 4+ Lithium ions can catalyze the decomposition of organic compounds such as ethylene carbonate (EC) in the electrolyte solvent, leading to the formation of a thick CEI (Chemical Electrolyte Interfacial) film on the surface of the cathode material. This CEI film gradually thickens with increasing cycle count, continuously deteriorating battery performance. Furthermore, LiPF6 in the electrolyte reacts with trace amounts of water to produce hydrofluoric acid, further eroding the cathode material and consuming active lithium, also forming a thick CEI film. To address these issues, a coating layer, such as an oxide solid electrolyte or a sulfide solid electrolyte, is typically applied to the surface of the high-nickel material. However, the interfacial compatibility between solid electrolytes and high-nickel materials is poor. During cycling, frequent lithium-ion insertion and extraction cause severe lattice distortion in the high-nickel material, resulting in frequent changes in cell volume. Moreover, due to the complex molecular structure of solid electrolytes, they can peel off from the surface of the high-nickel material during these rapid changes in cell volume, leading to deterioration of the cathode material's performance and affecting the battery's cycle and storage performance.

[0062] Based on this, this application provides a novel secondary battery, electrical device, positive electrode material, and method for preparing the same. The secondary battery of this application has improved cycle performance and storage performance.

[0063] Secondary batteries

[0064] The first aspect of this application provides a secondary battery, comprising: a positive electrode, a negative electrode, a separator disposed between the positive electrode and the negative electrode, and an electrolyte. The positive electrode includes a positive current collector and a positive electrode film layer disposed on at least one surface of the positive current collector and including a positive electrode material. The positive electrode material includes a lithium-containing transition metal oxide, a solid electrolyte layer coated on the outer surface of the lithium-containing transition metal oxide, and a fluxing layer located between the lithium-containing transition metal oxide and the solid electrolyte layer. The positive electrode material includes a lithium-containing transition metal oxide, wherein, based on the total molar number of metal elements other than lithium, the molar percentage of Ni element is greater than or equal to 80% and less than or equal to 100%. The fluxing layer includes one or more of alkali metal oxides, alkaline earth metal oxides, and aluminum oxides.

[0065] In this application, a fluxing layer is provided between the lithium-containing transition metal oxide and the solid electrolyte layer. Since the fluxing layer includes one or more of alkali metal oxides, alkaline earth metal oxides, and aluminum oxides, it can form molten metal oxides when heated (e.g., above 400°C). Thus, at high temperatures, the fluxing layer can exchange atoms with the lithium-containing transition metal oxide and the metal atoms in the solid electrolyte layer to form covalent bonds. This promotes the interfacial fusion between the lithium-containing transition metal oxide and the solid electrolyte, improves the adhesion and stability of the solid electrolyte layer on the surface of the lithium-containing transition metal oxide, and thus improves the stability of the cathode material. This is beneficial to the cycle performance and storage performance of the secondary battery.

[0066] Figure 1 This is a cross-sectional view of the positive electrode material according to an embodiment of this application, such as... Figure 1 As shown, the cathode material includes a lithium-containing transition metal oxide 10, a solid electrolyte layer 30 covering the outer surface of the lithium-containing transition metal oxide 10, and a fluxing layer 20 located between the lithium-containing transition metal oxide 10 and the solid electrolyte layer 30.

[0067] In some embodiments, the flux layer comprises alkali metal oxides and / or alkaline earth metal oxides. As examples, alkali metal oxides include one or more of lithium oxide, sodium oxide, potassium oxide, rubidium oxide, cesium oxide, and francium oxide. Alkaline earth metal oxides include one or more of beryllium oxide, magnesium oxide, calcium oxide, strontium oxide, barium oxide, and radium oxide. Alkali metal oxides and / or alkaline earth metal oxides are more likely to form a molten state upon heating and exhibit strong reactivity. At high temperatures, they more readily exchange atoms with lithium-containing transition metal oxides and metals in the solid electrolyte, forming covalent bonds. Therefore, this promotes interfacial fusion between the lithium-containing transition metal oxide and the solid electrolyte, thereby improving the cycle performance and storage performance of the secondary battery.

[0068] In some embodiments, the fluxing layer includes one or more of MgO, CaO, Al2O3, SrO, BaO, Na2O, and K2O. Optionally, the fluxing layer includes MgO and / or Na2O. These oxides can form a molten state when heated and possess strong reactivity and atom exchange capacity. Therefore, using these materials as the fluxing layer is more conducive to promoting interfacial fusion between the lithium-containing transition metal oxide and the solid electrolyte, thereby improving the cycle performance and storage performance of the secondary battery.

[0069] In some embodiments, the flux layer accounts for 0.01 wt% to 0.2 wt% of the cathode material by mass; optionally, the flux layer accounts for 0.02 wt% to 0.1 wt% of the cathode material by mass. When the flux layer accounts for a mass percentage of the cathode material within the above range, it can improve the adhesion and stability of the solid electrolyte layer on the lithium-containing transition metal oxide surface without affecting the specific capacity of the cathode material, thus balancing the cycle performance, storage performance, and capacity of the secondary battery.

[0070] In some embodiments, the thickness of the flux layer is 5 nm to 30 nm. Optionally, the thickness of the flux layer is 10 nm to 20 nm. A flux layer thickness within the above range can improve the adhesion and stability of the solid electrolyte layer on the lithium-containing transition metal oxide surface without affecting the specific capacity of the cathode material, thus balancing the cycle performance, storage performance, and capacity of the secondary battery.

[0071] In some embodiments, the solid electrolyte layer comprises Li d M2X d+3 The material comprises, wherein 1≤d≤6, M2 includes one or more of Al, Ga, In, Y, Zr, Nb, Sc, Ti, Mn, and La; and X includes one or more of halogens, S, O, and P. The above materials exhibit high ionic conductivity, which can enhance the diffusion rate of active ions at the interface between lithium-containing transition metal oxides and solid electrolytes, thereby reducing polarization and improving the cycle performance of secondary batteries.

[0072] In some embodiments, the solid electrolyte layer comprises an oxide solid electrolyte and / or a phosphate solid electrolyte. Oxide solid electrolytes and / or phosphate solid electrolytes have high ionic conductivity, which can enhance the diffusion rate of active ions at the interface between the lithium-containing transition metal oxide and the solid electrolyte, thereby reducing polarization and improving the cycle performance of the secondary battery.

[0073] In some embodiments, the solid electrolyte layer comprises an oxide solid electrolyte and / or a phosphate solid electrolyte. Exemplarily, the oxide solid electrolyte comprises a lithium lanthanum zirconium oxide series oxide or a tin oxide solid electrolyte, such as Li7La3Zr2O. 12 Phosphate solid electrolytes include LATP or LASP. Oxide solid electrolytes and / or phosphate solid electrolytes have high ionic conductivity, which can improve the diffusion rate of active ions at the interface between lithium-containing transition metal oxides and solid electrolytes, thus helping to reduce polarization and improve the cycle performance of secondary batteries.

[0074] In some embodiments, the solid electrolyte layer accounts for 0.05 wt% to 1 wt% of the mass of the cathode material, optionally 0.1 wt% to 0.5 wt%. This allows for an increase in the diffusion rate of active ions at the interface between the lithium-containing transition metal oxide and the solid electrolyte without excessively affecting the specific capacity of the cathode material, thus balancing the cycle performance and capacity of the secondary battery.

[0075] In some embodiments, the thickness of the solid electrolyte layer is 50 nm to 200 nm. This allows for an increase in the diffusion rate of active ions at the interface between the lithium-containing transition metal oxide and the solid electrolyte without excessively affecting the specific capacity of the cathode material, thus balancing the cycle performance and capacity of the secondary battery.

[0076] In some embodiments, the lithium-containing transition metal oxide includes the chemical formula Li a Ni b M1 c The O2 material, wherein M1 includes one or more of Co, Mn, Al, Mg, Ti, and Zr, with 0.9≤a≤1.1, 0.8≤b≤1, and 0≤c≤0.2. The above-mentioned lithium-containing transition metal oxides exhibit high capacity, which is beneficial for further improving battery capacity.

[0077] In some implementations, 0.9 ≤ b ≤ 1. This results in a higher specific capacity for the cathode material, which is beneficial for improving the energy density of the secondary battery.

[0078] In some implementations, 0 ≤ c ≤ 0.1.

[0079] In some embodiments, the lithium-containing transition metal oxide includes LiNi. 0.8 Co 0.1 Mn 0.1 O2 and / or LiNi 0.9 Co 0.05 Mn 0.05 O2. The aforementioned lithium-containing transition metal oxides have higher specific capacity, which is more conducive to improving the energy density of secondary batteries.

[0080] In some embodiments, the volumetric particle size distribution of the cathode material is 8 μm ≤ Dv50 ≤ 15 μm. A volumetric particle size distribution within this range is beneficial for achieving a higher compaction density.

[0081] In some implementations, the compaction density of the cathode material at 3t is greater than or equal to 3g / cc. This is beneficial for further improving the energy density of the secondary battery.

[0082] In some embodiments, the positive current collector has two surfaces opposite each other in its own thickness direction, and the positive electrode film layer is disposed on either or both of the two opposite surfaces of the positive current collector.

[0083] In some embodiments, the positive current collector may be a metal foil or a composite current collector. For example, aluminum foil may be used as the metal foil. The composite current collector may include a polymer substrate and a metal layer formed on at least one surface of the polymer substrate. The composite current collector may be formed by forming a metal material (aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.) on a polymer substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0084] In some embodiments, the positive electrode film layer may optionally include a binder. As an example, the binder may include at least one of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), PVDF-tetrafluoroethylene-propylene terpolymer, PVDF-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, and fluorinated acrylate resin.

[0085] In some embodiments, the positive electrode film may optionally include a conductive agent. As an example, the conductive agent may include at least one selected from superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0086] In some embodiments, the positive electrode sheet can be prepared by dispersing the above-mentioned components for preparing the positive electrode sheet, such as positive electrode material, conductive agent, binder and any other components, in a solvent (e.g., N-methylpyrrolidone) to form a positive electrode slurry; coating the positive electrode slurry onto the positive electrode current collector, and then obtaining the positive electrode sheet after drying, cold pressing and other processes.

[0087] In this application, the composition of each layer of the positive electrode material can be reversed in the following way: Specifically, the battery is disassembled to obtain the positive electrode sheet, the positive electrode material is peeled off from the positive electrode current collector, and the peeled-off positive electrode material is subjected to XPS sputtering test. X-rays are used to sputter the material surface to different depths, within a sputtering depth of 20 nm to 100 nm, to detect the content of characteristic elements of the corresponding solid electrolyte layer (e.g., P in LATP, La in LLZO); subsequently, sputtering continues, and within a sputtering depth of 10 nm to 20 nm, the characteristic elements of the flux layer can be detected.

[0088] In this application, the thickness of the flux layer and the solid electrolyte layer can be determined by testing the cross-sectional morphology (CP) of the positive electrode sheet using an ion polishing instrument. Specifically, the battery is disassembled to obtain the positive electrode sheet, and the positive electrode material is peeled off from the positive current collector. The peeled-off positive electrode material is fixed on the sample stage; the sample stage is installed into the sample holder and locked in place, the power of the argon ion cross-sectional polishing instrument (e.g., the IB-09010CP argon ion cross-sectional polishing instrument from JEOL Corporation of Japan) is turned on, and a vacuum is applied (e.g., 10...). -7 Set the argon flow rate (e.g., 0.12 MPa) and polishing time (e.g., 90 min), and adjust the sample stage to rocking mode to begin polishing. After polishing, perform energy dispersive spectroscopy (EDS) elemental analysis on the cross-section. By differentiating the characteristic elements in the solid electrolyte layer (e.g., P in LATP, La in LLZO) and the flux layer, the flux layer, solid electrolyte layer, and lithium-containing transition metal oxide can be distinguished, thus allowing the determination of the thickness of the flux layer and solid electrolyte layer.

[0089] In this application, the volumetric particle sizes Dv50, Dv90, and Dv10 have meanings known in the art, representing the particle sizes corresponding to a cumulative volumetric distribution percentage of 50%, 90%, and 10%, respectively, and can be determined using instruments and methods known in the art. For example, they can be determined using a laser particle size analyzer, referring to GB / T 19077-2016. The testing instrument can be a Mastersizer 3000 laser particle size analyzer from Malvern Instruments Ltd., UK.

[0090] In this application, the term "powder compaction density" has a meaning known in the art and can be determined using instruments and methods known in the art. For example, it can be determined using an electronic pressure testing machine (e.g., a UTM7305 type electronic pressure testing machine) in accordance with GB / T 24533-2009. An exemplary test method is as follows: Weigh 1g of sample powder and add it to a container with a bottom area of ​​1.327cm². 2 In the mold, the pressure is increased to 3t, held for 30s, then depressurized and held for 10s. The compaction density of the powder under 3t pressure is then recorded and calculated.

[0091] Negative electrode sheet

[0092] The negative electrode sheet includes a negative current collector and a negative electrode film layer disposed on at least one surface of the negative current collector, the negative electrode film layer including a negative electrode material.

[0093] As an example, the negative electrode current collector has two surfaces opposite each other in its own thickness direction, and the negative electrode film layer is disposed on either or both of the two opposite surfaces of the negative electrode current collector.

[0094] In some embodiments, the negative electrode current collector may be a metal foil or a composite current collector. For example, copper foil may be used as the metal foil. The composite current collector may include a polymer material substrate and a metal layer formed on at least one surface of the polymer material substrate. The composite current collector may be formed by forming a metal material (copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.) on a polymer material substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0095] In some embodiments, the negative electrode material may be a negative electrode material known in the art for use in batteries. As an example, the negative electrode material may include at least one of the following materials: artificial graphite, natural graphite, soft carbon, hard carbon, silicon-based materials, tin-based materials, and lithium titanate, etc. Silicon-based materials may be selected from at least one of elemental silicon, silicon oxide compounds, silicon-carbon composites, silicon-nitrogen composites, and silicon alloys. Tin-based materials may be selected from at least one of elemental tin, tin oxide compounds, and tin alloys. However, this application is not limited to these materials, and other conventional materials that can be used as battery negative electrode materials may also be used. These negative electrode materials may be used alone or in combination of two or more.

[0096] In some embodiments, the negative electrode material includes one or more of graphite, soft carbon, hard carbon, and silicon carbon.

[0097] In some embodiments, the negative electrode film layer may optionally include a binder. The binder may be selected from at least one of styrene-butadiene rubber (SBR), polyacrylic acid (PAA), sodium polyacrylate (PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), polymethacrylic acid (PMAA), and carboxymethyl chitosan (CMCS).

[0098] In some embodiments, the negative electrode film may optionally include a conductive agent. The conductive agent may be selected from at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0099] In some embodiments, the negative electrode film may optionally include other additives, such as thickeners (e.g., sodium carboxymethyl cellulose (CMC-Na)).

[0100] In some embodiments, the positive electrode sheet can be prepared by dispersing the components used to prepare the positive electrode sheet, such as negative electrode material, conductive agent, binder and any other components, in a solvent (e.g., deionized water) to form a negative electrode slurry; coating the negative electrode slurry onto a negative electrode current collector, and then obtaining the positive electrode sheet after drying, cold pressing and other processes.

[0101] electrolyte

[0102] The electrolyte acts as a conductor of ions between the positive electrode plates. This application does not impose specific restrictions on the type of electrolyte; it can be selected according to requirements.

[0103] In some embodiments, the electrolyte includes an electrolyte salt, which includes at least one of sodium hexafluorophosphate, sodium tetrafluoroborate, sodium perchlorate, sodium hexafluoroarsenate, sodium difluorosulfonamide, sodium ditrifluoromethanesulfonamide, sodium trifluoromethanesulfonate, sodium difluorophosphate, sodium difluorooxalate borate, sodium dioxalate borate, sodium difluorodioxalate phosphate, and sodium tetrafluorooxalate phosphate.

[0104] In some embodiments, the electrolyte further includes a solvent, which includes at least one selected from ethylene carbonate, propylene carbonate, methyl ethyl carbonate, diethyl carbonate, dimethyl carbonate, dipropyl carbonate, methyl propyl carbonate, ethyl propyl carbonate, butyl carbonate, fluoroethylene carbonate, methyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, ethyl butyrate, 1,4-butyrolactone, sulfolane, dimethyl sulfone, methyl ethyl sulfone, and diethyl sulfone.

[0105] In some embodiments, the electrolyte may optionally include additives. For example, additives may include negative electrode film-forming additives, positive electrode film-forming additives, and may also include additives that can improve certain battery performance, such as additives that improve battery overcharge performance, additives that improve battery high-temperature or low-temperature performance, etc.

[0106] In some embodiments, the additives in the electrolyte may include, but are not limited to, one or more of fluoroethylene carbonate (FEC), difluoroethylene carbonate (DFEC), trifluoromethyl ethylene carbonate (TFPC), etc.

[0107] In some implementations, the positive electrode, the positive electrode sheet, and the separator can be fabricated into an electrode assembly using a winding process or a stacking process.

[0108] In some embodiments, the battery cell may include an outer packaging. This outer packaging can be used to encapsulate the electrode assembly and electrolyte described above.

[0109] In some embodiments, the outer packaging of the battery cell can be a rigid shell, such as a hard plastic shell, an aluminum shell, or a steel shell. The outer packaging of the battery cell can also be a flexible package, such as a pouch. The material of the flexible package can be plastic; examples of plastics include polypropylene, polybutylene terephthalate, and polybutylene succinate.

[0110] This application does not impose any particular limitation on the shape of the battery cell; it can be cylindrical, square, or any other arbitrary shape. For example, Figure 2 The example shown is a square-structured battery cell 5.

[0111] In some implementations, refer to Figure 3 The outer packaging may include a housing 51 and a top cover assembly 53. The housing 51 may include a base plate and side plates connected to the base plate, the base plate and side plates forming a receiving cavity. The housing 51 has an opening communicating with the receiving cavity, and the top cover assembly 53 can cover the opening to close the receiving cavity. The positive electrode sheet, positive electrode plate, and separator can be formed into an electrode assembly 52 through a winding process or a stacking process. The electrode assembly 52 is encapsulated within the receiving cavity. Electrolyte is immersed in the electrode assembly 52. ​​The number of electrode assemblies 52 contained in the battery cell 5 can be one or more, which can be selected by those skilled in the art according to specific practical needs.

[0112] In some implementations, individual battery cells can be assembled into a battery module. The number of individual battery cells contained in a battery module can be one or more, and the specific number can be selected by those skilled in the art based on the application and capacity of the battery module.

[0113] Figure 4 This is battery module 4, used as an example. (See reference...) Figure 4 In battery module 4, multiple battery cells 5 can be arranged sequentially along the length of battery module 4. Of course, they can also be arranged in any other manner. Furthermore, these multiple battery cells 5 can be fixed in place using fasteners.

[0114] Optionally, the battery module 4 may also include a housing with a receiving space in which multiple battery cells 5 are received.

[0115] In some embodiments, the battery modules described above can also be assembled into a battery pack, and the number of battery modules contained in the battery pack can be one or more, the specific number of which can be selected by those skilled in the art according to the application and capacity of the battery pack.

[0116] Figure 5 and Figure 6 This is battery pack 1 as an example. (See reference...) Figure 5 and Figure 6 The battery pack 1 may include a battery box and multiple battery modules 4 disposed within the battery box. The battery box includes an upper body 2 and a lower body 3, with the upper body 2 covering the lower body 3 to form a closed space for accommodating the battery modules 4. The multiple battery modules 4 can be arranged in any manner within the battery box.

[0117] Electrical appliances

[0118] In addition, a second aspect of this application provides an electrical device, which includes the secondary battery provided in this application. The secondary battery can be used as the power source of the electrical device or as the energy storage unit of the electrical device. The electrical device may include, but is 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, etc.

[0119] As an electrical device, you can choose individual battery cells, battery modules, or battery packs according to your usage requirements.

[0120] Figure 7 This is an example of an electrical device. The device could be a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle. To meet the high power and high energy density requirements of the secondary battery for this device, a battery pack or battery module can be used.

[0121] Another example device could be a mobile phone, tablet, or laptop. These devices typically require a slim and lightweight design and can use a single battery cell as their power source.

[0122] cathode materials

[0123] A third aspect of this application provides a cathode material, comprising a lithium-containing transition metal oxide, a solid electrolyte layer coated on the outer surface of the lithium-containing transition metal oxide, and a fluxing layer located between the lithium-containing transition metal oxide and the solid electrolyte layer; wherein, based on the total molar number of metal elements other than lithium, the molar percentage of Ni element is greater than or equal to 80% and less than or equal to 100%; the fluxing layer comprises one or more of alkali metal oxides, alkaline earth metal oxides, and aluminum oxides.

[0124] In this application, a fluxing layer is provided between the lithium-containing transition metal oxide and the solid electrolyte layer. Since the fluxing layer includes one or more of alkali metal oxides, alkaline earth metal oxides, and aluminum oxides, it can form molten metal oxides when heated (e.g., above 400°C). At high temperatures, the fluxing layer can exchange atoms with the lithium-containing transition metal oxide and the metals in the solid electrolyte, forming covalent bonds. This promotes interfacial fusion between the lithium-containing transition metal oxide and the solid electrolyte, improving the adhesion and stability of the solid electrolyte layer on the lithium-containing transition metal oxide surface, thus enhancing the stability of the cathode material. Using the cathode material in this application is beneficial for improving the cycle performance and storage performance of the secondary battery.

[0125] In some embodiments, the flux layer comprises alkali metal oxides and / or alkaline earth metal oxides. As examples, alkali metal oxides include one or more of lithium oxide, sodium oxide, potassium oxide, rubidium oxide, cesium oxide, and francium oxide. Alkaline earth metal oxides include one or more of beryllium oxide, magnesium oxide, calcium oxide, strontium oxide, barium oxide, and radium oxide. Alkali metal oxides and / or alkaline earth metal oxides are more likely to form a molten state upon heating and possess strong reactivity and atom exchange capacity. At high temperatures, alkali metal oxides and / or alkaline earth metal oxides more readily react with lithium-containing transition metal oxides and metal atoms in the solid electrolyte to form covalent bonds. Therefore, this is more beneficial for improving the stability of the cathode material, thereby improving the cycle performance and storage performance of the secondary battery.

[0126] In some embodiments, the fluxing layer includes one or more of MgO, CaO, Al2O3, SrO, BaO, Na2O, and K2O; optionally, the fluxing layer includes MgO and / or Na2O. These oxides can form a molten state when heated and possess strong reactivity and atom exchange capacity. Therefore, using these materials as the fluxing layer is more conducive to promoting interfacial fusion between the lithium-containing transition metal oxide and the solid electrolyte, thereby improving the stability of the cathode material and consequently enhancing the cycle performance and storage performance of the secondary battery.

[0127] In some embodiments, the flux layer accounts for 0.01 wt% to 0.2 wt% of the mass of the cathode material; alternatively, it accounts for 0.02 wt% to 0.1 wt%. This allows for improved adhesion and stability of the solid electrolyte layer on the lithium-containing transition metal oxide surface without affecting the specific capacity of the cathode material, thus balancing the cycle performance, storage performance, and capacity of the secondary battery.

[0128] In some embodiments, the thickness of the flux layer is 5 nm to 30 nm, and optionally, the thickness of the flux layer is 10 nm to 20 nm. This allows for improved adhesion and stability of the solid electrolyte layer on the lithium-containing transition metal oxide surface without affecting the specific capacity of the cathode material, thus balancing the cycle performance, storage performance, and capacity of the secondary battery.

[0129] In some embodiments, the solid electrolyte layer comprises Li d M2X d+3The material comprises, wherein 1≤d≤6, M2 includes one or more of Al, Ga, In, Y, Zr, Nb, Sc, Ti, Mn, and La; and X includes one or more of halogens, S, O, and P. The above materials exhibit high ionic conductivity, which can enhance the diffusion rate of active ions at the interface between lithium-containing transition metal oxides and solid electrolytes, thereby reducing polarization and improving the cycle performance of secondary batteries.

[0130] In some embodiments, the solid electrolyte layer comprises an oxide solid electrolyte and / or a phosphate solid electrolyte. Oxide solid electrolytes and / or phosphate solid electrolytes have high ionic conductivity, which can enhance the diffusion rate of active ions at the interface between the lithium-containing transition metal oxide and the solid electrolyte, thereby reducing polarization and improving the cycle performance of the secondary battery.

[0131] For example, the oxide solid electrolyte includes lithium lanthanum zirconium oxide series oxides or tin oxide solid electrolytes, such as Li7La3Zr2O. 12 Phosphate solid electrolytes include LATP or LASP.

[0132] In some embodiments, the solid electrolyte layer accounts for 0.05 wt% to 1 wt% of the mass of the cathode material, optionally 0.1 wt% to 0.5 wt%. This allows for an increase in the diffusion rate of active ions at the interface between the lithium-containing transition metal oxide and the solid electrolyte without excessively affecting the specific capacity of the cathode material, thus balancing the cycle performance and capacity of the secondary battery.

[0133] In some embodiments, the thickness of the solid electrolyte layer is 50 nm to 200 nm. This allows for an increase in the diffusion rate of active ions at the interface between the lithium-containing transition metal oxide and the solid electrolyte without excessively affecting the specific capacity of the cathode material, thus balancing the cycle performance and capacity of the secondary battery.

[0134] In some embodiments, the lithium-containing transition metal oxide includes the chemical formula Li a Ni b M1 c The material containing O2 includes one or more of Co, Mn, Al, Mg, Ti, and Zr, with a molecular weight of 0.9 ≤ a ≤ 1.1, 0.8 ≤ b ≤ 1, and 0 ≤ c ≤ 0.2. These lithium-containing transition metal oxides exhibit high capacity, which is beneficial for further improving battery capacity.

[0135] In some implementations, 0.9 ≤ b ≤ 1. This results in a higher specific capacity for the cathode material, which is beneficial for improving the energy density of the secondary battery.

[0136] In some implementations, 0 ≤ c ≤ 0.1.

[0137] In some embodiments, the lithium-containing transition metal oxide includes LiNi. 0.8 Co 0.1 Mn 0.1 O2 and / or LiNi 0.9 Co 0.05 Mn 0.05 O2. The aforementioned lithium-containing transition metal oxides have higher specific capacity, which is more conducive to improving the energy density of secondary batteries.

[0138] In some embodiments, the volumetric particle size distribution of the cathode material is 8 μm ≤ Dv50 ≤ 15 μm. A volumetric particle size distribution within this range is beneficial for improving the material's compaction density.

[0139] In some implementations, the compaction density of the cathode material is greater than or equal to 3 g / cc. This is beneficial for further improving the energy density of the secondary battery.

[0140] Preparation method of positive electrode material

[0141] The fourth aspect of this application provides a method for preparing a cathode material, comprising the following steps: S1, mixing a transition metal precursor material with a lithium source and a fluxing material uniformly, and then performing a first sintering treatment to obtain a lithium-containing transition metal oxide and a fluxing layer located on the outer surface of the lithium-containing transition metal oxide, wherein the fluxing material includes one or more of alkali metal oxides, alkali metal hydroxides, alkaline earth metal oxides, alkaline earth metal hydroxides, aluminum oxides, and aluminum hydroxides; S2, mixing the lithium-containing transition metal oxide and the fluxing layer obtained in step S1 uniformly with a solid electrolyte material, and then performing a second sintering treatment to obtain a solid electrolyte layer coated with the fluxing layer.

[0142] In this application, a lithium-containing transition metal oxide and a flux layer on the outer surface of the lithium-containing transition metal oxide are prepared through a first sintering process. A solid electrolyte layer covering the flux layer is then formed through a second sintering process. Since the flux material includes one or more of alkali metal oxides, alkali metal hydroxides, alkaline earth metal oxides, alkaline earth metal hydroxides, aluminum oxides, and aluminum hydroxides, it can melt when heated. During the first and second sintering processes, the flux material melts, accelerating the exchange of metal atoms between the transition metal precursor material and the solid electrolyte layer, forming covalent bonds. This promotes interfacial fusion between the lithium-containing transition metal oxide and the solid electrolyte, improving the adhesion and stability of the solid electrolyte layer on the lithium-containing transition metal oxide surface, thus enhancing the stability of the formed cathode material. The secondary battery prepared using the method provided in this application exhibits improved cycle performance and storage performance.

[0143] In some embodiments, in step S1, the fluxing material includes one or more of alkali metal oxides, alkali metal hydroxides, alkaline earth metal oxides, and alkaline earth metal hydroxides. These fluxing materials are more likely to form a molten state upon heating and possess strong reactivity. During the first and second sintering processes, the fluxing material more easily accelerates the exchange between metal atoms in the lithium-containing transition metal oxide and the solid electrolyte, while simultaneously forming covalent bonds. Therefore, it is more conducive to promoting interfacial fusion between the lithium-containing transition metal oxide and the solid electrolyte, thereby improving the stability of the cathode material and, consequently, enhancing the cycle performance and storage performance of the secondary battery.

[0144] In some embodiments, the fluxing material includes one or more of MgO, CaO, Al2O3, SrO, BaO, Na2O, K2O, NaOH, and KOH. Optionally, the fluxing material includes one or more of MgO, Na2O, and NaOH. These oxides can form a molten state when heated and possess strong reactivity and atom exchange capacity. Therefore, using these materials as fluxing materials is more conducive to promoting interfacial fusion between lithium-containing transition metal oxides and solid electrolytes, thereby improving the stability of the cathode material.

[0145] In some embodiments, the flux layer accounts for 0.01 wt% to 0.2 wt% of the cathode material by mass, optionally 0.02 wt% to 0.1 wt%. This allows for improved adhesion and stability of the solid electrolyte layer on the lithium-containing transition metal oxide surface without affecting the specific capacity of the cathode material, thus balancing the cycle performance, storage performance, and capacity of the secondary battery.

[0146] In some embodiments, transition metal precursor materials can be prepared by mixing a Ni salt solution and an M1 salt solution (including one or more of Co, Mn, Al, Mg, Ti, and Zr salts) to obtain a mixed solution A. Then, the mixed solution A, the precipitant NaOH, and the complexing agent ammonia are pumped into a reaction vessel, and the pH of the material in the reaction vessel is controlled at 11-13. The co-precipitation reaction is carried out at 45-60°C for 12-24 hours. The material obtained from the reaction is then washed and dried to obtain the transition metal precursor material.

[0147] In some embodiments, the chemical formula of the solid electrolyte material is Li. d M2X d+3 Where 1≤d≤6, M2 includes one or more of Al, Ga, In, Y, Zr, Nb, Sc, Ti, Mn, and La; X includes one or more of halogens, S, O, and P.

[0148] In some embodiments, the solid electrolyte material includes oxide solid electrolytes and / or phosphate solid electrolytes. Exemplarily, the oxide solid electrolyte includes lithium lanthanum zirconium oxide series oxides or tin oxide solid electrolytes, such as Li7La3Zr2O. 12 Phosphate solid electrolytes include LATP or LASP.

[0149] In some embodiments, the solid electrolyte layer accounts for 0.05 wt% to 1 wt% of the mass of the cathode material, optionally 0.1 wt% to 0.5 wt%. This allows for an increase in the diffusion rate of active ions at the interface between the lithium-containing transition metal oxide and the solid electrolyte without excessively affecting the specific capacity of the cathode material, thus balancing the cycle performance and capacity of the secondary battery.

[0150] In some embodiments, in step S1, the lithium source is one or more of LiOH·H2O, Li2CO3, Li2SO4, LiNO3, LiC2O4, and CH3COOLi; optionally, the lithium source is LiOH·H2O or Li2CO3.

[0151] In some embodiments, the molar ratio of lithium in the lithium source to metal in the transition metal precursor material is 1.0 to 1.2; optionally, it is 1.01 to 1.05. This is beneficial for maximizing the specific capacity of the lithium-containing transition metal oxide.

[0152] In some embodiments, in step S2, the second sintering treatment is carried out at 500°C to 700°C for 4 to 10 hours; alternatively, it is carried out at 550°C to 650°C for 6 to 8 hours. This facilitates the formation of a solid electrolyte coating layer on the surface of the flux layer.

[0153] In some embodiments, in step S1, the first sintering treatment satisfies one or more of the following characteristics: (1) the sintering temperature is 600℃~800℃, optionally 700℃~750℃; (2) the sintering time is 8h~18h, optionally 10h~15h; (3) the heating rate is 0.5℃ / min~5℃ / min, optionally 1℃ / min~3℃ / min; (4) the sintering atmosphere is air or oxygen. This facilitates the formation of lithium-containing transition metal oxides and the formation of a solid electrolyte coating layer on the surface of the lithium-containing transition metal oxides.

[0154] Example

[0155] The following describes embodiments of this application. The embodiments described below are exemplary and are only used to explain this application, and should not be construed as limiting this application. Where specific techniques or conditions are not specified in the embodiments, they are performed according to the techniques or conditions described in the literature in this field or according to the product instructions. Reagents or instruments used, unless otherwise specified, are all conventional products that can be obtained commercially.

[0156] Example 1

[0157] Preparation of a positive electrode material

[0158] S1:1) Mix Ni salt solution, Co salt solution and Mn salt solution evenly to obtain mixed solution A. Then, pump mixed solution A, NaOH precipitant and ammonia complexing agent into the reactor and adjust the pH of the material in the reactor to 12. Co-precipitate at 50℃ for 18h. Wash and dry the material obtained from the reaction to obtain transition metal precursor material.

[0159] 2) The transition metal precursor material prepared in step 1) is mixed evenly with LiOH·H2O and flux NaOH and then subjected to a first sintering treatment to obtain a lithium-containing transition metal oxide and a flux layer Na2O on the outer surface of the lithium-containing transition metal oxide; wherein, the molar ratio of lithium element in the lithium source to metal element in the transition metal precursor material is 1.03, the amount of flux added is 0.05% of the mass of the lithium-containing transition metal oxide material, and the first sintering treatment is carried out in air atmosphere, heated to 720℃ at a heating rate of 2℃ / min, and held for 15h;

[0160] S2: The lithium-containing transition metal oxide obtained in step S1 is homogenized with the solid electrolyte material and then subjected to a second sintering treatment to obtain the cathode material. The second sintering treatment is carried out at 600°C for 7 hours. The amount of solid electrolyte material added is 0.2 wt% of the transition metal precursor material. In the cathode material prepared in Example 1, the thickness of the flux layer is 10 nm and the thickness of the solid electrolyte layer is 100 nm.

[0161] Preparation of a positive electrode sheet

[0162] The positive electrode material obtained in Example 1 was thoroughly mixed with the conductive agent acetylene black and the binder polyvinylidene fluoride (PVDF) in an N-methylpyrrolidone solvent system at a weight ratio of 94:3:3. The mixture was then coated onto aluminum foil, dried, and cold-pressed to obtain the positive electrode sheet.

[0163] Preparation of a negative electrode sheet

[0164] The negative electrode active material hard carbon, nano-level conductive agent acetylene black, binder styrene-butadiene rubber (SBR), and thickener sodium carboxymethyl cellulose (CMC) are thoroughly mixed in a deionized water solvent system at a weight ratio of 95:2:2:1. The mixture is then coated on both sides onto a copper foil with a thickness of 6 μm, dried, and cold-pressed to obtain the negative electrode sheet.

[0165] Electrolyte

[0166] An organic solvent was prepared by mixing equal volumes of ethylene carbonate (EC), diethyl carbonate (DEC), and propylene carbonate (PC). LiPF6 was then dissolved in the organic solvent to prepare an electrolyte with a concentration of 1 mol / L.

[0167] Separator film

[0168] A polyethylene film with a thickness of 13 μm was used as the isolation membrane.

[0169] Preparation of a secondary battery

[0170] The positive electrode, separator, and negative electrode are stacked in sequence, with the separator positioned between the positive and negative electrodes to provide insulation. This stacking process yields a bare battery cell. The bare battery cell is then placed in outer packaging, filled with the prepared electrolyte, and sealed to obtain a secondary battery.

[0171] Performance test of a secondary battery

[0172] 1) Cyclic performance test

[0173] At 25℃, the following steps were followed for testing:

[0174] ① Let stand for 5 minutes;

[0175] ② Charge at a constant current of 1C to 4.25V, then charge at a constant voltage of 4.25V to a current of 0.05mA;

[0176] ③ Let stand for 5 minutes;

[0177] ④ Discharge at a constant current of 1C to 2.8V, and record the discharge capacity D1 of the first cycle;

[0178] ⑤ Repeat steps ① to ④ above 100 times, and record the discharge capacity D100 on the 100th cycle;

[0179] The capacity retention rate after 100 cycles = D100 / D1*100%, and the capacity test results are shown in Table 2.

[0180] 2) Storage performance test

[0181] The prepared secondary battery was charged at a constant current of 1C to 4.25V, then charged at a constant voltage of 4.25V to a current of 0.05mA. After standing for 5 minutes, it was discharged at a constant current of 1C to 2.8V, and the discharge capacity C1 of the first cycle was recorded. Then, the secondary battery was charged at a constant current of 1C to 4.25V, then charged at a constant voltage of 4.25V to a current of 0.05mA, and stored at 60°C for 90 days. After being taken out, it was discharged at a constant current of 1C to 2.8V, and the discharge capacity C2 was recorded.

[0182] The capacity retention rate after 90 days of storage at 60℃ is calculated as C2 / C1*100%, and the test results are shown in Table 2.

[0183] Examples 2-9

[0184] The cathode material was prepared in a manner similar to that in Example 1 and assembled into a secondary battery. The only difference was that the fluxing material and / or the molar ratio of lithium in the lithium source to the metal in the transition metal precursor material were adjusted during the preparation of the cathode material. The specific cathode materials obtained are shown in Table 1 below.

[0185] Comparative Example 1

[0186] The cathode material was prepared in a similar manner to that in Example 1 and assembled into a secondary battery. The only difference was that no fluxing material was added when preparing the cathode material. Please refer to Table 1 below for details.

[0187] Comparative Example 2

[0188] The cathode material was prepared in a similar manner to that in Example 1 and assembled into a secondary battery. The difference was that the molar ratio of lithium in the lithium source to metal in the transition metal precursor material was adjusted, and no fluxing material was added when preparing the cathode material. Please refer to Table 1 below for details.

[0189] Table 1 below shows the parameters of the cathode materials prepared in Examples 1-9 and Comparative Examples 1 and 2, as well as the performance test results of the secondary batteries.

[0190] Table 1

[0191]

[0192]

[0193] In Table 1, " / " indicates that the symbol does not exist.

[0194] As can be seen from Table 1, compared with Comparative Example 1 (without a fluxing layer), Examples 1-7, through the use of lithium-containing transition metal oxide LiNi 0.9 Co 0.05 Mn 0.05The addition of a fluxing layer between O2 and the solid electrolyte layer LATP significantly improved the cycle performance and storage performance of the secondary battery. Compared to Comparative Example 2 (without a fluxing layer), Examples 8 and 9 improved the performance of the secondary battery by using a lithium-containing transition metal oxide LiNi. 0.8 Co 0.1 Mn 0.1 A fluxing layer is placed between O2 and the solid electrolyte layer LATP, which significantly improves the cycle performance and storage performance of the secondary battery.

[0195] Examples 10-13

[0196] The cathode material was prepared in a similar manner to that in Example 1 and assembled into a secondary battery. The only difference was the amount of fluxing material added during the preparation of the cathode material. Please refer to Table 2 below for details.

[0197] Table 2 below shows the parameters of the cathode materials prepared in Examples 10-13 and the performance test results of the secondary batteries.

[0198] Table 2

[0199]

[0200] As can be seen from Table 2, by setting the mass percentage of the flux layer in the cathode material to 0.01wt% to 0.2wt%, the cycle performance and storage performance of the secondary battery are significantly improved.

[0201] It should be noted that this application is not limited to the above-described embodiments. The above embodiments are merely examples, and any embodiments with the same structure and effect as the technical concept within the scope of this application are included in the technical scope of this application. Furthermore, various modifications that can be conceived by those skilled in the art to the embodiments, and other ways of constructing by combining some of the constituent elements of the embodiments, without departing from the spirit of this application, are also included in the scope of this application.

Claims

1. A secondary battery, characterized in that, The secondary battery comprises: a positive electrode tab, a negative electrode tab, a separator disposed between the positive electrode tab and the negative electrode tab, and an electrolyte, the positive electrode tab comprises a positive electrode current collector and a positive electrode film layer disposed on at least one surface of the positive electrode current collector and comprising a positive electrode material, the positive electrode material comprises a lithium-containing transition metal oxide, a solid-state electrolyte layer coated on an outer surface of the lithium-containing transition metal oxide, and a fluxing layer located between the lithium-containing transition metal oxide and the solid-state electrolyte layer, in the lithium-containing transition metal oxide, the mole percentage of Ni element based on the total moles of metal elements other than lithium is greater than or equal to 80% and less than or equal to 100%, the fluxing layer comprises one or more of alkali metal oxides, alkaline earth metal oxides, and aluminum oxides.

2. The secondary battery according to claim 1, characterized by The fluxing layer comprises alkali metal oxides and / or alkaline earth metal oxides.

3. The secondary battery according to claim 1, characterized by The fluxing layer comprises one or more of MgO, CaO, Al2O3, SrO, BaO, Na2O, and K2O.

4. The secondary battery according to any one of claims 1 to 3, characterized by The fluxing layer comprises MgO and / or Na2O.

5. The secondary battery according to any one of claims 1 to 4, characterized by The mass percentage of the fluxing layer in the positive electrode material is 0.01wt%-0.2wt%.

6. The secondary battery according to any one of claims 1 to 5, characterized by The mass percentage of the fluxing layer in the positive electrode material is 0.02wt%-0.1wt%.

7. The secondary battery according to any one of claims 1 to 6, characterized by The thickness of the fluxing layer is 5nm-30nm.

8. The secondary battery according to any one of claims 1 to 7, characterized by, The solid-state electrolyte layer includes a material of a chemical formula of Li d M2X d+3 , wherein 1≤d≤6, M2 includes one or more of Al, Ga, In, Y, Zr, Nb, Sc, Ti, Mn, La, and X includes one or more of halogen, S, O, and P.

9. The secondary battery according to any one of claims 1 to 8, characterized by, The solid-state electrolyte layer comprises oxide solid-state electrolytes and / or phosphate solid-state electrolytes.

10. The secondary battery according to any one of claims 1 to 9, characterized by The mass percentage of the solid-state electrolyte layer in the positive electrode material is 0.05wt%-1wt%.

11. The secondary battery according to any one of claims 1 to 10, characterized by The thickness of the solid-state electrolyte layer is 50nm-200nm.

12. The secondary battery according to any one of claims 1 to 11, characterized by The lithium-containing transition metal oxide includes a material of a chemical formula of Li a Ni b M1 c O2, wherein M1 includes one or more of Co, Mn, Al, Mg, Ti, Zr, 0.6≤a≤1.1, 0.8≤b≤1, and 0≤c≤0.

2.

13. The secondary battery according to claim 12, characterized by 0.9≤b≤1。 14. The secondary battery according to any one of claims 1 to 13, characterized by The volume particle size distribution of the positive electrode material is 8μm≤Dv50≤15μm.

15. The secondary battery according to any one of claims 1 to 14, characterized by The compaction density of the positive electrode material at 3t is greater than or equal to 3g / cc.

16. An electrical device, comprising: The secondary battery comprises any one of claims 1-15.

17. A positive electrode material, characterized in that, The secondary battery comprises a lithium-containing transition metal oxide, a solid-state electrolyte layer coated on an outer surface of the lithium-containing transition metal oxide, and a fluxing layer located between the lithium-containing transition metal oxide and the solid-state electrolyte layer, in the lithium-containing transition metal oxide, the mole percentage of Ni element based on the total moles of metal elements other than lithium is greater than or equal to 80% and less than or equal to 100%, the fluxing layer comprises one or more of alkali metal oxides, alkaline earth metal oxides, and aluminum oxides.

18. The cathode material of claim 17, wherein, The fluxing layer comprises alkali metal oxides and / or alkaline earth metal oxides.

19. The cathode material of claim 17, wherein, The fluxing layer comprises one or more of MgO, CaO, Al2O3, SrO, BaO, Na2O, and K2O.

20. The cathode material of any one of claims 17-19, wherein, The fluxing layer comprises MgO and / or Na2O.

21. The cathode material of any one of claims 17-20, wherein, The mass percentage of the fluxing layer in the positive electrode material is 0.01wt%-0.2wt%.

22. The cathode material of any one of claims 17-21, wherein, The mass percentage of the fluxing layer in the positive electrode material is 0.02wt%-0.1wt%.

23. The cathode material of any one of claims 17-22, wherein, The thickness of the fluxing layer is 5nm-30nm.

24. The cathode material of any one of claims 17-23, wherein, The solid-state electrolyte layer includes a chemical formula of Li d M2X d+3 material, wherein 1≤d≤6, M2 includes one or more of Al, Ga, In, Y, Zr, Nb, Sc, Ti, Mn, La, and X includes one or more of halogen, S, O, and P.

25. The cathode material of any one of claims 17-24, wherein, The solid-state electrolyte layer comprises oxide solid-state electrolytes and / or phosphate solid-state electrolytes.

26. The cathode material of any one of claims 17-25, wherein, The mass percentage of the solid-state electrolyte layer in the positive electrode material is 0.05wt%-1wt%.

27. The cathode material of any one of claims 17-26, wherein, The thickness of the solid-state electrolyte layer is 5nm-200nm.

28. The cathode material of any one of claims 17-27, wherein, The lithium-containing transition metal oxide includes a material of a chemical formula of Li a Ni b M1 c O2, wherein M1 includes one or more of Co, Mn, Al, Mg, Ti, Zr, 0.9≤a≤1.1, 0.8≤b≤1, 0≤c≤0.

2.

29. The cathode material of claim 28, wherein, 0.9≤b≤1。 30. The cathode material of any one of claims 17-29, wherein, The positive electrode material has a volume particle size distribution of 8 μm≤Dv50≤15 μm.

31. The cathode material of any one of claims 17-30, wherein, The positive electrode material has a compaction density of 3 g / cc or more.

32. A method of producing a positive electrode material, characterized by, The method comprises the following steps: S1, uniformly mixing a transition metal precursor material with a lithium source and a fluxing material, and then performing a first sintering treatment to obtain a lithium-containing transition metal oxide and a fluxing layer on the outer surface of the lithium-containing transition metal oxide, wherein the fluxing material comprises one or more of alkali metal oxides, alkali metal hydroxides, alkaline earth metal oxides, alkaline earth metal hydroxides, aluminum oxides, and aluminum hydroxides, S2, uniformly mixing the lithium-containing transition metal oxide and the fluxing layer obtained in step S1 with a solid electrolyte material, and then performing a second sintering treatment to obtain a solid electrolyte layer coated with the fluxing layer.

33. The method of claim 32, wherein, In step S1, the fluxing material comprises one or more of alkali metal oxides, alkali metal hydroxides, alkaline earth metal oxides, and alkaline earth metal hydroxides.

34. The method of claim 32 or 33, wherein, In step S1, the fluxing material comprises one or more of MgO, CaO, Al2O3, SrO, BaO, Na2O, K2O, NaOH, and KOH.

35. The method of any one of claims 32-34, wherein, The mass proportion of the fluxing layer in the positive electrode material is 0.01wt% to 0.2wt%.

36. The method of any one of claims 32-35, wherein, The mass proportion of the solid electrolyte layer in the positive electrode material is 0.05wt% to 1wt%.

37. The method of any one of claims 32-36, wherein, In step S1, the lithium source is one or more of LiOH·H2O, Li2CO3, Li2SO4, LiNO3, LiC2O4, and CH3COOLi.

38. The method of any one of claims 32-37, wherein, The molar ratio of lithium in the lithium source to metal elements in the transition metal precursor material is 1.0 to 1.

2.

39. The method of any one of claims 32-38, wherein, In step S2, the second sintering treatment is performed at 500°C to 700°C for 4h to 10h.

40. The method of any one of claims 32-39, wherein, In step S1, the first sintering treatment satisfies one or more of the following features: (1) the sintering temperature is 600°C to 800°C, (2) the sintering time is 8h to 18h, (3) the heating rate is 0.5°C / min to 5°C / min, and (4) the sintering atmosphere is air or oxygen.

Images