Solid electrolyte material and preparation method thereof, positive electrode active material, positive electrode sheet, solid-state battery and electrical equipment

Abstract

The present application discloses a solid electrolyte material and a preparation method thereof, a positive electrode active material, a positive electrode sheet, a solid-state battery and an electrical device. The solid electrolyte material includes Li 7‑nα‑β M α La3Zr 2‑x M' x O 12 ; Among them, 0

Description

Technical Field

[0001] The present application relates to the field of batteries, and in particular to solid electrolyte materials and preparation methods thereof, positive electrode active materials, positive electrode sheets, solid-state batteries, and electrical equipment. Background Art

[0002] Lithium lanthanum zirconate (Li7La3Zr2O 12 LLZO (lanthanum zirconate, also known as LLZO) is currently the most widely used solid-state electrolyte material with the best overall performance. Its advantages include high ionic conductivity, stable electrochemical performance, excellent thermal stability, a wide electrochemical window, non-toxicity, and stable contact with metallic lithium. These advantages give it broad application prospects and research value in the field of future all-solid-state lithium batteries. However, the uneven distribution of elements in the related art lithium lanthanum zirconate solid-state electrolyte material can affect its ionic conductivity to a certain extent. Summary of the Invention

[0003] The first aspect of the present application provides a solid electrolyte material, including Li 7-nα-β M α La3Zr 2-x M' x O 12 Wherein, 0<α<1, 0≤x≤1, β=(n'-4)x, n is the valence of element M, n' is the valence of element M', M includes at least one of B, Ca, Al, Y, Sc, Fe, and Ga, and M' includes at least one of Ti, Mn, Co, Sn, Ge, Hf, Mo, W, Sb, Nb, and Ta; the standard deviation of the element concentration of the solid electrolyte material is N, and satisfies N≤3%. This improves the uniformity of element distribution in the solid electrolyte material, optimizes the crystal structure of the solid electrolyte material, reduces the tortuosity of active metal ion transmission in the solid electrolyte material, and thereby improves the ionic conductivity and structural stability of the solid electrolyte material.

[0004] According to some embodiments of the present application, N is ≤ 2%. This further improves the uniformity of element distribution in the solid electrolyte material, optimizes the crystal structure of the solid electrolyte material, reduces the tortuosity of active metal ion transport in the solid electrolyte material, and thereby improves the ionic conductivity and structural stability of the solid electrolyte material.

[0005] According to some embodiments of the present application, the minimum cross-sectional area of ​​the lithium ion transmission channel of the solid electrolyte material is S, and satisfies Optionally, As a result, the cross-sectional area of ​​the lithium ion transmission channel is increased, the transmission rate of lithium ions is improved, and the ionic conductivity of the solid electrolyte material is improved.

[0006] According to some embodiments of the present application, the solid electrolyte material satisfies at least one of the following conditions: the median particle size D of the solid electrolyte material 50 Satisfy: 0.5μm≤D 50 ≤10μm, optionally, 1μm≤D 50 ≤2.5μm; the specific surface area A of the solid electrolyte material satisfies: 0.2m 2 / g≤A≤2m 2 / g, optionally, 0.5m 2 / g≤A≤0.9m 2 / g.

[0007] According to some embodiments of the present application, the solid electrolyte material includes Li 6.4 La3Zr2Al 0.2 O 12 、Li 6.2 La3Zr 1.8 Al 0.2 Nb 0.2 O 12 、Li6La3Zr2Al 0.2 Ca 0.2 O 12 、Li6La3Zr 1.8 Y 0.2 W 0.2 O 12 、Li 6.4 La3Zr 1.8 Al 0.2 Ti 0.2 O 12 At least one of .

[0008] The second aspect of the present application provides a method for preparing the solid electrolyte material of the first aspect of the present application, comprising: mixing a La source solution, a Zr source solution, and an M source solution to form a mixed salt solution; placing the mixed salt solution, a precipitant solution, a complexing agent solution, and a surfactant in a reactor for coprecipitation reaction, and drying to obtain M α La3Zr 2-x Co-precipitation precursor, based on the total mass of the La source, the Zr source, and the M source, the mass proportion of the surfactant is 0.1%-5%; the lithium source, the M' source and the M α La3Zr 2-xThe co-precipitated precursors are mixed to obtain a mixture; the mixture is sintered for the first time and crushed to obtain the solid electrolyte material, wherein the temperature of the first sintering is T1, and satisfies 750°C ≤ T1 ≤ 1000°C, and can be optionally 780°C ≤ T1 ≤ 950°C. Thus, the solid electrolyte material prepared by this method has all the characteristics and advantages of the aforementioned solid electrolyte material, which will not be repeated here. In general, it has at least the advantages of low sintering temperature during the preparation process, uniform distribution of elements in the solid electrolyte material, and high ionic conductivity.

[0009] According to some embodiments of the present application, the method satisfies at least one of the following conditions: based on the total mass of the La source, the Zr source, and the M source, the mass proportion of the surfactant is 0.2%-2%; the surfactant includes at least one of methanol, ethanol, n-propanol, isopropanol, ethylene glycol, propylene glycol, glycerol, acetone, N,N-dimethylformamide, dimethyl sulfoxide, and polyethylene glycol. Thus, by adding a surfactant during the coprecipitation process, the wetting performance and emulsification ability of the metal element are improved, and the uniformity of the mixing of the metal ions in the mixed salt is improved, thereby obtaining a more uniform M of the metal element. α La3Zr 2-x Co-precipitation precursor.

[0010] According to some embodiments of the present application, the method further includes: performing pre-sintering before the first sintering, performing a second sintering after the first sintering, the temperature of the pre-sintering is T2, the temperature of the second sintering is T3, the holding time of the first sintering is t1, the heating rate of the first sintering is v1, the holding time of the pre-sintering is t2, the heating rate of the pre-sintering is v2, the holding time of the second sintering is t3, and the method satisfies at least one of the following conditions: 300°C ≤ T2 ≤ 700°C, which can be 4 50℃≤T2≤650℃;600℃≤T3≤750℃,optionally 650℃≤T3≤730℃;0.5℃ / min≤V2≤10℃ / min,optionally 1℃ / min≤V2≤5℃ / min;0.5℃ / min≤V1≤10℃ / min,optionally 1℃ / min≤V1≤3℃ / min;0.5h≤t2≤5h,optionally 1.5h≤t2≤3h;5h≤t1≤24h,optionally 6h≤t1≤12h;1h≤t3≤5h,optionally 2h≤t3≤4h. Thus, pre-sintering can make the lithium source α La3Zr 2-xThe co-precipitation precursor diffuses uniformly, which can reduce the temperature of the first sintering and carry out the first sintering in a temperature range lower than the volatilization of lithium, so as to complete the formation of crystals. The second sintering can then rearrange the crystals, further improve the crystal structure of the material, and enhance the stability and electrochemical properties of the solid electrolyte material.

[0011] According to some embodiments of the present application, the method satisfies at least one of the following conditions: the total molar concentration of the metal elements in the mixed salt solution is 0.5 mol / L-3 mol / L, optionally 1 mol / L-2.5 mol / L; the La source includes at least one of lanthanum nitrate and lanthanum chloride; the Zr source includes at least one of zirconium sulfate, zirconium nitrate and zirconium oxychloride; the M source includes at least one of a boric acid compound and a nitric acid compound containing M.

[0012] According to some embodiments of the present application, the method satisfies at least one of the following conditions: placing the mixed salt solution, the precipitant solution and the complexing agent solution in a reactor containing a reaction base liquid, the reaction base liquid comprising the precipitant solution, the complexing agent solution and the surfactant; when conducting the co-precipitation reaction, the pH of the mixed salt solution at 25°C is 9.5-11.5, the reaction temperature is 30°C-65°C, the stirring speed is 300rpm-800rpm, and the total time for adding the mixed salt solution, the precipitant solution and the complexing agent solution to the reactor is 5h-60h; the molar concentration of the precipitant solution is 5mol / L-10mol / L; the precipitant comprises at least one of NaOH, KOH, and LiOH; the mass concentration of the complexing agent solution is 1g / L-20g / L; the complexing agent comprises at least one of ammonia water, ethylenediaminetetraacetic acid, ammonium bicarbonate, ammonium carbonate and citric acid.

[0013] According to some embodiments of the present application, the method further comprises: α La3Zr 2-x Co-precipitation precursor, dispersant mixing; Optionally, based on the lithium source, the M' source, the M α La3Zr 2-x The mass of the dispersant accounts for 0.01%-5% of the total mass of the co-precipitated precursor; optionally, the weight-average molecular weight of the dispersant is 400g / mol-5000g / mol; optionally, the dispersant includes at least one of polyacrylate and polyethylene glycol; optionally, the lithium source includes at least one of lithium carbonate, lithium hydroxide, and lithium nitrate; optionally, the M' source includes at least one of an oxide containing M', a hydroxide containing M', and a carbonate containing M'.

[0014] The third aspect of the present application provides a positive electrode active material, including a substrate, at least part of the surface of the substrate has a coating layer, and the coating layer includes the solid electrolyte material provided in the first aspect of the present application or the solid electrolyte material prepared by the method provided in the second aspect of the present application.

[0015] According to some embodiments of the present application, the mass proportion of the solid electrolyte material is 0.01%-10%, and optionally 0.1%-5%, based on the total mass of the matrix, thereby increasing the gram capacity of the positive electrode active material and improving the energy density and cycle capacity retention rate of the battery.

[0016] The fourth aspect of the present application provides a positive electrode plate, comprising the positive electrode active material provided in the third aspect of the present application.

[0017] The fifth aspect of the present application provides a solid-state battery, comprising the positive electrode plate provided in the fourth aspect of the present application.

[0018] The sixth aspect of the present application provides an electrical device, including the solid-state battery provided in the fifth aspect of the present application. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] The above and / or additional aspects and advantages of the present invention will become apparent and readily understood from the description of the embodiments with reference to the following drawings, in which:

[0020] Figure 1 A schematic diagram of the energy spectrometer analysis position during the standard deviation test of element concentration in the solid electrolyte material of this application is shown.

[0021] Figure 2 A schematic diagram of a process for preparing a solid electrolyte material according to an embodiment of the present application is shown.

[0022] Figure 3 An optical photograph of the precursor powder obtained in Preparation Example 1 of the present application is shown.

[0023] Figure 4 The SEM image of the precursor powder obtained in Preparation Example 1 of the present application is shown.

[0024] Figure 5 An optical photograph of the precursor obtained in Preparation Example 3 of the present application after filtration is shown.

[0025] Figure 6 An optical photograph of the precursor obtained in Preparation Example 3 of the present application after drying is shown.

[0026] Figure 7 The SEM image of the precursor powder obtained in Preparation Example 3 of the present application is shown.

[0027] Figure 8The SEM image of the solid electrolyte material prepared in Example 5 and the element content analysis position are shown.

[0028] Figure 9 The SEM image of the solid electrolyte material prepared in Comparative Example 1 is shown.

[0029] Figure 10 The EDS graph of the solid electrolyte material prepared in Comparative Example 1 is shown.

[0030] Figure 11 The XRD patterns of the solid electrolyte materials prepared in Example 5 and Comparative Example 1 are shown.

[0031] Figure 12 The test results of the discharge specific capacity of the positive electrode active material in Example 5 are shown in the coated and uncoated states.

[0032] Figure 13 A test graph showing the heat release of the positive electrode active material in Example 5 in coated and uncoated states.

[0033] Figure 14 The test results of the discharge specific capacity of the positive electrode active material in Example 5 are shown in the coated and uncoated states. DETAILED DESCRIPTION

[0034] The following embodiments of the present invention are described in detail. The embodiments described below are exemplary and are only used to explain the present invention, and are not to be construed as limiting the present invention. Where specific techniques or conditions are not specified in the embodiments, the techniques or conditions described in the literature in this field or the product specifications are used. Where the manufacturer of the reagents or instruments is not specified, all are conventional products that can be obtained commercially.

[0035] The first aspect of the present application provides a solid electrolyte material, wherein the solid electrolyte material comprises Li 7-nα-β M α La3Zr 2-x M' x O 12 Wherein, 0<α<1, 0≤x≤1, β=(n'-4)x, n is the valence of element M, n' is the valence of element M', M includes at least one of B, Ca, Al, Y, Sc, Fe, and Ga, and M' includes at least one of Ti, Mn, Co, Sn, Ge, Hf, Mo, W, Sb, Nb, and Ta; the standard deviation of the element concentration of the solid electrolyte material is N, and satisfies N≤3%. This improves the uniformity of element distribution in the solid electrolyte material, optimizes the crystal structure of the solid electrolyte material, reduces the tortuosity of active metal ion transmission in the solid electrolyte material, and thereby improves the ionic conductivity and structural stability of the solid electrolyte material.

[0036] The following is a detailed description of the principle by which this application can achieve the above beneficial effects:

[0037] The cubic phase solid electrolyte material proposed in this application can improve the uniformity of the distribution of metal elements in the solid electrolyte material by making the standard deviation of the element concentration less than or equal to 3%, inhibit the formation of low-conductivity phases such as tetragonal LLZO and lanthanum zirconate, reduce internal stress in the crystal, optimize the crystal structure, and improve the stability of the crystal structure, thereby reducing the tortuosity of lithium ion transmission in the solid electrolyte material, shortening the transmission path of lithium ions, and increasing the transmission rate of lithium ions, thereby improving the ionic conductivity of the solid electrolyte material. At the same time, when M and / or M' are doped in the solid electrolyte material, M elements replace Li in the crystal structure to generate vacancies, and M' elements replace Zr in the crystal structure to generate vacancies. The increase in vacancy concentration can reduce the migration barrier of lithium ions, thereby reducing the difficulty of lithium ion migration in the solid electrolyte material, increasing the migration rate of lithium ions, and thereby improving the ionic conductivity of the solid electrolyte material. At the same time, LLZO includes both LiO4 tetrahedrons and LiO6 octahedrons. The doping of M and / or M' can also reduce the interaction force between crystals and improve the stability of the solid electrolyte material structure.

[0038] In this application, the test method for the standard deviation of element concentration is: a single particle is randomly selected in a scanning electron microscope (SEM), and is divided into six equal parts along any diameter (refer to Figure 1 ), energy dispersive spectrometer (EDS) analysis was performed at the five equally divided points in the middle. The composition analysis was the concentration shown by the molar ratio when the total amount of metal elements other than lithium was set to 1. The standard deviation of the element concentration at the five test points was calculated. A total of 10 particles were selected, and the average result of the standard deviation of the element concentration was finally calculated. The SEM test requires the magnification to be the same as the powder particle d 50 The sizes of the electrolyte materials are matched with each other, and the target particles are found by observing the overall morphology at a magnification of 5k according to the particle size, and then further analyzed at a magnification of 10k, 30k or 50k. The SEM images can represent the overall level of the electrolyte material.

[0039] As an example, N may be 3%, 2.5%, 2%, 1.5%, 1%, 0.5%, etc., or may be a range consisting of any of the above values. According to some specific embodiments of the present application, N≤2%.

[0040] It should be noted that the element concentration standard deviation N≤3% referred to in this application means that the concentration standard deviation of each metal element in the solid electrolyte material is less than or equal to 3%.

[0041] According to some embodiments of the present application, M may include at least one of B, Ca, Al, Sc, Fe, and Ga.

[0042] According to some embodiments of the present application, the minimum cross-sectional area of ​​the lithium ion transmission channel of the solid electrolyte material is S, and satisfies For example, it can be or etc., or can be a range consisting of any of the above values. Thus, by making S within the above range, the rate of lithium ion transmission in the solid electrolyte material can be increased, thereby improving the ionic conductivity of the solid electrolyte material. According to some specific embodiments of the present application,

[0043] In this application, S is measured using a Rigaku X-ray diffractometer with Kα radiation from a copper target as the excitation radiation. The scanning range during the test is 10-80°, the scanning step size is 0.02°, and the scanning rate is 1° / min. Using the Riteveld method, the XRD data are refined using GSAS software, including zero point, background, unit cell parameters, peak shape parameters, asymmetry parameters, and structural parameters, to obtain unit cell parameters, bond lengths, bond angles, and other parameters. Finally, the minimum cross-sectional area S is calculated based on the Li1-O bond length.

[0044] According to some embodiments of the present application, the median particle size D of the solid electrolyte material is 50 Satisfy: 0.5μm≤D 50 ≤10μm, for example, it can be 0.5μm, 1μm, 3μm, 5μm, 7μm, 9μm or 10μm, or it can be a range consisting of any of the above values. According to some specific embodiments of the present application, 1μm≤D 50 ≤2.5μm.

[0045] In the present application, the particle size of the solid electrolyte material is measured using a Malvern laser particle size analyzer Mastersizer 2000.

[0046] According to some embodiments of the present application, the specific surface area A of the solid electrolyte material satisfies: 0.2 m 2 / g≤A≤2m 2 / g, for example, it can be 0.2m 2 / g, 0.5m 2 / g, 0.7m 2 / g、1m 2 / g, 1.5m 2 / g or 2m 2 / g, etc., or can be a range composed of any of the above values. According to some specific embodiments of the present application, 0.5m 2 / g≤A≤0.9m 2 / g.

[0047] According to some embodiments of the present application, the solid electrolyte material may include: Li 6.4 La3Zr2Al 0.2 O 12 、Li 6.2 La3Zr 1.8 Al 0.2 Nb 0.2 O 12 、Li6La3Zr2Al 0.2 Ca 0.2 O 12 、Li6La3Zr 1.8 Y 0.2 W 0.2 O 12 、Li 6.4 La3Zr 1.8 Al 0.2 Ti 0.2 O 12 At least one of .

[0048] The second aspect of the present application provides a method for preparing the solid electrolyte provided in the first aspect of the present application, the method comprising: mixing a La source solution, a Zr source solution, and an M source solution to form a mixed salt solution; placing the mixed salt solution, a precipitant solution, a complexing agent solution, and a surfactant in a reactor for coprecipitation reaction, and drying to obtain M α La3Zr 2-x Co-precipitation precursor, based on the total mass of the La source, the Zr source, and the M source, the mass proportion of the surfactant is 0.1%-5%; the lithium source, the M' source and the M α La3Zr 2-x The co-precipitated precursors are mixed to obtain a mixture; the mixture is sintered for the first time and crushed to obtain the solid electrolyte material, wherein the temperature of the first sintering is T1, and satisfies 750°C ≤ T1 ≤ 1000°C, and can be optionally 780°C ≤ T1 ≤ 950°C. Thus, the solid electrolyte material prepared by this method has all the characteristics and advantages of the aforementioned solid electrolyte material, which will not be repeated here. In general, it has at least the advantages of low sintering temperature during the preparation process, uniform distribution of elements in the solid electrolyte material, and high ionic conductivity.

[0049] The following is a detailed description of each step of the method, refer to Figure 2 , the method comprising:

[0050] S10: Mixing La source solution, Zr source solution, and M source solution to form a mixed salt solution

[0051] According to some embodiments of the present application, the La source includes at least one of lanthanum nitrate and lanthanum chloride.

[0052] According to some embodiments of the present application, the Zr source includes at least one of zirconium sulfate, zirconium nitrate, and zirconium oxychloride.

[0053] According to some embodiments of the present application, the M source includes at least one of a boric acid compound and a nitric acid compound containing M.

[0054] Therefore, the above-mentioned types of La sources, Zr sources and M sources are blended in the form of a solution, which can further improve the uniformity of the mixing of the La element, the Zr element and the M element.

[0055] It should be noted that when the solid electrolyte material does not contain M, no M source is added during the preparation process.

[0056] According to some embodiments of the present application, the total molar concentration of the metal elements in the mixed salt solution is 0.5 mol / L-3 mol / L, for example, 0.5 mol / L, 1 mol / L, 1.5 mol / L, 2 mol / L, 2.5 mol / L, or 3 mol / L, or a range consisting of any of the above values. According to some specific embodiments of the present application, the total molar concentration of the metal elements in the mixed salt solution is 1 mol / L-2.5 mol / L.

[0057] S20: placing the mixed salt solution, precipitant solution, complexing agent solution, and surfactant in a reactor for coprecipitation reaction, and drying to obtain M α La3Zr 2-x Co-precipitation precursor

[0058] According to some embodiments of the present application, the mixed salt solution, precipitant solution, complexing agent solution, and surfactant are placed in a reactor for coprecipitation reaction, and after the reaction is completed, the mixture is aged, washed, and dried to obtain M α La3Zr 2-x Thus, by adding surfactants during the coprecipitation process, the wettability and emulsification ability of the metal elements can be improved, which is beneficial to improve the uniformity of the mixing of the metal elements in the reactor, thereby obtaining atomically uniformly mixed, loose and porous M α La3Zr 2-x Co-precipitation precursor, M α La3Zr 2-x When the coprecipitation precursor is mixed with the lithium source, the lithium ions can be α La3Zr 2-x The co-precipitated precursor diffuses uniformly, thereby reducing the temperature during the second sintering, so that the second sintering can be carried out at a temperature lower than the volatilization temperature of lithium, reducing the hardness of the final solid electrolyte material and reducing the difficulty of nano-sizing the solid electrolyte material.

[0059] According to some embodiments of the present application, based on the total mass of the La source, the Zr source, and the M source, the mass proportion of the surfactant is 0.1%-5%, for example, it can be 0.1%, 0.2%, 0.5%, 0.7%, 1%, 2%, 3%, 4% or 5%, etc., or it can be a range composed of any of the above numerical values. Thus, by making the content of the surfactant within the above range, the effect of excessive surfactant content on the interaction between ions is reduced, the risk of surfactant forming micelles is reduced, and the uniformity of metal element mixing is further improved. According to some specific embodiments of the present application, the mass proportion of the surfactant can be 0.2%-2%.

[0060] According to some embodiments of the present application, the surfactant may include at least one of methanol, ethanol, n-propanol, isopropanol, ethylene glycol, propylene glycol, glycerol, acetone, N,N-dimethylformamide, dimethyl sulfoxide, and polyethylene glycol.

[0061] According to some embodiments of the present application, when the co-precipitation reaction is carried out, the pH of the mixed salt solution at 25°C is 9.5-11.5, the reaction temperature is 30°C-65°C, the stirring speed is 300rpm-800rpm, and the total time for adding the mixed salt solution, the precipitant solution and the complexing agent solution into the reactor is 5h-60h.

[0062] As an example, the pH of the mixed salt solution at 25° C. may be 9.5, 10, 10.5, 11 or 11.5, or may be within a range consisting of any of the above values.

[0063] As an example, the temperature of the coprecipitation reaction can be 30°C, 40°C, 50°C, 60°C or 65°C, etc., or can be a range consisting of any of the above values.

[0064] As an example, the stirring speed of the coprecipitation reaction can be 300 rpm, 400 rpm, 500 rpm, 600 rpm, 700 rpm or 800 rpm, or can be a range consisting of any of the above values.

[0065] As an example, the total time for adding the mixed salt solution, the precipitant solution and the complexing agent solution into the reactor can be 5 h, 10 h, 20 h, 30 h, 40 h, 50 h or 60 h, etc., or can be a range consisting of any of the above values.

[0066] According to some embodiments of the present application, the molar concentration of the precipitant solution can be 5 mol / L-10 mol / L, for example, it can be 5 mol / L, 6 mol / L, 7 mol / L, 8 mol / L, 9 mol / L or 10 mol / L, etc., or it can be a range consisting of any of the above values.

[0067] According to some embodiments of the present application, the precipitant may include at least one of NaOH, KOH, and LiOH.

[0068] It should be noted that the amount of precipitant added can be adjusted according to the pH of the mixed salt solution.

[0069] According to some embodiments of the present application, the mass concentration of the complexing agent solution is 1g / L-20g / L, for example, it can be 1g / L, 4g / L, 8g / L, 12g / L, 16g / L or 20g / L, etc., or it can be a range consisting of any of the above values.

[0070] According to some embodiments of the present application, the complexing agent may include at least one of ammonia water, ethylenediaminetetraacetic acid, ammonium bicarbonate, ammonium carbonate and citric acid.

[0071] According to some embodiments of the present application, the method may further include placing the mixed salt solution, the precipitant solution, and the complexing agent solution in a reactor containing a reaction base solution, wherein the reaction base solution includes the precipitant solution, the complexing agent solution, and the surfactant. Thus, by adding the precipitant and complexing agent to the reactor in advance, the coprecipitation rate is increased.

[0072] According to some embodiments of the present application, there is no special limitation on the amount of the reaction base liquid, and it can be adjusted according to the volume of the reactor.

[0073] According to some embodiments of the present application, the volume of the reaction base liquid is V 反应底液 , the volume of the reactor is V 反应器 , and satisfy: V 反应底液 / V 反应器 =0.15-0.25.

[0074] According to some embodiments of the present application, the aging time may be 0.5h-4h, for example, 0.5h, 1h, 2h, 3h or 4h, etc., or may be a range consisting of any of the above values.

[0075] According to some embodiments of the present application, the washing may include: rinsing with pure water and then slurry washing with pure water.

[0076] Specifically, the temperature of the pure water during elution can be 50°C-80°C, for example, 50°C, 60°C, 70°C or 80°C, or any range thereof.

[0077] Specifically, the temperature of pure water during pulp washing may be 50°C-80°C, for example, 50°C, 60°C, 70°C or 80°C, or any range thereof.

[0078] Specifically, the rotation speed during pulping can be 300 rpm-700 rpm, for example, 300 rpm, 400 rpm, 500 rpm, 600 rpm or 700 rpm, or can be within a range consisting of any of the above values.

[0079] Specifically, the pulping time may be 0.3 h to 2 h, for example, 0.3 h, 1 h, 1.5 h or 2 h, or any range thereof.

[0080] S30: Lithium source, M' source and the M α La3Zr 2-x Co-precipitation precursors are mixed to obtain a mixture

[0081] According to some embodiments of the present application, a lithium source, an M' source and the M α La3Zr 2-x The co-precipitated precursors are mixed, ground and spray-dried to obtain a mixture.

[0082] It should be noted that when the solid electrolyte material does not contain M', no M' source is added during the preparation process.

[0083] According to some embodiments of the present application, the lithium source includes at least one of lithium carbonate, lithium hydroxide, and lithium nitrate.

[0084] According to some embodiments of the present application, the M′ source includes at least one of an oxide containing M′, a hydroxide containing M′, and a carbonate containing M′.

[0085] According to some embodiments of the present application, the method may further include: α La3Zr 2-x The coprecipitation precursor and dispersant are mixed, ground and spray-dried to obtain a mixture. Thus, by adding a dispersant, the lithium source, M' source, M α La3Zr 2-x Dispersion effect of coprecipitation precursor in solvent.

[0086] According to some embodiments of the present application, based on the lithium source, the M' source, the M αLa3Zr 2-x The mass proportion of the dispersant to the total mass of the coprecipitated precursor can be 0.01%-5%, for example, 0.01%, 0.1%, 1%, 2%, 3%, 4% or 5%, or a range consisting of any of the above values.

[0087] According to some embodiments of the present application, the weight-average molecular weight of the dispersant may be 400 g / mol-5000 g / mol, for example, 400 g / mol, 1000 g / mol, 2000 g / mol, 3000 g / mol, 4000 g / mol or 5000 g / mol, or may be a range consisting of any of the above values.

[0088] According to some embodiments of the present application, the dispersant includes at least one of polyacrylate and polyethylene glycol.

[0089] According to some embodiments of the present application, the ratio of the actual usage amount of the lithium source to the stoichiometric amount may be 1-1.1 to compensate for lithium volatilization during the sintering process.

[0090] According to some embodiments of the present application, the lithium source, the M' source, the M α La3Zr 2-x After the coprecipitation precursor slurry is ground, the particle size D 50 ≤0.5 μm, for example, it can be 0.5 μm, 0.4 μm, 0.3 μm, 0.2 μm or 0.1 μm, or it can be any range of the above values. According to some specific embodiments of the present application, the slurry D after grinding 50 ≤0.2μm, D 90 ≤0.5μm.

[0091] According to some embodiments of the present application, the inlet air temperature of the spray drying may be 180°C-230°C, and the outlet air temperature may be 90°C-110°C.

[0092] As an example, the inlet air temperature for spray drying may be 180° C., 190° C., 200° C., 210° C., 220° C., or 230° C., or may be within a range consisting of any of the above values.

[0093] As an example, the outlet air temperature of the spray drying may be 90° C., 95° C., 100° C., 105° C. or 110° C., or may be within a range consisting of any of the above values.

[0094] S40: sintering the mixture for the first time and crushing it to obtain the solid electrolyte material

[0095] According to some embodiments of the present application, the mixture is subjected to a first sintering in a dry atmosphere, and then subjected to grinding, crushing, screening, and iron removal treatment to obtain the solid electrolyte material.

[0096] According to some embodiments of the present application, the dry atmosphere may be dry air or dry oxygen.

[0097] According to some embodiments of the present application, the temperature of the first sintering is T1, the holding time of the first sintering is t1, the heating rate of the first sintering is V1, and 750°C≤T1≤1000°C.

[0098] As an example, T1 may be 750°C, 800°C, 850°C, 900°C, 950°C or 1000°C, or may be a range consisting of any of the above values. According to some specific embodiments of the present application, 780°C≤T1≤950°C.

[0099] According to some embodiments of the present application, the method may further include: performing pre-sintering before the first sintering, and performing a second sintering after the first sintering, the temperature of the pre-sintering is T2, the temperature of the second sintering is T3, the holding time of the first sintering is t1, the heating rate of the first sintering is v1, the holding time of the pre-sintering is t2, the heating rate of the pre-sintering is v2, and the holding time of the second sintering is t3.

[0100] According to some embodiments of the present application, 300°C≤T2≤700°C, 0.5h≤t2≤5h, 0.5°C / min≤V2≤10°C / min. α La3Zr 2-x The coprecipitated precursor has a porous structure. By making T2, t2, and V2 within the above ranges, the lithium source can be α La3Zr 2-x The co-precipitation precursor is uniformly diffused, reducing the standard deviation of the element concentration of the solid electrolyte material. Through pre-sintering, the temperature of the first sintering can be reduced so that the first sintering is carried out within a temperature range lower than the volatilization of lithium, which is beneficial to the nano-sizing of the solid electrolyte material.

[0101] As an example, T2 may be 300° C., 400° C., 500° C., 600° C., or 700° C., or may be within a range of any of the above values. According to some specific embodiments of the present application, 450° C.≤T2≤650° C.

[0102] As an example, V2 can be 0.5°C / min, 1°C / min, 2°C / min, 3°C / min, 4°C / min, 5°C / min, 6°C / min, 7°C / min, 8°C / min, 9°C / min, or 10°C / min, or can be a range consisting of any of the above values. According to some specific embodiments of the present application, 1°C / min ≤ V2 ≤ 5°C / min.

[0103] As an example, t2 can be 0.5h, 1h, 2h, 3h, 4h or 5h, or can be a range consisting of any of the above values. According to some specific embodiments of the present application, 1.5h≤t2≤3h.

[0104] According to some embodiments of the present application, the holding time of the first sintering is t1, the heating rate of the first sintering is V1, 0.5°C / min≤V1≤10°C / min, 5h≤t1≤24h. Thus, the first sintering increases the crystal growth rate.

[0105] As an example, V1 can be 0.5°C / min, 1°C / min, 2°C / min, 3°C / min, 4°C / min, 5°C / min, 6°C / min, 7°C / min, 8°C / min, 9°C / min, or 10°C / min, or can be a range consisting of any of the above values. According to some specific embodiments of the present application, 1°C / min ≤ V1 ≤ 3°C / min.

[0106] As an example, t1 can be 5 hours, 8 hours, 11 hours, 14 hours, 17 hours, 20 hours, 22 hours or 24 hours, or can be a range consisting of the above arbitrary values. According to some specific embodiments of the present application, 6 hours ≤ t1 ≤ 12 hours.

[0107] Therefore, by keeping the first sintering temperature, holding time, and heating rate within the above ranges, the crystal growth rate can be increased, the minimum cross-sectional area S of the lithium ion transmission channel in LLZO can be increased, the lithium ion transmission rate can be increased, and the ionic conductivity of LLZO can be improved. At the same time, by keeping the first sintering temperature and holding time within the above ranges, LLZO with only a cubic phase can be formed, further improving the ionic conductivity of LLZO.

[0108] According to some embodiments of the present application, the temperature of the second sintering is T3, the holding time of the second sintering is t3, 600°C≤T3≤750°C, 1h≤t3≤5h.

[0109] As an example, T3 may be 600°C, 620°C, 640°C, 660°C, 680°C, 700°C, 720°C, 740°C, or 750°C, or may be any range thereof. According to some specific embodiments of the present application, 650°C≤T3≤730°C may be selected.

[0110] As an example, t3 can be 1 hour, 2 hours, 3 hours, 4 hours or 5 hours, or can be a range consisting of any of the above values. According to some specific embodiments of the present application, 2 hours ≤ t3 ≤ 4 hours.

[0111] Therefore, by setting the temperature and holding time of the second sintering within the above-mentioned range, the crystals are rearranged, the stress between the crystals is eliminated, and the structural stability of the solid electrolyte material is improved. At the same time, through the second sintering, the uniformity of the element distribution in the solid electrolyte material is further improved, and the ionic conductivity of the solid electrolyte material is improved.

[0112] According to some embodiments of the present application, the specific processes for grinding, crushing, screening, and iron removal are not particularly limited, as long as they meet the requirements. In the present application, the grinding can be performed using a stirred ball mill, a planetary ball mill, or a sand mill; the crushing can be performed using a roller crusher, a ball mill, a jet mill, or a mechanical mill; the screening can be performed using an ultrasonic vibrating screen; and the iron removal can be performed using an electromagnetic iron remover.

[0113] In a third aspect, the present application provides a positive electrode active material comprising a substrate, wherein at least a portion of the substrate surface has a coating layer, wherein the coating layer comprises the aforementioned solid electrolyte material. Thus, by forming the solid electrolyte material on at least a portion of the substrate surface, the ionic conductivity of the positive electrode active material can be improved due to the high ionic conductivity of the solid electrolyte material, thereby improving the rate performance of the battery.

[0114] According to some embodiments of the present application, based on the total mass of the matrix, the mass proportion of the solid electrolyte material can be 0.01%-10%, for example, it can be 0.01%, 0.1%, 1%, 3%, 5%, 7%, 9% or 10%, etc., or it can be a range composed of any of the above numerical values. Thus, by making the content of the solid electrolyte material within the above range, the ionic conductivity of the positive electrode active material can be improved, thereby improving the rate performance of the battery. According to some specific embodiments of the present application, the mass proportion of the solid electrolyte material can be 0.1%-5%.

[0115] According to some embodiments of the present application, the method for preparing the positive electrode active material may include mixing a solid electrolyte material with a matrix of the positive electrode active material, and performing sintering, crushing, and screening to obtain the positive electrode active material.

[0116] According to some embodiments of the present application, the sintering temperature may be 270°C-820°C, for example, 270°C-300°C, 400°C, 500°C, 600°C, 700°C, 800°C, or 820°C, or a range thereof. According to some specific embodiments of the present application, the sintering temperature may be 350°C-750°C.

[0117] According to some embodiments of the present application, the sintering time may be 4 hours to 48 hours, for example, 4 hours, 10 hours, 20 hours, 30 hours, 40 hours, or 48 hours, or may be within a range of any of the above values. According to some specific embodiments of the present application, the sintering time may be 8 hours to 24 hours.

[0118] According to some embodiments of the present application, the matrix of the positive electrode active material may be a lithium nickel cobalt manganese oxide multi-element material.

[0119] The fourth aspect of the present application provides a positive electrode plate, comprising the positive electrode active material provided in the third aspect of the present application.

[0120] The fifth aspect of the present application provides a solid-state battery, comprising the positive electrode sheet provided in the third aspect of the present application.

[0121] The sixth aspect of the present application provides an electrical device, including the solid-state battery provided in the fifth aspect of the present application.

[0122] The following embodiments of the present invention are described in detail. The embodiments described below are exemplary and are only used to explain the present invention, and are not to be construed as limiting the present invention. Where specific techniques or conditions are not specified in the embodiments, the techniques or conditions described in the literature in this field or the product specifications are used. Where the manufacturer of the reagents or instruments is not specified, all are conventional products that can be obtained commercially.

[0123] Preparation Example 1

[0124] (1) Lanthanum chloride, zirconium oxychloride and aluminum chloride are prepared in a molar ratio of La:Zr:Al=3:2:0.2 to prepare a mixed salt solution, wherein the concentration of the metal elements in the mixed salt solution is 2 mol / L, the amount of surfactant ethanol added is 1%, a sodium hydroxide solution with a concentration of 5 mol / L is prepared as a precipitant solution, and an ammonia solution with a concentration of 10 mol / L is prepared as a complexing agent solution.

[0125] (2) Add the reaction base liquid to the reactor, the reaction base liquid includes sodium hydroxide solution, ammonia water and surfactant ethanol, the content of ammonia water in the reaction base liquid is 3g / L, the pH of the reaction base liquid is 10.1, the temperature of the reactor is raised to 50℃, the stirring speed is 700rpm, and the mixed salt solution, sodium hydroxide solution, ammonia water and surfactant ethanol are added to the reactor to control the pH value of the reaction system to be 10.1, the complexing agent content is 3g / L, the reaction temperature is 50℃, the stirring speed is 700rpm, and the total liquid addition time is 10h to obtain a slurry. The slurry is aged for 2h and rinsed with 70℃ pure water. The filter cake is then slurried with 70℃ pure water. The stirring speed during slurry washing is 500rpm. After slurry washing for 1h, the filter cake is filtered to obtain a filter cake, which is dried at 120℃ for 24h to obtain a powdered garnet-type solid electrolyte precursor material La3Zr2Al 0.2 (OH) 17.6 The median particle size d of the precursor material 50 The surface area is 5.7 μm and the specific surface area is 127 m 2 / g.

[0126] Preparation Example 2

[0127] The preparation process of the precursor material is the same as that of Preparation Example 1, except that lanthanum chloride, zirconium oxychloride, aluminum chloride and niobium chloride are prepared according to the molar ratio of La:Zr:Al:Nb=3:1.8:0.2:0.2. The median particle size d 50 The surface area is 5.7 μm and the specific surface area is 156 m 2 / g.

[0128] Preparation Example 3

[0129] The preparation process of the precursor material is the same as that of Preparation Example 1, except that no ethanol is added.

[0130] Preparation Example 4

[0131] The preparation process of the precursor material is the same as that of Preparation Example 1, except that the amount of ethanol added is 0.02%.

[0132] Preparation Example 5

[0133] The preparation process of the precursor material is the same as that of Preparation Example 1, except that the amount of ethanol added is 0.1%.

[0134] Preparation Example 6

[0135] The preparation process of the precursor material is the same as that of Preparation Example 1, except that the amount of ethanol added is 0.2%.

[0136] Preparation Example 7

[0137] The preparation process of the precursor material is the same as that of Preparation Example 1, except that the amount of ethanol added is 2%.

[0138] Preparation Example 8

[0139] The preparation process of the precursor material is the same as that of Preparation Example 1, except that the amount of ethanol added is 5%.

[0140] Preparation Example 9

[0141] The preparation process of the precursor material is the same as that of Preparation Example 1, except that the amount of ethanol added is 6%.

[0142] Preparation Example 10

[0143] The preparation process of the precursor material is the same as that of Preparation Example 1, except that the amount of isopropyl alcohol added is 1%.

[0144]

[0145] in conclusion:

[0146] As can be seen from Table 1, the present invention is α La3Zr 2-x When the precursor is coprecipitated, the M can be made α La3Zr 2-x The standard deviation N of the element concentration of the co-precipitated precursor is ≤3%.

[0147] It can be seen from Preparation Examples 3 and 4 that when no surfactant is used or the surfactant content is too low, the standard deviation of the element concentration in the coprecipitation precursor is large and the element distribution is uneven.

[0148] It can be seen from Preparation Example 9 that when the surfactant content is too much, the standard deviation of the element concentration in the co-precipitation precursor is large and the element distribution is uneven, which means that adding too much surfactant will cause the metal ions to agglomerate, which will reduce the dispersion stability of the solution system and cause uneven distribution of elements in the co-precipitation precursor.

[0149] Example 1

[0150] (1) Li2CO3 and the precursor material La3Zr2Al in Preparation Example 1 0.2 (OH) 17.6 The above substances were weighed according to the molar ratio of n(Li):n(La)=6.60:3, wherein Li was in excess of 3%; the above substances, PEG1500 dispersant and water were mixed and ground, and the particle size of the slurry was D 50 =0.2μm, D 100 =0.8 μm, wherein the mass ratio of the mixture to the dispersant is 100:0.2; the slurry is spray-dried (the inlet air temperature is 200° C. and the outlet air temperature is 97° C.) to obtain a mixture;

[0151] (2) The dry powder of the mixture is placed in a roller kiln, and the temperature is raised to 520°C at a rate of 5°C / min in a dry air atmosphere, and kept at this temperature for 1 hour. Then the temperature is raised to 750°C at a rate of 1.5°C / min, and kept at this temperature for 10 hours. Then the temperature is lowered to 700°C and kept at this temperature for 2 hours, and finally cooled naturally. After crushing and screening to remove iron, Li 6.4 La3Zr2Al 0.2 O 12 .

[0152] (3) Lithium nickel cobalt manganate multi-material matrix Li 1.05 Ni 0.93 Co 0.02 Mn 0.05 O2 and nano-lithium 6.4 La3Zr2Al 0.2 O 12 Mixed evenly, the nano-Li 6.4 La3Zr2Al 0.2 O 12 D 50 =160nm, specific surface area is 23.7m 2 / g, nickel cobalt manganese oxide multi-material matrix and Li 6.4 La3Zr2Al 0.2 O 12 The mass ratio is 100:0.5. The mixture is then sintered at 550°C for 10 hours, crushed and sieved to obtain a multi-element positive electrode material of lithium nickel cobalt manganese oxide coated with a cubic phase LLZO solid electrolyte material.

[0153] The preparation processes of the positive electrode active materials of Examples 2 to 21 and Comparative Examples 2 to 5 are the same as those of Example 1, with the differences shown in Table 2 for details.

[0154] Comparative Example 1

[0155] (1) Li2CO3, La2O3 and ZrO2 were weighed in a molar ratio of n(Li):n(La):n(Zr)=7.28:3:2 and mixed uniformly by dry method;

[0156] (2) The mixture was placed in a roller kiln and heated to 520°C at a rate of 5°C / min in a dry air atmosphere, then heated to 825°C at a rate of 1.5°C / min, kept at this temperature for 10 hours, and naturally cooled to about 100°C; after crushing and screening to remove iron, Li7La3Zr2O was obtained. 12 .

[0157] Table 2

[0158]

[0159]

[0160] Performance test 1. The median particle size test was obtained by using Malvern laser particle size analyzer Mastersizer 2000.

[0161] 2. Specific surface area test method

[0162] The surface area was measured using a Tri-star 3020 surface area analyzer from Micromeritics, USA. The specific test conditions were: sample weight: 5.0 g; equipment degassing time / temperature: 100°C / 120 min (ventilation purge); adsorbate: N2, 99.99%; liquid nitrogen temperature: -196°C; multi-point BET method: P / P0 0.060, 0.080, 0.120, 0.160, 0.200.

[0163] 3. Crystal structure test

[0164] The results were obtained by using Rigaku X-ray automatic diffractometer.

[0165] 4. Element concentration standard deviation test method

[0166] In this application, the test method for the standard deviation of element concentration is as follows: a single particle is randomly selected in a scanning electron microscope (SEM) and divided into six equal parts along any diameter (refer to Figure 1 ), energy dispersive spectrometer (EDS) analysis was performed at the five equally divided points in the middle. The composition analysis was the concentration shown by the molar ratio when the total amount of metal elements other than lithium was set to 1. The standard deviation of the element concentration at the five test points was calculated. A total of 10 particles were selected, and the average result of the standard deviation of the element concentration was finally calculated. The SEM test requires the magnification to be the same as the powder particle d 50 The sizes of the electrolyte materials are matched with each other, and the target particles are found by observing the overall morphology at a magnification of 5k according to the particle size, and then further analyzed at a magnification of 10k, 30k or 50k. The SEM images can represent the overall level of the electrolyte material.

[0167] 5. Minimum cross-sectional area test of lithium ion transmission channel

[0168] A Rigaku X-ray diffractometer was used, with Kα radiation from a copper target as the excitation radiation. The scanning range was 10–80°, with a scan step of 0.02° and a scan rate of 1° / min. The Riteveld method was used to refine the XRD data using GSAS software, including zero point, background, cell parameters, peak shape parameters, asymmetry parameters, and structural parameters, to obtain cell parameters, bond lengths, and bond angles. Finally, the minimum cross-sectional area, S, was calculated based on the Li⁻O bond length.

[0169] 6. Ionic conductivity test method

[0170] Take 1g of solid electrolyte material, place it in a mold with a diameter of 11mm, and press it at 280MPa to obtain a ceramic sheet. Evenly cover 10g of solid electrolyte material on the ceramic sheet, sinter it at 1150℃ for 4h, take out the ceramic sheet and polish it to obtain a solid electrolyte ceramic sheet. After spraying gold on both sides of the above ceramic sheet, assemble the stainless steel sheet | ceramic sheet | stainless steel sheet test system, and test the AC impedance at room temperature in the Bio-logic SP-150 electrochemical workstation (the test frequency is set to 1MHz~1Hz, and the perturbation voltage is 10mV). The corresponding ionic conductivity is calculated by the formula σ=L / RS, where σ is the ionic conductivity (S / cm); R is the AC impedance value (Ω); L is the thickness of the ceramic sheet (cm); S is the area of ​​the ceramic sheet (cm 2 ).

[0171] 7. Button battery preparation method:

[0172] The positive electrode active material (Li 1.05 Ni 0.93 Co 0.02 Mn 0.05 O2), acetylene black and polyvinylidene fluoride are dispersed in an appropriate amount of NMP in a mass ratio of 95:2.5:2.5, coated on aluminum foil and dried, and then cut into positive electrode sheets with a diameter of 12 mm. The positive electrode sheets are then vacuum-dried at 120°C for 12 hours and then vacuum-sealed for storage.

[0173] The negative electrode uses a lithium metal sheet with a diameter of 16 mm and a thickness of 1 mm.

[0174] The separator was a Celgard porous membrane with a thickness of 25 μm.

[0175] The electrolyte uses LiPF6 as solute and equal volumes of ethylene carbonate, dimethyl carbonate and diethyl carbonate as solvents, and the concentration of LiPF6 is 1 mol / L.

[0176] The positive electrode sheet, separator, negative electrode sheet and electrolyte were assembled into a 2025 button cell in an argon-filled glove box with a water content and an oxygen content of less than 5 ppm.

[0177] 8. Discharge specific capacity test method at 25℃ and 45℃

[0178] The assembled 2025 button-type battery was placed in a constant temperature environment at 25°C for 24 hours. The battery was then charged to 4.3V using a charge-discharge tester at a 0.1C charge current. The battery was then switched to constant voltage charging until the charge current was ≤0.01C. The battery was then discharged to 3V at a 0.1C discharge current for two cycles. The charge-discharge cycle was then repeated at a 1C current. The charge-discharge capacity and cycling performance of the positive electrode material in the liquid lithium-ion battery were evaluated. The tests were conducted at both 25°C and 45°C.

[0179] 9. Heat release test method

[0180] The assembled 2025 button battery was placed in a constant temperature environment at 25°C for 24 hours, then charged to 4.3V at a charging current of 0.1C on a charge and discharge tester, switched to constant voltage charging until the charging current was ≤0.01C, then discharged to 3V at a discharge current of 0.1, and finally charged to 4.3V at a charging current of 0.1C, switched to constant voltage charging until the charging current was ≤0.01C.

[0181] The fully charged 2025 button cell battery was disassembled in an argon-filled glove box with a water and oxygen content of less than 5 ppm to obtain the positive electrode sheet. The positive electrode sheet was then placed in a high-pressure crucible, sealed, and removed from the glove box. Finally, it was tested on a METTLER TGA / DSC 3+ instrument under the conditions of 30°C-350°C, a heating rate of 5°C / min, an N2 atmosphere, and a carrier gas flow rate of 50 mL / min.

[0182] 10. Sulfide solid-state battery discharge capacity test method

[0183] The positive electrode active material, acetylene black, polytetrafluoroethylene and Li 5.5 PS 4.5 Cl 1.5 The solid electrolyte was placed in a mortar and ground for 30 min according to a mass ratio of 80:2:3:15 to achieve uniform mixing. 10 mg of the composite cathode material was weighed and evenly dispersed on the bottom of a 10 mm diameter stainless steel mold. Then 150 mg of Li 5.5 PS 4.5 Cl 1.5Solid electrolyte powder was poured into a mold, and finally a lithium negative electrode sheet with a diameter of 10 mm and a thickness of 1 mm was placed on it. The mold was pressed at a pressure of 600 MPa for 3 minutes to obtain a sandwich-structured all-solid-state lithium-ion battery based on a sulfide solid electrolyte. Finally, the battery was encapsulated in a 2025 battery case. All of the above processes were carried out in an argon-filled glove box with a water and oxygen content of less than 5 ppm. The assembled 2025 sulfide solid-state battery was placed in a constant temperature environment at 25°C for 24 hours. It was then charged to 4.3V on a charge-discharge tester at a charging current of 0.1C, switched to constant voltage charging to a charging current of ≤0.01C, and then discharged to 3V at a discharge current of 0.1C, completing two cycles. The charge and discharge cycles were then repeated at currents of 0.2C and 0.3C. The charge-discharge capacity and rate performance of the positive electrode material in the sulfide solid-state battery were investigated.

[0184] The test results of the positive electrode active materials in Examples 1 to 21 and Comparative Examples 1 to 5 are shown in Table 3.

[0185] Table 3

[0186]

[0187]

[0188]

[0189] in conclusion:

[0190] It can be seen from the comparison of Examples 1 to 21 with Comparative Examples 1 to 5 that the present application can improve the ionic conductivity of the solid electrolyte material by making the standard deviation N of the element concentration in the solid electrolyte material ≤3%.

[0191] It can be seen from the comparison between Examples 1 to 21 and Comparative Examples 2 and 5 that the present application can reduce the standard deviation of the element concentration in the solid electrolyte material by adding 0.1%-5% of a surfactant during the preparation process of the solid electrolyte material. If no surfactant is added during the preparation process or the amount of surfactant added is not within the scope of protection of this application, the standard deviation of the element concentration of the solid electrolyte material will increase and the uniformity of the distribution of metal elements will be reduced.

[0192] It can be seen from the comparison of Examples 1 to 9 with Comparative Examples 3 and 4 that the present application can increase the standard deviation of the element concentration of the solid electrolyte material and improve the ionic conductivity of the solid electrolyte material by setting the temperature of the first sintering in the range of 750°C-1000°C.

[0193] It can be seen from the comparison of Examples 1 to 19 with Examples 20 and 21 that the present application can increase the minimum cross-sectional area S of the solid electrolyte material by performing pre-sintering before the first sintering and performing a second sintering after the first sintering, thereby improving the ionic conductivity of the solid electrolyte material.

[0194] By the attached Figure 3 , Attachment Figure 4 It can be seen that the precursor material obtained in Preparation Example 1 has a loose porous structure.

[0195] By the attached Figure 5 and Figure 6 It can be seen that if the precursor material is prepared without adding surfactant, the water content in the precursor filter cake will be high, and it will be severely compacted after drying and difficult to break. Figure 7 It can be seen from the SEM scanning image in that the precursor material is relatively dense.

[0196] By the attached Figure 8 It can be seen that the elements in the solid electrolyte material in Example 5 are evenly distributed.

[0197] By the attached Figure 9 and attached Figure 10 It can be seen that the attached Figure 9 The SEM scanning image in the SEM position of the solid electrolyte material prepared in Comparative Example 1 has a large number of dark spots, and EDS shows that the Al element aggregates in the solid electrolyte material, indicating that the Al element is unevenly distributed in the solid electrolyte material.

[0198] By the attached Figure 11 It can be seen that the crystal structure in the XRD test pattern of the solid electrolyte material prepared in Example 5 is consistent with the cubic phase standard card PDF#01-090-2617, that is, a cubic phase solid electrolyte material is prepared.

[0199] By the attached Figure 11 It can be seen that the diffraction peaks in the XRD test spectrum of the solid electrolyte material prepared in Comparative Example 1 show a large number of splits, which is a tetragonal phase structure, indicating that the Al element does not enter the interior of the lattice. This result is consistent with the results of the attached Figure 10 The EDS test results were consistent.

[0200] By the attached Figure 12 It can be seen that the uncoated positive electrode active material matrix of Example 5 and the positive electrode active material coated with the solid electrolyte material were respectively prepared into button batteries for discharge specific capacity testing. The positive electrode active material with the solid electrolyte material coated on the surface has higher capacity and cycle capacity retention rate.

[0201] By the attached Figure 13It can be seen that after the surface of the positive electrode active material matrix is ​​coated with the solid electrolyte material in Example 5, the temperature corresponding to the exothermic peak is higher, indicating that coating the solid electrolyte material can make the positive electrode active material more resistant to high temperatures and improve the thermal stability of the positive electrode active material.

[0202] By the attached Figure 14 It can be seen that the positive electrode material coated with the solid electrolyte material has higher capacity and rate performance, indicating that coating the solid electrolyte material can reduce the interface impedance between the positive electrode material and the sulfide solid electrolyte, which is beneficial to the rapid transmission of lithium ions and fully exerts the battery performance.

[0203] Although the embodiments of the present invention have been shown and described above, it will be understood that the above embodiments are illustrative and are not to be construed as limitations on the present invention. A person skilled in the art may change, modify, replace and modify the above embodiments within the scope of the present invention.

Claims

1. A solid electrolyte material, characterized in that The solid electrolyte material has a cubic phase structure and includes: <h2 style=";text-align:left;direction:ltr">Li<h2 style=";text-align:left;direction:ltr"> 7-nα-β <h2 style=";text-align:left;direction:ltr"> M<h2 style=";text-align:left;direction:ltr"> α <h2 style=";text-align:left;direction:ltr"> La3Zr<h2 style=";text-align:left;direction:ltr"> 2-x <h2 style=";text-align:left;direction:ltr"> M'<h2 style=";text-align:left;direction:ltr"> x <h2 style=";text-align:left;direction:ltr"> O<h2 style=";text-align:left;direction:ltr"> 12 <h2 style=";text-align:left;direction:ltr"> ; Wherein, 0<α<1, 0≤x≤1, β=(n'-4)x, n is the valence of element M, n' is the valence of element M', M includes at least one of B, Ca, Al, Y, Sc, and Fe, and M' includes at least one of Ti, Mn, Co, Sn, Ge, Hf, Mo, W, Sb, Nb, and Ta; The median particle size D of the solid electrolyte material 50 Satisfy: 1μm≤D 50 ≤2.5μm; The standard deviation of the element concentration of the solid electrolyte material is N, and satisfies 0.21%≤N≤0.44%. The specific surface area A of the solid electrolyte material satisfies: 0.5m 2 / g≤A≤0.62m 2 / g; wherein, the testing method for the standard deviation of the element concentration is: randomly selecting a single particle in a scanning electron microscope, dividing it into six equal parts along an arbitrary diameter, performing energy spectrometer analysis at the five middle dividing points, and the composition analysis is the concentration shown by the molar ratio when the total amount of metal elements other than lithium is set to 1. The standard deviation of the element concentration of the single particle is obtained by calculating the five test points, and a total of 10 particles are selected to calculate the average result of the element concentration standard deviation, that is, the element concentration standard deviation N of the solid electrolyte material.

2. The solid electrolyte material according to claim 1, characterized in that Including Li 6.4 La3Zr2Al 0.2 O 12 、Li 6.2 La3Zr 1.8 Al 0.2 Nb 0.2 O 12 、Li6La3Zr2Al 0.2 Ca 0.2 O 12 、Li6La3Zr 1.8 Y 0.2 W 0.2 O 12 、Li 6.4 La3Zr 1.8 Al 0.2 Ti 0.2 O 12 At least one of .

3. A method for preparing the solid electrolyte material according to any one of claims 1 to 2, characterized in that: include: mixing a La source solution, a Zr source solution, and a M source solution to form a mixed salt solution; The mixed salt solution, precipitant solution, complexing agent solution and surfactant are placed in a reactor for coprecipitation reaction and dried to obtain M α La3Zr 2-x In the co-precipitation precursor, based on the total mass of the La source, the Zr source, and the M source, the mass proportion of the surfactant is 0.1%-5%; Lithium source, M' source and the M α La3Zr 2-x mixing the co-precipitated precursors to obtain a mixture; The mixed material is sequentially subjected to pre-sintering, first sintering, second sintering, and crushing to obtain the solid electrolyte material, wherein the pre-sintering temperature is T2, the first sintering temperature is T1, the second sintering temperature is T3, and the following conditions are satisfied: 300°C ≤ T2 ≤ 700°C, 780°C ≤ T1 ≤ 950°C, and 600°C ≤ T3 ≤ 750°C.

4. The method according to claim 3, characterized in that Meet at least one of the following conditions: Based on the total mass of the La source, the Zr source, and the M source, the mass proportion of the surfactant is 0.2%-2%; The surfactant includes at least one of methanol, ethanol, n-propanol, isopropanol, ethylene glycol, propylene glycol, glycerol, acetone, N,N-dimethylformamide, dimethyl sulfoxide, and polyethylene glycol.

5. The method according to claim 3, characterized in that The holding time of the first sintering is t1, the heating rate of the first sintering is v1, the holding time of the pre-sintering is t2, the heating rate of the pre-sintering is v2, and the holding time of the second sintering is t3. The method satisfies at least one of the following conditions: 450℃≤T2≤650℃； 650℃≤T3≤730℃； 0.5℃ / min≤V2≤10℃ / min; 0.5℃ / min≤V1≤10℃ / min; 0.5h≤t2≤5h; 5h≤t1≤24h; 1h≤t3≤5h.

6. The method according to claim 5, characterized in that Meet at least one of the following conditions: 1℃ / min≤V2≤5℃ / min; 1℃ / min≤V1≤3℃ / min; 1.5h≤t2≤3h; 6h≤t1≤12h; 2h≤t3≤4h.

7. The method according to claim 3, characterized in that Meet at least one of the following conditions: The total molar concentration of the metal elements in the mixed salt solution is 0.5 mol / L-3 mol / L; The La source includes at least one of lanthanum nitrate and lanthanum chloride; The Zr source includes at least one of zirconium sulfate, zirconium nitrate and zirconium oxychloride; The M source includes at least one of a boric acid compound and a nitric acid compound containing M.

8. The method according to claim 7, characterized in that The total molar concentration of the metal elements in the mixed salt solution is 1 mol / L-2.5 mol / L.

9. The method according to claim 3, characterized in that Meet at least one of the following conditions: placing the mixed salt solution, the precipitant solution and the complexing agent solution in a reactor containing a reaction base liquid, wherein the reaction base liquid includes the precipitant solution, the complexing agent solution and the surfactant; When performing the coprecipitation reaction, the pH of the mixed salt solution at 25° C. is 9.5-11.5, the reaction temperature is 30° C.-65° C., the stirring speed is 300 rpm-800 rpm, and the total time for adding the mixed salt solution, the precipitant solution, and the complexing agent solution into the reactor is 5 h-60 h; The molar concentration of the precipitant solution is 5 mol / L-10 mol / L; The precipitant includes at least one of NaOH, KOH, and LiOH; The mass concentration of the complexing agent solution is 1g / L-20g / L; The complexing agent includes at least one of ammonia water, ethylenediaminetetraacetic acid, ammonium bicarbonate, ammonium carbonate and citric acid.

10. The method according to claim 3, characterized in that The lithium source, the M' source, the M α La3Zr 2-x The co-precipitation precursor and dispersant are mixed.

11. The method according to claim 10, characterized in that Based on the lithium source, the M' source, the M α La3Zr 2-x The mass of the dispersant accounts for 0.01%-5% of the total mass of the co-precipitated precursor.

12. The method according to claim 10, characterized in that The weight average molecular weight of the dispersant is 400 g / mol-5000 g / mol.

13. The method according to claim 10, characterized in that The dispersant includes at least one of polyacrylate and polyethylene glycol.

14. The method according to claim 10, characterized in that The lithium source includes at least one of lithium carbonate, lithium hydroxide, and lithium nitrate.

15. The method according to claim 10, characterized in that The M' source includes at least one of an oxide containing M', a hydroxide containing M', and a carbonate containing M'.

16. A positive electrode active material, characterized in that The invention comprises a substrate, at least part of the surface of the substrate has a coating layer, and the coating layer comprises the solid electrolyte material according to any one of claims 1 to 2 or the solid electrolyte material prepared by the method according to any one of claims 3 to 15.

17. The positive electrode active material according to claim 16, characterized in that Based on the total mass of the matrix, the mass proportion of the solid electrolyte material is 0.01%-10%.

18. The positive electrode active material according to claim 17, characterized in that Based on the total mass of the matrix, the mass proportion of the solid electrolyte material is 0.1%-5%.

19. A positive electrode plate, characterized in that: The positive electrode active material comprises the positive electrode active material according to any one of claims 16 to 18.

20. A solid-state battery, characterized in that: Including the positive electrode sheet according to claim 19.

21. An electrical device, characterized in that: Including the solid-state battery as described in claim 20.

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