Tantalum gradient doped lithium-rich manganese-based precursor and preparation and application thereof

Abstract

The invention provides a tantalum gradient doped lithium-rich manganese-based precursor as well as preparation and application thereof. The lithium-rich manganese-based precursor comprises an inner core and at least one coating layer sequentially coating the outer part of the inner core, the inner core and all the coating layers contain tantalum elements, and the concentration of the tantalum elements is increased in the direction from the inner core of the lithium-rich manganese-based precursor to the outermost coating layer. In the tantalum gradient doped lithium-rich manganese-based precursor provided by the invention, the concentration of the tantalum element is increased along the direction from the inner core of the lithium-rich manganese-based precursor to the outermost coating layer, and the enrichment of the tantalum element on the outermost coating layer is realized, so that not only are the lattice oxygen loss and the structure phase change inhibited, but also the lithium-rich manganese-based precursor is obtained. And the problem of unstable structure caused by too fine primary crystal grains of the outermost coating layer is avoided, so that phase change and voltage attenuation in the battery circulation process are inhibited, and the capacity, the first coulombic efficiency and the circulation stability of the battery prepared from the lithium-rich manganese-based precursor are improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of electrodeposition, and relates to a tantalum gradient-doped lithium-rich manganese-based precursor, and in particular to a tantalum gradient-doped lithium-rich manganese-based precursor, and its preparation and application. Background Art

[0002] Lithium-rich manganese-based materials have long been ideal cathode materials for high-energy-density, long-life batteries due to their high specific capacity, abundant manganese resources, and low cost. With the rapid development of the new energy vehicle industry, solid-state battery technology has become a research focus. Lithium-rich manganese-based materials excel in improving battery energy density and are expected to become one of the mainstream cathode materials in solid-state battery technology.

[0003] However, if lithium-rich manganese-based materials are directly used in batteries, the first coulombic efficiency of batteries prepared with lithium-rich manganese-based materials will be low and the cycle stability will be insufficient due to the side reactions that easily occur on the surface of the lithium-rich manganese-based materials to form an unstable SEI film, the lattice structure is easily repeatedly distorted during charging and discharging, the interface impedance is high and the ion conductivity performance is insufficient.

[0004] In the prior art, the performance of lithium-rich manganese-based materials is improved by performing interface coating on the lithium-rich manganese-based materials. The coulombic efficiency and cycle life of batteries prepared with the coated lithium-rich manganese-based materials are improved. However, the capacity, coulombic efficiency and cycle life of the batteries still cannot meet the requirements of practical applications.

[0005] CN119920882A proposes a modified lithium-rich manganese-based cathode material and its preparation method, in which a solid electrolyte layer and an n-type polymer polybenzofurandione layer are sequentially coated on the surface of the lithium-rich manganese-based material. However, batteries prepared using this modified lithium-rich manganese-based cathode material still suffer from problems with capacity and cycle stability that fail to meet the requirements of practical applications.

[0006] CN118867179A discloses a fast-charging lithium-rich manganese-based positive electrode material, its preparation method, and application. The fast-charging lithium-rich manganese-based positive electrode material includes single-crystalline lithium-rich manganese-based particles and lithium-rich manganese-based secondary particles composed of the single-crystalline lithium-rich manganese-based particles. The single-crystalline lithium-rich manganese-based particles include a doped lithium-rich manganese-based core and a coating layer disposed on the surface of the doped lithium-rich manganese-based core. The lithium-rich manganese-based secondary particles include 2 to 40 single-crystalline lithium-rich manganese-based particles. However, the cycling stability of this fast-charging lithium-rich manganese-based positive electrode material is insufficient.

[0007] The lithium-rich manganese-based precursors disclosed in the prior art all have certain drawbacks. Batteries prepared using these precursors often fail to meet the requirements for practical applications in terms of capacity, initial coulombic efficiency, and cycle stability. Therefore, the development and design of a novel lithium-rich manganese-based precursor, as well as its preparation and application, are crucial. Summary of the Invention

[0008] In view of the shortcomings of the prior art, the purpose of the present invention is to provide a tantalum gradient-doped lithium-rich manganese-based precursor and its preparation and application. In the tantalum gradient-doped lithium-rich manganese-based precursor provided by the present invention, the concentration of tantalum element increases along the direction from the core of the lithium-rich manganese-based precursor to the outermost coating layer, and the enrichment of tantalum element in the outermost coating layer is achieved (the tantalum element content is the highest in the outermost coating layer), which not only inhibits the loss of lattice oxygen and structural phase change, but also avoids the structural instability problem caused by the excessive fineness of the primary grains of the outermost coating layer, thereby inhibiting the phase change and voltage attenuation during the battery cycle, and improving the capacity, first coulombic efficiency and cycle stability of the battery prepared with the lithium-rich manganese-based precursor.

[0009] To achieve this object, the present invention adopts the following technical solutions:

[0010] In a first aspect, the present invention provides a tantalum gradient-doped lithium-rich manganese-based precursor, the lithium-rich manganese-based precursor comprising a core and at least one coating layer sequentially coated on the outside of the core;

[0011] The core and all the coating layers contain tantalum elements, and the concentration of the tantalum elements increases along the direction from the core of the lithium-rich manganese-based precursor to the outermost coating layer.

[0012] In the tantalum gradient-doped lithium-manganese-based precursor provided by the present invention, the concentration of tantalum element increases along the direction from the core of the lithium-rich manganese-based precursor to the outermost coating layer, and the enrichment of tantalum element in the outermost coating layer is achieved (the tantalum element content is the highest in the outermost coating layer), which not only inhibits the loss of lattice oxygen and structural phase change, but also avoids the structural instability problem caused by the excessive fineness of the primary grains of the outermost coating layer, thereby inhibiting the phase change and voltage attenuation during the battery cycle, and improving the capacity, first coulombic efficiency and cycle stability of the battery prepared with the lithium-rich manganese-based precursor.

[0013] Preferably, the porosity increases sequentially from the core of the lithium-rich manganese-based precursor to the outermost coating layer.

[0014] In the present invention, the porosity increases successively from the core of the lithium-rich manganese-based precursor to the outermost coating layer, forming a "tight inside and loose outside" structure; the interior is dense, which improves the volume energy density; the exterior is porous, which increases the contact area between the positive electrode material prepared with the lithium-rich manganese-based precursor and the electrolyte.

[0015] Preferably, the porosity of the inner core is 4.1% to 9.6%, for example, it can be 4.1%, 4.5%, 5.0%, 5.5%, 6.0%, 6.5%, 7.0%, 7.5%, 8.0%, 8.5%, 9.0% or 9.6%, but is not limited to the listed values, and other unlisted values ​​within this numerical range are also applicable.

[0016] Preferably, the porosity of each coating layer between the inner core and the outermost coating layer is independently 9.6% to 13.5%, for example, it can be 9.6%, 10.0%, 10.5%, 11.0%, 11.5%, 12.0%, 12.5%, 13.0% or 13.5%, but is not limited to the listed values, and other unlisted values ​​within this numerical range are also applicable.

[0017] Preferably, the porosity of the outermost coating layer is 13.5% to 17%, for example, it can be 13.5%, 14.0%, 14.5%, 15.0%, 15.5%, 16.0%, 16.5% or 17.0%, but is not limited to the listed values, and other unlisted values ​​within this numerical range are also applicable.

[0018] Preferably, the molar fraction of the tantalum element in the core is 0.1% to 0.5%, calculated as a percentage of the total molar amount of the metal elements in the core, for example, it can be 0.1%, 0.15%, 0.2%, 0.25%, 0.3%, 0.35%, 0.4%, 0.45% or 0.5%, but is not limited to the listed values, and other unlisted values ​​within this numerical range are also applicable.

[0019] Preferably, the total molar amount of each coating layer between the core and the outermost coating layer is expressed as a percentage, and the molar fraction of tantalum element in each coating layer between the core and the outermost coating layer is independently 0.1% to 3%, for example, it can be 0.1%, 0.5%, 1.0%, 1.5%, 2.0%, 2.5% or 3.0%, but is not limited to the listed values, and other unlisted values ​​within this numerical range are also applicable.

[0020] Preferably, the molar fraction of the tantalum element in the outermost coating layer is 0.1% to 3% based on the total molar amount of the metal elements in the outermost coating layer, for example, it can be 0.1%, 0.5%, 1.0%, 1.5%, 2.0%, 2.5% or 3.0%, but it is not limited to the listed values, and other unlisted values ​​within this numerical range are also applicable.

[0021] Preferably, the D50 particle size of the inner core is 2 μm to 4 μm, for example, it can be 2.0 μm, 2.2 μm, 2.4 μm, 2.6 μm, 2.8 μm, 3.0 μm, 3.2 μm, 3.4 μm, 3.6 μm, 3.8 μm or 4.0 μm, but not limited to the listed values, other values not listed in the range are also applicable.

[0022] Preferably, the thickness of each coating layer between the inner core and the outermost coating layer is independently 0.1 μm to 0.8 μm, for example, it can be 0.1 μm, 0.2 μm, 0.3 μm, 0.4 μm, 0.5 μm, 0.6 μm, 0.7 μm or 0.8 μm, but not limited to the listed values, other values not listed in the range are also applicable.

[0023] Preferably, the thickness of the outermost coating layer is 0.1 μm to 0.8 μm, for example, it can be 0.1 μm, 0.2 μm, 0.3 μm, 0.4 μm, 0.5 μm, 0.6 μm, 0.7 μm or 0.8 μm, but not limited to the listed values, other values not listed in the range are also applicable.

[0024] Preferably, the lithium-rich manganese-based precursor comprises an inner core, and a coating layer coated outside the inner core.

[0025] Preferably, the lithium-rich manganese-based precursor further comprises a main element manganese and a secondary element, the secondary element comprises any one or a combination of at least two of nickel, cobalt, chromium or iron, typical but non-limiting combinations include a combination of nickel and cobalt, a combination of cobalt and chromium, a combination of chromium and iron, a combination of nickel, cobalt and chromium, or a combination of nickel, cobalt, chromium and iron.

[0026] In a second aspect, the present application provides a preparation method of the lithium-rich manganese-based precursor of the first aspect, the preparation method comprises:

[0027] (1) adding a metal mixed salt solution, a precipitant solution, a complexing agent solution and a tantalum salt solution into a reaction bottom solution to form a reaction solution, and performing a co-precipitation reaction to obtain a solution containing precipitates;

[0028] (2) adding a metal mixed salt solution, a precipitant solution, a complexing agent solution and a tantalum salt solution into the solution containing precipitates obtained in the previous step to form a reaction solution, and performing a co-precipitation reaction, and controlling the concentration of tantalum ions in the reaction solution to be higher than the concentration of tantalum ions in the reaction solution in the previous step, to obtain a solution containing precipitates;

[0029] (3) If only a lithium-rich manganese-based precursor comprising one coating layer is prepared, a lithium-rich manganese-based precursor is obtained after step (2); if a lithium-rich manganese-based precursor comprising at least two coating layers is prepared, step (2) is repeated at least once to obtain a lithium-rich manganese-based precursor.

[0030] Preferably, during the coprecipitation reaction in step (2), the pH of the reaction solution is controlled to be lower than the pH of the reaction solution in the previous step.

[0031] In the present invention, during the coprecipitation reaction in step (2), the pH of the reaction solution is controlled to be lower than the pH of the reaction solution in the previous step. During the entire coprecipitation process, the pH of the reaction solution decreases gradually from the inner layer to the outer layer in a gradient, thereby forming a lithium-rich manganese-based precursor with a dense inner layer and a loose outer layer, and the primary particles in the outermost coating layer are in the shape of fine whiskers, which is conducive to lithium ion transmission, thereby improving the electrochemical performance of the battery prepared with the lithium-rich manganese-based precursor.

[0032] Preferably, the pH of the reaction solution in step (1) is controlled to be 10 to 11.5, for example, 10, 10.5, 11.0, 11.1, 11.2, 11.3, 11.4 or 11.5, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0033] Preferably, the pH of the reaction solution in step (2) is controlled to be 9 to 10, for example, 9.0, 9.2, 9.4, 9.6, 9.8 or 10.0, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0034] Preferably, the complexing agent concentration of the reaction solution in step (1) is controlled to be 7 g / L to 10 g / L, for example, 7 g / L, 7.5 g / L, 8 g / L, 8.5 g / L, 9 g / L, 9.5 g / L or 10 g / L, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0035] Preferably, the complexing agent concentration of the reaction solution in step (2) is controlled to be 3 g / L to 5 g / L, for example, 3 g / L, 3.2 g / L, 3.5 g / L, 3.8 g / L, 4 g / L, 4.2 g / L, 4.5 g / L, 4.8 g / L or 5 g / L, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0036] Preferably, in step (1), the metal mixed salt solution, the precipitant solution and the complexing agent solution are added to the reaction base solution in parallel, while the tantalum salt solution is added to the reaction base solution separately.

[0037] Preferably, in step (2), the metal mixed salt solution, the precipitant solution and the complexing agent solution are added concurrently to the solution containing the precipitate obtained in the previous step, while the tantalum salt solution is added separately to the solution containing the precipitate obtained in the previous step.

[0038] Preferably, the total metal ion concentration in the metal mixed salt solution in step (1) and step (2) is independently 1 mol / L to 1.5 mol / L, for example, it can be 1.0 mol / L, 1.1 mol / L, 1.2 mol / L, 1.3 mol / L, 1.4 mol / L or 1.5 mol / L, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0039] Preferably, the metal mixed salt solutions in step (1) and step (2) independently include manganese salt and auxiliary element salt.

[0040] Preferably, the auxiliary element salt comprises any one of nickel salt, cobalt salt, chromium salt or iron salt or a combination of at least two thereof. Typical but non-limiting combinations include a combination of nickel salt and cobalt salt, a combination of cobalt salt and chromium salt, a combination of nickel salt and chromium salt, a combination of nickel salt, cobalt salt and chromium salt, or a combination of nickel salt, cobalt salt, chromium salt and iron salt.

[0041] Preferably, the manganese salt comprises any one or a combination of at least two of manganese chloride, manganese sulfate or manganese nitrate. Typical but non-limiting combinations include a combination of manganese chloride and manganese sulfate, a combination of manganese sulfate and manganese nitrate, or a combination of manganese chloride, manganese sulfate and manganese nitrate, preferably manganese chloride.

[0042] Preferably, the nickel salt comprises any one or a combination of at least two of nickel chloride, nickel sulfate or nickel nitrate. Typical but non-limiting combinations include a combination of nickel chloride and nickel sulfate, a combination of nickel sulfate and nickel nitrate, or a combination of nickel chloride, nickel sulfate and nickel nitrate, preferably nickel chloride.

[0043] Preferably, the cobalt salt comprises any one or a combination of at least two of cobalt chloride, cobalt sulfate or cobalt nitrate. Typical but non-limiting combinations include a combination of cobalt chloride and cobalt sulfate, a combination of cobalt sulfate and cobalt nitrate, or a combination of cobalt chloride, cobalt sulfate and cobalt nitrate, preferably cobalt chloride.

[0044] Preferably, the chromium salt comprises any one or a combination of at least two of chromium chloride, chromium sulfate or chromium nitrate. Typical but non-limiting combinations include a combination of chromium chloride and chromium sulfate, a combination of chromium sulfate and chromium nitrate, or a combination of chromium chloride, chromium sulfate and chromium nitrate, preferably chromium chloride.

[0045] Preferably, the iron salt comprises any one or a combination of at least two of ferric chloride, ferric sulfate or ferric nitrate. Typical but non-limiting combinations include a combination of ferric chloride and ferric sulfate, a combination of ferric sulfate and ferric nitrate, a combination of ferric chloride and ferric nitrate, or a combination of ferric chloride, ferric sulfate and ferric nitrate.

[0046] Preferably, the flow rate of the metal mixed salt solution added in parallel in step (1) and step (2) is 5 L / h to 40 L / h, for example, it can be 5 L / h, 10 L / h, 15 L / h, 20 L / h, 25 L / h, 30 L / h, 35 L / h or 40 L / h, but is not limited to the listed values, and other values ​​not listed within this numerical range are also applicable.

[0047] Preferably, the concentration of the precipitant in the precipitant solution in step (1) and step (2) is independently 10 mol / L to 20 mol / L, for example, 10 mol / L, 12 mol / L, 14 mol / L, 16 mol / L, 18 mol / L or 20 mol / L, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0048] Preferably, the precipitant in the precipitant solution in step (1) and step (2) independently comprises any one of sodium hydroxide, potassium hydroxide, sodium carbonate or potassium carbonate, or a combination of at least two thereof. Typical but non-limiting combinations include a combination of sodium hydroxide and potassium hydroxide, a combination of sodium carbonate and potassium carbonate, a combination of sodium hydroxide and sodium carbonate, a combination of potassium hydroxide and potassium carbonate, or a combination of sodium hydroxide, potassium hydroxide and sodium carbonate.

[0049] Preferably, the concentration of the complexing agent in the complexing agent solution in step (1) and step (2) is 5 mol / L to 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, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0050] Preferably, the complexing agent in the complexing agent solution in step (1) and step (2) independently includes any one of ammonia, disodium edetate, trisodium citrate or oxalic acid, or a combination of at least two of them. Typical but non-limiting combinations include a combination of ammonia and disodium edetate, a combination of trisodium citrate and oxalic acid, a combination of disodium edetate and trisodium citrate, or a combination of ammonia, disodium edetate and trisodium citrate.

[0051] Preferably, the concentration of the tantalum salt in the tantalum salt solution in step (1) and step (2) is independently 0.05 mol / L to 1 mol / L, for example, it can be 0.05 mol / L, 0.1 mol / L, 0.2 mol / L, 0.3 mol / L, 0.4 mol / L, 0.5 mol / L, 0.6 mol / L, 0.7 mol / L, 0.8 mol / L, 0.9 mol / L or 1.0 mol / L, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0052] Preferably, the tantalum salt comprises tantalum chloride and / or tantalum nitrate.

[0053] Preferably, the flow rate of adding the tantalum salt solution in step (1) and step (2) is 0.4 L / h to 2.0 L / h, for example, it can be 0.4 L / h, 0.6 L / h, 0.8 L / h, 1.0 L / h, 1.2 L / h, 1.4 L / h, 1.6 L / h, 1.8 L / h or 2.0 L / h, but is not limited to the listed values, and other unlisted values ​​within this numerical range are also applicable.

[0054] Preferably, the reaction base liquid in step (1) is prepared by adding a precipitant and a complexing agent to a water solvent.

[0055] The concentration and pH of the reaction base solution in the present invention are not limited and are determined according to the concentration and flow rate of the complexing agent solution and the precipitant solution.

[0056] Preferably, the temperature of the reaction solution in step (1) and step (2) is independently controlled to be 40°C to 55°C, for example, it can be 40°C, 41°C, 42°C, 43°C, 44°C, 45°C, 46°C, 47°C, 48°C, 49°C, 50°C, 51°C, 52°C, 53°C, 54°C or 55°C, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0057] Preferably, the molar amount of tantalum ions in the reaction solution in step (1) is controlled to be 0.1% to 0.5% of the total molar amount of metal ions in the reaction solution, for example, it can be 0.1%, 0.15%, 0.2%, 0.25%, 0.3%, 0.35%, 0.4%, 0.45% or 0.5%, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0058] Preferably, in step (2), the molar amount of tantalum ions in the coprecipitation reaction is controlled to be 0.1% to 3% of the total molar amount of metal ions in the reaction solution, for example, it can be 0.1%, 0.5%, 1.0%, 1.5%, 2.0%, 2.5% or 3.0%, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0059] Preferably, the co-precipitation reaction in step (1) and step (2) is carried out while stirring at a rotation speed of 80 rpm to 250 rpm, for example, 80 rpm, 100 rpm, 120 rpm, 140 rpm, 160 rpm, 180 rpm, 200 rpm, 220 rpm, 240 rpm or 250 rpm, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0060] Preferably, the preparation method comprises:

[0061] (1) adding a metal mixed salt solution having a total metal ion concentration of 1 mol / L to 1.5 mol / L, a precipitant solution, and a complexing agent solution concurrently to a reaction base solution, while separately adding a tantalum salt solution having a concentration of 0.05 mol / L to 1 mol / L to the reaction base solution to form a first reaction solution, performing a first coprecipitation reaction, and obtaining a solution containing a precipitate;

[0062] During the first coprecipitation reaction, the pH of the first reaction solution is controlled to be 10-11.5, the concentration of the complexing agent is 7 g / L-10 g / L, the temperature is 40° C.-55° C., the molar amount of tantalum ions accounts for 0.1%-0.5% of the total molar amount of metal ions in the first reaction solution, and the stirring is performed at a speed of 80 rpm-250 rpm;

[0063] (2) adding a metal mixed salt solution (including a manganese salt and an auxiliary element salt, wherein the auxiliary element salt includes any one or a combination of at least two of nickel salt, cobalt salt or chromium salt) having a total metal ion concentration of 1 to 1.5 mol / L, a precipitant solution and a complexing agent solution, and adding a tantalum salt solution having a concentration of 0.05 mol / L to 1 mol / L separately to the solution containing the precipitate obtained in the previous step to form a second reaction solution, and performing a second coprecipitation reaction to obtain a solution containing the precipitate;

[0064] During the second coprecipitation reaction, the tantalum ion concentration in the second reaction solution is controlled to be higher than the tantalum ion concentration in the reaction solution in the previous step, the pH is 9 to 10 and lower than the pH of the reaction solution in the previous step, the complexing agent concentration is 3 g / L to 5 g / L, the temperature is 40° C. to 55° C., the molar amount of tantalum ions accounts for 0.1% to 3% of the total molar amount of metal ions in the second reaction solution, and the stirring is carried out at a speed of 80 rpm to 250 rpm;

[0065] (3) If only a lithium-rich manganese-based precursor comprising one coating layer is prepared, a lithium-rich manganese-based precursor is obtained after step (2); if a lithium-rich manganese-based precursor comprising at least two coating layers is prepared, step (2) is repeated at least once to obtain a lithium-rich manganese-based precursor.

[0066] In a third aspect, the present invention provides a positive electrode material, which is prepared from a raw material comprising the lithium-rich manganese-based precursor described in the first aspect.

[0067] Preferably, the method for preparing the positive electrode material comprises:

[0068] After mixing the lithium source and the lithium-rich manganese-based precursor described in the first aspect, sintering is performed to obtain the positive electrode material.

[0069] In the present invention, the cathode material is obtained in a single crystal form after sintering, and the cathode material in a single crystal form further reduces the obstruction of the grain boundary to ion diffusion.

[0070] Preferably, the molar ratio of the lithium source to the lithium-rich manganese-based precursor in the mixture is (1-1.2):1, for example, it can be 1:1, 1.02:1, 1.04:1, 1.06:1, 1.08:1, 1.10:1, 1.12:1, 1.14:1, 1.16:1, 1.18:1 or 1.20:1, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0071] Preferably, the lithium source comprises lithium hydroxide and / or lithium carbonate.

[0072] Preferably, the sintering is performed at a temperature of 300° C. to 450° C. for a time of 4 hours to 10 hours in an oxygen atmosphere.

[0073] In the present invention, the sintering temperature is 300°C to 450°C, for example, it can be 300°C, 320°C, 340°C, 360°C, 380°C, 400°C, 420°C, 440°C or 450°C, but is not limited to the listed values. Other values ​​not listed within this numerical range are also applicable.

[0074] In the present invention, the sintering time is 4h to 10h, for example, it can be 4h, 4.5h, 5h, 5.5h, 6h, 6.5h, 7h, 7.5h, 8h, 8.5h, 9h, 9.5h or 10h, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0075] Preferably, the method for preparing the positive electrode material comprises:

[0076] After mixing the lithium source and the lithium-rich manganese-based precursor described in the first aspect at a molar ratio of (1-1.2):1, sintering is performed at 300° C. to 450° C. for 4 h to 10 h in an oxygen atmosphere to obtain a positive electrode material.

[0077] In a fourth aspect, the present invention provides a composite positive electrode material, which includes a positive electrode material core, and an interface buffer layer, an ion conductivity enhancement layer and an interface layer sequentially coated on the outside of the positive electrode material core; the positive electrode material in the positive electrode material core includes the positive electrode material described in the third aspect.

[0078] In the present invention, the interface buffer layer in the composite positive electrode material can block the transition metal (such as Mn 3+ ) to the electrolyte, while preventing S or O in the electrolyte from back-diffusion to the positive electrode, thereby reducing the risk of phase change and capacity attenuation of the composite positive electrode material and improving the electrochemical performance of the battery prepared with the composite positive electrode material.

[0079] In the present invention, the ionic conductivity enhancement layer in the composite positive electrode material can enhance the provision of ultra-high ionic conductivity and improve the rate performance of the battery; and in conjunction with the interface layer in the composite positive electrode material, the stability of the interface layer is utilized to prevent harmful side reactions (such as reduction decomposition) between the negative electrode material and the inner layer sulfide, thereby stabilizing the interface of the composite positive electrode material, reducing the interface impedance, and improving the cycle life of the battery prepared with the composite positive electrode material.

[0080] Preferably, the interface buffer layer comprises a Li-TM-OSP interface buffer layer, wherein TM comprises a main element manganese and an auxiliary element.

[0081] Preferably, the thickness of the interface buffer layer is 100nm to 200nm, for example, it can be 100nm, 110nm, 120nm, 130nm, 140nm, 150nm, 160nm, 170nm, 180nm, 190nm or 200nm, but is not limited to the listed values, and other unlisted values ​​within this numerical range are also applicable.

[0082] Preferably, the material of the ionic conductivity enhanced layer includes any one or a combination of at least two of sulfide solid electrolyte (chemical formula: Li6PS5Cl), sodium fluoroniobate (chemical formula: Na3NbF8) or lithium oxychloride (chemical formula: Li3OCl).

[0083] Preferably, the thickness of the ionic conductivity enhanced layer is 180 nm to 300 nm, for example, it can be 180 nm, 190 nm, 200 nm, 210 nm, 220 nm, 230 nm, 240 nm, 250 nm, 260 nm, 270 nm, 280 nm, 290 nm or 300 nm, but is not limited to the listed values, and other unlisted values ​​within this numerical range are also applicable.

[0084] Preferably, the material of the interface layer includes LLZO (garnet-type solid electrolyte, chemical formula is Li7La3Zr2O 12 ) and / or LAGP (chemical formula is Li 1.5 Al 0.5 Ge 1.5 (PO4)3), typical but non-limiting combinations include a combination of a sulfide solid electrolyte and sodium fluoroniobate, a combination of sodium fluoroniobate and lithium oxychloride, a combination of a sulfide solid electrolyte and lithium oxychloride, or a combination of a sulfide solid electrolyte, sodium fluoroniobate and lithium oxychloride.

[0085] In the present invention, the ion conductivity enhancing layer and the interface layer are preferably composite solid electrolyte layers. The composite positive electrode material enhances the electron / ion transport performance and interface stability of the lithium-rich manganese-based positive electrode material through the coordinated design of the lithium-rich manganese-based positive electrode material and the composite solid electrolyte layer, providing a feasible technical path for high energy density solid-state batteries.

[0086] Preferably, the thickness of the interface layer is 50nm to 100nm, for example, it can be 50nm, 55nm, 60nm, 65nm, 70nm, 75nm, 80nm, 85nm, 90nm, 95nm or 100nm, but is not limited to the listed values. Other unlisted values ​​within this numerical range are also applicable.

[0087] In a fifth aspect, the present invention provides a process for preparing the composite positive electrode material according to the fourth aspect, the process comprising:

[0088] On the surface of the positive electrode material described in the third aspect, the ion conductivity enhancing material and the interface material are deposited in sequence, and then heat treated to obtain a composite positive electrode material.

[0089] Preferably, the deposition method includes magnetron sputtering and / or spray pyrolysis.

[0090] In the present invention, the deposition process is followed by heat treatment to form an interface buffer layer between the positive electrode material and the ion conductivity enhancement layer. The interface buffer layer suppresses the mutual diffusion of elements and space charge effect in the composite positive electrode material.

[0091] Preferably, after the deposition, the mass ratio of the positive electrode material to the ion conductivity enhancing material is (8-6): (1-3), for example, it can be 8:1, 7:1, 6:1, 8:2, 7:2, 6:2, 8:3, 7:3 or 6:3, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0092] Preferably, after the deposition, the mass ratio of the ionic conductivity enhancing material to the interface material is (1 to 3):1, for example, it can be 1:1, 1.5:1, 2:1, 2.5:1 or 3:1, but is not limited to the listed values, and other unlisted values ​​within this numerical range are also applicable.

[0093] Preferably, the heat treatment includes sequentially performing a first temperature increase, a first temperature preservation, a second temperature increase and a second temperature preservation in a protective atmosphere.

[0094] Preferably, the protective atmosphere comprises nitrogen and / or an inert gas.

[0095] Preferably, the heating rate of the first heating is 1°C / min to 15°C / min, for example, it can be 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, 10°C / min, 12°C / min or 15°C / min, and the end temperature is the same as the temperature of the first insulation.

[0096] Preferably, the temperature of the first insulation is 300° C. to 500° C., and the time is 8 h to 12 h.

[0097] In the present invention, the temperature of the first insulation is 300°C to 500°C, for example, it can be 300°C, 325°C, 350°C, 375°C, 400°C, 425°C, 450°C, 475°C or 500°C, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0098] In the present invention, the first insulation time is 8h to 12h, for example, it can be 8h, 8.5h, 9h, 9.5h, 10h, 10.5h, 11h, 11.5h or 12h, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0099] Preferably, the heating rate of the second heating is 1°C / min to 15°C / min, for example, it can be 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, 10°C / min, 12°C / min or 15°C / min, and the end temperature is the same as the temperature of the first insulation.

[0100] Preferably, the temperature of the second insulation is 850° C. to 900° C., and the time is 4 hours to 6 hours.

[0101] In the present invention, the temperature of the second insulation is 850℃~900℃, for example, it can be 850℃, 860℃, 870℃, 880℃, 890℃ or 900℃, but is not limited to the listed values. Other unlisted values ​​within this numerical range are also applicable.

[0102] In the present invention, the second insulation time is 4h to 6h, for example, it can be 4h, 4.5h, 5h, 5.5h or 6h, but is not limited to the listed values. Other values ​​not listed within the numerical range are also applicable.

[0103] Preferably, the preparation process comprises:

[0104] On the surface of the positive electrode material described in the third aspect, an ion conductivity enhancing material and an interface material are sequentially deposited to obtain an intermediate material, wherein the mass ratio of the positive electrode material, the ion conductivity enhancing material and the interface material in the obtained intermediate material is (8-6):(1-3):1;

[0105] Then, in a protective atmosphere, the intermediate material is heated to 300°C to 500°C at a heating rate of 1°C / min to 15°C / min, and then kept warm for 8h to 12h. Then, the temperature is heated to 850°C-900°C at a heating rate of 1°C / min to 15°C / min, and then kept warm for 4h to 6h to obtain a composite positive electrode material.

[0106] In a sixth aspect, the present invention provides a solid-state battery, comprising the positive electrode material described in the third aspect and / or the composite positive electrode material described in the fourth aspect.

[0107] The numerical range described in the present invention includes not only the point values ​​listed above, but also any point values ​​between the above numerical ranges that are not listed. Due to space limitations and for the sake of simplicity, the present invention no longer exhaustively lists the specific point values ​​included in the range.

[0108] Compared with the prior art, the present invention has the following beneficial effects:

[0109] In the tantalum gradient-doped lithium-manganese-based precursor provided by the present invention, the concentration of tantalum element increases along the direction from the core of the lithium-rich manganese-based precursor to the outermost coating layer, and the enrichment of tantalum element in the outermost coating layer is achieved (the tantalum element content is the highest in the outermost coating layer), which not only inhibits the loss of lattice oxygen and structural phase change, but also avoids the structural instability problem caused by the excessive fineness of the primary grains of the outermost coating layer, thereby inhibiting the phase change and voltage attenuation during the battery cycle, and improving the capacity, first coulombic efficiency and cycle stability of the battery prepared with the lithium-rich manganese-based precursor. DETAILED DESCRIPTION

[0110] The technical solution of the present invention is further described below by way of specific embodiments. It should be understood by those skilled in the art that the embodiments are merely to help understand the present invention and should not be regarded as specific limitations of the present invention.

[0111] Example 1

[0112] This embodiment provides a tantalum gradient-doped lithium-rich manganese-based precursor, the lithium-rich manganese-based precursor comprising a core and a coating layer (i.e., an outermost coating layer) coated on the outside of the core;

[0113] The porosity increases in sequence from the core of the lithium-rich manganese-based precursor to the outermost coating layer;

[0114] The porosity of the inner core is 5.2%, and the porosity of the outermost coating layer is 15%;

[0115] The core and all coating layers contain tantalum, and the concentration of tantalum increases along the direction from the core of the lithium-rich manganese-based precursor to the outermost coating layer;

[0116] The D50 particle size of the core is 3 μm; the core contains tantalum, main element manganese and auxiliary elements (including nickel, iron and manganese);

[0117] The thickness of the outermost coating layer is 0.5 μm; the outermost coating layer contains tantalum, main element manganese and auxiliary elements (including nickel, iron and manganese);

[0118] The molar fraction of the tantalum element in the core is 0.3%, calculated as a percentage of the total molar amount of the metal elements in the core;

[0119] Calculated as a percentage based on the total molar amount of the outermost coating layer, the molar fraction of the tantalum element in the outermost coating layer is 1.5%.

[0120] The preparation method of the lithium-rich manganese-based precursor comprises:

[0121] (1) adding a metal mixed salt solution (containing nickel ions, iron ions, and manganese ions in a molar ratio of 25:25:50) having a total metal ion concentration of 1.5 mol / L, a sodium hydroxide solution, and an ammonia solution in parallel to a reaction base solution, and adding a tantalum chloride solution having a concentration of 1 mol / L to the reaction base solution at a feed rate of 0.4 L / h to form a first reaction solution, performing a first coprecipitation reaction, and obtaining a solution containing a precipitate;

[0122] During the first coprecipitation reaction, the pH of the first reaction solution was controlled to be 10.8, the ammonia concentration was 8.5 g / L, the temperature was 55° C., the molar amount of tantalum ions accounted for 0.3% of the total molar amount of metal ions in the first reaction solution, and the stirring was carried out at a speed of 240 rpm;

[0123] (2) adding a metal mixed salt solution (containing nickel ions, iron ions, and manganese ions in a molar ratio of 25:25:50) with a total metal ion concentration of 1.5 mol / L, a sodium hydroxide solution, and aqueous ammonia in parallel to the solution containing the precipitate obtained in the previous step, and adding a tantalum chloride solution with a concentration of 1 mol / L separately at a feed rate of 2 L / h to form a second reaction solution, and performing a second coprecipitation reaction to obtain a solution containing the precipitate;

[0124] During the second coprecipitation reaction, the pH of the second reaction solution was controlled to be 9.5, the ammonia concentration was 4 g / L, the temperature was 55° C., the molar amount of tantalum ions accounted for 1.5% of the total molar amount of metal ions in the second reaction solution, and the stirring was carried out at a speed of 240 rpm.

[0125] This embodiment further provides a positive electrode material, and a method for preparing the positive electrode material includes:

[0126] Lithium hydroxide and the lithium-rich manganese-based precursor provided by the present invention were mixed in a molar ratio of 1.1:1, and then sintered at 350° C. for 7 hours in an oxygen atmosphere to obtain a positive electrode material.

[0127] This embodiment also provides a composite positive electrode material, which includes a positive electrode material core, and a Li-TM-OSP interface buffer layer with a thickness of 150nm (TM includes the main element manganese and auxiliary elements), a Li6PS5Cl layer with a thickness of 200nm, and a Li7La3Zr2O layer with a thickness of 100nm. 12 layer; the positive electrode material in the positive electrode material core is the positive electrode material provided in this embodiment.

[0128] The preparation process of the composite positive electrode material is as follows:

[0129] On the surface of the positive electrode material provided in this embodiment, Li6PS5Cl and Li7La3Zr2O are sequentially deposited by magnetron sputtering.12 The intermediate material is deposited to obtain the positive electrode material, Li6PS5Cl and Li7La3Zr2O 12 The mass ratio is 7:2:1;

[0130] Then, in an argon atmosphere, the intermediate material was heated to 400°C at a heating rate of 8°C / min and kept warm for 10 hours, and then heated to 900°C at a heating rate of 8°C / min and kept warm for 6 hours to obtain a composite positive electrode material.

[0131] Example 2

[0132] This embodiment provides a tantalum gradient-doped lithium-rich manganese-based precursor, the lithium-rich manganese-based precursor comprising a core and at least one coating layer sequentially coated on the outside of the core;

[0133] The porosity increases in sequence from the core of the lithium-rich manganese-based precursor to the outermost coating layer;

[0134] The porosity of the inner core is 9.6%, and the porosity of the outermost coating layer is 17%;

[0135] The core and all coating layers contain tantalum, and the concentration of tantalum increases along the direction from the core of the lithium-rich manganese-based precursor to the outermost coating layer;

[0136] The D50 particle size of the core is 4 μm; the core contains tantalum, main element manganese and auxiliary elements (including nickel, iron and manganese);

[0137] The thickness of the outermost coating layer is 0.8 μm; the outermost coating layer contains tantalum, main element manganese and auxiliary elements (including nickel, iron and manganese);

[0138] The molar fraction of the tantalum element in the core is 0.5%, calculated as a percentage of the total molar amount of the metal elements in the core;

[0139] Calculated as a percentage based on the total molar amount of the coating layer, the molar fraction of the tantalum element in the coating layer is independently 3%.

[0140] The preparation method of the lithium-rich manganese-based precursor includes:

[0141] (1) adding a metal mixed salt solution (containing nickel ions, iron ions, and manganese ions in a molar ratio of 20:25:55) having a total metal ion concentration of 1.2 mol / L, a sodium hydroxide solution, and an ammonia solution in parallel to a reaction base solution, and adding a tantalum nitrate solution having a concentration of 0.5 mol / L to the reaction base solution at a feed rate of 0.6 L / h to form a first reaction solution, performing a first coprecipitation reaction, and obtaining a solution containing a precipitate;

[0142] During the first coprecipitation reaction, the pH of the first reaction solution was controlled to be 11, the ammonia concentration was 7 g / L, the temperature was 40° C., the molar amount of tantalum ions accounted for 0.5% of the total molar amount of metal ions in the first reaction solution, and the stirring was carried out at a speed of 250 rpm;

[0143] (2) adding a metal mixed salt solution (containing nickel ions, iron ions, and manganese ions in a molar ratio of 20:25:55) having a total metal ion concentration of 1.2 mol / L, a sodium hydroxide solution, and aqueous ammonia in parallel to the solution containing the precipitate obtained in the previous step, and adding a tantalum nitrate solution having a concentration of 0.5 mol / L separately at a feed rate of 3 L / h to form a second reaction solution, and performing a second coprecipitation reaction to obtain a solution containing a precipitate;

[0144] During the second coprecipitation reaction, the pH of the second reaction solution was controlled to be 9, the ammonia concentration was 3 g / L, the temperature was 40° C., the molar amount of tantalum ions accounted for 3% of the total molar amount of metal ions in the second reaction solution, and the stirring was carried out at a speed of 250 rpm.

[0145] This embodiment further provides a positive electrode material, and a method for preparing the positive electrode material includes:

[0146] After mixing lithium hydroxide and the lithium-rich manganese-based precursor provided by the present invention at a molar ratio of 1.2:1, sintering was performed at 300° C. for 10 hours in an oxygen atmosphere to obtain a positive electrode material;

[0147] This embodiment also provides a composite positive electrode material, which includes a positive electrode material core, and a Li-TM-OSP interface buffer layer with a thickness of 200nm (TM includes the main element manganese and auxiliary elements), a Li6PS5Cl layer with a thickness of 300nm, and a Li7La3Zr2O layer with a thickness of 80nm. 12 layer; the positive electrode material in the positive electrode material core is the positive electrode material provided in this embodiment;

[0148] The preparation process of the composite positive electrode material is as follows:

[0149] On the surface of the positive electrode material provided in this embodiment, Li6PS5Cl and Li7La3Zr2O are sequentially deposited by spray pyrolysis. 12 The intermediate material is deposited to obtain the positive electrode material, Li6PS5Cl and Li7La3Zr2O 12 The mass ratio is 6:3:1;

[0150] Then, in an argon atmosphere, the intermediate material was heated to 300°C at a heating rate of 1°C / min and kept warm for 12 hours, and then heated to 850°C at a heating rate of 15°C / min and kept warm for 6 hours to obtain a composite positive electrode material.

[0151] Example 3

[0152] This embodiment provides a tantalum gradient-doped lithium-rich manganese-based precursor, the lithium-rich manganese-based precursor comprising a core and at least one coating layer sequentially coated on the outside of the core;

[0153] The porosity increases in sequence from the core of the lithium-rich manganese-based precursor to the outermost coating layer;

[0154] The porosity of the inner core is 6.2%, and the porosity of the outermost coating layer is 13.5%;

[0155] The core and all coating layers contain tantalum, and the concentration of tantalum increases along the direction from the core of the lithium-rich manganese-based precursor to the outermost coating layer;

[0156] The D50 particle size of the core is 2 μm; the core contains tantalum, main element manganese and auxiliary elements (including nickel, iron and manganese);

[0157] The thickness of the outermost coating layer is 0.1 μm; the outermost coating layer contains tantalum, main element manganese and auxiliary elements (including nickel, iron and manganese);

[0158] The molar fraction of the tantalum element in the core is 0.1%, calculated as a percentage of the total molar amount of the metal elements in the core;

[0159] Calculated as a percentage of the total molar amount of the coating layer, the molar fraction of the tantalum element in the coating layer is independently 1%.

[0160] The preparation method of the lithium-rich manganese-based precursor includes:

[0161] (1) adding a metal mixed salt solution having a total metal ion concentration of 1 mol / L (containing nickel ions, iron ions, and manganese ions in a molar ratio of 25:20:55), a sodium hydroxide solution, and an ammonia solution in parallel to a reaction base solution, and adding a tantalum chloride solution having a concentration of 0.1 mol / L to the reaction base solution at a feed rate of 0.2 L / h to form a first reaction solution, and performing a first coprecipitation reaction to obtain a solution containing a precipitate;

[0162] During the first coprecipitation reaction, the pH of the first reaction solution was controlled to be 11.5, the ammonia concentration was 10 g / L, the temperature was 50° C., the molar amount of tantalum ions accounted for 0.1% of the total molar amount of metal ions in the first reaction solution, and the stirring was performed at a speed of 80 rpm;

[0163] (2) adding a metal mixed salt solution (containing nickel ions, iron ions, and manganese ions in a molar ratio of 25:20:55) having a total metal ion concentration of 1 mol / Lmol / L, a sodium hydroxide solution, and aqueous ammonia in parallel to the solution containing the precipitate obtained in the previous step, and adding a tantalum salt solution having a concentration of 0.1 mol / L separately at a feed rate of 1.5 L / h to form a second reaction solution, and performing a second coprecipitation reaction to obtain a solution containing the precipitate;

[0164] During the second coprecipitation reaction, the pH of the second reaction solution was controlled to be 10, the ammonia concentration was 5 g / L, the temperature was 50° C., the molar amount of tantalum ions accounted for 1% of the total molar amount of metal ions in the second reaction solution, and the stirring was carried out at a speed of 80 rpm.

[0165] This embodiment further provides a positive electrode material, and a method for preparing the positive electrode material includes:

[0166] After mixing lithium carbonate and the lithium-rich manganese-based precursor provided by the present invention in a molar ratio of 1:1, sintering was performed at 450° C. for 4 hours in an oxygen atmosphere to obtain a positive electrode material.

[0167] This embodiment also provides a composite positive electrode material, which includes a positive electrode material core, and a Li-TM-OSP interface buffer layer with a thickness of 100 nm (TM includes the main element manganese and auxiliary elements), a Li6PS5Cl layer with a thickness of 180 nm, and a Li7La3Zr2O layer with a thickness of 50 nm. 12 layer; the positive electrode material in the positive electrode material core is the positive electrode material provided in this embodiment;

[0168] The preparation process of the composite positive electrode material is as follows:

[0169] On the surface of the positive electrode material provided in this embodiment, Li6PS5Cl and Li7La3Zr2O are sequentially deposited by magnetron sputtering. 12 The intermediate material is deposited to obtain the positive electrode material, Li6PS5Cl and Li7La3Zr2O 12 The mass ratio is 8:1:1;

[0170] Then, in a nitrogen atmosphere, the intermediate material was heated to 500°C at a heating rate of 15°C / min and kept warm for 8 hours, and then heated to 880°C at a heating rate of 1°C / min and kept warm for 5 hours to obtain a composite positive electrode material.

[0171] Example 4

[0172] This embodiment provides a tantalum gradient-doped lithium-rich manganese-based precursor, the lithium-rich manganese-based precursor comprising a core, and two coating layers sequentially coated on the outside of the core (i.e., an intermediate coating layer and an outermost coating layer sequentially coated on the outside of the core);

[0173] The porosity increases in sequence from the core of the lithium-rich manganese-based precursor to the outermost coating layer;

[0174] The porosity of the inner core is 4.1%, the porosity of the intermediate coating layer is 12%, and the porosity of the outermost coating layer is 15%;

[0175] The core and all coating layers contain tantalum, and the concentration of tantalum increases along the direction from the core of the lithium-rich manganese-based precursor to the outermost coating layer;

[0176] The D50 particle size of the core is 3 μm; the core contains tantalum, main element manganese and auxiliary elements (including nickel, iron and manganese);

[0177] The thickness of the intermediate coating layer is 0.8 μm; the intermediate coating layer contains tantalum, main element manganese and auxiliary elements (including nickel, iron and manganese);

[0178] The thickness of the outermost coating layer is 0.5 μm; the outermost coating layer contains tantalum, main element manganese and auxiliary elements (including nickel, iron and manganese);

[0179] The molar fraction of the tantalum element in the core is 0.3%, calculated as a percentage of the total molar amount of the metal elements in the core;

[0180] Calculated as a percentage of the total molar amount of the intermediate coating layer, the molar fraction of the tantalum element in the intermediate coating layer is independently 1%;

[0181] Calculated as a percentage based on the total molar amount of the coating layer, the molar fraction of the tantalum element in the coating layer is independently 1.5%.

[0182] The preparation method of the lithium-rich manganese-based precursor includes:

[0183] (1) adding a metal mixed salt solution (containing nickel ions, iron ions, and manganese ions in a molar ratio of 25:20:55) having a total metal ion concentration of 1.5 mol / L, a sodium hydroxide solution, and an ammonia solution in parallel to a reaction base solution, and adding a tantalum chloride solution having a concentration of 1 mol / L to the reaction base solution at a feed rate of 0.4 L / h to form a first reaction solution, performing a first coprecipitation reaction, and obtaining a solution containing a precipitate;

[0184] During the first coprecipitation reaction, the pH of the first reaction solution was controlled to be 11.5, the ammonia concentration was 8.5 g / L, the temperature was 55° C., the molar amount of tantalum ions accounted for 0.3% of the total molar amount of metal ions in the first reaction solution, and the stirring was carried out at a speed of 240 rpm;

[0185] (2) adding a metal mixed salt solution (containing nickel ions, iron ions, and manganese ions in a molar ratio of 25:20:55) having a total metal ion concentration of 1.5 mol / L, a sodium hydroxide solution, and aqueous ammonia in parallel to the solution containing the precipitate obtained in the previous step, and adding a tantalum chloride solution having a concentration of 1 mol / L separately at a feed rate of 1.3 L / h to form a second reaction solution, and performing a second coprecipitation reaction to obtain a solution containing the precipitate;

[0186] During the second coprecipitation reaction, the pH of the second reaction solution was controlled to be 10, the ammonia concentration was 4 g / L, the temperature was 55° C., the molar amount of tantalum ions accounted for 1% of the total molar amount of metal ions in the second reaction solution, and stirring was performed at a speed of 240 rpm;

[0187] (3) adding a mixed metal salt solution (containing nickel ions, iron ions, and manganese ions at a molar ratio of ...) having a total metal ion concentration of 1.5 mol / L, a sodium hydroxide solution, and aqueous ammonia concurrently to the solution containing the precipitate obtained in the previous step, and adding a tantalum chloride solution having a concentration of 1 mol / L separately to form a third reaction solution, and performing a third coprecipitation reaction to obtain a solution containing the precipitate;

[0188] During the third coprecipitation reaction, the pH of the third reaction solution was controlled to be 9.5, the ammonia concentration was 3 g / L, the temperature was 55° C., the molar amount of tantalum ions accounted for 1.5% of the total molar amount of metal ions in the third reaction solution, and the solution was stirred at a speed of 240 rpm.

[0189] This embodiment further provides a positive electrode material, which is the same as that of Example 1 except that the lithium-rich manganese-based precursor in the preparation method of the positive electrode material is replaced with the lithium-rich manganese-based precursor in this embodiment in an equal molar amount.

[0190] This embodiment further provides a composite positive electrode material, wherein the positive electrode material in the positive electrode material core of the composite positive electrode material is replaced with the positive electrode material provided in this embodiment;

[0191] That is, the steps of the preparation process of the composite positive electrode material are the same as those of Example 1 except that the positive electrode material is replaced with the positive electrode material in this example.

[0192] Example 5

[0193] This embodiment provides a tantalum gradient-doped lithium-rich manganese-based precursor, except that the porosity of the core is the same as that of the outermost coating layer, both of which are 5.2%;

[0194] That is, in step (2) of the method for preparing the lithium-rich manganese-based precursor, the pH of the second reaction solution is adjusted to 10.8 during the second coprecipitation reaction, and the rest is the same as in Example 1.

[0195] This embodiment further provides a positive electrode material, which is the same as that of Example 1 except that the lithium-rich manganese-based precursor in the preparation method of the positive electrode material is replaced with the lithium-rich manganese-based precursor in this embodiment in an equal molar amount.

[0196] This embodiment further provides a composite positive electrode material, wherein the positive electrode material in the positive electrode material core of the composite positive electrode material is replaced with the positive electrode material provided in this embodiment;

[0197] That is, the steps of the preparation process of the composite positive electrode material are the same as those of Example 1 except that the positive electrode material is replaced with the positive electrode material in this example.

[0198] Example 6

[0199] This embodiment provides a tantalum gradient-doped lithium-rich manganese-based precursor, wherein the porosity of the core is higher than that of the outermost coating layer, the porosity of the core is 14.8%, and the porosity of the outermost coating layer is 5.4%;

[0200] That is, in step (1) of the method for preparing the lithium-rich manganese-based precursor, the pH of the first reaction solution in the first coprecipitation reaction is adjusted to 9.5; and in step (2), the pH of the second reaction solution during the second coprecipitation reaction is adjusted to 10.8. Others are the same as in Example 1.

[0201] This embodiment further provides a positive electrode material, which is the same as that of Example 1 except that the lithium-rich manganese-based precursor in the preparation method of the positive electrode material is replaced with the lithium-rich manganese-based precursor in this embodiment in an equal molar amount.

[0202] This embodiment further provides a composite positive electrode material, wherein the positive electrode material in the positive electrode material core of the composite positive electrode material is replaced with the positive electrode material provided in this embodiment;

[0203] That is, the steps of the preparation process of the composite positive electrode material are the same as those of Example 1 except that the positive electrode material is replaced with the positive electrode material in this example.

[0204] Example 7

[0205] This embodiment provides a tantalum gradient-doped lithium-rich manganese-based precursor, wherein the molar fraction of the tantalum element in the outermost coating layer is 5%, divided by the total molar amount of the outermost coating layer.

[0206] That is, in step (2) of the method for preparing the lithium-rich manganese-based precursor, during the second coprecipitation reaction, the molar amount of tantalum ions in the reaction solution is controlled to account for 5% of the total molar amount of metal ions in the second reaction solution, and the rest is the same as Example 1.

[0207] This embodiment further provides a positive electrode material, which is the same as that of Example 1 except that the lithium-rich manganese-based precursor in the preparation method of the positive electrode material is replaced with the lithium-rich manganese-based precursor in this embodiment in an equal molar amount.

[0208] This embodiment further provides a composite positive electrode material, wherein the positive electrode material in the positive electrode material core of the composite positive electrode material is replaced with the positive electrode material provided in this embodiment;

[0209] That is, the steps of the preparation process of the composite positive electrode material are the same as those of Example 1 except that the positive electrode material is replaced with the positive electrode material in this example.

[0210] Example 8

[0211] This embodiment provides a composite cathode material, except that the Li-TM-OSP interface buffer layer of the composite cathode material is omitted;

[0212] That is, except for omitting the steps of “then heating the intermediate material to 400°C at a heating rate of 8°C / min and keeping the temperature for 10 hours, and then heating the intermediate material to 900°C at a heating rate of 8°C / min and keeping the temperature for 6 hours in an argon atmosphere”, the rest are the same as those in Example 1.

[0213] Example 9

[0214] This embodiment provides a composite positive electrode material, except that the Li6PS5Cl layer of the composite positive electrode material is omitted;

[0215] That is, except that the magnetron sputtering of Li6PS5Cl in the preparation process of the composite positive electrode material is omitted, the rest is the same as that in Example 1.

[0216] Example 10

[0217] This embodiment also provides a composite positive electrode material, except that the Li7La3Zr2O composite positive electrode material is omitted. 12 layer;

[0218] That is, the preparation process of the composite positive electrode material is omitted. 12 Except for the magnetron sputtering, the rest are the same as in Example 1.

[0219] Example 11

[0220] This embodiment also provides a composite positive electrode material, except that the Li6PS5Cl layer and the Li7La3Zr2O 12 layer;

[0221] That is, the Li6PS5Cl and Li7La3Zr2O in the preparation process of the composite positive electrode material are omitted. 12 Except for the deposition, the rest are the same as in Example 1.

[0222] Comparative Example 1

[0223] This comparative example provides a tantalum-gradient doped lithium-rich manganese-based precursor, wherein the concentration of the tantalum element is the same except for the direction from the core to the outermost coating layer of the lithium-rich manganese-based precursor;

[0224] The molar fraction of the tantalum element in the core is 0.3%, calculated as a percentage of the total molar amount of the metal elements in the core;

[0225] The molar fraction of the tantalum element in the outermost coating layer is 0.3%, calculated as a percentage of the total molar amount of the outermost coating layer;

[0226] That is, in step (2) of the method for preparing the lithium-rich manganese-based precursor, during the second coprecipitation reaction, the molar amount of tantalum ions is controlled to be 0.3% of the total molar amount of metal ions in the second reaction solution, and the rest is the same as Example 1.

[0227] This comparative example also provides a positive electrode material, which is the same as Example 1 except that the lithium-rich manganese-based precursor in the preparation method of the positive electrode material is replaced with the lithium-rich manganese-based precursor in this comparative example in an equal molar amount.

[0228] This comparative example also provides a composite positive electrode material, except that the positive electrode material in the positive electrode material core of the composite positive electrode material is replaced with the positive electrode material provided in this comparative example;

[0229] That is, the steps of the preparation process of the composite positive electrode material are the same as those of Example 1, except that the positive electrode material is replaced with the positive electrode material in this comparative example.

[0230] Comparative Example 2

[0231] This comparative example provides a tantalum-gradient doped lithium-rich manganese-based precursor, wherein the concentration of the tantalum element is the same except for the direction from the core to the outermost coating layer of the lithium-rich manganese-based precursor;

[0232] The molar fraction of the tantalum element in the core is 1.5%, calculated as a percentage of the total molar amount of the metal elements in the core;

[0233] The molar fraction of the tantalum element in the outermost coating layer is 1.5% based on the total molar amount of the outermost coating layer;

[0234] That is, in step (1) of the method for preparing the lithium-rich manganese-based precursor, during the first coprecipitation reaction, the molar amount of tantalum ions is controlled to account for 1.5% of the total molar amount of metal ions in the first reaction solution, and the rest is the same as Example 1.

[0235] This comparative example also provides a positive electrode material, which is the same as Example 1 except that the lithium-rich manganese-based precursor in the preparation method of the positive electrode material is replaced with the lithium-rich manganese-based precursor in this comparative example in an equal molar amount.

[0236] This comparative example also provides a composite positive electrode material, except that the positive electrode material in the positive electrode material core of the composite positive electrode material is replaced with the positive electrode material provided in this comparative example;

[0237] That is, the steps of the preparation process of the composite positive electrode material are the same as those of Example 1, except that the positive electrode material is replaced with the positive electrode material in this comparative example.

[0238] Comparative Example 3

[0239] This comparative example provides a tantalum-gradient doped lithium-rich manganese-based precursor, wherein the concentration of the tantalum element decreases in sequence from the core to the outermost coating layer of the lithium-rich manganese-based precursor;

[0240] The molar fraction of the tantalum element in the core is 1.5%, calculated as a percentage of the total molar amount of the metal elements in the core;

[0241] The molar fraction of the tantalum element in the outermost coating layer is 0.3%, calculated as a percentage of the total molar amount of the outermost coating layer;

[0242] That is, in step (1) of the method for preparing the lithium-rich manganese-based precursor, the molar amount of tantalum ions is controlled to account for 1.5% of the total molar amount of metal ions in the first reaction solution; and in step (2) of the method for preparing the lithium-rich manganese-based precursor, the molar amount of tantalum ions is controlled to account for 0.3% of the total molar amount of metal ions in the second reaction solution. The rest is the same as Example 1.

[0243] This comparative example also provides a positive electrode material, which is the same as Example 1 except that the lithium-rich manganese-based precursor in the preparation method of the positive electrode material is replaced with the lithium-rich manganese-based precursor in this comparative example in an equal molar amount.

[0244] This comparative example also provides a composite positive electrode material, except that the positive electrode material in the positive electrode material core of the composite positive electrode material is replaced with the positive electrode material provided in this comparative example;

[0245] That is, the steps of the preparation process of the composite positive electrode material are the same as those of Example 1, except that the positive electrode material is replaced with the positive electrode material in this comparative example.

[0246] Comparative Example 4

[0247] This comparative example provides a tantalum gradient-doped lithium-rich manganese-based precursor, which is the same as Example 1 except that a coating layer (i.e., the outermost coating layer) covering the outer core is omitted.

[0248] This comparative example also provides a positive electrode material, which is the same as Example 1 except that the lithium-rich manganese-based precursor in the preparation method of the positive electrode material is replaced with the lithium-rich manganese-based precursor in this comparative example in an equal molar amount.

[0249] This comparative example also provides a composite positive electrode material, except that the positive electrode material in the positive electrode material core of the composite positive electrode material is replaced with the positive electrode material provided in this comparative example;

[0250] That is, the steps of the preparation process of the composite positive electrode material are the same as those of Example 1, except that the positive electrode material is replaced with the positive electrode material in this comparative example.

[0251] The positive electrode materials provided in the above embodiments and comparative examples are used to prepare positive electrode sheets. The method for preparing the positive electrode sheets is as follows: the positive electrode materials provided in the above embodiments and comparative examples are mixed with conductive carbon black and polyvinylidene fluoride in a mass ratio of 92:4:4 to obtain a mixture, and the obtained mixture is then slurried with NMP (N-methylpyrrolidone) at a liquid-solid ratio of 1:1.3; the slurry obtained after slurrying is poured on aluminum foil, and kept in a vacuum oven at 40°C for 6 hours, and then kept at 110°C for 12 hours to remove NMP to obtain a positive electrode sheet.

[0252] The obtained positive electrode sheet is then used to prepare a CR2032 button battery. The method for preparing the CR2032 button battery is as follows: using the obtained positive electrode sheet as the positive electrode, then using a metal lithium sheet as the negative electrode, using a Celgard 2400 membrane as the membrane, and using a 1 mol / L LiPF6 solution as the electrolyte, and assembling to obtain a CR2032 button battery.

[0253] Then, an electrochemical performance test was performed: the voltage range for the first discharge capacity and coulombic efficiency test was 2.0V to 4.8V, and the current density was 0.1C. The 0.1C first discharge specific capacity and coulombic efficiency of the button battery containing the positive electrode material were obtained as shown in Table 1. Then, a cycle performance test was performed, in which charge and discharge were performed at 1C for 50 cycles. The capacity retention rate of the button battery containing the positive electrode material after 50 cycles at 1C was obtained as shown in Table 1.

[0254] Table 1

[0255]

[0256]

[0257] The composite positive electrode material provided in the above embodiments and comparative examples is used to prepare a positive electrode sheet. The method for preparing the positive electrode sheet is as follows: the composite positive electrode material provided in the above embodiments and comparative examples is mixed with conductive carbon black and polyvinylidene fluoride in a mass ratio of 92:4:4 to obtain a mixture, and the obtained mixture is then slurried with NMP (N-methylpyrrolidone) at a liquid-solid ratio of 1:1.3; the slurry obtained after slurrying is poured on aluminum foil, and the mixture is kept warm at 40°C in a vacuum oven for 6 hours, and then kept warm at 110°C for 12 hours to remove NMP to obtain a positive electrode sheet.

[0258] The obtained positive electrode sheet is then used to prepare a CR2032 button battery. The method for preparing the CR2032 button battery is as follows: using the obtained positive electrode sheet as the positive electrode, then using a metal lithium sheet as the negative electrode, using a Celgard 2400 membrane as the membrane, and using a 1 mol / L LiPF6 solution as the electrolyte, and assembling to obtain a CR2032 button battery.

[0259] Then, the electrochemical performance test was carried out: the voltage range for the first discharge capacity and coulombic efficiency test was 2.0V to 4.8V, the current density was 0.1C, and the 0.1C first discharge specific capacity and coulombic efficiency of the button battery containing the composite positive electrode material were obtained as shown in Table 2; then, the cycle performance test was carried out, charging and discharging were carried out at 1C, and the number of cycles was 50. The capacity retention rate of the button battery containing the composite positive electrode material after 50 cycles at 1C was obtained as shown in Table 2.

[0260] Table 2

[0261]

[0262]

[0263] From Table 1 and Table 2, we can get:

[0264] (1) After the positive electrode materials and composite positive electrode materials were prepared using the tantalum gradient-doped lithium-rich manganese-based precursors provided in Examples 1 to 4, the batteries prepared using the positive electrode materials and the composite positive electrode materials showed high first discharge capacity, high coulombic efficiency and high cycle stability;

[0265] By comparing Example 1 with Example 4, it can be seen that in the present invention, when the coating layer of the core is higher than one layer and the concentration of tantalum increases successively from the core to the outermost coating layer of the lithium-rich manganese-based precursor, the battery prepared with the lithium-rich manganese-based precursor exhibits better performance;

[0266] (2) By comparing Example 1 with Examples 5 and 6, it can be seen that in the present invention, when the porosity increases successively from the core of the lithium-rich manganese-based precursor to the outermost coating layer, it is beneficial to improve the performance of the battery prepared with the lithium-rich manganese-based precursor;

[0267] In the present invention, the porosity increases successively from the core of the lithium-rich manganese-based precursor to the outermost coating layer, forming a "tight inside and loose outside" structure; the interior is dense, improving the volume energy density; the exterior is porous, increasing the contact area between the positive electrode material prepared with the lithium-rich manganese-based precursor and the electrolyte;

[0268] (3) By comparing Example 1 with Example 7, it can be seen that when the molar fraction of tantalum in the outermost coating layer is 0.1% to 3% based on the total molar amount of metal elements in the outermost coating layer, it is beneficial to improve the performance of the battery prepared with the lithium-rich manganese-based precursor; the appropriate amount of tantalum doping can stabilize the crystal structure, inhibit oxygen loss and phase change during the charge and discharge process, and reduce voltage decay; in addition, the appropriate amount of tantalum doping can inhibit cation mixing, and high-valent tantalum can anchor the transition metal layer and reduce the degree of mixing between lithium ions and transition metal ions; however, excessive doping of tantalum will lead to a decrease in the specific capacity of the positive electrode material, while aggravating lattice distortion, inducing structural stress and even crack generation, thereby causing the battery's cycle performance to deteriorate;

[0269] (4) By comparing Example 1 with Example 8, it can be seen that the interface buffer layer in the composite positive electrode material of the present invention can block the transition metal (such as Mn) in the core of the positive electrode material. 3+) to the electrolyte, while preventing S or O in the electrolyte from diffusing back to the positive electrode, thereby reducing the risk of phase change and capacity decay of the composite positive electrode material and improving the electrochemical performance of the battery prepared with the composite positive electrode material;

[0270] (5) By comparing Example 1 with Examples 9 to 11, it can be seen that in the present invention, the ionic conductivity enhancement layer in the composite positive electrode material can enhance the provision of ultra-high ionic conductivity and improve the rate performance of the battery; and in conjunction with the interface layer in the composite positive electrode material, the stability of the interface layer is utilized to prevent the negative electrode material from having harmful side reactions (such as reduction decomposition) with the inner layer sulfide, thereby stabilizing the interface of the composite positive electrode material, reducing the interface impedance, and improving the cycle life of the battery prepared with the composite positive electrode material;

[0271] (6) By comparing Example 1 with Comparative Examples 1 to 4, it can be seen that in the tantalum gradient-doped lithium-rich manganese-based precursor provided by the present invention, and along the direction from the core of the lithium-rich manganese-based precursor to the outermost coating layer, the concentration of tantalum element increases successively, and the enrichment of tantalum element in the outermost coating layer is achieved (the tantalum element content in the outermost coating layer is the highest), which not only inhibits the loss of lattice oxygen and structural phase change, but also avoids the structural instability problem caused by the excessive fineness of the primary grains of the outermost coating layer, thereby inhibiting the phase change and voltage attenuation during the battery cycle, and improving the capacity, first coulombic efficiency and cycle stability of the battery prepared with the lithium-rich manganese-based precursor.

[0272] The above description is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily thought of by those skilled in the art within the technical scope disclosed by the present invention fall within the protection scope and disclosure scope of the present invention.

Claims

1. A tantalum gradient-doped lithium-rich manganese-based precursor, characterized in that: The lithium-rich manganese-based precursor includes a core and at least one coating layer sequentially coated on the outside of the core; The core and all the coating layers contain tantalum elements, and the concentration of the tantalum elements increases along the direction from the core of the lithium-rich manganese-based precursor to the outermost coating layer.

2. The lithium-rich manganese-based precursor according to claim 1, characterized in that The porosity increases in sequence from the core of the lithium-rich manganese-based precursor to the outermost coating layer; Preferably, the porosity of the inner core is 4.1% to 9.6%; Preferably, the porosity of the outermost coating layer is 13.5% to 17%; Preferably, the molar fraction of the tantalum element in the core is 0.1% to 0.5% based on the total molar amount of the metal elements in the core; Preferably, the molar fraction of the tantalum element in the outermost coating layer is 0.1% to 3% based on the total molar amount of the metal elements in the outermost coating layer. Preferably, the D50 particle size of the core is 2 μm to 4 μm; Preferably, the thickness of the outermost coating layer is 0.1 μm to 0.8 μm; Preferably, the lithium-rich manganese-based precursor comprises a core and a coating layer covering the core; Preferably, the lithium-rich manganese-based precursor further includes a main element manganese and an auxiliary element, and the auxiliary element includes any one of nickel, cobalt, chromium or iron, or a combination of at least two of them.

3. A method for preparing the lithium-rich manganese-based precursor according to claim 1 or 2, characterized in that: The preparation method comprises: (1) adding a metal mixed salt solution, a precipitant solution, a complexing agent solution, and a tantalum salt solution to a reaction base solution to form a reaction solution, and performing a coprecipitation reaction to obtain a solution containing a precipitate; (2) adding a metal mixed salt solution, a precipitant solution, a complexing agent solution, and a tantalum salt solution to the solution containing the precipitate obtained in the previous step to form a reaction solution, performing a coprecipitation reaction, and controlling the tantalum ion concentration in the reaction solution to be higher than the tantalum ion concentration in the reaction solution in the previous step to obtain a solution containing the precipitate; (3) If only a lithium-rich manganese-based precursor comprising one coating layer is prepared, a lithium-rich manganese-based precursor is obtained after step (2); if a lithium-rich manganese-based precursor comprising at least two coating layers is prepared, step (2) is repeated at least once to obtain a lithium-rich manganese-based precursor.

4. The preparation method according to claim 3, characterized in that During the coprecipitation reaction in step (2), the pH of the reaction solution is controlled to be lower than the pH of the reaction solution in the previous step; Preferably, in step (1), the pH of the reaction solution is controlled to be 10 to 11.5; Preferably, in step (2), the pH of the reaction solution is controlled to be 9 to 10; Preferably, the temperature of the reaction solution in step (1) and step (2) is independently controlled to be 40° C. to 55° C.; Preferably, in step (1), the molar amount of tantalum ions in the reaction solution is controlled to be 0.1% to 0.5% of the total molar amount of metal ions in the reaction solution; Preferably, in step (2), the molar amount of tantalum ions in the coprecipitation reaction is controlled to be 0.1% to 3% of the total molar amount of metal ions in the reaction solution; Preferably, the co-precipitation reaction in step (1) and step (2) is carried out while stirring at a rotation speed of 80 rpm to 250 rpm.

5. A positive electrode material, characterized in that The positive electrode material is prepared from raw materials comprising the lithium-rich manganese-based precursor according to claim 1 or 2.

6. A composite positive electrode material, characterized in that The composite positive electrode material includes a positive electrode material core, and an interface buffer layer, an ion conductivity enhancement layer and an interface layer sequentially coated on the outside of the positive electrode material core; the positive electrode material in the positive electrode material core includes the positive electrode material according to claim 5.

7. The composite cathode material according to claim 6, characterized in that The interface buffer layer includes a Li-TM-OSP interface buffer layer; wherein TM includes a main element manganese and an auxiliary element; Preferably, the thickness of the interface buffer layer is 100 nm to 200 nm; Preferably, the material of the ionic conductivity enhancing layer includes any one or a combination of at least two of a sulfide solid electrolyte, a halide electrolyte, sodium fluoroniobate or lithium oxychloride; Preferably, the thickness of the ionic conductivity enhancing layer is 180 nm to 300 nm; Preferably, the material of the interface layer includes LLZO and / or LAGP; Preferably, the thickness of the interface layer is 50 nm to 100 nm.

8. A process for preparing the composite positive electrode material according to claim 6 or 7, characterized in that: The preparation process comprises: On the surface of the positive electrode material according to claim 5, an ion conductivity enhancing material and an interface material are sequentially deposited, and then heat treated to obtain a composite positive electrode material.

9. The preparation process according to claim 8, characterized in that: After the deposition, the mass ratio of the positive electrode material to the ion conductivity enhancing material is (8-6):(1-3); Preferably, after the deposition, the mass ratio of the ionic conductivity enhancing material to the interface material is (1-3):1; Preferably, the heat treatment comprises sequentially performing a first heating step, a first heat preservation step, a second heating step, and a second heat preservation step in a protective atmosphere; Preferably, the temperature of the first insulation is 300-500° C., and the time is 8-12 hours; Preferably, the temperature of the second insulation is 850° C. to 900° C., and the time is 4 hours to 6 hours.

10. A solid-state battery, characterized in that: The solid-state battery comprises the positive electrode material according to claim 5 and / or the composite positive electrode material according to claim 6 or 7.

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