Ternary precursor of core-shell structure, and preparation method therefor and use thereof

Abstract

The present application provides a ternary precursor of a core-shell structure, and a preparation method therefor and a use thereof. The preparation method for the ternary precursor comprises the following steps: introducing, in a concurrent flow, a ternary mixed salt solution, a precipitant solution and a complexing agent solution into a base solution, and carrying out a coprecipitation reaction until a target particle size, so as to obtain the ternary precursor of a core-shell structure, wherein the base solution comprises a metal-doped molecular sieve material. The ternary precursor of the core-shell structure obtained by the preparation method provided in the present application has a nickel-rich core and a manganese-rich shell, and a positive electrode material prepared from the ternary precursor has good rate performance and cycle performance and high initial specific capacity. In addition, the preparation method provided in the present application involves simple process steps, and does not need complex steps such as secondary sintering or secondary coating, thereby facilitating industrial popularization.

Description

A core-shell structure ternary precursor and its preparation method and application Technical Field

[0001] The present application belongs to the field of battery technology and relates to a ternary precursor and a preparation method thereof, and in particular to a core-shell structure ternary precursor and a preparation method and application thereof. Background Art

[0002] Nickel-rich layered material LiNi 1-x-y Mn x Co y O2 and LiNi 0.8 Co 0.15 Al 0.05 O2 is considered to be the most promising candidate for positive electrode material, with a capacity of 200mAh / g and a high voltage of 3.8V. + / Ni 2+ Problems such as cation mixing, Li residue, poor thermal stability and pulverization affect the cycle performance and rate performance of the battery.

[0003] Currently, methods to improve the cycle performance and rate performance of batteries corresponding to nickel-rich layered materials include element doping, surface coating and formation of concentration gradients.

[0004] Element doping can significantly improve the cycling stability of cathode materials, but it also leads to capacity degradation. While surface coatings can isolate the active material from the electrolyte by applying a protective layer to the secondary ions, they cannot prevent intergranular cracking within the primary particles caused by frequent volume changes during electrochemical cycling. Concentration gradient methods are cumbersome and unsuitable for large-scale production.

[0005] In view of the problems existing in the prior art, it is necessary to provide a core-shell structured ternary precursor that is simple to prepare and has excellent electrochemical properties, as well as a preparation method and application thereof.

[0006] Summary of the Invention

[0007] The following is a summary of the subject matter described in detail herein. This summary is not intended to limit the scope of the claims.

[0008] In response to the shortcomings of the existing technology, the purpose of this application is to provide a core-shell structure ternary precursor and its preparation method and application. The elements in the core-shell structure ternary precursor are evenly distributed, and the corresponding positive electrode material has good rate performance, cycle performance and high initial specific capacity.

[0009] To achieve this goal, this application adopts the following technical solutions:

[0010] In a first aspect, the present application provides a method for preparing a core-shell structured ternary precursor, the preparation method comprising the following steps:

[0011] A ternary mixed salt solution, a precipitant solution, and a complexing agent solution are introduced into the base liquid in parallel to perform a co-precipitation reaction to a target particle size, thereby obtaining the core-shell structure ternary precursor;

[0012] The bottom liquid includes metal-doped molecular sieve material.

[0013] The preparation method provided in the present application uses metal-doped molecular sieve materials in the base liquid, so that the resulting core-shell structured ternary precursor has a nickel-rich core and a manganese-rich shell. The positive electrode material prepared therefrom has good rate performance, cycle performance and a high initial specific capacity. Moreover, the preparation method provided in the present application has simple process steps and does not require more complicated steps such as secondary sintering or secondary coating, which is convenient for industrial promotion.

[0014] As an optional technical solution, the metal-doped molecular sieve material is metal-doped ZIF-8. By using metal-doped ZIF-8, the resulting core-shell structured ternary precursor has a nickel-rich core and a manganese-rich shell. The cathode material prepared therefrom has good rate performance, cycle performance, and a high initial specific capacity.

[0015] In one embodiment, the metal-doped molecular sieve material is prepared by the following steps: mixing a first solution and a second solution, performing solid-liquid separation after the reaction, and drying to obtain the metal-doped molecular sieve material;

[0016] The first solution is a NH4OH solution of 2-methylimidazole;

[0017] The second solution is a mixed aqueous solution of nickel salt and doping metal salt.

[0018] In one embodiment, the volume ratio of the first solution to the second solution is 1:(16-20).

[0019] In one embodiment, the content of NH3 in the first solution is 25-40 wt%.

[0020] In one embodiment, the concentration of 2-methylimidazole in the first solution is 1.9-3.8 mol / L.

[0021] In one embodiment, the concentration of the nickel salt in the second solution is 0.6-1.2 mol / L.

[0022] In one embodiment, the concentration of the doping metal salt in the second solution is 0.007-0.014 mol / L.

[0023] In one embodiment, the metal element in the doping metal salt includes any one or a combination of at least two of zirconium, titanium, magnesium, aluminum, copper or calcium.

[0024] In one embodiment, the temperature of the base liquid is 20-80°C.

[0025] In one embodiment, the concentration of aqueous ammonia in the base solution is 0-10 g / L, and can further be 5-8 g / L.

[0026] In one embodiment, the pH value of the base solution is 8-12.

[0027] In one embodiment, the concentration of the metal-doped molecular sieve material in the bottom solution is 4-6 g / L.

[0028] In one embodiment, the concentration of the ternary mixed salt solution is 80-120 g / L.

[0029] In one embodiment, the metal salts in the ternary mixed salt solution include nickel salt, cobalt salt and manganese salt.

[0030] In one embodiment, in the ternary mixed salt solution, the molar ratio of nickel element, cobalt element and manganese element is (4-6):(1-3):(2-4).

[0031] In one embodiment, the mass concentration of the precipitant solution is 10-30 wt%.

[0032] In one embodiment, the precipitant in the precipitant solution comprises sodium hydroxide and / or potassium hydroxide.

[0033] In one embodiment, the mass concentration of the complexing agent solution is 10-20 wt%.

[0034] In one embodiment, the complexing agent solution comprises aqueous ammonia.

[0035] In one embodiment, the coprecipitation reaction temperature is 20-80°C.

[0036] In one embodiment, the pH value of the coprecipitation reaction is 8-12.5.

[0037] In one embodiment, the concentration of aqueous ammonia during the coprecipitation reaction is 0-13 g / L, and can further be 5-8 g / L.

[0038] In one embodiment, the coprecipitation reaction is carried out under stirring conditions, and the stirring speed is 100-400 r / min.

[0039] In one embodiment, the target particle size is a particle size D50 of 1-50 μm, and can further be 8-15 μm.

[0040] In a second aspect, the present application provides a core-shell structure ternary precursor, which is prepared by the preparation method described in the first aspect.

[0041] In a third aspect, the present application provides a method for preparing a positive electrode material, the method comprising the following steps:

[0042] The positive electrode material is obtained by mixing a lithium source with the core-shell structure ternary precursor described in the second aspect and sintering the mixture in an oxygen atmosphere.

[0043] In a fourth aspect, the present application provides a positive electrode material, which is obtained by the preparation method described in the third aspect.

[0044] The numerical range described in this application 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, this application no longer exhaustively lists the specific point values ​​included in the range.

[0045] Compared with the prior art, the present invention has the following advantages:

[0046] The preparation method provided in the present application uses metal-doped molecular sieve materials in the base liquid to uniformly distribute the elements in the obtained core-shell structured ternary precursor, so that the positive electrode material prepared therefrom has good rate performance, cycle performance and a high initial specific capacity; moreover, the preparation method provided in the present application has simple process steps and does not require more complicated steps such as secondary sintering or secondary coating, which is convenient for industrial promotion.

[0047] Still other aspects will become apparent upon reading and understanding the detailed description. DETAILED DESCRIPTION

[0048] The technical solution of this application is further explained below through specific implementation methods.

[0049] The present invention provides a method for preparing a core-shell structure ternary precursor, which comprises the following steps:

[0050] A ternary mixed salt solution, a precipitant solution, and a complexing agent solution are introduced into the base liquid in parallel to perform a co-precipitation reaction to a target particle size, thereby obtaining the core-shell structure ternary precursor;

[0051] The bottom liquid includes metal-doped molecular sieve material.

[0052] The preparation method provided in the present application uses metal-doped molecular sieve materials in the base liquid, so that the resulting core-shell structured ternary precursor has a nickel-rich core and a manganese-rich shell. The positive electrode material prepared therefrom has good rate performance, cycle performance and a high initial specific capacity. Moreover, the preparation method provided in the present application has simple process steps and does not require more complicated steps such as secondary sintering or secondary coating, which is convenient for industrial promotion.

[0053] As an optional technical solution, the metal-doped molecular sieve material is metal-doped ZIF-8. By using metal-doped ZIF-8, the resulting core-shell structured ternary precursor has a nickel-rich core and a manganese-rich shell. The cathode material prepared therefrom has good rate performance, cycle performance, and a high initial specific capacity.

[0054] In certain embodiments, the metal-doped molecular sieve material is prepared by the following steps: mixing a first solution and a second solution, performing solid-liquid separation after the reaction, and drying to obtain the metal-doped molecular sieve material;

[0055] The first solution is a NH4OH solution of 2-methylimidazole;

[0056] The second solution is a mixed aqueous solution of nickel salt and doping metal salt.

[0057] As a further optional technical solution, the reaction temperature after mixing the first solution and the second solution is 20-30°C, and the time is more than 24 hours. In order to improve the preparation efficiency, the reaction is carried out under stirring conditions. This application does not specifically limit the stirring conditions, as long as the first solution and the second solution can be evenly mixed.

[0058] In certain embodiments, the volume ratio of the first solution to the second solution is 1:(16-20), for example, 1:16, 1:17, 1:18, 1:19 or 1:20, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0059] In certain embodiments, the NH3 content in the first solution is 25-40wt%, for example, 25wt%, 30wt%, 32wt%, 35wt% or 40wt%, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0060] In certain embodiments, the concentration of 2-methylimidazole in the first solution is 1.9-3.8 mol / L, for example, 1.9 mol / L, 2.5 mol / L, 2.8 mol / L, 3 mol / L, 3.5 mol / L or 3.8 mol / L, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0061] In some embodiments, the concentration of the nickel salt in the second solution is 0.6-1.2 mol / L, for example, 0.6 mol / L, 0.8 mol / L, 1 mol / L or 1.2 mol / L, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0062] In the present application, the nickel salt in the second solution includes but is not limited to nickel nitrate.

[0063] In some embodiments, the concentration of the doped metal salt in the second solution is 0.007-0.014 mol / L, for example, it can be 0.007 mol / L, 0.008 mol / L, 0.01 mol / L, 0.012 mol / L or 0.014 mol / L, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0064] In certain embodiments, the metal element in the doping metal salt includes any one or a combination of at least two of zirconium, titanium, magnesium, aluminum, copper or calcium. Typical but non-limiting combinations include a combination of zirconium and titanium, a combination of magnesium and aluminum, a combination of copper and calcium, a combination of zirconium, titanium and magnesium, a combination of aluminum, copper and calcium, or a combination of zirconium, titanium, magnesium, aluminum, copper and calcium.

[0065] In the present application, the metal salt in the doped metal salt includes but is not limited to nitrate.

[0066] In some embodiments, the temperature of the base liquid is 20-80°C, for example, it can be 20°C, 30°C, 40°C, 50°C, 60°C, 70°C or 80°C, but is not limited to the listed values. Other values ​​not listed within the numerical range are also applicable.

[0067] In some embodiments, the ammonia concentration in the base liquid is 0-10 g / L, for example, it can be 0 g / L, 1 g / L, 3 g / L, 5 g / L, 7 g / L, 8 g / L or 10 g / L, but is not limited to the listed values. Other unlisted values ​​within the numerical range are also applicable, and can further be selected as 5-8 g / L.

[0068] In some embodiments, the pH value of the base solution is 8-12, for example, 8, 9, 10, 11 or 12, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0069] Illustratively, the pH value of the base liquid described in the present application is adjusted by ammonia water and sodium hydroxide in the base liquid. However, when the ammonia water in the base liquid cannot make the pH value reach the process value, sodium hydroxide is added to adjust the pH value of the base liquid.

[0070] In some embodiments, the concentration of the metal-doped molecular sieve material in the base liquid is 4-6 g / L, for example, it can be 4 g / L, 4.5 g / L, 5 g / L, 5.5 g / L or 6 g / L, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0071] In some embodiments, the concentration of the ternary mixed salt solution is 80-120 g / L, for example, 80 g / L, 90 g / L, 100 g / L, 110 g / L or 120 g / L, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0072] In certain embodiments, the metal salts in the ternary mixed salt solution include nickel salt, cobalt salt, and manganese salt.

[0073] For example, the nickel salt includes but is not limited to nickel nitrate; the cobalt salt includes but is not limited to cobalt nitrate; and the manganese salt includes but is not limited to manganese nitrate.

[0074] In some embodiments, in the ternary mixed salt solution, the molar ratio of nickel element, cobalt element and manganese element is (4-6):(1-3):(2-4), for example, it can be any one of 5:2:3, 4:3:3, 6:1:3, 5:1:4 or 5:3:2, or a combination of at least two of them.

[0075] In some embodiments, the mass concentration of the precipitant solution is 10-30wt%, for example, it can be 10wt%, 15wt%, 20wt%, 25wt% or 30wt%, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0076] In certain embodiments, the precipitant in the precipitant solution comprises sodium hydroxide and / or potassium hydroxide.

[0077] In some embodiments, the mass concentration of the complexing agent solution is 10-20wt%, for example, it can be 10wt%, 12wt%, 15wt%, 16wt%, 18wt% or 20wt%, but is not limited to the listed values. Other values ​​not listed within the numerical range are also applicable.

[0078] In certain embodiments, the complexing agent solution includes aqueous ammonia.

[0079] In certain embodiments, the temperature of the coprecipitation reaction is 20-80°C, for example, 20°C, 30°C, 40°C, 50°C, 60°C, 70°C or 80°C, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0080] In certain embodiments, the pH value of the coprecipitation reaction is 8-12.5, for example, 8, 9, 10, 11, 12 or 12.5, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0081] This application does not impose any specific restrictions on the flow rate of the ternary mixed salt solution during the coprecipitation reaction. It only needs to coordinate the flow rate of the ternary mixed salt solution with the complexing agent solution and the precipitant solution to meet the pH value of 8-12.5 during the coprecipitation reaction.

[0082] Exemplarily, the flow rate of the ternary mixed salt solution is 1-10 L / h, for example, 1 L / h, 3 L / h, 5 L / h, 8 L / h or 10 L / h, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0083] In certain embodiments, the concentration of aqueous ammonia during the coprecipitation reaction is 0-13 g / L, for example, 0 g / L, 2 g / L, 5 g / L, 8 g / L, 10 g / L or 13 g / L, but is not limited to the listed values. Other unlisted values ​​within the numerical range are also applicable, and can further be selected from 5-8 g / L.

[0084] In certain embodiments, the coprecipitation reaction is carried out under stirring conditions, and the stirring speed is 100-400 r / min, for example, it can be 100 r / min, 200 r / min, 300 r / min or 400 r / min, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0085] In some embodiments, the target particle size is a particle size D50 of 1-50 μm, for example, 1 μm, 5 μm, 10 μm, 20 μm, 30 μm, 40 μm or 50 μm, but is not limited to the listed values. Other unlisted values ​​within the numerical range are also applicable, and can further be selected as 8-15 μm.

[0086] The embodiment of the present application provides a core-shell structure ternary precursor.

[0087] The present invention provides a method for preparing a positive electrode material, which comprises the following steps:

[0088] The lithium source and the core-shell structure ternary precursor are mixed and sintered in an oxygen atmosphere to obtain the positive electrode material.

[0089] The lithium source described in this application includes but is not limited to lithium hydroxide.

[0090] The gas used in the oxygen atmosphere described in this application includes but is not limited to air.

[0091] The sintering temperature described in this application is 600-800°C, for example, it can be 600°C, 650°C, 700°C, 750°C or 800°C, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0092] The sintering time described in this application is 6-15 hours, for example, it can be 6 hours, 9 hours, 10 hours, 12 hours or 15 hours, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0093] The embodiment of the present application also provides a positive electrode material.

[0094] Example 1

[0095] This embodiment provides a method for preparing a core-shell structure ternary precursor, the preparation method comprising the following steps:

[0096] A ternary mixed salt solution, a precipitant solution, and a complexing agent solution are added in parallel to a base solution at 50° C., with an ammonia concentration of 6 g / L and a pH of 10, and a co-precipitation reaction is carried out at 50° C. until the particle size D50 reaches 12 μm, thereby obtaining the core-shell structure ternary precursor;

[0097] The base solution includes metal-doped molecular sieve material at a concentration of 5 g / L;

[0098] The metal-doped molecular sieve material is prepared by the following steps: mixing the first solution and the second solution in a volume ratio of 1:18, performing solid-liquid separation after the reaction, and drying to obtain the metal-doped molecular sieve material;

[0099] The first solution is a 2-methylimidazole NH4OH solution; the NH3 content in the first solution is 32wt%, and the concentration of 2-methylimidazole is 3mol / L;

[0100] The second solution is a mixed aqueous solution of nickel nitrate and zirconium nitrate; the concentration of nickel nitrate in the second solution is 1 mol / L, and the concentration of zirconium nitrate is 0.01 mol / L.

[0101] The concentration of the ternary mixed salt solution is 100 g / L, the precipitant solution is a sodium hydroxide solution with a mass concentration of 20 wt%, and the complexing agent solution is ammonia water with a mass concentration of 15 wt%;

[0102] The metal salts in the ternary mixed salt solution are nickel nitrate, cobalt nitrate and manganese nitrate, and the molar ratio of nickel element, cobalt element and manganese element is 5:2:3;

[0103] During the coprecipitation reaction, the pH value was maintained at 10 and the ammonia concentration was maintained at 6 g / L by controlling the flow rate of the precipitant solution; the coprecipitation reaction was carried out under stirring conditions, and the stirring speed was 200 r / min;

[0104] During the coprecipitation reaction, a high-efficiency concentrator is used to collect all the particles before the particle size reaches the requirement and return them to the reaction device until the particle size D50 reaches 12μm.

[0105] Example 2

[0106] This embodiment provides a method for preparing a core-shell structure ternary precursor, the preparation method comprising the following steps:

[0107] A ternary mixed salt solution, a precipitant solution, and a complexing agent solution are introduced into a base solution at 20° C., with an ammonia concentration of 8 g / L and a pH of 12, and a coprecipitation reaction is carried out at 20° C. until the particle size D50 is 12 μm, thereby obtaining the core-shell structure ternary precursor;

[0108] The base solution includes metal-doped molecular sieve material at a concentration of 4 g / L;

[0109] The metal-doped molecular sieve material is prepared by the following steps: mixing the first solution and the second solution in a volume ratio of 1:16, performing solid-liquid separation after the reaction, and drying to obtain the metal-doped molecular sieve material;

[0110] The first solution is a 2-methylimidazole NH4OH solution; the NH3 content in the first solution is 25wt%, and the concentration of 2-methylimidazole is 1.9mol / L;

[0111] The second solution is a mixed aqueous solution of nickel nitrate and zirconium nitrate; the concentration of nickel nitrate in the second solution is 0.6 mol / L, and the concentration of zirconium nitrate is 0.007 mol / L.

[0112] The concentration of the ternary mixed salt solution is 80 g / L, the precipitant solution is a sodium hydroxide solution with a mass concentration of 20 wt%, and the complexing agent solution is an ammonia solution with a mass concentration of 10 wt%;

[0113] The metal salts in the ternary mixed salt solution are nickel nitrate, cobalt nitrate and manganese nitrate, and the molar ratio of nickel element, cobalt element and manganese element is 5:2:3;

[0114] During the coprecipitation reaction, the pH value was maintained at 12 and the ammonia concentration was maintained at 8 g / L by controlling the flow rate of the precipitant solution; the coprecipitation reaction was carried out under stirring conditions, and the stirring speed was 100 r / min;

[0115] During the coprecipitation reaction, a high-efficiency concentrator is used to collect all the particles before the particle size reaches the requirement and return them to the reaction device until the particle size D50 reaches 12μm.

[0116] Example 3

[0117] This embodiment provides a method for preparing a core-shell structure ternary precursor, the preparation method comprising the following steps:

[0118] A ternary mixed salt solution, a precipitant solution, and a complexing agent solution are introduced into a base solution at 80° C., with an ammonia concentration of 5 g / L and a pH value of 8, and a coprecipitation reaction is carried out at 80° C. until the particle size D50 is 12 μm, thereby obtaining the core-shell structure ternary precursor;

[0119] The base solution includes metal-doped molecular sieve material at a concentration of 6 g / L;

[0120] The metal-doped molecular sieve material is prepared by the following steps: mixing the first solution and the second solution in a volume ratio of 1:20, performing solid-liquid separation after the reaction, and drying to obtain the metal-doped molecular sieve material;

[0121] The first solution is a 2-methylimidazole NH4OH solution; the NH3 content in the first solution is 40wt%, and the concentration of 2-methylimidazole is 3.8mol / L;

[0122] The second solution is a mixed aqueous solution of nickel nitrate and zirconium nitrate; the concentration of nickel nitrate in the second solution is 1.2 mol / L, and the concentration of zirconium nitrate is 0.014 mol / L.

[0123] The concentration of the ternary mixed salt solution is 120 g / L, the precipitant solution is a sodium hydroxide solution with a mass concentration of 30 wt%, and the complexing agent solution is an ammonia solution with a mass concentration of 20 wt%;

[0124] The metal salts in the ternary mixed salt solution are nickel nitrate, cobalt nitrate and manganese nitrate, and the molar ratio of nickel element, cobalt element and manganese element is 5:2:3;

[0125] During the coprecipitation reaction, the pH value was maintained at 8 and the ammonia concentration was maintained at 5 g / L by controlling the flow rate of the precipitant solution; the coprecipitation reaction was carried out under stirring conditions at a speed of 400 r / min;

[0126] During the co-precipitation reaction, a high-efficiency concentrator is used to collect all the particles before the particle size reaches the requirement and return them to the reaction device until the particle size D50 reaches 12μm.

[0127] Example 4

[0128] This embodiment provides a method for preparing a core-shell structure ternary precursor, the preparation method comprising the following steps:

[0129] A ternary mixed salt solution, a precipitant solution, and a complexing agent solution are introduced into a base solution at 50° C., with an ammonia concentration of 6 g / L and a pH value of 10, and a coprecipitation reaction is carried out at 50° C. until the particle size D50 is 12 μm, thereby obtaining the core-shell structure ternary precursor;

[0130] The base solution includes metal-doped molecular sieve material at a concentration of 5 g / L;

[0131] The metal-doped molecular sieve material is prepared by the following steps: mixing the first solution and the second solution in a volume ratio of 1:18, performing solid-liquid separation after the reaction, and drying to obtain the metal-doped molecular sieve material;

[0132] The first solution is a 2-methylimidazole NH4OH solution; the NH3 content in the first solution is 32wt%, and the concentration of 2-methylimidazole is 3mol / L;

[0133] The second solution is a mixed aqueous solution of nickel nitrate and magnesium nitrate; the concentration of nickel nitrate in the second solution is 1 mol / L, and the concentration of magnesium nitrate is 0.01 mol / L.

[0134] The concentration of the ternary mixed salt solution is 100 g / L, the precipitant solution is a sodium hydroxide solution with a mass concentration of 20 wt%, and the complexing agent solution is ammonia water with a mass concentration of 15 wt%;

[0135] The metal salts in the ternary mixed salt solution are nickel nitrate, cobalt nitrate and manganese nitrate, and the molar ratio of nickel element, cobalt element and manganese element is 5:2:3;

[0136] During the coprecipitation reaction, the pH value was maintained at 10 and the ammonia concentration was maintained at 6 g / L by controlling the flow rate of the precipitant solution; the coprecipitation reaction was carried out under stirring conditions, and the stirring speed was 200 r / min;

[0137] During the coprecipitation reaction, a high-efficiency concentrator is used to collect all the particles before the particle size reaches the requirement and return them to the reaction device until the particle size D50 reaches 12μm.

[0138] Example 5

[0139] This embodiment provides a method for preparing a core-shell structure ternary precursor, the preparation method comprising the following steps:

[0140] A ternary mixed salt solution, a precipitant solution, and a complexing agent solution are introduced into a base solution at 50° C., with an ammonia concentration of 6 g / L and a pH value of 10, and a coprecipitation reaction is carried out at 50° C. until the particle size D50 is 12 μm, thereby obtaining the core-shell structure ternary precursor;

[0141] The base solution includes metal-doped molecular sieve material at a concentration of 5 g / L;

[0142] The metal-doped molecular sieve material is prepared by the following steps: mixing the first solution and the second solution in a volume ratio of 1:18, performing solid-liquid separation after the reaction, and drying to obtain the metal-doped molecular sieve material;

[0143] The first solution is a 2-methylimidazole NH4OH solution; the NH3 content in the first solution is 32wt%, and the concentration of 2-methylimidazole is 3mol / L;

[0144] The second solution is a mixed aqueous solution of nickel nitrate and copper nitrate; the concentration of nickel nitrate in the second solution is 1 mol / L, and the concentration of copper nitrate is 0.01 mol / L.

[0145] The concentration of the ternary mixed salt solution is 100 g / L, the precipitant solution is a sodium hydroxide solution with a mass concentration of 20 wt%, and the complexing agent solution is ammonia water with a mass concentration of 15 wt%;

[0146] The metal salts in the ternary mixed salt solution are nickel nitrate, cobalt nitrate and manganese nitrate, and the molar ratio of nickel element, cobalt element and manganese element is 5:2:3;

[0147] During the coprecipitation reaction, the pH value was maintained at 10 and the ammonia concentration was maintained at 6 g / L by controlling the flow rate of the precipitant solution; the coprecipitation reaction was carried out under stirring conditions, and the stirring speed was 200 r / min;

[0148] During the coprecipitation reaction, a high-efficiency concentrator is used to collect all the particles before the particle size reaches the requirement and return them to the reaction device until the particle size D50 reaches 12μm.

[0149] Example 6

[0150] This embodiment provides a method for preparing a core-shell structure ternary precursor, the preparation method comprising the following steps:

[0151] A ternary mixed salt solution, a precipitant solution, and a complexing agent solution are introduced into a base solution at 50° C., with an ammonia concentration of 6 g / L and a pH value of 10, and a coprecipitation reaction is carried out at 50° C. until the particle size D50 is 12 μm, thereby obtaining the core-shell structure ternary precursor;

[0152] The base solution includes metal-doped molecular sieve material at a concentration of 5 g / L;

[0153] The metal-doped molecular sieve material is prepared by the following steps: mixing the first solution and the second solution in a volume ratio of 1:18, performing solid-liquid separation after the reaction, and drying to obtain the metal-doped molecular sieve material;

[0154] The first solution is a 2-methylimidazole NH4OH solution; the NH3 content in the first solution is 32wt%, and the concentration of 2-methylimidazole is 3mol / L;

[0155] The second solution is a mixed aqueous solution of nickel nitrate, magnesium nitrate and copper nitrate; the concentration of nickel nitrate in the second solution is 1 mol / L, the concentration of magnesium nitrate is 0.005 mol / L, and the concentration of copper nitrate is 0.005 mol / L.

[0156] The concentration of the ternary mixed salt solution is 100 g / L, the precipitant solution is a sodium hydroxide solution with a mass concentration of 20 wt%, and the complexing agent solution is ammonia water with a mass concentration of 15 wt%;

[0157] The metal salts in the ternary mixed salt solution are nickel nitrate, cobalt nitrate and manganese nitrate, and the molar ratio of nickel element, cobalt element and manganese element is 5:2:3;

[0158] During the coprecipitation reaction, the pH value was maintained at 10 and the ammonia concentration was maintained at 6 g / L by controlling the flow rate of the precipitant solution; the coprecipitation reaction was carried out under stirring conditions, and the stirring speed was 200 r / min;

[0159] During the coprecipitation reaction, a high-efficiency concentrator is used to collect all the particles before the particle size reaches the requirement and return them to the reaction device until the particle size D50 reaches 12μm.

[0160] Example 7

[0161] This embodiment provides a method for preparing a core-shell structure ternary precursor, which is the same as that of Example 1 except that the concentration of zirconium nitrate in the second solution is 0.005 mol / L.

[0162] Example 8

[0163] This embodiment provides a method for preparing a core-shell structure ternary precursor, which is the same as that of Example 1 except that the concentration of zirconium nitrate in the second solution is 0.018 mol / L.

[0164] Example 9

[0165] This embodiment provides a method for preparing a core-shell structure ternary precursor, which is the same as that of Example 1 except that the concentration of nickel nitrate in the second solution is 0.4 mol / L.

[0166] Example 10

[0167] This embodiment provides a method for preparing a core-shell structure ternary precursor, which is the same as that of Example 1 except that the concentration of nickel nitrate in the second solution is 1.5 mol / L.

[0168] Comparative Example 1

[0169] This comparative example provides a method for preparing a core-shell structured ternary precursor, which is the same as Example 1 except that the metal-doped molecular sieve material is replaced with commercially available ZIF-67 (Beijing Huawei Rayke).

[0170] Comparative Example 2

[0171] This comparative example provides a method for preparing a core-shell structure ternary precursor, which comprises the following steps:

[0172] A ternary mixed salt solution, a precipitant solution, and a complexing agent solution are introduced into a base solution at 50° C., with an ammonia concentration of 6 g / L and a pH value of 10, and a coprecipitation reaction is carried out at 50° C. until the particle size D50 is 12 μm, thereby obtaining the core-shell structure ternary precursor;

[0173] The base solution includes metal-doped molecular sieve material at a concentration of 5 g / L;

[0174] The metal-doped molecular sieve material is prepared by the following steps: mixing the first solution and the second solution in a volume ratio of 1:18, performing solid-liquid separation after the reaction, and drying to obtain the metal-doped molecular sieve material;

[0175] The first solution is a 2-methylimidazole NH4OH solution; the NH3 content in the first solution is 32wt%, and the concentration of 2-methylimidazole is 3mol / L;

[0176] The second solution is an aqueous solution of nickel nitrate; the concentration of nickel nitrate in the second solution is 1 mol / L.

[0177] The concentration of the ternary mixed salt solution is 100 g / L, the precipitant solution is a sodium hydroxide solution with a mass concentration of 20 wt%, and the complexing agent solution is ammonia water with a mass concentration of 15 wt%;

[0178] The metal salts in the ternary mixed salt solution are nickel nitrate, cobalt nitrate and manganese nitrate, and the molar ratio of nickel element, cobalt element and manganese element is 5:2:3;

[0179] During the coprecipitation reaction, the pH value was maintained at 10 and the ammonia concentration was maintained at 6 g / L by controlling the flow rate of the precipitant solution; the coprecipitation reaction was carried out under stirring conditions, and the stirring speed was 200 r / min;

[0180] During the coprecipitation reaction, a high-efficiency concentrator is used to collect all the particles before the particle size reaches the requirement and return them to the reaction device until the particle size D50 reaches 12μm.

[0181] Performance Characterization

[0182] The positive electrode material was prepared using the core-shell structure ternary precursor provided in Examples 1-10 and Comparative Examples 1-2. The preparation method was as follows: LiOH·H2O and the core-shell structure ternary precursor were uniformly mixed by a high-speed mixer, and sintered in a box furnace under an air atmosphere at a sintering temperature of 700°C for 12 hours to obtain the positive electrode material; the theoretical molar ratio of LiOH·H2O to the core-shell structure ternary precursor was 1:1, and the ignition loss was supplemented according to the sintering loss.

[0183] The positive electrode material, binder polyvinylidene fluoride, and conductive agent Super P were added to N-methylpyrrolidone at a mass ratio of 97:1.5:1.5 and stirred to form a first positive electrode slurry; the first positive electrode slurry was then evenly coated on the positive electrode current collector aluminum foil, dried and roll-pressed to obtain a positive electrode sheet;

[0184] Graphite, conductive agent acetylene black, thickener CMC and binder SBR are mixed in a mass ratio of 96:1:1.5:1.5, and deionized water is added as a solvent and stirred thoroughly to obtain a negative electrode slurry; the negative electrode slurry is evenly coated on the negative electrode current collector copper foil, and the negative electrode sheet is obtained after drying, cold pressing and slitting;

[0185] Ethylene carbonate (EC), ethyl methyl carbonate (EMC), and diethyl carbonate (DEC) were mixed in a volume ratio of 1:1:1, and then fully dried lithium salt LiPF6 was dissolved in the mixed solvent to prepare an electrolyte with a concentration of 1 mol / L.

[0186] The positive electrode sheet, separator, and negative electrode sheet are stacked in sequence, then wrapped with aluminum-plastic film. After drying, the electrolyte is injected. After packaging, standing and formation processes, a lithium-ion battery is obtained. The separator is a PE porous film with a thickness of 11μm, an air permeability of 280s / 100mL, and a porosity of 40%.

[0187] After aging for 12 hours, the assembled battery was subjected to charge and discharge tests at different potentials. After activation for three cycles at a voltage of 3-4.3V and a rate of 0.1C, the battery was cycled for 200 cycles at 2C. The results are shown in Table 1.

[0188] Table 1

[0189] In summary, the preparation method provided in the present application uses metal-doped molecular sieve materials in the base liquid, so that the resulting core-shell structured ternary precursor has a nickel-rich core and a manganese-rich shell, and the positive electrode material prepared therefrom has good rate performance, cycle performance and a high initial specific capacity; moreover, the preparation method provided in the present application has simple process steps and does not require more complicated steps such as secondary sintering or secondary coating, which is convenient for industrial promotion.

[0190] The specific embodiments described above further illustrate the purpose, technical solutions and beneficial effects of this application. It should be understood that the above is only a specific embodiment of this application and is not intended to limit this application. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of this application should be included in the scope of protection of this application.

Claims

1. A method for preparing a core-shell structure ternary precursor, the preparation method comprising the following steps: A ternary mixed salt solution, a precipitant solution and a complexing agent solution are introduced into the base liquid in parallel to perform a co-precipitation reaction to a target particle size, thereby obtaining the core-shell structure ternary precursor; The base liquid includes metal-doped molecular sieve material.

2. The preparation method according to claim 1, wherein The metal-doped molecular sieve material is prepared by the following steps: mixing the first solution and the second solution, performing solid-liquid separation after the reaction is completed, and drying to obtain the metal-doped molecular sieve material; The first solution is a NH4OH solution of 2-methylimidazole; The second solution is a mixed aqueous solution of nickel salt and doped metal salt; Optionally, the volume ratio of the first solution to the second solution is 1:(16-20).

3. The preparation method according to claim 2, wherein The content of NH3 in the first solution is 25-40wt%; Optionally, the concentration of 2-methylimidazole in the first solution is 1.9-3.8 mol / L.

4. The preparation method according to claim 2 or 3, wherein The concentration of nickel salt in the second solution is 0.6-1.2 mol / L; Optionally, the concentration of the doped metal salt in the second solution is 0.007-0.014 mol / L; Optionally, the metal element in the doped metal salt includes any one of zirconium, titanium, magnesium, aluminum, copper or calcium, or a combination of at least two thereof.

5. The preparation method according to any one of claims 1 to 4, wherein: The temperature of the base liquid is 20-80°C; Optionally, the concentration of aqueous ammonia in the base solution is 0-10 g / L, and further optionally 5-8 g / L; Optionally, the pH value of the base solution is 8-12; Optionally, the concentration of the metal-doped molecular sieve material in the base solution is 4-6 g / L.

6. The preparation method according to any one of claims 1 to 5, wherein: The concentration of the ternary mixed salt solution is 80-120 g / L; Optionally, the metal salts in the ternary mixed salt solution include nickel salt, cobalt salt and manganese salt; Optionally, in the ternary mixed salt solution, the molar ratio of nickel element, cobalt element and manganese element is (4-6):(1-3):(2-4); Optionally, the concentration of the precipitant solution is 10-30wt%; Optionally, the precipitant in the precipitant solution includes sodium hydroxide and / or potassium hydroxide; Optionally, the concentration of the complexing agent solution is 10-20wt%; Optionally, the complexing agent solution comprises aqueous ammonia.

7. The preparation method according to any one of claims 1 to 6, wherein: The temperature of the coprecipitation reaction is 20-80°C; Optionally, the pH value of the coprecipitation reaction is 8-12.5; Optionally, the concentration of aqueous ammonia during the coprecipitation reaction is 0-13 g / L, and further optionally 5-8 g / L; Optionally, the coprecipitation reaction is carried out under stirring conditions, and the stirring speed is 100-400r / min; Optionally, the target particle size is a particle size D50 of 1-50 μm, and further optionally 8-15 μm.

8. A core-shell structure ternary precursor, wherein the core-shell structure ternary precursor is prepared by the preparation method according to any one of claims 1 to 7.

9. A method for preparing a positive electrode material, the method comprising the following steps: The positive electrode material is obtained by mixing a lithium source with the core-shell structure ternary precursor according to claim 8 and sintering them in an oxygen atmosphere. 10 . A positive electrode material, wherein the positive electrode material is obtained by the preparation method according to claim 9 .

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