Lithium-rich manganese-based precursor for solid-state battery, preparation method therefor and use thereof

Abstract

A lithium-rich manganese-based precursor for a solid-state battery. The chemical formula of the lithium-rich manganese-based precursor is NixMnyNbaCob(OH)2, wherein 0.25＜x≤0.4, 0.6≤y＜0.75, 0.001≤a＜0.005, 0.005≤b＜0.01, x+y+a+b=1, the content of Nb element decreases in a gradient from inside to outside, the content of Co element increases in a gradient from inside to outside, and the lithium-rich manganese-based precursor has a compact inner structure and a loose outer structure. Further provided are a preparation method for the precursor, a further obtained positive electrode material, and a solid-state battery.

Description

A lithium-rich manganese-based precursor for solid-state batteries and a preparation method and application thereof TECHNICAL FIELD

[0001] The present application relates to the technical field of solid-state batteries, in particular to a lithium-rich manganese-based precursor for solid-state batteries and a preparation method and application thereof. BACKGROUND

[0002] The lithium-rich manganese-based positive electrode material has high-voltage characteristics and can provide a higher energy density, which helps to improve the energy density of the battery and thus increase the cruising range. However, developing a 4.8V high-voltage electrolyte suitable for the lithium-rich manganese-based positive electrode material is a challenging task, which to some extent limits the performance of its high-voltage characteristics. Solid-state electrolytes can adapt to higher working voltages, and if combined with ternary positive electrode materials or lithium iron phosphate positive electrode materials, the space for improving energy density is becoming smaller and smaller. Therefore, the lithium-rich manganese-based positive electrode material is expected to become the best choice for future solid-state batteries.

[0003] In addition to the need for high capacity at high voltage, the lithium-rich manganese-based positive electrode material has several defects: 1) During the cycling process, Mn 3+ migrates into lithium vacancies, causing the layered structure to transform into a spinel structure, resulting in a continuous decrease in average discharge voltage and causing severe energy loss and posing a huge challenge to battery management; 2) poor rate performance; and 3) low material density, resulting in low volumetric energy density.

[0004] By adjusting the morphology and structure of the lithium-rich manganese-based precursor, the performance of the lithium-rich manganese-based positive electrode material can be improved. For example, CN108557905A discloses a lithium-rich manganese-based material precursor, a preparation method thereof, a lithium-rich manganese-based positive electrode material, a preparation method thereof, and a lithium battery. The lithium-rich manganese-based material precursor is a lithium-rich manganese-based material carbonate precursor with a sheet-like morphology, the particle size of the lithium-rich manganese-based material carbonate precursor with a sheet-like morphology is 1-7μm, the specific surface area is 8-50m 2 / g, and the BET pore volume is 0.1-0.5cm 2 / g. Using the lithium-rich manganese-based material precursor, a single-crystal lithium-rich manganese-based positive electrode material with a higher degree of single crystallization can be prepared with a simpler process and lower production cost, thereby improving the mechanical strength and compaction density of the microstructure of the positive electrode material, improving the capacity, the initial efficiency, and suppressing the voltage decay. However, compared with the hydroxide precursor, the positive electrode material obtained from the carbonate precursor is prone to gas production, low compaction, low strength, and easy breakage. The application reduces the impact of the carbonate precursor by burning single crystals, but single-crystal materials have poor rate performance compared to polycrystal materials, which negatively affects the lithium-rich manganese-based material which already has poor rate performance.

[0005] CN112234176A obtains fluorine and magnesium co-doped lithium-rich manganese-based precursor by double system co-precipitation method, and the lithium-rich manganese-based positive electrode material prepared from the lithium-rich manganese-based precursor can effectively improve the material crystal form stability and inhibit voltage attenuation, and the lithium ion battery prepared has good electrochemical performance. However, in addition to the negative effects of carbonate precursors, the doping of fluorine element is also a great challenge. Fluoride ions can corrode stainless steel equipment and are also easy to volatilize at high temperatures, which has very high requirements for the material quality of the production equipment of the precursor and the positive electrode material, greatly increasing the equipment investment cost.

[0006] Therefore, it is a technical problem to be solved at present to provide a lithium-rich manganese-based precursor, so that the lithium-rich manganese-based positive electrode material prepared therefrom has good cycle performance, rate performance and high energy density.

[0007] SUMMARY

[0008] 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.

[0009] The present application provides a lithium-rich manganese-based precursor for solid-state batteries and a preparation method and application thereof.

[0010] In a first aspect, the present application provides a lithium-rich manganese-based precursor for solid-state batteries, the chemical formula of the lithium-rich manganese-based precursor is Ni x Mn y Nb a Co b (OH)2, wherein 0.25

[0011] In the lithium-rich manganese-based precursor of the present application, the value range of x is 0.25

[0012] The lithium-rich manganese-based precursor of the present application has a specific gradient doping structure and an inner tight and outer loose structure. The lithium-rich manganese-based positive electrode material prepared by using the lithium-rich manganese-based precursor can inherit the gradient doping structure and the inner tight and outer loose structure characteristics of the lithium-rich manganese-based precursor. The Nb doping can improve the Li + diffusion rate and stabilize the material structure, thereby improving the rate capability and cycle performance. The Co doping can also stabilize the structure and improve the cycle performance. The inner tight structure can improve the density, thereby improving the volume energy density. The outer loose structure can increase the contact area with the solid-state electrolyte, thereby improving the rate capability.

[0013] The following is an optional technical solution of the present application, but is not a limitation on the technical solutions provided by the present application. Through the following optional technical solution, the technical purpose and beneficial effects of the present application can be better achieved and realized.

[0014] In an embodiment, the particle size D50 of the lithium-rich manganese-based precursor is 3-3.5 μm, for example, it can be 3 μm, 3.1 μm, 3.2 μm, 3.3 μm, 3.4 μm or 3.5 μm, etc. The lithium-rich manganese-based precursor has a smaller particle size, and therefore the lithium-rich manganese-based positive electrode material formed by using the lithium-rich manganese-based precursor also has a smaller particle size, which helps to improve the capacity and rate capability of the material.

[0015] As an optional technical solution of the lithium-rich manganese-based precursor described in the present application, the outer surface of the lithium-rich manganese-based precursor is coated with a coating layer, and the coating layer comprises cobalt hydroxide. The enrichment of Co on the outside can effectively reduce the residual alkali content.

[0016] In an embodiment, the thickness of the coating layer is 0.05-0.1 μm, for example, it can be 0.05 μm, 0.06 μm, 0.07 μm, 0.08 μm, 0.09 μm or 0.1 μm, etc.

[0017] In a second aspect, the present application provides a preparation method of the lithium-rich manganese-based precursor according to the first aspect, and the preparation method comprises the following steps:

[0018] The co-precipitation reaction is carried out by using a nickel-manganese salt solution, a Nb salt solution, a Co salt solution, a precipitant solution and a complexing agent solution. During the reaction process, the content of Nb element provided by the Nb salt solution and the Co salt solution is gradually reduced, and the content of Co element is gradually increased.

[0019] The method of the present application is simple and has good controllability. The element doping effect of the lithium-rich manganese-based precursor prepared by the method is controllable, and the lithium-rich manganese-based positive electrode material prepared by using the lithium-rich manganese-based precursor has good performance.

[0020] In one embodiment, the temperature of the co-precipitation reaction is 40-80°C, for example, it can be 40°C, 45°C, 50°C, 55°C, 60°C, 65°C, 70°C, 75°C or 80°C, etc.

[0021] In one embodiment, the co-precipitation reaction is carried out under the protection of a protective gas.

[0022] In one embodiment, the protective gas comprises at least one of nitrogen, helium and argon.

[0023] In one embodiment, the reaction is divided into a pre-reaction stage and a post-reaction stage, the pre-reaction stage is the stage from the formation of the precursor to the growth to the particle size D = (70%-85%) x D0, wherein D0 is the target particle size. Exemplarily, D can be 70% x D0, 72% x D0, 75% x D0, 77% x D0, 80% x D0, 82% x D0 or 84% x D0, etc.

[0024] In one embodiment, in the pre-reaction stage, the rotation speed of the co-precipitation reaction is 400-500 rpm, for example, it can be 400 rpm, 420 rpm, 440 rpm, 450 rpm, 460 rpm, 480 rpm or 500 rpm, etc.

[0025] In one embodiment, in the pre-reaction stage, the pH value of the co-precipitation reaction is 11.0-12.0, for example, it can be 11.0, 11.2, 11.3, 11.4, 11.5, 11.6, 11.8 or 12.0, etc.

[0026] In one embodiment, in the pre-reaction stage, the complexing agent is ammonia water.

[0027] In one embodiment, in the pre-reaction stage, the ammonia concentration in the reaction system is 3.0-10.0 g / L, for example, it can be 3.0 g / L, 3.4 g / L, 4 g / L, 4.5 g / L, 5 g / L, 5.5 g / L, 6 g / L, 6.5 g / L, 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, etc.

[0028] In one embodiment, in the post-reaction stage, the rotation speed of the co-precipitation reaction is 200-300 rpm, for example, it can be 200 rpm, 220 rpm, 240 rpm, 260 rpm, 280 rpm or 300 rpm, etc.

[0029] In one embodiment, in the post-reaction stage, the complexing agent is a sodium citrate solution.

[0030] In one embodiment, the concentration of sodium citrate in the reaction system in the late stage of the reaction is 0.2 g / L to 2 g / L, for example, it can be 0.2 g / L, 0.5 g / L, 1 g / L, 1.2 g / L, 1.4 g / L, 1.5 g / L, 1.7 g / L, 1.8 g / L or 2 g / L, etc.

[0031] In the preparation method of the present application, by using high rotation speed in the early stage of the reaction and ammonia as the complexing agent, and using low rotation speed in the late stage of the reaction and sodium citrate solution as the complexing agent, the structure of the lithium-rich manganese-based precursor can be adjusted, and the performance of the lithium-rich manganese-based positive electrode material prepared therefrom can be improved.

[0032] As an optional technical solution of the method described in the present application, the manner in which the content of Nb element provided by the Nb salt solution and the content of Co element provided by the Co salt solution are gradually reduced and gradually increased is as follows:

[0033] The nickel-manganese salt solution, the Nb salt solution, the Co salt solution, the precipitant solution and the complexing agent solution are added into the reaction kettle in parallel flow, wherein the amount of the Nb salt solution is fixed, and the Co salt solution is added into the Nb salt solution at a certain rate.

[0034] In one embodiment, the certain rate is 0.1 L / h to 1 L / h, for example, it can be 0.1 L / h, 0.2 L / h, 0.3 L / h, 0.4 L / h, 0.5 L / h, 0.6 L / h, 0.7 L / h, 0.8 L / h, 0.9 L / h or 1 L / h, etc.

[0035] In one embodiment, the pH values of the Nb salt solution and the Co salt solution are the same. The same pH values of the two can avoid the fluctuation of the pH value in the reaction process due to the different amounts of alkali consumed by the two.

[0036] In one embodiment, the method further comprises coating when the precursor grows to a particle size D0, and the coating method is: stopping using the Nb salt solution, and only retaining the nickel-manganese salt solution, the Co salt solution, the precipitant solution and the complexing agent solution to carry out the coprecipitation reaction.

[0037] In one embodiment, in the coating method, the pH value and the concentration of the complexing agent are stabilized by adjusting the strengths of the precipitant solution and the complexing agent solution.

[0038] In one embodiment, in the coating method, the concentration of the Co salt solution is 1 g / L to 10 g / L, for example, it can be 1 g / L, 2 g / L, 3 g / L, 4 g / L, 5 g / L, 6 g / L, 7 g / L, 8 g / L, 9 g / L or 10 g / L, etc.

[0039] The application can ensure the uniformity of the coating of Co element by adopting a low-concentration Co salt solution and prolonging the coating time, so that a uniform coating layer is formed on the surface of the particles.

[0040] In one embodiment, the time of the coprecipitation reaction in the coating method is 10-20h, for example, it can be 10h, 12h, 13h, 14h, 15h, 17h, 18h or 20h, etc.

[0041] In one embodiment, the method further comprises the steps of washing, drying, screening and removing iron of the product after coating.

[0042] As an optional technical solution of the preparation method of the lithium-rich manganese-based precursor, the method comprises the following steps:

[0043] Step 1: prepare a nickel-manganese mixed salt solution with a certain concentration according to a certain metal molar ratio; prepare a Nb salt solution and a Co salt solution with a certain concentration, and adjust the pH values of the Nb salt solution and the Co salt solution with dilute sulfuric acid to make the pH values of the two solutions the same;

[0044] Step 2: under a nitrogen atmosphere, the nickel-manganese salt solution, the Nb salt solution, the sodium hydroxide solution and the ammonia solution are added into the reaction kettle in parallel flow, wherein the amount of the Nb salt solution is fixed, and the Co salt solution is added into the Nb salt solution at a certain rate;

[0045] Step 3: the whole temperature of the reaction kettle is controlled at 40-80℃, in the early stage of the reaction, the rotation speed of the reaction kettle is controlled at 400-500rpm, the pH value is controlled at 11.0-12.0, and the ammonia concentration is controlled at 3.0-10.0g / L; when the precursor particle size grows to 2.5μm, the rotation speed of the reaction kettle is reduced to 200-300rpm, the complexing agent is replaced with a sodium citrate solution, the sodium citrate concentration is controlled at 0.2-2g / L, and after the precursor particle size grows to 3.0-3.5μm, only the Co salt solution, the sodium hydroxide solution and the sodium citrate solution are kept, and the other solutions are stopped feeding, and the feeding flow rates of the sodium hydroxide solution and the sodium citrate solution are adjusted to keep the pH value and the complexing agent concentration stable; the feeding is stopped after 10-20h of reaction;

[0046] Step 4: the slurry in the reaction kettle is washed, dried, screened and de-ironed to obtain the precursor.

[0047] In a third aspect, the application provides a lithium-rich manganese-based positive electrode material, and the preparation raw material of the lithium-rich manganese-based positive electrode material comprises the lithium-rich manganese-based precursor of the first aspect or the lithium-rich manganese-based precursor prepared by the method of the second aspect.

[0048] In one embodiment, the lithium-rich manganese-based positive electrode material has a chemical formula of Li 1.2 Ni x′ Mn y′ Nb a′ Co b′ O2, wherein 0.25 < x' ≤ 0.4, 0.6 ≤ y' < 0.75, 0.001 ≤ a' < 0.005, 0.005 ≤ b' < 0.01, and x' + y' + a' + b' = 1, the content of the Nb element decreases from the inside to the outside, the content of the Co element increases from the inside to the outside, and the lithium-rich manganese-based positive electrode material has a structure of being compact inside and loose outside.

[0049] In one embodiment, the outer surface of the lithium-rich manganese-based positive electrode material is coated with a coating layer, and the coating layer comprises lithium cobaltate.

[0050] The lithium-rich manganese-based positive electrode material provided in the present application has a gradient doping structure of Nb and Co and a structure of being compact inside and loose outside, wherein the Nb doping can improve the Li + diffusion rate and stabilize the material structure, thereby improving the rate capability and cycle performance, the Co doping can also stabilize the structure and improve the cycle performance; the compact inside of the material can improve the density, thereby improving the volumetric energy density, and the loose outside can increase the contact area with the solid-state electrolyte, thereby improving the rate capability.

[0051] The present application does not make specific limitations on the preparation method of the lithium-rich manganese-based positive electrode material, and the preparation method of the lithium-rich manganese-based positive electrode material includes the following steps:

[0052] The lithium source and the lithium-rich manganese-based precursor material are uniformly mixed according to a molar ratio of lithium to the lithium-rich manganese-based precursor of 1.15-1.25 (for example, it can be 1.15, 1.17, 1.18, 1.19, 1.20, 1.22, 1.24, or 1.25, etc.), and then sintered at a sintering temperature of 800-950°C for 10-20h to obtain the lithium-rich manganese-based positive electrode material.

[0053] In this optional technical solution, the sintering temperature is 800-950°C, for example, it can be 800°C, 820°C, 850°C, 870°C, 880°C, 900°C, 915°C, 930°C, 940°C, or 950°C, etc.

[0054] In this optional technical solution, the sintering time is 10-20h, for example, it can be 10h, 12h, 15h, 16h, 17h, 18h, 19h, or 20h, etc.

[0055] In one embodiment, the lithium source comprises lithium carbonate and / or lithium hydroxide.

[0056] In a fourth aspect, the present application provides a solid-state battery comprising the lithium-rich manganese-based positive electrode material of the third aspect.

[0057] The numerical ranges recited herein are inclusive of the endpoints and of any range that would be formed in conjunction with the inclusion of the endpoints. To the extent that specific numerical ranges do not expressly include commonly understood ranges within the numbers stated (e.g., 1 to 5 includes 3, but not 2 or 4), the specification is to be deemed to contain expressly including those ranges as if the ranges were explicitly recited.

[0058] Compared with the related art, the present application has the following beneficial effects:

[0059] (1) The lithium-rich manganese-based precursor of the present application has a specific gradient doping structure and an inner tight and outer loose structure. The lithium-rich manganese-based positive electrode material prepared by using the lithium-rich manganese-based precursor can inherit the gradient doping structure and the inner tight and outer loose structure characteristics of the precursor. The Nb doping can improve the Li diffusion rate and stabilize the material structure, thereby improving the rate and cycle performance. The Co doping can also stabilize the structure and improve the cycle performance. The inner tightness of the material can improve the density, thereby improving the volume energy density. The outer looseness can increase the contact area with the solid-state electrolyte, thereby improving the rate performance. +

[0060] (2) The method of the present application is simple and controllable. The element doping effect of the lithium-rich manganese-based precursor prepared by using the method is controllable. The lithium-rich manganese-based positive electrode material prepared by using the lithium-rich manganese-based precursor has good performance.

[0061] Other aspects can become apparent from the following detailed description, which, when taken in conjunction with the drawings, where like elements are numbered alike, discloses embodiments. DETAILED DESCRIPTION

[0062] The technical solutions of the present application will be further described below through specific embodiments.

[0063] In the embodiments of the present application, the molar ratio of nickel to manganese is taken as 30:70 for illustration, but it does not mean that the preparation of the precursor only applies to the molar ratio. Other molar ratios are also applicable to the present application.

[0064] Embodiment 1

[0065] The present embodiment provides a lithium-rich manganese-based precursor (particle size D50 is 3 μm) for a solid-state battery. The chemical formula of the lithium-rich manganese-based precursor is Ni 0.297 Mn 0.693 Nb 0.001 Co 0.009 (OH)2. The content of the Nb element decreases from the inside to the outside in a gradient manner. The content of the Co element increases from the inside to the outside in a gradient manner. The structure of the lithium-rich manganese-based precursor is tight inside and loose outside. The outer surface of the lithium-rich manganese-based precursor is coated with a cobalt hydroxide coating layer. The thickness of the coating layer is 0.1 μm.

[0066] ​The embodiment also provides the preparation method of the lithium-rich manganese-based precursor.

[0067] Step 1: a nickel-manganese salt solution with a metal concentration of 2 mol / L is prepared according to a molar ratio of Ni:Mn of 30:70 (nickel and manganese are both from sulfate); a 1 g / L Nb salt solution (Nb is from sulfate) and a 2 g / L Co salt solution (Co is from sulfate) are prepared, and the pH values of the Nb salt solution and the Co salt solution are both adjusted to 2.0 by dilute sulfuric acid.

[0068] Step 2: under a nitrogen atmosphere, the nickel-manganese salt solution, the Nb salt solution, the Co salt solution, the sodium hydroxide solution and the ammonia solution are added into a reaction kettle in parallel, the amount of the Nb salt solution is fixed, the Co salt solution is added into the Nb salt solution at a speed of 0.5 L / h, and after the mixture is formed, the mixture is introduced into the reaction kettle.

[0069] Step 3: the whole reaction kettle is controlled at a temperature of 40℃, in the early stage of the reaction, the rotation speed of the reaction kettle is controlled at 500 rpm, the pH value is controlled at 11.8-12.0, and the ammonia concentration is controlled at 3.0 g / L, when the particle size of the precursor grows to 2.5 μm, the rotation speed of the reaction kettle is reduced to 300 rpm, the complexing agent is replaced by a sodium citrate solution, the sodium citrate concentration is controlled at 0.2 g / L, after the particle size of the precursor grows to 3.0 μm, only 10 g / L of the Co salt solution, the sodium hydroxide solution and the sodium citrate solution are reserved, other solutions are stopped, and the feeding flow rates of the sodium hydroxide solution and the sodium citrate solution are adjusted to keep the pH value and the complexing agent concentration stable, and the feeding is stopped after 18 h of the reaction.

[0070] Step 4: the slurry in the reaction kettle is washed, dried, screened and de-ironed to obtain the lithium-rich manganese-based precursor.

[0071] The embodiment also provides a lithium-rich manganese-based positive electrode material, the outer surface of the lithium-rich manganese-based positive electrode material is coated with a lithium cobaltate coating layer, the chemical formula (not including the coating layer) of the lithium-rich manganese-based positive electrode material is Li 1.2 Ni 0.297 Mn 0.693 Nb 0.001 Co 0.009 O2, the content of the Nb element decreases from the inside to the outside, the content of the Co element increases from the inside to the outside, and the structure of the lithium-rich manganese-based positive electrode material is compact in the inside and loose on the outside.

[0072] The embodiment also provides the preparation method of the lithium-rich manganese-based positive electrode material.

[0073] The lithium carbonate and the lithium-rich manganese-based precursor are mixed uniformly according to a molar ratio of lithium to the lithium-rich manganese-based precursor of 1.2, and sintered at 900 DEG C for 18 h to obtain the lithium-rich manganese-based positive electrode material.

[0074] Example 2

[0075] The embodiment provides a lithium-rich manganese-based precursor (particle size D50 is 3.5 mu m) for a solid-state battery, the lithium-rich manganese-based precursor has a chemical formula of Ni 0.297 Mn 0.693 Nb 0.004 Co 0.006 (OH)2, the content of the Nb element decreases from inside to outside in a gradient manner, the content of the Co element increases from inside to outside in a gradient manner, the lithium-rich manganese-based precursor is compact inside and loose outside, and the lithium-rich manganese-based precursor is coated with a cobalt hydroxide coating layer on an outer side surface, and the thickness of the coating layer is 0.05 mu m.

[0076] The embodiment further provides a preparation method of the lithium-rich manganese-based precursor.

[0077] Step 1, a nickel-manganese salt solution with a metal concentration of 3 mol / L is prepared according to a molar ratio of Ni:Mn of 30:70 (nickel and manganese in the solution are both from sulfate salts); a Nb salt solution with a concentration of 2 g / L (Nb in the solution is from sulfate salt) and a Co salt solution with a concentration of 3 g / L (Co in the solution is from sulfate salt) are prepared, and the pH values of the Nb salt solution and the Co salt solution are both adjusted to 3.0 by using dilute sulfuric acid.

[0078] Step 2, under a helium atmosphere, the nickel-manganese salt solution, the Nb salt solution, the Co salt solution, a sodium hydroxide solution and an ammonia solution are added into a reaction kettle in parallel flow, wherein the amount of the Nb salt solution is fixed, the Co salt solution is added into the Nb salt solution at a speed of 0.2 L / h, and after the mixture of the two forms a mixed solution, the mixed solution is introduced into the reaction kettle.

[0079] Step 3, the whole process temperature of the reaction kettle is controlled at 70 DEG C, in the early stage of the reaction, the rotation speed of the reaction kettle is controlled at 400 rpm, the pH value is controlled at 11.2-11.5, and the ammonia concentration is controlled at 8.0 g / L, when the particle size of the precursor grows to 2.5 mu m, the rotation speed of the reaction kettle is reduced to 200 rpm, the complexing agent is replaced by a sodium citrate solution, the concentration of the sodium citrate solution is controlled at 1 g / L, after the particle size of the precursor grows to 3.5 mu m, only the Co salt solution, the sodium hydroxide solution and the sodium citrate solution are reserved, other solutions stop feeding, and the feeding flow rates of the sodium hydroxide solution and the sodium citrate solution are adjusted to keep the pH value and the complexing agent concentration stable, and the feeding is stopped after 10 h of reaction.

[0080] Step 4, the slurry in the reaction kettle is washed, dried, screened and de-ironed to obtain the lithium-rich manganese-based precursor.

[0081] The embodiment also provides a lithium-rich manganese-based positive electrode material, the outer surface of the lithium-rich manganese-based positive electrode material is coated with a lithium cobaltate coating layer, and the chemical formula of the lithium-rich manganese-based positive electrode material is (not including the coating layer) Li 1.2 Ni 0.297 Mn 0.693 Nb 0.004 Co 0.006 O2, the content of the Nb element decreases from the inside to the outside in a gradient manner, and the content of the Co element increases from the inside to the outside in a gradient manner, the structure of the lithium-rich manganese-based positive electrode material is compact in the inside and loose in the outside.

[0082] The embodiment also provides a preparation method of the lithium-rich manganese-based positive electrode material.

[0083] According to a molar ratio of 1.22 of lithium to the lithium-rich manganese-based precursor, lithium carbonate is uniformly mixed with the lithium-rich manganese-based precursor, and sintering is performed at 800 DEG C for 20 hours to obtain the lithium-rich manganese-based positive electrode material.

[0084] Embodiment 3

[0085] The embodiment provides a lithium-rich manganese-based precursor (particle size D50 is 3.2 microns) for a solid-state battery, the chemical formula of the lithium-rich manganese-based precursor is Ni 0.297 Mn 0.693 Nb 0.003 Co 0.007 (OH)2, the content of the Nb element decreases from the inside to the outside in a gradient manner, and the content of the Co element increases from the inside to the outside in a gradient manner, the structure of the lithium-rich manganese-based positive electrode material is compact in the inside and loose in the outside.

[0086] The embodiment also provides a preparation method of the lithium-rich manganese-based precursor.

[0087] Step 1, according to a molar ratio of Ni:Mn=30:70, a nickel-manganese salt solution with a metal concentration of 1 mol / L is prepared (nickel and manganese in the solution are both from sulfate); a Nb salt solution with a concentration of 3 g / L (Nb in the solution is from sulfate) and a Co salt solution with a concentration of 5 g / L (Co in the solution is from sulfate) are prepared, and dilute sulfuric acid is used to adjust the pH value of the Nb salt solution and the Co salt solution to 2.5.

[0088] Step 2, under a nitrogen atmosphere, the nickel-manganese salt solution, the Nb salt solution, the Co salt solution, the sodium hydroxide solution and the ammonia solution are added into a reaction kettle in parallel flow, wherein the amount of the Nb salt solution is fixed, and the Co salt solution is added into the Nb salt solution at a speed of 1 L / h, and after the mixture is formed, the mixture is introduced into the reaction kettle.

[0089] Step 3, the whole process temperature of the reactor is controlled at 55℃, in the early stage of the reaction, the rotation speed of the reactor is controlled at 450rpm, the pH value is controlled at 11.4-11.6, and the ammonia concentration is controlled at 5.0g / L; when the particle size of the precursor grows to 2.3μm, the rotation speed of the reactor is reduced to 250rpm, the complexing agent is replaced by sodium citrate solution, the concentration of sodium citrate is controlled at 1.5g / L, after the particle size of the precursor grows to 3.2μm, only Co salt solution, sodium hydroxide solution and sodium citrate solution are kept, and other solutions stop feeding, and the feeding flow of sodium hydroxide solution and sodium citrate solution is adjusted to keep the pH value and the concentration of the complexing agent stable, and the feeding is stopped after 15h of reaction.

[0090] Step 4, the slurry in the reactor is washed, dried, sieved and de-ironed to obtain the lithium-rich manganese-based precursor.

[0091] The embodiment also provides a lithium-rich manganese-based positive electrode material, the outer surface of the lithium-rich manganese-based positive electrode material is coated with a lithium cobaltate coating layer, and the chemical formula of the lithium-rich manganese-based positive electrode material (not including the coating layer) is Li 1.2 Ni 0.297 Mn 0.693 Nb 0.003 Co 0.007 O2, the content of the Nb element decreases from the inside to the outside, and the content of the Co element increases from the inside to the outside, and the structure of the lithium-rich manganese-based positive electrode material is compact inside and loose outside.

[0092] The embodiment also provides a preparation method of the lithium-rich manganese-based positive electrode material.

[0093] According to the molar ratio of lithium to the lithium-rich manganese-based precursor of 1.25, lithium carbonate is uniformly mixed with the lithium-rich manganese-based precursor, and sintered at 950℃ for 10h to obtain the lithium-rich manganese-based positive electrode material.

[0094] Example 4

[0095] The embodiment is different from example 1 in that, in step 3, in the early stage of the reaction, the rotation speed of the reactor is controlled at 300rpm, and when the particle size of the precursor grows to 2.5μm, the rotation speed of the reactor is increased to 500rpm.

[0096] Example 5

[0097] The embodiment is different from example 1 in that, in step 3, the complexing agent is not replaced, and ammonia is used as the complexing agent throughout the whole process, and the ammonia concentration is controlled at 3.0g / L.

[0098] Example 6

[0099] The difference between this embodiment and embodiment 1 is that in step 1, the pH values of the Nb salt solution and the Co salt solution are not adjusted by using dilute sulfuric acid, and in this embodiment, the pH values of the Nb salt solution and the Co salt solution are 4 and 3.5, respectively.

[0100] Example 7

[0101] The difference between this embodiment and embodiment 1 is that in step 3, after the precursor particle size grows to 3.0 μm, the concentration of the Co salt solution is 100 g / L, and the reaction time is 1.8 h.

[0102] Comparative Example 1

[0103] The difference between this comparative example and embodiment 1 is that in step 2, the Co salt solution is not added to the Nb salt solution at a speed of 0.5 L / h.

[0104] Comparative Example 2

[0105] The difference between this comparative example and embodiment 1 is that the rotation speed and the complexing agent are always constant, so that the inner and outer structures of the precursor are relatively tight.

[0106] Comparative Example 3

[0107] The difference between this comparative example and embodiment 1 is that the chemical formula of the lithium-rich manganese-based precursor is Ni 0.297 Mn 0.693 Nb 0.01 Co 0.009 (OH)2.

[0108] Comparative Example 4

[0109] The difference between this comparative example and embodiment 1 is that the chemical formula of the lithium-rich manganese-based precursor is Ni 0.297 Mn 0.693 Nb 0.001 Co 0.02 (OH)2.

[0110] Battery preparation:

[0111] Preparation of the positive electrode: the lithium-rich manganese-based positive electrode material, the solid-state electrolyte Li3InCl6, and the conductive agent Super P are mixed and ground uniformly at a mass ratio of 5:4:1.

[0112] Battery assembly: the above mixture is used as the positive electrode material, Li3InCl6 is used as the solid-state electrolyte, and lithium-indium alloy is used as the negative electrode to assemble a solid-state battery.

[0113] Performance test:

[0114] (1) Rate performance test: 2.0-4.8 V, 8C / 0.5C discharge capacity ratio at 25°C.

[0115] (2) Cycle performance test: 2.0-4.8V, 0.5C, 25℃, 1000 cycles, capacity retention rate.

[0116] The results are shown in Table 1.

[0117] Table 1

[0118] As shown in Table 1, the preparation method of the ternary precursor provided by the application is simple, the morphology of the precursor is controlled by gradient doping of Nb and Co, and the rate performance and cycle performance of the positive electrode material prepared by using the precursor can be effectively improved.

[0119] As shown by the comparison between Example 1 and Example 4, increasing the rotation speed in the later stage of the reaction will cause the degree of loosening of the external structure of the material to decrease, and the rate and cycle performance to decrease.

[0120] As shown by the comparison between Example 1 and Example 5, using ammonia as the complexing agent throughout the whole process will cause the external structure of the material to be not loose enough, and the rate and cycle performance to decrease.

[0121] As shown by the comparison between Example 1 and Example 6, different pH of the doping solution will cause the pH of the mixed solution to fluctuate, and the generation of fine powder caused by the large pH fluctuation during the reaction process will have a great impact on the cycle performance.

[0122] As shown by the comparison between Example 1 and Example 7, increasing the concentration of the Co salt solution in the coating stage and the time being too short will cause the surface of many particles to be incompletely coated, and the coating effect to be reduced.

[0123] As shown by the comparison between Example 1 and Comparative Example 1, gradient doping of Co element can effectively improve the rate and cycle performance of the material.

[0124] As shown by the comparison between Example 1 and Comparative Example 2, the structure of the material has a significant impact on the rate and cycle performance, and the loose structure is beneficial to the rate and cycle performance.

[0125] As shown by the comparison between Example 1 and Comparative Example 3, further increasing the doping amount of Nb will not continue to improve the performance, but the price of Nb element is high, and the cost will increase a lot.

[0126] As shown by the comparison between Example 1 and Comparative Example 4, further increasing the amount of Co element will not improve the performance, but will increase the cost of raw materials.

[0127] Applicant states that the above embodiments illustrate the detailed methods of the present application, but the present application is not limited to the above detailed methods, i.e. the present application does not mean that it must rely on the above detailed methods to be implemented. It should be understood by those skilled in the art that any improvement of the present application, equivalent replacement of each raw material of the product of the present application, addition of auxiliary ingredients, selection of specific methods, etc. fall within the protection scope and disclosure scope of the present application.

Claims

1. A lithium-rich manganese-based precursor for solid-state batteries, wherein, The chemical formula of the lithium-rich manganese-based precursor is Ni x Mn y Nb a Co b (OH)2, wherein 0.25 The content of the Nb element is gradually reduced from the inside to the outside, the content of the Co element is gradually increased from the inside to the outside, and the structure of the lithium-rich manganese-based precursor is compact inside and loose outside.

2. The lithium-rich manganese-based precursor of claim 1, wherein, The particle size D50 of the lithium-rich manganese-based precursor is 3-3.5 μm.

3. The lithium-rich manganese-based precursor of claim 1 or 2, wherein, The outer surface of the lithium-rich manganese-based precursor is coated with a coating layer, and the coating layer comprises cobalt hydroxide.

4. The lithium-rich manganese-based precursor of claim 3, wherein, The thickness of the coating layer is 0.05-0.1 μm.

5. A method for preparing the lithium-rich manganese-based precursor according to any one of claims 1-4, comprising the following steps: The co-precipitation reaction is carried out using a nickel-manganese salt solution, an Nb salt solution, a Co salt solution, a precipitant solution and a complexing agent solution, and during the reaction, the content of Nb provided by the Nb salt solution and the Co salt solution is gradually reduced while the content of Co is gradually increased.

6. The method of preparing a lithium-rich manganese-based precursor according to claim 5, wherein, The temperature of the co-precipitation reaction is 40-80 °C.

7. The method of producing a lithium-rich manganese-based precursor according to claim 5 or 6, wherein, The co-precipitation reaction is carried out under the protection of a protective gas. Optionally, the protective gas comprises at least one of nitrogen, helium and argon.

8. The method of producing a lithium-rich manganese-based precursor according to any one of claims 5 to 7, wherein, The reaction is divided into a pre-stage and a post-stage, and the pre-stage is the stage from the formation of the precursor to the growth of the precursor to a particle size D=(70-85)%×D0, wherein D0 is the target particle size.

9. The method of producing a lithium-rich manganese-based precursor according to claim 8, wherein, During the pre-stage, the rotation speed of the co-precipitation reaction is 400-500 rpm. Optionally, during the pre-stage, the pH value of the co-precipitation reaction is 11.0-12.

0. Optionally, during the pre-stage, the complexing agent is ammonia water. Optionally, during the pre-stage, the ammonia concentration in the reaction system is 3.0-10.0 g / L.

10. The method of producing a lithium-rich manganese-based precursor according to claim 8 or 9, wherein, During the post-stage, the rotation speed of the co-precipitation reaction is 200-300 rpm. Optionally, during the post-stage, the complexing agent is a sodium citrate solution. Optionally, during the post-stage, the concentration of sodium citrate in the reaction system is 0.2-2 g / L.

11. The method of producing a lithium-rich manganese-based precursor according to any one of claims 5 to 10, wherein, The manner of gradually reducing the content of Nb provided by the Nb salt solution and the Co salt solution and gradually increasing the content of Co is as follows: The nickel-manganese salt solution, the Nb salt solution, the Co salt solution, the precipitant solution and the complexing agent solution are added into the reaction kettle in parallel, wherein the amount of the Nb salt solution is fixed, and the Co salt solution is added into the Nb salt solution at a certain rate. Optionally, the certain rate is 0.1-1 L / h. Optionally, the pH values of the Nb salt solution and the Co salt solution are the same.

12. The method of making a lithium-rich manganese-based precursor of any one of claims 5-11, wherein, The method further comprises coating when the precursor grows to the particle size D0, and the coating method is as follows: stopping using the Nb salt solution, and only retaining the nickel-manganese salt solution, the Co salt solution, the precipitant solution and the complexing agent solution to carry out the co-precipitation reaction. Optionally, in the coating method, the pH value and the complexing agent concentration are stabilized by adjusting the strengths of the precipitant solution and the complexing agent solution. Optionally, in the coating method, the concentration of the Co salt solution is 1-10 g / L. Optionally, in the coating method, the time of the co-precipitation reaction is 10-20 h.

13. A lithium-rich manganese-based cathode material, wherein, The raw materials for preparing the lithium-rich manganese-based positive electrode material comprise the lithium-rich manganese-based precursor according to any one of claims 1-4, or the lithium-rich manganese-based precursor prepared by the method according to any one of claims 5-12.

14. The lithium-rich manganese-based positive electrode material of claim 13, wherein, The chemical formula of the lithium-rich manganese-based cathode material is Li 1.2 Ni x′ Mn y′ Nb a′ Co b′ O2, wherein 0.25<x′≤0.4, 0.6≤y′<0.75, 0.001≤a′<0.005, 0.005≤b′<0.01, and x′+y′+a′+b′=1, the content of Nb element decreases from the inside to the outside, and the content of Co element increases from the inside to the outside. The structure of the lithium-rich manganese-based cathode material is compact inside and loose outside. Optionally, an outer surface of the lithium-rich manganese-based positive electrode material is coated with a coating layer, and the coating layer comprises lithium cobaltate.

15. A solid state battery, wherein, The solid-state battery comprises the lithium-rich manganese-based positive electrode material of claim 14.

Images