Nickel-rich positive electrode precursor, preparation method therefor and use thereof

Abstract

The present application provides a nickel-rich positive electrode precursor, a preparation method therefor and a use thereof. The nickel-rich positive electrode precursor comprises a core, and a coating layer coated on a surface of the core; the core comprises a positive electrode precursor matrix material, and boron oxide and zirconium doped in the positive electrode precursor matrix material; along a direction from a center of the positive electrode precursor matrix material core to the surface, the doping amount of the zirconium gradually increases; coating elements in the coating layer comprise zirconium. In the present application, by means of directly doping boron oxide in the precursor, and in synergy and cooperation with gradient doping and coating of zirconium, the uneven surface stress distribution of the positive electrode material prepared subsequently is significantly reduced, the generation of microcracks is reduced, and the structure of the material is stabilized, thereby improving safety performance and electrochemical performance.

Description

A nickel-rich positive electrode precursor and its preparation method and application Technical Field

[0001] The present application belongs to the technical field of lithium-ion batteries and relates to a nickel-rich positive electrode precursor and a preparation method and application thereof. Background Art

[0002] To meet the high energy requirements of electric vehicles, nickel-rich layered materials LiNi 1-x-y Mn x Co y O2(x+y≤0.3)(NMC) is considered to be the most promising cathode candidate material, with the characteristics of high energy, low cost, good safety, etc. It exhibits excellent electrochemical properties and is expected to become the market-leading power battery cathode material in the future.

[0003] Although the specific capacity of layered nickel-rich cathode materials increases with the increase of nickel content, they have inherent defects and structural changes, which makes industrial application very difficult. During the cycle process, especially under special conditions such as high pressure and high temperature, the oxidized Ni 4+ It will react with the electrolyte, causing irreversible structural collapse and increasing the material's own impedance, bringing serious safety issues and being the key factor restricting its large-scale application. In addition, nickel-rich cathode materials undergo lithium-nickel mixing during the reaction process, leading to the release of active oxygen and the formation of a large amount of lithium residue Li2O or LiOH on the material surface. When exposed to air, it absorbs a large amount of H2O / CO2, accumulating a large amount of lithium residue and moisture on the material surface, greatly affecting the material's processing performance. At the same time, it causes the material to flatulence, resulting in a decrease in cycle performance, and ultimately deteriorating the overall electrochemical performance of the material and causing failure.

[0004] Both element doping and surface coating are effective methods that can improve the stability of the material structure and interface. However, in general industry, obtaining nickel-rich materials that are modified by element doping and surface coating at the same time requires a two-step process. For example, CN111244426A discloses a nickel-rich ternary positive electrode material and preparation method, and a lithium-ion battery. The method includes: mixing a nickel-rich ternary positive electrode material precursor, a first nanometal compound, and a lithium source powder, and performing a first sintering treatment to obtain a first powder; mixing the first powder with a first coating agent to obtain a first coating material; performing a second sintering treatment on the first coating material to obtain a second powder; mixing the second powder with a second coating agent to obtain a second coating material; performing a third sintering treatment on the second coating material to obtain a nickel-rich ternary positive electrode material; The document adopts a multi-step process to prepare the positive electrode material. The preparation process is cumbersome, and combined with the characteristics of nickel-rich materials such as easy water absorption, it greatly increases the manufacturing cost of the material, and the performance improvement effect on the nickel-rich positive electrode material is also very limited.

[0005] Therefore, how to improve the safety and electrochemical performance of nickel-rich positive electrode materials while reducing costs and simplifying the preparation process is a technical problem that needs to be solved urgently.

[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] This application provides a nickel-rich cathode precursor, its preparation method, and application. By directly doping the precursor with boron oxide and simultaneously synergizing with gradient zirconium doping and coating, the resulting cathode material exhibits significantly reduced surface stress unevenness, minimizing microcracks, stabilizing the material structure, and improving safety and electrochemical performance.

[0009] In the first aspect, the present application provides a nickel-rich positive electrode precursor, which includes a core and a coating layer coated on the surface of the core; the core includes a positive electrode precursor matrix material and boron oxide and zirconium doped in the positive electrode precursor matrix material; the doping amount of the zirconium gradually increases from the center of the core to the surface of the positive electrode precursor matrix material; the coating element in the coating layer includes zirconium.

[0010] The present application directly dopes boron oxide into the precursor and coordinates the gradient doping and coating of zirconium, so that the boron oxide reacts with the metal ions in the precursor in the subsequently prepared positive electrode material to obtain boron metal oxide, thereby reducing the uneven stress distribution on the surface of the material and the generation of microcracks. The gradient increase of zirconium doping improves the atomic stability in the material lattice. Secondly, the zirconium coating avoids direct contact between the ternary precursor and the electrolyte, improves the cycle stability of the material, and enhances the safety performance and electrochemical performance.

[0011] In the present application, boron oxides, rather than simple boron atoms, are doped into the precursor stage, thereby improving the atomic stability in the material lattice; if the zirconium doping is not a regular doping that increases gradually, the problem of positive electrode ball cracking and cycle decline cannot be solved either; the present application adopts dual doping of boron oxides and zirconium, and the zirconium is doped in a gradient-increasing manner, which cooperates with the zirconium coating to achieve internal stability of the atoms in the lattice and external isolation of the electrolyte, thereby achieving long battery cycles; the lack of any one of them will lead to cracking of the positive electrode ball and cycle decline.

[0012] In one embodiment, the chemical formula of the positive electrode precursor matrix material is Ni a Co b Mn c(OH)2, 0.8≤a<1, b>0, c>0, the a can be 0.8, 0.81, 0.82, 0.83, 0.84, 0.85, 0.86, 0.87, 0.88, 0.89, 0.9, 0.91, 0.92, 0.93, 0.94, 0.95, 0.96, 0.97, 0.98 or 0.99, etc.; the b can be 0.01, 0.03, 0.5, 0.08, 0.1, 0.13, 0.15, 0.18 or 0.19, etc.; the c can be 0.01, 0.03, 0.5, 0.08, 0.1, 0.13, 0.15, 0.18 or 0.19, etc.

[0013] In one embodiment, the total mass of the zirconium is 0.5-1% of the mass of the positive electrode precursor matrix material, for example, 0.5%, 0.55%, 0.6%, 0.65%, 0.7%, 0.75%, 0.8%, 0.85%, 0.9%, 0.95% or 1%.

[0014] In the present application, the total mass of zirconium includes the sum of the doping amount of zirconium and the coating amount of zirconium.

[0015] In one embodiment, the doping amount of the boron oxide is 500-5000 ppm, for example, 500 ppm, 1000 ppm, 1500 ppm, 2000 ppm, 2500 ppm, 3000 ppm, 3500 ppm, 4000 ppm, 4500 ppm or 5000 ppm.

[0016] In the nickel-rich positive electrode precursor material provided in the present application, the doping amount of boron oxide cooperates with the total mass of zirconium, and together they achieve structural stability and interface modification.

[0017] In a second aspect, the present application provides a method for preparing the nickel-rich positive electrode precursor as described in the first aspect, wherein the preparation repeatedly comprises the following steps:

[0018] Adding a nickel-cobalt-manganese mixed salt solution, a boron source solution, a zirconium source solution, a precipitant solution, and a complexing agent solution in parallel to perform a first-stage coprecipitation reaction; after reaching a target particle size, stopping the addition of the nickel-cobalt-manganese mixed salt solution and the boron source solution, and continuing the second-stage coprecipitation reaction to obtain the nickel-rich positive electrode precursor;

[0019] During the first stage of the coprecipitation reaction, the amount of zirconium source added gradually increases.

[0020] The preparation method provided in this application can achieve doping and coating of the positive electrode precursor in just one step, and is bulk doping and coating, thereby preparing a nickel-rich material with simultaneously modified structure and interface, simplifying the production process and being suitable for large-scale production.

[0021] In one embodiment, the concentration of the nickel-cobalt-manganese mixed salt solution is 50-150 g / L, for example, 50 g / L, 60 g / L, 70 g / L, 80 g / L, 90 g / L, 100 g / L, 110 g / L, 120 g / L, 130 g / L, 140 g / L or 150 g / L.

[0022] In one embodiment, the concentration of the boron source is 1 to 10 g / L, for example, 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.

[0023] In the present application, the nickel-cobalt-manganese mixed salt solution can be a variety of salts, including but not limited to at least one or a combination of at least two of a nickel-cobalt-manganese ternary mixed sulfuric acid solution, a nickel-cobalt-manganese ternary mixed hydrochloric acid solution, and a nickel-cobalt-manganese ternary mixed nitric acid solution.

[0024] In one embodiment, the boron source comprises boric acid.

[0025] In the present application, using boric acid as a reaction raw material can better achieve uniform boron doping.

[0026] In one embodiment, the concentration of the zirconium source is 1 to 10 g / L, for example, 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.

[0027] In one embodiment, the zirconium source comprises a zirconium salt.

[0028] In one embodiment, the mass concentration of the precipitant solution is 20% to 50%, for example, 20%, 30%, 40% or 50%.

[0029] In one embodiment, the precipitant solution comprises a liquid caustic soda solution.

[0030] In one embodiment, the mass concentration of the complexing agent solution is 10-30%, for example, 10%, 15%, 20%, 25% or 30%.

[0031] In one embodiment, the complexing agent solution comprises an aqueous ammonia solution.

[0032] In one embodiment, the feed rate of the nickel-cobalt-manganese mixed salt solution is 6 to 10 L / h, for example, 6 L / h, 7 L / h, 8 L / h, 9 L / h or 10 L / h.

[0033] In one embodiment, the feeding rate of the boron source solution is 1 to 3 L / h, for example, 1 L / h, 2 L / h or 3 L / h.

[0034] In one embodiment, the feed rate of the zirconium source solution is 0.3 to 1 L / h, for example, 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.

[0035] In one embodiment, the feed rate of the precipitant solution is 2 to 3 L / h, for example, 2 L / h, 2.3 L / h, 2.5 L / h, 2.8 L / h or 3 L / h.

[0036] In one embodiment, the feeding rate of the complexing agent solution is 0.6 to 1 L / h, such as 0.6 L / h, 0.7 L / h, 0.8 L / h, 0.9 L / h or 1 L / h.

[0037] In one embodiment, the target particle size D50 is 9 to 10 μm, for example, 9 μm, 9.1 μm, 9.2 μm, 9.3 μm, 9.4 μm, 9.5 μm, 9.6 μm, 9.7 μm, 9.8 μm or 10 μm.

[0038] In one embodiment, the temperature of the first stage coprecipitation reaction and the temperature of the second stage coprecipitation reaction are each independently 30-80°C, such as 30°C, 40°C, 50°C, 60°C, 70°C or 80°C.

[0039] In one embodiment, the pH value of the first stage coprecipitation reaction and the pH value of the second stage coprecipitation reaction are each independently 10-12, for example, 10, 10.3, 10.5, 10.8, 11, 11.3, 11.5, 11.8 or 12.

[0040] In one embodiment, the stirring rate of the coprecipitation reaction in the first stage and the stirring rate of the coprecipitation reaction in the second stage are each independently 100 to 500 r / min, for example, 100 r / min, 150 r / min, 200 r / min, 250 r / min, 300 r / min, 350 r / min, 400 r / min, 450 r / min or 500 r / min, etc.

[0041] As an optional technical solution, the preparation method includes the following steps:

[0042] A nickel-cobalt-manganese mixed salt solution at a feeding rate of 6 to 10 L / h, a boric acid solution at a feeding rate of 1 to 3 L / h, a zirconium salt solution at a feeding rate of 0.3 to 1 L / h, a liquid alkali solution at a feeding rate of 2 to 3 L / h, and an ammonia solution at a feeding rate of 0.6 to 1 L / h are added in parallel, and the pH value is maintained at 10 to 12 at 30 to 80° C., and a first-stage coprecipitation reaction is carried out at a stirring rate of 100 to 500 r / min. After reaching a target particle size D50 of 9 to 10 μm, the addition of the nickel-cobalt-manganese mixed salt solution and the boron source solution is stopped, and the pH value is maintained at 10 to 12 at 30 to 80° C., and a second-stage coprecipitation reaction is continued at a stirring rate of 100 to 500 r / min to obtain the nickel-rich positive electrode precursor;

[0043] During the first stage of the coprecipitation reaction, the amount of zirconium source added is gradually increased; the concentration of the nickel-cobalt-manganese mixed salt solution is 50-150 g / L; the concentration of boric acid is 1-10 g / L; the concentration of the zirconium salt is 1-10 g / L; the mass concentration of the liquid alkali solution is 20-50%; and the mass concentration of the ammonia aqueous solution is 10-30%.

[0044] The preparation method provided in this application obtains a nickel-rich positive electrode precursor material with stable structure and good interface modification through the coordinated coordination of multiple parameters.

[0045] In a third aspect, the present application provides a nickel-rich positive electrode material, which is obtained by mixing and sintering the nickel-rich positive electrode precursor as described in the first aspect with a lithium source.

[0046] When the nickel-rich precursor material provided in this application is used to prepare the positive electrode material, its preparation process and specific parameters are all conventional technical means.

[0047] In a fourth aspect, the present application further provides a lithium-ion battery, which includes the nickel-rich positive electrode material as described in the third aspect.

[0048] Compared with the related art, this application has the following beneficial effects:

[0049] (1) The present application directly dopes boron oxide into the precursor and coordinates the gradient doping and coating of zirconium, so that the boron oxide reacts with the metal ions in the precursor in the subsequently prepared positive electrode material to obtain boron metal oxide, thereby reducing the uneven stress distribution on the surface of the material and the generation of microcracks. The gradient increase of zirconium doping improves the atomic stability in the material lattice. Secondly, the zirconium coating avoids direct contact between the ternary precursor and the electrolyte, improves the cycle stability of the material, and enhances the safety performance and electrochemical performance.

[0050] (2) The preparation method provided in this application can achieve doping and coating of the positive electrode precursor in just one step, and it is bulk doping and coating, thereby preparing a nickel-rich material with simultaneously modified structure and interface, simplifying the production process and being suitable for large-scale production.

[0051] Still other aspects will become apparent upon reading and understanding the accompanying drawings and detailed description. BRIEF DESCRIPTION OF THE DRAWINGS

[0052] The accompanying drawings are used to provide a further understanding of the technical solution of this article and constitute a part of the specification. Together with the embodiments of this application, they are used to explain the technical solution of this article and do not constitute a limitation on the technical solution of this article.

[0053] FIG1 is a SEM image of the nickel-rich positive electrode precursor provided in Example 1.

[0054] FIG2 is an element distribution diagram of Zr in the nickel-rich positive electrode precursor provided in Example 1.

[0055] FIG3 is an energy spectrum diagram of the element distribution of B in the nickel-rich positive electrode precursor provided in Example 1. DETAILED DESCRIPTION

[0056] The technical solution of the present application is further described below through specific implementation methods. Those skilled in the art should understand that the embodiments are only used to help understand the present application and should not be regarded as specific limitations of the present application.

[0057] Example 1

[0058] The present embodiment provides a nickel-rich positive electrode precursor, which includes a core and a coating layer coated on the surface of the core; the core includes a positive electrode precursor matrix material and boron oxide (the doping amount of boron oxide is 1000ppm) and zirconium doped in the positive electrode precursor matrix material; along the direction from the core center to the surface of the positive electrode precursor matrix material, the doping amount of zirconium gradually increases, and the chemical formula of the positive electrode precursor matrix material is Ni 0.83 Co 0.11 Mn 0.06 (OH)2; the coating element in the coating layer includes zirconium.

[0059] The preparation method of the nickel-rich positive electrode precursor is as follows:

[0060] (1) A 100 g / L nickel-cobalt-manganese ternary mixed sulfate solution (Ni:Co:Mn molar ratio of 0.83:0.11:0.06), a 30% liquid caustic soda solution, 5 g / L zirconium sulfate, 5 g / L boric acid, and a 15% ammonia solution were simultaneously and concurrently added to a reactor containing a bottom solution (temperature of 50°C, ammonia concentration of 5 g / L, pH of 11) at feed rates of 8 L / h, 2.5 L / h, 0.3 L / h, 2 L / h, and 0.8 L / h, respectively;

[0061] The pH value was maintained at 11 at 50°C, and the first stage of the coprecipitation reaction was carried out at a stirring rate of 300r / min. The flow rate of zirconium sulfate increased continuously with the growth of the precursor particle size, and the zirconium doping amount increased continuously from the inside to the outside of the precursor. The particle size was continuously monitored. Before the particle size reached the requirement, a high-efficiency concentrator was used in the reaction process to collect all the particles and return them to the reactor for continued reaction and growth. When the particle size D50 reached 9.5μm (target particle size), the addition of nickel-cobalt-manganese ternary mixed salt solution and boric acid solution was stopped, and other materials were fed normally until the amount of zirconium added (the total mass of the doping amount and the coating amount) reached 1% of the ternary mass. Then the feeding was stopped and the reaction was continued until the material reaction was complete to obtain a doped and coated ternary precursor.

[0062] FIG1 shows an SEM image of the nickel-rich positive electrode precursor provided in Example 1. As can be seen from FIG1 , the precursor material provided in the present application is uniform in size and has good sphericity.

[0063] Figure 2 shows the element distribution diagram of Zr in the nickel-rich positive electrode precursor provided in Example 1. It can be seen from Figure 2 that Zr is uniformly doped in the precursor, and the doping amount increases from the inside to the outside, and is wrapped with a Zr shell of several microns on the outside (that is, the surface also has a zirconium coating layer).

[0064] FIG3 shows the element distribution energy spectrum of B in the nickel-rich positive electrode precursor provided in Example 1. It can be seen from FIG3 that boron oxide is uniformly doped in the precursor.

[0065] Example 2

[0066] The present embodiment provides a nickel-rich positive electrode precursor, which includes a core and a coating layer coated on the surface of the core; the core includes a positive electrode precursor matrix material and boron oxide (the doping amount of boron oxide is 1500ppm) and zirconium doped in the positive electrode precursor matrix material; along the direction from the core center to the surface of the positive electrode precursor matrix material, the doping amount of zirconium gradually increases, and the chemical formula of the positive electrode precursor matrix material is Ni 0.83 Co 0.11 Mn 0.06 (OH)2; the coating element in the coating layer includes zirconium.

[0067] The preparation method of the nickel-rich positive electrode precursor is as follows:

[0068] (1) A 150 g / L nickel-cobalt-manganese ternary mixed sulfate solution (Ni:Co:Mn molar ratio of 0.83:0.11:0.06), a 50% liquid caustic soda solution, 10 g / L zirconium sulfate, 10 g / L boric acid, and a 30% ammonia solution were simultaneously and concurrently added to a reactor containing a bottom solution (temperature of 40°C, ammonia concentration of 10 g / L, pH of 12) at feed rates of 10 L / h, 3 L / h, 0.5 L / h, 2.5 L / h, and 1 L / h, respectively;

[0069] The pH value was maintained at 12 at 40°C, and the first stage of the coprecipitation reaction was carried out at a stirring rate of 200 r / min. The flow rate of zirconium sulfate increased continuously with the growth of the precursor particle size, and the zirconium doping amount increased continuously from the inside to the outside of the precursor. The particle size was continuously monitored. Before the particle size reached the requirement, a high-efficiency concentrator was used in the reaction process to collect all the particles and return them to the reactor for continuous reaction and growth. When the particle size D50 reached 9 μm, the addition of nickel-cobalt-manganese ternary mixed salt solution and boric acid solution was stopped, and other materials were fed normally until the amount of zirconium added (the total mass of the doping amount and the coating amount) reached 1% of the ternary mass. Then the feeding was stopped and the reaction was continued until the material reaction was complete to obtain a doped and coated ternary precursor.

[0070] Example 3

[0071] The present embodiment provides a nickel-rich positive electrode precursor, which includes a core and a coating layer coated on the surface of the core; the core includes a positive electrode precursor matrix material and boron oxide (the doping amount of boron oxide is 5000ppm) and zirconium doped in the positive electrode precursor matrix material; along the direction from the core center to the surface of the positive electrode precursor matrix material, the doping amount of zirconium gradually increases, and the chemical formula of the positive electrode precursor matrix material is Ni 0.83 Co 0.11 Mn 0.06 (OH)2; the coating element in the coating layer includes zirconium.

[0072] The preparation method of the nickel-rich positive electrode precursor is as follows:

[0073] (1) A 50 g / L nickel-cobalt-manganese ternary mixed sulfate solution (Ni:Co:Mn molar ratio of 0.83:0.11:0.06), a 20% liquid caustic soda solution, 1 g / L zirconium sulfate, 1 g / L boric acid, and a 10% ammonia solution were simultaneously and concurrently added to a reactor containing a bottom solution (temperature of 60°C, ammonia concentration of 1 g / L, pH of 10) at feed rates of 6 L / h, 1 L / h, 0.3 L / h, 1 L / h, and 0.6 L / h, respectively;

[0074] The pH value was maintained at 10 at 60°C, and the first stage of the coprecipitation reaction was carried out at a stirring rate of 100 r / min. The flow rate of zirconium sulfate increased continuously with the growth of the precursor particle size, and the zirconium doping amount increased continuously from the inside to the outside of the precursor. The particle size was continuously monitored. Before the particle size reached the requirement, a high-efficiency concentrator was used in the reaction process to collect all the particles and return them to the reactor for continuous reaction and growth. When the particle size D50 reached 9 μm, the addition of nickel-cobalt-manganese ternary mixed salt solution and boric acid solution was stopped, and other materials were fed normally until the amount of zirconium added (the total mass of the doping amount and the coating amount) reached 1% of the ternary mass. Then the feeding was stopped and the reaction was continued until the material reaction was complete to obtain a doped and coated ternary precursor.

[0075] Example 4

[0076] The difference between this embodiment and embodiment 1 is that the chemical formula of the positive electrode precursor matrix material in this embodiment is Ni 0.9 Co 0.05 Mn 0.05 (OH)2.

[0077] In the preparation method, a nickel-cobalt-manganese ternary mixed sulfate solution is prepared, wherein the molar ratio of Ni:Co:Mn is 0.9:0.05:0.05.

[0078] The rest of the preparation methods and parameters were the same as those in Example 1.

[0079] Example 5

[0080] The difference between this embodiment and embodiment 1 is that the chemical formula of the positive electrode precursor matrix material in this embodiment is Ni 0.6 Co 0.2 Mn 0.2 (OH)2.

[0081] In the preparation method, a nickel-cobalt-manganese ternary mixed sulfate solution is prepared, wherein the molar ratio of Ni:Co:Mn is 0.6:0.2:0.2.

[0082] The rest of the preparation methods and parameters were the same as those in Example 1.

[0083] Comparative Example 1

[0084] The difference between this comparative example and Example 1 is that the nickel-rich positive electrode precursor provided in this comparative example is not doped with boron oxide.

[0085] In the preparation method, no boric acid is added.

[0086] The rest of the preparation methods and parameters were the same as those in Example 1.

[0087] Comparative Example 2

[0088] The difference between this comparative example and Example 1 is that the zirconium in the nickel-rich positive electrode precursor provided in this comparative example is not gradient-doped.

[0089] During the preparation method, the feed flow rate of zirconium sulfate remains unchanged.

[0090] The rest of the preparation methods and parameters were the same as those in Example 1.

[0091] Comparative Example 3

[0092] The difference between this comparative example and Example 1 is that the nickel-rich positive electrode precursor provided in this comparative example is not doped with zirconium and is not coated with zirconium.

[0093] In the preparation method, zirconium sulfate is not added.

[0094] The rest of the preparation methods and parameters were the same as those in Example 1.

[0095] The nickel-rich positive electrode precursors provided by Examples 1-5 and Comparative Examples 1-3 were mixed with lithium hydroxide at a molar ratio of Li:M (M is a metal element) = 1.05, and calcined at a calcination temperature of 800°C for 13 hours in an air atmosphere to obtain a positive electrode material.

[0096] The positive electrode materials provided in Examples 1-5 and Comparative Examples 1-3 were used as positive electrode active materials, with a mass ratio of positive electrode active material: PVDF: SP of 95:3:2. NMP was added to obtain a positive electrode slurry, which was then coated on the surface of an aluminum foil to obtain a positive electrode sheet.

[0097] A button battery is obtained by assembling a lithium sheet as a counter electrode with a positive electrode sheet.

[0098] Electrochemical performance testing was conducted on the button-type batteries provided in Examples 1-5 and Comparative Examples 1-3. Following 12 hours of aging after assembly, the batteries were subjected to charge-discharge tests at different potentials. After activation at a voltage of 3-4.3 V and a rate of 0.1 C for three cycles, the batteries were cycled at 2 C for 200 cycles to determine their specific capacity and capacity retention. The test results are shown in Table 1.

[0099] Table 1

[0100] From the data results of Examples 1, 4 and 5, it can be seen that the synergistic combination of doping and coating is more conducive to improving the cycle stability of nickel-rich materials. Under medium and low nickel conditions, the performance improvement is not obvious.

[0101] From the data results of the embodiments and comparative examples 1-3, it can be seen that the nickel-rich positive electrode precursor material provided by the present application, if not doped with boron oxide, can ensure the stability of the atoms in the material lattice; and if the gradient doping of zirconium is not performed, the problems of cracking of the positive electrode balls and cycle decline cannot be solved; if zirconium is not doped and coated, it cannot play the role of isolating the electrolyte and protecting the positive electrode material; that is, in the present application, the coordinated cooperation of boron oxide and zirconium must be achieved to jointly achieve the internal stability of the atoms in the lattice and the external isolation of the electrolyte to achieve the purpose of long cycle of the battery.

[0102] In summary, the present application can achieve the doping and coating of the positive electrode precursor in just one step, and it is bulk doping and coating, and a nickel-rich material with simultaneously modified structure and interface is prepared; by directly doping boron oxide in the precursor, and coordinating with the gradient doping and coating of zirconium, the positive electrode material prepared subsequently, the boron oxide reacts with the metal ions in the precursor to obtain boron metal oxide, which reduces the uneven stress distribution on the surface of the material and reduces the generation of microcracks. The gradient increase in zirconium doping improves the atomic stability in the material lattice. Secondly, the zirconium coating avoids direct contact between the ternary precursor and the electrolyte, improves the cycle stability of the material, and enhances the safety performance and electrochemical performance.

[0103] The applicant declares that the above is only a specific implementation method of the present application, but the protection scope of the present application is not limited thereto. Technical personnel in the relevant technical field should understand that any changes or substitutions that can be easily thought of by technical personnel in the relevant technical field within the technical scope disclosed in this application fall within the protection scope and disclosure scope of this application.

Claims

1. A nickel-rich positive electrode precursor, comprising a core and a coating layer coated on the surface of the core; the core comprises a positive electrode precursor matrix material and boron oxide and zirconium doped in the positive electrode precursor matrix material; along the direction from the core center to the surface of the positive electrode precursor matrix material, the doping amount of the zirconium gradually increases; the coating element in the coating layer comprises zirconium.

2. The nickel-rich positive electrode precursor according to claim 1, wherein The chemical formula of the positive electrode precursor matrix material is Ni a Co b Mn c (OH)2, 0.8≤a<1, b>0, c>0.

3. The nickel-rich positive electrode precursor according to claim 1 or 2, wherein: The total mass of the zirconium is 0.5-1% of the mass of the positive electrode precursor matrix material; Optionally, the doping amount of the boron oxide is 500 to 5000 ppm.

4. A method for preparing a nickel-rich positive electrode precursor according to any one of claims 1 to 3, comprising the following steps: Adding a nickel-cobalt-manganese mixed salt solution, a boron source solution, a zirconium source solution, a precipitant solution and a complexing agent solution in parallel to carry out a first-stage coprecipitation reaction, and after reaching a target particle size, stopping adding the nickel-cobalt-manganese mixed salt solution and the boron source solution, and continuing the second-stage coprecipitation reaction to obtain the nickel-rich positive electrode precursor; Among them, during the first stage of the co-precipitation reaction, the amount of zirconium source added gradually increased.

5. The method for preparing a nickel-rich positive electrode precursor according to claim 4, wherein: The concentration of the nickel-cobalt-manganese mixed salt solution is 50-150 g / L; Optionally, the concentration of the boron source is 1 to 10 g / L; Optionally, the boron source comprises boric acid; Optionally, the concentration of the zirconium source is 1 to 10 g / L; Optionally, the zirconium source comprises a zirconium salt; Optionally, the mass concentration of the precipitant solution is 20-50%; Optionally, the precipitant solution comprises a liquid alkali solution; Optionally, the mass concentration of the complexing agent solution is 10 to 30%; Optionally, the complexing agent solution comprises an aqueous ammonia solution.

6. The method for preparing a nickel-rich positive electrode precursor according to claim 4 or 5, wherein: The feeding rate of the nickel-cobalt-manganese mixed salt solution is 6 to 10 L / h; Optionally, the feeding rate of the boron source solution is 1 to 3 L / h; Optionally, the feed rate of the zirconium source solution is 0.3 to 1 L / h; Optionally, the feed rate of the precipitant solution is 2 to 3 L / h; Optionally, the feeding rate of the complexing agent solution is 0.6 to 1 L / h.

7. The method for preparing a nickel-rich positive electrode precursor according to any one of claims 4 to 6, wherein: The target particle size D50 is 9 to 10 μm; Optionally, the temperature of the coprecipitation reaction in the first stage and the temperature of the coprecipitation reaction in the second stage are each independently 30 to 80° C.; Optionally, the pH value of the coprecipitation reaction in the first stage and the pH value of the coprecipitation reaction in the second stage are each independently 10 to 12; Optionally, the stirring rate of the coprecipitation reaction in the first stage and the stirring rate of the coprecipitation reaction in the second stage are each independently 100 to 500 r / min.

8. The method for preparing a nickel-rich positive electrode precursor according to any one of claims 4 to 7, comprising the following steps: A nickel-cobalt-manganese mixed salt solution with a feed rate of 6 to 10 L / h, a boric acid solution with a feed rate of 1 to 3 L / h, a zirconium salt solution with a feed rate of 0.3 to 1 L / h, a liquid alkali solution with a feed rate of 2 to 3 L / h, and an ammonia solution with a feed rate of 0.6 to 1 L / h are added in parallel, and the pH value is maintained at 10 to 12 at 30 to 80°C. The first stage of the coprecipitation reaction is carried out at a stirring rate of 100 to 500 r / min to achieve a target particle size D50 of After the particle size reaches 9 to 10 μm, the addition of the nickel-cobalt-manganese mixed salt solution and the boron source solution is stopped, the pH value is maintained at 10 to 12 at 30 to 80° C., and the second stage of the coprecipitation reaction is continued at a stirring rate of 100 to 500 r / min to obtain the nickel-rich positive electrode precursor; Among them, during the first stage of the coprecipitation reaction, the amount of zirconium source added is gradually increased; the concentration of the nickel-cobalt-manganese mixed salt solution is 50-150 g / L; the concentration of boric acid is 1-10 g / L; the concentration of zirconium salt is 1-10 g / L; the mass concentration of the liquid alkali solution is 20-50%; and the mass concentration of the ammonia solution is 10-30%.

9. A nickel-rich positive electrode material, wherein: The nickel-rich positive electrode material is obtained by mixing and sintering the nickel-rich positive electrode precursor as described in any one of claims 1 to 3 with a lithium source.

10. A lithium ion battery, wherein: The lithium-ion battery comprises the nickel-rich positive electrode material as claimed in claim 9.

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