A nickel-rich cathode precursor, its preparation method and application

Abstract

This invention provides a nickel-rich cathode precursor, its preparation method, and its application. The nickel-rich cathode precursor includes a core and a coating layer covering the surface of the core; the core includes a cathode precursor matrix material and boron oxide and zirconium doped into the cathode precursor matrix material; the zirconium doping amount gradually increases along the direction from the center of the core to the surface of the cathode precursor matrix material; the coating element in the coating layer includes zirconium. This invention, by directly doping boron oxide into the precursor, while simultaneously coordinating with gradient doping and coating of zirconium, significantly reduces the uneven surface stress distribution of the subsequently prepared cathode material, reduces the generation of microcracks, stabilizes the material structure, and improves safety and electrochemical performance.

Description

Technical Field

[0001] This invention belongs to the field of lithium-ion battery technology, and relates to a nickel-rich cathode precursor, its preparation method, and its application. Background Technology

[0002] To meet the high energy demands of electric vehicles, nickel-rich layered materials LiNi 1-x-y Mn x Co y O2 (x+y≤0.3) (NMC) is considered the most promising cathode material candidate, possessing characteristics such as high energy, low cost, and good safety, exhibiting excellent electrochemical performance, and is expected to become the dominant cathode material for power batteries in the future market.

[0003] While layered nickel-rich cathode materials exhibit increased specific capacity with increasing nickel content, their inherent defects and structural changes pose significant challenges for industrial application. During cycling, especially under extreme conditions such as high pressure and high temperature, the oxidized Ni in layered nickel-rich cathode materials... 4+ Side reactions with the electrolyte can occur, leading to irreversible structural collapse and increased material impedance, resulting in serious safety issues and hindering large-scale application. Furthermore, during the reaction, lithium-nickel mixed-off occurs in nickel-rich cathode materials, causing the release of active oxygen and the formation of large amounts of lithium residue (Li2O or LiOH) on the material surface. Upon contact with air, this residue absorbs large amounts of H2O / CO2, accumulating significant amounts of lithium residue and moisture on the surface. This greatly affects the material's processing performance, causes gas expansion, leads to cycle performance degradation, and ultimately results in the deterioration of the overall electrochemical performance and failure of the material.

[0004] Element doping and surface coating are both effective methods to improve the stability of material structure and interface. However, in general, obtaining nickel-rich materials with simultaneous element doping and surface coating modification in industry requires a two-step process. For example, CN111244426A discloses a nickel-rich ternary cathode material and its preparation method, as well as a lithium-ion battery. This method includes: mixing a nickel-rich ternary cathode material precursor, a first nano-metal compound, and 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; and performing a third sintering treatment on the second coating material to obtain the nickel-rich ternary cathode material. This literature uses a multi-step process to prepare the cathode material. The preparation process is cumbersome, and combined with the hygroscopic nature of nickel-rich materials, it greatly increases the manufacturing cost while having very limited effect on improving the performance of the nickel-rich cathode material.

[0005] Therefore, how to improve the safety and electrochemical performance of nickel-rich cathode materials while reducing costs and simplifying the preparation process is an urgent technical problem to be solved. Summary of the Invention

[0006] To address the shortcomings of existing technologies, the present invention aims to provide a nickel-rich cathode precursor, its preparation method, and its applications. This invention directly dops the precursor with boron oxide ions, while simultaneously coordinating with gradient doping and coating of zirconium. This significantly reduces the uneven surface stress distribution in the subsequently prepared cathode material, decreases microcrack formation, stabilizes the material structure, and improves safety and electrochemical performance.

[0007] To achieve this objective, the present invention employs the following technical solution:

[0008] In a first aspect, the present invention provides a nickel-rich cathode precursor, the nickel-rich cathode precursor comprising a core and a coating layer covering the surface of the core; the core comprising a cathode precursor matrix material and boron oxide and zirconium doped in the cathode precursor matrix material; the amount of zirconium doping gradually increases along the direction from the center of the core to the surface of the cathode precursor matrix material; the coating element in the coating layer comprises zirconium.

[0009] This invention directly dops boron oxide ions into the precursor, while simultaneously coordinating with gradient doping and coating of zirconium. This allows the boron oxide ions in the subsequently prepared cathode material to react with the metal ions in the precursor, yielding boron metal oxides. This reduces uneven stress distribution on the material surface and minimizes the formation of microcracks. The gradient doping of zirconium increases the atomic stability in the material lattice. Furthermore, zirconium coating prevents direct contact between the ternary precursor and the electrolyte, improving the material's cycle stability, safety performance, and electrochemical performance.

[0010] In this invention, boron oxide ions are incorporated into the precursor stage, rather than simply boron atoms, which improves the atomic stability in the material lattice. If the zirconium doping is not a gradually increasing, regular doping, it will also fail to solve the problems of cathode sphere cracking and cycle degradation. This invention achieves dual doping of boron oxide ions and zirconium, with zirconium doping increasing in a gradient, working synergistically with zirconium coating to achieve internal atomic stability in the lattice and external isolation from the electrolyte, thus enabling long battery cycles. The absence of either one will lead to cathode sphere cracking and cycle degradation.

[0011] Preferably, the general 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, where 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.; b can be 0.01, 0.03, 0.5, 0.08, 0.1, 0.13, 0.15, 0.18, or 0.19, etc.; and c can be 0.01, 0.03, 0.5, 0.08, 0.1, 0.13, 0.15, 0.18, or 0.19, etc.

[0012] Preferably, the total mass of the zirconium is 0.5% to 1% of the mass of the cathode 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%.

[0013] In this invention, the total mass of zirconium includes the sum of the zirconium doping amount and the zirconium coating amount.

[0014] Preferably, the boron oxide doping amount is 500 to 5000 ppm, such as 500 ppm, 1000 ppm, 1500 ppm, 2000 ppm, 2500 ppm, 3000 ppm, 3500 ppm, 4000 ppm, 4500 ppm or 5000 ppm.

[0015] In the nickel-rich cathode precursor material provided by this invention, the amount of boron oxide doping is synergistically combined with the total mass of zirconium, thus achieving structural stability and interface modification.

[0016] In a second aspect, the present invention provides a method for preparing a nickel-rich cathode precursor as described in the first aspect, wherein the preparation process repeatedly includes the following steps:

[0017] A nickel-cobalt-manganese mixed salt solution, a boron source solution, a zirconium source solution, a precipitant solution, and a complexing agent solution are added in parallel to carry out the first stage of co-precipitation reaction. After the target particle size is reached, the addition of the nickel-cobalt-manganese mixed salt solution and the boron source solution is stopped, and the second stage of co-precipitation reaction is continued to obtain the nickel-rich cathode precursor.

[0018] In the first stage of the coprecipitation reaction, the amount of zirconium source added gradually increases.

[0019] The preparation method provided by this invention can achieve doping and coating of the cathode precursor in just one step, and it is a bulk doping and coating process. This method produces nickel-rich materials with simultaneous structural and interface modifications, which simplifies the production process and is suitable for large-scale production.

[0020] Preferably, the concentration of the nickel-cobalt-manganese mixed salt solution is 50–150 g / L, such as 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.

[0021] Preferably, the concentration of the boron source is 1 to 10 g / L, such as 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.

[0022] In this invention, 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 the following: nickel-cobalt-manganese ternary mixed sulfuric acid solution, nickel-cobalt-manganese ternary mixed hydrochloric acid solution, and nickel-cobalt-manganese ternary mixed nitric acid solution.

[0023] Preferably, the boron source includes boric acid.

[0024] In this invention, boric acid is used as the reaction raw material, which can better achieve uniform boron doping.

[0025] Preferably, the concentration of the zirconium source is 1 to 10 g / L, such as 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.

[0026] Preferably, the zirconium source comprises a zirconium salt.

[0027] Preferably, the mass concentration of the precipitant solution is 20-50%, for example, 20%, 30%, 40% or 50%.

[0028] Preferably, the precipitant solution comprises a liquid alkali solution.

[0029] Preferably, the mass concentration of the complexing agent solution is 10-30%, such as 10%, 15%, 20%, 25%, or 30%.

[0030] Preferably, the complexing agent solution comprises an aqueous ammonia solution.

[0031] Preferably, the feed rate of the nickel-cobalt-manganese mixed salt solution is 6 to 10 L / h, such as 6 L / h, 7 L / h, 8 L / h, 9 L / h or 10 L / h.

[0032] Preferably, the feed rate of the boron source solution is 1 to 3 L / h, such as 1 L / h, 2 L / h or 3 L / h.

[0033] Preferably, 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.

[0034] Preferably, the feed rate of the precipitant solution is 2 to 3 L / h, such as 2 L / h, 2.3 L / h, 2.5 L / h, 2.8 L / h or 3 L / h.

[0035] Preferably, the feed rate of the complexing agent solution is 0.6 to 1 L / h, for example, 0.6 L / h, 0.7 L / h, 0.8 L / h, 0.9 L / h or 1 L / h.

[0036] Preferably, the D50 of the target particle size is 9 to 10 μm, such as 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.

[0037] Preferably, the temperature of the first stage coprecipitation reaction and the temperature of the second stage coprecipitation reaction are each independently 30 to 80°C, for example 30°C, 40°C, 50°C, 60°C, 70°C or 80°C.

[0038] Preferably, the pH value of the first stage coprecipitation reaction and the pH value of the second stage coprecipitation reaction are each independently 10 to 12, such as 10, 10.3, 10.5, 10.8, 11, 11.3, 11.5, 11.8 or 12.

[0039] Preferably, the stirring rate of the first stage coprecipitation reaction and the stirring rate of the second stage coprecipitation reaction are each independently 100-500 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.

[0040] As a preferred technical solution, the preparation method includes the following steps:

[0041] A nickel-cobalt-manganese mixed salt solution, a boric acid solution, a zirconium salt solution, a liquid alkali solution, and an ammonia solution are fed in parallel at a rate of 6–10 L / h, 1–3 L / h, 0.3–1 L / h, 2–3 L / h, and 0.6–1 L / h. The first stage of co-precipitation reaction is carried out at 30–80°C with a pH of 10–12 and a stirring rate of 100–500 r / min. After the target particle size D50 of 9–10 μm is reached, the addition of the nickel-cobalt-manganese mixed salt solution and the boron source solution is stopped. The second stage of co-precipitation reaction is carried out at 30–80°C with a pH of 10–12 and a stirring rate of 100–500 r / min to obtain the nickel-rich cathode precursor.

[0042] In the first stage of the co-precipitation reaction, the amount of zirconium source added gradually increases; 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%.

[0043] The preparation method provided by this invention, through the synergistic coordination of multiple parameters, yields a nickel-rich cathode precursor material with stable structure and good interface modification.

[0044] Thirdly, the present invention provides a nickel-rich cathode material, which is obtained by mixing and sintering a nickel-rich cathode precursor as described in the first aspect with a lithium source.

[0045] When preparing cathode materials from nickel-rich precursor materials provided by this invention, the preparation process and specific parameters are all conventional technical means.

[0046] Fourthly, the present invention also provides a lithium-ion battery, the lithium-ion battery comprising the nickel-rich cathode material as described in the third aspect.

[0047] Compared with the prior art, the present invention has the following beneficial effects:

[0048] (1) This invention directly dops boron oxides in the precursor, while simultaneously coordinating with the gradient doping and coating of zirconium. This allows the boron oxides in the subsequently prepared cathode material to react with the metal ions in the precursor to obtain boron metal oxides, thereby reducing the uneven distribution of stress on the material surface and reducing the generation of microcracks. The gradient doping of zirconium increases the atomic stability in the material lattice. Furthermore, the zirconium coating avoids direct contact between the ternary precursor and the electrolyte, improving the cycle stability of the material and enhancing its safety and electrochemical performance.

[0049] (2) The preparation method provided by the present invention can achieve doping and coating of the positive electrode precursor in just one step, and it is a bulk doping and coating, thus preparing nickel-rich materials with simultaneous structural and interface modification, simplifying the production process and making it suitable for large-scale production. Attached Figure Description

[0050] Figure 1 SEM image of the nickel-rich cathode precursor provided in Example 1.

[0051] Figure 2 The elemental distribution diagram of Zr in the nickel-rich cathode precursor provided in Example 1.

[0052] Figure 3 The elemental distribution energy spectrum of B in the nickel-rich cathode precursor provided in Example 1. Detailed Implementation

[0053] The technical solution of the present invention will be further illustrated below through specific embodiments. Those skilled in the art should understand that the embodiments described are merely illustrative of the present invention and should not be construed as limiting the invention in any way.

[0054] Example 1

[0055] This embodiment provides a nickel-rich cathode precursor, which includes a core and a coating layer covering the surface of the core. The core includes a cathode precursor matrix material and boron oxide (1000 ppm doping) and zirconium doped into the cathode precursor matrix material. The zirconium doping content gradually increases from the center of the core to the surface of the cathode precursor matrix material. The chemical formula of the cathode precursor matrix material is Ni. 0.83 Co 0.11 Mn 0.06 (OH)2; the coating element in the coating layer includes zirconium.

[0056] The preparation method of the nickel-rich cathode precursor is as follows:

[0057] (1) A nickel-cobalt-manganese ternary mixed sulfate solution with a concentration of 100 g / L (the molar ratio of Ni:Co:Mn is 0.83:0.11:0.06), a liquid alkali solution with a mass concentration of 30%, zirconium sulfate with a mass concentration of 5 g / L, boric acid with a mass concentration of 5 g / L, and an ammonia solution with a mass concentration of 15% were simultaneously and concurrently added to the reactor containing the bottom liquid (temperature is 50℃, ammonia concentration is 5 g / L, pH is 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.

[0058] The first stage of co-precipitation reaction was carried out at 50℃ with a pH of 11 and a stirring rate of 300 r / min. The flow rate of zirconium sulfate increased continuously as the precursor particle size grew. The zirconium doping amount increased from the inside out of the precursor. The particle size was continuously monitored. Before the particle size reached the required level, a high-efficiency thickener was used to collect all the particles and return them to the reactor for continued reaction and growth. When the particle size D50 reached 9.5 μm (target particle size), the addition of nickel-cobalt-manganese ternary mixed salt solution and boric acid solution was stopped, while other materials were fed normally until the amount of zirconium added (total mass of doping and coating) reached 1% of the ternary mass. Then the feeding was stopped and the reaction continued until the material was completely reacted to obtain the doped and coated ternary precursor.

[0059] Figure 1 The SEM image of the nickel-rich cathode precursor provided in Example 1 is shown. Figure 1 It can be seen that the precursor material provided by the present invention has uniform size and good sphericity.

[0060] Figure 2 The elemental distribution diagram of Zr in the nickel-rich cathode precursor provided in Example 1 is shown. Figure 2 As can be seen, Zr is uniformly doped in the precursor, with the doping amount increasing continuously from the inside out, and it is covered with a Zr shell of several micrometers (i.e., the surface also has a zirconium coating layer).

[0061] Figure 3 The table shows the elemental distribution energy spectrum of B in the nickel-rich cathode precursor provided in Example 1. Figure 3 It can be seen that boron oxide ions are uniformly doped in the precursor.

[0062] Example 2

[0063] This embodiment provides a nickel-rich cathode precursor, which includes a core and a coating layer covering the surface of the core. The core includes a cathode precursor matrix material and boron oxide (1500 ppm doping) and zirconium doped into the cathode precursor matrix material. The zirconium doping amount gradually increases from the center of the core to the surface of the cathode precursor matrix material. The chemical formula of the cathode precursor matrix material is Ni. 0.83 Co 0.11 Mn 0.06 (OH)2; the coating element in the coating layer includes zirconium.

[0064] The preparation method of the nickel-rich cathode precursor is as follows:

[0065] (1) A nickel-cobalt-manganese ternary mixed sulfate solution with a concentration of 150 g / L (the molar ratio of Ni:Co:Mn is 0.83:0.11:0.06), a liquid alkali solution with a mass concentration of 50%, zirconium sulfate with a mass concentration of 10 g / L, boric acid with a mass concentration of 10 g / L, and an ammonia solution with a mass concentration of 30% were simultaneously and concurrently added to the reactor containing the bottom liquid (temperature of 40℃, 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.

[0066] The first stage of co-precipitation reaction was carried out at 40℃ with a pH of 12 and a stirring rate of 200 r / min. The flow rate of zirconium sulfate increased continuously as the precursor particle size grew. The zirconium doping amount increased continuously from the inside out of the precursor. The particle size was continuously monitored. Before the particle size reached the required level, a high-efficiency thickener was used to collect all the particles and return them to the reactor for continued 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, while other materials were fed normally until the amount of zirconium added (total mass of doping and coating) reached 1% of the ternary mass. Then the feeding was stopped and the reaction continued until the material was completely reacted to obtain the doped and coated ternary precursor.

[0067] Example 3

[0068] This embodiment provides a nickel-rich cathode precursor, which includes a core and a coating layer covering the surface of the core. The core includes a cathode precursor matrix material and boron oxide (5000 ppm doping) and zirconium doped into the cathode precursor matrix material. The zirconium doping amount gradually increases from the center of the core to the surface of the cathode precursor matrix material. The chemical formula of the cathode precursor matrix material is Ni. 0.83 Co 0.11 Mn 0.06 (OH)2; the coating element in the coating layer includes zirconium.

[0069] The preparation method of the nickel-rich cathode precursor is as follows:

[0070] (1) A nickel-cobalt-manganese ternary mixed sulfate solution with a concentration of 50 g / L (the molar ratio of Ni:Co:Mn is 0.83:0.11:0.06), a liquid alkali solution with a mass concentration of 20%, zirconium sulfate with a mass concentration of 1 g / L, boric acid with a mass concentration of 1 g / L, and an ammonia solution with a mass concentration of 10% were simultaneously and concurrently added to the reactor containing the bottom liquid (temperature of 60℃, 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.

[0071] The first stage of co-precipitation reaction was carried out at 60℃ with a pH of 10 and a stirring rate of 100 r / min. The flow rate of zirconium sulfate increased continuously as the precursor particle size grew. The zirconium doping amount increased continuously from the inside out of the precursor. The particle size was continuously monitored. Before the particle size reached the required level, a high-efficiency thickener was used to collect all the particles and return them to the reactor for continued 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, while other materials were fed normally until the amount of zirconium added (total mass of doping and coating) reached 1% of the ternary mass. Then the feeding was stopped and the reaction continued until the material was completely reacted to obtain the doped and coated ternary precursor.

[0072] Example 4

[0073] 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.

[0074] 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.

[0075] The remaining preparation methods and parameters are consistent with those in Example 1.

[0076] Example 5

[0077] 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.

[0078] In the preparation method, a nickel-cobalt-manganese ternary mixed sulfate solution is used, wherein the molar ratio of Ni:Co:Mn is 0.6:0.2:0.2.

[0079] The remaining preparation methods and parameters are consistent with those in Example 1.

[0080] Comparative Example 1

[0081] The difference between this comparative example and Example 1 is that the nickel-rich cathode precursor provided in this comparative example is not doped with boron oxide.

[0082] Boric acid is not added in the preparation method.

[0083] The remaining preparation methods and parameters are consistent with those in Example 1.

[0084] Comparative Example 2

[0085] The difference between this comparative example and Example 1 is that the zirconium in the nickel-rich cathode precursor provided in this comparative example is not gradient-doped.

[0086] In the preparation method, the feed flow rate of zirconium sulfate remains constant.

[0087] The remaining preparation methods and parameters are consistent with those in Example 1.

[0088] Comparative Example 3

[0089] The difference between this comparative example and Example 1 is that the nickel-rich cathode precursor provided in this comparative example is not doped with zirconium, nor is it coated with zirconium.

[0090] Zirconium sulfate is not added in the preparation method.

[0091] The remaining preparation methods and parameters are consistent with those in Example 1.

[0092] The nickel-rich cathode precursors provided in Examples 1-5 and Comparative Examples 1-3 were mixed with lithium hydroxide at a molar ratio of Li:M (M being a metal element) = 1.05 and calcined at 800°C for 13 hours in an air atmosphere to obtain cathode materials.

[0093] 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 onto the surface of an aluminum foil to obtain a positive electrode sheet.

[0094] A coin cell is obtained by assembling a lithium sheet as the counter electrode with a positive electrode.

[0095] Electrochemical performance tests were conducted on the coin cells provided in Examples 1-5 and Comparative Examples 1-3. The test conditions were as follows: after aging for 12 hours following assembly, charge-discharge tests were performed at different potentials. After activation at 3-4.3V and 0.1C rate for 3 cycles, the cells were then cycled 200 times at 2C to obtain their cycle specific capacity and capacity retention. The test results are shown in Table 1.

[0096] Table 1

[0097]

[0098] The data from Examples 1, 4, and 5 show that the synergistic effect of doping and coating is more conducive to improving the cycle stability of nickel-rich materials, while the performance improvement is not significant under medium and low nickel conditions.

[0099] As can be seen from the data results of the examples and comparative examples 1-3, the nickel-rich cathode precursor material provided by the present invention, if not doped with boron oxide, ensures the stability of the atoms in the material lattice; however, if zirconium is not doped in a gradient manner, the problems of cathode sphere cracking and cycle degradation cannot be solved; if zirconium is not doped and coated, it cannot isolate the electrolyte and protect the cathode material; that is, in this application, boron oxide and zirconium must work together to achieve internal stabilization of the atoms in the lattice and external isolation of the electrolyte, so as to achieve the purpose of long cycle life of the battery.

[0100] In summary, this invention achieves doping and coating of the cathode precursor in a single step, and is a bulk doping and coating process, thus preparing a nickel-rich material with simultaneous structural and interface modifications. By directly doping boron oxide ions into the precursor, and simultaneously coordinating with gradient doping and coating of zirconium, the boron oxide ions in the subsequently prepared cathode material react with the metal ions in the precursor to obtain boron metal oxides. This reduces the uneven distribution of stress on the material surface and decreases the generation of microcracks. The gradient doping of zirconium improves the atomic stability in the material lattice. Furthermore, zirconium coating avoids direct contact between the ternary precursor and the electrolyte, improving the cycle stability of the material and enhancing its safety and electrochemical performance.

[0101] The applicant declares that the above description is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention fall within the protection and disclosure scope of the present invention.

Claims

1. A nickel-rich cathode precursor, characterized in that, The nickel-rich cathode precursor includes a core and a coating layer covering the surface of the core; the core includes a cathode precursor matrix material and boron oxide and zirconium doped in the cathode precursor matrix material; the amount of zirconium doping gradually increases along the direction from the center of the core to the surface of the cathode precursor matrix material; the coating element in the coating layer includes zirconium. The total mass of the zirconium is 0.5% to 1% of the mass of the cathode precursor matrix material; The boron oxide doping amount is 500~5000ppm; The positive electrode precursor base material has a chemical formula of Ni a Co b Mn c (OH)2, 0.8≤a<1, b>0, c>0.

2. A method for preparing the nickel-rich cathode precursor as described in claim 1, characterized in that, The preparation method includes the following steps: A nickel-cobalt-manganese mixed salt solution, a boron source solution, a zirconium source solution, a precipitant solution, and a complexing agent solution are added in parallel to carry out the first stage of co-precipitation reaction. After the target particle size is reached, the addition of the nickel-cobalt-manganese mixed salt solution and the boron source solution is stopped, and the second stage of co-precipitation reaction is continued to obtain the nickel-rich cathode precursor. In the first stage of the coprecipitation reaction, the amount of zirconium source added gradually increases; The target particle size has a D50 of 9~10μm.

3. The method for preparing the nickel-rich cathode precursor according to claim 2, characterized in that, The concentration of the nickel-cobalt-manganese mixed salt solution is 50~150g / L.

4. The method for preparing the nickel-rich cathode precursor according to claim 2, characterized in that, The concentration of the boron source is 1~10 g / L.

5. The method for preparing the nickel-rich cathode precursor according to claim 2, characterized in that, The boron source includes boric acid.

6. The method for preparing the nickel-rich cathode precursor according to claim 2, characterized in that, The concentration of the zirconium source is 1~10 g / L.

7. The method for preparing the nickel-rich cathode precursor according to claim 2, characterized in that, The zirconium source includes zirconium salts.

8. The method for preparing the nickel-rich cathode precursor according to claim 2, characterized in that, The mass concentration of the precipitant solution is 20-50%.

9. The method for preparing the nickel-rich cathode precursor according to claim 2, characterized in that, The precipitant solution includes a liquid alkali solution.

10. The method for preparing the nickel-rich cathode precursor according to claim 2, characterized in that, The mass concentration of the complexing agent solution is 10-30%.

11. The method for preparing the nickel-rich cathode precursor according to claim 2, characterized in that, The complexing agent solution includes an aqueous ammonia solution.

12. The method for preparing the nickel-rich cathode precursor according to claim 2, characterized in that, The feed rate of the nickel-cobalt-manganese mixed salt solution is 6~10 L / h.

13. The method for preparing the nickel-rich cathode precursor according to claim 2, characterized in that, The feed rate of the boron source solution is 1~3 L / h.

14. The method for preparing the nickel-rich cathode precursor according to claim 2, characterized in that, The feed rate of the zirconium source solution is 0.3~1L / h.

15. The method for preparing the nickel-rich cathode precursor according to claim 2, characterized in that, The feed rate of the precipitant solution is 2~3 L / h.

16. The method for preparing the nickel-rich cathode precursor according to claim 2, characterized in that, The feed rate of the complexing agent solution is 0.6~1L / h.

17. The method for preparing the nickel-rich cathode precursor according to claim 2, characterized in that, The temperatures of the first-stage coprecipitation reaction and the second-stage coprecipitation reaction are each independently 30~80℃.

18. The method for preparing the nickel-rich cathode precursor according to claim 2, characterized in that, The pH values ​​of the first stage coprecipitation reaction and the second stage coprecipitation reaction are each independently 10~12.

19. The method for preparing the nickel-rich cathode precursor according to claim 2, characterized in that, The stirring rate for the first stage of the coprecipitation reaction and the stirring rate for the second stage of the coprecipitation reaction are each independently 100~500 r / min.

20. The method for preparing the nickel-rich cathode precursor according to claim 2, characterized in that, The preparation method includes the following steps: A nickel-cobalt-manganese mixed salt solution, a boric acid solution, a zirconium salt solution, a liquid alkali solution, and an ammonia solution are fed in parallel at a rate of 6-10 L / h, 1-3 L / h, 0.3-1 L / h, 2-3 L / h, and 0.6-1 L / h. The first stage of co-precipitation reaction is carried out at 30-80°C with a pH of 10-12 and a stirring rate of 100-500 r / min. After the target particle size D50 of 9-10 μm is reached, the addition of the nickel-cobalt-manganese mixed salt solution and boron source solution is stopped. The second stage of co-precipitation reaction is carried out at 30-80°C with a pH of 10-12 and a stirring rate of 100-500 r / min to obtain the nickel-rich cathode precursor. In the first stage of the co-precipitation reaction, the amount of zirconium source added gradually increases; the concentration of the nickel-cobalt-manganese mixed salt solution is 50~150g / L; the concentration of boric acid is 1~10g / L; the concentration of zirconium salt is 1~10g / L; the mass concentration of the liquid alkali solution is 20~50%; and the mass concentration of the ammonia solution is 10~30%.

21. A nickel-rich cathode material, characterized in that, The nickel-rich cathode material is obtained by mixing and sintering the nickel-rich cathode precursor as described in claim 1 with a lithium source.

22. A lithium-ion battery, characterized in that, The lithium-ion battery includes the nickel-rich cathode material as described in claim 21.

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