A positive electrode precursor and its preparation method and application

Abstract

The present disclosure provides a positive electrode precursor and its preparation method and application, wherein the positive electrode precursor comprises a core and a shell arranged on the surface of the core, wherein the chemical formula of the core is Ni x Co y Mn z M (1‑x‑y‑z) (OH)2, the chemical formula of the shell is Ni x Co y Mn z N b (OH) 2‑b , wherein, 0.83≤x≤0.95, 0.03≤y≤0.06, 0.02≤z≤0.11, M includes any one of W, Sb, Nb or Mo or a combination of at least two, N includes any one of F, Br, I or B or a combination of at least two, the shell is composed of flaky particles, and the shell has a porous structure. The precursor disclosed in the present invention has good consistency, achieving the unity of high capacity and long cycle, and at the same time, it is not easy to crack during the preparation process, thereby avoiding the deterioration of the performance of the positive electrode material.

Description

Technical Field

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

[0002] Ternary cathode materials, especially high nickel materials, have relatively high specific energy and working voltage, making them the most commercially promising cathode materials. However, excessive Ni content in the materials will also damage the structural stability of the materials while increasing the gram capacity of the materials. The highly active Ni generated during the charging process 4+ The reaction with the electrolyte will generate a NiO rock salt phase, which seriously damages the structure of the layered material, causing the collapse of the positive electrode material structure, and then inducing the dissolution of transition metal ions, phase transformation and lattice oxygen precipitation.

[0003] The uneven volume change (lattice parameter change) of high-nickel positive electrode materials during the charge and discharge process will lead to the formation of microcracks. The formed microcracks will expose new surfaces inside the particles, further accelerating structural decay. Especially when the nickel content exceeds 80%, the destructive effect of the cracks becomes more obvious, which to a certain extent limits the further application of high-nickel materials. At present, in response to the problems of high-nickel materials, modification methods such as doping and coating have emerged, but they all have some limitations.

[0004] The positive electrode material is made by adding lithium to the precursor and then calcining it at high temperature. Since the morphology of the primary grains and secondary particles changes little during the lithiation and calcination process, the physicochemical properties and electrochemical performance of the positive electrode material mainly depend on the morphology, microstructure, particle size, tap density, etc. of the precursor.

[0005] At present, high nickel precursors are mostly prepared by intermittent methods to produce special morphologies such as core-shell structures and radial shapes, but there are problems such as narrow particle size distribution (particle size distribution span <1.0) and low production capacity. In addition, when preparing large-particle precursors by intermittent methods, multiple kettle separations or concentrators are required to concentrate the precursors, but the production cycle is long and the cost is high, and the particles are prone to nucleation in the later stages of growth, resulting in poor product consistency. The core-shell structures disclosed in the prior art mostly use a nickel-deficient shell to wrap the nickel-rich particle core. Although it provides high capacity and reduces capacity attenuation to a certain extent, the uneven change in Ni concentration is prone to interface mismatch, which leads to premature rupture of the core-shell interface. In addition, cracking is also prone to occur during the preparation of large-particle high-nickel precursors, which will lead to deterioration of the performance of the positive electrode material. Summary of the Invention

[0006] 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.

[0007] The purpose of the present disclosure is to provide a cathode precursor, a preparation method and an application thereof. The precursor of the present disclosure has good consistency, achieving the unity of high capacity and long cycle life. At the same time, cracking is not easily generated during the preparation process, avoiding the deterioration of the performance of the cathode material.

[0008] To achieve this disclosure purpose, the present disclosure adopts the following technical solutions:

[0009] In the first aspect, an embodiment of the present disclosure provides a cathode precursor. The cathode precursor includes a core and a shell disposed on the surface of the core. The chemical formula of the core is Ni x Co y Mn z M (1-x-y-z) (OH)2, and the chemical formula of the shell is Ni x Co y Mn z N b (OH) 2-b , where 0.83 ≤ x ≤ 0.95, 0.03 ≤ y ≤ 0.06, 0.02 ≤ z ≤ 0.11, 0 < b ≤ 0.02, M includes any one or at least two combinations of W, Sb, Nb or Mo, N includes any one or at least two combinations of F, Br, I or B. The shell is composed of flaky particles and has a porous structure.

[0010] In the precursor of the embodiment of the present disclosure, the core is doped with high-valent metal elements, and the shell is doped with non-metal elements such as F, Br, I or B. The ionic radius of the high-valent metal element is comparable to that of the main element of the precursor, and it can be incorporated into the lamellar transition metal site to stabilize the material structure and reduce the internal diffusion impedance. The non-metal element replaces the oxygen site, can form a more stable ionic bond with the transition metal, and is more tightly combined, improving the crystallinity of the layered material. The composite element doping of the inner and outer layers compensates for the defects of single elements, and the good synergistic effect maximally improves the electrochemical performance and stability of the material.

[0011] In one embodiment, the shape of the core includes spherical and / or quasi-spherical.

[0012] In one embodiment, the median particle size D50 of the core is 2.5 - 4.5 μm, for example: 2.5 μm, 3 μm, 3.5 μm, 4 μm or 4.5 μm, etc.

[0013] In one embodiment, the shell is distributed in a porous radial manner along the radial direction of the core. The shell wraps around the surface of the core and is assembled radially by flaky primary particles perpendicular to the surface of the core. There are gaps between the flaky particles, forming a surface porous structure.

[0014] The disclosed embodiment controls a porous shell on the surface of a compact inner core in which primary particles grow radially in a sheet shape. The precursor is not easy to crack, and the porous radial structure is conducive to the entry of lithium sources during the sintering process, shortens the transmission path of lithium ions, and helps to reduce the accumulation of mechanical strain caused by the volume shrinkage of anisotropic monomers. While ensuring high capacity, it also improves the cycle performance, achieving the unity of high capacity and long cycle.

[0015] In one embodiment, the average pore volume of the positive electrode precursor is 0.02 to 0.06 cm 3 / g, for example: 0.02cm 3 / g, 0.03cm 3 / g, 0.04cm 3 / g, 0.05cm 3 / g or 0.06cm 3 / g, etc.

[0016] In one embodiment, the median particle size D50 of the positive electrode precursor is 10 to 14 μm, for example, 10 μm, 11 μm, 12 μm, 13 μm or 14 μm.

[0017] In one embodiment, (D90-D10) / D50 of the positive electrode precursor is 1.2-1.4, for example, 1.2, 1.25, 1.3, 1.35 or 1.4.

[0018] In one embodiment, the specific surface area of ​​the positive electrode precursor is 7 to 12 m 2 / g, for example: 7m 2 / g、8m 2 / g、9m 2 / g、10m 2 / g or 12m 2 / g, etc.

[0019] In one embodiment, the tap density of the positive electrode precursor is 1.8 to 2.0 g / cm 3 , for example: 1.8g / cm 3 , 1.85g / cm 3 , 1.9g / cm 3 , 1.95g / cm 3 or 2.0g / cm 3 wait.

[0020] In a second aspect, an embodiment of the present disclosure provides a method for preparing the positive electrode precursor as described in the first aspect, the preparation method comprising the following steps:

[0021] (1) mixing a nickel source, a cobalt source, and a manganese source with a solvent to obtain a ternary salt solution, mixing a high-valent metal source with an alkaline solution to obtain a high-valent metal salt solution, and mixing a doped non-metallic source with an alkaline solution to obtain a doped non-metallic solution;

[0022] (2) injecting the ternary salt solution, the high-valent metal salt solution, and the complexing agent into the bottom liquid in parallel to perform a one-step coprecipitation reaction to obtain a core slurry;

[0023] (3) The ternary salt solution, the doped non-metallic solution and the complexing agent are injected into the core slurry in parallel to perform a two-step co-precipitation reaction to obtain the positive electrode precursor.

[0024] The disclosed embodiments achieve the goal of continuously producing a core-shell structured high-nickel precursor by using the core slurry as the bottom liquid for the two-step co-precipitation. In addition to being the core, the core slurry also acts as a seed crystal, reducing the supersaturation of the system and avoiding the risk of nucleation. The continuous production method described in the disclosed embodiments overcomes some of the drawbacks of the existing intermittent method for preparing high-nickel precursors. The resulting precursor has a wider particle size distribution, and the positive electrode material has a higher compaction density after sintering, which greatly improves the energy density of the material.

[0025] In one embodiment, the high-valent metal source in step (1) includes any one of tungsten trioxide, antimony oxide, niobium monoxide or molybdenum oxide, or a combination of at least two thereof.

[0026] In one embodiment, the doping non-metal source includes any one of NaF, NaBr, NaI or sodium tetraborate, or a combination of at least two thereof.

[0027] In one embodiment, the alkaline solution comprises sodium hydroxide solution.

[0028] In one embodiment, the total molar concentration of metal ions in the ternary salt solution in step (1) is 1.5 to 2.5 mol / L, for example: 1.5 g / L, 1.8 mol / L, 2 mol / L, 2.2 mol / L or 2.5 mol / L.

[0029] In one embodiment, the molar concentration of the alkali solution is 6 to 12 mol / L, for example, 6 mol / L, 7 mol / L, 8 mol / L, 10 mol / L or 12 mol / L.

[0030] In one embodiment, the total mass concentration of the high-valent metal source in the high-valent metal salt solution is 10-20 g / L, for example, 10 g / L, 12 g / L, 15 g / L, 18 g / L or 20 g / L.

[0031] In one embodiment, the total mass concentration of the doped non-metallic source in the doped non-metallic solution is 5 to 10 g / L, for example, 5 g / L, 6 g / L, 7 g / L, 8 g / L, 9 g / L or 10 g / L.

[0032] In one embodiment, the complexing agent in step (2) includes aqueous ammonia.

[0033] In one embodiment, the molar concentration of the ammonia solution is 5 to 11 mol / L, for example, 5 mol / L, 6 mol / L, 8 mol / L, 10 mol / L or 11 mol / L.

[0034] In one embodiment, the mass concentration of aqueous ammonia in the base liquid is 1-5 g / L, for example, 1 g / L, 2 g / L, 3 g / L, 4 g / L or 5 g / L.

[0035] In one embodiment, the pH of the one-step co-precipitation reaction is 11-13, for example, 11, 11.5, 12, 12.5 or 13.

[0036] In one embodiment, the temperature of the one-step co-precipitation reaction is 55-75°C, for example, 55°C, 60°C, 65°C, 70°C or 75°C.

[0037] In one embodiment, the stirring speed of the one-step co-precipitation reaction is 400-500 rpm, for example, 400 rpm, 420 rpm, 450 rpm, 480 rpm or 500 rpm.

[0038] In one embodiment, the complexing agent in step (3) includes aqueous ammonia.

[0039] In one embodiment, the molar concentration of the ammonia solution is 5 to 11 mol / L, for example, 5 mol / L, 6 mol / L, 8 mol / L, 10 mol / L or 11 mol / L.

[0040] In one embodiment, the pH of the two-step co-precipitation reaction is 9-11, for example, 9, 9.5, 10, 10.5 or 11.

[0041] In one embodiment, the temperature of the two-step co-precipitation reaction is 55-75°C, for example, 55°C, 60°C, 65°C, 70°C or 75°C.

[0042] In one embodiment, the mass concentration of ammonia water in the two-step co-precipitation reaction is 3-10 g / L, for example, 3 g / L, 4 g / L, 5 g / L, 8 g / L or 10 g / L.

[0043] The conditions for the one-step co-precipitation and the two-step co-precipitation described in the embodiments of the present invention are significantly different. The introduced inner core slurry causes a sudden and drastic change in the system's supersaturation due to different reaction conditions. As the particles continue to grow, the primary particles on the inner core surface grow radially. Due to the increase in ammonia concentration and the decrease in pH, the primary particles are flaky. In addition, due to the reduced growth rate and incomplete crystallization, a loose and porous structure is formed between the primary particles.

[0044] In one embodiment, the stirring speed of the two-step co-precipitation reaction is 150-250 rpm, for example, 150 rpm, 180 rpm, 200 rpm, 220 rpm or 250 rpm.

[0045] The two-step co-precipitation described in the embodiment of the present disclosure prolongs the residence time of the particles in the kettle at a low stirring speed, and can also reduce problems such as cracking of the particles.

[0046] In one embodiment, the ammonia concentration of the two-step co-precipitation reaction is greater than the ammonia concentration of the one-step co-precipitation reaction.

[0047] In a third aspect, an embodiment of the present disclosure provides a positive electrode material, which is obtained by mixing and sintering the positive electrode precursor as described in the first aspect with a lithium source.

[0048] In one embodiment, the sintering includes one-step sintering and two-step sintering.

[0049] The positive electrode material described in the embodiment of the present disclosure is obtained by lithiation of a porous radial high-nickel precursor with a core-shell structure, followed by a low-temperature pre-sintering and a secondary high-temperature calcination. The high-valent metal elements in the core pin the particle boundaries to reduce mutual diffusion and minimize particle coarsening, thereby stabilizing the internal structure and inhibiting the formation of microcracks; the non-metallic elements in the outer shell can inhibit the formation of rock salt phase, reduce the dissolution of transition metal elements and the precipitation of lattice oxygen, and improve the cycle stability; the main components of the core and the outer shell are basically the same, avoiding the interface mismatch phenomenon caused by the difference in the concentration of the main elements.

[0050] In one embodiment, the one-step sintering temperature is 500-550°C, for example, 500°C, 510°C, 520°C, 530°C or 550°C.

[0051] In one embodiment, the one-step sintering time is 3 to 5 hours, for example, 3 hours, 3.5 hours, 4 hours, 4.5 hours or 5 hours.

[0052] In one embodiment, the temperature of the second-step sintering is 750-980°C, for example, 750°C, 780°C, 800°C, 900°C or 950°C.

[0053] In one embodiment, the two-step sintering time is 10 to 15 hours, for example, 10 hours, 11 hours, 12 hours, 13 hours, 14 hours or 15 hours.

[0054] In a fourth aspect, an embodiment of the present disclosure provides a lithium-ion battery, wherein the lithium-ion battery comprises the positive electrode material as described in the third aspect.

[0055] Compared with the prior art, the present disclosure has the following beneficial effects:

[0056] (1) The present invention controls the change in supersaturation during the co-precipitation process to prepare a precursor, thereby regulating the formation of a porous shell with primary particles growing radially in a sheet shape on the surface of a compact inner core, so that the prepared high-nickel precursor is not easy to crack; the porous radial structure is conducive to the entry of lithium source during the sintering process, shortens the transmission path of lithium ions, and is conducive to reducing the accumulation of mechanical strain caused by the volume shrinkage of anisotropic monomers, thereby ensuring high capacity and improving the cycle performance, thereby achieving the unity of high capacity and long cycle.

[0057] (2) The positive electrode material disclosed in the present invention is obtained by lithiation of a porous radial high-nickel precursor with a core-shell structure, followed by a low-temperature pre-sintering and a secondary high-temperature calcination. The high-valent metal elements in the core pin the particle boundaries to reduce mutual diffusion and minimize particle coarsening, thereby stabilizing the internal structure and inhibiting the formation of microcracks; the non-metallic elements in the shell can inhibit the formation of rock salt phase, reduce the dissolution of transition metal elements and the precipitation of lattice oxygen, and improve the cycle stability; the main components of the core and shell are basically the same, avoiding the interface mismatch phenomenon caused by the difference in the concentration of the main elements.

[0058] (3) The precursor prepared by the present disclosure has a wide particle size distribution and a high average pore volume, its (D90-D10) / D50 value is above 1.2, and the average pore volume is above 0.02 cm3 / g; the positive electrode material prepared by using the precursor described in the present disclosure has a high capacity and good cycle performance and rate performance. At an average voltage of 3.5V, the initial discharge specific capacity at 0.33C can reach above 210.8 mAh / g, the first coulombic efficiency at 0.33C can reach above 90.8%, and the capacity retention rate after 100 cycles at 1C can reach above 93.1%.

[0059] Still other aspects will become apparent upon reading and understanding the accompanying drawings and detailed description. BRIEF DESCRIPTION OF THE DRAWINGS

[0060] 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.

[0061] Figure 1 This is an SEM image of the positive electrode precursor described in Example 1 of the present disclosure.

[0062] Figure 2 This is a SEM cross-sectional view of the positive electrode precursor described in Example 1 of the present disclosure.

[0063] Figure 3 This is an SEM image of the positive electrode precursor described in Comparative Example 1.

[0064] Figure 4 This is a SEM cross-sectional view of the positive electrode precursor described in Comparative Example 1.

[0065] Figure 5 This is a comparison chart of the capacity retention rates of the positive electrode materials obtained from the positive electrode precursors described in Example 1 and Comparative Example 1.

[0066] Figure 6 This is a comparison chart of the cycle performance of the positive electrode materials obtained from the positive electrode precursors described in Example 1 and Comparative Example 1.

[0067] Figure 7 This is a comparison chart of the rate performance of the positive electrode materials obtained from the positive electrode precursors described in Example 1 and Comparative Example 1. DETAILED DESCRIPTION

[0068] The technical solution of the present disclosure 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 disclosure and should not be regarded as specific limitations of the present disclosure.

[0069] Example 1

[0070] This embodiment provides a positive electrode precursor, and the preparation method of the positive electrode precursor is as follows:

[0071] (1) Nickel sulfate, cobalt sulfate, and manganese sulfate were prepared into a 1.5 mol / L ternary salt solution A at a metal molar ratio of 83.8:5.7:10.5. 1.08 kg of tungsten trioxide was dissolved in 75 L of 10 mol / L alkali solution to form a mixed solution B. 620 g of NaF was added to 75 L of 10 mol / L alkali solution to form a mixed solution C.

[0072] (2) Add 1 / 3 volume of pure water to the reactor I, add ammonia water to adjust the ammonia concentration to 1.5g / L, add alkali solution to adjust the pH to 11-11.5, heat the reactor to 55℃, start stirring, set the stirring speed to 400rpm, pump the ternary salt solution A at a flow rate of 5L / h, the mixed solution B at a flow rate of 1.5L / h and the 5mol / L ammonia solution at a flow rate of 0.75L / h into the reactor I through a peristaltic pump for reaction, test the particle size once every 3h with a particle size analyzer, keep other conditions unchanged, adjust the pH to 11.5±0.05 to maintain the dynamic balance of nucleation and growth, repeat this process continuously, control the particle size D50 to fluctuate between 2.5 and 4.5μm, open the overflow after the reactor is full, and continuously overflow to obtain Ni0.83 Co 0.056 Mn 0.104 W 0.01 (OH)2 core slurry D;

[0073] (3) Slurry D accounting for 1 / 3 of the volume of reactor II was pumped into the reactor by a peristaltic pump, and then ternary salt solution A at 20 L / h, mixed solution C at 6 L / h and 5 mol / L ammonia solution at 3 L / h were pumped into the bottom of reactor II by a peristaltic pump to continue the reaction. The pH was adjusted to 9-9.5, the ammonia concentration to 3-5 g / L, the temperature to 60 ° C, the stirring speed to 250 rpm, and the Ni 0.83 Co 0.056 Mn 0.104 W 0.01 The loose and porous Ni 0.83 Co 0.056 Mn 0.104 F 0.01 (OH) 1.99 The shell is tested for particle size every 3 hours with a particle size analyzer. After the reactor is full, the overflow is opened. When the particle size D50 reaches 10 μm, the slurry D is intermittently pumped into the bottom of the reactor II by a peristaltic pump. When the particle size is stable, the overflow material is collected to obtain a porous radial high-nickel precursor slurry with a core-shell structure. The slurry is centrifuged, washed, dried, sieved, deironed, and packaged to obtain the positive electrode precursor.

[0074] The SEM image of the positive electrode precursor is as follows Figure 1 As shown, the SEM cross-sectional view of the positive electrode precursor is as shown Figure 2 shown.

[0075] Example 2

[0076] This embodiment provides a positive electrode precursor, and the preparation method of the positive electrode precursor is as follows:

[0077] (1) nickel sulfate, cobalt sulfate, and manganese sulfate were prepared into a 2 mol / L ternary salt solution A at a metal molar ratio of 91.3:7:1.7, 3.5 kg of antimony oxide was dissolved in 100 L of 8 mol / L alkali solution to form a mixed solution B, and 2.24 kg of NaBr was added to 100 L of 8 mol / L alkali solution to form a mixed solution C;

[0078] (2) Add 1 / 2 volume of pure water to the reactor I, add ammonia water to adjust the ammonia concentration to 4.5g / L, add alkali solution to adjust the pH to 12.5-13, heat the reactor to 75℃, start stirring, set the stirring speed to 500rpm, pump the ternary salt solution A at a flow rate of 10L / h, the mixed solution B at a flow rate of 5L / h and the 8mol / L ammonia solution at a flow rate of 2L / h into the reactor I through a peristaltic pump for reaction, test the particle size once every 3h with a particle size analyzer, keep other conditions unchanged, adjust the pH to 12.5±0.05 to maintain the dynamic balance of nucleation and growth, repeat this process continuously, control the particle size D50 to fluctuate between 2.5 and 4.5μm, open the overflow after the reactor is full, and continuously overflow to obtain Ni 0.90 Co 0.069 Mn 0.016 Sb 0.015 (OH)2 core slurry D;

[0079] (3) Slurry D accounting for 1 / 2 of the volume of reactor II was pumped into the reactor by a peristaltic pump, and then ternary salt solution A at 40 L / h, mixed solution C at 20 L / h and 8 mol / L ammonia solution at 8 L / h were pumped into the bottom of reactor II by a peristaltic pump to continue the reaction. The pH was adjusted to 10-10.5, the ammonia concentration to 6-8 g / L, the temperature to 65 ° C, the stirring speed to 200 rpm, and the Ni 0.90 Co 0.069 Mn 0.016 Sb 0.015 The loose and porous Ni 0.90 Co 0.069 Mn 0.016 Br 0.015 (OH) 1.985 The shell is tested for particle size every 3 hours with a particle size analyzer. After the reactor is full, the overflow is opened. When the particle size D50 reaches 12 μm, the slurry D is intermittently pumped into the bottom of the reactor II by a peristaltic pump. When the particle size is stable, the overflow material is collected to obtain a porous radial high-nickel precursor slurry with a core-shell structure. The slurry is centrifuged, washed, dried, sieved, deironed, and packaged to obtain the positive electrode precursor.

[0080] Example 3

[0081] This embodiment provides a positive electrode precursor, and the preparation method of the positive electrode precursor is as follows:

[0082] (1) nickel sulfate, cobalt sulfate, and manganese sulfate were prepared into a 2.5 mol / L ternary salt solution A at a metal molar ratio of 95:3:2, 1.18 kg of niobium monoxide was dissolved in 90 L of 12 mol / L alkali solution to form a mixed solution B, and 4.23 kg of NaI was added to 90 L of 12 mol / L alkali solution to form a mixed solution C;

[0083] (2) Add 2 / 3 volume of pure water to the reactor I, add ammonia water to adjust the ammonia concentration to 3g / L, add alkali solution to adjust the pH to 11.5-12, heat the reactor to 60℃, start stirring, set the stirring speed to 450rpm, pump the ternary salt solution A at a flow rate of 15L / h, the mixed solution B at a flow rate of 6.3L / h and the 11mol / L ammonia solution at a flow rate of 2L / h into the reactor I through a peristaltic pump for reaction, test the particle size once every 3h with a particle size analyzer, keep other conditions unchanged, adjust the pH to 11.8±0.05 to maintain the dynamic balance of nucleation and growth, repeat this process continuously, control the particle size D50 to fluctuate between 2.5 and 4.5μm, open the overflow after the reactor is full, and continuously overflow to obtain Ni 0.93 Co 0.03 Mn 0.02 Nb 0.02 (OH)2 core slurry D;

[0084] (3) Slurry D, which accounts for 2 / 3 of the volume, was pumped into the reactor II by a peristaltic pump. Then, ternary salt solution A was pumped at 60 L / h, mixed solution C was pumped at 25 L / h, and 11 mol / L ammonia solution was pumped at 8 L / h into the bottom of the reactor II by a peristaltic pump to continue the reaction. The pH was adjusted to 10.5-11, the ammonia concentration was adjusted to 8-10 g / L, the temperature was adjusted to 75 °C, the stirring speed was adjusted to 150 rpm, and the Ni 0.93 Co 0.03 Mn 0.02 Nb 0.02 The loose and porous Ni 0.93 Co 0.03 Mn 0.02 I 0.02 (OH) 1.98 The shell is tested for particle size every 3 hours with a particle size analyzer. After the reactor is full, the overflow is opened. When the particle size D50 reaches 14 μm, the slurry D is intermittently pumped into the bottom of the reactor II by a peristaltic pump. When the particle size is stable, the overflow material is collected to obtain a porous radial high-nickel precursor slurry with a core-shell structure. The slurry is centrifuged, washed, dried, sieved, deironed, and packaged to obtain the positive electrode precursor.

[0085] Example 4

[0086] This embodiment provides a positive electrode precursor, and the preparation method of the positive electrode precursor is as follows:

[0087] (1) nickel sulfate, cobalt sulfate, and manganese sulfate were prepared into a 1.8 mol / L ternary salt solution A at a metal molar ratio of 96:2.4:1.6, 475 g of molybdenum trioxide was dissolved in 100 L of 6 mol / L alkali solution to form a mixed solution B, and 2.8 kg of sodium tetraborate was added to 100 L of 6 mol / L alkali solution to form a mixed solution C;

[0088] (2) Add 1 / 2 volume of pure water to the reactor I, add ammonia water to adjust the ammonia concentration to 3.5g / L, add alkali solution to adjust the pH to 12-12.5, heat the reactor to 65℃, start stirring, set the stirring speed to 480rpm, pump the ternary salt solution A at a flow rate of 20L / h, the mixed solution B at a flow rate of 12L / h and the 10mol / L ammonia solution at a flow rate of 2.5L / h into the reactor I through a peristaltic pump for reaction, test the particle size once every 3h with a particle size analyzer, keep other conditions unchanged, adjust the pH to 12.2±0.05 to maintain the dynamic balance of nucleation and growth, repeat this process continuously, control the particle size D50 to fluctuate between 2.5 and 4.5μm, open the overflow after the reactor is full, and continuously overflow to obtain Ni 0.95 Co 0.024 Mn 0.016 Mo 0.01 (OH)2 core slurry D;

[0089] (3) Slurry D, which accounts for 2 / 3 of the volume, was pumped into the reactor II by a peristaltic pump. Then, ternary salt solution A was pumped at 50 L / h, mixed solution C was pumped at 30 L / h, and 10 mol / L ammonia solution was pumped at 4.5 L / h into the bottom of the reactor II by a peristaltic pump to continue the reaction. The pH was adjusted to 9.5-10, the ammonia concentration to 5-7 g / L, the temperature to 60 ° C, the stirring speed to 180 rpm, and the Ni 0.95 Co 0.024 Mn 0.016 Mo 0.01 The loose and porous Ni 0.95 Co 0.024 Mn 0.016 B 0.02 (OH) 1.98 The shell is tested for particle size every 3 hours with a particle size analyzer. After the reactor is full, the overflow is opened. When the particle size D50 reaches 10 μm, the slurry D is intermittently pumped into the bottom of the reactor II by a peristaltic pump. When the particle size is stable, the overflow material is collected to obtain a porous radial high-nickel precursor slurry with a core-shell structure. The slurry is centrifuged, washed, dried, sieved, deironed, and packaged to obtain the positive electrode precursor.

[0090] Example 5

[0091] The only difference between this embodiment and embodiment 1 is that the concentration of ammonia water in the two-step co-precipitation in step (2) is 2 g / L, and the other conditions and parameters are exactly the same as those in embodiment 1.

[0092] Example 6

[0093] The only difference between this embodiment and embodiment 1 is that the concentration of ammonia water in the two-step co-precipitation in step (2) is 12 g / L, and the other conditions and parameters are exactly the same as those in embodiment 1.

[0094] Example 7

[0095] The only difference between this embodiment and embodiment 1 is that the pH of the two-step co-precipitation in step (2) is 8.5, and the other conditions and parameters are exactly the same as those in embodiment 1.

[0096] Example 8

[0097] The only difference between this embodiment and embodiment 1 is that the pH of the two-step co-precipitation in step (2) is 11.5, and the other conditions and parameters are exactly the same as those in embodiment 1.

[0098] Comparative Example 1

[0099] This comparative example provides a positive electrode precursor, and the preparation method of the positive electrode precursor is as follows:

[0100] (1) Nickel sulfate, cobalt sulfate, and manganese sulfate were prepared into a 1.5 mol / L ternary salt solution A at a metal molar ratio of 83:6:11, 10 mol / L NaOH solution was directly used as the alkali solution B, and 5 mol / L ammonia water was used as the complexing agent C;

[0101] (2) Add 1 / 3 volume of pure water to the reactor I, add ammonia water to adjust the ammonia concentration to 1.5g / L, add alkali solution to adjust the pH to 11-11.5, raise the temperature in the reactor to 55°C, start stirring, set the stirring speed to 400rpm, pump the ternary salt solution A at a flow rate of 5L / h, alkali solution B at a flow rate of 1.5L / h and complexing agent C at a flow rate of 0.75L / h into the reactor I through a peristaltic pump for reaction, test the particle size once every 3 hours with a particle size analyzer, keep other conditions unchanged, adjust the pH to 11.5±0.05 to maintain the dynamic balance of nucleation and growth, repeat this process continuously, control the particle size D50 to fluctuate between 2.5 and 4.5μm, open the overflow after the reactor is full, and continuously overflow to obtain seed crystal D;

[0102] (3) A seed crystal D accounting for 1 / 3 of the volume of the reactor II is pumped into the reactor II by a peristaltic pump, and then the ternary salt solution A is pumped into the bottom of the reactor II at a rate of 20 L / h, the alkali solution B is pumped into the bottom of the reactor II at a rate of 6 L / h, and the complexing agent C is pumped into the bottom of the reactor II by a peristaltic pump to continue the reaction. The pH is adjusted to 9-9.5, the ammonia concentration is adjusted to 3-5 g / L, the temperature is adjusted to 60 ° C, and the stirring speed is adjusted to 250 rpm. The particle size is tested once every 3 hours with a particle size analyzer. After the reactor is full, the overflow is opened. When the particle size D50 reaches 10 μm, the slurry D is intermittently pumped into the bottom of the reactor II by a peristaltic pump. When the particle size is stable, the overflow material is collected to obtain a conventional high-nickel precursor slurry. The slurry is centrifuged, washed, dried, sieved, deironed, and packaged to obtain a conventional high-nickel precursor, whose chemical formula is Ni 0.83 Co 0.06 Mn 0.11 (OH)2.

[0103] The SEM image of the positive electrode precursor is as follows Figure 3As shown, the SEM cross-sectional view of the positive electrode precursor is as shown Figure 4 shown.

[0104] Comparative Example 2

[0105] The only difference between this comparative example and Example 1 is that both the non-metallic element and the high-valent metal element are doped in the core, and the other conditions and parameters are exactly the same as those in Example 1.

[0106] Comparative Example 3

[0107] The only difference between this comparative example and Example 1 is that both the non-metallic element and the high-valent metal element are doped in the outer layer, and the other conditions and parameters are exactly the same as those in Example 1.

[0108] Comparative Example 4

[0109] The only difference between this comparative example and Example 1 is that the outer shell is doped with Cl, and the other conditions and parameters are exactly the same as those in Example 1.

[0110] Performance testing:

[0111] (1) The precursors prepared in the examples and comparative examples were tested. The test results are shown in Table 1:

[0112] Table 1

[0113]

[0114]

[0115] (2) The precursors obtained in the embodiment and the comparative example were mixed with lithium hydroxide in a molar ratio of 1:1.08 and placed in a tube furnace. In an oxygen atmosphere, the temperature was raised to 550°C at 5°C / min and kept warm for 4h, then raised to 850°C at 3°C / min and kept warm for 11h. The mixture was then cooled to room temperature and ground to obtain a high-nickel positive electrode material. The positive electrode material, carbon black conductive agent Super P and binder polyvinylidene chloride were dissolved in N-methylpyrrolidone in a mass ratio of 92:5:3, stirred to form a slurry, and coated on aluminum foil. The slurry was dried at 110°C to obtain a positive electrode sheet. The metal lithium sheet was then used as the negative electrode, and a CR2430 button battery assembly was selected to assemble a battery. A charge and discharge comparison test was carried out under the conditions of 2.7-4.3V and 0.33C. The test results are shown in Table 2:

[0116] Table 2

[0117]

[0118]

[0119] As can be seen from Table 1-2 and Examples 1-4, the precursor disclosed in the present invention has a porous radial core-shell structure with primary particles on the surface arranged in an orderly lamellar shape, a large average pore volume, and the 0.33C initial discharge specific capacity of the positive electrode material can reach more than 210.8mAh / g, the 0.33C first coulombic efficiency can reach more than 90.8%, and the capacity retention rate after 100 cycles at 1C can reach more than 93.1%.

[0120] By comparing Example 1 and Examples 5-6, it can be seen that in the preparation process of the positive electrode precursor described in the present invention, the ammonia concentration of the two-step co-precipitation reaction will affect its performance. The ammonia concentration of the two-step co-precipitation reaction is controlled at 3-10 g / L and greater than the ammonia concentration of the one-step co-precipitation reaction, and the precursor has better performance. If the ammonia concentration of the two-step co-precipitation reaction is too high, the average pore volume and specific surface area of ​​the precursor will decrease (caused by the primary particles becoming coarser and tightly bound), and the capacity and cycle performance of the obtained positive electrode material will deteriorate significantly. If the ammonia concentration of the two-step co-precipitation reaction is too low, the average pore volume and specific surface area of ​​the precursor will decrease (caused by the primary particles becoming finer and tightly bound), and the capacity of the obtained positive electrode material will decrease slightly, but the cycle performance will deteriorate significantly.

[0121] By comparing Example 1 and Examples 7-8, it can be seen that in the preparation process of the positive electrode precursor described in the present disclosure, the pH of the two-step co-precipitation reaction will affect its performance. The pH of the two-step co-precipitation reaction is controlled at 9-11 and lower than the pH of the one-step co-precipitation reaction, and the precursor has better performance. If the pH of the two-step co-precipitation reaction is too high, the average pore volume and specific surface area of ​​the precursor decrease (caused by the primary particles becoming thinner but tightly bound), the capacity of the obtained positive electrode material decreases slightly, but the cycle performance deteriorates significantly. If the pH of the two-step co-precipitation reaction is too low, the average pore volume and specific surface area of ​​the precursor are both reduced (caused by the primary particles becoming thicker and larger and tightly bound), the capacity of the obtained positive electrode material decreases significantly, and the cycle performance deteriorates slightly.

[0122] The comparison of the capacity retention rate of the positive electrode material obtained by the positive electrode precursor of Example 1 and Comparative Example 1 is shown in the figure below. Figure 5 As shown in the figure, the cycle performance comparison of the positive electrode material obtained by the positive electrode precursor of Example 1 and Comparative Example 1 is shown in Figure 6 As shown in the figure, the rate performance comparison of the positive electrode material obtained by the positive electrode precursor of Example 1 and Comparative Example 1 is shown in Figure 7 As shown, by comparing Example 1 and Comparative Example 1, the present invention regulates the formation of a porous shell in which primary particles grow radially in a sheet shape on the surface of a compact inner core. The precursor is not easy to crack, and the porous radial structure is conducive to the entry of lithium source during the sintering process, shortens the transmission path of lithium ions, and is conducive to reducing the accumulation of mechanical strain caused by the volume shrinkage of anisotropic monomers. While ensuring high capacity, it also improves the cycle performance, achieving the unity of high capacity and long cycle.

[0123] By comparing Example 1 with Comparative Examples 2-3, it can be seen that compared with the doping in the entire core or the entire shell, the precursor of the present invention, which is doped with a high-valent metal in the core and a non-metal in the outer layer, has a higher average pore volume, and the prepared positive electrode material has a higher initial discharge capacity and initial coulombic efficiency, and has a higher capacity retention rate after 100 cycles at 1C.

[0124] From the comparison between Example 1 and Comparative Example 4, it can be seen that the shell doping element of the precursor disclosed in the present invention must be F, Br, I or B. Compared with the surface doping of Cl element, the precursor disclosed in the present invention has a higher average pore volume, and the initial discharge capacity and initial coulombic efficiency of the prepared positive electrode material are greatly improved, and the capacity retention rate after 100 cycles at 1C is significantly improved.

Claims

1. A positive electrode precursor, comprising a core and a shell disposed on the surface of the core, wherein the chemical formula of the core is Ni x Co y Mn z M (1-x-y-z) (OH)2, the chemical formula of the shell is Ni x Co y Mn z N b (OH) 2-b ,in, 0.83 ≤ x ≤ 0.95, 0.03 ≤ y ≤ 0.06, 0.02 ≤ z ≤ 0.11, 0 < b ≤ 0.02, M includes any one or a combination of at least two of W, Sb, Nb or Mo, N includes any one or a combination of at least two of F, Br, I or B, the outer shell is composed of flaky particles, the outer shell has a porous structure, and the outer shell is distributed in a porous radial pattern along the radial direction of the inner core.

2. The cathode precursor according to claim 1, wherein The shape of the inner core includes spherical and / or quasi-spherical.

3. The cathode precursor according to claim 1, wherein The median particle size D50 of the inner core is 2.5 - 4.5 μm.

4. The cathode precursor according to claim 1, wherein The average pore volume of the positive electrode precursor is 0.02 to 0.06 cm 3 / g.

5. The cathode precursor according to claim 1, wherein The median particle size D50 of the positive electrode precursor is 10 - 14 μm.

6. The cathode precursor according to claim 1, wherein (D90 - D10) / D50 of the positive electrode precursor is 1.2 - 1.

4.

7. The cathode precursor according to claim 1, wherein The specific surface area of ​​the positive electrode precursor is 7 to 12 m 2 / g.

8. The cathode precursor according to claim 1, wherein The tap density of the positive electrode precursor is 1.8 to 2.0 g / cm 3 .

9. A method for preparing a positive electrode precursor according to any one of claims 1 - 8, the preparation method comprising the following steps: (1) Mixing a nickel source, a cobalt source and a manganese source with a solvent to obtain a ternary salt solution, mixing a high-valent metal source with an alkali solution to obtain a high-valent metal salt solution, and mixing a doped non-metal source with an alkali solution to obtain a doped non-metal solution; (2) Injecting the ternary salt solution, the high-valent metal salt solution and a complexing agent into a bottom liquid in a co-current manner to perform a one-step co-precipitation reaction to obtain an inner core slurry; (3) Injecting the ternary salt solution, the doped non-metal solution and a complexing agent into the inner core slurry in a co-current manner to perform a two-step co-precipitation reaction to obtain the positive electrode precursor.

10. The preparation method according to claim 9, wherein The high-valent metal source in step (1) includes any one or a combination of at least two of tungsten trioxide, antimony oxide, niobium monoxide or molybdenum oxide.

11. The preparation method according to claim 9, wherein The doped non-metal source includes any one or a combination of at least two of NaF, NaBr, NaI or sodium tetraborate.

12. The preparation method according to claim 9, wherein The alkali solution includes a sodium hydroxide solution.

13. The preparation method according to claim 9, wherein The total molar concentration of metal ions in the ternary salt solution in step (1) is 1.5 - 2.5 mol / L.

14. The preparation method according to claim 9, wherein The molar concentration of the alkali solution is 6 - 12 mol / L.

15. The preparation method according to claim 9, wherein The total mass concentration of the high-valent metal source in the high-valent metal salt solution is 10 - 20 g / L.

16. The preparation method according to claim 9, wherein The total mass concentration of the doped non-metal source in the doped non-metal solution is 5 - 10 g / L.

17. The preparation method according to claim 9, wherein The complexing agent in step (2) includes ammonia water.

18. The preparation method according to claim 17, wherein The molar concentration of the ammonia water is 5 - 11 mol / L.

19. The preparation method according to claim 9, wherein The mass concentration of ammonia water in the bottom liquid is 1 - 5 g / L.

20. The preparation method according to claim 9, wherein The pH of the one-step co-precipitation reaction is 11 - 13.

21. The preparation method according to claim 9, wherein The temperature of the one-step co-precipitation reaction is 55 - 75 °C.

22. The preparation method according to claim 9, wherein The stirring speed of the one-step co-precipitation reaction is 400 - 500 rpm.

23. The preparation method according to claim 9, wherein The complexing agent in step (3) includes ammonia water.

24. The preparation method according to claim 23, wherein The molar concentration of the ammonia water is 5 - 11 mol / L.

25. The preparation method according to claim 9, wherein The pH of the two-step co-precipitation reaction is 9 - 11.

26. The preparation method according to claim 9, wherein The temperature of the two-step co-precipitation reaction is 55 - 75 °C.

27. The preparation method according to claim 9, wherein The mass concentration of ammonia water in the two-step co-precipitation reaction is 3 - 10 g / L.

28. The preparation method according to claim 9, wherein The stirring speed of the two-step co-precipitation reaction is 150 - 250 rpm.

29. The preparation method according to claim 9, wherein The ammonia water concentration in the two-step co-precipitation reaction > the ammonia water concentration in the one-step co-precipitation reaction.

30. A positive electrode material, the positive electrode material is obtained by mixing and sintering a positive electrode precursor according to any one of claims 1 - 8 with a lithium source.

31. The positive electrode material according to claim 30, wherein The sintering includes one-step sintering and two-step sintering.

32. The positive electrode material according to claim 31, wherein The temperature of the one-step sintering is 500-550°C.

33. The positive electrode material according to claim 31, wherein The one-step sintering time is 3 to 5 hours.

34. The positive electrode material according to claim 31, wherein The temperature of the second-step sintering is 750-980°C.

35. The cathode material according to claim 31, wherein The time of the two-step sintering is 10 to 15 hours.

36. A lithium ion battery comprising the positive electrode material according to any one of claims 30 to 35.

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