Lithium nickel cobalt manganese oxide positive electrode material and preparation method thereof, solid-state battery and electric equipment

Abstract

The invention relates to the technical field of batteries, in particular to a nickel cobalt lithium manganate positive electrode material and a preparation method thereof, a solid-state battery and electric equipment. The chemical general formula of the nickel cobalt lithium manganate positive electrode material is LiaNixCoyMnzO2, a is greater than or equal to 0.9 and less than or equal to 1.2, x is greater than 0 and less than or equal to 1, and x + y + z = 1; the nickel cobalt lithium manganate positive electrode material comprises secondary particles, the secondary particles are formed by agglomeration of primary particles, the average equivalent diameter d1 of the primary particles meets the condition that d1 is larger than or equal to 400 nm and smaller than or equal to 1 micron, and Dv50 of the secondary particles meets the condition that Dv50 is larger than or equal to 3 microns and smaller than or equal to 8.5 microns; the porosity phi of the nickel cobalt lithium manganate positive electrode material is not more than 10%, the specific surface area S is not less than 0.7 m < 2 > / g, and the compaction density rho is not less than 3.35 g / cm < 3 >. The average equivalent diameter of primary particles and the Dv50 of secondary particles of the nickel cobalt lithium manganate positive electrode material are appropriate, and the nickel cobalt lithium manganate positive electrode material has low porosity, high specific surface area and high compaction density.

Description

Technical Field

[0001] This invention relates to the field of battery technology, and more specifically, to a lithium nickel cobalt manganese oxide cathode material and its preparation method, a solid-state battery, and an electrical device thereof. Background Technology

[0002] With the rapid development of the electric vehicle and large-scale energy storage markets, higher demands are being placed on the energy density, safety, and cycle life of lithium-ion batteries. All-solid-state batteries, due to their use of non-flammable solid electrolytes, are expected to fundamentally solve the safety hazards of traditional liquid lithium batteries and are also expected to be compatible with metallic lithium anodes, thus achieving higher energy density, and are considered the preferred next-generation energy storage technology. However, the transition from a liquid to a solid system is not a simple material replacement; the positive electrode side faces significant challenges. In traditional liquid lithium batteries, the positive electrode sheet needs to maintain a porosity of 10%-20%. These pores are filled by the liquid electrolyte, forming continuous ion transport channels to ensure rapid lithium-ion conduction between and within the positive electrode active material particles.

[0003] However, in solid-state batteries, the solid electrolyte is mostly a rigid ceramic or sulfide material with poor fluidity, unable to penetrate the tiny pores inside the cathode material like a liquid electrolyte. This causes the pores inside the cathode material to become "dead zones," interrupting ion transport paths and significantly increasing interfacial ion conduction impedance. Simultaneously, excessively high porosity reduces the effective contact area between cathode active material particles and between the active material and solid electrolyte particles, further increasing interfacial impedance, leading to increased battery polarization, insufficient capacity utilization, and decreased rate performance. Secondly, high porosity directly results in a low compaction density of the cathode electrode, severely limiting the battery's volumetric energy density and preventing the full realization of the theoretical advantages of solid-state batteries.

[0004] Therefore, developing a novel cathode material that can simultaneously meet the three key requirements of low porosity, high specific surface area, and high compaction density is crucial for promoting the development of solid-state battery technology.

[0005] In view of this, the present invention is hereby proposed. Summary of the Invention

[0006] One objective of this invention is to provide a lithium nickel cobalt manganese oxide cathode material to address the technical problems in solid-state batteries caused by the discontinuous ion conduction pathway due to excessive porosity of high-nickel ternary materials, the coexistence of low specific surface area and interparticle porosity due to traditional single-crystalization processes, and the limitation on volumetric energy density due to insufficient material compaction density. The present invention provides a lithium nickel cobalt manganese oxide cathode material with a primary particle average equivalent diameter and a secondary particle D... v 50 is suitable, with low porosity, high specific surface area and high compaction density.

[0007] Another objective of this invention is to provide a method for preparing lithium nickel cobalt manganese oxide cathode material.

[0008] Another object of the present invention is to provide a solid-state battery.

[0009] Another object of the present invention is to provide an electrical device.

[0010] In order to achieve the above-mentioned objectives of the present invention, the following technical solution is adopted: A lithium nickel cobalt manganese oxide cathode material, wherein the general chemical formula of the lithium nickel cobalt manganese oxide cathode material is Li. a Ni x Co y Mn z O2, where 0.9≤a≤1.2, 0<x≤1, x+y+z=1; the lithium nickel cobalt manganese oxide cathode material includes secondary particles, which are formed by the agglomeration of primary particles. The average equivalent diameter d1 of the primary particles satisfies: 400nm≤d1≤1μm, and the D of the secondary particles... v 50 satisfies: 3μm≤D v The porosity φ of the lithium nickel cobalt manganese oxide cathode material is ≤8.5μm, and the specific surface area S is ≥0.7m². 2 / g, compacted density ρ≥3.35g / cm³ 3 .

[0011] In some embodiments, the average equivalent diameter d1 of the primary particles satisfies: 400nm ≤ d1 ≤ 800nm.

[0012] In some embodiments, the D of the secondary particles v 50 satisfies: 3.5μm≤D v 50≤7.2μm.

[0013] In some embodiments, the porosity φ satisfies: 4.5% ≤ φ ≤ 8%.

[0014] In some embodiments, the specific surface area S satisfies: 0.8 m² 2 / g≤S≤1.2m 2 / g.

[0015] In some embodiments, the compaction density ρ satisfies: 3.38 g / cm³ 3 ≤ρ≤3.5g / cm 3 .

[0016] In some embodiments, the battery prepared from the nickel-cobalt-manganese cathode material has an initial discharge specific capacity >190mAh / g under 0.1C and 1.9~3.7V conditions.

[0017] In some embodiments, the capacity retention rate of the battery prepared from the lithium nickel cobalt manganese oxide cathode material is > 97% under the conditions of 0.33C, 1.9 - 3.7V, and 100 cycles.

[0018] A preparation method of a lithium nickel cobalt manganese oxide cathode material includes the following steps: Mix a coprecipitation precursor material of nickel, cobalt, and manganese with a lithium source to obtain a mixed material.

[0019] Perform first spark plasma sintering on the mixed material. The axial pressure of the first spark plasma sintering is P1, and the temperature of the first spark plasma sintering is T1 to obtain a first material; perform second spark plasma sintering on the first material. The axial pressure of the second spark plasma sintering is P2, and the temperature of the second spark plasma sintering is T2 to obtain a second material; wherein, P1 < P2 and T1 < T2. Perform classification treatment on the second material.

[0020] In some embodiments, the axial pressure P1 of the first spark plasma sintering satisfies: 5MPa ≤ P1 ≤ 10MPa.

[0021] In some embodiments, the temperature T1 of the first spark plasma sintering satisfies: 400°C ≤ T1 ≤ 600°C.

[0022] In some embodiments, the axial pressure P2 of the second spark plasma sintering satisfies: 五十MPa ≤ P2 ≤ 100MPa.

[0023] In some embodiments, the temperature T2 of the second spark plasma sintering satisfies: 700°C ≤ T2 ≤ 800°C.

[0024] In some embodiments, the holding time of the first spark plasma sintering is t1, and the holding time of the second spark plasma sintering is t2, 2min ≤ t2 - t1 ≤ 8min.

[0025] In some embodiments, the holding time t1 of the first spark plasma sintering satisfies: 2min ≤ t1 ≤ 3min.

[0026] In some embodiments, the holding time t2 of the second spark plasma sintering satisfies: 5min ≤ t2 ≤ 10min.

[0027] In some embodiments, the heating rate of the first spark plasma sintering is ν1, and the heating rate of the second spark plasma sintering is ν2, 15°C / min ≤ ν1 - ν2 ≤ 35°C / min.

[0028] It should be noted that in the translation of "五十MPa", it is guessed that the original text might be "50MPa", and the translation is adjusted accordingly. If there is an error, please correct it according to the actual situation.In some embodiments, the heating rate ν1 of the first discharge plasma sintering satisfies: 30℃ / min ≤ ν1 ≤ 55℃ / min.

[0029] In some embodiments, the heating rate ν2 of the second discharge plasma sintering satisfies: 15℃ / min ≤ ν2 ≤ 25℃ / min.

[0030] In some embodiments, the pulse currents of the first discharge plasma sintering and the second discharge plasma sintering are each independently 500~1000A.

[0031] In some embodiments, the atmospheres for the first and second discharge plasma sintering are each independently a vacuum atmosphere.

[0032] In some embodiments, the preparation method of the nickel-cobalt-manganese coprecipitation precursor material specifically includes: coprecipitating nickel salt, cobalt salt, manganese salt, complexing agent and precipitant under protective gas conditions, collecting the precipitate and drying it.

[0033] In some embodiments, the nickel salt in the preparation method of the nickel-cobalt-manganese coprecipitation precursor material includes at least one of nickel sulfate, nitrate, chloride and acetate.

[0034] In some embodiments, the cobalt salt includes at least one of cobalt sulfate, nitrate, chloride, and acetate.

[0035] In some embodiments, the manganese salt includes at least one of manganese sulfate, nitrate, chloride, and acetate.

[0036] In some embodiments, the complexing agent in the preparation method of the nickel-cobalt-manganese coprecipitation precursor material includes at least one of ammonia, ammonium bicarbonate, ammonium carbonate, and ammonium sulfate.

[0037] In some embodiments, the precipitant in the preparation method of the nickel-cobalt-manganese coprecipitation precursor material includes at least one of sodium hydroxide, sodium carbonate, sodium bicarbonate, and potassium hydroxide.

[0038] In some embodiments, the pH of the coprecipitation reaction system is 11-12.5 in the preparation method of the nickel-cobalt-manganese coprecipitation precursor material.

[0039] In some embodiments, the lithium source includes at least one of lithium hydroxide and lithium carbonate.

[0040] In some embodiments, the grading process includes a first pulverization and a second pulverization; the first pulverization includes: micro-pulverization using a roller mill, with a gap spacing of 0.1~0.5mm and an air inlet pressure of 0.2~5MPa; the second pulverization includes airflow pulverization, wherein the airflow pulverization frequency is 10~50Hz and the grading frequency is 20~200Hz.

[0041] A solid-state battery comprising the aforementioned lithium nickel cobalt manganese oxide cathode material, or the lithium nickel cobalt manganese oxide cathode material obtained by the method of producing the aforementioned lithium nickel cobalt manganese oxide cathode material.

[0042] An electrical device comprising the aforementioned solid-state battery.

[0043] Compared with the prior art, the beneficial effects of the present invention are as follows: (1) The average equivalent diameter of the primary particles and the D of the secondary particles of the lithium nickel cobalt manganese oxide cathode material of the present invention v 50 is suitable, possessing low porosity, high specific surface area, and high compaction density; among which, the suitable average equivalent diameter of the primary particles provides sufficient mechanical strength and facilitates growth and fusion during sintering; suitable D v The 50% secondary particle size is beneficial for electrode coating process and maintaining high tap density; low porosity can fundamentally solve the problem of ion transport path interruption caused by pores in solid-state batteries, significantly improving interfacial ion conduction efficiency; the secondary spherical structure constructed from submicron primary particles achieves low porosity while maintaining a high specific surface area, which can greatly increase the contact area with solid electrolyte, facilitate rapid lithium ion migration, and effectively reduce interfacial impedance; high tap density can significantly improve the volumetric energy density of solid-state batteries.

[0044] (2) The preparation method of lithium nickel cobalt manganese oxide cathode material of the present invention, through the combined treatment of first discharge plasma sintering and second discharge plasma sintering, adopts a "stepwise pressurization and heating" strategy, which perfectly combines the mechanical densification effect of axial pressure with the thermal densification effect of pulse current, and simultaneously solves the problems of crystallization, lithiation and densification. The process is simple and efficient. Among them, the function of the first discharge plasma sintering includes: removing crystal water, promoting the initial contact between particles and the formation of crystal nuclei, while avoiding the particles growing too fast; the function of the second discharge plasma sintering includes: high axial pressure forcing the particles to undergo plastic deformation and creep, effectively eliminating the effects of crystallization and creep. In addition to eliminating the pores between particles, the Joule heating effect generated by the pulsed current can instantly produce local high temperatures between particles, promoting atomic diffusion and fusion on the particle surface, realizing the directional growth of grains and the closure of pores, and finally forming dense aggregates. By controlling the size and distribution of secondary particles through precursor synthesis and airflow classification, the resulting material has good sphericity and flowability, strong compatibility with existing electrode sheet manufacturing processes, and broad application prospects. Through the coordinated cooperation of each step, a lithium nickel cobalt manganese oxide cathode material with primary particles of suitable average equivalent diameter, secondary particles of suitable Dv50, porosity, specific surface area, and compaction density is obtained.

[0045] (3) The solid-state battery of the present invention has high discharge specific capacity and capacity retention rate, good cycle performance and rate performance, and high safety performance. Attached Figure Description

[0046] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0047] Figure 1 This is a scanning electron microscope image of the lithium nickel cobalt manganese oxide cathode material of Example 1 of the present invention; Figure 2 This is a scanning electron microscope image of the cathode material of Comparative Example 1 of the present invention; Figure 3 The diagram shows the cycle performance of the cathode materials in Example 1 and Comparative Example 1 of this invention. Detailed Implementation

[0048] The embodiments of the present invention will be described in detail below with reference to examples. However, those skilled in the art will understand that the following examples are for illustrative purposes only and should not be considered as limiting the scope of the invention. Unless otherwise specified in the examples, conventional conditions or conditions recommended by the manufacturer are followed. Reagents or instruments whose manufacturers are not specified are all commercially available conventional products.

[0049] According to one aspect of the present invention, the present invention relates to a lithium nickel cobalt manganese oxide cathode material, wherein the general chemical formula of the lithium nickel cobalt manganese oxide cathode material is Li. a Ni x Co y Mn z O2, where 0.9≤a≤1.2, 0<x≤1, x+y+z=1; the lithium nickel cobalt manganese oxide cathode material includes secondary particles, which are formed by the agglomeration of primary particles. The average equivalent diameter d1 of the primary particles satisfies: 400nm≤d1≤1μm (e.g., 400nm, 500nm, 700nm, 800nm, 1μm, etc.). The D of the secondary particles... v 50 satisfies: 3μm≤D v The micrometer diameter (φ) is ≤8.5μm (e.g., 3μm, 4μm, 5μm, 6μm, 7μm, 8.5μm, etc.); the porosity of the lithium nickel cobalt manganese oxide cathode material is ≤10% (e.g., 3%, 5%, 6%, 7%, 8%, 9% or 10%, etc.), and the specific surface area S is ≥0.7m². 2 / g (e.g., 0.7m) 2 / g, 0.8m 2 / g, 0.85m 2 / g, 0.9m 2 / g, 1m 2 / g, 1.1m 2 / g, 1.2m 2 / g, etc.), compacted density ρ≥3.35g / cm³ 3 (e.g., 3.35g / cm) 3 3.4g / cm 3 3.5g / cm 3 3.55g / cm 3 3.6g / cm 3 wait).

[0050] The average equivalent diameter of the primary particles and the D of the secondary particles in the lithium nickel cobalt manganese oxide cathode material of the present invention v 50 is suitable, possessing low porosity, high specific surface area, and high compaction density; among which, the suitable average equivalent diameter of the primary particles provides sufficient mechanical strength and facilitates growth and fusion during sintering; suitable D vThe 50% secondary particle size is beneficial for electrode coating process and maintaining high tap density; low porosity can fundamentally solve the problem of ion transport path interruption caused by pores in solid-state batteries, significantly improving interfacial ion conduction efficiency; the secondary spherical structure constructed from submicron primary particles achieves low porosity while maintaining a high specific surface area, which can greatly increase the contact area with solid electrolyte, facilitate rapid lithium ion migration, and effectively reduce interfacial impedance; high tap density can significantly improve the volumetric energy density of solid-state batteries.

[0051] In some embodiments, the average equivalent diameter d1 of the primary particles satisfies: 400nm ≤ d1 ≤ 800nm. In some embodiments, the D of the secondary particles... v 50 satisfies: 3.5μm≤D v 50 ≤ 7.2 μm. In some embodiments, the porosity φ satisfies: 4.5% ≤ φ ≤ 8%. In some embodiments, the specific surface area S satisfies: 0.8 m² / s². 2 / g≤S≤1.2m 2 / g. In some embodiments, the compaction density ρ satisfies: 3.38 g / cm³. 3 ≤ρ≤3.5g / cm 3 The present invention further optimizes the average equivalent diameter of the primary particles and the D of the secondary particles. v 50. Porosity φ, specific surface area S, and compaction density ρ, which in turn ensure the comprehensive performance of lithium nickel cobalt manganese oxide cathode materials.

[0052] In some embodiments, the battery prepared from the lithium nickel cobalt manganese oxide cathode material exhibits an initial discharge specific capacity >190 mAh / g under 0.1C and 1.9~3.7V conditions, such as 195 mAh / g, 198 mAh / g, 200 mAh / g, 205 mAh / g, etc. In some embodiments, the battery prepared from the lithium nickel cobalt manganese oxide cathode material exhibits a capacity retention rate >97% under 0.33C, 1.9~3.7V, and 100 cycles conditions, such as 97.5%, 98%, 98.5%, etc. The battery prepared from the lithium nickel cobalt manganese oxide cathode material of the present invention possesses excellent initial discharge specific capacity and capacity retention rate.

[0053] According to another aspect of the present invention, the present invention also relates to a method for preparing a lithium nickel cobalt manganese oxide cathode material, comprising the following steps: Mix the coprecipitated precursor material of nickel, cobalt and manganese with a lithium source to make the lithium source uniformly adhere to the surface of the precursor particles, obtaining a mixed material. Perform first spark plasma sintering on the mixed material, where the axial pressure of the first spark plasma sintering is P1 and the temperature of the first spark plasma sintering is T1, obtaining a first material. Perform second spark plasma sintering on the first material, where the axial pressure of the second spark plasma sintering is P2 and the temperature of the second spark plasma sintering is T2, obtaining a second material; wherein, P1 < P2 and T1 < T2. Perform classification treatment on the second material.

[0054] The preparation method of the lithium nickel cobalt manganese oxide cathode material of the present invention adopts a spark plasma sintering (SPS) process. Through the combined treatment of the first spark plasma sintering and the second spark plasma sintering, adopting a "stepwise pressurization and heating" strategy, the mechanical densification effect of the axial pressure is perfectly combined with the thermal densification effect of the pulsed current, synchronously solving the problems of crystallization, lithiation and densification, and the process is simple and efficient; among them, the functions of the first spark plasma sintering include: removing crystal water, promoting the initial contact between particles and the formation of crystal nuclei, while avoiding the overgrowth of particles; the functions of the second spark plasma sintering include: the high axial pressure forces the particles to undergo plastic deformation and creep, effectively eliminating the pores between particles; the Joule heat effect generated by the pulsed current can instantaneously generate local high temperature between particles, promoting the atomic diffusion and fusion on the particle surface, realizing the directional growth of grains and the closure of pores, and finally forming a dense aggregate. By controlling the size and distribution of secondary particles through precursor synthesis and air classification, the obtained material has good sphericity and fluidity, strong compatibility with the existing electrode sheet manufacturing process, and broad application prospects. Through the coordinated cooperation of each step, a lithium nickel cobalt manganese oxide cathode material with suitable average equivalent diameter of primary particles, suitable Dv50 of secondary particles, porosity, specific surface area and tap density is obtained.

[0055] In some embodiments, the pulsed currents of the first spark plasma sintering and the second spark plasma sintering are each independently 500 - 1000 A, such as 500 A, 600 A, 700 A, 800 A, 900 A, 1000 A, etc. The appropriate pulsed currents of the first spark plasma sintering and the second spark plasma sintering can ensure the sintering effect.

[0056] In some embodiments, 40 MPa ≤ P2 - P1 ≤ 95 MPa, such as 40 MPa, 50 MPa, 60 MPa, 70 MPa, 80 MPa or 95 MPa, etc. The present invention has an appropriate pressure difference between the axial pressures of the first spark plasma sintering and the second spark plasma sintering to ensure the combined effect of the two-stage sintering process.

[0057] In some embodiments, 100℃≤T2-T1≤400℃, such as 100℃, 150℃, 200℃, 250℃, 300℃, 400℃, etc. The sintering temperatures of the first discharge plasma sintering and the second discharge plasma sintering of the invention have a suitable difference to ensure the combined sintering effect of the two stages.

[0058] In some embodiments, the holding time for the first discharge plasma sintering is t1, and the holding time for the second discharge plasma sintering is t2, where 2 min ≤ t2 - t1 ≤ 8 min (e.g., 2 min, 3 min, 4 min, 5 min, 8 min, etc.). The holding times for the first and second discharge plasma sintering have a suitable difference, and the two can work together to improve the effect of discharge plasma sintering.

[0059] In some embodiments, the heating rate of the first discharge plasma sintering is ν1, and the heating rate of the second discharge plasma sintering is ν2, where 15℃ / min≤ν1-ν2≤35℃ / min (e.g., 15℃ / min, 20℃ / min, 25℃ / min, 30℃ / min, 35℃ / min, etc.).

[0060] In some embodiments, the axial pressure P1 of the first discharge plasma sintering satisfies: 5MPa ≤ P1 ≤ 10MPa, where P1 is, for example, 5MPa, 5.5MPa, 6MPa, 6.5MPa, 7MPa, 7.5MPa, 8MPa, 9MPa, 10MPa, or any value within a range of two. In some embodiments, the temperature T1 of the first discharge plasma sintering satisfies: 400℃ ≤ T1 ≤ 600℃, where T1 is, for example, 400℃, 450℃, 500℃, 520℃, 550℃, 580℃, 600℃, or any value within a range of two. In some embodiments, the holding time t1 of the first discharge plasma sintering satisfies: 2min ≤ t1 ≤ 3min, for example, 2min, 2.5min, or 3min. In some embodiments, the heating rate ν1 of the first discharge plasma sintering satisfies: 30℃ / min ≤ ν1 ≤ 55℃ / min, for example, 30℃ / min, 35℃ / min, 40℃ / min, 50℃ / min, 55℃ / min, etc. The atmosphere for the first discharge plasma sintering is a vacuum atmosphere. The first discharge plasma sintering of the present invention uses lower axial pressure, sintering temperature, holding time, and heating rate ν1, which facilitates the initial contact between particles and the formation of crystal nuclei, and can avoid excessively rapid particle growth, thereby ensuring the effectiveness of the initial heat treatment.

[0061] In some embodiments, the axial pressure P2 of the second discharge plasma sintering satisfies: 50MPa ≤ P2 ≤ 100MPa, where P2 is, for example, 50MPa, 60MPa, 70MPa, 80MPa, 90MPa, or 100MPa. In some embodiments, the temperature T2 of the second discharge plasma sintering satisfies: 700℃ ≤ T2 ≤ 800℃, where T2 is, for example, 700℃, 710℃, 720℃, 730℃, 750℃, 780℃, or 800℃. In some embodiments, the holding time t2 of the second discharge plasma sintering satisfies: 5min ≤ t2 ≤ 10min, where t2 is, for example, 5min, 6min, 7min, 8min, 9min, or 10min. In some embodiments, the heating rate ν2 of the second discharge plasma sintering satisfies: 15℃ / min ≤ ν2 ≤ 25℃ / min, where ν2 is, for example, 15℃ / min, 18℃ / min, 20℃ / min, or 25℃ / min. The atmosphere for the second discharge plasma sintering is a vacuum atmosphere. The second discharge plasma sintering of this invention employs relatively high axial pressure, sintering temperature, holding time, and heating rate, which is beneficial for achieving directional grain growth and pore closure, and for forming dense aggregates.

[0062] In some embodiments, the preparation method of the nickel-cobalt-manganese coprecipitation precursor material specifically includes: coprecipitating nickel salt, cobalt salt, manganese salt, complexing agent, and precipitant under a protective gas condition, collecting the precipitate, and drying it. Collecting the precipitate includes centrifugation and washing. The protective gas includes nitrogen, argon, etc.

[0063] In some embodiments, the nickel salt includes at least one selected from nickel sulfate, nitrate, chloride, and acetate. In some embodiments, the cobalt salt includes at least one selected from cobalt sulfate, nitrate, chloride, and acetate. In some embodiments, the manganese salt includes at least one selected from manganese sulfate, nitrate, chloride, and acetate.

[0064] In some embodiments, the complexing agent includes at least one selected from ammonia, ammonium bicarbonate, ammonium carbonate, and ammonium sulfate. In some embodiments, the concentration of the complexing agent is 1~10 mol / L, for example, 1 mol / L, 2 mol / L, 5 mol / L, 10 mol / L, etc. The ammonia concentration in the mixture of nickel salt, cobalt salt, manganese salt, complexing agent, and precipitant is 0.1~2.0 mol / L, for example, 0.1 mol / L, 0.5 mol / L, 1 mol / L, or 2 mol / L, etc.

[0065] In some embodiments, the precipitant includes at least one selected from sodium hydroxide, sodium carbonate, sodium bicarbonate, and potassium hydroxide. In some embodiments, the concentration of the precipitant is 5-12 mol / L, for example, 5 mol / L, 8 mol / L, 10 mol / L, 12 mol / L, etc.

[0066] In some embodiments, the pH of the coprecipitation reaction system in the preparation method of the nickel-cobalt-manganese precursor material is 11~12.5, such as 11, 11.5, 12 or 12.5.

[0067] The preparation process conditions of the above-mentioned suitable nickel-cobalt-manganese coprecipitation precursor materials are coordinated to ensure the performance of the nickel-cobalt-manganese coprecipitation precursor materials and facilitate subsequent spark plasma sintering treatment.

[0068] In some embodiments, the lithium source includes at least one of lithium hydroxide and lithium carbonate.

[0069] In some embodiments, the grading process includes a first pulverization and a second pulverization. The first pulverization includes: micro-pulverization using a roller mill with a gap spacing of 0.1~0.5mm, such as 0.1mm, 0.2mm, 0.3mm, 0.4mm, 0.5mm, etc. The inlet air pressure is 0.2~5MPa, such as 0.2MPa, 0.5MPa, 1MPa, 2MPa, 3MPa, or 5MPa, etc. The second pulverization includes air jet milling, with a frequency of 10~50Hz, such as 10Hz, 15Hz, 20Hz, 30Hz, 50Hz, etc., and a grading frequency of 20~200Hz, such as 20Hz, 50Hz, 100Hz, 200Hz, etc. This invention, after slightly pulverizing the block material, uses an air jet mill for further pulverization and grading to remove a small amount of excessively large or small particles that may have been generated during sintering, resulting in a more concentrated secondary particle size distribution in the final product, meeting the requirements for battery cell applications.

[0070] According to another aspect of the present invention, the present invention also relates to a solid-state battery comprising the aforementioned lithium nickel cobalt manganese oxide cathode material, or the lithium nickel cobalt manganese oxide cathode material obtained by the method of making the aforementioned lithium nickel cobalt manganese oxide cathode material.

[0071] The solid-state battery of the present invention has high discharge specific capacity and capacity retention, good cycle performance and rate performance, and high safety performance.

[0072] According to another aspect of the invention, the invention also relates to an electrical device including the aforementioned solid-state battery. The electrical device includes electric vehicles, power tools, laptops, etc.

[0073] The following explanation, combined with specific embodiments and comparative examples, further illustrates the point.

[0074] Example 1 A method for preparing lithium nickel cobalt manganese oxide cathode material includes the following steps: (1) Synthesis of precursor materials: A mixed solution of nickel sulfate, cobalt sulfate and manganese sulfate with a total metal ion concentration of 2.0 mol / L was prepared according to the molar ratio of Ni:Co:Mn=80:10:10. This solution was added in parallel with 4 mol / L NaOH solution to a reactor containing a bottom liquid (containing 0.8 mol / L ammonia water). The reaction pH was controlled at 11.5, the temperature at 55℃, the stirring speed at 1000 rpm, and the reaction was carried out for 48 h. After centrifugation, washing and drying, the hydroxide precursor material was obtained.

[0075] (2) Spark plasma sintering treatment: The above precursor material is mixed with lithium hydroxide at a stoichiometric ratio of 1.05, placed in a mold, and then placed in an SPS sintering furnace. First, the furnace is evacuated to a vacuum environment and the pulse current is set to 600A. First stage: apply an axial pressure of 8MPa, heat up to 500℃ at 50℃ / min, and hold for 2min; Second stage: increase the axial pressure to 60MPa, heat up to 750℃ at 20℃ / min, and hold for 8min.

[0076] (3) Grading process: The block obtained by SPS sintering is lightly crushed by a roller mill and then graded by airflow milling to obtain the final cathode material. The roller gap is 0.2 mm, the air inlet pressure is 1 MPa, the airflow milling frequency is 15 Hz, and the grading frequency is 80 Hz.

[0077] The scanning electron microscope image of the lithium nickel cobalt manganese oxide cathode material in this embodiment is as follows: Figure 1 As shown.

[0078] Example 2 A method for preparing lithium nickel cobalt manganese oxide cathode material differs from that in Example 1 in that: In step (2), the pulse current of the first stage is 700A and the sintering temperature is 550℃.

[0079] Example 3 A method for preparing lithium nickel cobalt manganese oxide cathode material differs from that in Example 1 in that: In step (2), the axial pressure of the second stage is 80 MPa, the sintering temperature is 780℃, and the holding time is 10 min.

[0080] Example 4 A method for preparing a lithium nickel cobalt manganese oxide cathode material differs from Example 1 in that: In step (2), the pulse current of the first stage is 900A, the sintering temperature is 450℃, and the axial pressure is 10Mpa.

[0081] Example 5 A method for preparing lithium nickel cobalt manganese oxide cathode material differs from that in Example 1 in that: In step (2), the axial pressure of the second stage is 90 MPa, the sintering temperature is 700℃, and the holding time is 6 min.

[0082] Example 6 A method for preparing lithium nickel cobalt manganese oxide cathode material differs from that in Example 1 in that: In step (1), the element ratio is adjusted to Ni:Co:Mn=83:12:5.

[0083] Example 7 A method for preparing lithium nickel cobalt manganese oxide cathode material differs from that in Example 1 in that: In step (1), the element ratio is adjusted to Ni:Co:Mn=75:15:10.

[0084] Example 8 A method for preparing lithium nickel cobalt manganese oxide cathode material differs from that in Example 1 in that: In step (1), the element ratio is adjusted to Ni:Co:Mn=60:30:10.

[0085] Example 9 A method for preparing lithium nickel cobalt manganese oxide cathode material differs from that in Example 1 in that: In step (1), the reaction pH is controlled at 12.2.

[0086] Example 10 A method for preparing lithium nickel cobalt manganese oxide cathode material differs from that in Example 1 in that: In step (3), the gap between the rollers is 0.4 mm, the air inlet pressure is 2.2 MPa, the airflow pulverization frequency is 20 Hz, and the grading frequency is 100 Hz.

[0087] Comparative Example 1 A method for preparing a cathode material differs from that in Example 1 in that: Spark plasma sintering: The precursor material was mixed with lithium hydroxide at a stoichiometric ratio of 1.05, placed in a mold, and then placed in an SPS sintering furnace. The furnace was first evacuated to a vacuum environment, and a pulse current of 600A was set, with an axial pressure of 60MPa applied. The temperature was increased to 750℃ at a rate of 20℃ / min. The temperature was held for 10 minutes.

[0088] The scanning electron microscope (SEM) image of the lithium nickel cobalt manganese oxide cathode material in this comparative example is shown below. Figure 2 As shown.

[0089] Comparative Example 2 A method for preparing a cathode material differs from that in Example 1 in that: The SPS sintering in step (2) was changed to high-temperature solid-state sintering, that is, the precursor material was mixed with lithium hydroxide at a stoichiometric ratio of 1.05 and placed in a high-temperature sintering furnace under an oxygen atmosphere and held at 720°C for 15 hours.

[0090] Experimental Example I. Physical property testing of lithium nickel cobalt manganese oxide cathode material The lithium nickel cobalt manganese oxide cathode materials of each embodiment and comparative example were subjected to physical performance tests, including: the average equivalent diameter of primary particles, the Dv50 of secondary particles, porosity, specific surface area and compaction density.

[0091] (1) Test method for the average equivalent diameter of primary particles: Observe the material under test with an electron microscope, measure the diameter of no less than 100 primary particles using image analysis software, and calculate the average equivalent diameter of primary particles.

[0092] (2) Test method for Dv50 of secondary particles: Disperse each particle material in deionized water, sonicate for 10 min, and test with a laser particle size analyzer to obtain the Dv50 of secondary particles.

[0093] (3) Test method for porosity: The cross-sectional structure of the material under test is observed by electron microscope, and the pore area and the area of ​​the entire observation area are measured and calculated by image analysis software to obtain the porosity of the material.

[0094] (4) Specific surface area test method: Micromeritics Tristar II was used to test the adsorption of N2 and calculate the adsorption amount under different equilibrium pressures. The isothermal adsorption line was obtained and the specific surface area of ​​the cathode material was calculated.

[0095] (5) Test method for compaction density: Weigh 2g of sample and add it into a mold with a diameter of 13mm and a cylinder height of 25mm. Hold it at 200MPa for 10s for compaction test. Calculate the compaction density based on the sample thickness before and after compaction.

[0096] The physical performance test results of lithium nickel cobalt manganese oxide cathode material are shown in Table 1.

[0097] Table 1 Physical performance test results

[0098] As shown in Table 1, the lithium nickel cobalt manganese oxide cathode materials obtained by the methods in the various embodiments of the present invention have suitable average equivalent diameter of primary particles, Dv50 of secondary particles, porosity, specific surface area, and compaction density. The average equivalent diameter of primary particles is 400 nm to 800 nm, and the Dv50 of secondary particles is... v50 has a diameter of 3.5μm to 8μm, a porosity φ ≤ 10%, and a specific surface area S ≥ 0.7m². 2 / g, compacted density ρ≥3.35g / cm³ 3 .

[0099] The discharge plasma sintering of Comparative Example 1 only involves one stage of processing, resulting in secondary particles of lithium nickel cobalt manganese oxide cathode material with excessively large Dv50, excessively large porosity, excessively small specific surface area, and low compaction density.

[0100] Comparative Example 2 uses conventional high-temperature solid-state sintering, and the secondary particles of the obtained lithium nickel cobalt manganese oxide cathode material have excessively large Dv50, excessively large porosity, excessively small specific surface area, and low compaction density.

[0101] II. Battery Performance Testing Batteries were prepared using lithium nickel cobalt manganese oxide cathode materials from each embodiment and comparative example.

[0102] For mold battery testing, the positive electrode materials prepared in the examples and comparative examples were mixed with sulfide solid electrolyte and conductive agent acetylene black in a ratio of 70:25:5 and ground in a mortar for 15 minutes to obtain the composite positive electrode material. Then, 50 mg of sulfide solid electrolyte, 10 mg of composite positive electrode material, and lithium-indium alloy were successively added to a mold and assembled under pressure to form a solid-state battery.

[0103] Charge and discharge test: The battery charge and discharge test was conducted using the Blue Electric system. The cutoff voltage was set to 1.9~3.7V. First, it was charged and discharged at 0.1C for 2 cycles, and then charged and discharged at 0.33C for 100 cycles.

[0104] The battery capacity and cycle performance data are shown in Table 2. The cycle performance graphs of the cathode materials in Example 1 and Comparative Example 1 are shown below. Figure 3 As shown.

[0105] Table 2 Battery performance test results

[0106] As shown in Table 2, the batteries prepared from lithium nickel cobalt manganese oxide cathode materials obtained by the methods of the various embodiments of the present invention have excellent initial discharge specific capacity and cycle capacity retention. The initial discharge specific capacity of the batteries under 0.1C and 1.9~3.7V conditions is >190mAh / g, and the capacity retention under 0.33C, 1.9~3.7V and 100 cycles conditions is >97%.

[0107] The batteries prepared from the cathode materials obtained by the methods in Comparative Examples 1 and 2 showed significantly reduced first-discharge specific capacity and cycle capacity retention.

[0108] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A lithium nickel cobalt manganese oxide cathode material, characterized in that, The general chemical formula of the lithium nickel cobalt manganese oxide cathode material is Li a Ni x Co y Mn z O2, where 0.9≤a≤1.2, 0<x≤1, x+y+z=1; The lithium nickel cobalt manganese oxide cathode material includes secondary particles, which are formed by the agglomeration of primary particles. The average equivalent diameter d1 of the primary particles satisfies: 400nm ≤ d1 ≤ 1μm. The secondary particles have a D1 value of 400nm ≤ d1 ≤ 1μm. v 50 satisfies: 3μm≤D v 50≤8.5μm; The lithium nickel cobalt manganese oxide cathode material has a porosity φ ≤ 10% and a specific surface area S ≥ 0.7 m². 2 / g, compacted density ρ≥3.35g / cm³ 3 .

2. The lithium nickel cobalt manganese oxide cathode material according to claim 1, characterized in that, It includes at least one of the following features (1) to (5): (1) The average equivalent diameter d1 of the primary particles satisfies: 400nm≤d1≤800nm; (2) The D of the secondary particles v 50 satisfies: 3.5μm≤D v 50≤7.2μm; (3) The porosity φ satisfies: 4.5% ≤ φ ≤ 8%; (4) The specific surface area S satisfies: 0.8m 2 / g≤S≤1.2m 2 / g; (5) The compaction density ρ satisfies: 3.38 g / cm³ 3 ≤ρ≤3.5g / cm 3 .

3. The lithium nickel cobalt manganese oxide cathode material according to claim 1, characterized in that, It includes at least one of the following features (1) to (2): (1) The battery prepared by the nickel cobalt manganese oxide cathode material has a first discharge specific capacity of >190mAh / g under the conditions of 0.1C and 1.9~3.7V; (2) The battery prepared by the nickel cobalt manganese oxide cathode material has a capacity retention rate of >97% under the conditions of 0.33C, 1.9~3.7V and 100 cycles.

4. The method for preparing the lithium nickel cobalt manganese oxide cathode material according to any one of claims 1 to 3, characterized in that, Includes the following steps: The nickel-cobalt-manganese co-precipitation precursor material was mixed with a lithium source to obtain a mixture. The mixture is subjected to a first discharge plasma sintering, wherein the axial pressure of the first discharge plasma sintering is P1 and the temperature of the first discharge plasma sintering is T1, to obtain a first material. The first material is subjected to a second discharge plasma sintering, wherein the axial pressure of the second discharge plasma sintering is P2 and the temperature of the second discharge plasma sintering is T2, thereby obtaining a second material; Among them, P1 <P2,T1<T2; The second material is then subjected to a grading process.

5. The method for preparing lithium nickel cobalt manganese oxide cathode material according to claim 4, characterized in that, It includes at least one of the following features (1) to (4): (1) The axial pressure P1 of the first discharge plasma sintering satisfies: 5MPa≤P1≤10MPa; (2) The temperature T1 of the first discharge plasma sintering satisfies: 400℃≤T1≤600℃; (3) The axial pressure P2 of the second discharge plasma sintering satisfies: 50MPa≤P2≤100MPa; (4) The temperature T2 of the second discharge plasma sintering satisfies: 700℃≤T2≤800℃.

6. The method for preparing lithium nickel cobalt manganese oxide cathode material according to claim 4, characterized in that, It includes at least one of the following features (1) to (8): (1) The holding time of the first discharge plasma sintering is t1, and the holding time of the second discharge plasma sintering is t2, 2min≤t2-t1≤8min; (2) The first discharge plasma sintering holding time t1 satisfies: 2min≤t1≤3min; (3) The second discharge plasma sintering holding time t2 satisfies: 5min≤t2≤10min; (4) The heating rate of the first discharge plasma sintering is ν1, and the heating rate of the second discharge plasma sintering is ν2, 15℃ / min≤ν1-ν2≤35℃ / min; (5) The heating rate ν1 of the first discharge plasma sintering satisfies: 30℃ / min≤ν1≤55℃ / min; (6) The heating rate ν2 of the second discharge plasma sintering satisfies: 15℃ / min≤ν2≤25℃ / min; (7) The pulse currents of the first discharge plasma sintering and the second discharge plasma sintering are each 500~1000A independently; (8) The atmosphere of the first discharge plasma sintering and the second discharge plasma sintering are each a vacuum atmosphere.

7. The method for preparing lithium nickel cobalt manganese oxide cathode material according to claim 4, characterized in that, It includes at least one of the following features (1) to (6): (1) The preparation method of the nickel-cobalt-manganese coprecipitation precursor material specifically includes: coprecipitating nickel salt, cobalt salt, manganese salt, complexing agent and precipitant under protective gas conditions, collecting the precipitate and drying it; (2) In the preparation method of the nickel-cobalt-manganese coprecipitation precursor material, the nickel salt includes at least one of nickel sulfate, nitrate, chloride and acetate; The cobalt salt includes at least one of cobalt sulfate, nitrate, chloride and acetate. The manganese salt includes at least one of manganese sulfate, nitrate, chloride and acetate. (3) In the preparation method of the nickel-cobalt-manganese coprecipitation precursor material, the complexing agent includes at least one of ammonia, ammonium bicarbonate, ammonium carbonate and ammonium sulfate; (4) In the preparation method of the nickel-cobalt-manganese coprecipitation precursor material, the precipitant includes at least one of sodium hydroxide, sodium carbonate, sodium bicarbonate and potassium hydroxide; (5) In the preparation method of the nickel-cobalt-manganese coprecipitation precursor material, the pH of the coprecipitation reaction system is 11~12.5; (6) The lithium source includes at least one of lithium hydroxide and lithium carbonate.

8. The method for preparing lithium nickel cobalt manganese oxide cathode material according to claim 4, characterized in that, The graded processing includes a first crushing and a second crushing; The first pulverization includes: micro-pulverization using a roller mill, with a gap spacing of 0.1~0.5mm and an air inlet pressure of 0.2~5MPa; The second pulverization includes airflow pulverization, wherein the airflow pulverization frequency is 10~50Hz and the grading frequency is 20~200Hz.

9. A solid-state battery, characterized in that, The lithium nickel cobalt manganese oxide cathode material includes the lithium nickel cobalt manganese oxide cathode material according to any one of claims 1 to 3, or the lithium nickel cobalt manganese oxide cathode material obtained by any one of claims 4 to 8.

10. An electrical appliance, characterized in that, Includes the solid-state battery as described in claim 9.

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