A single-crystal cathode material, its preparation method and application

Abstract

This invention relates to the field of new energy materials, specifically to a single-crystal cathode material, its preparation method, and its application. The single-crystal cathode material has the chemical formula LiNi. x Co y Me 1‑x‑ y O2; wherein 0≤x, 0≤y, 0<x+y≤1, and Me includes at least one of the following metallic elements: Al, Ti, Mg, Sr, W, Ca, Nb, Cr, Mn, and Fe. The aforementioned single-crystal cathode material has accurate lithium content, a well-preserved layered structure, stable structure, excellent electrochemical performance, uniform internal elemental composition distribution, high charge-discharge specific capacity, and stable cycle performance.

Description

Technical Field

[0001] This invention relates to the field of new energy materials, and more specifically, to a single-crystal cathode material, its preparation method, and its application. Background Technology

[0002] Lithium-ion batteries, with their advantages of high energy density, high power density, and long lifespan, are playing an increasingly important role in portable devices, automobiles, and energy storage. Traditional cathode materials, with their spherical or other morphological structures composed of primary particles, have numerous grain boundaries. During charging or discharging, lattice contraction or expansion occurs, making it easy for stress inconsistencies to occur between closely spaced primary particles, leading to noticeable cracks. Therefore, due to the inherent multi-level structural characteristics of this type of cathode material, it is prone to problems such as main morphological degradation, primary particle detachment, electrolyte infiltration into intergranular spaces, and impurity phase formation after long-term cycling, resulting in rapid decline in its electrochemical performance.

[0003] To develop high-performance, high-strength cathode materials, researchers have proposed synthesizing micron-sized single-crystal cathode materials. These single-crystal cathode materials are widely used in batteries due to their excellent high-temperature performance, high-voltage performance, long cycle performance, and stable structural morphology. Although existing research and technologies have used CoCO3 and Ni... x Co y Mn 1-x-y Single-crystal cathode materials can be prepared using precursors with specific morphologies, tap densities, and specific surface areas, such as (OH)₂, via the molten salt method. However, the reaction time is generally long, and the reaction is highly dependent on the CoCO₃ and Ni alloys used. x Co y Mn 1-x-y The stringent requirements for precursors such as (OH)2 result in higher production costs for these single-crystal cathode materials compared to spherical cathode materials produced by conventional methods, hindering the further expansion of the market share of single-crystal cathode materials. Furthermore, some researchers have proposed preparing single-crystal ternary electrode materials through solid-phase mixing and molten salt reactions of raw materials with different elemental compositions. However, the single-crystal cathode materials prepared by this method exhibit uneven elemental composition and segregation, which severely affects the battery performance of the cathode material.

[0004] Currently, the strategy of synthesizing single-crystal cathode materials at high cost is still insufficient to meet the urgent need of the new energy market for high-performance single-crystal cathode materials. Therefore, developing a targeted, efficient, simple, and low-cost synthesis method for preparing micron-sized single-crystal large-particle electrode materials is of great significance for promoting the development of commercial single-crystal cathode materials.

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

[0006] One aspect of the present invention relates to a single-crystal cathode material, wherein the chemical formula of the single-crystal cathode material is LiNi. x Co y Me 1-x-y O2;

[0007] Wherein, 0≤x, 0≤y, 0<x+y≤1, and Me includes at least one of Al, Ti, Mg, Sr, W, Ca, Nb, Cr, Mn, or Fe.

[0008] The aforementioned single-crystal cathode material has accurate lithium content, intact layered structure, stable structure, excellent electrochemical performance, uniform internal elemental composition distribution, high charge-discharge specific capacity, and stable cycle performance.

[0009] Another aspect of the present invention relates to a method for preparing the aforementioned single-crystal cathode material, comprising the following steps:

[0010] (a) A co-precipitation reaction was carried out after adding a precipitant to solution A containing soluble salt to obtain nanoparticle precursors;

[0011] (b) The mixture of the nanoparticle precursor and molten salt is sintered, granulated, and washed to obtain single-crystal particles;

[0012] The sintering temperature is 850–1000℃; the sintering time is 1–5 hours.

[0013] (c) The mixture of the single crystal particles and the lithium source is calcined;

[0014] The calcination temperature is 650–950℃; the calcination time is 3–10 h.

[0015] The method for preparing the single-crystal cathode material is efficient, simple, and low-cost, with fast sintering and granulation speed. It can flexibly introduce trace amounts of doping elements when preparing the precursor, and the sintering and calcination processes do not need to be carried out under a protective atmosphere. A single-crystal cathode material with excellent electrochemical performance can be obtained in a very short reaction time.

[0016] Another aspect of the present invention relates to a positive electrode sheet, comprising a single-crystal positive electrode material prepared by the aforementioned method for preparing single-crystal positive electrode material.

[0017] Another aspect of the present invention relates to a lithium-ion battery, including the aforementioned lithium-ion battery.

[0018] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0019] (1) The single-crystal cathode material provided by the present invention has accurate lithium content, intact layered structure, stable structure, excellent electrochemical performance, uniform internal elemental composition distribution, high charge-discharge specific capacity, and stable cycle performance.

[0020] (2) The method for preparing single-crystal cathode material provided by the present invention is efficient, simple and low cost, and has a fast sintering and granulation speed. It can flexibly introduce trace amounts of doping elements when preparing the precursor. The sintering and calcination processes do not need to be carried out under the protection of a protective atmosphere. A single-crystal cathode material with excellent electrochemical performance can be obtained in a very short reaction time. Attached Figure Description

[0021] 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.

[0022] Figure 1 The image shown is an FESEM image of the single-crystal cathode material in Example 1 of this invention.

[0023] Figure 2 This is the FESEM image of the single-crystal cathode material in Example 2 of the present invention;

[0024] Figure 3 The image shows the XRD pattern of the single-crystal cathode material in Example 1 of this invention.

[0025] Figure 4 The image shows the XRD pattern of the single-crystal cathode material in Example 2 of this invention.

[0026] Figure 5 This is a graph showing the long-cycle performance of the single-crystal cathode material at 1C in Example 1 of this invention;

[0027] Figure 6 This is a graph showing the long-cycle performance of the single-crystal cathode material at 1C in Example 2 of the present invention. Detailed Implementation

[0028] The technical solution of the present invention will be clearly and completely described below with reference to the accompanying drawings and specific embodiments. However, those skilled in the art will understand that the embodiments described below are some embodiments of the present invention, but not all embodiments, and are only used to illustrate the present invention, and should not be regarded as limiting the scope of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall be followed. Where the manufacturers of reagents or instruments are not specified, they are all conventional products that can be purchased commercially.

[0029] One aspect of the present invention relates to a single-crystal cathode material, wherein the single-crystal cathode material has the chemical formula LiNi. x Co y Me 1-x-y O2;

[0030] Wherein, 0≤x, 0≤y, 0<x+y≤1, and Me includes, but is not limited to, at least one of the following elements: Al, Ti, Mg, Sr, W, Ca, Nb, Cr, Mn, or Fe.

[0031] The single-crystal cathode material has accurate lithium content, intact layered structure, stable structure, excellent electrochemical performance, uniform internal elemental composition distribution, high charge-discharge specific capacity, and stable cycle performance.

[0032] When the single-crystal cathode material is a nickel-based cathode material, the chemical formula can be, for example, but not limited to, LiNiO2, LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 O2, LiNi 0.4 Co 0.2 Mn 0.4 O2, LiNi 0.5 Co 0.2 Mn 0.3 O2, LiNi 0.6 Co 0.2 Mn 0.2 O2, LiNi 0.7 Co 0.1 Mn 0.2 O2, LiNi 0.8 Co 0.1 Mn 0.1 O2, LiNi 0.8 Mn 0.2 O2 or LiNi 0.9 Co 0.1 At least one of O2.

[0033] When the single-crystal cathode material is a manganese-based cathode material, its chemical formula can be, for example, but is not limited to, Li. 1.2 Ni 0.13 Co 0.13 Mn 0.54 O2 or LiNi 0.2 Co 0.2 Mn 0.6 At least one of O2.

[0034] When the single-crystal cathode material is a cobalt-based cathode material, its chemical formula can be, for example, LiNi. 0.1 Co 0.9 O2 or LiMn 0.1 Co 0.9 O2.

[0035] Preferably, the single-crystal cathode material further includes anions (BO3). 3- F - ,Br - Cl - PO4 3- (etc.) and / or cations (V 3+ Ta 4+ Zr 4+ Ce 4+ Mo 6+ Y 3+ La 3+ (etc.) replacement or doping situations.

[0036] Preferably, the particle size of the single-crystal cathode material is 1–13 μm.

[0037] In some specific embodiments, the particle size of the single-crystal cathode material can be, for example, but not limited to, 1μm, 2μm, 3μm, 4μm, 5μm, 6μm, 7μm, 8μm, 9μm, 10μm, 12μm or 13μm.

[0038] Another aspect of the present invention relates to a method for preparing the aforementioned single-crystal cathode material, comprising the following steps:

[0039] (a) A co-precipitation reaction was carried out after adding a precipitant to solution A containing soluble salt to obtain nanoparticle precursors;

[0040] (b) The mixture of the nanoparticle precursor and molten salt is sintered, granulated, and washed to obtain single-crystal particles;

[0041] The sintering temperature is 850–1000℃; the sintering time is 1–5 hours.

[0042] (c) The mixture of the single crystal particles and the lithium source is calcined;

[0043] The calcination temperature is 650–950℃; the calcination time is 3–10 h.

[0044] In some specific embodiments, the sintering temperature may be, for example, but not limited to, 850°C, 860°C, 870°C, 880°C, 890°C, 900°C, 910°C, 920°C, 930°C, 940°C, 950°C, 960°C, 970°C, 980°C, 990°C, or 1000°C.

[0045] In some specific embodiments, the sintering time can be, for example, 1h, 1.5h, 2h, 2.5h, 3h, 3.5h, 4h, 4.5h or 5h.

[0046] In some specific embodiments, the calcination temperature may be, for example, but not limited to, 650°C, 660°C, 670°C, 680°C, 690°C, 700°C, 710°C, 720°C, 730°C, 740°C, 750°C, 760°C, 770°C, 780°C, 790°C, 800°C, 810°C, 820°C, 830°C, 840°C, 850°C, 860°C, 870°C, 880°C, 890°C, 900°C, 910°C, 920°C, 930°C, 940°C, or 950°C.

[0047] In some specific embodiments, the calcination time can be, for example, but not limited to, 3h, 4h, 5h, 6h, 7h, 8h, 9h or 10h.

[0048] The method for preparing the single-crystal cathode material utilizes a rapid granulation reaction of nanoparticle precursors in a molten salt environment to prepare micron-sized single-crystal large-particle electrode material for lithium-ion batteries. Although existing technologies have reported the use of CoCO3 and Ni... x Co y Mn 1-x-y Single-crystal cathode materials can be prepared using precursors such as (OH)2 via the molten salt method, but this method has a long reaction time and requires specific reaction conditions, such as the use of CoCO3 and Ni. x Co y Mn 1-x-yThe high requirements for precursors such as (OH)2 lead to higher production costs compared to conventional spherical cathode materials, hindering the development of single-crystal cathode materials. Furthermore, using multiple oxides to prepare single-crystal cathode materials through solid-phase mixing followed by molten salt preparation results in uneven internal composition and severe segregation, significantly impacting battery performance. The rapid preparation strategy proposed in this invention not only ensures uniform distribution of elemental components within the cathode material and rapid, simple preparation of nanoparticle precursors, but also yields micron-sized, large-particle single-crystal cathode materials with excellent electrochemical performance within a very short reaction time, significantly improving production capacity and reducing production costs.

[0049] This method can also be used to prepare cathode materials containing anions, cations, or doping.

[0050] Preferably, the sintering, granulation, and calcination are carried out in an air or oxygen atmosphere, without the need for a special protective atmosphere, thus reducing costs.

[0051] Preferably, the amount of the soluble salt contained in solution A is determined according to the chemical formula of the target cathode material.

[0052] Soluble salts are weighed and dissolved in water according to the designed stoichiometric ratio to prepare a solution with a molar concentration of 0.1-10 mol / L. -1 Solution A contains soluble salts.

[0053] An excess of 10% molar amount of precipitant was added to solution A to prepare nanoparticle precursors with a size not exceeding 800 nm.

[0054] Preferably, the molar ratio of the molten salt to the transition metal ions in the nanoparticle precursor is >1.2.

[0055] In some specific embodiments, the molar ratio of the molten salt to the transition metal ions in the nanoparticle precursor can be, for example, but not limited to, 1.2, 2.4, 3.6, 4.8, 5.6, 6.4 or 6.8.

[0056] Preferably, the molar ratio of lithium salt in the molten salt to transition metal ions in the nanoparticle precursor is >0.7.

[0057] In some specific embodiments, the molar ratio of lithium salt in the molten salt to transition metal ions in the nanoparticle precursor can be, for example, but not limited to, 0.7, 1.5, 2.0, 2.5, 3.0, 3.5, 4.0 or 4.5.

[0058] Preferably, the sintering heating rate is 2 to 10 °C / min.

[0059] In some specific embodiments, the heating rate of the sintering can be, for example, but not limited to, 2℃ / min, 3℃ / min, 4℃ / min, 5℃ / min, 6℃ / min, 7℃ / min, 8℃ / min, 9℃ / min or 10℃ / min.

[0060] Preferably, the heating rate of the calcination is 2 to 10 °C / min.

[0061] In some specific embodiments, the heating rate of the calcination can be, for example, but not limited to, 2℃ / min, 3℃ / min, 4℃ / min, 5℃ / min, 6℃ / min, 7℃ / min, 8℃ / min, 9℃ / min or 10℃ / min.

[0062] Preferably, the size of the nanoparticle precursor in the largest direction is ≤800nm.

[0063] In some specific embodiments, the size of the nanoparticle precursor in the largest direction can be, for example, but not limited to, 400nm, 230nm, 110nm, 470nm, 330nm, 170nm or 280nm.

[0064] The size of the nanoparticle precursor in the largest direction should be controlled within a certain range. If it exceeds 800 nm, the time required for the precursor particles to generate single crystal particles will increase significantly, failing to achieve the effect of rapid preparation into large particles. Furthermore, the distribution of metal elements is also prone to segregation, resulting in an uneven distribution.

[0065] The precursor particles used in this invention are less than 1 μm in size and have no specific morphology requirements. They only need to be small in size so that they can easily promote the diffusion of metal ions between particles during molten salt calcination, thus enabling faster melting growth to form large single-crystal particles.

[0066] Preferably, the shape of the nanoparticle precursor includes, but is not limited to, spindle-shaped, rice-grain-shaped, spherical, rod-shaped, needle-shaped, sheet-shaped, or irregular particles.

[0067] Preferably, the soluble salt includes at least one of a soluble nickel salt, a soluble cobalt salt, or a soluble salt of the metal element Me;

[0068] Preferably, the soluble salt includes at least one of nitrate, sulfate, or chloride.

[0069] Preferably, the molten salt comprises at least one of lithium oxide, lithium carbonate, lithium sulfate, lithium nitrate, lithium acetate, lithium hydroxide, lithium oxalate, or lithium chloride.

[0070] Preferably, the molten salt may also be a molten salt formed by mixing one or more of sodium / potassium carbonates, nitrates, chlorides, and sulfates with lithium salts.

[0071] Preferably, the precipitant comprises at least one of the following: sodium carbonate, sodium bicarbonate, ammonium carbonate, ammonium bicarbonate, sodium oxalate, ammonium oxalate, sodium hydroxide, potassium hydroxide, ammonia, sodium citrate, potassium citrate, or citric acid.

[0072] Preferably, the lithium source includes at least one of lithium hydroxide, lithium carbonate, lithium sulfate, lithium nitrate, lithium acetate, lithium oxalate, or lithium chloride.

[0073] Another aspect of the present invention relates to a positive electrode sheet, comprising the aforementioned single-crystal positive electrode material or a single-crystal positive electrode material prepared by the method for preparing the aforementioned single-crystal positive electrode material.

[0074] Another aspect of the present invention relates to a lithium-ion battery, including the aforementioned lithium-ion battery.

[0075] The lithium-ion battery described above exhibits excellent electrochemical performance.

[0076] The embodiments of the present invention will now be described in detail with reference to specific examples and comparative examples.

[0077] Example 1: Rapid preparation of single-crystal LiNi 0.6 Co 0.2 Mn 0.2 O2 cathode material

[0078] Weigh out 30 mmol of nickel acetate, 10 mmol of cobalt acetate, and 10 mmol of manganese acetate according to the metal ion molar ratio of nickel:cobalt:manganese = 60:20:20. Dissolve them together in 75 mL of deionized water to prepare solution A. Add 100 mmol of oxalic acid to solution A, stir and react for 30 min. After filtration and drying, the nanoparticle precursor is obtained.

[0079] The above-mentioned nanoparticle precursor powder was mixed and ground with molten salt (lithium carbonate and sodium sulfate in a molar ratio of 1:1) in a molar ratio of 1:2.8, and then sintered in air at 6°C for 1 minute. -1 The temperature was rapidly increased to 920℃ and held for 2 hours, then cooled to room temperature to obtain a mixture of single crystal particles and molten salt. The soluble lithium salt in the mixture was then washed away with deionized water to obtain single crystal particle powder, which was then dried in an oven.

[0080] The dried single-crystal powder particles were mixed with lithium hydroxide and calcined in a tube furnace (oxygen atmosphere). The mixture was then held at 750°C for 5 hours and cooled to room temperature in the furnace to obtain single-crystal LiNi with accurate lithium content and a well-preserved layered structure.0.6 Co 0.2 Mn 0.2 O2 cathode material.

[0081] Example 2: Rapid preparation of single-crystal Li 1.2 Ni 0.19 Mn 0.6 Sr 0.01 O2 cathode material

[0082] Weigh out 9.5 mmol of nickel sulfate, 30 mmol of manganese acetate, and 0.5 mmol of strontium nitrate according to the metal ion molar ratio of nickel:manganese:strontium = 19:60:1, and dissolve them together in 75 mL of deionized water to prepare solution A. Add 80 mmol of sodium oxalate to solution A, stir and react for 30 min, filter and dry to obtain the nanoparticle precursor.

[0083] The above-mentioned nanoparticle precursor powder was mixed and ground with molten salt (lithium carbonate and sodium sulfate in a molar ratio of 1:1) in a molar ratio of 1:2.9, and then sintered in air at 6°C for 1 minute. -1 The temperature was rapidly increased to 950℃ and held for 2 hours, then cooled to room temperature to obtain a mixture of single crystal particles and molten salt. The soluble lithium salt in the mixture was then washed away with deionized water to obtain single crystal particle powder, which was then dried in an oven.

[0084] The dried single-crystal powder particles were mixed with lithium hydroxide and calcined in a tube furnace (oxygen atmosphere). The mixture was then held at 850℃ for 5 hours, and finally cooled to room temperature in the furnace to obtain single-crystal Li with accurate lithium content and a well-preserved layered structure. 1.2 Ni 0.19 Mn 0.6 Sr 0.01 O2 cathode material.

[0085] Example 3: Rapid preparation of single-crystal LiNi 0.75 Co 0.24 Al 0.01 O2 cathode material

[0086] Weigh out 32.5 mmol of nickel sulfate, 12 mmol of cobalt acetate, and 0.5 mmol of aluminum acetylacetonate according to the metal ion molar ratio of nickel:manganese:aluminum = 75:24:1, and dissolve them together in 60 mL of deionized water to prepare solution A. Add 80 mmol of sodium carbonate to solution A, stir and react for 30 min, filter and dry to obtain the nanoparticle precursor.

[0087] The above-mentioned nanoparticle precursor powder was mixed and ground with molten salt (lithium nitrate and sodium chloride in a molar ratio of 1:1) at a molar ratio of 1:2.7, and then sintered in air at 5°C for 1 minute. -1The temperature was rapidly increased to 910℃ and held for 2 hours, then cooled to room temperature to obtain a mixture of single crystal particles and molten salt. The soluble lithium salt in the mixture was then washed away with deionized water to obtain single crystal particle powder, which was then dried in an oven.

[0088] The dried single-crystal powder particles were mixed with lithium hydroxide and calcined in a tube furnace (oxygen atmosphere). The mixture was then held at 740℃ for 5 hours and subsequently cooled to room temperature in the furnace to obtain single-crystal LiNi with accurate lithium content and a well-preserved layered structure. 0.75 Co 0.24 Al 0.01 O2 cathode material.

[0089] Example 4: Rapid preparation of single-crystal LiNi 0.90 Mn 0.0.09 Mg 0.01 O2 cathode material

[0090] Weigh out 45 mmol of nickel nitrate, 4.5 mmol of manganese nitrate, and 0.5 mmol of magnesium nitrate according to the molar ratio of nickel:manganese:magnesium = 90:9:1, and dissolve them together in 70 mL of deionized water to prepare solution A. Add 140 mmol of sodium hydroxide to solution A, stir and react for 30 min, filter and dry to obtain the nanoparticle precursor.

[0091] The above-mentioned nanoparticle precursor powder was mixed and ground with molten salt (lithium acetate and sodium nitrate in a molar ratio of 1:1) in a molar ratio of 1:2.8, and then sintered in air at 5°C for 1 minute. -1 The temperature was rapidly increased to 890℃ and held for 2 hours, then cooled to room temperature to obtain a mixture of single crystal particles and molten salt. The soluble lithium salt in the mixture was then washed away with deionized water to obtain single crystal particle powder, which was then dried in an oven.

[0092] The dried single-crystal powder particles were mixed with lithium hydroxide and calcined in a tube furnace (oxygen atmosphere). The mixture was then held at 650°C for 4 hours and cooled to room temperature in the furnace to obtain single-crystal LiNi with accurate lithium content and a well-preserved layered structure. 0.90 Mn 0.0.09 Mg 0.01 O2 cathode material.

[0093] Example 5: Rapid preparation of single-crystal LiNi 0.16 Co 0.10 Mn 0.54 O2 cathode material

[0094] Weigh out 8 mmol of nickel chloride, 5 mmol of cobalt nitrate, and 27 mmol of manganese chloride according to the metal ion molar ratio of nickel:cobalt:manganese = 16:10:54, and dissolve them together in 60 mL of deionized water to prepare solution A. Add 140 mmol of sodium citrate to solution A, stir and react for 30 min, filter and dry to obtain the nanoparticle precursor.

[0095] The above-mentioned nanoparticle precursor powder was mixed and ground with molten salt (lithium acetate to sodium chloride molar ratio of 1:1) at a molar ratio of 1:2.9, and then sintered in air at 8°C for 1 minute. -1 The temperature was rapidly increased to 960℃ and held for 3 hours, then cooled to room temperature to obtain a mixture of single crystal particles and molten salt. The soluble lithium salt in the mixture was then washed away with deionized water to obtain single crystal particle powder, which was then dried in an oven.

[0096] The dried single-crystal powder particles were mixed with lithium carbonate and calcined in air, then held at 850°C for 5 hours, and finally cooled to room temperature in the furnace to obtain single-crystal LiNi with accurate lithium content and intact layered structure. 0.16 Co 0.1 Mn 0.54 O2 cathode material.

[0097] Example 6: Rapid preparation of single-crystal LiNi 0.33 Co 0.33 Mn 0.33 O2 cathode material

[0098] Weigh out 16.5 mmol of nickel chloride, 16.5 mmol of cobalt chloride, and 16.5 mmol of manganese nitrate according to the molar ratio of nickel:cobalt:manganese = 16.5:16.5:16.5, and dissolve them together in 60 mL of deionized water to prepare solution A. Add 140 mmol of sodium citrate to solution A, stir and react for 30 min, filter and dry to obtain the nanoparticle precursor.

[0099] The above-mentioned nanoparticle precursor powder was mixed and ground with molten salt (lithium nitrate and potassium sulfate in a molar ratio of 1:1) at a molar ratio of 1:3.0, and then sintered in air at 8°C for 1 minute. -1 The temperature was rapidly increased to 970℃ and held for 3 hours, then cooled to room temperature to obtain a mixture of single crystal particles and molten salt. The soluble lithium salt in the mixture was then washed away with deionized water to obtain single crystal particle powder, which was then dried in an oven.

[0100] The dried single-crystal powder particles were mixed with lithium carbonate and calcined in air, then held at 960℃ for 5 hours, and finally cooled to room temperature in the furnace to obtain single-crystal LiNi with accurate lithium content and intact layered structure. 0.33 Co0.33 Mn 0.33 O2 cathode material.

[0101] Example 7: Rapid preparation of single-crystal LiNi 0.02 Co 0.96 Mn 0.02 O2 cathode material

[0102] Weigh out 0.1 mmol of nickel chloride, 43 mmol of cobalt chloride, and 0.1 mmol of manganese nitrate according to the molar ratio of nickel:cobalt:manganese = 0.2:96:0.2, and dissolve them together in 60 mL of deionized water to prepare solution A. Add 140 mmol of citric acid to solution A, stir and react for 30 min, filter and dry to obtain the nanoparticle precursor.

[0103] The above-mentioned nanoparticle precursor powder was mixed and ground with molten salt (lithium sulfate and lithium hydroxide in a molar ratio of 1:1) at a molar ratio of 1:2.4, and then sintered in air at 8°C for 1 minute. -1 The temperature was rapidly increased to 1000℃ and held for 2 hours, then cooled to room temperature to obtain a mixture of single crystal particles and molten salt. The soluble lithium salt in the mixture was then washed away with deionized water to obtain single crystal particle powder, which was then dried in an oven.

[0104] The dried single-crystal powder particles were mixed with lithium carbonate and calcined in air, then held at 1000℃ for 5 hours, and finally cooled to room temperature in the furnace to obtain single-crystal LiNi with accurate lithium content and intact layered structure. 0.05 Co 0.9 Mn 0.05 O2 cathode material.

[0105] Experimental Example

[0106] Figure 1 The single-crystal LiNi in Example 1 of this invention 0.6 Co 0.2 Mn 0.2 FESEM image of O2 cathode material. LiNi is clearly visible in the image. 0.6 Co 0.2 Mn 0.2 The O2 cathode material particles are micron-sized, with smooth surfaces, and are single-crystal particles.

[0107] Figure 2 The single-crystal Li in Example 2 of this invention 1.2 Ni 0.19 Mn 0.6 Sr 0.01 FESEM image of the O2 cathode material. Li can be seen. 1.2 Ni 0.19 Mn0.6 Sr 0.01 The O2 cathode material particles are micron-sized single-crystal large particles with smooth surfaces.

[0108] Figure 3 The single-crystal LiNi in Example 1 of this invention 0.6 Co 0.2 Mn 0.2 XRD pattern of O2 cathode material. Its diffraction peaks match the layered structure of α-NaFeO2. The two pairs of diffraction peaks (006) / (012) and (018) / (110) are clearly split, indicating that the single-crystal LiNi is formed after lithium supplementation and calcination. 0.6 Co 0.2 Mn 0.2 O2 cathode materials have a good layered structure.

[0109] Figure 4 The single-crystal Li in Example 2 of this invention 1.2 Ni 0.19 Mn 0.6 Sr 0.01 XRD pattern of O2 cathode material. Its diffraction peaks match the layered structure of α-NaFeO2, and superlattice diffraction peaks belonging to Li2MnO3 are observed in the 20-25° range. The diffraction peaks of (006) / (012) and (018) / (110) are clearly separated, indicating that the single-crystal Li2 with good layered structure is obtained after calcination with additional lithium ions. 1.2 Ni 0.19 Mn 0.6 Sr 0.01 O2 cathode material.

[0110] The monocrystalline cathode materials from Examples 1 and 2 were dispersed in an organic solvent at a mass ratio of 90:5:5 with conductive carbon black and polyvinylidene fluoride binder to form a slurry. The slurry was then coated onto an aluminum foil substrate, dried, rolled, and cut into 1.0 cm diameter electrode discs for use as cathode sheets. The cathode sheets, separator, and lithium foil were assembled into a coin cell in a sealed glove box, and the battery performance was tested using an electrochemical testing instrument.

[0111] Figure 5 The single-crystal LiNi in Example 1 of this invention 0.6 Co 0.2 Mn 0.2 The cycling performance of O2 cathode material at 1C current density is shown in the figure. As can be seen from the figure, single-crystal LiNi... 0.6 Co 0.2 Mn 0.2The O2 cathode material exhibits excellent long-term cycling stability within a voltage range of 2.8-4.3V and a current density of 1C, achieving an initial discharge capacity of 160.9 mAh g. -1 After 200 cycles, the capacity remained at 137.7 mAh g. -1 It achieved a capacity retention rate of 85.6%.

[0112] Figure 6 Single-crystal Li in Embodiment 2 of the present invention 1.2 Ni 0.19 Mn 0.6 Sr 0.01 Cycling performance of the O2 cathode material at 1C current density. The first discharge capacity of this single-crystal cathode material at 1C current density is 220.4 mAh g / L in the voltage range of 2.8-4.8V. -1 After 200 cycles, the capacity reached 207.5 mAh g. -1 The corresponding capacity retention rate is as high as 94.1%, demonstrating excellent long-cycle performance.

[0113] Tests show that the cathode materials prepared in the other examples all have the morphology of micron-sized single crystal large particles and have high charge-discharge specific capacity and cycle stability.

[0114] Although the present invention has been illustrated and described with specific embodiments, it should be understood that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; those skilled in the art should understand that modifications can 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, without departing from the spirit and scope of the present invention; and these 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; therefore, this means that all such substitutions and modifications that fall within the scope of the present invention are included in the appended claims.

Claims

1. A method for preparing a single-crystal cathode material, characterized in that, The chemical formula of this single-crystal cathode material is LiNi. x Co y Me 1-x-y O2; Wherein, 0≤x, 0≤y, 0<x+y≤1, and Me includes at least one of Al, Ti, Mg, Sr, W, Ca, Nb, Cr, Mn, or Fe; The preparation method of this single-crystal cathode material includes the following steps: (a) A co-precipitation reaction was carried out after adding a precipitant to solution A containing soluble salts to obtain nanoparticle precursors; (b) The mixture of the nanoparticle precursor and molten salt is sintered, granulated, and washed to obtain single-crystal particles; The sintering temperature is 850~1000℃; the sintering time is 1~5h; (c) The mixture of the single crystal particles and the lithium source is calcined; The calcination temperature is 650~950℃; the calcination time is 3~10h; The maximum dimension of the nanoparticle precursor is ≤800nm.

2. The method for preparing the single-crystal cathode material according to claim 1, characterized in that, The particle size of the single-crystal cathode material is 1~13μm.

3. The method for preparing the single-crystal cathode material according to claim 1, characterized in that, The molar ratio of the molten salt to the transition metal ions in the nanoparticle precursor is >1.

2.

4. The method for preparing the single-crystal cathode material according to claim 1, characterized in that, The molar ratio of lithium salt in the molten salt to transition metal ions in the nanoparticle precursor is >0.

7.

5. The method for preparing the single-crystal cathode material according to claim 1, characterized in that, The sintering heating rate is 2~10℃ / min.

6. The method for preparing the single-crystal cathode material according to claim 1, characterized in that, The heating rate of the calcination is 2~10℃ / min.

7. The method for preparing the single-crystal cathode material according to claim 1, characterized in that, The soluble salt includes at least one of the following: soluble nickel salt, soluble cobalt salt, or soluble salt of the metal element Me.

8. The method for preparing the single-crystal cathode material according to claim 1, characterized in that, The soluble salt includes at least one of nitrate, sulfate, or chloride.

9. The method for preparing the single-crystal cathode material according to claim 1, characterized in that, The molten salt includes at least one of lithium oxide, lithium carbonate, lithium sulfate, lithium nitrate, lithium acetate, lithium hydroxide, lithium oxalate, or lithium chloride.

10. The method for preparing the single-crystal cathode material according to claim 1, characterized in that, The precipitant includes at least one of the following: sodium carbonate, sodium bicarbonate, ammonium carbonate, ammonium bicarbonate, sodium oxalate, ammonium oxalate, sodium hydroxide, potassium hydroxide, ammonia, sodium citrate, potassium citrate, or citric acid.

11. The method for preparing the single-crystal cathode material according to claim 1, characterized in that, The lithium source includes at least one of lithium hydroxide, lithium carbonate, lithium sulfate, lithium nitrate, lithium acetate, lithium oxalate, or lithium chloride.

12. A positive electrode plate, characterized in that, The single-crystal cathode material prepared by the method for preparing single-crystal cathode material according to any one of claims 1 to 11.

13. A lithium-ion battery, characterized in that, Includes the positive electrode sheet as described in claim 12.

Images