Cobalt-free monocrystal lithium-rich manganese-based positive electrode material, preparation method and application thereof

Abstract

The invention relates to a cobalt-free monocrystal lithium-rich manganese-based positive electrode material, a preparation method and application thereof, and belongs to the technical field of lithium ion battery positive electrode materials, the chemical formula of the cobalt-free monocrystal lithium-rich manganese-based positive electrode material is Li < x > Ni < y > Mn < z > O < 2 >, wherein x is greater than or equal to 1.1 and less than or equal to 1.5, y is greater than or equal to 0.2 and less than or equal to 0.5, and z is greater than or equal to 0.4 and less than or equal to 0.8. According to the preparation method, the submicron cobalt-free monocrystal lithium-rich manganese-based positive electrode material is prepared through a high-temperature solid-phase sintering method after lithium salt is added into a precursor for ball milling, the preparation process is simple, the cost is low, the production efficiency is high, and the prepared submicron cobalt-free monocrystal lithium-rich manganese-based positive electrode material is uniform in distribution and high in crystallinity; the preparation method provided by the invention does not have the problem of carbon emission, and meanwhile, the prepared positive electrode material has higher compaction density.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of lithium ion battery cathode materials, and particularly relates to a cobalt-free single-crystal lithium-rich manganese-based cathode material, a preparation method and application thereof. BACKGROUND

[0002] The lithium-rich manganese-based cathode material is one of ideal options for the next generation of high-energy-density cathode materials due to its high specific capacity and relatively low cost. At present, the lithium-rich manganese-based cathode material prepared from a carbonate precursor is loose and porous, and has a large specific surface area, which leads to a low tap density and makes it difficult to achieve a higher volumetric energy density. Meanwhile, the lithium-rich manganese-based cathode material prepared from an existing hydroxide precursor is mainly in a polycrystalline morphology composed of secondary particle agglomeration, and the side reaction between the electrolyte and the cathode material during the charging and discharging cycle process aggravates the generation of microcracks, further damages the stability of the material, and leads to rapid capacity and voltage decay, poor cycle and rate performance.

[0003] In view of this, the single-crystal lithium-rich manganese-based cathode material has a stable layered structure and a small specific surface area, inhibits the generation of microcracks during the cycle process, has a high thermal decomposition temperature and a small amount of gas production, and has good cycle stability and thermal stability. In addition, the single-crystal lithium-rich manganese-based cathode material can effectively alleviate the phase change from a layered structure to a spinel structure during the cycle process, and inhibit the voltage decay problem. However, the size of the single-crystal lithium-rich manganese cathode material particle has a great influence on its performance. The micron-level single-crystal particle size (~ 3 µm) will aggravate the degree of Li / Ni mixing, leading to inevitable kinetic hysteresis and structural damage. In addition, the long diffusion path not only limits the effective transfer of lithium ions, but also significantly weakens the negative ion redox kinetics. Meanwhile, the content of fine powder in the finished product should be strictly controlled during the preparation of the single-crystal lithium-rich manganese-based cathode material. These fine powder particles may be composed of particles with irregular morphology or particle size less than 0.5 µm, and their presence will bring safety hazards to the use of the cathode material. SUMMARY

[0004] In view of the above problems, the present application provides a cobalt-free single-crystal lithium-rich manganese-based cathode material, a preparation method and application thereof. The present application adopts a precursor plus lithium salt ball milling, and then a high-temperature solid-phase sintering method to prepare a submicron cobalt-free single-crystal lithium-rich manganese-based cathode material. The preparation process is simple, the cost is low, the production efficiency is high, the prepared submicron cobalt-free single-crystal lithium-rich manganese-based cathode material is uniformly distributed, has high crystallinity, good consistency and stability, and can achieve a higher tap density.

[0005] The present application provides a cobalt-free single-crystal lithium-rich manganese-based cathode material, the chemical formula of which is Li x Ni y Mn zO2; wherein, 1.1≤x≤1.5, 0.2≤y≤0.5, 0.4≤z≤0.8.

[0006] Optionally, x=1.2, y=0.2, z=0.6.

[0007] The second object of the present application is to provide a preparation method of a cobalt-free single-crystal lithium-rich manganese-based positive electrode material, comprising: Step 1, mixing and uniformly grinding a nickel-manganese hydroxide precursor and a lithium salt to obtain a mixture one; Step 2, transferring the mixture one to a ball mill to perform high-energy ball milling to obtain a mixture two; Step 3, sintering, heat preservation and cooling the mixture two to obtain an original cobalt-free single-crystal lithium-rich manganese-based positive electrode material; Step 4, chemically modifying the original cobalt-free single-crystal lithium-rich manganese-based positive electrode material to obtain a cobalt-free single-crystal lithium-rich manganese-based positive electrode material.

[0008] Optionally, the chemical formula of the nickel-manganese hydroxide precursor in step 1 is Ni a Mn b (OH)2, wherein, 0.2≤a≤0.45, 0.55≤b≤0.8, a+b=1.

[0009] Optionally, the lithium salt in step 1 comprises lithium hydroxide, lithium carbonate, lithium nitrate and / or lithium chloride.

[0010] Optionally, the molar ratio of the nickel-manganese hydroxide precursor to the lithium salt in step 1 is 1:1.15-1.55.

[0011] Optionally, the particle size of the nickel-manganese hydroxide precursor is 8-10 um, and the particle size of the nickel-manganese hydroxide precursor in the mixture one is 400-600 nm.

[0012] Optionally, the particle size of the nickel-manganese hydroxide precursor in the mixture one is 400-600 nm.

[0013] Optionally, the sintering temperature is 700-1100°C, and the heat preservation time is 8-30h.

[0014] The third object of the present application is to provide an application of a cobalt-free single-crystal lithium-rich manganese-based positive electrode material.

[0015] Optionally, the cobalt-free single-crystal lithium-rich manganese-based positive electrode material is applied to electric vehicles, energy storage systems, low-altitude economy and consumer electronics.

[0016] Compared with the prior art, the present application has at least the following beneficial effects: The application applies a high-temperature solid-phase sintering method to the preparation of a cobalt-free single-crystal lithium-rich manganese-based positive electrode material, has the advantages of simple process flow, uniform particles, regular morphology, etc., and the prepared single-crystal lithium-rich manganese-based positive electrode material has uniform size, high discharge capacity and good cycle performance; (2) the application uses nickel-manganese hydroxide as a precursor, mixes with lithium salt, and sintered after ball milling to prepare a cobalt-free lithium-rich manganese-based positive electrode material, which has no carbon emission problem, and the prepared positive electrode material has higher compaction density; (3) the application shortens the sintering time in the sintering process, reduces energy consumption, and makes lithium insertion more complete, so that the prepared cobalt-free single-crystal lithium-rich manganese-based positive electrode material has a good layered structure; (4) the preparation process of the application is simple, the reaction is easy to control, the equipment requirement is low, batch production is possible, and the prepared product has good consistency and high production efficiency. BRIEF DESCRIPTION OF DRAWINGS

[0017] The accompanying drawings are included to provide a further understanding of the application and are incorporated in and constitute a part of this specification, illustrate embodiments of the application and together with the description serve to explain the principles of the application.

[0018] Figure 1 The XRD diagram of the cobalt-free single-crystal lithium-rich manganese-based positive electrode material prepared in Example 1 of the application is shown in the schematic diagram. Figure 2 The SEM diagram of the cobalt-free single-crystal lithium-rich manganese-based positive electrode material prepared by the method of Example 1 of the application is shown in the schematic diagram. Figure 3 The cycle performance diagram of the cobalt-free single-crystal lithium-rich manganese-based positive electrode material prepared by the method of Example 1 of the application is shown in the schematic diagram. Figure 4 The XRD diagram of the polycrystalline lithium-rich manganese-based positive electrode material prepared by the method of Comparative Example 1 of the application is shown in the schematic diagram. Figure 5 The SEM diagram of the polycrystalline lithium-rich manganese-based positive electrode material prepared by the method of Comparative Example 1 of the application is shown in the schematic diagram. Figure 6 The XRD diagram of the polycrystalline lithium-rich manganese-based positive electrode material prepared by the method of Comparative Example 2 of the application is shown in the schematic diagram. Figure 7 The SEM diagram of the polycrystalline lithium-rich manganese-based positive electrode material prepared by the method of Comparative Example 2 of the application is shown in the schematic diagram. Figure 8 The cycle performance diagram of Example 1, Example 4, Example 6 and Comparative Example 1 of the application is shown in the schematic diagram. DETAILED DESCRIPTION

[0019] In order to enable a more clear understanding of the above-mentioned purposes, features and advantages of the present application, the present application will be further described in detail below in conjunction with the accompanying drawings and specific embodiments. It should be noted that the embodiments of the present application and the features in the embodiments can be combined with each other without conflict. In addition, the present application can also be implemented in other ways different from those described herein, and therefore, the protection scope of the present application is not limited by the specific embodiments disclosed below.

[0020] One specific embodiment of the present application, as Figures 1-8 disclosed a kind of cobalt-free single crystal lithium-rich manganese-based positive electrode material, preparation method and application, specific implementation steps are as follows: A kind of preparation method of cobalt-free single crystal lithium-rich manganese-based positive electrode material, comprising the following steps: Step 1, nickel manganese hydroxide precursor is mixed with lithium salt and uniformly ground, to obtain mixture one; Optionally, the particle size of the nickel manganese hydroxide precursor is 8-10 um; The particle size of the nickel manganese hydroxide precursor in the mixture one is 400-600 nm; The technical scheme of the present application mixes the nickel manganese hydroxide precursor with large particle size with lithium salt and uniformly grinds, grinds the nickel manganese hydroxide precursor with small particle size of 400-600 nm, which is beneficial to the nickel manganese hydroxide precursor and lithium salt to be mixed uniformly, and then form small particle size single crystal lithium-rich manganese in the sintering process.

[0021] Step 2, mixture one is transferred to a ball mill, high-energy ball milling is carried out, and mixture two is obtained; Step 3, mixture two is placed in a box furnace with air atmosphere for sintering, heat preservation, and cooling to room temperature in the box furnace, to obtain the original cobalt-free single crystal lithium-rich manganese-based positive electrode material; Step 4, the original cobalt-free single crystal lithium-rich manganese-based positive electrode material is placed in a weak acid solvent or a salt solution for chemical modification treatment, to obtain the cobalt-free single crystal lithium-rich manganese-based positive electrode material. Optionally, the weak acid solvent is phosphoric acid or acetic acid; The salt solution is ammonium persulfate, ammonium fluoride or ammonium dihydrogen phosphate; Further, the concentration of the weak acid solution is 4%-16%, the stirring time is 8-24h, and the stirring rate is 300-800rmp / min; The concentration of the salt solution is 4%-16%, the stirring time is 8-24h, and the stirring rate is 300-800rmp / min.

[0022] Optionally, the chemical formula of the nickel manganese hydroxide precursor in step 1 is Ni a Mn b(OH) 2, wherein 0.2≤a≤0.45, 0.55≤b≤0.8, a+b=1.

[0023] Optionally, the lithium salt in step 1 is lithium hydroxide, lithium carbonate, lithium nitrate or lithium chloride.

[0024] Optionally, a temperature sensor is included in the box furnace, and the crucible containing the nickel-manganese hydroxide precursor and the lithium salt is placed below the temperature sensor to ensure that the theoretical temperature is consistent with the actual sintering temperature, thereby avoiding errors caused by inaccurate temperature sensor testing.

[0025] Optionally, the molar ratio of the nickel-manganese hydroxide precursor to the lithium salt in step 1 is 1:1.15-1.55.

[0026] Optionally, the rotation speed of the ball mill is 300-800 rmp / min, and the ball milling time is 3-12h. Optionally, the sintering temperature is 700-1100 °C, the heating rate is 2-15 °C / min, and the holding time is 8-30h. Further, the heating rate is 8-15℃ / min. Further, the holding temperature is 800-900℃. Further, the heating rate includes a fast heating rate and a slow heating rate. The fast heating rate is 8-15℃ / min. The slow heating rate is 2-8℃ / min.

[0027] In the present application, when the heating rate is selected to be 8-15℃ / min, the mixture can be rapidly heated to the high-temperature zone, and Li⁺, Mn 4 + and other active components are generated by the decomposition of the mixture, a large number of crystal nuclei are formed in a short time, and a large number of nanoscale or submicron small particles with uniform distribution are obtained. In addition, rapid heating to the high-temperature zone shortens the residence time of the particles in the low-temperature zone, reduces the Ostwald ripening effect of the dissolution of small particles to the growth of large particles, maintains the size uniformity of the single crystal structure D90 / D10<1.5, and inhibits the grain coarsening.

[0028] In the present application, the sintering temperature determines the atomic diffusion ability and phase stability. When the temperature is in the medium-high temperature range of 800-900℃, it is the most suitable range for single crystal growth. The atomic diffusion rate is improved, the grain grows through Ostwald ripening, submicron single crystal particles (0.3-1.5 μm) are formed, the particle size distribution is narrow, and the crystallinity is high (XRD half-peak width <0.1°), realizing the optimization of atomic diffusion and growth. High temperature of 800-900℃ promotes the reconstruction of crystal faces, forming a smooth polyhedron or near-spherical single crystal.

[0029] The application forms a cobalt-free lithium-rich manganese-based material with a layered structure as the main body and a Li2MnO3 nanodomain by high-temperature solid-phase sintering, in which a lithium salt and a precursor undergo a dynamic process of decomposition-diffusion-ordering, and finally form the cobalt-free lithium-rich manganese-based material.

[0030] In the process of high-temperature solid-phase sintering, at <400 DEG C, the metal oxides such as Mn3O4 in the nickel-manganese hydroxide precursor decompose in the heating process, release oxygen and form metastable transition metal oxides such as MnO with higher activity. The lithium salt melts at 300-400 DEG C to form a liquid phase medium of Li+ lithium ions, which penetrates into the precursor particles by capillary action, and reacts with the surface of the transition metal oxide to form an intermediate phase such as Li-Mn-O complex; at 400-700 DEG C, Li+ gradually embeds into the interstitial gap of the transition metal oxide lattice, replaces part of the transition metal ions such as Mn 4 + and Ni²+, and forms a lithium-rich Li x MO rock salt phase, wherein M is a transition metal or LiMn2O4 spinel phase. The redox reaction of transition metals such as Mn³+ releases oxygen to form oxygen vacancies, and the lattice gradually transitions from disorder to order; at 700-900 DEG C, the transition metals such as Mn and Ni and Li+ are rearranged by thermal diffusion to form a layered structure such as R-3m space group. In-furnace cooling is beneficial to the integrity of the single crystal structure. In the application, lithium ions of the lithium salt and the precursor are embedded in the high-temperature state to form a lithium-rich manganese-based positive electrode material with good layered structure. Through EDS test analysis, the elements of Ni, Mn and O in the lithium-rich manganese-based positive electrode material are uniformly distributed, and there is no local aggregation and segregation of elements.

[0031] The cobalt-free single-crystal lithium-rich manganese-based positive electrode material of the application can have a discharge specific capacity of about 250 mAh / g at 0.1C rate, and can be applied to electric vehicles, energy storage systems, low-altitude economy and electronic consumption.

[0032] The application controls the morphology and particle size of the single crystal by controlling the lithium ratio, the heating rate, the sintering temperature and the sintering time, and regulates the content of the two phases in the lithium-rich manganese-based positive electrode material.

[0033] The preparation method of the cobalt-free single-crystal lithium-rich manganese-based positive electrode material in the application is simple, the reaction is easy to control, the equipment requirement is low, and the material can be produced in batches. The synthesized single-crystal lithium-rich manganese-based positive electrode particles are uniform in size, have high discharge capacity and high compaction density, and have good cycle performance.

[0034] The application sets the amount of lithium salt and the sintering temperature, avoids that due to the too high amount of lithium salt and the too high sintering temperature, the single crystal lithium-rich manganese has a large particle size, the lithium-nickel mixing is serious, and the performance is poor. If the amount of lithium salt is too low and the sintering temperature is too low, the prepared single crystal lithium-rich manganese has a poor layered structure and low order, and also leads to poor electrochemical performance.

[0035] The second object of the application is to provide a cobalt-free single crystal lithium-rich manganese-based positive electrode material, the chemical formula of which is Li x Ni y Mn z O2; wherein, 1.1≤x≤1.5, 0.2≤y≤0.5, 0.4≤z≤0.8.

[0036] The particle size of the cobalt-free single crystal lithium-rich manganese-based positive electrode material is submicron.

[0037] The bulk phase and the surface of the cobalt-free single crystal lithium-rich manganese-based positive electrode material both include LiTMO2(C2 / m) phase and Li2MnO3(R-3m) phase, the Li, Ni, Mn and O elements in the material are uniformly distributed, and there is no phenomenon of element aggregation and segregation.

[0038] Alternatively, the chemical formula of the cobalt-free single crystal lithium-rich manganese-based positive electrode material is: Li 1.2 Ni 0.2 Mn 0.6 O2.

[0039] The application prepares the cobalt-free single crystal lithium-rich manganese-based positive electrode material, which has high discharge capacity, high compaction density and good electrochemical performance, and the material is low.

[0040] The third object of the application is to provide an application of the cobalt-free single crystal lithium-rich manganese-based positive electrode material in electric vehicles, energy storage systems, low-altitude economy and consumer electronics. The cobalt-free single crystal lithium-rich manganese positive electrode in the application has high discharge capacity and high compaction density, has high volume energy density and good cycle performance, and has great application prospect in electric vehicles, energy storage systems, low-altitude economy and consumer electronics, and with the breakthrough of solid-state battery technology and material genetic engineering, the lithium-rich manganese-based material is expected to become a key point for the dual goals of "de-cobaltization" and "high energy density" in the lithium battery industry.

[0041] Example 1 A preparation method of a cobalt-free single crystal lithium-rich manganese-based positive electrode material, the specific steps of which include: 1. Weigh 10 g of nickel-manganese hydroxide precursor, mix the nickel-manganese hydroxide precursor with lithium hydroxide at a molar ratio of 1:1.35, add 7.53 g of lithium hydroxide (20% excess lithium hydroxide), mix them evenly using a mixer, then transfer them to a ball mill and ball mill at 500 rpm for 5 hours for crushing treatment; 2. Transfer the crushed powder to a high-temperature resistant corundum boat with dimensions of 50*20*20 mm, spread it out, cut it into pieces, and then transfer it to a box furnace with an air atmosphere for sintering. The temperature was increased to 950 °C at a heating rate of 5 °C / min at room temperature and held for 20 h. The material was then naturally cooled to room temperature to obtain a cobalt-free single-crystal lithium-rich manganese-based cathode material.

[0042] Example 2 A method for preparing a cobalt-free single-crystal lithium-rich manganese-based cathode material, comprising the following steps: 1. Weigh 10 g of nickel manganese hydroxide precursor, mix the nickel manganese hydroxide precursor and lithium hydroxide in a molar ratio of 1:1.2, add 5.86 g of lithium hydroxide (5% excess lithium hydroxide), mix them evenly using a mixer, then transfer them to a ball mill and ball mill at 800 rpm for 3 hours for crushing treatment. 2. Transfer the crushed powder to a high-temperature resistant corundum boat with dimensions of 50*20*20 mm, spread it out, cut it into pieces, and then transfer it to a box furnace with an air atmosphere for sintering. The temperature was increased to 800 °C at a heating rate of 8 °C / min at room temperature and held for 12 h. The material was then naturally cooled to room temperature to obtain a cobalt-free single-crystal lithium-rich manganese-based cathode material.

[0043] Example 3 A method for preparing a cobalt-free single-crystal lithium-rich manganese-based cathode material, comprising the following steps: 1. Weigh 10 g of nickel manganese hydroxide precursor, mix the nickel manganese hydroxide precursor and lithium carbonate at a molar ratio of 1:1.15, add 5.18 g of lithium carbonate (10% excess lithium carbonate), mix them evenly using a mixer, then transfer them to a ball mill and ball mill at 600 rpm for 6 hours for crushing treatment.

[0044] 2. The crushed powder is transferred to a high-temperature resistant corundum boat with dimensions of 50*20*20 mm, leveled, and cut into blocks. Then, it is transferred to a box furnace with an air atmosphere for sintering. The temperature is raised to 900 °C at a heating rate of 12 °C / min at room temperature and held for 10 hours. Then, it is allowed to cool naturally to room temperature to obtain a cobalt-free single-crystal lithium-rich manganese-based cathode material.

[0045] Example 4 A method for preparing a cobalt-free single-crystal lithium-rich manganese-based cathode material, comprising the following steps: 1. Weigh 10 g of nickel-manganese hydroxide precursor, mix the nickel-manganese hydroxide precursor with lithium carbonate / lithium hydroxide = 5:5 at a molar ratio of 1:1.2, add 2.47 g of lithium carbonate / 3.35 g of lithium hydroxide (20% excess lithium hydroxide), mix them evenly with a mixer, then transfer them to a ball mill and ball mill at 300 rpm for 12 hours for crushing treatment; 2. Transfer the crushed powder to a high-temperature resistant corundum boat with dimensions of 50*20*20 mm, spread it out, cut it into pieces, and then transfer it to a box furnace with an air atmosphere for sintering. The material was heated to 950 °C at a heating rate of 15 °C / min at room temperature and held at that temperature for 25 h. Then it was allowed to cool naturally to room temperature to obtain a cobalt-free single-crystal lithium-rich manganese-based cathode material.

[0046] Example 5 A method for preparing a cobalt-free single-crystal lithium-rich manganese-based cathode material, comprising the following steps: 1. Weigh 10 g of nickel manganese hydroxide precursor, mix the nickel manganese hydroxide precursor and lithium carbonate at a molar ratio of 1:1.5, add 6.45 g of lithium carbonate (5% excess lithium carbonate), mix them evenly using a mixer, then transfer them to a ball mill and ball mill at 400 rpm for 10 h for crushing treatment.

[0047] 2. Transfer the crushed powder to a high-temperature resistant corundum boat with dimensions of 50*20*20 mm, spread it out, cut it into pieces, and then transfer it to a box furnace with an air atmosphere for sintering. The temperature was increased to 1100 °C at a heating rate of 10 °C / min at room temperature and held for 8 hours. Then it was allowed to cool naturally to room temperature to obtain a cobalt-free single-crystal lithium-rich manganese-based cathode material.

[0048] Example 6 A method for preparing a cobalt-free single-crystal lithium-rich manganese-based cathode material, comprising the following steps: 1. Weigh 10 g of nickel manganese hydroxide precursor, mix the nickel manganese hydroxide precursor and lithium carbonate at a molar ratio of 1:1.3, add 5.86 g of lithium carbonate (10% excess lithium carbonate), mix them evenly using a mixer, then transfer them to a ball mill and ball mill at 500 rpm for 10 hours for crushing treatment.

[0049] 2. Transfer the crushed powder to a high-temperature resistant corundum boat with dimensions of 50*20*20 mm, spread it out, cut it into pieces, and then transfer it to a box furnace with an air atmosphere for sintering. The material was heated to 700 °C at a heating rate of 2 °C / min at room temperature and held at that temperature for 30 h. Then it was allowed to cool naturally to room temperature to obtain a cobalt-free single-crystal lithium-rich manganese-based cathode material.

[0050] Example 7 A method for preparing a cobalt-free single-crystal lithium-rich manganese-based cathode material, comprising the following steps: 1. Weigh 10 g of nickel-manganese hydroxide precursor, mix the nickel-manganese hydroxide precursor with lithium hydroxide at a molar ratio of 1:1.55, add 7.57 g of lithium hydroxide (5% excess lithium hydroxide), mix them evenly using a mixer, then transfer them to a ball mill and ball mill at 400 rpm for 12 hours for crushing treatment.

[0051] 2. Transfer the crushed powder to a high-temperature resistant corundum boat with dimensions of 50*20*20 mm, spread it out, cut it into pieces, and then transfer it to a box furnace with an air atmosphere for sintering. The material was heated to 1000 °C at a heating rate of 4 °C / min at room temperature and held at that temperature for 15 h. Then it was allowed to cool naturally to room temperature to obtain a cobalt-free single-crystal lithium-rich manganese-based cathode material.

[0052] Example 8 A method for preparing a cobalt-free single-crystal lithium-rich manganese-based cathode material, comprising the following steps: 1. Weigh 10 g of nickel-manganese hydroxide precursor, mix the nickel-manganese hydroxide precursor with lithium carbonate at a molar ratio of 1:1.15, add 6.68 g of lithium hydroxide (25% excess lithium hydroxide), mix them evenly using a mixer, then transfer them to a ball mill and ball mill at 800 rpm for 6 hours for crushing treatment.

[0053] 2. Transfer the crushed powder to a high-temperature resistant corundum boat with dimensions of 50*20*20 mm, spread it out, cut it into pieces, and then transfer it to a box furnace with an air atmosphere for sintering. The material was heated to 900 °C at a heating rate of 8 °C / min at room temperature and held at that temperature for 8 hours. Then it was allowed to cool naturally to room temperature to obtain a cobalt-free single-crystal lithium-rich manganese-based cathode material.

[0054] Comparative Example 1 A method for preparing a cobalt-free polycrystalline lithium-rich manganese-based cathode material, comprising the following steps: 1. Weigh 10 g of nickel-manganese hydroxide precursor, mix the nickel-manganese hydroxide precursor and lithium hydroxide at a molar ratio of 1:1.35, add 6.28 g of lithium hydroxide, and mix them evenly using a mixer.

[0055] 2. The uniformly mixed powder is transferred to a high-temperature resistant corundum boat with dimensions of 50*20*20 mm, leveled, and cut into blocks. Then, it is transferred to a box furnace with an air atmosphere for sintering. The temperature is increased to 950 °C at a heating rate of 5 °C / min at room temperature and held for 15 hours. Then, it is allowed to cool naturally to room temperature to obtain the cobalt-free polycrystalline lithium-rich manganese-based cathode material.

[0056] Comparative Example 2 A method for preparing a cobalt-free polycrystalline lithium-rich manganese-based cathode material, comprising the following steps: 1. Weigh 10 g of nickel manganese hydroxide precursor, mix the nickel manganese hydroxide precursor and lithium carbonate at a molar ratio of 1:1.3, add 5.32 g of lithium carbonate, and mix them evenly using a mixer.

[0057] 2. The uniformly mixed powder is transferred to a high-temperature resistant corundum boat with dimensions of 50*20*20 mm, leveled, and cut into blocks. Then, it is transferred to a box furnace with an air atmosphere for sintering. The temperature is increased to 900 °C at a heating rate of 2 °C / min at room temperature and held for 18 hours. Then, it is allowed to cool naturally to room temperature to obtain the cobalt-free polycrystalline lithium-rich manganese-based cathode material.

[0058] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any changes or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention should be included within the scope of protection of the present invention.

Claims

1. A cobalt-free single-crystal lithium-rich manganese-based cathode material, characterized in that, The chemical formula is Li x Ni y Mn z O2; where 1.1≤x≤1.5, 0.2≤y≤0.5, 0.4≤z≤0.

8.

2. The cobalt-free single-crystal lithium-rich manganese-based cathode material according to claim 1, characterized in that, x=1.2, y=0.2, z=0.

6.

3. A method for preparing a cobalt-free single-crystal lithium-rich manganese-based cathode material according to any one of claims 1-2, characterized in that, include: Step 1: Mix the nickel manganese hydroxide precursor with the lithium salt and grind them evenly to obtain mixture one; Step 2: Transfer mixture one to a ball mill for high-energy ball milling to obtain mixture two; Step 3: Sinter the mixture, hold it at a certain temperature, and cool it to obtain the original cobalt-free single-crystal lithium-rich manganese-based cathode material; Step 4: Chemically modify the original cobalt-free single-crystal lithium-rich manganese-based cathode material to obtain cobalt-free single-crystal lithium-rich manganese-based cathode material.

4. The method for preparing cobalt-free single-crystal lithium-rich manganese-based cathode material according to claim 3, characterized in that, The chemical formula of the nickel-manganese hydroxide precursor mentioned in step 1 is Ni a Mn b (OH)2, where 0.2≤a≤0.45, 0.55≤b≤0.8, and a+b=1.

5. The method for preparing cobalt-free single-crystal lithium-rich manganese-based cathode material according to claim 3, characterized in that, The lithium salts mentioned in step 1 include lithium hydroxide, lithium carbonate, lithium nitrate, and / or lithium chloride.

6. The method for preparing cobalt-free single-crystal lithium-rich manganese-based cathode material according to claim 3, characterized in that, In step 1, the molar ratio of the nickel manganese hydroxide precursor to the lithium salt is 1:1.15 to 1.

55.

7. The method for preparing cobalt-free single-crystal lithium-rich manganese-based cathode material according to claim 3, characterized in that, The particle size of the nickel-manganese hydroxide precursor is 8-10 μm; the particle size of the nickel-manganese hydroxide precursor in the first mixture is 400-600 nm.

8. The method for preparing cobalt-free single-crystal lithium-rich manganese-based cathode material according to claim 3, characterized in that, The particle size of the nickel-manganese hydroxide precursor in the mixture is 400-600 nm.

9. The method for preparing cobalt-free single-crystal lithium-rich manganese-based cathode material according to claim 3, characterized in that, The sintering temperature is 700-1100°C, and the holding time is 8-30h.

10. An application of a cobalt-free single-crystal lithium-rich manganese-based cathode material according to any one of claims 1-2, characterized in that, Applications of cobalt-free single-crystal lithium-rich manganese-based cathode materials in electric vehicles, energy storage systems, low-altitude economy, and consumer electronics.

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