A lithium-rich cathode material, a preparation method thereof, and a lithium-ion battery

Abstract

The present invention provides a lithium-rich cathode material, a preparation method thereof, and a lithium-ion battery. The preparation method of the lithium-rich cathode material includes: uniformly mixing nickel-manganese hydroxide with a lithium source to obtain a mixture; sintering the mixture to obtain the lithium-rich cathode material; during the sintering process, the mixture is placed in a reaction chamber, and oxygen is continuously introduced into the reaction chamber. The sintering process includes a heating stage and a heat preservation stage that are carried out in sequence; the heating rate in the heating stage is 1 °C / min ≤ r ≤ 5 °C / min, and the sintering process satisfies 0.3 ≤ a / r ≤ 0.5 and 3 ≤ a / r*t ≤ 6, where a is the ratio of the oxygen flow rate to the volume of the reaction chamber, and t is the time of the heat preservation stage; by limiting the heating rate within a specific range and the specific relationship between the oxygen flow rate and the heat preservation time and the heating rate, the content of the Li 2 MnO 3 phase in the lithium-rich cathode material is regulated, and a lithium-rich cathode material with excellent capacity and low voltage attenuation degree is prepared, which is beneficial to improving the energy density and cycle performance of the lithium-ion battery.

Description

Technical Field

[0001] The present invention relates to the technical field of lithium - ion batteries, and particularly relates to a lithium - rich cathode material, a preparation method thereof, and a lithium - ion battery. Background Art

[0002] Lithium - ion batteries have advantages such as high voltage platform, good cycling performance, no memory effect, and high specific energy, and are currently the most widely used power batteries. With the development of smart grid energy storage and the continuous popularization of new energy vehicles, lithium - ion batteries have developed rapidly, and at the same time, the market's performance requirements for lithium - ion batteries are getting higher and higher. Currently, the actual discharge specific capacity of commercial cathode materials (such as LiCoO2, LiFePO4, and lithium nickel manganese cobalt oxide) is far lower than that of commercial anode materials (such as graphite), which limits the energy density of lithium - ion batteries; at the same time, cobalt elements are contained in existing commercial cathode materials, and the high price of cobalt increases the cost of lithium - ion batteries and causes relatively large environmental pollution.

[0003] Lithium - rich manganese - based cathode materials (LMROs) have a discharge specific capacity higher than 250 mAh / g and do not contain cobalt elements. The reserves of Mn and Ni elements are abundant and the cost is low, so they are considered to be the most potential lithium - ion battery cathode materials in recent years. The lithium - rich manganese - based cathode material can be regarded as being composed of two phases of Li 2 MnO 3 and LiNi 0.5 Mn 0.5 O 2 . Among them, the less the Li 2 MnO 3 phase, the smaller the voltage attenuation degree, that is, the more beneficial to the cycling performance of the lithium - ion battery; while the less the Li 2 MnO 3 phase, the smaller its capacity, that is, the more unfavorable to the energy density of the lithium - ion battery.

[0004] The theoretical content of the Li 2 MnO 3 phase in the lithium - rich manganese - based cathode material is mainly determined by the contents of nickel and manganese elements in nickel - manganese hydroxide. However, its actual content is affected by various parameters in the preparation process, which makes it difficult to prepare a lithium - rich cathode material with both excellent capacity and low voltage attenuation degree. Summary of the Invention

[0005] Therefore, the technical problem to be solved by the present invention is how to prepare a lithium - rich cathode material with both excellent capacity and low voltage attenuation degree, so as to provide a lithium - rich cathode material, a preparation method thereof, and a lithium - ion battery.

[0006] The present invention provides a method for preparing a lithium-rich cathode material, comprising: uniformly mixing nickel-manganese hydroxide with a lithium source to obtain a mixture; sintering the mixture to obtain the lithium-rich cathode material; during the sintering process, the mixture is placed in a reaction chamber, and oxygen is continuously introduced into the reaction chamber, and the sintering process includes a heating stage and a heat preservation stage that are sequentially carried out; the heating rate of the heating stage is 1 °C / min ≤ r ≤ 5 °C / min, and the sintering process satisfies 0.3 ≤ a / r ≤ 0.5 and 3 ≤ a / r*t ≤ 6, where a is the ratio of the flow rate of oxygen to the volume of the reaction chamber, the unit of the flow rate of oxygen is L / h, the unit of the volume of the reaction chamber is L, and t is the time of the heat preservation stage, and the unit of t is h.

[0007] Optionally, 0.3 ≤ a ≤ 2 and 8 h ≤ t ≤ 15 h.

[0008] Optionally, the molar ratio of the lithium element in the lithium source to the total molar amount of the nickel element and the manganese element in the nickel-manganese hydroxide is 1.1 - 1.5.

[0009] Optionally, the nickel-manganese hydroxide is Ni y Mn 1-y (OH) 2 , 0.25 ≤ y ≤ 0.45.

[0010] Optionally, the specific surface area of the nickel-manganese hydroxide is 17 m 2 / g - 27 m 2 / g, and the tap density of the nickel-manganese hydroxide is 1.4 g / cm 3 -1.6 g / cm 3 .

[0011] Optionally, the lithium source includes at least one of Li 2 CO 3 and LiOH.

[0012] Optionally, the sintering process further includes a cooling stage, and the cooling stage is carried out after the heat preservation stage; after the lithium-rich cathode material is cooled to room temperature, the lithium-rich cathode material is sequentially crushed and sieved to remove impurities.

[0013] Optionally, the mesh number of the sieve used for sieving is 325 mesh - 400 mesh.

[0014] Optionally, the temperature of the heat preservation stage is 800 °C - 1000 °C.

[0015] The present invention also provides a lithium-rich cathode material, which is prepared by using the above method for preparing a lithium-rich cathode material, and the lithium-rich cathode material is xLi 2 MnO 3·(1 - x)LiNi 0.5 Mn 0.5 O 2 , where x is 0.1 - 0.5.

[0016] Optionally, the specific surface area of the lithium-rich cathode material is 1.0 m 2 / g - 10 m 2 / g, and the tap density of the lithium-rich cathode material is 1.0 g / cm 3 - 2.1 g / cm 3 .

[0017] The present invention also provides a lithium-ion battery, including the above-mentioned lithium-rich cathode material.

[0018] The technical solution of the present invention has the following advantages:

[0019] 1. The preparation method of the lithium-rich cathode material provided by the present invention, by limiting the heating rate within a specific range during the sintering process, and limiting the specific relationship between the oxygen flow rate, the holding time and the heating rate, to regulate the content of the Li 2 MnO 3 phase, so as to reduce the degree of voltage decay while ensuring the capacity of the lithium-rich cathode material, that is, a lithium-rich cathode material with both excellent capacity and low voltage decay degree is prepared, which is beneficial to the energy density and cycle performance of the lithium-ion battery.

[0020] 2. The lithium-ion battery provided by the present invention, using the lithium-rich cathode material with excellent capacity and low voltage decay degree, ensures the energy density of the lithium-ion battery and improves the cycle performance of the lithium-ion battery. Specific Embodiments

[0021] The technical solution of the present invention will be described clearly and completely below. Obviously, the described embodiments are part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without making creative efforts belong to the scope of protection of the present invention. For those embodiments where specific experimental steps or conditions are not indicated, the operations or conditions of the conventional experimental steps described in the literature in this field can be carried out. For the reagents or instruments whose manufacturers are not indicated, they are all conventional reagent products that can be obtained through commercial purchase.

[0022] This embodiment provides a method for preparing a lithium-rich cathode material, including: uniformly mixing nickel manganese hydroxide with a lithium source to obtain a mixture; sintering the mixture to obtain the lithium-rich cathode material; during the sintering process, the mixture is placed in a reaction chamber, and oxygen is continuously introduced into the reaction chamber. The sintering process includes a heating stage and a heat preservation stage that are carried out in sequence; the heating rate in the heating stage is 1°C / min ≤ r ≤ 5°C / min, and the sintering process satisfies 0.3 ≤ a / r ≤ 0.5 and 3 ≤ a / r*t ≤ 6, where a is the ratio of the flow rate of oxygen to the volume of the reaction chamber, the unit of the flow rate of oxygen is L / h, the unit of the volume of the reaction chamber is L, t is the time of the heat preservation stage, and the unit of t is h.

[0023] In the above method for preparing a lithium-rich cathode material, by limiting the heating rate within a specific range during the sintering process, and limiting the specific relationship between the oxygen flow rate, the heat preservation time and the heating rate, the content of Li 2 MnO 3 phase in the lithium-rich cathode material is regulated, so that while ensuring the capacity of the lithium-rich cathode material, the degree of voltage decay is reduced, that is, a lithium-rich cathode material with both excellent capacity and low voltage decay degree is prepared, which is beneficial to the energy density and cycle performance of lithium-ion batteries. In addition, by introducing oxygen into the reaction chamber during the sintering process, the reaction can be promoted, the reaction degree is increased, and the amount of unreacted lithium source is reduced.

[0024] Exemplarily, the heating rate in the heating stage can be 1°C / min, 1.5°C / min, 2°C / min, 2.5°C / min, 3°C / min, 3.5°C / min, 4°C / min, 4.5°C / min, 5°C / min and any value between the above values; the value of a / r can be 0.3, 0.35, 0.4, 0.45, 0.5 and any value between the above values; the value of a / r*t can be 3, 3.5, 4, 4.5, 5, 5.5, 6 and any value between the above values.

[0025] As a preferred embodiment, 0.3 ≤ a ≤ 2 and 8h ≤ t ≤ 15h; exemplarily, the ratio of the flow rate of oxygen to the volume of the reaction chamber can be 0.3, 0.5, 0.75, 1, 1.25, 1.5, 1.75, 2 and any ratio between the above values; the time of the heat preservation stage can be 8h, 8.5h, 9h, 9.5h, 10h, 10.5h, 11h, 11.5h, 12h, 12.5h, 13h, 13.5h, 14h, 14.5h, 15h and any value between the above values.

[0026] In this embodiment, the ratio of the molar amount of lithium element in the lithium source to the total molar amount of nickel element and manganese element in the nickel manganese hydroxide is 1.1 - 15, and the nickel manganese hydroxide is Ni y Mn 1-y (OH) 2 , where 0.25 ≤ y ≤ 0.45; Exemplarily, the ratio of the molar amount of lithium element in the lithium source to the total molar amount of nickel element and manganese element in the nickel manganese hydroxide can be 1.15, 1.20, 1.25, 1.35, 1.4, 1.5, and any value between the above values, and the content y of Ni in the nickel manganese hydroxide can be 0.25, 0.3, 0.35, 0.4, 0.45, and any value between the above values. Both the ratio of the molar amount of lithium element in the lithium source to the total molar amount of nickel element and manganese element in the nickel manganese hydroxide and the content y of Ni in the nickel manganese hydroxide will affect the content of Li 2 MnO 3 phase in the lithium-rich cathode material, thereby affecting the capacity and voltage decay degree of the lithium-rich cathode material.

[0027] Further, the lithium source includes at least one of Li 2 CO 3 and LiOH; the specific surface area of the nickel manganese hydroxide is 17 m 2 / g - 27 m 2 / g, and the tap density of the nickel manganese hydroxide is 1.4 g / cm 3 -1.6 g / cm 3 ; Exemplarily, the specific surface area of the nickel manganese hydroxide can be 17 m 2 / g, 18 m 2 / g, 19 m 2 / g, 20 m 2 / g, 21 m 2 / g, 22 m 2 / g, 23 m 2 / g, 24 m 2 / g, 25 m 2 / g, 26 m 2 / g, 27 m 2 / g, and any value between the above values, and the tap density of the nickel manganese hydroxide can be 1.4 g / cm 3 , 1.45 g / cm 3 , 1.5 g / cm 3 , 1.55 g / cm 3 , 1.6 g / cm 3 , and any value between the above values.

[0028] In this embodiment, after weighing the nickel-manganese hydroxide and the lithium source, the nickel-manganese hydroxide and the lithium source are placed in a mixer for mixing. Among them, the rotation speed of the mixer is 700 rpm - 1000 rpm, the mixing time is 10 min - 20 min, and the material filling efficiency in the mixer is 50% - 80%; Exemplarily, the rotation speed of the mixer can be 700 rpm, 750 rpm, 800 rpm, 850 rpm, 900 rpm, 950 rpm or 1000 rpm, the mixing time can be 10 min, 12 min, 14 min, 16 min, 18 min or 20 min, and the material filling efficiency in the mixer can be 50%, 55%, 60%, 65%, 70%, 75% or 80%.

[0029] In this embodiment, the temperature in the heat preservation stage is 800°C - 1000°C; Exemplarily, the temperature in the heat preservation stage can be 800°C, 825°C, 850°C, 875°C, 900°C, 925°C, 950°C, 975°C, 1000°C and any value between the above values.

[0030] In this embodiment, the sintering process further includes a cooling stage, and the cooling stage is carried out after the heat preservation stage; After the lithium-rich cathode material is cooled to room temperature, the lithium-rich cathode material is successively crushed and sieved to remove impurities. Specifically, the mesh number of the sieve used for sieving is 325 mesh - 400 mesh.

[0031] The lithium-rich cathode material prepared in this embodiment is xLi 2 MnO 3 ·(1 - x)LiNi 0.5 Mn 0.5 O 2 , where x is 0.1 - 0.5, the specific surface area of the lithium-rich cathode material is 1.0 m 2 / g - 10 m 2 / g, the tap density of the lithium-rich cathode material is 1.0 g / cm 3 - 2.1 g / cm 3 , and the lithium-rich cathode material is single crystal and / or polycrystal.

[0032] Exemplarily, the content x of the Li 2 MnO 3 phase in the lithium-rich cathode material can be 0.1, 0.15, 0.2, 0.25, 0.3, 0.35, 0.4, 0.45, 0.5 and any value between the above values, and the specific surface area of the lithium-rich cathode material can be 1.0 m 2 / g, 2.0 m 2 / g, 3.0 m 2 / g, 4.0 m2 / g, 5.0 m 2 / g, 6.0 m 2 / g, 7.0 m 2 / g, 8.0 m 2 / g, 9.0 m 2 / g, 10 m 2 / g and any value between the above values, the tap density of the lithium-rich cathode material can be 1.0 g / cm 3 , 1.2 g / cm 3 , 1.4 g / cm 3 , 1.6 g / cm 3 , 1.8 g / cm 3 , 2 g / cm 3 , 2.1 g / cm 3 and any value between the above values.

[0033] This embodiment also provides a lithium-ion battery, including a lithium-rich cathode material prepared by using the preparation method of the lithium-rich cathode material provided in this embodiment.

[0034] Example 1

[0035] This embodiment provides a preparation method of a lithium-rich cathode material, including the following steps:

[0036] Weigh nickel-manganese hydroxide and Li 2 CO 3 , the nickel-manganese hydroxide is Ni 0.25 Mn 0.75 (OH) 2 , the specific surface area of the nickel-manganese hydroxide is 17 m 2 / g to 27 m 2 / g, the tap density of the nickel-manganese hydroxide is 1.4 g / cm 3 to 1.6 g / cm 3 , the molar amount of lithium element in Li 2 CO 3 and the total molar amount of nickel element and manganese element in the nickel-manganese hydroxide is 1.5;

[0037] Put the nickel-manganese hydroxide and Li 2 CO 3 into a mixer and mix evenly to obtain a mixture. The rotation speed of the mixer is 850 rpm, the mixing time is 15 min, and the material filling efficiency in the mixer is 65%;

[0038] Place the mixture in a kiln with an internal volume of 20 L. Continuously introduce oxygen into the kiln at a flow rate of 20 L / h, and heat the kiln with a heating rate r of 2 °C / min; until the temperature in the kiln reaches 900 °C, hold for a time t of 10 h; then cool naturally; that is, a = 1, a / r = 0.5, a / r*t = 5;

[0039] Sieve the product in the kiln through a 400-mesh sieve to obtain the lithium-rich cathode material.

[0040] The lithium-rich cathode material prepared in this example is 0.5Li 2 MnO 3 ·0.5LiNi 0.5 Mn 0.5 O 2 , the content of residual Li 2 CO 3 in the lithium-rich cathode material is 0.3 wt%, the specific surface area of the lithium-rich cathode material is 1.5 m 2 / g, and the tap density is 1.4 g / cm 3 .

[0041] Example 2

[0042] This example provides a method for preparing a lithium-rich cathode material, including the following steps:

[0043] Weigh nickel-manganese hydroxide and LiOH. The nickel-manganese hydroxide is Ni 0.35 Mn 0.65 (OH) 2 , the specific surface area of the nickel-manganese hydroxide is 17 m 2 / g to 27 m 2 / g, the tap density of the nickel-manganese hydroxide is 1.4 g / cm 3 to 1.6 g / cm 3 , and the ratio of the molar amount of lithium element in LiOH to the total molar amount of nickel element and manganese element in the nickel-manganese hydroxide is 1.3;

[0044] Place the nickel-manganese hydroxide and LiOH in a mixer and mix evenly to obtain a mixture. The rotation speed of the mixer is 1000 rpm, the mixing time is 10 min, and the material filling efficiency in the mixer is 80%;

[0045] Place the mixture in a kiln with an internal volume of 20 L. Continuously introduce oxygen into the kiln at a flow rate of 6 L / h, and heat the kiln with a heating rate r of 1 °C / min; until the temperature in the kiln reaches 800 °C, hold for a time t of 15 h; then cool naturally; that is, a = 0.3, a / r = 0.3, a / r*t = 5;

[0046] The product in the kiln was sieved through a 400-mesh sieve to obtain a lithium-rich cathode material.

[0047] The lithium-rich cathode material prepared in this example is 0.3Li 2 MnO 3 ·0.7LiNi 0.5 Mn 0.5 O 2 , the content of residual LiOH in the lithium-rich cathode material is 0.2 wt%, the specific surface area of the lithium-rich cathode material is 2 m 2 / g, and the tap density is 1.6 g / cm 3 .

[0048] Example 3

[0049] This example provides a preparation method of a lithium-rich cathode material, including the following steps:

[0050] Weigh nickel-manganese hydroxide and Li 2 CO 3 , the nickel-manganese hydroxide is Ni 0.45 Mn 0.55 (OH) 2 , the specific surface area of the nickel-manganese hydroxide is 17 m 2 / g to 27 m 2 / g, the tap density of the nickel-manganese hydroxide is 1.4 g / cm 3 to 1.6 g / cm 3 , the molar ratio of lithium element in Li 2 CO 3 to the total molar amount of nickel element and manganese element in the nickel-manganese hydroxide is 1.1;

[0051] Put the nickel-manganese hydroxide and Li 2 CO 3 into a mixer and mix evenly to obtain a mixture. The rotation speed of the mixer is 700 rpm, the mixing time is 20 min, and the material filling efficiency in the mixer is 50%;

[0052] Put the mixture into a kiln. The volume of the kiln is 20 L. Continuously introduce oxygen into the kiln at a flow rate of 40 L / h, and heat up the kiln. The heating rate r is 5 °C / min; until the temperature in the kiln reaches 1000 °C, the holding time t is 8 h; then cool down naturally; that is, a = 2, a / r = 0.4, a / r*t = 3.2;

[0053] Sieve the product in the kiln through a 350-mesh sieve to obtain a lithium-rich cathode material.

[0054] The lithium-rich cathode material prepared in this example is 0.1Li 2 MnO 3· 0.9LiNi 0.5 Mn 0.5 O 2 , the content of residual Li 2 CO 3 in the lithium-rich cathode material is 0.1 wt%, the specific surface area of the lithium-rich cathode material is 1.1 m 2 / g, and the tap density is 1.9 g / cm 3 .

[0055] Comparative Example 1

[0056] This comparative example provides a preparation method of a lithium-rich cathode material, which is different from the preparation method of the lithium-rich cathode material provided in Example 1 in that: during the sintering process, the oxygen flow rate is 6 L / h, the heating rate r is 4 °C / min, and the holding time t is 15 h; that is, a = 0.3, a / r = 0.075, a / r*t = 1.125.

[0057] Comparative Example 2

[0058] This comparative example provides a preparation method of a lithium-rich cathode material, which is different from the preparation method of the lithium-rich cathode material provided in Example 2 in that: during the sintering process, the oxygen flow rate is 20 L / h, the heating rate r is 4 °C / min, and the holding time t is 10 h; that is, a = 1, a / r = 0.25, a / r*t = 2.5.

[0059] Comparative Example 3

[0060] This comparative example provides a preparation method of a lithium-rich cathode material, which is different from the preparation method of the lithium-rich cathode material provided in Example 3 in that: during the sintering process, the oxygen flow rate is 6 L / h, the heating rate r is 2 °C / min, and the holding time t is 8 h; that is, a = 0.3, a / r = 0.15, a / r*t = 1.2.

[0061] Test Example 1

[0062] The lithium-rich cathode materials prepared in Examples 1-3 and Comparative Examples 1-3 are mixed and homogenized with conductive carbon black and polyvinylidene fluoride (PVDF) colloidal solution in a mass ratio of 92:4:4 to obtain a positive electrode slurry. The solid content of the polyvinylidene fluoride colloidal solution is 6.25%, and the solvent of the polyvinylidene fluoride colloidal solution is N-methylpyrrolidone (NMP); after the positive electrode slurry is coated on the surface of the aluminum foil, drying and rolling are carried out in sequence to obtain a positive electrode sheet; using a lithium sheet as the negative electrode and a carbonate ethylene ester-based electrolyte, an R2032 button battery is assembled.

[0063] The assembled lithium-ion battery was subjected to charge and discharge tests at 25 °C and 0.1C to obtain the specific capacity of the positive electrode material; then, a cycle performance test was carried out at 1C to obtain the voltage attenuation degree after 50 cycles. The test results are shown in Table 1.

[0064] Table 1

[0065] Capacity (mAh / g) Degree of voltage attenuation (%) Example 1 253.2 3.4 Example 2 235.2 2.9 Example 3 210.2 2.2 Comparative Example 1 244.7 5.3 Comparative Example 2 228.3 4.2 Comparative Example 3 203.2 3.4

[0066] As can be seen from Table 1, different heating rates, oxygen flow rates, and heat preservation times can obtain lithium-rich cathode materials with different compositions; by limiting the heating rate, oxygen flow rate, and heat preservation time within a specific numerical range, a lithium-rich cathode material with both excellent capacity and low voltage attenuation degree can be obtained.

[0067] Obviously, the above embodiments are merely examples given for clear illustration and are not limitations on the implementation manners. For those of ordinary skill in the art, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to enumerate all the implementation manners here. The obvious changes or modifications derived therefrom still fall within the protection scope of the present invention.

Claims

1. A preparation method of a lithium-rich cathode material, characterized in that, it includes: uniformly mixing nickel-manganese hydroxide with a lithium source to obtain a mixture; sintering the mixture to obtain the lithium-rich cathode material; during the sintering process, the mixture is placed in a reaction chamber, and oxygen is continuously introduced into the reaction chamber. The sintering process includes a heating stage and a heat preservation stage that are carried out in sequence; the heating rate of the heating stage is 1°C / min ≤ r ≤ 5°C / min, and the sintering process satisfies 0.3 ≤ a / r ≤ 0.5 and 3 ≤ a / r*t ≤ 6, where a is the ratio of the flow rate of oxygen to the volume of the reaction chamber, the unit of the flow rate of oxygen is L / h, the unit of the volume of the reaction chamber is L, t is the time of the heat preservation stage, and the unit of t is h.

2. The preparation method of the lithium-rich cathode material according to claim 1, characterized in that, 0.3 ≤ a ≤ 2 and 8h ≤ t ≤ 15h.

3. The preparation method of the lithium-rich cathode material according to claim 1, characterized in that, the molar amount of lithium element in the lithium source is 1.1 - 1.5 times the total molar amount of nickel element and manganese element in the nickel-manganese hydroxide.

4. The preparation method of the lithium-rich cathode material according to any one of claims 1 to 3, characterized in that, The nickel manganese hydroxide is Ni y Mn 1-y (OH) 2 , where 0.25 ≤ y ≤ 0.

45.

5. The preparation method of the lithium-rich cathode material according to claim 4, characterized in that, The specific surface area of the nickel manganese hydroxide is 17 m 2 / g - 27 m 2 / g, and the tap density of the nickel manganese hydroxide is 1.4 g / cm 3 - 1.6 g / cm 3 .

6. The preparation method of the lithium-rich cathode material according to any one of claims 1 to 3, characterized in that, The lithium source includes Li 2 CO 3 and at least one of LiOH.

7. The preparation method of the lithium-rich cathode material according to claim 1, characterized in that, the sintering process further includes a cooling stage, and the cooling stage is carried out after the heat preservation stage; after the lithium-rich cathode material is cooled to room temperature, the lithium-rich cathode material is broken and sieved in sequence to remove impurities.

8. The preparation method of the lithium-rich cathode material according to claim 7, characterized in that, the mesh number of the sieve used for sieving is 325 mesh - 400 mesh.

9. The preparation method of the lithium-rich cathode material according to claim 1, characterized in that, the temperature of the heat preservation stage is 800°C - 1000°C.

10. A lithium-rich cathode material, characterized in that, Prepared by the preparation method of the lithium-rich cathode material according to any one of claims 1 to 9, the lithium-rich cathode material is xLi 2 MnO 3 ·(1-x)LiNi 0.5 Mn 0.5 O 2 , where x is 0.1-0.

5.

11. The lithium-rich cathode material according to claim 10, characterized in that, The specific surface area of the lithium-rich cathode material is 1.0 m 2 / g - 10 m 2 / g, and the tap density of the lithium-rich cathode material is 1.0 g / cm 3 - 2.1 g / cm 3 .

12. A lithium-ion battery, characterized in that, it includes the lithium-rich cathode material according to claim 10 or 11.