Low-residual-alkali lithium-rich manganese-based positive electrode material as well as preparation method and application thereof

Abstract

The invention relates to the technical field of lithium ion batteries, in particular to a low-residual-alkali lithium-rich manganese-based positive electrode material and a preparation method and application thereof. The preparation method of the low-residual alkali lithium-rich manganese-based positive electrode material comprises the following steps: uniformly mixing a lithium-rich manganese-based precursor with a lithium source to obtain mixed powder; carrying out three-stage sintering treatment on the mixed powder; wherein the temperature of the first-stage sintering treatment is 350-550 DEG C, the temperature of the second-stage sintering treatment is 650-700 DEG C, and the temperature of the third-stage sintering treatment is 850-950 DEG C. By gradually sintering and accurately controlling the sintering temperature, the residual alkaline impurities are fully decomposed or volatilized at high temperature, the internal stress and potential structural damage of the material can be reduced, and the crystal integrity and phase stability of the material can be maintained, so that the generation and accumulation of the alkaline impurities are effectively reduced, and the service life of the material is prolonged. And degradation of specific discharge capacity, rate capability and cycle performance and potential safety hazards caused by residual alkali are reduced.

Description

Technical Field

[0001] The present invention relates to the technical field of lithium ion batteries, and in particular to a low-residual-alkali lithium-rich manganese-based positive electrode material and a preparation method and application thereof. Background Art

[0002] With the rapid development of the new energy industry, the technical requirements for lithium-ion battery cathode materials are also constantly increasing. In recent years, lithium-rich manganese-based cathode materials (referred to as lithium-rich materials) have attracted much attention due to their high specific capacity (>250mAh / g) and low cost, and are considered to be strong competitors for the next generation of lithium-ion battery cathode materials. However, due to the reaction of H2O adsorbed on the surface of the material with CO2 in the air to generate H2CO3, the pH value of the water on the surface of the material drops to about 5.5. This weakly acidic CO3 2 -It is easy to capture Li+ from the surface lattice of the material to generate Li2CO3 and LiOH, causing the lithium-rich manganese-based material to exhibit excessive alkalinity.

[0003] The residual alkali in lithium-rich manganese-based materials will bring a series of negative effects and hazards. For example, the residual alkali will react adversely with the electrolyte, resulting in the decomposition or consumption of the electrolyte, which in turn affects the overall electrochemical reaction efficiency of the battery and causes the capacity to gradually decrease; the residual alkali causes the formation of a byproduct film on the electrode surface, which increases the charge transfer impedance, thereby reducing the cycle life and stability of the material; it reacts with the active components such as lithium, nickel, and manganese on the surface of the material, resulting in lattice distortion or destruction, thereby affecting the structural stability of the material; it reacts with the electrolyte during the battery charging and discharging process to produce gas (such as CO2 or H2), resulting in an increase in the internal pressure of the battery, increasing the risk of battery bulging, leakage, and even explosion. That is, the residual alkali in lithium-rich manganese-based materials not only directly affects the performance and life of the battery, but may also bring serious safety risks. Therefore, these residual alkalis must be eliminated as much as possible during the material preparation and processing process.

[0004] At present, the existing technology mostly uses water washing to reduce the residual alkali in lithium-rich manganese-based positive electrode materials. Although it is a common and economical method, it also has some shortcomings and challenges: a) Incomplete removal: The water washing method may not be able to completely remove all residual alkaline impurities, especially impurities inside or deep in the material. This will cause some alkaline substances to remain, which may still affect the electrochemical properties of the material. b) Material structural damage: During the water washing process, water may penetrate into the micropores or lattices of the material, causing the dissolution or structural damage of the material, especially for those phases that are unstable in water. This structural damage will reduce the cycle stability and capacity retention rate of the material. c) Secondary pollution risk: During the water washing process, if the water source or the cleaning environment is not pure enough, new impurities or pollutants may be introduced, which will reduce the purity of the material and affect the final electrochemical performance. d) New phase generation: During the water washing process, certain chemical reactions may occur, resulting in the formation of undesirable new phases, such as hydroxide or carbonate precipitation. The presence of these by-products will further reduce the performance of the material and increase the complexity of subsequent processing. e) Operational complexity: Although the water washing method seems simple, in order to ensure the effect, it may be necessary to strictly control the conditions of water washing (such as temperature, time, purity of pure water, etc.), which increases the complexity of the process. In addition, the drying and processing process of the washed material also requires special attention to prevent the degradation of discharge capacity, rate performance and cycle performance. f) Environmental and cost issues: The water washing method consumes a large amount of pure water, and the treatment of wastewater after washing also needs to consider environmental protection requirements, which may bring certain environmental and economic costs. Summary of the invention

[0005] Therefore, the technical problem to be solved by the present invention is to overcome the defects of the existing water washing method for treating residual alkali in lithium-rich manganese-based positive electrode materials, such as the problem of wastewater treatment and poor effect, which leads to the deterioration of the discharge specific capacity, rate performance and cycle performance of the lithium-rich manganese-based positive electrode materials, thereby providing a low-residual-alkali lithium-rich manganese-based positive electrode material and its preparation method and application to solve the above problems.

[0006] In order to achieve the above object, the present invention provides the following technical solutions:

[0007] A method for preparing a low-residual-alkali lithium-rich manganese-based positive electrode material, comprising:

[0008] Mixing the lithium-rich manganese-based precursor with the lithium source to obtain a mixed powder;

[0009] The mixed powder is subjected to a three-stage sintering treatment; wherein the temperature of the first stage sintering treatment is 350-550°C, the temperature of the second stage sintering treatment is 650-700°C, and the temperature of the third stage sintering treatment is 850-950°C.

[0010] Preferably, the lithium source is at least one of lithium carbonate, lithium hydroxide and lithium acetate.

[0011] Preferably, the chemical formula of the lithium-rich manganese-based precursor is Ni x Mn 1-x (OH)2, 0<x<0.5.

[0012] Preferably, the molar ratio of the metal element in the lithium-rich manganese-based precursor to the lithium element in the lithium source is 1:(1.35-1.55).

[0013] Preferably, the atmosphere of the three-stage sintering treatment is an oxygen-containing atmosphere and / or an inert atmosphere.

[0014] Preferably, the holding time of the first stage sintering treatment is 4-6 hours;

[0015] And / or, the heat preservation time of the second stage sintering treatment is 4-6h;

[0016] And / or, the heat preservation time of the third sintering treatment is 8-12 hours.

[0017] Preferably, the heating rate of the three-stage sintering process is 2-5°C / min;

[0018] And / or, the three-stage sintering treatment is followed by cooling at a rate of 1-2°C / min.

[0019] Preferably, the cooling is followed by a crushing and screening process.

[0020] The present invention also provides a low residual alkali lithium-rich manganese-based positive electrode material, which is prepared by the above-mentioned method for preparing the low residual alkali lithium-rich manganese-based positive electrode material.

[0021] The present invention also provides the use of the low-residual-alkali lithium-rich manganese-based positive electrode material in a lithium-ion battery.

[0022] In the present invention, the oxygen-containing atmosphere is air or oxygen, and the inert atmosphere is nitrogen or argon.

[0023] The technical solution of the present invention has the following advantages:

[0024] 1. A method for preparing a low-residual-alkali lithium-rich manganese-based positive electrode material, comprising: mixing a lithium-rich manganese-based precursor with a lithium source to obtain a mixed powder; performing a three-stage sintering treatment on the mixed powder; wherein the temperature of the first stage sintering treatment is 350-550°C, the temperature of the second stage sintering treatment is 650-700°C, and the temperature of the third stage sintering treatment is 850-950°C. The present invention gradually sinters and precisely controls the sintering temperature, so that the residual alkaline impurities are fully decomposed or volatilized at high temperatures, while reducing the internal stress and potential structural damage of the material, helping to maintain the crystal integrity and phase stability of the material, thereby effectively reducing the generation and accumulation of alkaline impurities, and reducing the discharge specific capacity, rate performance and cycle performance degradation and safety hazards caused by residual alkali. In addition, the present invention does not involve liquid media, so there are no new impurities or pollutants that may be introduced during the water washing process, and there is no need to consider wastewater treatment issues.

[0025] The specific mechanism is: in the initial stage of sintering, the temperature of 350-550℃ is used for pre-sintering to promote the full reaction of the unreacted precursors in the material, thereby reducing the formation of by-products such as Li2CO3 and LiOH. Subsequently, the high-temperature stage further promotes the formation and stabilization of the material lattice, and at the same time helps to eliminate impurities such as Li2CO3 and LiOH that are easily decomposed in the material. Step sintering at the high-temperature stage (first heating to 650-700℃, then heating to 850-950℃) helps to reduce the internal stress of the material caused by rapid heating, thereby reducing the residual alkaline substances on the surface of the material.

[0026] 2. In the preparation method of the low residual alkali lithium-rich manganese-based positive electrode material of the present invention, after sintering, the cooling rate is controlled to perform slow cooling to avoid cracks or other defects in the material due to rapid cooling, reduce the contact area between the material and the air, and further reduce the alkaline substances generated by the reaction of moisture and CO2 in the air with the material. In addition, after cooling, the product can be stored in an inert atmosphere to inhibit the generation of residual alkali during storage.

[0027] 3. In the preparation method of the low residual alkali lithium-rich manganese-based positive electrode material of the present invention, the formation of LiOH and Li2CO3 is reduced by creating an oxygen-containing atmosphere (compressed air is introduced to remove carbon dioxide and moisture) or an inert atmosphere. DETAILED DESCRIPTION

[0028] The following examples are provided for a better understanding of the present invention, but are not intended to limit the best mode of implementation, nor to limit the content and protection scope of the present invention. Any product identical or similar to the present invention obtained by anyone under the inspiration of the present invention or by combining the features of the present invention with other prior arts shall fall within the protection scope of the present invention.

[0029] If no specific experimental steps or conditions are specified in the examples, the conventional experimental steps or conditions described in the literature in the field can be used. If no manufacturer is specified for the reagents or instruments used, they are all conventional reagent products that can be obtained commercially.

[0030] Example 1

[0031] This embodiment provides a method for preparing a low-residual-lithium-rich lithium-manganese-based positive electrode material, and the specific steps are as follows:

[0032] 1) According to the molar ratio of the metal element in the lithium-rich manganese-based precursor to the lithium element in the lithium source of 1:1.5, weigh Ni 0.35 Mn 0.65 (OH)2 and lithium carbonate, among which Ni 0.35 Mn 0.65 The specific surface area of ​​the (OH)2 precursor is 41 m 2 / g, tap density is 1.82g / cm 3 , the median particle size D50 is 5.7 μm, the above raw materials are mixed evenly with a high-speed mixer to obtain a mixed powder;

[0033] 2) The mixed powder in step 1) is placed in a box furnace, the sintering atmosphere is compressed air, the air flow rate is 10L / min, the temperature is first increased to 500°C at a heating rate of 2°C / min and sintered for 4h, then the temperature is increased to 700°C at a heating rate of 2°C / min and high-temperature calcined for 5h, and then the temperature is increased to 900°C at a heating rate of 2°C / min and high-temperature calcined for 10h, and finally cooled to room temperature at a cooling rate of 1°C / min (the cooling rate is slowed down by intermittent heating, the same below), and a low residual alkali lithium-rich manganese-based positive electrode material is obtained after crushing, and the prepared positive electrode material is placed in an inert atmosphere for storage and standby.

[0034] Example 2

[0035] This embodiment provides a method for preparing a low-residual-lithium-rich lithium-manganese-based positive electrode material, and the specific steps are as follows:

[0036] 1) According to the molar ratio of the metal element in the lithium-rich manganese-based precursor to the lithium element in the lithium source of 1:1.55, weigh Ni 0.4 Mn 0.6 (OH)2 and lithium hydroxide, of which Ni 0.4 Mn 0.6 The specific surface area of ​​the (OH)2 precursor is 40 m 2 / g, tap density is 1.79g / cm 3 , the median particle size D50 is 5.4 μm, the above raw materials are mixed evenly with a high-speed mixer to obtain a mixed powder;

[0037] 2) placing the mixed powder in step 1) in a box furnace, the sintering atmosphere is compressed air, the air flow rate is 10L / min, first heating to 350°C at a heating rate of 5°C / min and sintering for 6h, then heating to 650°C at a heating rate of 5°C / min and calcining at high temperature for 6h, then heating to 950°C at a heating rate of 5°C / min and calcining at high temperature for 8h, finally cooling to room temperature at a cooling rate of 2°C / min, and obtaining a low residual alkali lithium-rich manganese-based positive electrode material after crushing, and storing the obtained positive electrode material in an inert atmosphere for standby use.

[0038] Example 3

[0039] This embodiment provides a method for preparing a low-residual-lithium-rich lithium-manganese-based positive electrode material, and the specific steps are as follows:

[0040] 1) According to the molar ratio of the metal element in the lithium-rich manganese-based precursor to the lithium element in the lithium source of 1:1.35, weigh Ni 0.1 Mn 0.9 (OH)2 and lithium acetate, of which Ni 0.1 Mn 0.9 The specific surface area of ​​the (OH)2 precursor is 42 m 2 / g, tap density is 1.80g / cm 3 , the median particle size D50 is 5.6 μm, the above raw materials are mixed evenly with a high-speed mixer to obtain a mixed powder;

[0041] 2) placing the mixed powder in step 1) in a box furnace, the sintering atmosphere is compressed air, the air flow rate is 10L / min, first heating to 550°C at a heating rate of 2°C / min and sintering for 4h, then heating to 700°C at a heating rate of 2°C / min and calcining at high temperature for 4h, then heating to 850°C at a heating rate of 2°C / min and calcining at high temperature for 12h, finally cooling to room temperature at a cooling rate of 1°C / min, and obtaining a low residual alkali lithium-rich manganese-based positive electrode material after crushing, and storing the obtained positive electrode material in an inert atmosphere for standby use.

[0042] Example 4

[0043] This embodiment provides a method for preparing a low-residual-lithium-rich lithium-manganese-based positive electrode material, and the specific steps are as follows:

[0044] 1) According to the molar ratio of the metal element in the lithium-rich manganese-based precursor to the lithium element in the lithium source of 1:1.5, weigh Ni 0.35 Mn 0.65 (OH)2 and lithium carbonate, among which Ni 0.35 Mn 0.65 The specific surface area of ​​the (OH)2 precursor is 41 m 2 / g, tap density is 1.82g / cm 3, the median particle size D50 is 5.7 μm, the above raw materials are mixed evenly with a high-speed mixer to obtain a mixed powder;

[0045] 2) placing the mixed powder in step 1) in a box furnace, the sintering atmosphere is nitrogen, the nitrogen flow rate is 10L / min, first heating to 500°C at a heating rate of 2°C / min and sintering for 4h, then heating to 700°C at a heating rate of 2°C / min and calcining at high temperature for 5h, then heating to 900°C at a heating rate of 2°C / min and calcining at high temperature for 10h, finally cooling naturally to room temperature with the furnace, crushing to obtain a low residual alkali lithium-rich manganese-based positive electrode material, and placing the obtained positive electrode material in an inert atmosphere for storage for standby use.

[0046] Comparative Example 1

[0047] This comparative example provides a method for preparing a low-residual-lithium-rich lithium-manganese-based positive electrode material, and the specific steps are as follows:

[0048] 1) According to the molar ratio of the metal element in the lithium-rich manganese-based precursor to the lithium element in the lithium source of 1:1.5, weigh Ni 0.35 Mn 0.65 (OH)2 and lithium carbonate, among which Ni 0.35 Mn 0.65 The specific surface area of ​​the (OH)2 precursor is 41 m 2 / g, tap density is 1.82g / cm 3 , the median particle size D50 is 5.7 μm, the above raw materials are mixed evenly with a high-speed mixer to obtain a mixed powder;

[0049] 2) placing the mixed powder in step 1) in a box furnace, the sintering atmosphere is compressed air, the air flow rate is 10L / min, first heating to 700°C at a heating rate of 2°C / min and calcining at high temperature for 5h, then heating to 900°C at a heating rate of 2°C / min and calcining at high temperature for 10h, and finally cooling to room temperature at a cooling rate of 1°C / min, and obtaining a low residual alkali lithium-rich manganese-based positive electrode material after crushing, and storing the obtained positive electrode material in an inert atmosphere for standby use.

[0050] Comparative Example 2

[0051] This comparative example provides a method for preparing a low-residual-lithium-rich lithium-manganese-based positive electrode material, and the specific steps are as follows:

[0052] 1) According to the molar ratio of the metal element in the lithium-rich manganese-based precursor to the lithium element in the lithium source of 1:1.5, weigh Ni 0.35 Mn 0.65 (OH)2 and lithium carbonate, among which Ni 0.35 Mn 0.65 The specific surface area of ​​the (OH)2 precursor is 41 m 2 / g, tap density is 1.82g / cm 3 , the median particle size D50 is 5.7 μm, the above raw materials are mixed evenly with a high-speed mixer to obtain a mixed powder;

[0053] 2) placing the mixed powder in step 1) in a box furnace, the sintering atmosphere is compressed air, the air flow rate is 10L / min, first heating to 500°C at a heating rate of 2°C / min and sintering for 4h, then heating to 900°C at a heating rate of 2°C / min and calcining at high temperature for 10h, and finally cooling to room temperature at a cooling rate of 1°C / min, and obtaining a low residual alkali lithium-rich manganese-based positive electrode material after crushing, and the obtained positive electrode material is placed in an inert atmosphere for storage and standby.

[0054] Comparative Example 3

[0055] This comparative example provides a method for preparing a low-residual-lithium-rich lithium-manganese-based positive electrode material, and the specific steps are as follows:

[0056] 1) According to the molar ratio of the metal element in the lithium-rich manganese-based precursor to the lithium element in the lithium source of 1:1.5, weigh Ni 0.35 Mn 0.65 (OH)2 and lithium carbonate, among which Ni 0.35 Mn 0.65 The specific surface area of ​​the (OH)2 precursor is 41 m 2 / g, tap density is 1.82g / cm 3 , the median particle size D50 is 5.7 μm, the above raw materials are mixed evenly with a high-speed mixer to obtain a mixed powder;

[0057] 2) placing the mixed powder in step 1) in a box furnace, the sintering atmosphere is compressed air, the air flow rate is 10L / min, first heating to 500°C at a heating rate of 2°C / min and sintering for 4h, then heating to 700°C at a heating rate of 2°C / min and calcining at high temperature for 5h, and finally cooling to room temperature at a cooling rate of 1°C / min, and obtaining a low residual alkali lithium-rich manganese-based positive electrode material after crushing, and the obtained positive electrode material is placed in an inert atmosphere for storage and standby.

[0058] Comparative Example 4

[0059] This embodiment provides a method for preparing a low-residual-lithium-rich lithium-manganese-based positive electrode material, and the specific steps are as follows:

[0060] 1) According to the molar ratio of the metal element in the lithium-rich manganese-based precursor to the lithium element in the lithium source of 1:1.5, weigh Ni 0.35 Mn 0.65 (OH)2 and lithium carbonate, among which Ni 0.35 Mn 0.65 The specific surface area of ​​the (OH)2 precursor is 41 m 2 / g, tap density is 1.82g / cm 3 , the median particle size D50 is 5.7 μm, the above raw materials are mixed evenly with a high-speed mixer to obtain a mixed powder;

[0061] 2) placing the mixed powder in step 1) in a box furnace, the sintering atmosphere is compressed air, the air flow rate is 10L / min, first heating to 350°C at a heating rate of 2°C / min and sintering for 3h, then heating to 450°C at a heating rate of 2°C / min and calcining at high temperature for 4h, then heating to 850°C at a heating rate of 2°C / min and calcining at high temperature for 12h, finally cooling to room temperature at a cooling rate of 1°C / min, and obtaining a low residual alkali lithium-rich manganese-based positive electrode material after crushing, and the obtained positive electrode material is placed in an inert atmosphere for storage and standby.

[0062] Comparative Example 5

[0063] This comparative example provides a method for preparing a low-residual-lithium-rich lithium-manganese-based positive electrode material, and the specific steps are as follows:

[0064] 1) According to the molar ratio of the metal element in the lithium-rich manganese-based precursor to the lithium element in the lithium source of 1:1.5, weigh Ni 0.35 Mn 0.65 (OH)2 and lithium carbonate, among which Ni 0.35 Mn 0.65 The specific surface area of ​​the (OH)2 precursor is 41 m 2 / g, tap density is 1.82g / cm 3 , the median particle size D50 is 5.7 μm, the above raw materials are mixed evenly with a high-speed mixer to obtain a mixed powder;

[0065] 2) placing the mixed powder in step 1) in a box furnace, the sintering atmosphere is compressed air, the air flow rate is 10L / min, first heating to 250°C at a heating rate of 2°C / min and sintering for 4h, then heating to 700°C at a heating rate of 2°C / min and calcining at high temperature for 5h, then heating to 900°C at a heating rate of 2°C / min and calcining at high temperature for 10h, finally cooling to room temperature at a cooling rate of 1°C / min, and obtaining a low residual alkali lithium-rich manganese-based positive electrode material after crushing, and storing the obtained positive electrode material in an inert atmosphere for standby use.

[0066] Comparative Example 6

[0067] This comparative example provides a method for preparing a low-residual-lithium-rich lithium-manganese-based positive electrode material, and the specific steps are as follows:

[0068] 1) According to the molar ratio of the metal element in the lithium-rich manganese-based precursor to the lithium element in the lithium source of 1:1.5, weigh Ni 0.35 Mn 0.65 (OH)2 and lithium carbonate, among which Ni0.35 Mn 0.65 The specific surface area of ​​the (OH)2 precursor is 41 m 2 / g, tap density is 1.82g / cm 3 , the median particle size D50 is 5.7 μm, the above raw materials are mixed evenly with a high-speed mixer to obtain a mixed powder;

[0069] 2) placing the mixed powder in step 1) in a box furnace, the sintering atmosphere is compressed air, the air flow rate is 10L / min, first heating to 600°C at a heating rate of 2°C / min and sintering for 4h, then heating to 700°C at a heating rate of 2°C / min and calcining at high temperature for 5h, then heating to 900°C at a heating rate of 2°C / min and calcining at high temperature for 10h, finally cooling to room temperature at a cooling rate of 1°C / min, and obtaining a low residual alkali lithium-rich manganese-based positive electrode material after crushing, and storing the obtained positive electrode material in an inert atmosphere for standby use.

[0070] Comparative Example 7

[0071] This comparative example provides a method for preparing a low-residual-lithium-rich lithium-manganese-based positive electrode material, and the specific steps are as follows:

[0072] 1) According to the molar ratio of the metal element in the lithium-rich manganese-based precursor to the lithium element in the lithium source of 1:1.5, weigh Ni 0.35 Mn 0.65 (OH)2 and lithium carbonate, among which Ni 0.35 Mn 0.65 The specific surface area of ​​the (OH)2 precursor is 41 m 2 / g, tap density is 1.82g / cm 3 , the median particle size D50 is 5.7 μm, the above raw materials are mixed evenly with a high-speed mixer to obtain a mixed powder;

[0073] 2) placing the mixed powder in step 1) in a box furnace, the sintering atmosphere is compressed air, the air flow rate is 10L / min, first heating to 500°C at a heating rate of 2°C / min and sintering for 4h, then heating to 550°C at a heating rate of 2°C / min and calcining at high temperature for 5h, then heating to 900°C at a heating rate of 2°C / min and calcining at high temperature for 10h, finally cooling to room temperature at a cooling rate of 1°C / min, and obtaining a low residual alkali lithium-rich manganese-based positive electrode material after crushing, and storing the obtained positive electrode material in an inert atmosphere for standby use.

[0074] Comparative Example 8

[0075] This comparative example provides a method for preparing a low-residual-lithium-rich lithium-manganese-based positive electrode material, and the specific steps are as follows:

[0076] 1) According to the molar ratio of the metal element in the lithium-rich manganese-based precursor to the lithium element in the lithium source of 1:1.5, weigh Ni 0.35 Mn 0.65 (OH)2 and lithium carbonate, among which Ni 0.35 Mn 0.65 The specific surface area of ​​the (OH)2 precursor is 41 m 2 / g, tap density is 1.82g / cm 3 , the median particle size D50 is 5.7 μm, the above raw materials are mixed evenly with a high-speed mixer to obtain a mixed powder;

[0077] 2) placing the mixed powder in step 1) in a box furnace, the sintering atmosphere is compressed air, the air flow rate is 10L / min, first heating to 500°C at a heating rate of 2°C / min and sintering for 4h, then heating to 800°C at a heating rate of 2°C / min and calcining at high temperature for 5h, then heating to 900°C at a heating rate of 2°C / min and calcining at high temperature for 10h, finally cooling to room temperature at a cooling rate of 1°C / min, and obtaining a low residual alkali lithium-rich manganese-based positive electrode material after crushing, and storing the obtained positive electrode material in an inert atmosphere for standby use.

[0078] Comparative Example 9

[0079] This comparative example provides a method for preparing a low-residual-lithium-rich lithium-manganese-based positive electrode material, and the specific steps are as follows:

[0080] 1) According to the molar ratio of the metal element in the lithium-rich manganese-based precursor to the lithium element in the lithium source of 1:1.5, weigh Ni 0.35 Mn 0.65 (OH)2 and lithium carbonate, among which Ni 0.35 Mn 0.65 The specific surface area of ​​the (OH)2 precursor is 41 m 2 / g, tap density is 1.82g / cm 3 , the median particle size D50 is 5.7 μm, the above raw materials are mixed evenly with a high-speed mixer to obtain a mixed powder;

[0081] 2) placing the mixed powder in step 1) in a box furnace, the sintering atmosphere is compressed air, the air flow rate is 10L / min, first heating to 500°C at a heating rate of 2°C / min and sintering for 4h, then heating to 700°C at a heating rate of 2°C / min and calcining at high temperature for 5h, then heating to 750°C at a heating rate of 2°C / min and calcining at high temperature for 10h, finally cooling to room temperature at a cooling rate of 1°C / min, and obtaining a low residual alkali lithium-rich manganese-based positive electrode material after crushing, and storing the obtained positive electrode material in an inert atmosphere for standby use.

[0082] Comparative Example 10

[0083] This comparative example provides a method for preparing a low-residual-lithium-rich lithium-manganese-based positive electrode material, and the specific steps are as follows:

[0084] 1) According to the molar ratio of the metal element in the lithium-rich manganese-based precursor to the lithium element in the lithium source of 1:1.5, weigh Ni 0.35 Mn 0.65 (OH)2 and lithium carbonate, among which Ni 0.35 Mn 0.65 The specific surface area of ​​the (OH)2 precursor is 41 m 2 / g, tap density is 1.82g / cm 3 , the median particle size D50 is 5.7 μm, the above raw materials are mixed evenly with a high-speed mixer to obtain a mixed powder;

[0085] 2) placing the mixed powder in step 1) in a box furnace, the sintering atmosphere is compressed air, the air flow rate is 10L / min, first heating to 500°C at a heating rate of 2°C / min and sintering for 4h, then heating to 700°C at a heating rate of 2°C / min and calcining at high temperature for 5h, then heating to 1000°C at a heating rate of 2°C / min and calcining at high temperature for 10h, finally cooling to room temperature at a cooling rate of 1°C / min, and obtaining a low residual alkali lithium-rich manganese-based positive electrode material after crushing, and storing the obtained positive electrode material in an inert atmosphere for standby use.

[0086] Test Example 1

[0087] The electrical properties of the low residual alkali lithium-rich manganese-based positive electrode materials prepared in the embodiment and the comparative example were tested under the following test conditions: first, the main material (low residual alkali lithium-rich manganese-based positive electrode material), polyvinylidene fluoride (PVDF), and Super P (SP) were weighed and homogenized in a weight ratio of 8:1:1, and then the aluminum foil was spread flat on a coating machine for coating (surface density 16 mg / cm 2 ), put it into an 80℃ forced air drying oven and dry it for 2h; then punch, weigh, bake the electrode piece, and make it into a CR2032 button battery. Finally, put the battery into the blue electric test system for electrical performance test. The electrical performance test parameters are set as follows: charging cutoff voltage is 4.65V, discharging cutoff voltage is 2.5V; the first cycle is 0.1C charging, 0.1C discharging; the second cycle is 0.5C charging, 0.5C discharging; the third cycle is 1.0C charging, 1.0C discharging; then 1C charging and 1C discharging are cycled 200 times to test the cycle retention rate. The test results are shown in Table 1;

[0088] Table 1

[0089]

[0090] Obviously, the above embodiments are merely examples for the purpose of clear explanation, and are not intended to limit the implementation methods. For those skilled 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 list all the implementation methods here. The obvious changes or modifications derived therefrom are still within the scope of protection of the invention.

Claims

1. A method for preparing a low-residual-alkali lithium-rich manganese-based positive electrode material, characterized in that: include: Mixing the lithium-rich manganese-based precursor with the lithium source to obtain a mixed powder; The mixed powder is subjected to a three-stage sintering treatment; wherein the temperature of the first stage sintering treatment is 350-550°C, the temperature of the second stage sintering treatment is 650-700°C, and the temperature of the third stage sintering treatment is 850-950°C.

2. The preparation method according to claim 1, characterized in that: The lithium source is at least one of lithium carbonate, lithium hydroxide and lithium acetate.

3. The preparation method according to claim 1 or 2, characterized in that: The chemical formula of the lithium-rich manganese-based precursor is Ni x Mn 1-x (OH)2, 0<x<0.

5.

4. The preparation method according to any one of claims 1 to 3, characterized in that: The molar ratio of the metal element in the lithium-rich manganese-based precursor to the lithium element in the lithium source is 1:(1.35-1.55).

5. The preparation method according to any one of claims 1 to 4, characterized in that: The atmosphere of the three-stage sintering treatment is an oxygen-containing atmosphere and / or an inert atmosphere.

6. The preparation method according to any one of claims 1 to 5, characterized in that: The holding time of the first stage sintering treatment is 4-6 hours; And / or, the heat preservation time of the second sintering treatment is 4-6h; And / or, the heat preservation time of the third sintering treatment is 8-12 hours.

7. The preparation method according to any one of claims 1 to 6, characterized in that: The heating rate of the three-stage sintering process is 2-5°C / min; And / or, the three-stage sintering treatment is followed by cooling at a rate of 1-2°C / min.

8. The preparation method according to claim 7, characterized in that: After the cooling, the powder is crushed and screened.

9. A low residual alkali lithium-rich manganese-based positive electrode material, characterized in that: The cathode material is prepared by the method for preparing the low-residual-alkali lithium-rich manganese-based cathode material according to any one of claims 1 to 8.

10. Use of the low residual alkali lithium-rich manganese-based positive electrode material according to claim 9 in lithium-ion batteries.

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