Nickel-manganese-doped binary method for lithium battery positive electrode material

Abstract

The invention belongs to the field of metallurgical electrode materials, and particularly relates to a nickel-manganese-doped binary method for a lithium battery positive electrode material. Comprising the following steps: (1) mixing lithium molybdate with a precursor and a lithium source, and adding water in the mixing process to obtain a water-containing wet material with the water mass fraction of 1-5%; and (2) carrying out subsequent high-temperature sintering on the water-containing wet material, cooling, crushing and sieving to obtain the molybdenum-doped positive electrode material. The prepared positive electrode material can realize uniform doping of the molybdenum element, and the material after high-temperature synthesis is not agglomerated and is easy to crush, so that subsequent treatment is facilitated.

Description

Technical Field

[0001] The present invention belongs to the field of metallurgical electrode materials, and particularly relates to a method for doping nickel and manganese into a cathode material of a lithium battery. Background Art

[0002] As a new generation of environmentally friendly and high-energy batteries, the improvement of the performance of lithium-ion batteries has become one of the research hotspots in the battery industry. Doping and coating the cathode material of lithium-ion batteries are the main methods to improve the comprehensive performance of the cathode material.

[0003] Existing research shows that doping nickel and manganese is beneficial to improving the capacity, conductivity and cycling performance of the cathode material. A large number of Chinese patent documents disclose methods for doping nickel and manganese into lithium manganate, ternary materials (NCM and NCA), lithium-rich manganese-based materials and nickel-manganese binary materials, etc. The disclosed methods for doping nickel and manganese include the method of doping nickel and manganese into the precursor by precipitation, the method of doping nickel and manganese by evaporating the mother liquor to dryness, and the method of doping nickel and manganese by solid-phase mixing, etc.

[0004] The method of doping nickel and manganese into the precursor by precipitation is to add a soluble nickel-manganese binary source during the production of the cathode precursor, and co-precipitate nickel and manganese together with other main metal ions (such as nickel, manganese, cobalt) through a precipitant to obtain the precursor, and then mix lithium with the precursor, and obtain the cathode material doped with nickel and manganese through high-temperature solid-phase synthesis. Because nickel and manganese elements are easy to form nickel-manganese binary salts with relatively high solubility, although this method has been reported, the content of nickel and manganese in the actual precipitate is very low, and the target doping ratio of nickel and manganese cannot be achieved, and the purpose of doping and modifying nickel and manganese cannot be achieved.

[0005] The method of doping nickel and manganese by evaporating the mother liquor to dryness is divided into two cases. One is represented by the sol-gel method, in which a soluble nickel-manganese binary source and a main metal salt are added to a lithium source solution during the preparation of the precursor, and after corresponding treatment, the mother liquor is evaporated to dryness to prepare the precursor doped with nickel and manganese, and then high-temperature solid-phase synthesis is carried out; the other is to mix a soluble nickel-manganese binary source solution and a precursor with a lithium source and then evaporate to dryness, and then carry out high-temperature solid-phase synthesis. These methods all require drying a large amount of mother liquor, with high energy consumption and complex processes, which is not conducive to industrial production.

[0006] Summary of the Invention

[0007] The technical problem to be solved by the present invention is that the existing molybdenum doping methods cannot simultaneously meet the requirements of low energy consumption and uniform diffusion. In order to overcome the above-mentioned deficiencies and defects in the background art, the present invention provides a method for doping molybdenum into a cathode material of a lithium battery with uniform doping and simple process.

[0008] To solve the above technical problem, the technical solution proposed by the present invention is as follows:

[0009] A method for doping molybdenum into a cathode material of a lithium battery, comprising the following steps:

[0010] (1) Mix lithium molybdate with a precursor and a lithium source, and water needs to be added during the mixing process to obtain a wet material containing water with a water mass fraction of 1%-5%.

[0011] (2) Subject the wet material containing water to subsequent high-temperature sintering, and after cooling, obtain a molybdenum-doped cathode material through pulverization and sieving.

[0012] Preferably, in step (1), a lithium molybdate solution is used to mix with the precursor and the lithium source. In this step, the water content of the wet material is relatively small, and using a lithium molybdate solution is beneficial to ensuring the complete dissolution of lithium molybdate.

[0013] Preferably, the concentration of the lithium molybdate solution is 1-3 mol / L, which is specifically determined according to the target molybdenum doping amount and the target water content of the subsequent wet material. The lithium molybdate can be directly purchased from the market or obtained by reacting molybdenum trioxide with lithium hydroxide.

[0014] Preferably, the lithium source material in step (1) includes any one or more of lithium carbonate or lithium hydroxide.

[0015] Preferably, the water content mass fraction of the wet material containing water in step (1) is 2%-3%. The wet material containing water can enhance the uniform mass transfer of molybdenum and lithium elements. Both molybdenum and lithium elements effectively migrate to the surface of the precursor particles, into the micropores of the precursor particles, or the contact gaps between the precursor particles by means of water, realizing the uniform doping of molybdenum elements and the uniform mixing of lithium elements. If the water content rate is too low, the uniform mass transfer effect of molybdenum and lithium elements will be reduced, while if the water content is too high, segregation of molybdenum and lithium elements will occur during the water evaporation process before subsequent high-temperature synthesis, which will instead have a negative effect and cause non-uniformity.

[0016] Preferably, for the high-temperature sintering in step (2), the wet material is directly fed into a roasting furnace without drying. When synthesizing cathode materials, a continuous roller hearth kiln or a continuous tunnel kiln is usually used. During the movement of the material, vibration inevitably exists. If the dried material enters the furnace, as the material is pushed forward, the material layer will become denser and denser, hindering the mass transfer of oxygen in the ambient atmosphere to oxidize the material, and it is easy to cause incomplete oxidation and material agglomeration, and secondary roasting is required after crushing. The method of feeding the wet material into the furnace in the present invention can, on the one hand, reduce the fluidity of the material and prevent the material layer from becoming dense, and on the other hand, a large number of microporous channels are generated in the material layer due to water evaporation, which is beneficial to the mass transfer of oxygen in the ambient atmosphere.

[0017] Preferably, the molybdenum-doped cathode material obtained in the step (2) is at least one of molybdenum-doped lithium manganese oxide cathode material, molybdenum-doped lithium cobalt oxide cathode material, molybdenum-doped ternary cathode material, molybdenum-doped nickel manganese binary material, and molybdenum-doped lithium-rich manganese-based cathode material. Correspondingly, the precursor is the precursor of the corresponding molybdenum-doped cathode material. When producing lithium manganese oxide, the precursor material can be manganese dioxide, manganese tetroxide or manganese carbonate; when producing ternary materials (NCM or NCA), the precursor material can be nickel cobalt manganese oxide or hydroxide (for NCM), nickel cobalt aluminum oxide or hydroxide (for NCA); when producing nickel manganese binary or lithium-rich manganese-based materials, the precursor materials can be nickel manganese binary precursor or lithium-rich manganese-based precursor respectively.

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

[0019] (1) The cathode material prepared by this method can achieve uniform doping of molybdenum element, and the material after high-temperature synthesis does not agglomerate and is easy to crush, which is convenient for subsequent processing;

[0020] (2) It significantly improves the processing performance and electrical performance of the cathode material, and the specific capacity of the cathode material increases significantly;

[0021] (3) The production process is simple. There is no need to dry a large amount of mother liquor and then mix it. Only one high-temperature roasting is required, and no secondary sintering is needed, which is easy for industrial production. Specific embodiments

[0022] The present invention will be further described below in conjunction with embodiments:

[0023] Comparative example 1:

[0024] Lithium manganese oxide product comparative example 1: Using electrolytic manganese dioxide to synthesize lithium manganese oxide.

[0025] (1) Take 800 Kg of electrolytic manganese dioxide with a particle size D50 of 16 μm, add lithium carbonate according to a lithium-manganese ratio of 0.54, put it into an inclined mixer with a volume of 2.5 cubic meters and mix for 2 hours. After detection, the moisture content of the mixed material is 0.6%;

[0026] (2) Load the mixed material into the sagger, control the thickness of the material layer in the sagger to be 6 cm, and the material enters the roller hearth kiln with the sagger. Control the heating rate of the heating section of the roller hearth kiln to be 5 °C / min. After the material is calcined at 800 °C for 15 hours, it is cooled to about 100 °C in 6 hours and taken out of the furnace. The material in the sagger is loose and does not agglomerate, and then it is crushed and sieved to obtain the lithium manganese oxide product.

[0027] Example 1:

[0028] Lithium manganese oxide product example 1: Using electrolytic manganese dioxide to synthesize lithium manganese oxide doped with 0.5% molybdenum.

[0029] (1) Prepare a lithium molybdate solution with a concentration of 1.8 mol / L; take 800 Kg of electrolytic manganese dioxide with a particle size D50 of 16 μm, add lithium carbonate according to a lithium-manganese ratio of 0.54, and put it into an inclined mixer with a volume of 2.5 cubic meters and mix for 2 hours; add 22.6 L of the prepared lithium molybdate solution and continue mixing for 0.5 hours. After testing, a mixed material with a moisture content of 2.8% is obtained.

[0030] (2) Load the wet material into the sagger, control the thickness of the material layer in the sagger to be 6 cm, and the material enters the roller hearth kiln with the sagger. Control the heating rate of the heating section of the roller hearth kiln to be 5 °C / min. After the material is calcined at 800 °C for 15 hours, it is cooled to about 100 °C in 6 hours and then taken out of the furnace. The material in the sagger is loose and does not agglomerate. Then, it is pulverized and sieved to obtain the lithium manganate product.

[0031] In the present invention, the description of the direction and relative position relationship of the structure, such as the description of front, back, left, right, up, and down, does not constitute a limitation to the present invention, but is only for convenience of description.

Claims

1. A method for doping nickel and manganese in a cathode material of a lithium battery, characterized in that, it includes the following steps: (1) Mix lithium nickel manganese binary acid with a precursor and a lithium source, and water needs to be added during the mixing process to obtain a water-containing wet material with a water mass fraction of 1%-5%; (2) Subject the water-containing wet material to subsequent high-temperature sintering, and after cooling, pulverize and screen it to obtain a nickel- and manganese-doped cathode material.

2. The method for doping nickel and manganese in a cathode material of a lithium battery according to claim 1, characterized in that, in step (1), a lithium nickel manganese binary acid solution is used to mix with the precursor and the lithium source.

3. The method for doping nickel and manganese in a cathode material of a lithium battery according to claim 2, characterized in that, the concentration of the lithium nickel manganese binary acid solution is 1-3 mol / L.

4. The method for doping nickel and manganese in a cathode material of a lithium battery according to claim 1, characterized in that, the lithium source in step (1) includes at least one of lithium carbonate or lithium hydroxide.

5. The method for doping nickel and manganese in a cathode material of a lithium battery according to claim 1, characterized in that, the water mass fraction of the water-containing wet material in step (1) is 2%-3%.

6. The method for doping nickel and manganese in a cathode material of a lithium battery according to claim 1, characterized in that, the high-temperature sintering in step (2) means directly feeding the water-containing wet material into a roasting furnace without drying.

7. The method for doping nickel and manganese in a cathode material of a lithium battery according to any one of claims 1-6, characterized in that, the obtained nickel- and manganese-doped cathode material is at least one of a nickel- and manganese-doped lithium manganate cathode material, a nickel- and manganese-doped lithium cobaltate cathode material, a nickel- and manganese-doped ternary cathode material, a nickel- and manganese-doped lithium nickel manganese binary cathode material, and a nickel- and manganese-doped lithium-rich manganese-based cathode material; correspondingly, the precursor is the precursor of the corresponding nickel- and manganese-doped cathode material.