A kind of method for reducing residual alkali content of nickel cobalt lithium manganate

Abstract

The invention discloses a method for reducing the content of residual alkaline in nickel cobalt manganese acid lithium. According to the method, LiH2PO4 serving as an alkaline treatment agent is used for removing alkaline components such as LiOH, Li2CO3 and LiHCO3 retained in a nickel cobalt manganese acid lithium positive electrode material, so that the structure of the positive electrode material cannot be damaged; furthermore, the circulating performance and the compaction density of the positive electrode material can be improved, and the performance of the battery can be improved; meanwhile, the method is simple and feasible and is suitable for industrial production.

Description

technical field [0001] The invention relates to the field of lithium ion batteries, in particular to a method for reducing the residual alkali content of nickel-cobalt lithium manganese oxide. Background technique [0002] Nickel-cobalt lithium manganese oxide, which is used as the positive electrode material of lithium-ion batteries, has the advantages of low cost, relatively simple manufacturing process, relatively high specific capacity and weight specific energy, relatively low toxicity and relatively abundant raw material sources, so it is a lithium-ion battery. It is an important positive electrode material for batteries, especially lithium-ion power batteries. [0003] The increase of the relative content of nickel element in nickel cobalt lithium manganese oxide positive electrode material can increase the specific capacity of the positive electrode material, thereby increasing the specific energy of the battery system, but when the content of nickel element containe...

AI Technical Summary

Problems solved by technology

[0005] (1) When feeding the synthesis reaction, reduce the proportion of lithium-containing raw materials, make the nickel-cobalt-manganese precursor excessive in the chemical reaction, move the chemical reaction balance forward, and reduce the residual alkali content in the final product, but this method will reduce the final product The electrochemical specific capacity and compaction density of the material, and the degree of reduction of residual alkali by this method is limited, only about 20% of residual alkali can be reduced. In actual production, it is mostly used to fine-tune and balance the residual alkali in nickel-cobalt lithium manganate cathode material Content and compaction density, can not efficiently improve the performance of positive electrode materials, such as Chinese patent CN201310079543.2, in the process of preparing lithium batteries, lithium salt is added twice, the operation steps are cumbersome and complicated, and the total preparation time is as long as 25 to 120 hours, and The capacity holding capacity after 50 cycles is 140mAh / g;

[0006] (2) During high-temperature treatment, increase the reaction temperature during the firing process of the material and prolong the high-temperature treatment time to promote a more thorough synthesis reaction and partially volatilize the lithium element under high-temperature conditions, thereby reducing the residual in the final product However, with the increase of the treatment temperature and the extension of the high-temperature treatment time in this method, the lithium atoms in the material and the nickel atoms in the transition metal layer will transpose each other, making the structure of the material unstable, so the positive electrode material The specific capacity and cycle performance are all seriously reduced, and the method can only reduce the residual alkali by 10%;

[0007] (3) After synthesizing the positive electrode material, add manganese carbonate and other additives that are easy to react with lithium-containing alkaline substances at high temperature into the fired material, so that it can consume the residual alkali in the positive electrode material during high temperature treatment, thereby reducing the The residual alkali content of the material; this method can reduce the residual alkali in the material by about 50%, but due to the high residual alkali content in the positive electrode material, it is usually necessary to add a large amount of manganese carbonate additive, and manganese carbonate will change the performance of the positive electrode material, making the positive electrode The specific capacity, discharge platform and compaction density of the material are all reduced, and the additives used are required to be of high purity and small particle size, generally not exceeding 1 micron. Therefore, the industrial production cost is relatively high, and it is generally used for high-end cobalt acid at present. The production of lithium cathode materials is rarely used in the large-scale production of nickel-cobalt lithium manganese oxide cathode materials;

[0008] (4) Add weakly acidic organic substances, such as oxalic acid, to neutralize the residual alkali in the positive electrode material during the pulping process of the positive electrode material. This method can improve the process technology of the full battery to a certain extent, but due to the The reaction produces water, and the water will react with the positive electrode slurry and consume the slurry, which will seriously affect the subsequent use of the positive electrode material and have a negative impact on the cycle performance of the positive electrode material, and the weakly acidic organic matter cannot be completely removed. In a full battery, a large amount of gas will be produced when it is charged for the first time, so this method is not suitable for manufacturing pouch batteries;

[0009] (5) Add the positive electrode material to the bicarbonate solution or water, wash and process the product at high temperature. For example, Chinese patent CN102683672A discloses a method for reducing the pH value of the ternary material. This method does not exceed the nickel element content. 50% nickel-cobalt lithium manganese oxide cathode material has good feasibility, but for materials with high nickel content, bicarbonate has limited solubility, and at the same time it is extremely easy to decompose, and actual industrial production is likely to cause the residual lithium hydroxide to decrease. Small, the phenomenon that the residual amount of lithium carbonate increases is limited for the application of ternary materials in flexible packaging full batteries, and the material is in an alkaline environment, so it is not easy to reduce the residual alkali; another example is the Chinese patent CN101450815, which uses ammonium carbonate as a pH regulator agent, which does not characterize the effect of pH adjustment, and the resulting positive electrode material has poor cycle performance of the battery

[0011] At present, there is no use of LiH 2 PO 4 Report on Reducing Residual Alkali Content of Nickel Cobalt Lithium Manganate Cathode Material as Alkaline Neutralizer