Two-layer coated modified ternary cathode high-nickel material and preparation method thereof

Abstract

The invention provides a two-layer coated modified ternary cathode high-nickel material and a preparation method thereof. The double-layer coated modified ternary cathode high-nickel material has a double-layer coated structure which is composed of a Ni-Co lithium manganate substrate, a manganese oxide layer coating layer and a metal oxide outer layer coating layer. The preparation method comprises coating the ternary cathode material precursor NixCoyMn1-x-y(OH)2 as a precursor with the manganese oxide and the metal oxide. The method not only reduces the residual alkali on the surface of the material, but also stabilizes the Ni4+ generated by the material when fully charged, improves the high temperature storage performance and the safety performance. Further, the coated nano metal oxide at the outer layer effectively prevents the electrolyte from reacting with the material, improves the cycle performance of the material, increases the material capacity retention rate, and reduces thecost.

Description

technical field [0001] The invention relates to the field of positive electrode materials for batteries, in particular to a high-nickel positive electrode material in a lithium ion battery and a preparation method thereof. Background technique [0002] Since the commercial application of lithium-ion secondary batteries for the first time, it has rapidly become the current electronic consumer products such as mobile phones, computers, The main provider of electrical energy required by devices such as cameras. In recent years, with the vigorous development of electric vehicles and other industries, the current commercial lithium-ion battery cathode materials can no longer meet the requirements of high-power batteries, and high-capacity cathode materials have become a current research hotspot. Among them, nickel-cobalt-manganese ternary cathode material LiMO 2 (M=Ni, Co, Mn) has become the most promising cathode material for lithium-ion secondary batteries due to its higher t...

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Problems solved by technology

At the same time, when the Ni content exceeds 60%, the positive electrode is in the delithiated state. 4+ The content will also increase, and Ni4 + It is very unstable and highly oxidizing, which can easily cause side reactions between the electrode and the electrolyte, which will sharply reduce the cycle performance and thermal stability of the material, thereby affecting the practical use of materials with high nickel content.

[0003] At the same time, materials with high nickel content (>60%) are prone to excessive residual alkali content on the surface during sintering, because during the cooling stage, materials with high nickel content (>60%) will interact with moisture in the air And carbon dioxide, and then generate lithium hydroxide, lithium carbonate and other impurities, which will cause the residual alkali content of the sintered material to be too high

During the battery manufacturing process, the residual alkali on the surface will decompose to varying degrees during the charging and discharging process, thereby producing CO 2 Such gases make the material easy to produce gas in actual use, causing the thickness of the battery to change and affecting the actual use of the material

If under the environmental conditions such as overcharging, the residual alkali on the surface can easily cause rapid side reactions and generate a large amount of gas and heat, resulting in thermal runaway of the battery, eventually leading to combustion and explosion of the battery, etc.

In order to reduce the amount of residual alkali on the surface of materials with high nickel content (>60%), the amount of lithium added during the sintering process can be reduced, but this often loses the electrical properties of the obtained materials, that is, cycle stability and discharge are often not obtained. The material with the best specific capacity

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