A surface-modified ternary positive electrode material, its preparation method, and a battery made thereof

Abstract

A surface modify ternary cathode material is prepared by coat a surface modified layer on that core of the ternary cathode material; The ternary cathode material core is Li1+kNixCoyMzO2, wherein M isone of Al, Mn, Ti and Mg, and the ternary cathode material core is Li1+kNixCoyMzO2, wherein M is one of Al, Mn, Ti and Mg. 0.1 <= k <= 0. 1, 0 < x < 1, 0 < y < 1, 0 < z < 1; The surface modification layer is formed of two surface modification substances, one is yttria stabilized zirconia, the other is oxide, selected from Al2O3, SiO2, MgO and ZrO2. The invention also provides a preparation methodof the surface-modified ternary cathode material and a battery made of the surface-modified ternary cathode material. The YSZ provided by the invention is an oxide containing oxygen vacancies, which is favorable for lithium ion migration. The surface of the high nickel ternary cathode material modified by the YSZ has a faster lithium ion migration rate, and the lithium ion diffusion problem can bewell improved by covering the surface of the high nickel ternary cathode material, and the magnification performance of the material can be improved.

Description

technical field [0001] The invention belongs to the field of battery materials, and in particular relates to a ternary positive electrode material of a lithium ion battery, a preparation method thereof, and a battery made of the positive electrode material. Background technique [0002] As a new type of green high-energy battery, lithium-ion batteries are widely used in portable electronic products, and are expanding to new energy electric vehicles and other fields. higher requirement. Cathode materials are an important part of lithium-ion batteries, accounting for about 30%-40% of the total cost of the entire battery. Therefore, improving the performance of cathode materials is extremely critical for the development of lithium-ion batteries. [0003] High nickel ternary layered cathode material Li[Ni x co y m 1-x-y ]O 2 (x≥0.8, M is Al, Mn, etc.) is considered to be one of the most promising cathode materials that can meet the application, however, there are still som...

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Problems solved by technology

[0003] High nickel ternary layered cathode material Li[Ni x co y m 1-x-y ]O 2 (x≥0.8, M is Al, Mn, etc.) is considered to be one of the most promising cathode materials that can meet the application, however, there are still some problems with this system material as a candidate material for high-energy lithium-ion batteries: first, at high temperature During the synthesis process due to the Ni 3+ unstable and easily reduced to Ni 2+ and due to Li + and Ni 2+ The similar ionic radius of the resulting Li + / Ni 2+ Mixed arrangement makes the solid-phase diffusion of lithium ions more difficult and increases the polarization of the material; secondly, due to the easily reduced Ni 4+ Especially in the highly delithiated state, the surface of the positive electrode material is prone to side reactions with the electrolyte to form an electrochemically inert layer, accompanied by the generation of impurity phases such as spinel phase and rock salt, which inhibits the The diffusion of lithium ions, accompanied by the loss of oxygen in the bulk material at the same time, reduces the safety performance; in addition, during the lithium intercalation process, the generation of microcracks inside the secondary particles caused by the multiphase transformation causes the electrolyte to The corrosion of the material is further intensified, and the surface resistance is further increased

Patent CN 107331852 A proposes a kind of oxide (Nb 2 o 5 , ZrO 2 and Y 2 o 3 ) method of coating the surface of the ternary positive electrode material. The coating reduces the side reaction between the electrolyte and the positive electrode material to a certain extent, improves the cycle performance and thermal stability of the material, but the effect is limited, and it will bring negative effects at the same time. Effect, because the coated metal oxide is an inert material, which inhibits the transport of lithium ions and electrons

Patent CN 104995769 A dry-coats layered materials by doping oxides, and the cycle performance is improved, but the contribution of the coating layer to the material performance is single. It only illustrates the role of oxygen vacancies in promoting lithium ion transport, and does not mention The synergistic effect of YSZ and other materials, and the method is to coat the finished product, using high-temperature post-heat treatment, it is difficult to form a layered material doped on the surface, only a certain thickness of the coating layer is formed, and there is a problem with lithium ion diffusion. hindrance

Patent CN 105938901 A coats layered materials by oxide dry method, which improves the cycle performance, but the coating amount is small, and there is no suitable post-heat treatment, which makes it difficult for the coating layer to evenly coat the material. The solid interface between the cladding and the bulk material is not connected, which hinders the diffusion of lithium ions and hinders the diffusion of electrolyte

Patent CN108258224A proposes a method for preparing a ternary positive electrode material coated with metal oxide on the surface. Not only the preparation method is cumbersome, but also the inert oxide surface coating layer will inevitably lead to the decline of the first discharge specific capacity and rate performance

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