Core-shell high-voltage monocrystal nickel cobalt lithium manganate positive electrode material and preparation method and application thereof

Abstract

The invention discloses a core-shell high-voltage monocrystal nickel cobalt lithium manganate positive electrode material and a preparation method and application thereof, and the positive electrode material comprises a core layer and a shell layer arranged on the outer surface of the core layer, wherein the core layer and the shell layer form a core-shell structure. The core layer is made of Lia(NixCoyMn<1-x-y>)O2, wherein 1.0 <= a <= 1.15, 0.2 <= x <= 0.6, 0.1 <= y <= 0.5, 1-x-y > 0, and the material of the core layer is of a monocrystal type; the material of the shell layer is LibCokM<1-k>O2, wherein 0.9 <= b <= 1.05, 0.8 <= k <= 0.99, and M is one or more of Mg, Al, Zr, Ti and W. The preparation method comprises the following steps: firstly preparing monocrystal lithium nickel cobaltmanganate, then preparing nano cobaltosic oxide slurry, adding the monocrystal lithium nickel cobalt manganate, lithium salt and an M-containing additive into the slurry, performing mixing, then carrying out spray drying, and performing sintering in an air atmosphere, so as to prepare the nano cobaltosic oxide lithium manganate cathode material. The invention also discloses an application of the positive electrode material in lithium ion batteries. The positive electrode material has excellent first charge-discharge efficiency and high capacity retention rate, and also has excellent cycle performance and safety performance under high voltages of 4.35 V and 4.4 V.

Description

technical field [0001] The invention belongs to the field of lithium-ion battery electrode materials, and relates to a positive electrode material, in particular to a core-shell type high-voltage single-crystal nickel-cobalt lithium manganese oxide positive electrode material and a preparation method and application thereof. Background technique [0002] Nickel cobalt lithium manganese oxide (NCM) ternary cathode material has been extensively studied since it was first reported in 1999. The ternary cathode material combines lithium cobaltate, lithium nickelate, The advantages of the three materials of lithium manganese oxide: it has the characteristics of high capacity of lithium nickel oxide, the high safety performance and low cost of lithium manganate oxide, and the good cycle performance of lithium cobalt oxide. It has become the most rapidly developed cathode material for lithium ion batteries in recent years. . [0003] At present, the ternary positive electrode mater...

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Problems solved by technology

[0003] At present, the ternary positive electrode material of NCM is mainly secondary spherical particle structure. However, the above-mentioned traditional secondary spherical particle structure still has the following problems: 1. The mechanical strength of the particle structure is poor, and it is easy to cause secondary spherical particles during the compaction process. Broken; 2. There are many internal gaps and obvious structural defects. The unit pole piece is easily broken during the rolling process, which causes the battery capacity to attenuate in the later stage, and the compaction density is greatly limited. At the same time, it also increases the difficulty of processing and limits the energy density. 3. The internal pores are large and difficult to cover. The active material is in contact with the electrolyte, and it will be corroded by HF under high temperature conditions, destroying the interface structure, and causing the dissolution of transition metals Ni, Co, and Mn in the electrolyte. Contact with the electrolyte leads to increased side reactions, a large amount of gas is generated, the air pressure of the cell increases, and the battery expands, causing serious safety hazards; 4. There are many surface defects on the particles, and side reactions are prone to occur

However, studies have shown that single crystal nickel-cobalt-manganese ternary cathode materials still have problems such as low initial charge and discharge efficiency, serious capacity loss, and cycle performance under high voltage (≥4.35V) needs to be further improved.

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