Layered composite oxide coated positive electrode material and preparation method and application thereof

Abstract

The invention relates to a layered composite oxide coated positive electrode material as well as a preparation method and application thereof. The preparation method comprises the following steps: uniformly mixing cobalt salt and M salt or oxide according to a ratio, conducting sintering to obtain a bulk phase material precursor, mixing the bulk phase material precursor with lithium salt and an additive according to a ratio, conducting sintering at a high temperature, and conducting crushing to obtain gradient-doped modified lithium cobalt oxide; ultrasonically dispersing layered protonated titanate nanosheets in a uniformly dispersed dispersion liquid containing a metal oxide, transferring the dispersion liquid to a high-pressure reaction kettle for reaction, and conducting washing after separation to obtain intercalated layered titanate; carrying out dispersion and ultrasonic treatment on the intercalated layered titanate to obtain a stripped intercalated layered titanate nanosheet colloidal solution; and adding the modified lithium cobalt oxide into the intercalated layered titanate nanosheet colloidal solution, carrying out rotary evaporation to remove the solvent, carrying out vacuum drying, and carrying out heat treatment on the dried material to form the intercalated layered titanate nanosheet-coated modified lithium cobalt oxide layered composite oxide-coated positive electrode material.

Description

technical field [0001] The invention relates to the field of material technology, in particular to a layered composite oxide-coated positive electrode material and a preparation method and application thereof. Background technique [0002] Lithium cobalt oxide (LiCoO 2 ), as the earliest commercial lithium-ion battery cathode material, has achieved great success in the field of consumer electronics, but from 1990 to 2010, lithium cobalt oxide material actually only exerted about half of its capacity, and the cut-off voltage was conventional At 4.2V, the amount of Li removed is only about 0.5, while its theoretical capacity after complete delithiation can reach 274mAh / g. [0003] If you want to make lithium cobalt oxide play a higher capacity, you can only increase the charge cut-off voltage, but too high charge voltage will lead to the dissolution of Co element and LiCoO 2 Irreversible phase transitions of materials. In view of this, the industry proposes to improve lithi...

AI Technical Summary

Problems solved by technology

However, with the increase of the cut-off voltage, a series of problems need to be solved urgently: 1. The side reaction between the material and the electrolyte becomes more severe, especially when the state of charge (SOC) is high, the electrolyte continues to decompose, The positive electrode electrolyte interfacial phase (CEI) is formed, which is prone to cyclic diving; 2. Oxygen participates in charge compensation, resulting in structural changes and accelerating the formation of CEI; 3. The structural changes on the surface of materials, including cracking, etc., from layered The structure is converted to a spinel structure with no electrochemical activity and a rock-salt (Rock-Salt) structure; 4. The new phase transition platform (4.5Vvs.Li) under high voltage releases more lithium ions, and the capacity increases, O3→H1 The -3→O1 phase transition also leads to the delithiation material Li 1-x CoO 2 The structure is more likely to collapse, an irreversible phase transition occurs, and the cycle life is greatly reduced

[0007] However, in the actual technical solution, after using the layered or spinel structure lithium nickel manganese oxide material on the surface, although the high voltage performance of the lithium cobalt oxide material is improved to a certain extent, it can meet the full range of 4.35-4.40V. battery system, but it cannot solve the corrosion of the cladding layer by HF. Due to the intensified corrosion of materials by HF at high temperatures, the cycle performance of materials in existing technical solutions is still poor at high temperatures; at the same time, this type of technology cannot overcome high voltage Cyclic Stability Issues at (≥4.5V)

The method of coating with inert materials can reduce side reactions and inhibit the formation of CEI, but since the coating layer has no electrochemically active lithium, the capacity of the material will be significantly reduced, and the cycle performance of the full battery 4.6V system is also poor.

For the solution using trace doping, the effect obtained so far can only cover the system below 4.6V, and it is not very helpful for the stability of the structure of lithium cobaltate cycle above 4.6V, which is far from the actual industrial application requirements. a certain distance

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