A composite lithium supplement and a preparation method thereof, a positive electrode sheet, and a lithium ion battery

Abstract

This invention provides a composite lithium replenishing agent, its preparation method, a positive electrode sheet, and a lithium-ion battery. The composite lithium replenishing agent comprises Li₂C₂O₄, elemental boron (B), and a conductive support, wherein elemental boron is dispersed at the nanoscale in the Li₂C₂O₄ crystal lattice. The preparation method includes: mixing lithium metal powder and LiB(C₂O₄)₂ at a molar ratio of (2.8-3.2):1, and performing a first mechanical ball milling treatment under inert gas protection to induce an in-situ chemical reaction between the two to generate a nanocomposite of Li₂C₂O₄ and elemental boron; then mixing the obtained nanocomposite with the conductive support and performing a second mechanical ball milling treatment to form a nanoscale dispersed composite lithium replenishing agent. This invention achieves atomic / nanoscale dispersion of elemental B in the Li2C2O4 lattice through in-situ reaction, obtaining a unique microstructure. This allows the composite lithium replenishing agent to possess low decomposition voltage (<4.3V), high lithium replenishing capacity (>400mAh / g), no gas generation characteristics, and excellent cycle stability. Furthermore, the particle size D90≤1μm makes it more suitable for existing electrode production lines.

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