Coralline glassy lithium phosphate-coated LiFePO₄ cathodes with improved power capability for lithium ion batteries

Novel coralline glassy lithium phosphate-coated LiFePO₄ cathodes successfully prepared by radio frequency magnetron sputtering have been studied in lithium ion batteries. These coated LiFePO₄ show higher reversible capacity, stable cycle performance, and improved power capability compared to the bare one. These favorable properties are considered to be attributed to the good conductivity and stability of the glassy lithium phosphate coating. The amorphous nature of the coating reduces the anisotropy of the surface properties of LiFePO₄ electrode and enhances the Li ⁺ ionic diffusion into the LiFePO₄. The glassy lithium phosphate is an effective Li⁺ conductor, which increases the ionic and electronic transport on the surface and into the bulk of LiFePO₄ electrode, extends the electroactive zone, and facilitates the transfer kinetics. It is also a stable Li-excess material, which provides an extra lithium capacity and maintains the electrode structural integrality. Radio frequency sputtering coating of stable Li⁺ conductors on the surface of nanosized LiFePO₄ is an attractive way to improve its power capability, and these specific LiFePO₄ cathodes have great potential for application in high-power lithium ion batteries.