Improved high-voltage performance of FePO4-coated LiCoO2 by microwave-assisted hydrothermal method

• Hot spots are introduced on LiCoO2 surface by selective heating of microwave.
• Hot spots promote heterogeneous nucleation of FePO4 only on the LiCoO2 surface.
• Conformal and densely-packed FePO4 coating layer is found only on LiCoO2 surface.
• FePO4-coated LiCoO2 exhibits excellent cycle stability with charging voltage of 4.7 V.

The generation of hot spots on the surface of LiCoO2 by microwave-induced selective heating is shown to facilitate a uniform hydrothermal coating of FePO4. This is achieved by heterogeneous nucleation of FePO4 in the bulk solution, with the resulting coating layer found to be highly conformal. Furthermore, morphology of the LiCoO2 is preserved with no aggregation of the FePO4 nanoparticles. This FePO4-coated LiCoO2 exhibits markedly improved capacity retention of over 92% under a high charge voltage cutoff of 4.7 V, even after 50 cycles.