LiCoO2 cathode surface modification with optimally structured Li3PO4 for outstanding high-voltage cycling performance

While researchers often adopt a higher operating voltage to further enlarge the actual specific capacity of LCO to expand its application scope and market share, this triggers some more intractable issues in that the capacity decays obviously and causes the attendant problem of safety. Li₃PO₄ shows the advantage of increasing the energy density of lithium-ion batteries due to its characteristic ionic conduction when coated onto an LCO cathode. Enhancing the conductivity of cathode materials is the key factor in the success of raising their operating voltage to meet emerging market demands. Here, we report a direct facile coprecipitation method for coating crystalized Li₃PO₄ onto an LCO surface that enables balancing the ionic conductivity and chemical stability. LCO@ Li₃PO₄ crystalline lithium phosphate can generate superior electrical contact with the cathode material for high capacity and effectively stabilize the cathode surface by reducing the formation of SEI/CEI to prolong the cycle life. The optimized LP-3 cathode can deliver a high initial discharge capacity of 181 mA h g^-1 at 0.5C, with a capacity retention of 75% after 200 cycles. This study introduces a competitive strategy to produce a high-voltage LCO cathode via the most viable and economical method.