Constructing durable carbon layer on LiMn_0.8Fe_0.2PO₄ with superior long-term cycling performance for lithium-ion battery

Highlights: • The durable carbon layer is constructed by CVD coating method, successfully. • Mn dissolution of treated cathode material is effectively suppressed. • Long-term cycling performance of the treated cathode material is improved. • The rate capability of the treated material is enhanced. - Abstract: LiMn_0.8Fe_0.2PO₄ is becoming one of the most promising cathode materials for lithium ion batteries. However, the capacity suffers from a loss during long-term cycling, which is directly associated with Mn dissolution due to the disproportionation reaction of Mn³⁺. Here, we report a chemical vapor deposition (CVD) approach to modify LiMn_0.8Fe_0.2PO₄ particles with carbon so as to minimize Mn dissolution from cathode. The deposited carbon layer not only protects LiMn_0.8Fe_0.2PO₄ cathode from electrolyte corrosion, but also enhances the electronic/ionic conductivity owing to its higher graphitize degree. As a consequence, the electrochemical performances have a significant improvement. The capacity retention achieves 96% after 450 cycles at 1 C at room temperature (25 °C). Even at elevated temperature (55 °C), the capacity retention also reaches at 97 % after 50 cycles at 1 C rate, which is much higher than that of untreated sample (89%). Hence, the cathode material based on LiMn_0.8Fe_0.2PO₄ encapsulated with durable carbon by CVD method represents a promising strategy for developing its long-term cycling performance through suppressing Manganese dissolution.