High Rate Performance of Dual-Substituted LiFePO₄ Based on Controlling Metastable Intermediate Phase

High rate capability is one of the most important properties in Li-ion batteries for electric vehicle and/or energy grid use. Herein, a high-power electrode material consisting of dual-substituted LiFePO4 by zirconium and silicon, Li­(Fe0.95Zr0.05)­(P0.9Si0.1)­O4, was developed as it exhibits small lattice volume change between Li-rich and Li-poor phases. The dual-substituted cathode exhibited 1.1–4.4 times larger charge/discharge capacities for upper 10 C rates than that of the undoped material. Time-resolved XRD measurements at the high rate of 10 C revealed the formation of a metastable intermediate phase during the Li intercalation/deintercalation processes which triggers the continuous phase transition in Li­(Fe0.95Zr0.05)­(P0.9Si0.1)­O4 with moderation of the lattice mismatch. Controlling the lattice volume change between the initial and end phase of the intercalation materials is key to achieving high rate capabilities