Fast-Rate Capable Electrode Material with Higher Energy Density than LiFePO4: 4.2V LiVPO4F Synthesized by Scalable Single-Step Solid-State Reaction

Use of compounds that contain fluorine (F) as electrode materials in lithium ion batteries has been considered, but synthesizing single-phase samples of these compounds is a difficult task. Here, it is demonstrated that a simple scalable single-step solid-state process with additional fluorine source can obtain highly pure LiVPO4F. The resulting material with submicron particles achieves very high rate capability ≈100 mAh g−1 at 60 C-rate (1-min discharge) and even at 200 C-rate (18 s discharge). It retains superior capacity, ≈120 mAh g−1 at 10 C charge/10 C discharge rate (6-min) for 500 cycles with >95% retention efficiency. Furthermore, LiVPO4F shows low polarization even at high rates leading to higher operating potential >3.45 V (≈3.6 V at 60 C-rate), so it achieves high energy density. It is demonstrated for the first time that highly pure LiVPO4F can achieve high power capability comparable to LiFePO4 and much higher energy density (≈521 Wh g−1 at 20 C-rate) than LiFePO4 even without nanostructured particles. LiVPO4F can be a real substitute of LiFePO4.