Ti3SiC2 modified Li3V2(PO4)3/C cathode materials with simultaneous improvement of electronic and ionic conductivities for lithium ion batteries

• Both electronic and ionic conductivities are increased simultaneously with TSC.
• A continuous conductive network is formed via a “point-to-plane” conducting mode.
• A model of double-decker bus is proposed to understand the improvements.

Li3V2(PO4)3/C (LVP/C) is synthesized by an improved sol–gel method and modified with various amounts of Ti3SiC2 (TSC). It is found that both electronic and ionic conductivities are increased simultaneously with one single addition due to the nanolaminated structure of TSC. TSC not only constitutes continuous electron pathways via a “point-to-plane” conducting mode, which improves the electronic conductivity, but also enhances lithium ionic conductivity. Therefore, electrochemical performances of TSC-modified samples are significantly improved. TSC-modified samples exhibit improved cyclic stability, rate performance and initial discharge capacity at high rates. An extremely low charge transfer resistance (5.57 Ω) and significantly reduced polarization were obtained. The 4 wt% TSC-modified LVP/C sample exhibits the best electrochemical performances in the voltage range of 3.0–4.8 V, especially at high rates. It shows initial discharge capacity of 114.5 mAh g−1 at 10 C, while the discharge capacity of the pristine sample is only 37.2 mAh g−1 at the same rate. The 4 wt% TSC-modified LVP/C sample holds capacity retention of 88.5% at 10 C after 200 cycles, which is much higher than that of pristine one. A model of double-decker bus is proposed to understand the significant improvements of both electronic and ionic conductivities.

In this work, we firstly modify Li3V2(PO4)3/C with Ti3SiC2. Nanolaminated Ti3SiC2 performs as a double-decker bus carrying Li+ ions and electrons on its two floors separately, achieving a simultaneous increase of both electronic and ionic conductivities with high capacity. The 4 wt% Ti3SiC2-modified Li3V2(PO4)3/C sample exhibits best cycle performances in the voltage range of 3.0–4.8 V and shows the highest capacity retention of 65.4% after the 60th cycle at 10 C for instance. But the capacity retention of the pristine one is only 24.4% as a comparison. Besides, the 4 wt% Ti3SiC2-modified Li3V2(PO4)3/C electrode is able to retrieve its reversible capacity of 137.9 mAh g−1 (91.2% recovery) when re-cycled at 0.2 C, showing a good stability after 60 cycles at various rates.Figure optionsDownload as PowerPoint slide