Development of LiNi_0.5 Mn_1.5 O₄ / Li ₄ Ti₅ O₁₂ system with long cycle life

The electrochemical performance of LiNi_0.5 Mn_1.5 O₄ (LNMO) / Li₄ Ti₅ O₁₂ (LTO) cells with different designs (positive-electrode-limited, negative-electrode-limited, and positive/negative capacity ratio of ≈1) was investigated at different temperatures and current densities. Half-cells based on either LNMO/Li or LTO/Li exhibited an outstanding rate capability. When both electrodes were combined in a full cell configuration, the LNMO/LTO cells showed an excellent rate capability, with 86% discharge capacity retention at the 10C rate. Of the three designs, the negative-limited full cell showed the best cycling performance when discharged at the 2C rate in tests at room temperature: 98% capacity retention after 1000 cycles. The negative-limited full cell also exhibited excellent cycling characteristics in tests at 55°C: 95% discharge capacity retention after 200 cycles. These results clearly demonstrate that the LNMO/LTO system with a negative-limited design is attractive for plug-in hybrid electric vehicles, where a long cycle life and a reasonable power are needed.