Cycling Stability of Lithium-Ion Batteries Based on Fe-Ti-Doped LiNi_0.5 Mn_1.5 O₄ Cathodes, Graphite Anodes, and the...

This study addresses the improved cycling stability of Li-ion batteries based on Fe-Ti-doped LiNi_0.5 Mn_1.5 O₄ (LNMO) high-voltage cathode active material and graphite anodes. By using 1 wt% Li₃ PO₄ as cathode additive, over 90% capacity retention for 1000 charge-discharge cycles and remaining capacities of 109 mAh g^-1 are reached in a cell with an areal capacity of 2.3 mAh cm^{- 2} (potential range: 3.5-4.9 V). Cells without the additive, in contrast, suffer from accelerated capacity loss and increase polarization, resulting in capacity retention of only 78% over 1000 cycles. An electrolyte consisting of ethylene carbonate, dimethyl carbonate, and LiPF₆ is used without additional additives. The significantly improved cycling stability of the full cells is mainly due to two factors, namely, the low Mn^III content of the Fe-Ti-doped LNMO active material and the use of the cathode-additive Li₃ PO₄ . Crystalline Li₃ PO₄ yields a drastic reduction of transition metal deposition on the graphite anode and prevents Li loss and the propagation of cell polarization. Li₃ PO₄ is added to the cathode slurry that makes it a very simple and scalable process, first reported herein. The positive effects of crystalline Li₃ PO₄ as electrode additive, however, should apply to other cell chemistries as well.