Cycling Stability of Lithium-Ion Batteries Based on Fe-Ti-Doped LiNi 0.5 Mn 1.5 O 4 Cathodes, Graphite Anodes, and the Cathode-Additive Li 3 PO 4 .

This study addresses the improved cycling stability of Li-ion batteries based on Fe-Ti-doped LiNi 0.5 Mn 1.5 O 4 (LNMO) high-voltage cathode active material and graphite anodes. By using 1 wt% Li 3 PO 4 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 LiPF 6 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 Li 3 PO 4 . Crystalline Li 3 PO 4 yields a drastic reduction of transition metal deposition on the graphite anode and prevents Li loss and the propagation of cell polarization. Li 3 PO 4 is added to the cathode slurry that makes it a very simple and scalable process, first reported herein. The positive effects of crystalline Li 3 PO 4 as electrode additive, however, should apply to other cell chemistries as well.