Cycling Stability of Lithium-Ion Batteries Based on Fe–Ti-Doped LiNi0.5Mn1.5O4 Cathodes, Graphite Anodes, and the Cathode-Additive Li3PO4

Abstract

This study addresses the improved cycling stability of Li-ion batteries based on Fe–Ti-doped LiNi0.5Mn1.5O4 (LNMO) high-voltage cathode active material and graphite anodes. By using 1 wt% Li3PO4 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 MnIII content of the Fe–Ti-doped LNMO active material and the use of the cathode-additive Li3PO4. Crystalline Li3PO4 yields a drastic reduction of transition metal deposition on the graphite anode and prevents Li loss and the propagation of cell polarization. Li3PO4 is added to the cathode slurry that makes it a very simple and scalable process, first reported herein. The positive effects of crystalline Li3PO4 as electrode additive, however, should apply to other cell chemistries as well.