Cycling stability of lithium-ion batteries based on Fe-Ti doped LiNi0.5Mn1.5O4 cathodes, graphite anodes and the cathode additive Li3PO4

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 were reached in a cells with an areal capacity of 2.3 mAh∙cm-² (potential range: 3.5 V - 4.9 V). Cells without the additive, in contrast, suffered from accelerated capacity loss and increased polarization, resulting in capacity retention of only 78% over 1000 cycles. An electrolyte consisting of ethylene carbonate, dimethyl carbonate and LiPF6 was 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 was added to the cathode slurry which makes it a very simple and scalable process, firstly reported herein. The positive effects of crystalline Li3PO4 as electrode additive, however, should apply to other cell chemistries as well.