The origin of stability and high Co(2+/3+) redox utilization for FePO(4)-coated LiCo(0.90)Ti(0.05)PO(4)/MWCNT nanocomposites for 5 V class lithium ion batteries

Highly-dispersed 10 wt% FePO(4) (FP)-coated LiCo(0.90)Ti(0.05)PO(4) (LCTP) was successfully synthesized within a multiwalled carbon nanotube matrix via our original ultracentrifugation process. 10 wt% FP-coated LCTP sample showed a higher discharge capacity of 116 mA h g(−1) together with stable cycle performance over 99% of capacity retention at the 100(th) cycle in high voltage. A combination of TEM, XRD, XPS, and XAFS analyses suggests that (i) Ti(4+)-substitution increases the utilization of Co redox (capacity increase) in LCP crystals by suppressing the Co(3)O(4) formation and creating the vacancies in Co sites, and (ii) the FP-coating brought about the Fe enrichment of the surface of LCTP which prevents an irreversible crystal structure change and electrolyte decomposition during cycling, resulting in the stable cycle performance.