Synthesis of Li1.147K0.026Mn0.582Ni0.25O2 cathode material with high rate cyclic performance and the application to lithium-ion full cells

Li1.147K0.026Mn0.582Ni0.25O2 (LKMNO) sample is successfully prepared by doping K+ ions into Li slab without changing the original structure of Li1.167Mn0.575Ni0.25O2 (LMNO). LKMNO sample delivers the capacities of 160.2 and 135.1 mAh g(-1) at 1 and 5 C rates, respectively, but LMNO sample only delivers 135.1 and 0 mAh g(-1). After 100 cycles at 1 C rate, LMNO and LKMNO samples respectively remain 67.4% and 93.0% of their initial capacities. The effects of K+ doping on the relationship between the charging-discharging process and phase change are detailed studied by the incremental capacity curves (dQ/dV) at the various cycles. K+ doping in LKMNO sample plays an essential role in rate performance and cyclic performance, because it effectively hinders the formation of spinel structure and stabilizes the host layered structure. Considering the irreversible extraction of Li and O from the Li2MnO3 region occurred beyond 4.6 V, after the charging/discharging are collected for 1-5 cycles at 2.5-4.9 V and 6-300 cycles at 2.5-4.6 V, LKMNO sample further reveals a remarkable improvement in cycling performance. In the full cell state (pouch cell), the discharge capacity of LKMNO is 194.6 and 115.4 mAh g(-1) at 0.1 and 1 C rates, respectively, which are much higher than 175.5 and 79.7 mAh g(-1) of LMNO sample. The capacity retention of LMNO and LKMNO samples is respective 48.8% and 74.9% of their initial capacity after 100 cycles. (C) 2019 Elsevier B.V. All rights reserved.