Electrochemical investigation of Li-excess layered oxide cathode materials/mesocarbon microbead in 18650 batteries

The electrochemical performance of the 18650 lithium-ion batteries for layered Li-excess oxide Li1.144Ni0.136Co0.136Mn0.544O2 (LNCMO) cathode material and mesocarbon microbead (MCMB) anode material is investigated. The battery shows an excellent rate capability with the capacity of 227 mAh g−1 at 8 C-rate (the cut-off voltage is 4.5 V). Furthermore, it exhibits excellent cycle performance that the capacity retention over 300 cycles in the voltage ranges of 2.5-4.5 V (vs. MCMB) and at 0.2 C-rate is about 85%. Although the medium voltage of the battery greatly reduces during the first 30 cycles, it keeps stable in the following cycles. The mechanisms of the capacity fade and voltage decay are also studied based on energy dispersive spectrometry, X-ray photoelectron spectroscopy, charge-discharge curves, and dQ/dV plots.