Post-mortem studies of mesoporous carbon coated, nanostructured silicon anode of li-ion cell

Lithium-ion batteries (LIBs) have come up as promising devices for energy storage applications because of high energy density, low self-discharge, long cycle life and absence of memory effect, they are endowed with. High energy density LIBs are particularly considered as ideal sources for powering electric vehicles (EV) and hybrid electric vehicles (HEV). Silicon and transition metal oxides are widely pursued anode materials for Li ion cells due to the advantages of high theoretical capacity, environmental friendliness and suitable and safe voltage profile. However, they encounter challenges arising from large volume expansion up to 300% on lithium insertion, poor electrical conductivity and formation of unstable solid electrolyte interface (SEI) layers.1 Efficient working of an ideal Li-ion cell relies on never-ending shuttling of lithium ions during charging and discharging (or lithiation and delithiation) between the electrodes. For ideal performance of the cell, electrodes should retain their structural stability, porosity and conductivity after many cycles of charging and discharging.2 A hierarchical structure of mesoporous carbon as a shell grown around silicon nanoparticles via hydrothermal method is used as anode and is assessed against lithium metal in half-cell configuration. The test cells show an initial discharge capacity of 3102 mAh/g and charge capacity of 2101 mAh/g with initial columbic efficiency (ICE) of 67%. After 5 cycles the capacity retention of the cell is 37%. In the present work, we report assessment of failure mechanism of Li ion cell due to high volume expansion of Si composite anode using post-mortem analysis of the electrode based on FE SEM studies.