Electrochemical properties of the mesocarbon microbeads (MCMBs) in an all-solid-state electrochemical cell by use of the amorphous solid electrolyte Li3PS4

Abstract

Electrochemical properties of the mesocarbon microbeads (MCMBs) were investigated as anode active materials for an all-solid-state cell in which amorphous Li3PS4(a-Li3PS4) was used as solid electrolytes and Li-In alloy was used as a counter electrode. The amount of Li+ions that were inserted into the MCMBs denoted as x in the notation LixC6(0 < × < 1). X-ray diffraction measurements suggested that Li+ions were inserted into the disordered portions of MCMBs at the initial reaction stage with the composition range of 0 < × < 0.13. After the initial reaction stage, Li+ions were intercalated into the graphite layers of MCMBs in the composition range of 0.13 < × < 0.91. The Li+ions inserted into the disordered portions of MCMBs could not be extracted in the discharge process and then caused the irreversible capacity of the first charge-discharge cycle. On the other hand, Li+ions that were intercalated into the graphite layers can be reversibly deintercalated in the composition range of 0.13 < × < 0.91. The charge-discharge capacity of the MCMBs was gradually decreased with an increase in the cycle number. Raman spectroscopy suggested that the capacity fading during the charge-discharge cycles would be caused by the deterioration of the MCMBs' crystallinity.