High-capacity Li2S–nanocarbon composite electrode for all-solid-state rechargeable lithium batteries

All-solid-state lithium secondary batteries with Li2S active materials and sulfide-based solid electrolytes (SEs) were fabricated and the Li2S electrodes were characterized. Li2S–nanocarbon composite electrodes were prepared by hand grinding and mechanical milling. Mechanical milling of a mixture of Li2S, acetylene black (AB), and Li2S–P2S5 SE enhanced the reversible capacity of the all-solid-state cells. Cross-sectional transmission electron microscopy images and electron-energy-loss spectroscopy maps revealed the formation of favorable contacts among Li2S, AB, and SE. Nanocomposites consisting of approximately 500 nm Li2S particles and AB and SE particles were well-dispersed both before and after charge–discharge cycles. The effect of reducing the particle size of the Li2S active material in the composite electrodes on cell performance was investigated. Cells containing milled Li2S with small particle sizes exhibited a charge capacity of about 1000 mA h g−1 under 0.064 mA cm−2 at 25 °C and they were charged and discharged at a high current density of 6.4 mA cm−2 (3.5 C). To improve the reversible capacity and the rate performance of all-solid-state cells, it is important to realize intimate contact among electrode components and reduce the particle size of active materials and composite electrodes by mechanical milling.