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

Abstract

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.