A BESS semi-solid refers to a Battery Energy Storage System (BESS) that uses semi-solid-state batteries, an advanced battery technology featuring a gel-like electrolyte, offering a bridge between liquid electrolyte Li-ion batteries and all-solid-state batteries, promising higher energy density, enhanced safety, and potentially lower costs for large-scale grid storage. These systems are used for grid stabilization, peak shaving, and renewable integration, with significant projects recently deployed in China showcasing their viability.