Low Temperature Sintering Al-B Doped-LLZO for All-Solid-State Lithium Battery

This research synthesizes a double Al-B doped LLZO following a composition of Li7+0.5xLa1.14Al1.43xB0.5xZr2-3xO12-δ through a solid-state reaction. The materials were sintered at a low temperature of 900 °C, giving an advantage in reducing Li loss. The material was analyzed to understand the phase content, the crystal structure and cell parameters, the surface morphology, the impedance, the electrical conductivity, and the activation energy for ionic migration. As a result, the Al-B doped-LLZO with x composition of 0.3 (Li7.15La1.14Al0.429B0.15Zr1.1O12-) and ball milling time of 120 h, LLZBAO(0.3)120 h, provides the highest ionic conductivity of 6.898×10–4 Scm–1 at room temperature, and it increases as the temperature increases confirming activation energy of 0.135 eV. A prototype of LCO-LLZBAO(0.3)120h-Li metal battery was produced and tested to investigate the solid electrolyte performance. A cyclic voltammetry analysis confirms a quasi-reversible reaction involving extraction-insertion of Li ions into LiCoO2. However, the excess capacity and a long plateau at low voltage also indicate the reduced Li+ into zero valent-metal, which is poorly reversible, causing the battery capacity to decrease and become stable after 20 cycles.