Micron-sized monocrystalline LiNi_1/3Co_1/3Mn_1/3O₂ is proposed for the first time to improve the volumetric-energy-density of lithium-ion batteries.

In this paper, a NASICON-type Li_1.3Al_0.3Ti_1.7(PO₄)₃ (LATP)/Li_1.3Al_0.3Ge_1.7(PO₄)₃ (LAGP) bi-layer structured solid state electrolyte was successfully prepared via a simple dry pressing and post-calcination method. By adjusting the sintering temperature for LAGP starting materials, a dense and smooth LATP/LAGP double-layer solid state electrolyte with no defects was obtained. This electrolyte sample exhibits a high electrical conductivity of 3.4 × 10⁻⁴ S cm⁻¹ and a negligible electronic conductivity of 9.6 × 10⁻⁹ S cm⁻¹ at room temperature. In addition, the LATP/LAGP electrolyte also shows an excellent stability in air as well as chemical stability against Li. Moreover, an assembled LiFePO₄/LATP–LAGP/Li coin-type battery employing LATP/LAGP as the solid state electrolyte can be suitably charged and discharged at a current rate of 0.1C at room temperature, and its low charge–discharge capacities are mainly attributed to the high electrolyte/electrode interfacial resistance of the cell. These results suggest that the LATP/LAGP bi-layer electrolyte can be an alternative electrolyte for all-solid-state lithium-ion batteries.