Monday, 10 October 2022
Lithium (Li) metal batteries are expected to develop faster to cater to the growth of the sustainable consumer electronic market. Due to its high specific capacity (3860 mAh g−1) and a low redox potential (−3.04 V vs H2/H+), Li metal is preferred to achieve high-capacity batteries. However, the Li metal is unstable and generates exothermic reactions with liquid electrolytes. The growth of Li dendrites on the surface of Li is another issue that jeopardizes the safety standards of the battery. Solid-state electrolytes can be a better alternative to achieving stable and safer Li metal batteries. Oxygen deficient metal oxides such as Molybdenum trioxide (MoO3) can act as a source of Lewis acid sites to dissociate the LiTFSI salt. We have modified a PEO-based solid-state electrolyte for stable Li-metal batteries. Locally designed MoO3-x nanobelts (MNBs) were utilized as passive fillers in PEO/LiTFSI matrix. The oxygen vacancies act like Lewis acid sites and interact with LiTFSI salt. Upon interaction, the oxygen vacancies react with TFSI− anions and separate the Li+ cations. This phenomenon enhances the number of free Li+ ions and the ionic conductivity of the PEO/LiTFSI matrix. The 5% of MNBs in PEO/LiTFSI (MPL-SPE) offered high Li-ion conductivity of 4.28 × 10−4 S cm−1 at 600C. The enhanced ionic conductivity and shorter diffusion pathways for Li+ ions result in a lower overpotential of the Li/Li symmetrical cell performance. In Figure 1a, the MPL-SPE cell shows reduced overpotential (~40mV) than the cell with PEO/LiTFSI matrix (~85mV) at a current density of 0.2mA cm-2 (Figure 1a). The as-designed MPL-SPE had attached to the cathode by using the hard press method. The cathode supported ML-SPE reduces the interfacial resistance between the cathode and solid electrolyte. The electrochemical performance of the all-solid-state Li battery with LiFePO4 (LFP) cathode attached with MPL-SPE demonstrated superior initial specific capacity of ~115 mAh g-1 and ~140 mAh g-1 at the 50th cycle at a 0.5C rate with ~100% coulombic efficiency (Figure 1b).
