Morphology control of lithium peroxide using Pd₃Co as an additive in aprotic Li-O₂ batteries

During discharge in aprotic Li-O₂batteries, lithium peroxide (Li₂O₂) can be formed by a surface- or solution-mediated route. In the surface-mediated process, a Li₂O₂film is formed electrochemically on the cathode surface, leading to low capacity and rate capability. In contrast, in high donor or acceptor number electrolyte systems, Li₂O₂toroids are formed by solution-mediated growth through a disproportionation reaction, resulting in high capacity and rate capability. However, during charging, high donor or acceptor number solvents cause poor rechargeability because of the high crystallinity of Li₂O₂toroids and byproduct formation. Therefore, controlling the size of Li₂O₂in a solution-mediated discharge process is the key to the development of Li-O₂batteries with high capacity and good rechargeability. We demonstrate the application of Pd₃Co nanoparticles to enhance the rechargeability of a Li-O₂cell in a solution-mediated process. Scanning electron microscopy and X-ray diffraction studies indicate that the Li₂O₂particles formed during discharge are small and the decomposition of the reaction products is reversible. A cell fabricated with Pd₃Co nanoparticles exhibits a lower overpotential than the one without the nanoparticles. The additive may provide nucleation sites for Li₂O₂particles, leading to enhanced rechargeability and appropriate capacity in a solution-mediated process for Li-O₂batteries.