1 research outputs found
Use of Nano Seed Crystals To Control Peroxide Morphology in a Nonaqueous Li–O<sub>2</sub> Battery
The high theoretical energy density
of Li–O<sub>2</sub> batteries
as required for electrification of transport has pushed Li–O<sub>2</sub> research to the forefront. The poor cyclability of this system
due to incomplete Li<sub>2</sub>O<sub>2</sub> oxidation is one of
the major hurdles to be crossed if it is ever to deliver a high reversible
energy density. Here we present the use of nano seed crystallites
to control the size and morphology of the Li<sub>2</sub>O<sub>2</sub> crystals. The evolution of the Li<sub>2</sub>O<sub>2</sub> lattice
parameters during <i>operando</i> X-ray diffraction demonstrates
that the hexagonal NiO nanoparticles added to the activated carbon
electrode act as seed crystals for equiaxed growth of Li<sub>2</sub>O<sub>2</sub>, which is confirmed by scanning electron microscopy
energy-dispersive X-ray spectroscopy (SEM-EDX) elemental maps also
showing preferential formation of Li<sub>2</sub>O<sub>2</sub> on the
NiO surface. Even small amounts of NiO (∼5 wt %) particles
act as preferential sites for Li<sub>2</sub>O<sub>2</sub> nucleation,
effectively reducing the average size of the primary Li<sub>2</sub>O<sub>2</sub> crystallites and promoting crystalline growth. This
is supported by first principle calculations, which predict a low
interfacial energy for the formation of NiO–Li<sub>2</sub>O<sub>2</sub> interfaces. The eventual cell failure appears to be the consequence
of electrolyte side reactions, indicating the necessity of more stable
electrolytes. The demonstrated control of the Li<sub>2</sub>O<sub>2</sub> crystallite growth by the rational selection of appropriate
nano seed crystals appears to be a promising strategy to improve the
reversibility of Li–air electrodes