Electrospun C/GeO2 paper-like electrodes for flexible Li-ion batteries

Carbon/germanium dioxide (C/GeO2) paper-like self-supporting membranes to be used as binder- and collector-free anodes in flexible Li-ion batteries (LIBs) are synthesised via electrospinning (ES) followed by stabilisation and carbonisation heat treatments. Carbonisation is operated at relatively low temperature (550 °C) in order to keep high nitrogen concentration in the carbonaceous fibre network, which is claimed to be beneficial for Li-ion storage. Regardless of the germanium load in the spinnable solution (2.50-4.25 wt%), α-quartz GeO2 nanoparticles (NPs) encapsulated in highly N-doped (10-16 at%) C fibres are produced. The size of the oxide NPs and the fibre diameter increase with increasing germanium load. Based on the results of the compositional analysis, the specific capacities of the composite fibres are expected to range between 590 and 780 mAh/g. Preliminary results of half-cell tests substantially confirm the expectations, with Coulombic efficiencies of 92-96% at the second charge/discharge cycle.