Li2CO3 induced stable SEI formation: An efficient strategy to boost reversibility and cyclability of Li storage in SnO2 anodes

The unstable interfaces between a SnO2 anode and an electrolyte in a Li-ion battery dramatically impair the reversibility and cycling stability of lithiation and delithiation, resulting in low roundtrip Coulombic efficiency (CE) and fast capacity decay of SnO2-based anode materials. Herein, a simple strategy of modifying the solid electrolyte interphase (SEI) is developed to enhance the interfacial stability and lithium storage reversibility of SnO2 by compositing it with graphite (G) and an inorganic component of the SEI, such as Li2CO3 or LiF, which results in the SnO2-Li2CO3/G and SnO2-LiF/G composite anodes with high CEs, large capacities and long cycle lives. Specifically, the SnO2-Li2CO3/G composite anode exhibits an average initial CE of 79.6%, a stable reversible capacity of 927.5 mA h g−1 at a current rate of 0.2 A g−1, and a charge capacity over 1200 mA h g−1 with a CE >99% after 900 cycles at a higher current rate of 1 A g−1. It is revealed that Li2CO3 induces the formation of a dense and stable SEI on SnO2 grains and inhibits the coarsening of nanosized Sn particles generated from the dealloying reaction in the SnO2-Li2CO3/G electrode. Moreover, the CE and cycling stability of other alloying type (Si) and conversion reaction (MnO2 and Fe3O4) anodes can also be greatly promoted by simply milling with Li2CO3. Thus, a universal and simple strategy is developed to achieve highly reversible and stable electrodes for large capacity lithium storage.