Influencing factors of low- and high-temperature behavior of Co-doped Zn^sub 2^SnO^sub 4^–graphene–carbon nanocomposite as anode material for lithium-ion batteries

Zn2SnO4-based anode materials have recently attracted considerable attention due to their high capacity and low price for lithium-ion batteries. However, their performance is affected by temperature and temperature-dependent characters have not been investigated sufficiently. In this regard, we tested the electrochemistry performance of Co-doped Zn2SnO4–graphene–carbon (Co–ZTO–G–C) nanocomposite anode at various temperatures (− 25, 25 and 60 °C) and analyzed the main limitations and improvements of its low- and high-temperature behavior. Cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) results demonstrated that severe concentration polarization, the absence of Zn2SnO4/Zn(Sn) redox couple and large charge-transfer resistance Rct limited its low-temperature performance. Further electrochemical performance analysis indicated that the doped Co could effectively decrease Rct of the nanocomposite and improve its capacity at low temperature. It also suggested that graphene and carbon layer contributed to maintaining its capacity during high-temperature cycles. Field emission scanning electron microscopy (FESEM) and X-ray diffraction (XRD) results revealed that the performance degeneration of the nanocomposite at elevated temperature was mainly attributed to severe volume expansion/contraction of Zn2SnO4 nanoparticles and destruction of Zn2SnO4 cubic structure. The XRD results also showed that the cubic structures of Zn2SnO4 at all temperatures were destroyed after cycling, which led to cyclic performance degeneration of the Co–ZTO–G–C nanocomposite.