Strong MXene-bridged graphene sheets for compact energy storage

High volumetric energy density energy storage devices are needed for many applications ranging from miniaturized electronics to electric vehicles[1,2].Two-dimensional(2D)nanosheets,such as graphene,MoS2,and MXene are great candidates for assembling compact sheets[1–5],as their horizontal stacking can achieve interlayer distances close to the diameter of electrolyte ions[1,6].The electrolyte ions confined between interlayers of those materials significantly improve the pore and porous volume utilization,thus achieving compact energy storage realized by ion desolvation[1].

Boosting the lithium-ion storage performance of perovskite Sr_(x)VO_(3-δ) via Sr cation and O anion deficient engineering

Perovskite SrVO_(3) has been investigated as a promising lithium storage anode where the V cation plays the role of the redox center,combining excellent cycle stability and safe operating potential versus Li metal plating,with limited capacity.Here,we demonstrate the possibility to boost the lithium storage properties,by reducing the non-redox active Sr cation content and fine-tuning the O anion vacancies while maintaining a non-stoichiometric Sr_(x)VO_(3-δ) perovskite structure.Theoretical investigations suggest that Sr vacancy can work as favorable Li^(+) storage sites and preferential transport channels for guest Li^(+) ions,contributing to the increased specific capacity and rate performance.In contrast,inducing O anion vacancy in Sr_(x)VO_(3-δ) can improve rate performance while compromising the specific capacity.Our experimental results confirm the enhancement of specific capacities by fine adjusting the Sr and O vacancies,with a maximum capacity of 444 mAh g^(-1) achieved with Sr_(0.63)VO_(3-δ),which is a 37%increase versus stoichiometric SrVO_(3).Although rich defects have been induced,Sr_(x)VO_(3-δ) electrodes maintain a stable perovskite structure during cycling versus a LiFePO_(4) cathode,and the full-cell could achieve more than 6000 discharge/charge cycles with 80%capacity retention.This result highlights the possibility to use the cation defective-based engineering approach to design high-capacity perovskite oxide anode materials.