Ultralow-strain Ti substituted Mn-vacancy layered oxides with enhanced stability for sodium-ion batteries

Anionic redox reaction(ARR) in layered manganese-based oxide cathodes has been considered as an effective strategy to improve the energy density of sodium-ion batteries.Mn-vacancy layered oxides deliver a high ARR-related capacity with small voltage hysteresis,however,they are limited by rapid capacity degradation and poor rate capability,which arise from inferior structure changes due to repeated redox of lattice oxygen.Herein,redox-inactive Ti^(4+)is introduced to substitute partial Mn^(4+)to form Na_(2) Ti_(0.5)Mn_(2.5)O_7(Na_(4/7)[□_(1/7)Ti_(1/7)Mn_(5/7)]O_(2),□ for Mn vacancies),which can effectively restrain unfavorable interlayer gliding of Na2 Mn307 at high charge voltages,as reflected by an ultralow-strain volume variation of 0.11%.There is no irreversible O_(2) evolution observed in Na_(2) Ti_(0.5)Mn_(2.5)O_7 upon charging,which stabilizes the lattice oxygen and ensures the overall structural stability.It exhibits increased capacity retention of 79.1% after 60 cycles in Na_(2) Ti_(0.5)Mn_(2.5)O_7(17.1% in Na_(2) Mn_(3) O_7) and good rate capability(92.1 mAh g^(-1) at 0.5 A g^(-1)).This investigation provides new insights into designing high-performance cathode materials with reversible ARR and structural stability for SIBs.

Solvation chemistry of electrolytes for stable anodes of lithium metal batteries

Lithium metal batteries(LMBs)have gained increasing attention owing to high energy density for large-scale energy storage applications.However,serious side reactions between Li anodes and organic electrolytes lead to low Columbic efficiency and Li dendrites.Although progress has been achieved in constructing electrode structures,the interfacial instability of Li anodes is still challenging.Solvation chemistry significantly affects the electrolyte properties and interfacial reactions,but the reaction mechanisms and the roles of each component in electrolytes are still vague.This review spotlights the recent development of electrolyte regulation with concentration and composition adjustments,aiming to understanding the correlation between solvation structures and Li anode stability.Further perspectives on the solvation design are provided in light of anode interfacial stability in LMBs.

Co3O4 nanocage derived from metal-organic frameworks: An excellent cathode catalyst for rechargeable Li-O2 battery

Rechargeable non-aqueous Li-O2 battery is regarded as one of the most promising energy-storage technologies on account of its high energy density.It is believed that the rational design of three-dimensional (3D) architecture for catalyst is a key factor for the remarkable performance.Metal-organic frameworks (MOFs) derived materials possess excellent architecture,which is beneficial for Li-O2 batteries.In this work,ZIF-67 is used as precursor template and calcinated under different temperature to produce Co3O4 crystals.When the anneal treatment is under 350℃,the derived Co3O4 nanocage holds the most complete skeleton,which provides better charge transfer ability as well as O2 and Li^+ diffusion.Meanwhile,the Co3O4 nanocage owns more oxygen vacancies,offering more active sites.With the synergistic effect of nanocage structure and active sites,the Co3O4 nanocage stably delivers a large specific capacity of 15,500 mAh·g^-1 as well as a long cycle-life of 132 cycles at limited discharge capacity of 1,000 mAh·g^-1 under discharge/charge current density of 0.5 A·g^-1.