Layered Potassium Titanium Niobate/Reduced Graphene Oxide Nanocomposite as a Potassium‑Ion Battery Anode

With graphite currently leading as the most viable anode for potassium-ion batteries(KIBs),other materials have been left relatively underexamined.Transition metal oxides are among these,with many positive attributes such as synthetic maturity,longterm cycling stability and fast redox kinetics.Therefore,to address this research deficiency we report herein a layered potassium titanium niobate KTiNbO5(KTNO)and its rGO nanocomposite(KTNO/rGO)synthesised via solvothermal methods as a high-performance anode for KIBs.Through effective distribution across the electrically conductive rGO,the electrochemical performance of the KTNO nanoparticles was enhanced.The potassium storage performance of the KTNO/rGO was demonstrated by its first charge capacity of 128.1 mAh g^(−1) and reversible capacity of 97.5 mAh g^(−1) after 500 cycles at 20 mA g^(−1),retaining 76.1%of the initial capacity,with an exceptional rate performance of 54.2 mAh g^(−1)at 1 A g^(−1).Furthermore,to investigate the attributes of KTNO in-situ XRD was performed,indicating a low-strain material.Ex-situ X-ray photoelectron spectra further investigated the mechanism of charge storage,with the titanium showing greater redox reversibility than the niobium.This work suggests this lowstrain nature is a highly advantageous property and well worth regarding KTNO as a promising anode for future high-performance KIBs.

Polybenzimidazole functionalized electrolyte with Li-wetting and self-fluorination functionalities for practical Li metal batteries

Rough Li plating,low ionic conductivity,and low thermal stability of conventional electrolytes post-primary challenges for achieving reliable high-capacity rechargeable lithium batteries,for which lithiummetal is frequently proposed as themost promising anode material.Conventional low-polarity commercial polypropylene/polyethylene separators fail to support the application of high-energy-density Li anodes due to their rigid physicochemical properties and the high reactivity of Li metal,leading to fatal dendrite formation and vigorous exothermic reaction with electrolytes.Herein,we develop a Li-wetting,flame-retardant binary polymer electrolyte by functionalizing poly(vinylidene fluoride)(PVDF)separators with nonflammable polybenzimidazole(PBI)to build safe room-temperature solid-state electrolyte membranes.A dendrite-free LiFePO4 cell with the solid polymer electrolyte(SPE)delivers a discharge capacity of 127 mAh g^(-1) at 25℃ with a capacity retention of 87.5%after 500 cycles at 0.5℃(0.15 mA cm^(-2)).Phase-field simulations and density functional theory calculations demonstrate that the negatively charged benzimidazole chains of PBI own superior affinity to lithium bis(trifluoromethanesulfonyl)imide(LiTFSI),and shares overlapping electron density with Li anode,giving rise to accelerated Li^(+)conduction at room temperature and uniform Li electrodeposition at the electrolyte/Li metal interface.The SPE is also flame-retardant since heat-resistant polytetrafluoroethylene and a dense,heat-blocking graphitized carbon layer are formed in intense heat throughdehydrogenation/fluorination of PVDF under the catalysis of Lewis base imidazole rings and the decomposition of benzimidazole rings in PBI.No such fire-resistant mechanism is ever reported in conventional electrolytes.