Arranging cation mixing and charge compensation of TiNb_(2)O_(7) with W^(6+) doping for high lithium storage performance

TiNb_(2)O_(7) is an advanced anode material for high-energy density lithium-ion batteries(LIBs) due to its considerable specific capacity and satisfactory safety.However,its rate capability is limited by its poor ionic conductivity and electronic conductivity.To solve this problem,TiNb_(2)O_(7) with W^(6+) doping was synthesized by a convenient solid-state method.The doping of W^(6+) will lead to arranging cation mixing and charge compensation.The cation rearrangement creates a new Li-conductive environment for lithiation,resulting in a low-energy barrier and the fast Li^(+)storage/diffusion.The results show that the Li^(+)diffusion coefficient of W_(0.06)Ti_(0.91)Nb_(2)O_(7) is increased by 9.96 times greater than that of TiNb_(2)O_(7).Besides,as the calculation proves,due to the partial reduction of the Nb^(5+)and Ti^(4+) caused by charge compensation,W^(6+)doping results in low charge transfer resistance and excellent electronic conductivity.Moreover,W^(6+) doping accounts for a high pseudocapacitive contribution.At the scan rate of 1 mV·s^(-1),the pseudocapacitive contribution for TiNb_(2)O_(7) is 78%,while that for W_(0.06)Ti_(0.91)Nb_(2)O_(7) increases to 83%.The reversible specific capacity of W_(0.06)Ti_(0.91)Nb_(2)O_(7) after 600 cycles is maintained at 148.90mAh·g^(-1) with a loss of only 16.37% at 10.0C.Also,it delivers a commendable capacity of 161.99 mAh·g^(-1) at20.0C.Even at 30.0C,it still retains a satisfactory capacity of 147.22 mAh·g^(-1),much higher than TiNb_(2)O_(7)(97.49mAh·g^(-1)).Our present study provides ideas for the development of electrode materials for lithium-ion batteries.

Synergistic electronic interaction between ruthenium and nickel-iron hydroxide for enhanced oxygen evolution reaction

The efficiency of electrochemical water splitting is extremely hampered by the sluggish oxygen evolution reaction(OER)occurred at the anode.Therefore,developing high-performance OER electrocatalysts is crucial for realizing the industrialized application of water splitting.Herein,a high-efficiency electrocatalyst of ruthenium-decorated nickel-iron hydroxide(10 Ru-NiFe LDH)supported on Ni foam is successfully synthesized for OER.Modifying NiFe LDH with ruthenium can optimize the electronic density to form high valences of metal sites,which is beneficial to promote its OER performance.Consequently,the 10 Ru-NiFe LDH only needs a low overpotential of 222 mV to achieve a current density of50 mA,cm^(-2),which exhibits fast OER kinetics with a small Tafel slope of 58 mV.dec^(-1).Moreover,this electrocatalyst shows high stability over 20 h at a high current density of 100 mA·cm^(-2)without obvious decay.The decent OER performances can be ascribed to the increased active sites and the synergistic electronic interactions among Ni,Fe and Ru.This work provides an effective approach for designing desirable electrocatalysts for OER.