Trace doping realizing superior electrochemical performance in P2-type Na_(0.50)Li_(0.08)Mn_(0.60)Co_(0.16)Ni_(0.16)0_(2)cathode for sodium-ion batteries

P2-type layered oxides are receiving significant interest due to their superior structure and intrinsic performances.There are strenuous attempts to balance the structure stability,phase transition as well as desirable electrochemical performances by inducing anion/cation ions,changing morphology,adjusting valence,etc.In this work,several same-period elements of Sc,Ti,V,Cr,Fe,Cu and Zn are doped into Na_(0.50)Li_(0.08)Mn_(0.60)Co_(0.16)Ni_(0.16)O_(2)cathodes,which are manipulated by ions radii and valence state,further studied by operando X-ray powder diffraction patterns(XRD).As a result,the Cu^(2+)doped cathode performed higher rate capacities(as high as 86 mAh/g even at 10 C)and more stable structures(capacity retention of~89.4%for 100 cycles),which owing to the synergistic effect among the tightened TMO_(2)layer,enlarged d-spacing,reduce O-O electrostatic repulsion,ameliorate lattice distortion as well as mitigate ordering of Na^(+)/vacancy.

Improving rate performances of Li-rich layered oxide by the co-doping of Sn and K ions

The specific capacities and power performances of conventional cathode materials are still needed to improve in order to meet the demand for electrical vehicles.Li-rich layered oxide delivers a high specific capacity,but poor rate performances.Chemical doping is an effective way to address this challenge due to the expanded crystal lattice.Unlike a single ion substitution in the literature,here Li-rich layered oxides were doped by Sn and K to achieve the favorite rate performance,where Sn and K were assumed to replace transition metal ion and Li ion,respectively.Results indicate the co-doped samples result in an increasing capacity retention by more than 40%from 107.9(contrast sample)to 151.5 mAh g^(-1)(co-doped sample)at 10 C-rate.Electrochemical impedance spectroscopy(EIS)and calculated diffusion coefficient of Li^(+) also confirmed the favorite rate performances for co-doped sample.Combining results of Rietveld structure refinement,we proposed that the reason for rate performances comes from the enlarged crystal lattices,which provides a smooth diffusion tunnel for Lithium ions during the charge/discharge processes.The as-adopted method provides a possibility to achieve the improved rate performances by co-doping big-size ions at the different crystal sites.