Synthesis and electrochemical performance of La_(2)CuO_(4)as a promising coating material for high voltage Li-rich layered oxide cathodes

The structural transformations,oxygen releasing and side reactions with electrolytes on the surface are considered as the main causes of the performance degradation of Li-rich layered oxides(LROs)cathodes in Li-ion batteries.Thus,stabilizing the surfaces of LROs is the key to realize their practical application in high energy density Li-ion batteries.Surface coating is regarded as one of the most effective strategies for high voltage cathodes.The ideal coating materials should prevent cathodes from electrolyte corrosion and possess both electronic and Li-ionic conductivities simultaneously.However,commonly reported coating materials are unable to balance these functions well.Herein,a new type of coating material,La_(2)CuO_(4)was introduced to mitigate the surface issues of LROs for the first time,due to its superb electronic conductivity(26-35 mS·cm^(-1))and lithium-ionic diffusion coefficient(10^(-12)-10^(-13)cm^(2)·s^(-1)).After coating with the La_(2)CuO_(4),the capacity retention of Li_(1.2)Ni_(0.54)Co_(0.13)Mn_(0.13)O_(2)cathode was increased to 85.9%(compared to 79.3%of uncoated cathode)after 150 cycles in the voltage range of 2.0-4.8 V.In addition,only negligible degradations on the deliverable capacity and rate capability were observed.

Probing component contributions and internal polarization in silicon-graphite composite anode for lithium-ion batteries with an electrochemical-mechanical model

Silicon–graphite(Si–Gr)composite anodes are attractive alternatives to replace Gr anodes for lithium-ion batteries(LIBs)owing to their relatively high capacity and mild volume change.However,it is difficult to understand electrochemical interactions of Si and Gr in Si–Gr composite anodes and internal polarization of LIBs with regular experiment methods.Herein,we establish an electrochemical-mechanical coupled model to study the effect of rate and Si content on the electrochemical and stress behavior in a Si–Gr composite anode.The results show that the composites of Si and Gr not only improve the lithiation kinetics of Gr but also alleviate the voltage hysteresis of Si and decrease the risk of lithium plating in the negative electrode.What's more,the Si content is a tradeoff between electrode capacity and electrode volume variation.Further,various internal polarization contributions of cells using Si–Gr composite anodes are quantified by the voltage decomposition method.The results indicate that the electrochemical polarization of electrode materials and the electrolyte ohmic over-potential are dominant factors in the rate performance of cells,which provides theoretical guidance for improving the rate performance of LIBs using Si–Gr composite anodes.