Thermodynamics-directed bulk/grain-boundary engineering for superior electrochemical durability of Ni-rich cathode

Introducing high-valence Ta element is an essential strategy for addressing the structu ral deterioration of the Ni-rich LiNi_(1-x-y)Co_(x)Mn_(y)O_(2)(NCM)cathode,but the enlarged Li/Ni cation mixing leads to the inferior rate capability originating from the hindered Li~+migration.Note that the non-magnetic Ti~(4+)ion can suppress Li/Ni disorder by removing the magnetic frustration in the transition metal layer.However,it is still challenging to directionally design expected Ta/Ti dual-modification,resulting from the complexity of the elemental distribution and the uncertainty of in-situ formed coating compounds by introducing foreign elements.Herein,a LiTaO_3 grain boundary(GB)coating and bulk Ti-doping have been successfully achieved in LiNi_(0.834)Co_(0.11)Mn_(0.056)O_(2) cathode by thermodynamic guidance,in which the structural formation energy and interfacial binding energy are employed to predict the elemental diffusion discrepancy and thermodynamically stable coating compounds.Thanks to the coupling effect of strengthened structural/interfacial stability and improved Li~+diffusion kinetics by simultaneous bulk/GB engineering,the Ta/Ti-NCM cathode exhibits outstanding capacity retention,reaching 91.1%after 400 cycles at 1 C.This elaborate work contributes valuable insights into rational dual-modification engineering from a thermodynamic perspective for maximizing the electrochemical performances of NCM cathodes.

Stabilizing surface chemistry and texture of single-crystal Ni-rich cathodes for Li-ion batteries

The single-crystalline Ni-rich cathodes are believed to help improve the safety of Li-ion batteries(LIBs),however,the ion-diffusion limits their high-rate performance owing to large single-crystal particles.Herein,a dual-modification strategy of surface Li_(2)TiO_(3)-coating and bulk Ti-doping has been performed to achieve high-rate single crystal LiNi_(0.83)Co_(0.12)Mn_(0.05)O_(2)(NCM)cathode.The Li-ion conductive Li_(2)TiO_(3) coating layer facilitates the Li-ion transfer and prevents the electrolyte erosion.Meanwhile,the robust Ti-O bonds stabilize the cubic close-packed oxygen framework and mitigate the Li/Ni disorder.The synergy endows the dual-modified NCM with enhanced de-/lithiation reaction kinetics and stable surface chemistry.A high specific capacity of 128 mAh g^(-1) is delivered even at 10 C with an extended cycle life.This finding is reckoned to pave the way for developing high energy density LIBs for long-range electric vehicles.