A bi-functional strategy involving surface coating and subsurface gradient co-doping for enhanced cycle stability of LiCoO_(2) at 4.6 V

Layered LiCoO_(2)(LCO)acts as a dominant cathode material for lithium-ion batteries(LIBs)in 3C products because of its high compacted density and volumetric energy density.Although improving the high cutoff voltage is an effective strategy to increase its capacity,such behavior would trigger rapid capacity decay due to the surface or/and structure degradation.Herein,we propose a bi-functional surface strategy involving constructing a robust spinel-like phase coating layer with great integrity and compatibility to LiCoO_(2) and modulating crystal lattice by anion and cation gradient co-doping at the subsurface.As a result,the modified LiCoO_(2)(AFM-LCO)shows a capacity retention of 80.9%after 500 cycles between 3.0and 4.6 V.The Al,F,Mg enriched spinel-like phase coating layer serves as a robust physical barrier to effectively inhibit the undesired side reactions between the electrolyte and the cathode.Meanwhile,the Al,F,Mg gradient co-doping significantly enhances the surficial structure stability,suppresses Co dissolution and oxygen release,providing a stable path for Li-ions mobility all through the long-term cycles.Thus,the surface bi-functional strategy is an effective method to synergistically improve the electrochemical performances of LCO at a high cut-off voltage of 4.6 V.

A composite PEO electrolyte with amide-based polymer matrix for suppressing lithium dendrite growth in all-solid-state lithium battery

The lithium dendrite growth is still a serious challenge and impeding the realistic applications of all-solid-state lithium batteries.In view of the amide containing sediment layer can be stable on lithium/cathodes,a composite polymer electrolyte with amide-based matrix is in-situ built on porous electrodes.With the introduction of amide,the polymer electrolyte presents excellent ability to inhibit lithium dendrite growth and makes the Li/Li symmetric battery stably work for 500 h with a good ionic conductivity of 4.25×10^(-5)S/cm at 40℃.The solid electrolyte also shows a wide electrochemical stable window and good interface contact with the porous cathode.Utilizing this composite polymer electrolyte,the all-solid-state Li/LiFePO_(4) battery shows an initial discharge capacity of 146.5 mA h/g at 0.1 C under 40℃ and remains 81.4%in 100 cycles.The polymer electrolyte also can present better properties after modification.These results demonstrate that the presented PA-based composite polymer electrolyte could be served as a good electrolyte candidate for all-solid-state lithium-ion batteries.