A chemo-mechanical model coupled with thermal effect on the hollow core–shell electrodes in lithium-ion batteries

Electrode is a key component to remain durability and safety of lithium-ion（Li-ion） batteries. Li-ion insertion/removal and thermal expansion mismatch may induce high stress in electrode during charging and discharging processes. In this paper, we present a continuum model based on COMSOL Multiphysics software, which involves thermal, chemical and mechanical behaviors of electrodes. The results show that,because of diffusion-induced stress and thermal mismatch, the electrode geometry plays an important role in diffusion kinetics of Li-ions. A higher local compressive stress results in a lower Li-ion concentration and thus a lower capacity when a particle is embedded another, which is in agreement with experimental observations.

Confining sulfur in sandwich structure of bamboo charcoal and aluminum fluoride(BC@S@AlF3) as a long cycle performance cathode for Li-S batteries

The ’shuttle effect’ of polysulfide causing rapid capacity fade and low coulo mbic efficiency of high ene rgy storage lithium-sulfur(Li-S) batteries.Herein,a sandwich structure of bamboo charcoal/sulfur coating by aluminum fluoride(BC@S@AlF3) composites is designed and fabricated for the first time.The as-designed cathode exhibited excellent electrochemical properties and stable capacity retention.The initial capacity reaches 1119 mA h/g and the capacity after 100 cycles is 869 mA h/g at 0.5 C,which is much stable than that of composite materials without bamboo charcoal or AlF3 coating.Moreover,the BC@S@AlF3 cathode presents excellent long-term capacity stability with a capacity decay of 0.073% per cycle during 500 charge/discharge cycles at 1 C,offering a potential for use in high energy Li-S batteries.The physical confinement,chemical ancho ring,and catalysis conversion for active sulfur are achieved simultaneously with the AlF3 coating and bamboo charcoal core with porous structure.