Stable and Fast Lithium–Sulfur Battery Achieved by Rational Design of Multifunctional Separator

Lithium–sulfur(Li-S) battery is considered as one of the most promising candidates for future portable electronics and electric vehicles due to high energy density and potentially low cost. However, the severe polysulfides shuttling in Li-S battery always causes low Coulombic efficiency, capacity fading, and hindering its practical commercialization. Herein, a dualfunctional PEI@MWCNTs-CB/MWCNTs/PP(briefly denoted as PMS)separator is assembled through Langmuir–Blodgett–Scooping(LBS) technique for improvement of Li-S battery performance, that is, rational integrating conductive MWCNTs multilayer on a routine PP separator with polyethyleneimine(PEI) polymer. Owing to "proton-sponge"-based PEI feature with the abundant amino/imine groups and branched structures, the PMS separator can provide strong affinity to immobilize the negatively charged polysulfides via electrostatic interaction. Simultaneously,incorporated with the conductive MWCNTs multilayers for the electron transportation, the Li-S cells assembled with PMS separators achieve exceptional high delivery capacity, good rate performance(~550 m Ah g-1 at a current density of 9 A g-1), and stable cycling retention(retention of84.5% at a current density of 1 A g-1) even over 120 cycles, especially in the case of high-loading sulfur cathode(80 wt% of S content). This multifunctional separator with dual-structural architectures via self-assembly LBS method paves new avenues to develop high-performance Li-S batteries.

Insights on“nitrate salt”in lithium anode for stabilized solid electrolyte interphase

A Li/KNO_(3) composite(LKNO),with KNO_(3) uniformly implanted in bulk metallic Li,is fabricated for battery anode via a facile mechanical kneading approach,which exhibits high Coulombic efficiency and prolonged cycle life.The mechanism behind the enhanced electrochemical performance of the“salt-in-metal”composite is investigated,where KNO_(3) in metallic Li composite electrode would be sustainably released into the electrolyte.The presence of NO_(3)-stabilizes the solid electrolyte interphase by producing functional Li_(3)N,LiNxOy,and Li_(2)O species.K^(+)from KNO_(3) also helps to form an electrostatic shield after its adsorption on the electrode protrusions,which suppresses the dendritic growth of metallic Li.With the above advantages,uniform Li plating with dense and planar structure is realized for the LKNO electrode.These findings reveal a deep understanding of the effect of the“saltin-metal”anode and provide new insights into the use of nitrate additives for high-energy-density Li metal batteries.

Dynamic dispersion stability of graphene oxide with metal ions

Graphene oxide(GO),an important chemical precursor of graphene,can stably disperse in aqueous surrounding and undergo aggregation as metal cations introduced.The usual instability of GO with ions is caused by the shielding effect of ions and crosslinking between GO and ions.However,the dynamic stability of GO under ions exchange still remains unclear.Here,we investigated the dynamic dispersion stability of GO with metal ions and observed a redispersion behavior in concentrated Fe3+solution,other than permanent aggregation.The exchange with Fe3+ions drives the reversion of zeta(ζ)potential and enables the redispersion to individual GO-Fe3+complex sheets,following a dynamic electric double layer(EDL)mechanism.It is found that the specifically strong electrostatic shielding effect and coordination attraction between Fe3+and functional oxygen groups allows the selective redispersion of GO in concentrated Fe3+solution.The revealed dynamic dispersion stability complements our understanding on the dispersive stability of GO and can be utilized to fabricate graphene-metal hybrids for rich applications.