Structure and reactions mechanism of sulfurized polyacrylonitrile as cathodes for rechargeable Li-S batteries

Sulfurized polyacrylonitrile(S@pPAN)composite provides a conductive pathway for sulfur active material at the molecular level and has already become one of the most promising cathode materials in lithium-sulfur batteries because of its outstanding electrochemical performances via novel solid-solid conversion mechanism.Although there are a great number of researches on the S@pPAN composite material,the accurate structure of S@pPAN and its redox reaction mechanism during the charge-discharge process still have not been determined.The previous research and inferences about the structure of S@pPAN and its electrochemical reaction mechanism were summarized in this review,providing a reference for the future study of lithiumsulfur batteries.

A Mixed Ether Electrolyte for Lithium Metal Anode Protection in Working Lithium-Sulfur Batteries

Lithium-sulfur(Li-S) battery is considered as a promising energy storage system to realize high energy density.Nevertheless,unstable lithium metal anode emerges as the bottleneck toward practical applications,especially with limited anode excess required in a working full cell.In this contribution,a mixed diisopropyl ether-based(mixed-DIPE) electrolyte was proposed to effectively protect lithium metal anode in Li-S batteries with sulfurized polyacrylonitrile(SPAN) cathodes.The mixed-DIPE electrolyte improves the compatibility to lithium metal and suppresses the dissolution of lithium polysulfides,rendering significantly improved cycling stability.Concretely,Li | Cu half-cells with the mixed-DIPE electrolyte cycled stably for 120 cycles,which is nearly five times longer than that with routine carbonate-based electrolyte.Moreover,the mixedDIPE electrolyte contributed to a doubled life span of 156 cycles at 0.5 C in Li | SPAN full cells with ultrathin 50 μm Li metal anodes compared with the routine electrolyte.This contribution affords an effective electrolyte formula for Li metal anode protection and is expected to propel the practical applications of high-energy-density Li-S batteries.

Flexible,solid-state,fiber-network-reinforced composite solid electrolyte for long lifespan solid lithium-sulfurized polyacrylonitrile battery

Solid lithium-sulfur batteries(SLSBs)show potential for practical application due to their possibility for high energy density.However,SLSBs still face tough challenges such as the large interface impedance and lithium dendrite formation.Herein,a highperformance SLSB is demonstrated by using a fiber network reinforced Li_(6.75)La_(3)Zr_(1.75)Ta_(0.25)O_(12)(LLZTO)based composite solid electrolyte(CSE)in combination with sulfurized polyacrylonitrile(SPAN)cathode.The CSE consisting of an electrospun polyimide(PI)film,LLZTO ionically conducting filler and polyacrylonitrile(PAN)matrix,which is named as PI-PAN/LLZTO CSE,possesses high room-temperature ionic conductivity(2.75×10^(-4)S/cm),high Li^(+)migration number(tLi+)of 0.67 and good interfacial wettability.SPAN is utilized due to its unique electrochemical properties:reasonable electronic conductivity and no polysulfides shuttle effect.The CSE enables a highly stable Li plating/stripping cycle for over 600 h and good rate performance.Moreover,the assembled SLSB exhibits good cycle performance of accomplishing 120 cycles at 0.2 C with the capacity retention of 474 mAh/g,good rate properties and excellent long-term cycling stability with a high capacity retention of 86.49%from 15^(th)to 1,000^(th)cycles at 1.0 C.This work rationalizes our design concept and may guide the future development of SLSBs.