Lithium-sulfur cell with combining carbon nanofibers–sulfur cathode and gel polymer electrolyte

Abstract

In this paper we report a novel lithium-sulfur cell, which is characteristic of a unique combination of carbon nanofibers–sulfur cathode and gel polymer electrolyte (GPE). In particular, the carbon nanofibers for the cathode and the poly(acrylonitrile)/poly(methyl methacrylate) (PAN/PMMA) membrane for the GPE are prepared by electrospinning technique. The GPE consists of electrospun PAN/PMMA membrane and 1 mol kg−1 lithium bis(trifluoromethylsulfonyl)imide in N-methyl-N-butylpiperidinium bis(trifluoromethanesulfonyl)imide (PPR14TFSI) and poly (ethylene glycol) dimethyl ether (PEGDME). The membrane and cell performances are investigated by scanning electron spectroscopy, cyclic voltammetry and electrochemical impedance spectroscopy. It is found that the cell using the GPE based on PAN/PMMA membrane and PPR14TFSI-PEGDME (1:1) exhibits the largest discharge capacity and the best cycle durability. The discharge capacity of this cell remains at 760 mA h g−1 after 50 cycles. This new sulfur/electrolyte system combines the advantages of the carbon nanofibers that provide an effective conduction path and network-like structure, and the GPE that suppresses the dissolution of the intermediate products generated during the discharge process. The ratio of PPR14TFSI to PEGDME affects the ionic conductivity of the GPE, the stability of the sulfur electrode and the compatibility of lithium electrode with the GPE.