3059wileyonlinelibrary.com of 1672 mAh g −1 and of 3860 mAh g −1 , which lead to very high theoretical specifi c energy (2550 Wh kg −1 ) and energy density (2862 Wh L −1 ) for Li-S batteries. However, the stable operation of the sulfur electrode, which signifi cantly differs from the intercalation mechanism in the traditional cathodes used in Li-ion batteries, still faces a series of barriers, including dissolution of long chain polysulfi des (Li 2 S m , m = 4-8), low utilization of sulfur, large volume expansion, and low Coulombic effi ciency (CE). [ 2 ] Moreover, in the so-called shuttle mechanism, lithium polysulfi des formed during discharge and charge processes will migrate from the cathode to the anode side to react with the metallic Li, leading to serious self-discharge, poor CE, and limited cycle life for Li-S batteries. [ 3 ] To address these critical issues, a variety of strategies have been developed to accommodate sulfur species, [ 4 ] mitigate the dissolution of polysulfi des, [ 5,6 ] and block the shuttle effect. [ 7,8 ] With the signifi cant progress made in the development of composite sulfur cathode materials in Li-S batteries, [ 9 ] the stability of a Li metal anode in Li-S batteries has become one of the more urgent challenges in order to reach the desired long-term stability of Li-S batteries. [ 10 ] A Li metal anode is the preferred anode in Li-S batteries not only because of its ultrahigh specifi c capacity, but also due to its low electrochemical potential (−3.040 V vs standard hydrogen electrode) as well as its light weight (molecular weight 6.94 g mol −1 , density 0.534 g cm −3 ) compared to other metals. [ 11 ] However, the use of Li metal as an anode in nonaqueous electrolyte batteries is challenging because Li often forms dendritic and mossy Li metal deposits during repeated charge/discharge cycles, leading to low CE and a short cycle life, as well as safety concerns. In Li-S batteries, a passivation layer is readily formed on the metallic Li anode surface due to the presence of polysulfi des and electrolyte additives. This layer will lead to increased cell resistance and failure of the Li-S battery. [ 10 ] Various strategies have been developed to minimize the corrosion of Li anodes and to reduce their increase in impedance under operating conditions, including the use of electrolyte additives, [ 12 ] co-solvent, [ 13 ] polymer electrolytes, [ 14 ] and interlayers. [ 8 ] Recently, concentrated electrolytes were demonstrated
Effect of the Anion Activity on the Stability of Li Metal Anodes in Lithium-Sulfur BatteriesRuiguo Cao , Junzheng Chen , Kee Sung Han , Wu Xu , Donghai Mei , Priyanka Bhattacharya , Mark H. Engelhard , Karl T. Mueller , Jun Liu , and Ji-Guang Zhang * With the signifi cant progress made in the development of cathodes in lithium-sulfur (Li-S) batteries, the stability of Li metal anodes becomes a more urgent challenge in these batteries. Here the systematic investigation of the stability of the anode/electrolyte interface in Li-S batteries with concentrated ele...