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SUMMARY:Using redox mediators for Li-O2 and Li-S batteries and Li recyclin
 g - Prof Nuria Garcia-Araez\, University of Southampton
DTSTART:20161115T160000Z
DTEND:20161115T170000Z
UID:TALK68711@talks.cam.ac.uk
CONTACT:Alice Wood
DESCRIPTION:Using redox mediators for Li-O2 and Li-S batteries and Li recy
 cling \n\nN. Garcia-Araez\, L. Yang\, J.T Frith J. W. Dibden\, N. Intarano
 nt\, and J.R. Owen\nUniversity of Southampton\nHighfield Campus\, SO17 1BJ
 \, Southampton\, United Kingdom\nn.garcia-araez@soton.ac.uk\n\nLithium-oxy
 gen and lithium-sulfur batteries have the potential to revolutionize the e
 nergy storage market\, since they can in principle store >5 times more ene
 rgy than the current lithium-ion battery technologies. However\, the perfo
 rmance of Li-O2 and Li-S batteries is currently limited by several fundame
 ntal issues. \n\nWe have recently shown that redox mediators can solve the
  two more important issues associated to Li O2 batteries\, i.e. electrode 
 passivation and degradation reactions.1 Degradation reactions are initiate
 d by superoxide radical species that are formed as intermediates in the pa
 thway of the reduction of oxygen: \nO2 + e- + Li+ → LiO2	\nLiO2 + e- + L
 i+ → Li2O2\nOn the example of ethyl viologen\, EtV2+\, we demonstrated t
 hat redox mediators can be used to decrease the lifetime of superoxide spe
 cies by promoting the fast reduction of superoxide to peroxide:\nEtV2+ + e
 - → EtV+\nLiO2 + EtV+ + Li+ → Li2O2 + EtV2+\nwhere EtV2+ acts as homog
 eneous catalyst and it is not consumed in the reaction. Furthermore\, EtV2
 + also acts as an electron shuttle\, preventing electrode passivation by d
 isplacing the location of the reduction of oxygen from the electrode surfa
 ce to the solution. Indeed\, a major increase in capacity is obtained upon
  addition of EtV2+ to a Li-O2 cell.\n\nIn Li-S batteries\, a variety of po
 lysulfides\, Li2Sn\, are formed in the pathway of the reduction of S to Li
 2S:\nn S + 2e- + 2Li+ → Li2Sn\nLi2Sn + (2n-2) e- + (2n-2) Li+ → n Li2S
 \nWe hypothesize that polysulfides can act as redox mediators and shuttles
  in Li-S batteries\, and their action can be optimized via a selection of 
 suitable electrolytes. We have recently developed a new method that allows
  predicting the equilibrium concentration of polysulfides in Li-S cells\, 
 as well as the theoretical electrochemical response of the cell as a funct
 ion of the amount of electrolyte.2 This new approach\, based on the constr
 uction of an experimental phase diagram\, will be used for the rational sc
 reening of electrolytes for Li-S batteries. \n\nRedox mediators are also a
  promising tool for Li recycling. We have shown that the reaction of batte
 ry materials (e.g. LiFePO4) with redox agents is a fast\, selective and ef
 ficient new method to extract lithium from natural brines and for recyclin
 g spent batteries.3\nReferences:\n1. L. Yang\, J.T. Frith\, N. Garcia-Arae
 z\, J.R. Owen. Chem. Commun. 2015\, 51\,1705-1708.\n2. J. W. Dibden\, J. W
 . Smith\, N. Zhou\, N. Garcia-Araez\, J. R. Owen. Chem. Commun. 2016\, DOI
 : 10.1039/C6CC05881G\n3. N. Intaranont\, N. Garcia-Araez\, A. Hector\, J.A
 . Milton\, J.R. Owen. J. Mater. Chem. A\, 2014\, 2\, 6374-6377.\n
LOCATION:Pfizer LT
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