(Invited) Beyond Lithium Ion Batteries

Abstract

In other to enable 40 miles PHEVs and long electric drive range EVs, there is a need of developing advanced battery systems that offer at least 250 to 300 wh/kg energy density. The challenge is to develop batteries that are able to perform the requirements imposed by a PHEV system and yet meet market expectations in terms of cost and life. In this case, the PHEV battery will experience both deep discharge, like an electric vehicle, and shallow cycling necessary to maintain the battery for power assist in charge sustaining HEV mode. Conventional lithium-ion batteries based on metal oxides and graphite have made significant progress in recent years for HEV applications, however, durability with the PHEV duty cycle and the ultimate cost and safety of the technology remain key challenges. To achieve a very high all electric drive range, a new battery system is needed. In this talk, we will disclose new systems based on beyond lithium ion chemistry. Li/S batteries have attracted lots of attention because of their low cost and high energy-density. However, the dissolution of lithium polysulfides in non-aqueous electrolytes causes the accelerated capacity fade and low round turn energy efficiency of Li/S batteries during normal charge/discharge cycling. Alternatively, Li/Se has been newly explored to take advantage of extremely low solubility of Li2Se in non-aqueous electrolyte. In situ X-ray absorption spectroscopy at K edge of Se (~12.66 KeV) during the normal charge/discharge cycling of a Li/Se cell clearly shows that Se can be reversibly reduced to Li2Se upon lithium insertion reaction, and can be fully recovered upon the subsequently lithium removal reaction. More progress on Li/Se and Li/SeSx chemistry will be discussed in this talk. We will also disclose new lithium air based on Lithium superoxide and new close system based on lithium oxide/lithium superoxide that offers significantly high energy density.