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Title: Ab initio structure search and in situ 7Li NMR studies of discharge products in the Li–S battery system

The high theoretical gravimetric capacity of the Li–S battery system makes it an attractive candidate for numerous energy storage applications. In practice, cell performance is plagued by low practical capacity and poor cycling. In an effort to explore the mechanism of the discharge with the goal of better understanding performance, we examine the Li–S phase diagram using computational techniques and complement this with an in situ 7Li NMR study of the cell during discharge. Both the computational and experimental studies are consistent with the suggestion that the only solid product formed in the cell is Li2S, formed soon after cell discharge is initiated. In situ NMR spectroscopy also allows the direct observation of soluble Li+-species during cell discharge; species that are known to be highly detrimental to capacity retention. We suggest that during the first discharge plateau, S is reduced to soluble polysulfide species concurrently with the formation of a solid component (Li2S) which forms near the beginning of the first plateau, in the cell configuration studied here. The NMR data suggest that the second plateau is defined by the reduction of the residual soluble species to solid product (Li2S). Lastly, a ternary diagram is presented to rationalize the phasesmore » observed with NMR during the discharge pathway and provide thermodynamic underpinnings for the shape of the discharge profile as a function of cell composition.« less
Authors:
 [1] ;  [2] ;  [2] ;  [2] ;  [2] ;  [3] ;  [1] ;  [2] ;  [2] ;  [4] ;  [1]
  1. Univ. of California, Santa Barbara, CA (United States)
  2. Univ. of Cambridge, Cambridge (United Kingdom)
  3. Univ. of Michigan, Ann Arbor, MI (United States)
  4. Univ. of Cambridge, Cambridge (United Kingdom); SUNY Stony Brook, Stony Brook, NY (United States)
Publication Date:
Grant/Contract Number:
AC02-05CH11231
Type:
Published Article
Journal Name:
Journal of the American Chemical Society
Additional Journal Information:
Journal Volume: 136; Journal Issue: 46; Journal ID: ISSN 0002-7863
Publisher:
American Chemical Society (ACS)
Research Org:
Stony Brook Univ., Stony Brook, NY (United States)
Sponsoring Org:
USDOE Office of Energy Efficiency and Renewable Energy (EERE), Vehicle Technologies Office (EE-3V)
Country of Publication:
United States
Language:
English
Subject:
25 ENERGY STORAGE; 36 MATERIALS SCIENCE
OSTI Identifier:
1171658
Alternate Identifier(s):
OSTI ID: 1345821