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Temperature Dependence of Electrochemical Degradation in LiNi 1/3 Mn 1/3 Co 1/3 O 2 /Li 4 Ti 5 O 12 Cells
Author(s) -
Björklund Erik,
Naylor Andrew J.,
Brant William,
Brandell Daniel,
Younesi Reza,
Edström Kristina
Publication year - 2019
Publication title -
energy technology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.91
H-Index - 44
eISSN - 2194-4296
pISSN - 2194-4288
DOI - 10.1002/ente.201900310
Subject(s) - x ray photoelectron spectroscopy , electrolyte , electrochemistry , materials science , lithium (medication) , xanes , analytical chemistry (journal) , electrode , chemical engineering , spectroscopy , chemistry , medicine , physics , quantum mechanics , chromatography , engineering , endocrinology
Aging mechanisms in lithium‐ion batteries are dependent on the operational temperature, but the detailed mechanisms on what processes take place at what temperatures are still lacking. The electrochemical performance and capacity fading of the common cell chemistry LiNi 1/3 Mn 1/3 Co 1/3 O 2 (NMC)/Li 4 Ti 5 O 12 (LTO) pouch cells are studied at temperatures 10, 30, and 55 °C. The full cells are cycled with a moderate upper cutoff potential of 4.3 V versus Li + /Li. The electrode interfaces are characterized postmortem using photoelectron spectroscopy techniques (soft X‐ray photoelectron spectroscopy [SOXPES], hard X‐ray photoelectron spectroscopy [HAXPES], and X‐ray absorption near edge structure [XANES]). Stable cycling at 30 °C is explained by electrolyte reduction forming a stabilizing interphase, thereby preventing further degradation. This initial reaction, between LTO and the electrolyte, seems to be beneficial for the NMC–LTO full cell. At 55 °C, continuous electrolyte reduction and capacity fading are observed. It leads to the formation of a thicker surface layer of organic species on the LTO surface than at 30 °C, contributing to an increased voltage hysteresis. At 10 °C, large cell‐resistances are observed, caused by poor electrolyte conductivity in combination with a relatively thicker and Li x PF y ‐rich surface layer on LTO, which limit the capacity.