TY - JOUR

T1 - High-energy NCA cells on idle

T2 - anode versus cathode driven side reactions

AU - Aragon Zulke, Alana

AU - Hoster, Harry

AU - Mercer, Michael

AU - Burrell, Robert

AU - Li, Yi

AU - Nagarathinam, Mangayarkarasi

PY - 2021/6/30

Y1 - 2021/6/30

N2 - We report on the first year of calendar ageing of commercial high‐energy 21700 lithium‐ion cells, varying over eight state of charge (SoC) and three temperature values. Lithium‐nickel‐cobalt‐aluminium oxide (NCA) and graphite with silicon suboxide (Gr‐SiOx) form cathodes and anodes of those cells, respectively. Degradation is fastest for cells at 70–80 % SoC according to monthly electrochemical check‐up tests. Cells kept at 100 % SoC do not show the fastest capacity fade but develop internal short circuits for temperatures T≥40 °C. Degradation is slowest for cells stored close to 0 % SoC at all temperatures. Rates of capacity fade and their temperature dependencies are distinctly different for SoC values below and above 60 %, respectively. Differential voltage analyses, apparent activation energy analysis, and endpoint slippage tracking provide useful insights into the degradation mechanisms and the respective roles of anode and cathode potential. We discuss how reversible losses of lithium might play a role in alleviating the rate of irreversible losses on commercial cells.

AB - We report on the first year of calendar ageing of commercial high‐energy 21700 lithium‐ion cells, varying over eight state of charge (SoC) and three temperature values. Lithium‐nickel‐cobalt‐aluminium oxide (NCA) and graphite with silicon suboxide (Gr‐SiOx) form cathodes and anodes of those cells, respectively. Degradation is fastest for cells at 70–80 % SoC according to monthly electrochemical check‐up tests. Cells kept at 100 % SoC do not show the fastest capacity fade but develop internal short circuits for temperatures T≥40 °C. Degradation is slowest for cells stored close to 0 % SoC at all temperatures. Rates of capacity fade and their temperature dependencies are distinctly different for SoC values below and above 60 %, respectively. Differential voltage analyses, apparent activation energy analysis, and endpoint slippage tracking provide useful insights into the degradation mechanisms and the respective roles of anode and cathode potential. We discuss how reversible losses of lithium might play a role in alleviating the rate of irreversible losses on commercial cells.

KW - Lithium-ion Battery

KW - Calendar Ageing

KW - Lithium Nickel-Cobalt-Aluminium Oxide

KW - Graphite-silicon Anode

KW - Coulomb tracking

U2 - 10.1002/batt.202100046

DO - 10.1002/batt.202100046

M3 - Journal article

VL - 4

SP - 934

EP - 947

JO - Batteries & Supercaps

JF - Batteries & Supercaps

IS - 6

ER -