First-cycle irreversibility of layered Li-Ni-Co-Mn oxide cathode in Li-ion batteries.
The first-cycle irreversibility of Li{sub 1.048}(Ni{sub 1/3}Co{sub 1/3}Mn{sub 1/3}){sub 0.952}O{sub 2} (LiMO{sub 2}) cathode material in lithium and lithium-ion cells has been studied using galvanostatic cycling and in situ synchrotron X-ray diffraction. The so-called 'lost capacity' of a Li/LiMO{sub 2} cell observed during initial cycle in conventional voltage ranges (e.g., 3.0-4.3 V) could be completely recovered by discharging the cell to low voltages (<2 V). During the deep discharge, the lithium cell exhibited an additional voltage plateau, which is believed to result from the formation of Li{sub 2}MO{sub 2}-like phase on the oxide particle surface due to very sluggish lithium diffusion in Li{sub 1-{Delta}}MO{sub 2} with {Delta} {yields} 0 (i.e., near the end of discharge). Voltage relaxation curve and in situ X-ray diffraction patterns, measured during relaxation of the lithium cell after deep discharge to obtain 100% cycle efficiency, suggested that the oxide cathode returned to its original state after the following two-step relaxation processes: relatively quick disappearance of the Li{sub 2}MO{sub 2}-like phase on the particle surface, followed by slow lithium diffusion in the layered structure. Experiments conducted in Li{sub 4}Ti{sub 5}O{sub 12}/LiMO{sub 2} lithium-ion cells confirmed that the physical loss of lithium (via surface film formation or parasitic electrochemical reactions, etc.) from LiMO{sub 2} was negligible up to an oxide voltage of 4.3 V vs. Li{sup +}/Li.
- Research Organization:
- Argonne National Lab. (ANL), Argonne, IL (United States)
- Sponsoring Organization:
- EE
- DOE Contract Number:
- DE-AC02-06CH11357
- OSTI ID:
- 985114
- Report Number(s):
- ANL/CSE/JA-62171; TRN: US1006076
- Journal Information:
- Electrochim. Acta, Vol. 54, Issue Jul. 2008; ISSN 0013-4686
- Country of Publication:
- United States
- Language:
- ENGLISH
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