Implications of QdV/dQ for the analysis of performance fade in lithium-ion batteries.
The Advanced Technology Development Program (ATD) was established by the U.S. Department of Energy to investigate key issues affecting the calendar and cycle life of high-power lithium-ion batteries. These issues include impedance rise and power fade. For the purposes of this study, 18650-sized cells containing commercially available chemistries were built to our specifications. The cells employed LiNi{sub 0.8}Co{sub 0.15}Al{sub 0.05}O{sub 2} cathodes, MAG-10 synthetic graphite anodes, and 1.2 M LiPF{sub 6} in EC:EMC (3:7) electrolyte. They were subjected to both standard and accelerated calendar and cycle life tests. All tests were performed at 60% SOC. The cells were tested for calendar life at 45 and 55 C. They were also tested for cycle life at 25 and 45 C. As a part of the test, the cells were initially characterized by undergoing a series of performance tests, including a C/25 discharge and charge. The cells were then aged at the desired temperatures for 4-week periods. At the end of 4 weeks, the cells were cooled to 25 C and the performance tests were repeated to determine how the cells changed during the time at temperature. The differential voltage curves, QdV/dQ (where Q is the initial C/25 discharge capacity), were calculated using the C/25 discharge and charge data. For the calculation, the individual changes in voltage per change in capacity, Q{Delta}V/{Delta}Q, were smoothed and plotted as a function of state of charge or cell potential. Typical plots of -QdV/dQ vs. %SOC for the discharge portion of Group A calendar and cycle life cells at 45 C are given in Figs. 1 and 2. A vertical offset was added to each curve to make visualization and interpretation easier.
- Research Organization:
- Argonne National Lab. (ANL), Argonne, IL (United States)
- Sponsoring Organization:
- EE
- DOE Contract Number:
- DE-AC02-06CH11357
- OSTI ID:
- 963257
- Report Number(s):
- ANL/CMT/CP-110654; TRN: US200917%%205
- Resource Relation:
- Conference: 204th Meeting of the Electrochemical Society; Oct. 12, 2003 - Oct. 16, 2003; Orlando, FL
- Country of Publication:
- United States
- Language:
- ENGLISH
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