Multi-Step Fast Charging of Commercial NMC/Graphite EV Pouch Cells: First-Life Extension, Degradation Mechanisms, and Second-Life Performance
- 1Department of Mechanical Engineering, San Diego State University, San Diego, CA 92182, USA
- 2Department of Electrical and Computer Engineering, San Diego State University, San Diego, CA 92182, USA
Abstract
Fast charging provides convenience for electric vehicle users but can accelerate Li-ion battery degradation and compromise lifetime energy utilization. Here, we investigate how fast-charging protocols govern first- and second-life performance of commercial 20 Ah NMC442/graphite pouch cells. A six-step 3C protocol (P6C2R1) completed 1009 first-life recorded cycles with >84.7% state of health (SOH) and limited resistance growth. Cells previously subjected to P6C2R1 subsequently demonstrated extended second-life cycling, including 1000 service cycles at 0.5C with ~80% SOH. Post-mortem scanning electron microscopy, X-ray diffraction, and X-ray photoelectron spectroscopy revealed reduced electrode deterioration, smaller structural changes, and a comparatively LiF-rich graphite interphase under multi-step fast charging (MS-FC). Increasing relaxation steps systematically delayed the onset of accelerated aging, while exploratory correlation analysis indicated that first-life aging trajectories contain information about subsequent second-life behavior beyond retirement SOH alone. Across measured first- and second-life operation, P6C2R1 delivered 64.6 kWh of cumulative discharge energy, 89% more than continuous fast charging. These results establish lifetime-aware MS-FC as a practical strategy for balancing charging speed, degradation, and second-life value in commercial lithium-ion batteries.
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BibTeX
@article{ko2026multistep,
title = {{Multi-Step Fast Charging of Commercial NMC/Graphite EV Pouch Cells: First-Life Extension, Degradation Mechanisms, and Second-Life Performance}},
author = {Shu-Ting Ko and Yuhong Fu and Cruz Gonsalves and Ziting Ma and Max Gonsalves and Aiden William Koenig-Russell and Chunting Chris Mi and Lingping Kong},
journal = {Batteries},
year = {2026},
month = oct,
doi = {10.3390/batteries12100403},
url = {https://www.mdpi.com/2313-0105/12/10/403},
note = {CC BY 4.0},
}
RIS
TY - JOUR
TI - Multi-Step Fast Charging of Commercial NMC/Graphite EV Pouch Cells: First-Life Extension, Degradation Mechanisms, and Second-Life Performance
AU - Shu-Ting Ko
AU - Yuhong Fu
AU - Cruz Gonsalves
AU - Ziting Ma
AU - Max Gonsalves
AU - Aiden William Koenig-Russell
AU - Chunting Chris Mi
AU - Lingping Kong
PY - 2026
DA - 2026/10/07
JO - Batteries
DO - 10.3390/batteries12100403
UR - https://www.mdpi.com/2313-0105/12/10/403
AB - Fast charging provides convenience for electric vehicle users but can accelerate Li-ion battery degradation and compromise lifetime energy utilization. Here, we investigate how fast-charging protocols govern first- and second-life performance of commercial 20 Ah NMC442/graphite pouch cells. A six-step 3C protocol (P6C2R1) completed 1009 first-life recorded cycles with >84.7% state of health (SOH) and limited resistance growth. Cells previously subjected to P6C2R1 subsequently demonstrated extended second-life cycling, including 1000 service cycles at 0.5C with ~80% SOH. Post-mortem scanning electron microscopy, X-ray diffraction, and X-ray photoelectron spectroscopy revealed reduced electrode deterioration, smaller structural changes, and a comparatively LiF-rich graphite interphase under multi-step fast charging (MS-FC). Increasing relaxation steps systematically delayed the onset of accelerated aging, while exploratory correlation analysis indicated that first-life aging trajectories contain information about subsequent second-life behavior beyond retirement SOH alone. Across measured first- and second-life operation, P6C2R1 delivered 64.6 kWh of cumulative discharge energy, 89% more than continuous fast charging. These results establish lifetime-aware MS-FC as a practical strategy for balancing charging speed, degradation, and second-life value in commercial lithium-ion batteries.
SN - 2313-0105
ER -