Calendar aging of a graphite/LiFePO4 cell

Abstract

Graphite/LFP commercial cells are stored under 3 different conditions of temperature (30°C, 45°C, and 60°C) and SOC (30, 65, and 100%) during up to 8 months. Several non-destructive electrochemical tests are performed at different storage times in order to understand calendar aging phenomena. After storage, all the cells except those stored at 30°C exhibited capacity fade. The extent of capacity fade strongly increases with storage temperature and to a lesser extent with the state of charge. From in-depth data analysis, cyclable lithium loss was identified as the main source of capacity fade. This loss arises from side reactions taking place at the anode, e.g. solvent decomposition leading to the growth of the solid electrolyte interphase. However, the existence of reversible capacity loss also suggests the presence of side reactions occurring at the cathode, which are less prominent than those at the anode. The analyses do not show any evidence about active-material loss in the electrodes. The cells do not suffer substantial change in internal resistance. According to EIS analysis, the overall impedance increase is 70% or less.

A Simplified Electrochemical and Thermal Aging Model of LiFePO4-Graphite Li-ion Batteries: Power and Capacity Fade Simulations

“…28,29 In the database concerning the LiFePO 4 -graphite system under study (high-power cell of nominal capacity 2.3 Ah, A123 Systems ANR26650m1), stress factors like temperature and SOC are being investigated for nine calendar operating conditions: three temperatures (30°C, 45°C, and 60°C) and three SOC (30%, 65%, and 100%). 28 Experimental repeatability is obtained by testing three cells for each operating condition.…”

Cycle Life of Commercial Lithium-Ion Batteries with Lithium Titanium Oxide Anodes in Electric Vehicles

“…Hence, in situ voltage measurement methods are necessary and used in this paper. The incremental capacity (IC) curve, i.e., dQ/dV = f(V) [10,11], and the differential voltage (DV) curve, i.e., dV/dQ = f(Q) [12,13], could provide huge information about the reactions inside the battery. Thus, based on the analysis of the IC and DV curves, the battery aging mechanism could be identified without battery destruction.…”

Calendar Aging of Lithium-Ion Batteries

“…However, these studies usually considered only a few storage SoCs or storage voltages. Most of the studies examined only three different values or fewer, [18][19][20][21][22][23][24][25][26][27][28] and there is one study that investigated five SoCs from 20% * Electrochemical Society Member. z E-mail: peter.keil@tum.de to 100%.…”