Cycle-Life Characterization of Automotive Lithium-Ion Batteries with LiNiO[sub 2] Cathode

Abstract

A set of lithium-ion cells containing a LiNi 0.8 Co 0.15 Al 0.05 O 2-based positive electrode and a graphite negative electrode were cycled nonintrusively at high power ͑5C rate͒ and elevated temperature ͑40°C͒. The aged cells were characterized at prescribed cycle numbers ͑up to 5250 cycles͒ by a three-electrode cell, capacity measurement, and electrochemical impedance spectroscopy ͑EIS͒. Excellent cyclability of these cells under typical hybrid-electric vehicle conditions is demonstrated by 18% capacity fade after 5250 cycles, and the discharge capacity shows a mainly parabolic behavior with the cycle number ͑N͒ ͑dependent on N 1/2 ͒ in the initial stage and a linear behavior ͑dependent on N͒ for subsequent cycles. Using a lithium reference electrode further reveals that the capacity fade during cycling is primarily caused by the positive electrode, where discharge capacity may be limited by a decrease in active lithium intercalation sites in the oxide particles. The increase in full-cell impedance with cycling is evident from the increase in midfrequency arc width ͑R w ͒, composed of charge-transfer kinetic resistance ͑R ct ͒ and Li + transport resistance through the solid electrolyte interphase ͑SEI͒, R SEI. More specifically, the cell-impedance rise comes mainly from the rising R ct and R SEI of the positive electrode. Based on individual electrode EIS spectra and equivalent-circuit analysis, it is found that the R SEI rise in the positive electrode is far more influential than the change in R ct. Therefore, property modification and thickening of the SEI layer of the positive electrode during cycling appear to be dominant factors in cell-impedance rise and power fade.

Accelerated energy capacity measurement of lithium-ion cells to support future circular economy strategies for electric vehicles

“…As a direct consequence of the cell being cycled at its maximum C-rate at zero degrees, the cells experiences an average 8.6% reduction in energy capacity. This result is consistent with a number of other publications that address the topic of Li-ion cell degradation and discuss the possible causality between low temperature, high current and the occurrence of lithium plating [53,54] and high temperature and high current and the growth of the solid electrolyte interphase 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 21 layer growth [54]. From Figure 9, similar conclusions for the 18650 cell type may be made.…”

A study of 40 Ah lithium ion batteries at zero percent state of charge as a function of temperature

“…Thus Zhang et al [39] have reported an activation energy of 4.3 kJ mol -1 for a fresh battery utilising a LiFePO 4 cathode; this increased to 20.9 kJ mol -1 after 300 cycles. However, an activation energy of 3.6 kJ mol -1 for a battery employing a LiNiO 2 cathode has also been reported [40], which decreased to 2.4 kJ mol -1 after 5250 cycles.…”

Duty-cycle characterisation of large-format automotive lithium ion pouch cells for high performance vehicle applications

“…One limitation of this research is that often, several studies use relatively simplistic constant current charge and discharge tests, often at different current rates and environmental temperatures as a means to estimate cycle life over a broad spectrum of operating conditions [5][6][7]. These tests are known to be largely unrepresentative of the day to day battery operation within an EV.…”