Evaluating Performance and Cycle Life Improvements in the Latest Generations of Prismatic Lithium-Ion Batteries

Abstract

During the last decade, the market interest for electrified vehicles has increased considerably alongside global climate initiatives. This has coincided with vast improvements in automotive-grade, lithium-ion battery performance. This has increased the range of battery electric vehicles and plug-in hybrids but lifetime remains a challenge. Ageing during fast charging is especially difficult to understand due to its non-linear dependence on charge rate, state-of-charge and temperature. We present results from fast charging of several energy-optimized, prismatic lithium-ion battery cell generations with an NMC/graphite chemistry through comparison of capacity retention, resistance and dQ/dV analysis. Changes in cell design have increased energy density by almost 50 % over six years of cell development and acceptable cycle life can be expected, even under fast charging, when restricting the usage of the available capacity. Even though this approach reduces the useable energy density of a battery system, this trade-off could still be acceptable for vehicle applications where conventional overnight charging is not possible. The tested cell format has been used for a decade in electrified vehicles. The ongoing development and improvement of this cell format by several cell manufacturers suggests it will continue to be a good choice for future vehicles.

Effect of WLTP CLASS 3B Driving Cycle on Lithium-Ion Battery for Electric Vehicles

“…The cells were subjected to both calendar and cycle ageing, varying SoC and temperature in the former case and C-rate, DoD and temperature in the latter case; it is found that the temperature is the main parameter that affects the capacity fade and resistance increases for both calendar and cycle ageing [16]. However, identifying the ageing of an electrochemical cell is particularly difficult to understand due to its non-linear dependence on charge rate, state-of-charge and temperature [17]. In this regard, an interesting representation of the link between causes and effects in terms of ageing (evaluated with two main macro effects: capacity fade and power fade) has been presented [13].…”