Capacity fade of high-energy Li[Ni0.8Mn0.1Co0.1]O2/Graphite lithium-ion battery as affected by cell mechanical constraint and subsequent stresses

Abstract

Demand for a high energy density in electric vehicles is increasing, and thus, high-Ni-content cathodes have recently been increasingly used. However, cyclic degradation is an issue in high-Ni Li-ion batteries, especially in battery packs. The packing pattern plays a key role in the energy degradation and thermal behaviour of the final battery products. In this study, the effects of preloading, current rate, and environment temperature on the capacity fading of Li-ion batteries are experimentally investigated, and the corresponding mechanisms are discussed. The experimental uncertainty of capacity fading, resistance, and swelling force are 9.4%, 8.9%, and 2.8%, respectively. The results show that, when the cell is tested at 45 °C, the capacity loss is approximately ∼4.2 times that at 25 °C after 720 cycles. The current rate also plays a key role in the life of the cell; the estimated life is 860 and 1942 cycles for 1 C and 1/3 C, respectively. The most important finding is that an increase in the preloading can lengthen the life of lithium-ion cells. When the preloading is varied from 0 N to 1000 N at intervals of 250 N, the cell life span is estimated to be 1942, 1678, 2063, 2083, and 2421 cycles, respectively. In addition, our battery has certain advantages in terms of capacity degradation such that the required raw materials and hazardous waste of the battery can be reduced. Finally, the module is tested to estimate its capacity and constrained force evolution. Thus, the results of this study can guide the development and design of cell packing patterns and further investigations in this field.