Speaker
Description
With each year, the demand for Li-ion batteries is increasing – whether it is for industrial applications or electric vehicles – and improving battery performances remains one of the main goals of the research. Currently, switching to materials offering higher energy is one approach to achieve higher capacities. Silicon has gained much interest as anode material due to its high specific capacity of 3579 mAh/g compared to conventional graphite. However, pure silicon suffers from severe volume changes during lithiation, inducing mechanical stresses that can result in the failure of the battery.
Here, the lithiation mechanism and aging behavior of silicon anodes and LiNi0.8Co0.15Al0.05O2 (NCA) cathodes in multi-layer 5 Ah pouch cells were studied with neutron diffraction at the Wombat instrument at ANSTO. The batteries were fabricated on the research production line of the iwb institute at TUM to replicate the conditions of commercial cells as closely as possible. After formation and stabilization, uncylced cells were compared to a cylced cell at a state of health of 60 percent.
Due to aging, the capacity is decreased, which can be seen in the evolution of the cell parameters of NCA as well. Hereby, the c and a parameter of the aged cell are moving in a smaller window compared to the uncycled cell. Furthermore, it could be seen that the peak positions of NCA are shifting during the relaxation phase after charge indicating that the structure of NCA is changing.
