Silicon and silicon oxide: Investigation of full cells, binder additive, and pre-lithiation for Li-ion batteries

Author(s): Dsouza, Macwin Savio | Advisor(s): Meng, Ying Shirley | Abstract: The advent of electric vehicles has uncovered the true potential for lithium-ion batteries (LIBs) however existing technology, can achieve a maximum energy density of ~ 300 Wh/kg. In order to promote the global use of electric vehicles, it is necessary to achieve g 400 Wh/kg which can enhance the driving range and in turn lower the cost. Si-based alloy anode is a promising alternative compared to graphite, due to its higher specific capacity. However, severe volume change (g 300 %) during lithiation, currently hinders its commercial application. The effect of the volume expansion can be largely mitigated by efficient binder formulations and novel silicon oxide-based chemistries. However, the understanding must be translated into full-cell configurations also. In this work, first, the stability of the full cells is explored using Si anode coupled with NMC111 cathode. Our measurements indicate that capacity degradation is aggravated due to overcharging of the cathode. Preventive action to eliminate this overcharge rendered ~ 30 % increase in capacity retention. Second, to achieve improved coulombic efficiency (CE) g 99% and larger capacity retention, Ferritin, a protein, was incorporated as a binder additive. Attractive properties such as self-healing, flexibility, and rigidity which can sustain the structural integrity of the anode allowed for effective half-cell testing. Last, tackling the volume expansion was sought by use of silicon oxide (SiOx) as the anode material. Pre-lithiation using stabilized lithium metal powder (SLMP) was also demonstrated to overcome low first cycle CE.