The Role of Pre-Lithiation in Activated Carbon/Li4Ti5O12 Asymmetric Capacitors

Pre-lithiation is a method that has been demonstrated to avoid the sudden cell voltage drop/rise during the charge/discharge in Li4Ti5O12 (LTO) anode and to compensate the energy loss of the first cycle resulting from the high initial potential of activated carbon (AC) cathode in lithium ion capacitors (LICs). However, the present pre-lithiation practices are largely empirical and lack of theoretical guidance. In the present study, we show from a theoretical perspective that the optimal pre-lithiation capacity range is closely related to the mass ratio (r) between the cathode and anode, and initial potential of AC cathode in a LIC. The optimal pre-lithiation capacity for the AC/LTO asymmetrical capacitor with a mass ratio of r = 2 and AC open circuit potential of 3.0 V is 34 ≤ Cpl ≤ 102mA hg−1. The theoretical prediction agrees well with the experimental data. This work promises to provide a practical guideline for optimizing the pre-lithiation level for a variety of LICs or LIBs systems.