(Invited) A Transversal Low-Cost Pre-Lithiation Strategy Enabling Ultrafast and Stable Lithium Ion Capacitors

Abstract

Lithium ion capacitors (LICs) are foreseen to be a complementary alternative of vital importance to current energy storage issues, coupling high energy density delivered by batteries with high power/long cycle life offered by supercapacitors. The prime issues in realising this technology are pre-lithiation and replacement of graphite electrodes that bring about energy gain at the expense of power. Herein we present an easy-to-scale-up approach, combining activated carbon with a highly efficient and industrially compatible low-cost sacrificial salt (dilithium squarate), that can be used as a lithium source for pre-lithiation. Paired with a hard carbon electrode tailored to perform at high rates, a LIC is demonstrated. Furthermore, the successful fabrication of a LIC pouch cell prototype with high energy at high power densities showing capacitance retention over 84% after 48000 cycles validates the strategy. This breakthrough may trigger the easy and low-cost fabrication of LICs and significantly reduce technological barriers to market growth and consolidation. Figure 1. Scheme representing the pre-metallation strategy followed in this work: Open circuit) MICs are represented by pristine HC as the negative electrode, each electrolyte corresponding to LIC, NIC and KIC with cations represented in dark blue (Li+), dark red (Na+) and dark green (K+) while anions are represented in brown (ClO4 -) and grey (PF6 -), and AC combined with the sacrificial salt -whose ions are represented in light colors- as the positive electrode; 1st charge) Cations from electrolyte and sacrificial salt are inserted into the HC while PF6 - anions are adsorbed into the AC surface; 1st discharge) While the excess of cations coming from the sacrificial salt are permanently inserted into the HC to compensate for the first cycle irreversibility (light colored cations), cations from electrolyte are reversibly inserted/deinserted as well as anions are adsorbed/deadsorbed allowing MICs to operate efficiently. Figure 1