Fast and Controllable Prelithiation of Hard Carbon Anodes for Lithium-Ion Batteries

Abstract

As one of the potential alternatives to graphite, non-graphitizable hard carbon (HC) is of great interest for its high capacity and better rate performance. It is generally accepted that the higher capacity of HC comes from the random arrangement of single graphene layers, which provides extra voids to accommodate lithium.1 However, its practical application is hindered by a large irreversible capacity and thus low initial Coulombic efficiency (ICE) (<80%), which originates from the relatively large surface area, causing solid electrolyte interface (SEI) formation and side reaction between Li ions and surface functional groups. 2 Chemical prelithiation is one of the most effective method to compensate the Li loss and thus improve the ICE. It refers to the application of Li-containing reagents with strong reducing capabilities, which transfer the Li ions to the anode materials along with the redox reaction.3-4 The operation is rather simple and shows great potential for industrial application with a suitable roll-to-roll design. In this study, the chemical prelithiation reagent, Li-biphenyl-tetrahydrofuran, was evaluated for its prelithiation capability in hard carbon electrodes through the immersion method. The prelithiation extent can be easily controlled by tuning the reaction time. A short time of 30 s results in a high ICE of ~106% in half cell. The improvement of ICE was evaluated in full cells as well. When matched with a LiNi1/3Co1/3Mn1/3O2 cathode, the full cell with the prelithiated hard carbon anode exhibits a much improved ICE and cycling performance than those of the pristine full cell. SEM, XPS, and EIS analysis were conducted to investigate the SEI difference between pristine and prelithiated samples, and the prelithiation mechanism was proposed. References (1) Nagao, M.; Pitteloud, C.; Kamiyama, T.; Otomo, T.; Itoh, K.; Fukunaga, T.; Tatsumi, K.; Kanno, R. Structure Characterization and Lithiation Mechanism of Nongraphitized Carbon for Lithium Secondary Batteries. J. Electrochem. Soc. 2006, 153, A914-A919.(2) Xing, W.; Dahn, J. R. Study of Irreversible Capacities for Li Insertion in Hard and Graphitic Carbons. Journal of The Electrochemical Society 1997, 144, 1195-1201.(3) Scott, M. G.; Whitehead, A. H.; Owen, J. R. Chemical Formation of a Solid Electrolyte Interface on the Carbon Electrode of a Li‐Ion Cell. J. Electrochem. Soc. 1998, 145, 1506-1510.(4) Tabuchi, T.; Yasuda, H.; Yamachi, M. Li-doping process for LixSiO-negative active material synthesized by chemical method for lithium-ion cells. J. Power Sources 2005, 146, 507-509.