Balancing microcrystalline domains in hard carbon with robust kinetics for a 46.7 Wh kg−1 practical lithium-ion capacitor

Abstract

As a promising electrochemical energy storage system, lithium-ion capacitors (LICs) exhibit alluring theoretical merits of high energy density, high power density and long cycle life. However, most of the LIC cells can hardly surpass the practical energy density threshold of 30 Wh kg−1, which greatly hinders their employments in various energy-oriented fields. Anthracite shows great prospect as low-cost and abundant carbon precursor to prepare anode material with plentiful Li-ion anchoring sites for high performance LICs. In this work, a scalable low-temperature hydrothermal disordering strategy is proposed to achieve balanced structural modification of anthracite into short-ranged turbostratic carbon precursor, which further transforms into microcrystalline hard carbon (MHC) with high electrical conductivity (13065 S m−1) and substantially improved energy storage kinetics. A practical large-capacity LIC pouch cell is fabricated using MHC anode and activated carbon cathode to deliver a maximum gravimetric and volumetric energy density of 46.7 Wh kg−1 and 66.8 Wh/L based on the total weight of cell, outperforming the commercially available LIC products from relevant enterprises. Moreover, the cell reveals an exceptional capacity retention of 94.7 % after 10,000 cycles at high current density. The work herein would emerge as a universal and feasible protocol to fabricate high-end carbon electrode for practical LICs in numerous energy-intensive occasions.