Study on LiPO3@HC composite anodes with high capacity and rate capability for lithium ion capacitors

Abstract

Lithium-ion capacitors (LICs) could satisfy the increasing energy demand in current society owning to their high energy density and power density, as well as long cycle property. However, it is still a sharp challenge to find the ideal anode materials with low Li+ de-intercalation potential and fast electrochemical kinetics. Among common electrode materials, hard carbon (HC) is the preferred anode material for LICs, but the unsatisfying capacity and low Initial Coulomb Efficiency (ICE) hinder its practical application. One of the main limiting factors is the poor electrical conductivity. In this paper, lithium metaphosphate (LPO) is coated on the surface of HC by a solid-phase method to improve electrical conductivity as well as capacity. 3wt% LPO coated HC delivers an impressive reversible capacity of 515.3 mAh g−1 at 0.1 C and outstanding rate performance (120.6 mAh g−1 at 10 C). The pre-lithiation technology is adopted to enhance ICE. As a result, ICE can increase from 67.6% to 96.7% after prelithiation. Furthermore, LIC with pre-lithiated 3% LPO@HC anode and active carbon (AC) cathode demonstrates an energy density of 17.8 Wh kg−1 and a power density of 3.8 kW kg−1. The capacitance retention rate is 80.9% after 1000 cycles at 2 C, revealing a promising potential way for high-performance lithium ion capacitors.