Segmented bi-material cathodes to boost the lithium-ion battery-capacitors

Lithium-ion battery-capacitor (LIBC) is a type of internal hybrid electrochemical energy storage device, bridging the gap between lithium-ion battery and electrical double-layer capacitor. In this work, we have designed a novel LIBC structure consisting of segmented bi-material (SBM) cathodes and pre-lithiated soft carbon (SC) anodes. The SBM cathodes havebeen formed by connecting the separated LiNi1/3Co1/3Mn1/3O2 (NCM) electrodes and activated carbon (AC) electrodes together in parallel within a cell, indicating lower electrochemical polarization and higher energy efficiency. The hybrid LIBC device with SBM cathodes exhibits high specific energy and superior rate capability. The hybrid pouch cell with 67 wt% NCM and 33 wt% AC possesses a specific energy of 173.3 Wh kg−1 at the specific power of 26.91 W kg−1, and even delivers 65.6% and 48.7% of its initial capacity discharged at the rate of 50C and 100C, respectively. Moreover, after 10,000 cycles at the charge/discharge rate of 10C, the hybrid device is still capable of maintaining more than 80% capacity retention and nearly 100% coulombic efficiency over the entire cycles. The LIBC with the NCM-AC segmented bi-material cathodes has a good prospect in the fast-charging and pulsed applications.