High energy density in ultra-thick and flexible electrodes enabled by designed conductive agent/binder composite

Abstract

Thick electrodes can increase incorporation of active electrode materials by diminishing the proportion of inactive constituents, improving the overall energy density of batteries. However, thick electrodes fabricated using the conventional slurry casting approach frequently exhibit an exacerbated accumulation of carbon additives and binders on their surfaces, invariably leading to compromised electrochemical properties. In this study, we introduce a designed conductive agent/binder composite synthesized from carbon nanotube and polytetrafluoroethylene. This agent/binder composite facilitates production of dry-process-prepared ultra-thick electrodes endowed with a three-dimensional and uniformly distributed percolative architecture, ensuring superior electronic conductivity and remarkable mechanical resilience. Using this approach, ultra-thick LiCoO2 (LCO) electrodes demonstrated superior cycling performance and rate capabilities, registering an impressive loading capacity of up to 101.4 mg/cm2, signifying a 242% increase in battery energy density. In another analytical endeavor, time-of-flight secondary ion mass spectroscopy was used to clarify the distribution of cathode electrolyte interphase (CEI) in cycled LCO electrodes. The results provide unprecedented evidence explaining the intricate correlation between CEI generation and carbon distribution, highlighting the intrinsic advantages of the proposed dry-process approach in fine-tuning the CEI, with excellent cycling performance in batteries equipped with ultra-thick electrodes.