Scalable and high-rate ultra-thick cathodes enabled by a multifunctional ethyl cellulose additive

Abstract

Ultra-thick cathodes delivering >10 mAh cm− 2 with high-rate capability remain a central challenge due to severe electronic/ionic transport limitations and structural inhomogeneity introduced during fabrication. Here, we present a multifunctional ethyl-cellulose (EC) additive for conventional slurry processing that enables scalable manufacture of ultra-thick electrodes with exceptional electrochemical performance. A tiny amount of EC (<0.05 wt%) promotes uniform CNT dispersion via noncovalent (CH-π) interactions and drives selective adhesion to oxide surfaces through hydrogen bonding, yielding conformal in situ CNT coatings during slurry processing. The process is fully compatible with industrial roll-to-roll lines and was validated by continuous coating of >150 m of CNT-coated electrodes without loss of processability. In addition, EC suppresses carbon–binder migration during drying, a long-standing issue in slurry fabrication, and enhances electrolyte wettability, thereby lowering tortuosity-limited ionic resistance (i.e., ion-transport resistance from tortuous pores). This strategy enables defect-free electrodes with active-mass loadings up to 97.5 mg cm− 2 (19.5 mAh cm− 2 ) using only 0.5 wt % CNT. At 55 mg cm− 2 (≈11 mAh cm− 2 ), the electrodes retain 87% and 46% of their 0.1C capacity at 1C and 2C, respectively, demonstrating state-of-the-art performance among ultra-thick electrodes, and they maintain 73% capacity after 200 cycles in full-cell configurations. Li-metal pouch cells achieve a cathode-specific energy density of 734 Wh kg− 1 , demonstrating the industrial viability of the approach. This additive-assisted paradigm provides mechanistic insight into CNT–polymer–oxide interactions and offers a practical route to accelerate commercialization of high-areal-capacity electrodes at industrial scale.