( Invited ) Nanocellulose Batteries

Cellulose is the most abundant biopolymer on the planet. I will give an overview of our published work on nanotechnologies based on cellulose nanomaterials, with a focus on assembly and functionalization strategies of wood-derived nanocellulose. I will then discuss the use of nanocellulose in battery applications, in both aqueous and solid-state systems. In particular, I will describe the synthesis–property–application relationships of nanocellulose-based nanochannels and their use in aqueous batteries (e.g., Zn-ion batteries). I will further present a general design strategy for achieving one-dimensional (1D), high-performance polymer solid-state ion conductors through molecular channel engineering, demonstrated via Cu²⁺ coordination of cellulose nanofibrils. Cellulose nanofibrils themselves are not ionically conductive; however, by opening molecular channels between cellulose chains through Cu²⁺ coordination, we enable Li-ion conductivity. This enhanced conductivity arises from a unique Li⁺ hopping mechanism that is decoupled from polymer segmental motion. Benefiting from this decoupling, the cellulose-based ion conductor exhibits multiple advantages, including a high transference number (0.78 vs. 0.2–0.5 in other polymers), low activation energy (0.19 eV), and a wide electrochemical stability window (4.5 V) that accommodates both Li-metal anodes and high-voltage cathodes. Furthermore, we demonstrate this 1D ion conductor not only as a thin, high-conductivity solid-state electrolyte, but also as an effective ion-conducting additive for solid cathodes, providing continuous ion-transport pathways with a low percolation threshold (Nature, 2021).