Abstract
ABSTRACT
Cellulose nanofibers (CNFs) are emerging as sustainable polymer matrices for gel‐polymer electrolytes; however, their ion‐transport properties are limited by surface‐chemistry‐derived interactions. In this work, we demonstrate that a single, time‐controlled APTES functionalization step provides an effective and scalable route to enhance the ionic transport characteristics of CNF‐based gel–polymer electrolytes. The pristine and functionalized CNF membranes are imbibed with PF
6
−
‐based carbonate liquid electrolytes for both lithium (Li
+
)‐ and sodium (Na
+
) systems. By optimizing the functionalization duration, the ionic conductivity increases from ≈0.07 to 0.60 mS cm
−1
(Li
+
) and from ≈0.1 to 2.02 mS cm
−1
(Na
+
), accompanied by an increased apparent cation transference number, while preserving the fibrous morphology, mechanical integrity, and thermal stability. In LiFePO
4
|| Li half‐cells, the optimized A‐CNF electrolyte delivers stable rate capability and long‐term cycling beyond 1000 cycles, with reversible non‐monotonic capacity evolution associated with polarization relaxation, as supported by overpotential analysis and d
Q
/d
V
measurements. The A‐CNF electrolyte also enables efficient Na
+
transport in Na
3
V
2
(PO
4
)
3
|| Na half‐cells, showing minimal capacity loss (<5%) and narrow voltage hysteresis from 0.1C to 1C. These results establish single‐step APTES‐modified CNFs as a versatile and sustainable gel–polymer electrolyte platform for both lithium‐ and sodium‐ion batteries.