Shape-Conformable, Eco-Friendly Cellulose Aerogels as High-Performance Battery Separators

Abstract

The ubiquity of portable electronics underlines the importance of high-performance flexible metal-ion batteries and the necessity of their development. Considering their ecological footprint, the application of eco-friendly recyclable battery components has become the greatest challenge and the focal point of research. However, less attention has been devoted to the development of shapeconformable separators with minimal impact on the battery performance and the environment. It is therefore imperative to develop a rational design of next-generation eco-friendly separators with an optimized structure−performance relationship. In this work, a highly flexible and eco-friendly cellulose-nanofiber aerogel (CNF-AG) separator is developed and its dynamic behavior in battery cells is assessed. The tailored channel-like structure with a meso-and macroporosity of 99.5% and good mechanical stability results in superior performance to the commercial glass fiber (GF) membranes and other cellulose-based separators. Its structure with a well-connected pore network and affinity to carbonate-based and ionic liquid electrolytes realize an electrolyte uptake of 12 000%. Furthermore, an effective diffusion coefficient of 1.70 × 10 −10 m 2 s −1 , only 16% lower than that of the bulk electrolyte, yielded an ionic conductivity of 2.64 mS cm −1 . Assessing the CNF-AG in lithium-ion batteries (LIBs) revealed a stable interfacial resistance over time, reaching 380 Ω, one-third of that obtained for GF. Accordingly, superior electrochemical performance is observed, achieving good cycling stability up to 200 cycles. Moreover, its applicability in aluminum-ion batteries is demonstrated. The outstanding structure−performance relationships of the developed CNF-AG indicate its superiority as a shape-conformable biodegradable separator suitable for metal-ion batteries.

Single‐Ion‐Functionalized Nanocellulose Membranes Enable Lean‐Electrolyte and Deeply Cycled Aqueous Zinc‐Metal Batteries

“…[ 13 ] However, previously reported CNFs in the battery field only served as routine supporting materials for electronically decoupling anode and cathode, while liquid electrolytes containing metal salts are needed for applications. [ 14 ] Moreover, their potentials in ion‐transport selectivity, water activity inhibition, and dendrite suppression are yet to be explored in depth, which could partially rationalize the fact that the stable cycling of energy‐dense metal anodes is rarely reported in lean electrolyte and/or low metal inventory conditions. [ 15 ] Thus, we embarked on assessing the viability of practically rechargeable aqueous ZBs by a focus on fabricating functionalized CNFs.…”

Prelithiated, Multiscale Nickel Phosphate Octahydrate Platelets by a Tailored Nanoarchitectonics Approach

“…In order to assess the electrochemical performance, free-standing electrodes in form of aerogels via ice-templating were fabricated from the dispersions containing the platelets and DP2 (Figure S22). The platelets are thereby embedded in a highly porous matrix of the secondary phase that demonstrates a channel-like structure, 45 as illustrated in Figure 6d using the p-CNF aerogel as an example to show the typical morphological features. Compressing these aerogels into discs provides them with high mechanical stability while maintaining a very high porosity, beneficial for the complete wetting of the active material by the electrolyte, utilizing a higher fraction of the active material and facilitating the ion diffusion.…”

“…Compressing these aerogels into discs provides them with high mechanical stability while maintaining a very high porosity, beneficial for the complete wetting of the active material by the electrolyte, utilizing a higher fraction of the active material and facilitating the ion diffusion. The synergy of these aspects enhances the electrochemical performance compared to the xerogel counterpart. , …”

“…Alternatively, they were dehydrated first, preserving thereby their microstructure (Figure S24), prior to their compression for p-GO and p-CNF. The separator used is a novel CNF aerogel separator, known for its superior performance due to its high ionic conductivity and lower tortuosity . Moreover, a good interface between the layers is thereby achieved as the electrode disc is stacked upon the CNF aerogel separator during its ice-templating (Figure S25).…”

“…For the latter, 15 mL of each activated dispersion was filled in a polystyrene petri dish with a diameter of 5.5 cm, yielding self-assembled paper-like thin films. The dispersions with constant concentration were used to form aerogels by ice-templating, a process previously reported in detail . Briefly, the dispersion is thereby filled in a mold with the desired dimensions, here a cylinder with 8 mm as height and diameter was used for the hybrid materials and 15 mm diameter for the CNF separator production.…”