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Cellulose nanofibrils (CNFs) with carboxylated surface ligands are a class of materials with tunable surface functionality, good mechanical properties, and bio-/environmental friendliness. They have been used in many applications as scaffold, reinforcing, or functional materials, where the interaction between adsorbed moisture and the CNF could lead to different properties and structures and become critical to the performance of the materials. In this work, we exploited multiple experimental methods to study the water movement in hydrated films made of carboxylated CNFs prepared by TEMPO oxidation with two different surface charges of 600 and 1550 μmol·g -1 . A combination of quartz crystal microbalance with dissipation (QCM-D) and small-angle X-ray scattering (SAXS) shows that both the surface charge of a single fibril and the films' network structure contribute to the moisture uptake. The films with 1550 μmol·g -1 surface charges take up twice the amount of moisture per unit mass, leading to the formation of nanostructures with an average radius of gyration of 2.1 nm. Via the nondestructive quasi-elastic neutron scattering (QENS), a faster motion is explained as a localized movement of water molecules inside confined spheres, and a slow diffusive motion is found with the diffusion coefficient close to bulk water at room temperature via a random jump diffusion model and regardless of the surface charge in films made from CNFs.

The packing of cellulose nanocrystals (CNC) in the anisotropic chiral nematic phase has been investigated over a wide concentration range by small-angle X-ray scattering (SAXS) and laser diffraction. The average separation distance between the CNCs and the average pitch of the chiral nematic phase have been determined over the entire isotropic-anisotropic biphasic region. The average separation distances range from 51 nm, at the onset of the anisotropic phase formation, to 25 nm above 6 vol % (fully liquid crystalline phase) whereas the average pitch varies from ≈15 μm down to ≈2 μm as ϕ increases from 2.5 up to 6.5 vol %. Using the cholesteric order, we determine that the twist angle between neighboring CNCs increases from about 1° up to 4° as ϕ increases from 2.5 up to 6.5 vol %. The dependence of the twisting on the volume fraction was related to the increase in the magnitude of the repulsive interactions between the charged rods as the average separation distance decreases.

Silicon is a good alternative to conventional graphite anode but it has bad cycling and rate performance. To overcome these severe problems, extensively interconnected silicon nanoparticles using carbon network derived from ultrathin cellulose nanofibers were synthesized. Ultrathin cellulose nanofibers, an abundant and sustainable material, entangle each silicon nanoparticle and become extensively interconnected carbon network after pyrolysis. This wide range interconnection provides an efficient electron path by decreasing the likelihood that electrons experience contact resistivity and also suppresses the volume expansion of silicon during lithiation. In addition, Ultrathin cellulose nanofibers are carboxylated and therefore adhesive to silicon nanoparticles through hydrogen bonding. This property makes ultrathin cellulose the perfect carbon source when making silicon composites. As a consequence, it exhibits 808 mAh g −1 of the reversible capacity after 500 cycles at high current density of 2 A g −1 with a coulombic efficiency of 99.8%. Even at high current density of 8 A g −1 , it shows a high reversible discharge capacity of 464 mAh g −1 . Moreover, extensively interconnected carbon network prevents the formation of a brittle electrode with a water-based binder. Therefore, this remarkable material has a huge potential for LIBs applications. [ABSTRACT FROM AUTHOR]

• TEMPO-oxidized cellulose nanofiber (TOCNF) is suitable for versatile additive. • The TOCNF can cat as both reinforcing fiber and assistant binder in silicon anode. • Its carboxylic groups can make intimate adhesion with silicon via hydrogen bonding. • The addition of a small amount (1 wt%) of TOCNF exhibits good cycling performance. • Enhanced mechanical properties and stress distribution are attributed to the TOCNF. Silicon (Si) has been considered the most promising anode material for next-generation lithium-ion batteries due to its high theoretical capacity and natural abundance. However, the Si anode suffers from massive volume change, which results in challenging cycling performance. Many researches demonstrated that polymeric binder plays an important role to sustain the structural integrity of Si anodes. While most studies about the binder material have been focused on enhancing distinctive properties such as adhesive strength and mechanical property, it has been recently shown that binder distribution can help to improve electrochemical performance. Herein, we introduce TEMPO-oxidized cellulose nanofiber (TOCNF) as a versatile additive for the binder of silicon anode. The one-dimensional morphology of TOCNF efficiently reinforces the mechanical properties of the electrode. The TOCNF additive also contains carboxylic groups with sufficient flexibility to induce intimate interaction with Si via hydrogen bonding. Based on all of these beneficial features of TOCNF, the addition of ~ 1 wt% of TOCNF of the whole weight of silicon anode slurry significantly improved cycling stability. With pre-mixing, the resulting Si-TOCNF allows efficient water-based binder solution penetration, thus improving uniform binder distribution of electrode. Furthermore, the well-distributed binder protects silicon surface and forms a stable SEI layer. The current study suggests that the TOCNF additive facilitates uniform binder distribution in the electrode with enhanced mechanical properties, leading to improved cycling performance. Image, graphical abstract [ABSTRACT FROM AUTHOR]

In this work, cellulose nanofiber (CNF) derived carbon and reduced graphene oxide co-supported lithium iron phosphate (LiFePO 4 , LFP) nanocomposite was prepared by thoroughly mixing CNF with LFP first, followed by mixing again with graphene oxide (GO) to make well dispersed LFP nanoparticles anchored on graphene oxide, finally heating under an inert atmosphere. The ultrathin CNF was used as not only a carbon source but also an adhesive agent which can attach the LFP nanoparticles to the graphene sheets. The LFP nanoparticles were tightly attached to graphene sheets due to the hydrogen bond between GO and CNF. This nanocomposite exhibited good rate performance (discharge capacity of 168.9 mA h g−1 at 0.1C, and 90.3 mA h g−1 at 60C) and long-term cycle stability (~ 91.5% of initial capacity at 10C after 500 cycles) as cathode material for LIBs. The good rate and cycling performances could be attributed to the well-connected electron pathway derived from strongly adhering the LFP nanoparticles to reduced graphene oxide (rGO) and the facilitate electron transportation derived from carbonized CNF (cCNF) conductive network. The introduction of cCNF to LFP/rGO nanocomposite can be a promising strategy for further improve the performance of LFP cathode in LIBs. [ABSTRACT FROM AUTHOR]