Electrochemical capacitors, also called supercapacitors, store energy using either ion adsorption (electrochemical double layer capacitors) or fast surface redox reactions (pseudo-capacitors). They can complement or replace batteries in electrical energy storage and harvesting applications, when high power delivery or uptake is needed. A notable improvement in performance has been achieved through recent advances in understanding charge storage mechanisms and the development of advanced nanostructured materials. The discovery that ion desolvation occurs in pores smaller than the solvated ions has led to higher capacitance for electrochemical double layer capacitors using carbon electrodes with subnanometre pores, and opened the door to designing high-energy density devices using a variety of electrolytes. Combination of pseudo-capacitive nanomaterials, including oxides, nitrides and polymers, with the latest generation of nanostructured lithium electrodes has brought the energy density of electrochemical capacitors closer to that of batteries. The use of carbon nanotubes has further advanced micro-electrochemical capacitors, enabling flexible and adaptable devices to be made. Mathematical modelling and simulation will be the key to success in designing tomorrow's high-energy and high-power devices.

https://hal.archives-ouvertes.fr/hal-02417326/document

Materials for electrochemical capacitors

Due to their abundance, high strength and stiffness, low weight and biodegradability, nano-scale cellulose fiber materials (e.g., microfibrillated cellulose and bacterial cellulose) serve as promising candidates for bio-nanocomposite production. Such new high-value materials are the subject of continuing research and are commercially interesting in terms of new products from the pulp and paper industry and the agricultural sector. Cellulose nanofibers can be extracted from various plant sources and, although the mechanical separation of plant fibers into smaller elementary constituents has typically required high energy input, chemical and/or enzymatic fiber pre-treatments have been developed to overcome this problem. A challenge associated with using nanocellulose in composites is the lack of compatibility with hydrophobic polymers and various chemical modification methods have been explored in order to address this hurdle. This review summarizes progress in nanocellulose preparation with a particular focus on microfibrillated cellulose and also discusses recent developments in bio-nanocomposite fabrication based on nanocellulose.

Microfibrillated cellulose and new nanocomposite materials: a review

Hyperbranched polymers: from synthesis to applications

https://cdr.lib.unc.edu/downloads/js956h87r

Endocytosis of Nanomedicines

This review gives a survey on the latest most representative developments and progress concerning ionic liquids, from their fundamental properties to their applications in catalytic processes. It also highlights their emerging use for biomass treatment and transformation.

Ionic liquids and catalysis: Recent progress from knowledge to applications

Because of the high affinity of the carbonate ion (CO32-) to the hydrotalcite-like compounds or LDHs (layered double hydroxides), it was difficult to deintercalate carbonate ions and convert them into other LDHs with an easier anion-exchangeability. By treatment with dilute acids such as HCl, the conversion is limited, and, at higher concentrations, changes in shape and weight loss occurred. We found that the addition of NaCl dramatically enhanced the deintercalation of carbonate ions by dilute HCl solution (0.0025−0.005 N). It made the carbonate ions very rapidly deintercalate from the hydrotalcite-like compounds at 25 °C without any weight loss. Scanning electron microscopy (SEM) revealed that no morphological change occurred. Furthermore, by changing the HCl/NaCl ratio, it was possible to regulate the exchange ratio. Protonation of carbonate ions in the interlayer space and successive ion exchange with a large excess of Cl- ions was assumed to be the mechanism for this enhanced deintercalation.

Yoshiro Kaneko

Papers

Deintercalation of Carbonate Ions from a Hydrotalcite-Like Compound: Enhanced Decarbonation Using Acid−Salt Mixed Solution

A facile preparation of gel materials from a solution of cellulose in ionic liquid

Preparation of chitin/cellulose composite gels and films with ionic liquids

Weak gel of chitin with ionic liquid, 1-allyl-3-methylimidazolium bromide.

An acidic cellulose-chitin hybrid gel as novel electrolyte for an electric double layer capacitor