Ann Cornell

Single-paper flexible Li-ion battery cells through a paper-making process based on nano-fibrillated cellulose

Recently, a need for mechanically flexible and strong batteries has arisen to power technical solutions such as active RFID tags and bendable reading devices. In this work, a method for making flexible and strong battery cells, integrated into a single flexible paper structure, is presented. Nano-fibrillated cellulose (NFC) is used both as electrode binder material and as separator material. The battery papers are made through a paper-making type process by sequential filtration of water dispersions containing the battery components. The resulting paper structure is thin, 250 μm, and strong with a strength at break of up to 5.6 MPa when soaked in battery electrolyte. The cycling performances are good with reversible capacities of 146 mA h g−1 LiFePO4 at C/10 and 101 mA h g−1 LiFePO4 at 1 C. This corresponds to an energy density of 188 mW h g−1 of full paper battery at C/10.

Ruthenium dioxide as cathode material for hydrogen evolution in hydroxide and chlorate solutions

Ruthenium Dioxide as Cathode Material for Hydrogen Evolution in Hydroxide and Chlorate Solutions

Selectivity between Oxygen and Chlorine Evolution in the Chlor-Alkali and Chlorate Processes

Chlorine gas and sodium chlorate are two base chemicals produced through electrolysis of sodium chloride brine which find uses in many areas of industrial chemistry. Although the industrial production of these chemicals started over 100 years ago, there are still factors that limit the energy efficiencies of the processes. This review focuses on the unwanted production of oxygen gas, which decreases the charge yield by up to 5%. Understanding the factors that control the rate of oxygen production requires understanding of both chemical reactions occurring in the electrolyte, as well as surface reactions occurring on the anodes. The dominant anode material used in chlorate and chlor-alkali production is the dimensionally stable anode (DSA), Ti coated by a mixed oxide of RuO2 and TiO2. Although the selectivity for chlorine evolution on DSA is high, the fundamental reasons for this high selectivity are just now becoming elucidated. This review summarizes the research, since the early 1900s until today, concerning the selectivity between chlorine and oxygen evolution in chlorate and chlor-alkali production. It covers experimental as well as theoretical studies and highlights the relationships between process conditions, electrolyte composition, the material properties of the anode, and the selectivity for oxygen formation.

Ruthenium based DSA® in chlorate electrolysis—critical anode potential and reaction kinetics ☆

Ruthenium based DSA®s have been investigated in chlorate electrolyte using rotating discs made from commercial electrodes. Measurements of the voltammetric charge, q*, and of iR-corrected polarisat ...

A Mathematical Model for the Electrochemical Pickling of Steel

In industrial electrolytic pickling, a steel strip with oxidized surfaces is passed through an aqueous electrolyte between a configuration of electrodes, across which a potential difference is appl ...

The effect of addition of chromate on the hydrogen evolution reaction and on iron oxidation in hydroxide and chlorate solutions

The addition of chromate to the electrolyte has been shown in previous papers to hinder almost completely the electroreduction of hypochlorite, while the hydrogen evolution reaction can still proce ...

Flexible Paper Electrodes for Li-Ion Batteries Using Low Amount of TEMPO-Oxidized Cellulose Nanofibrils as Binder

Flexible Li-ion batteries attract increasing interest for applications in bendable and wearable electronic devices. TEMPO-oxidized cellulose nanofibrils (TOCNF), a renewable material, is a promising candidate as binder for flexible Li-ion batteries with good mechanical properties. Paper batteries can be produced using a water-based paper making process, avoiding the use of toxic solvents. In this work, finely dispersed TOCNF was used and showed good binding properties at concentrations as low as 4 wt %. The TOCNF was characterized using atomic force microscopy and found to be well dispersed with fibrils of average widths of about 2.7 nm and lengths of approximately 0.1-1 μm. Traces of moisture, trapped in the hygroscopic cellulose, is a concern when the material is used in Li-ion batteries. The low amount of binder reduces possible moisture and also increases the capacity of the electrodes, based on total weight. Effects of moisture on electrochemical battery performance were studied on electrodes dried at 110 °C in a vacuum for varying periods. It was found that increased drying time slightly increased the specific capacities of the LiFePO4 electrodes, whereas the capacities of the graphite electrodes decreased. The Coulombic efficiencies of the electrodes were not much affected by the varying drying times. Drying the electrodes for 1 h was enough to achieve good electrochemical performance. Addition of vinylene carbonate to the electrolyte had a positive effect on cycling for both graphite and LiFePO4. A failure mechanism observed at high TOCNF concentrations is the formation of compact films in the electrodes.

A Coupled Electrochemical and Hydrodynamical Two-Phase Model for the Electrolytic Pickling of Steel

In industrial electrolytic pickling, a steel strip with oxidized surfaces is passed through an aqueous electrolyte between a configuration of electrodes, across which a potential difference is applied. The strip is thereby indirectly polarized, and electrochemical reactions at the strip surface result in the dissolution of the oxide layer and the evolution of hydrogen and oxygen bubbles. In this paper, we extend an earlier mathematical model for the electrochemical aspects of the process, which took account only of the liquid phase, to include the effect of the gas phase. The model is two-dimensional, steady-state and isothermal, and comprises five ionic species, the mixture velocity, pressure, and the gas fraction; numerical solutions of this model are then obtained. The results of the single and two-phase models are compared, and their implications for the actual pickling process are discussed.

Ruthenium-Based Dimensionally Stable Anode in Chlorate Electrolysis Effects of Electrolyte Composition on the Anode Potential

In this work the anodic reactions taking place on a dimensionally stable anode (DSA) in chlorate electrolyte have been investigated. Rotating disk electrodes were made from commercial RuO2-catalyze ...

Electrochemical Characterization of Electrically Induced Adhesive Debonding

Within the framework of this thesis, three innovative electrochemical devices have been studied. A part of the work is devoted to an already existing device, laminates which are debonded by the application of a voltage. This type of material can potentially be used in a wide range of applications, including adhesive joints in vehicles to both reduce the total weight and to simplify the disassembly after end-of-life, enabling an inexpensive recycling process. Although already a functioning device, the development and tailoring of this process was slowed by a lack of knowledge concerning the actual electrochemical processes responsible for the debonding. The laminate studied consisted of an epoxy adhesive, mixed with an ionic liquid, bonding two aluminium foils. The results showed that the electrochemical reaction taking place at the releasing anode interface caused a very large increase in potential during galvanostatic polarization. Scanning electron microscopy images showed reaction products growing out from the electrode surface into the adhesive. These reaction products were believed to cause the debonding through swelling of the anodic interface so rupturing the adhesive bond.The other part of the work in this thesis was aimed at innovative lithium ion (Li‑ion) battery concepts. Commercial Li-ion batteries are two-dimensional thin film constructions utilized in most often mechanically rigid products. Two routes were followed in this thesis. In the first, the aim was flexible batteries that could be used in applications such as bendable reading devices. For this purpose, nano-fibrillated cellulose was used as binder material to make flexible battery components. This was achieved through a water-based filtration process, creating flexible and strong papers. These paper-based battery components showed good mechanical properties as well as good rate capabilities during cycling. The drawback using this method was relatively low coulombic efficiencies believed to originate from side-reactions caused by water remnants in the cellulose structure. The second Li-ion battery route comprised an electrochemical process to coat carbon fibers, shown to perform well as negative electrode in Li-ion batteries, from a monomer solution. The resulting polymer coatings were ~500 nm thick and contained lithium ions. This process could be controlled by mainly salt content in the monomer solution and polarization time, yielding thin and apparently pin-hole free coatings. By utilizing the carbon fiber/polymer composite as integrated electrode and electrolyte, a variety of battery designs could possibly be created, such as three-dimensional batteries and structural batteries.