Electrochemical cell cyclability

The electrochemical fluorescence switching from a patternable poly(l,3,4-oxadiazole) thin film has been assessed [46]. The high solubility of the polymers enables a simple fabrication of an electrochemical cell, which shows a reversible fluorescence switching between dark and bright states with a maximum on/off ratio of 2.5 and a cyclability longer than 1000 cycles. The photochemical cleavage of the oxadiazole in the poly(arylene-l,3,4-oxadiazole) allows a photo-patterning of the film upon exposure to UV source. 

An electrochromic display (ECD) is basically an electrochemical battery where the cyclable energy output is revealed by a colour change. Similarly to any electrochemical cell, the typical configuration of ECDs involves, in sequence, the electrochromic electrode (for instance a WO 3 film deposited on an ITO-coated glass), an electrolyte and a counter-electrode. The electrochromic electrode provides the colour changes while the electrolyte allows the ionic transport and the counter-electrode assures the electrochemical balance. 

Manganese dioxide, Mn02, (MDO) is a widely used as material in primary electrochemical cells. It is the positive electrode of the zinc-MnOa cell, invented in 1866 by the French engineer Georges-Lionel Leclanche [11]. Li-MnOa battery was developed by Sanyo in 1975 [12] as low-power supplies for watches, calculators and memory backups. The poor cyclability of MDOs observed at that time [13] has been improved by preparing composite dimensional manganese oxides (CDMOs) for the development of flat-type secondary batteries. Table 6.2 lists the chemical formula of selected Li-Mn-O compounds used in Li batteries. 

The figure of merit (FOM) for lithium cycling efficiency [24] also is often used to evaluate the cyclability of a lithium cell. The FOM is defined as the number of cycles completed by one atom of lithium before it becomes electrochemically inactive. Equation (2) is derived from the above definition. 

Lazzari, M., and Scrosati, B. (1980). Cyclable lithium organic electrolyte cell based on 2 intercalation electrodes. J. Electrochem. Soc., 127. pp. 773-774. 

S. Menkin, D. Golodnitsky, E. Peled, Artificial solid-electrolyte interphase (SEI) for improved cyclability and safety of lithium-ion cells for EV applications, Electrochem. Commun. 2009, 11, 1789-1791. 

Further understanding of the effect of SEl formation on the cyclability of silicon-based anodes. Electrolytes and additives that can produce a stable SEl layer need to be developed. In situ SEM of working electrochemical test cells could be a very useful tool to directly observe the formation and evolution of SEl layers. 

The capability of polypyrrole to be reversibly doped and dedoped by electrochemical methods makes this electroactive material adequate for the construction of rechargeable batteries [181-185]. The electroactive polymer can be either the anode or the cathode of the cell, although construction of anodes is most common, due to difficulties in inserting negative charges into polyheterocycles. Technical factors such as cyclability, energy density, and stability have to be optimized in the future, before commercial application of polypyrrole-based batteries. 

Certainly the concept of a polymer battery is very attractive in terms of the various interesting applications that such a unique electrochemical power source could offer. However, the electrochemical doping processes of polymer are affected by diffusion-controlled kinetics which seriously limit the cyclability and stability of a polymer-based cell. For the purpose of clarity non-aqueous and aqueous systems will be discussed separately. 

Lazzari M, Scrosati B (1980) A cyclable lithium organic electrolyte cell based on two intercalation electrodes. J Electrochem Soc 127(3) 773-774. doi 10.1149/l.2129753... 

Takahashi M, Otsuka H, Akuto K, Sakurai Y (2005) Confirmation of long-term cyclability and high thermal stabihty of LrFeP04 in prismatic lithium-ion cells. J Electrochem Soc 152 ... 

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