Graphite//LiNi0.5 Mn1.5 O4 Cells Based on Environmentally Friendly Made-in-Water Electrodes

The performance of graphite//LiNi_0.5 Mn_1.5 O₄ (LNMO) cells, both electrodes of which are made using water-soluble sodium carboxymethyl cellulose (CMC) binder, is reported for the first time. The full cell performed outstandingly over 400 cycles in the conventional electrolyte ethylene carbonate/dimethyl carbonate-1 m LiPF₆ , and the delivered specific energy at the 100th, 200th, 300th, and 400th cycle corresponded to 82, 78, 73, and 66 %, respectively, of the initial energy value of 259 Wh kg^-1 (referring to the sum of the two electrode-composite weights). The good stability of high-voltage, LNMO-CMC-based electrodes upon long-term cycling is discussed and the results are compared to those of LNMO-composite electrodes with polyvinylidene fluoride (PVdF). LNMO-CMC electrodes outperformed those with PVdF binder, displaying a capacity retention of 83 % compared to 62 % for the PVdF-based electrodes after 400 cycles at 1 C. CMC promotes a more compact and stable electrode surface than PVdF; undesired interfacial reactions at high operating voltages are mitigated, and the thickness of the passivation layer on the LNMO surface is reduced, thereby enhancing its cycling stability.

Role of Oxygen Mass Transport in Rechargeable Li/O2 Batteries Operating with Ionic Liquids

The use of ionic liquid (IL)-based electrolytes and porous carbonaceous cathodes is today one of the most promising strategies for the development of rechargeable Li/O2 batteries. Enhancing Li/O2 battery cyclability at high discharge rate is a key issue for automotive applications. O2 reduction at a meso-macroporous carbon electrode in N-butyl-N-methyl pyrrolidinium bis(trifluoromethanesulfonyl)imide (PYR14TFSI):LiTFSI 9:1 is here investigated. The study demonstrates that oxygen electrode response in IL at high discharge currents is dominated by O2 mass transport in IL. A novel configuration of flow-Li/O2 battery that operates at high discharge rate is reported.

Polymer-Based Electrochemical Devices

Selected findings of ongoing investigations of variable light-transmission electrochromic devices using electronically conducting polymers as electrochromic materials are presented and discussed.

An obvious requisite for electrochromic windows is an all-solid configuration with polymer electrolyte; in this connection testing data of a new hybrid electrolyte based on a polymer network including a plasticizer are reported and discussed.

Performance of Polymer-Based Supercapacitors

Supercapacitors are now attracting much attention as an electric vehicle power source. The present study focuses on redox supercapacitors with electronically conducting polymers as electrode materials. Performance data of a symmetric supercapacitor based on p-doped poly(pyrrole), of an unsymmetric supercapacitor based on p-doped poly(pyrrole) and poly(3-methylthiophene), and of a symmetric sypercapacitor based on p- and n-doped poly(dithieno[3,4-b:3',4'-d]thiophene) are here compared.

Adsorption of Paracetamol and Acetylsalicylic Acid onto Commercial Activated Carbons

The adsorption of paracetamol (PAR) and acetylsalicylic acid (ASA) onto high-surface-area, commercial activated carbons was investigated at 26°C via adsorption isotherms at different pH values, including pH 1.5 to simulate conditions existing in the stomach. A wide-ranging characterization of the carbons, including analysis of their morphology and surface chemistry, was undertaken, with the actual surface areas of the carbons available for PAR and ASA adsorption being estimated by taking the molecular sizes of the drugs into account. This provided an understanding of the differences in the drug adsorption behaviour of the carbons.

The Effect of Ring Nitrogen Atoms on the Homolytic Reactivity of Phenolic Compounds: Understanding the Radical-Scavenging Ability of 5-Pyrimidinols

Six substituted 5-pyrimidinols were synthesized, and the thermochemistry and kinetics of their reactions with free radicals were studied and compared to those of equivalently substituted phenols. To assess their potential as hydrogen-atom donors to free radicals, we measured their O-H bond dissociation enthalpies (BDEs) using the radical equilibration electron paramagnetic resonance technique. This revealed that the O-H BDEs in 5-pyrimidinols are, on average, about 2.5 kcal mol(-1) higher than those in equivalently substituted phenols. The results are in good agreement with theoretical predictions, and confirm that substituent effects on the O-H BDE of 5-pyrimidinol are essentially the same as those on the Obond;H BDE in phenol. The kinetics of the reactions of these compounds with peroxyl radicals has been studied by their inhibition of the AIBN-initiated autoxidation of styrene, and with alkyl and alkoxyl radicals by competition kinetics. Despite their larger O-H BDEs, 5-pyrimidinols appear to transfer their phenolic hydrogen-atom to peroxyl radicals as quickly as equivalently substituted phenols, while their reactivity toward alkyl radicals far exceeds that of the corresponding phenols. We suggest that this rate enhancement, which is large in the case of alkyl radical reactions, small in the case of peroxyl radical reactions, and nonexistent in the case of alkoxyl radical reactions, is due to polar effects in the transition states of these atom-transfer reactions. This hypothesis is supported by additional experimental and theoretical results. Despite this higher reactivity of 5-pyrimidinols towards radicals compared to phenols, electrochemical measurements indicate that they are more stable to one-electron oxidation than equivalently substituted phenols. For example, the 5-pyrimidinol analogues of 2,4,6-trimethylphenol and butylated hydroxytoluene (BHT) were found to have oxidation potentials approximately 400 mV higher than their phenolic counterparts, but reacted roughly one order of magnitude faster with alkyl radicals and at about the same rate with peroxyl radicals. The 5-pyrimidinol structure should, therefore, serve as a useful template for the rational design of novel air-stable radical scavengers and chain-breaking antioxidants that are more effective than phenols.