The active reuse of automotive lithium-ion batteries (LIBs) no longer utilized in electric vehicles for onboard applications is an effective way to achieve carbon neutrality. However, the safety of used LIBs, whose chemical composition of components has changed from that of new ones due to degradation, is still unknown, and the relationship between degradation and safety needs to be understood. The purpose of this study is to clarify the effect of degradation on the thermal stability of the battery by numerical simulation for LiNi_0.8Co_0.1Mn_0.1O₂ (NCM811)/graphite battery using high-Ni layered oxide NCM811, which has recently attracted attention as a high-capacity positive electrode. The numerical simulation was employed to clarify the effect of degradation on the thermal stability of the battery. After degradation, the temperature at which the thermal runaway starts increased by 15 °C compared to the initial batteries, indicating that the thermal stability as a battery has improved. It is because the heat generated by the positive electrode near 200 °C, which triggers thermal runaway of batteries, has decreased due to battery degradation.

In this paper, we propose voltammetry for determining amino acidity in Japanese sake. The measurement principle of this voltammetric method is based on a concept of acid-base back titration and a decrease of cathodic prepeak current of 3,5-di-tert-butyl-1,2-benzoquinone (DBBQ) caused by surplus HCl, which is obtained by the neutralization between excess HCl and amino acids in Japanese sake. In the comparisons of amino acidities in Japanese sakes (n = 10) obtained by this voltammetric method and the official titration, called the ethanol additional method, the correlation coefficient (r) was 0.946, indicating that the amino acidities in Japanese sakes by both methods were essentially the same.

Due to the abundance and low cost of sodium, sodium-ion batteries have received renewed attention in large-scale applications. At present, the primary task is to explore a new generation of cathode materials with excellent performance. Herein, ascorbic acid was used as a carbon source, Na₂Fe_0.85Mg_0.15PO₄F/C (NFMPF/C) and Na₂Fe_0.8Mg_0.15Ni_0.05PO₄F/C (NFMNPF/C) cathode materials were prepared by conventional solid-state reaction method on the basis of Na₂FePO₄F/C (NFPF/C). The electrochemical performance of the cathode material was improved by doping Mg and Ni on the Fe site, which was confirmed by the volt-ampere characteristic test and charge-discharge test. Compared with NFPF/C, the electrochemical performance of NFMPF/C has been greatly improved. After further doping of Ni, NFMNPF/C shows a stable discharge capacity, which can still maintain 91.3 % of the initial specific capacity after 50 cycles at 0.1 C-rate, while the rate capability shows a great improvement. The optimized NFMNPF/C sample can deliver a specific discharge capacity of 53 mAh/g at 5 C-rate. In general, the simple doping of NFPF/C optimizes the cycle life and rate capability at the same time. As a low-cost cathode material, this study provides more possibilities for the development of sodium-ion batteries.

The redox processes of the self-assembled monolayers (SAMs) of alkylthiolated viologens on Au electrodes are largely determined by oxidation-state-dependent binding of electrolyte anions to the viologen moiety in an aqueous solution. In this paper, we give an answer to a question: what if the SAM-forming molecule has a covalently-attached intermolecular anionic site? We used the results of the voltammetric measurements for a SAM of a viologen with a covalently-attached sulfonate group, 1-(10-mercaptodecyl)-1′-(3-sulfonatopropyl)-4,4′-bipyridinium bromide (HS-C10-V-C3-SO₃⁻ bromide salt), and examined the effect of intramolecular ion binding on the redox behavior. We found the coexistence of two distinct types of redox couples: one with a viologen moiety, which binds always to the sulfonate group, and the other with a moiety, which catches and releases an electrolyte anion from the solution upon redox. We deciphered rather complicated behavior and discussed the implications.

3,6-diphenyltetrazine (DPT) is an electron-deficient π-conjugated molecule with a perfectly planar structure and high crystallinity. In this study, discharge-charge tests of crystalline DPT as a cathode material for sodium ion batteries were conducted. DPT showed an initial reversible capacity of 102 mAh/g (theoretical capacity 114 mAh/g), corresponding to one electron reaction. The plateau of the discharge-charge profiles was observed at 1.9–2.1 V vs. Na/Na⁺. According to the ex-situ XRD, FT-IR, and XPS measurements to investigate the discharge-charge mechanism, the redox center was identified as the conjugated tetrazine ring. DPT was in a crystalline form in both the charged and discharged state and indicated the potential as a reversible Na ion host.