Low-Concentrated Lithium Hexafluorophosphate Ternary-based Electrolyte for a Reliable and Safe NMC/Graphite Lithium-Ion Battery.

Current commercial lithium-ion battery (LIB) electrolytes are heavily influenced by the cost, chemical instability, and thermal decomposition of the lithium hexafluorophosphate salt (LiPF6). This work studies the use of an unprecedently low Li salt concentration in a novel electrolyte, which shows equivalent capabilities to their commercial counterparts. Herein, the use of 0.1 M LiPF6 in a ternary solvent mixture of ethylene carbonate (EC), ethyl methyl carbonate (EMC), and 1,1,2,2-tetrafluoroethyl 2,2,2-trifluoroethyl ether (TFE) (3EC/7EMC/20TFE, by weight) is investigated for the first time in LiNi1/3Mn1/3Co1/3O2 (NMC111)/graphite pouch cells. In solution, the Li+ transport number and diffusion are governed by the Grotthuss mechanism, with transport properties being independent of salt concentration. The proposed electrolyte operates in a wide temperature window (0-40 °C), is nonflammable (self-extinguishing under 2 s), and shows adequately fast wetting (4 s). When incorporated into the NMC/graphite pouch cell, it initially forms a solid electrolyte interphase (SEI) with minimal gas formation followed by a comparable battery performance to standard LiPF6 electrolytes, validated by a high specific capacity of 165 mAh g-1, Coulombic efficiencies of 99.3%, and capacity retention of 85% over 700 cycles.

Investigation of photocurrents resulting from a living unicellular algae suspension with quinones over time.

Plants, algae, and some bacteria convert solar energy into chemical energy by using photosynthesis. In light of the current energy environment, many research strategies try to benefit from photosynthesis in order to generate usable photobioelectricity. Among all the strategies developed for transferring electrons from the photosynthetic chain to an outer collecting electrode, we recently implemented a method on a preparative scale (high surface electrode) based on a Chlamydomonas reinhardtii green algae suspension in the presence of exogenous quinones as redox mediators. While giving rise to an interesting performance (10-60 µA cm-2) in the course of one hour, this device appears to cause a slow decrease of the recorded photocurrent. In this paper, we wish to analyze and understand this gradual fall in performance in order to limit this issue in future applications. We thus first show that this kind of degradation could be related to over-irradiation conditions or side-effects of quinones depending on experimental conditions. We therefore built an empirical model involving a kinetic quenching induced by incubation with quinones, which is globally consistent with the experimental data provided by fluorescence measurements achieved after dark incubation of algae in the presence of quinones.

Redesigning the QA binding site of Photosystem II allows reduction of exogenous quinones.

Strategies to harness photosynthesis from living organisms to generate electrical power have long been considered, yet efficiency remains low. Here, we aimed to reroute photosynthetic electron flow in photosynthetic organisms without compromising their phototrophic properties. We show that 2,6-dimethyl-p-benzoquinone (DMBQ) can be used as an electron mediator to assess the efficiency of mutations designed to engineer a novel electron donation pathway downstream of the primary electron acceptor QA of Photosystem (PS) II in the green alga Chlamydomonas reinhardtii. Through the use of structural prediction studies and a screen of site-directed PSII mutants we show that modifying the environment of the QA site increases the reduction rate of DMBQ. Truncating the C-terminus of the PsbT subunit protruding in the stroma provides evidence that shortening the distance between QA and DMBQ leads to sustained electron transfer to DMBQ, as confirmed by chronoamperometry, consistent with a bypass of the natural QA°- to QB pathway.