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.
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.
In the last years, many strategies have been developed to benefit from oxygenic photosynthesis in the present context of renewable energies. To achieve this, bioelectricity may be produced by using photosynthetic components involved in anodic or cathodic compartments. In this respect, harvesting photosynthetic electrons from living biological systems appears to be an encouraging approach. However it raises the question of the most suitable electrochemical device. In this work, we describe and analyze the performances of an electrochemical device based on a millimeter sized well involving a gold surface as a working electrode. Photocurrents were generated by suspensions of Chlamydomonas reinhardtii algae using quinones as mediators under different experimental conditions. Chronoamperometry and cyclic voltammetry measurements gave insight into the use of this device to investigate important issues (harvesting and poisoning by quinones, photoinactivation…). Furthermore, by introducing a kinetic model originally developed for homogeneous catalytic systems, the kinetics of the electron diverting from this system (Chlamydomonas reinhardtii algae + 2,6-DCBQ + miniaturized setup) can be estimated. All these results demonstrate that this experimental configuration is suitable for future works devoted to the choice of the best parameters in terms of long lasting performances.
Among all the chemical and biotechnological strategies implemented to extract energy from oxygenic photosynthesis, several concern the use of intact photosynthetic organisms (algae, cyanobacteria…). This means rerouting (fully or partially) the electron flow from the photosynthetic chain to an outer collecting electrode thus generating a photocurrent. While diverting photosynthetic electrons from living biological systems is an encouraging approach, this strategy is limited by the need to use an electron shuttle. Redox mediators that are able to interact with an embedded photosynthetic chain are rather scarce. In this respect, exogenous quinones are the most frequently used. Unfortunately, some of them also act as poisoning agents within relatively long timeframes. It thus raises the question of the best quinone. In this work, we use a previously reported electrochemical device to analyze the performance of different quinones. Photocurrents (maximum photocurrent, stability) were measured from suspensions of Chlamydomonas reinhardtii algae/quinones by chronoamperometry and compared to parameters like quinone redox potentials or cytotoxic concentration. From these results, several quinones were synthesized and analyzed in order to find the best compromise between bioelectricity production and toxicity.
Manganese oxide LiMn2O4 (LMO) is one of the most promising cathode materials because it benefits from the low cost and availability of manganese, a high electrochemical stability, and a neutral environmental impact. In the same vein, the full or partial replacement of lithium salt in electrolyte by a more available and less expensive potassium salt contributes to reducing the environmental impact of batteries. Herein, the impact of the partial or total replacement of LiPF6 by KPF6 in a binary mixture of alkyl carbonate (EC/EMC) for LMO/graphite full battery is reported. The physicochemical properties of the electrolyte and its consequence on the kinetic and thermodynamic intercalation controls of each cation on cyclability are explored. Without protection with an additive, at a high current density (1 C), the nonselective intercalation of the two cations induces an optimum observed with an equimolar salt composition (0.5 m LiPF6 + 0.5 m KPF6), whereas in the presence of 5% of fluoroethylene (FEC), the replacement of part of the lithium is achievable without significant loss of performance. However, LMO/Gr cycling seems to depend on the discharge current density.
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