Nitrilase-catalysed desymmetrization of 3-substituted glutaronitriles to optically active 3-substituted 4-cyanobutanoic acid offers an attractive approach to access chiral β-substituted γ-amino acids, an important moiety in pharmaceuticals. In this study, we employed enzyme-substrate docking and alanine scanning to determine the key amino acid residues which have a positive effect on the activity and stereoselectivity of a nitrilase from Synechocystis sp. PCC6803 (SsNIT). Then, site-saturation mutagenesis and combinatorial mutagenesis of the positive amino acid residues (H141, P194, M197, I201 and F202) were performed, and a double mutant (P194A/F202V) and a triple mutant (P194A/I201A/F202V) with high activity and stereoselectivity were identified for desymmetrization of 3-substituted glutaronitriles to afford (S)-3-substituted-4-cyanobutanoic acids with a high space–time productivity of up to 488 g L−1 d−1. Molecular calculation suggests that the enzymatic activity improvement may be due to the enlargement of the substrate binding cavity. It is interesting that the stereoselectivity is enhanced simultaneously.
Lithium secondary battery with a wide working temperature range is crucial to boost its increasing applications in harsh circumstances. Suppressing excessive electrolyte decomposition at high temperatures while maintaining reasonable electrochemical kinetics at low temperatures is critical for wide-temperature electrochemical performance. Construction of high temperature stable electrode-electrolyte interface layer by electrolyte formulation is an effective strategy to prevent electrolyte from uncontrollable decomposition. On the contrary to conventional thinking, propylene carbonate (PC) bearing poor filming ability to suppress electrolyte decomposition is used in this work to promote decomposition of the single lithium difluoro(oxalate)borate (LiODFB) salt in the electrolyte, producing inorganic-rich interface layer with good structure stability over a wide temperature range. Glutaronitrile (GLN) is further utilized to minimize the decomposition of PC by expelling PC out of the solvation sheath of lithium-ion. The teamwork of LiODFB, PC, and GLN makes a synergistic contribution to building a high-temperature stable electrode-electrolyte interface layer at both LFP and MCMB electrodes. Based on the approach developed in this work, the temperature window is successfully expanded to the range of from -40 °C to 140 °C. Excellent electrochemical performance is exhibited by both LFP/Li and MCMB/Li cells from -20 °C to 100 °C in terms of reversible capacity and cyclic stability.
Lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) is widely employed in lithium metal batteries (LMB) owing to its capacity for efficiently mitigating the growth of lithium dendrites and enhancing the interface stability of lithium metal anodes. Unfortunately, LiTFSI frequently causes severe aluminum (Al) corrosion and leads to LMB failure. To address this issue, we conducted solvation structure design in the electrolyte using co-solvents such as 1,2-diethoxyethane, fluoroethylene carbonate and adiponitrile. Both experimental and computational evidences demonstrate that the co-solvents can regulate the solvation structure of electrolyte and promote the formation of more anion-rich internal solvation shells, ultimately enhancing the interfacial stability of Li anode and Al collector. When paired with high-loading LiFePO 4 cathode, the full cell exhibits a long-term lifespan (1000 cycles) and outstanding capacity retention (86.4 %). Even the full cell with stringent conditions of NMC811 (∼4.0 mAh cm −2 ), 50 μm thin Li (N/P = 2.5) and the optimized electrolyte still enables to output over 110 cycles and 80.0 % capacity retention. This work provides an efficacious and innovative strategy to stabilize Li metal anode and Al current collector through solvation structure regulation.
危险品化学品经营许可证（带存储）