Expanding the charge/discharge voltage range of the high‑nickel cathode material NCM811 is one of the most cost-effective ways to increase the specific energy density of lithium-ion batteries (LIBs). However, carbonate-based electrolytes fail to adapted to the high-voltage environment is susceptible to objectionable oxidative decomposition. Therefore, two widely used electrolyte additives, lithium difluorophosphate (LiDFP) and adiponitrile (ADN), were combined to enhance the performance of LIBs at 4.5 V through their synergistic effect. The results show that the specific discharge capacity and capacity retention rate (CRR) of the Li||NCM811 half-cell with 5ADN electrolyte at 150 cycles under 4.5 V are 161.9 mAh/g and 76.5 %, significantly higher than the 118 mAh/g and 60.1 % of the standard electrolyte cell (STD). Similarly, graphite||NCM811 full-cell also has high specific discharge capacity and excellent CRR compared with STD cell. Further confirmed by physical analysis methods, the LiF-rich interfacial film between the cathode and the electrolyte called cathode electrolyte interphase (CEI) film, is more robust and denser. Thereby, the integrity of the cathode material is well protected, effectively inhibiting the dissolution of transition metal (TM) from the cathode material, and, ultimately, resulting in excellent high-voltage electrochemical performance of the battery. In addition, theoretical calculations show that LiDFP and ADN have larger adsorption energies for Li + and Co 4+ , which can effectively reduce the deposition of Co 4+ to the anode and increase the dissociation of lithium salts. This work provides a novel insight into the effective application of high-voltage electrolytes.
The vapor-phase nitrilation of dimethyl adipate (DMA) with ammonia (NH 3 ) is an environmentally benign route leading to adiponitrile (ADN) with great application value. In this study, the performance of HZSM-5 zeolites, widely used in industry as the solid acid catalysts, was investigated. It exhibits a strong correlation between the SiO 2 /Al 2 O 3 ratio (SAR) in HZSM-5 zeolites and the reactivity (both activity and selectivity). The influence of Al density closely related to the value of SAR on the reactivity of HZSM-5 was thus elucidated by mechanistic experiments. As a result, the introduction of Al element to the framework is beneficial to the activation of ester functionality, thus improving the activity, especially at a high liquid hourly space velocity (LHSV). However, a high Al density will lead to poor selectivity and deactivation due to too strong adsorption of esters and intermediates (e. g., amides). Herein, the balanced adsorption/desorption capability was reached on HZSM-5 with SAR as 631 (i. e., HZSM-5-631), which provides the best selectivity to nitriles (S ADN+MCP , 92.5 %) at a high single-pass conversion of DMA (C DMA , 98.0 %). Graphical The nitrilation of DMA over HZSM-5 with different SiO 2 /Al 2 O 3 was investigated, wherein HZSM-5 with SiO 2 /Al 2 O 3 of 631 exhibited excellent reactivity due to the balance of ester activation and amide intermediate desorption.
In the present study, the catalyst modified with alkaline oxide can enhance the selectivity to primary amines. However, the addition of alkaline oxide inevitably reduces catalytic activity. In this study, NiCo-NC@BaO-MFC catalyst derived from zeolitic imidazolate framework-67, Ba(CH 3 COO) 2 , and melamine formaldehyde (MF) resin was prepared and used for the hydrogenation of adiponitrile (ADN) to hexamethylene diamine (HDMA). The carbon layer obtained from the MF resin effectively prevents the interaction between barium (Ba) and the active center, thus improving target product selectivity without decreasing catalytic activity. The results of the density functional theory (DFT) calculation and characterization indicated that the effect of synergy between nickel (Ni) and cobalt (Co) bimetals induces an electron density growth on the Ni surface, bringing the d-band center toward the Fermi surface. Meanwhile, the high electron density of the active center compensates for the electron-deficient state of the carbon atom in –C N, thus improving the catalytic activity. Furthermore, it was found that the introduction of Ba promotes the formation of nucleophilic hydrogen anions, which facilitates the hydrogenation of 6-aminohexylimine (AHIM) to HDMA and inhibits the intramolecular condensation of AHIM, hence improving the selectivity to HDMA. The NiCo-NC@BaO-MFC catalyst gives 98.6 % ADN conversion and 97.2 % selectivity to HDMA in an alkali-free system.
危险品化学品经营许可证（带存储）