RESUMEN
Due to the intrinsic flame-retardant, eutectic electrolytes are considered a promising candidate for sodium-metal batteries (SMBs). However, the high viscosity and ruinous side reaction with Na metal anode greatly hinder their further development. Herein, based on the Lewis acid-base theory, a new eutectic electrolyte (EE) composed of sodium bis(trifluoromethanesulfonyl)imide (NaTFSI), succinonitrile (SN), and fluoroethylene carbonate (FEC) is reported. As a strong Lewis base, the âC≡N group of SN can effectively weaken the interaction between Na+ and TFSI-, achieving the dynamic equilibrium and reducing the viscosity of EE. Moreover, the FEC additive shows a low energy level to construct thicker and denser solid electrolyte interphase (SEI) on the Na metal surface, which can effectively eliminate the side reaction between EE and Na metal anode. Therefore, EE-1:6 + 5% FEC shows high ionic conductivity (2.62 mS cm-1) and ultra-high transference number of Na+ (0.96). The Na||Na symmetric cell achieves stable Na plating/stripping for 1100 h and Na||Na3V2(PO4)3/C cell shows superior long-term cycling stability over 2000 cycles (99.1% retention) at 5 C. More importantly, the Na||NVP/C pouch cell demonstrates good cycling performance of 102.1 mAh g-1 after 135 cycles at 0.5 C with an average coulombic efficiency of 99.63%.
RESUMEN
Electrocatalytic oxidation of formaldehyde (FOR) is an effective way to prevent the damage caused by formaldehyde and produce high-value products. A screening strategy of a single-layer MnO2-supported transition metal catalyst for the selective oxidation of formaldehyde to formic acid was designed by high-throughput density functional calculation. N-MnO2@Cu and MnO2@Cu are predicted to be potential FOR electrocatalysts with potential-limiting steps (PDS) of 0.008 and -0.009 eV, respectively. Electronic structure analysis of single-atom catalysts (SACs) shows that single-layer MnO2 can regulate the spin density of loaded transition metal and thus regulate the adsorption of HCHO (Ead), and Ead is volcanically distributed with the magnetic moment descriptor -|mM - mH|. In addition, the formula quantifies Ead and |mM - mH| to construct a volcano-type descriptor α describing the PDS [ΔG(*CHO)]. Other electronic and structural properties of SACs and α are used as input features for the GBR method to construct machine learning models predicting the PDS (R2 = 0.97). This study hopes to provide some insights into FOR electrocatalysts.
RESUMEN
Solid polymer electrolytes are considered among the most promising candidates for developing practical solid-state sodium batteries. However, moderate ionic conductivity and narrow electrochemical windows hinder their further application. Herein, inspired by the Na+/K+ conduction in biological membranes, we report a (-COO-)-modified covalent organic framework (COF) as a Na-ion quasi-solid-state electrolyte with sub-nanometre-sized Na+ transport zones (6.7-11.6 Å) created by adjacent -COO- groups and COF inwalls. The quasi-solid-state electrolyte enables selective Na+ transport along specific areas that are electronegative with sub-nanometre dimensions, resulting in a Na+ conductivity of 1.30×10-4 S cm-1 and oxidative stability of up to 5.32 V (versus Na+/Na) at 25 ± 1 °C. Testing the quasi-solid-state electrolyte in Na||Na3V2(PO4)3 coin cell configuration demonstrates fast reaction dynamics, low polarization voltages, and a stable cycling performance over 1000 cycles at 60 mA g-1 and 25 ± 1 °C with a 0.0048% capacity decay per cycle and a final discharge capacity of 83.5 mAh g-1.
RESUMEN
Noncovalent modification of carbon materials with redox-active organic molecules has been considered as an effective strategy to improve the electrochemical performance of supercapacitors. However, their low loading mass, slow electron transfer rate, and easy dissolution into the electrolyte greatly limit further practical applications. Herein, this work reports dual molecules (1,5-dihydroxyanthraquinone (DHAQ) and 2,6-diamino anthraquinone (DAQ)) cooperatively confined in-between edge-oxygen-rich graphene sheets as high-performance electrodes for supercapacitors. Cooperative electrostatic-interaction on the edge-oxygen sites and π-π interaction in-between graphene sheets lead to the increased loading mass and structural stability of dual molecules. Moreover, the electron tunneling paths constructed between edge-oxygen groups and dual molecules can effectively boost the electron transfer rate and redox reaction kinetics, especially at ultrahigh current densities. As a result, the as-obtained electrode exhibits a high capacitance of 507 F g-1 at 0.5 A g-1 , and an unprecedented rate capability (203 F g-1 at 200 A g-1 ). Moreover, the assembled symmetrical supercapacitor achieves a high energy density of 17.1 Wh kg-1 and an ultrahigh power density of 140 kW kg-1 , as well as remarkable stability with a retention of 86% after 50 000 cycles. This work may open a new avenue for the efficient utilization of organic materials in energy storage and conversion.