Sodium metal is a promising anode, but uneven Na deposition with a dendrite growth seriously impedes its application. Herein, a fibrous hydroxylated MXene/carbon nanotubes (h‐Ti3C2/CNTs) composite is ...designed as a scaffold for dendrite‐free Na metal electrodes. This composite displays fast Na+/electron transport kinetics and good thermal conductivity and mechanical properties. The h‐Ti3C2 contains abundant sodiophilic functional groups, which play a significant role in inducing homogeneous nucleation of Na. Meanwhile, CNTs provide high tensile strength and ease of film‐forming. As a result, h‐Ti3C2/CNTs exhibit a high average Coulombic efficiency of 99.2 % and no dendrite after 1000 cycles. The h‐Ti3C2/CNTs/Na based symmetric cells show a long lifespan over 4000 h at 1.0 mA cm−2 with a capacity of 1.0 mAh cm−2. Furthermore, Na‐O2 batteries with a h‐Ti3C2/CNTs/Na anode exhibit a low potential gap of 0.11 V after an initial 70 cycles.
A friend to sodium: A fibrous hydroxylated h‐Ti3C2/carbon nanotubes composite is designed as a scaffold for dendrite‐free Na metal electrodes. It displays fast Na+/electron transport kinetics, high sodiophilicity, and satisfactory thermal conductivity and mechanical properties.
A new facile and green solid exfoliation method using urea-assisted ball milling is reported here to prepare NH2-functionalized few-layer black phosphorus (BP) nanosheets. The thickness of the ...obtained nanosheets is about 2.15–4.87 nm. The NH2-BP nanosheets exhibit enhanced electrocatalytic hydrogen evolution reaction (HER) performance with an overpotential of 290 mV at −10 mA cm−2, a Tafel slope of 63 mV dec−1 and a turnover frequency of 3.21 s−1 at an overpotential of 290 mV, which drastically surpass those of the bulk BP. This electrocatalytic activity of NH2-BP nanosheets in alkaline electrolyte greatly outperforms that in acidic electrolyte, making it a promising metal-free HER catalyst.
Highly reversible, stable, and non‐dendritic metal anode (Li, Na etc.) is a crucial requirement for next‐generation high‐energy batteries. Herein, we have built a Li–Na hybrid battery (LNHB) based on ...Na plating/stripping, which features a high and stable coulombic efficiency of 99.2 % after 100 cycles, low voltage hysteresis (42 mV at 2 mA cm−2), and fast charge transfer. As a result of the Li+ electrostatic shield layer, the Na deposition showed cubic morphology rather than dendritic, even at high current density of 5 mA cm−2. The solvation/desolvation of Li+ and Na+ were modelled by density functional theory calculations, demonstrating the fast desolvation kinetics of Na+. Owing to the superior performance of the Na metal anode, the LNHB coupled with LiFePO4 cathode exhibited low voltage hysteresis and stable cycling performance that demonstrates its feasibility in practical applications.
Cubism: A highly reversible, stable and non‐dendritic Na metal anode with fast plating kinetics is utilized for building Li–Na hybrid batteries. The Li+ electrostatic shield layer facilitates that the Na deposition shows a cubic morphology rather than dendritic deposition in hybrid electrolyte. The Li‐Na hybrid battery exhibits superior electrochemical performance.
Electrochemical energy storage with redox‐flow batteries (RFBs) under subzero temperature is of great significance for the use of renewable energy in cold regions. However, RFBs are generally used ...above 10 °C. Herein we present non‐aqueous organic RFBs based on 5,10,15,20‐tetraphenylporphyrin (H2TPP) as a bipolar redox‐active material (anode: H2TPP2−/H2TPP, cathode: H2TPP/H2TPP2+) and a Y‐zeolite–poly(vinylidene fluoride) (Y‐PVDF) ion‐selective membrane with high ionic conductivity as a separator. The constructed RFBs exhibit a high volumetric capacity of 8.72 Ah L−1 with a high voltage of 2.83 V and excellent cycling stability (capacity retention exceeding 99.98 % per cycle) in the temperature range between 20 and −40 °C. Our study highlights principles for the design of RFBs that operate at low temperatures, thus offering a promising approach to electrochemical energy storage under cold‐climate conditions.
Hot stuff when it gets chilly: Redox‐flow batteries (RFBs) for energy storage at subzero temperatures would facilitate the use of renewable energy in cold regions. Such non‐aqueous RFBs with high volumetric capacity, high voltage, and excellent cycling stability between 20 and −40 °C have been developed with the porphyrin H2TPP as a bipolar redox‐active material and a Y‐zeolite–poly(vinylidene fluoride) ion‐selective membrane.
Direct monitoring of dendrite growth, hydrogen evolution, and surface passivation can enrich the chemical and morphological understanding of the unstable Zn/electrolyte interface and provide ...guidelines for rational design of Zn anodes; however, the on-line observation with high precision is hitherto lacking. Herein, we present a real-time comprehensive characterization system, including in situ atomic force microscopy, optical microscopy, and electrochemical quartz crystal microbalance (referred to as the “3M” system), to provide multiscale views on the semisphere nuclei and growth of bump-like dendrites and the potential-dependent chemical and morphological structures of passivated products in a mild acidic electrolyte. It is revealed that the poor interfacial properties can be attributed to the sparse nucleation sites and direct contact of Zn with the electrolyte. The 3M system further visualizes and confirms that the additive polyethylene glycol acts as a Zn2+ distribution promoter and physical barrier and merits stable electrochemical performance.
Quinones are promising electrode materials for lithium-ion batteries (LIBs), but their structure-electrochemical property relationship remains unclear. The aim of this study is to unravel the ...structural influence on the electrochemical properties of different quinones in LIBs. Through density functional theory calculations, redox potentials of 20 parent quinone isomers were examined, which revealed an increasing order of redox potentials as para-quinones < discrete-quinones < ortho-quinones. Two new methods were introduced to calculate and design organic electrode materials rationally. One is the vertical electron affinity in consideration of solvation effect, which was used to estimate the number of electron accommodation for quinones during lithiation. The other is a new index denoted as ΔA2Li used in para- and ortho-quinones, which was introduced to reveal the relationship between aromaticity and redox potential, establishing the theoretical basis for the design of analogous high-voltage organic electrode materials of LIBs.
Organic carbonyl compounds are promising electrode materials for high-performance lithium-ion batteries (LIBs), but generally suffer from poor cycling stability, low utilization, inferior rate ...performance, and relatively low reduction potential. In order to solve these problems, we report a dissolution-recrystallization method to prepare flexible, binder-free, and free-standing hybrid films of sodium 1,4-dioxonaphthalene-2-sulfonate and multiwalled carbon nanotubes (NQS/MWNTs) as high-performance cathode for rechargeable LIBs. The hybrid films demonstrate high utilization of NQS, stable cycling, and high-rate capability. The superior electrochemical performance is attributed to decreased size and high polarity of NQS, three-dimensional intertwined conductive network formed by MWNTs. Moreover, NQS/MWNTs show high initial reduction potential at 2.97 V, which is well explained via density functional theory (DFT) calculations. Meanwhile, the reversible redox mechanism of NQS/MWNTs during discharge/charge process is revealed by in situ infrared spectroscopy (IR) test and the stability of fully discharged product is further confirmed by DFT calculations. This study illustrates a facile method to build high-performance flexible rechargeable batteries with sustainable organic materials.
Benzoquinone (BQ)-based macrocyclic compounds have shown great potential as cathode materials for lithium-ion batteries (LIBs) owing to their high redox potential and specific capacity. However, such ...materials usually have complex structures, which impede the investigation of lithiation mechanisms. Herein, we take Calix4quinone (C4Q) molecule as an example to develop a viable mechanism investigation method for such materials. The lithiation profile of C4Q is determined by condensed Fukui function which provides the reaction sites and orders. A correction of redox potential is proposed by leaving out the ion-transfer effect during the redox reaction based on Gibbs free energy change. The redox potential obtained by this approach shows high consistency with the experimental results. Moreover, this method can also be well extended to study the lithiation mechanism of another BQ-based macrocyclic compound (Pillar5quinone). Our results are promising to more deeply understand the reaction mechanism and predict the redox potential of new BQ-based macrocyclic compounds for LIBs.
The lithiation mechanism of C4Q cathode has been revealed by redox potential correction and condensed Fukui function.
Organic carbonyl compounds show potential as cathode materials for lithium‐ion batteries (LIBs) but the limited capacities (<600 mA h g−1) and high solubility in electrolyte restrict their further ...applications. Herein we report the synthesis and application of cyclohexanehexone (C6O6), which exhibits an ultrahigh capacity of 902 mA h g−1 with an average voltage of 1.7 V at 20 mA g−1 in LIBs (corresponding to a high energy density of 1533 Wh kg−1C6O6
). A preliminary cycling test shows that C6O6 displays a capacity retention of 82 % after 100 cycles at 50 mA g−1 because of the limited solubility in high‐polarity ionic liquid electrolyte. Furthermore, the combination of DFT calculations and experimental techniques, such as Raman and IR spectroscopy, demonstrates the electrochemical active C=O groups during discharge and charge processes.
Six pack: Cyclohexanehexone (C6O6) is synthesized and applied as a cathode material in lithium‐ion batteries that exhibit an ultrahigh capacity of 902 mA h g−1 (1533 Wh kg−1). As a result of its limited dissolution, C6O6 shows relatively good cycling stability (a capacity retention of 82 % after 100 cycles at 50 mA g−1) in ionic liquid electrolyte.
