Pyrene-4,5,9,10-tetraone (PTO), with a high theoretical capacity of 408 mAh·g⁻¹, is a promising candidate for rechargeable aqueous zinc-ion batteries (RAZIBs), but its zincated products during discharge process suffer from high solubility in electrolytes. Herein, a β-ketoenamine-linked two-dimensional (2D) covalent organic framework (COF) based on a 2,7-diaminopyrene-4,5,9,10-tetraone (4KT-BD) monomer and a 2,4,6-trihydroxy-benzene-1,3,5-tricarbaldehyde (Tp) node (4KT-Tp-COF) is synthesized to address the above issue. The well-designed 4KT-Tp-COF displays low solubility in 3 M Zn(CF₃SO₃)₂ owing to the favorable π–π stacking as well as extended structure. Besides, the ingenious structural design of the active molecule and the long-range ordered nano-channels alter the intramolecular electron distribution, which facilitates the ionic diffusion. Consequently, the 4KT-Tp-COF cathode exhibits a stable capacity of 181 mAh·g⁻¹ at 0.2 A·g⁻¹, superior rate capability of 139 mAh·g⁻¹ at 20 A·g⁻¹, and a long lifetime of 1000 cycles without capacity loss at 30 A·g⁻¹. Even at a low temperature of −20 °C, the electrode also performs an ultralong cycling life of 9000 cycles with a capacity of 106 mAh·g⁻¹ at 5 A·g⁻¹. The comprehensive characterizations of ex-situ analyses together with the theoretical calculations validate that the groups of C=O can contribute highly accessible redox-active sites for Zn²⁺ storage. The ultra-stable 4KT-Tp-COF cathode provides important insights for designing robust organic electrodes for sustainable and large-scale electrochemical energy storage.

Polymerization is a valid strategy to solve the dissolution issue of organic electrode materials in aprotic electrolytes. However, conventional polymers usually with amorphous structures and morphology’s influence on electrochemistry have rarely been studied. Herein, a hollow tubular poly phenyl pyrene-4,5,9,10-tetraone (T-PPh-PTO) organic cathode material was designed and synthesized based on the concentration-gradient of the precursor (PTO-Br₂) and asymmetrical internal diffusion during the reaction. The unique hollow structure endowed T-PPh-PTO with a short Li⁺ diffusion path accompanied by a high diffusion coefficient (D ${}_{{\mathrm{L}\mathrm{i}}^{+}}$ ≈ 10⁻⁸ cm²·s⁻¹). Thus, T-PPh-PTO presented a capacitance-dominated redox pseudocapacitance action with an outstanding rate performance (173 mAh·g⁻¹ at 2 A·g⁻¹) and high cycle stability (capacity retention ratio is 91.7% after 2,000 cycles). Our study leads to further developments in designing unique organic structures for energy storage.

Aqueous ammonium-ion battery (AAIB) has attracted much attention due to its low cost, safety, and environmental friendliness, but its electrode materials have many limitations. Here, alloxazine (ALO) is introduced as the anode for the AAIB. With its pseudocapacitive effect and fast diffusion kinetics of NH₄⁺, ALO anode shows excellent rate performance with a specific capacity of 120 mAh/g at 40 C (10 A/g). The full battery is further fabricated by ALO anode and Prussian white analogs cathode. Its specific capacity can reach 110 mAh/g and it can work up to 10, 000 cycles with no obvious capacity fading at 20 C (5 A/g). In addition, the system delivers a high energy density of 122.5 Wh/kg and a power density of 5, 055 W/kg. This work broadens the application prospect of the AAIB.

Aqueous rechargeable batteries are a possible strategy for large-scale energy storage systems. However, limited choices of anode materials restrict their further application. Here we report phenazine (PNZ) as stable anode materials in different alkali-ion (Li⁺, Na⁺, K⁺) electrolyte. A novel full cell is assembled by phenazine anode, Na_0.44MnO₂ cathode and 10 M NaOH electrolyte to further explore the electrochemical performance of phenazine anode. This battery is able to achieve high capacity (176.7 mAh·g^-1 at 4 C (1.2 A·g^-1)), ultralong cycling life (capacity retention of 80% after 13,000 cycles at 4 C), and excellent rate capacity (92 mAh·g^-1 at 100 C (30 A·g^-1)). The reaction mechanism of PNZ during charge-discharge process is demonstrated by in situ Raman spectroscopy, in situ Fourier transform infrared (FTIR) spectroscopy, X-ray photoelectron spectroscopy (XPS) and density functional theory (DFT) calculations. Furthermore, the system is able to successfully operate at wide temperature range from -20 to 70 °C and achieves remarkable electrochemical performance.

The rechargeable Li-CO₂ battery has been receiving significant attention owing to its merits of high energy density and the efficient utilization of CO₂. However, the widely application is plagued by severe security risks, such as leakage, flammability and lithium dendrites growth due to the use of liquid organic electrolytes. Here, a composite solid state electrolyte consisting of polyethylene oxide (PEO) and 20 wt.% Li₇La₃Zr_1.4Ta_0.6O₁₂ (LLZTO) was prepared and first introduced into Li-CO₂ battery to solve the problems. The composite solid state electrolyte exhibited high ionic conductivity (1.03 × 10^-3 S·cm^-1 at 70 ℃), wide electrochemical window (5 V vs. Li⁺/Li), good mechanical properties and excellent flexibility. Ultimately, the Li symmetric cell with PEO/LLZTO composite solid state electrolyte can operate 1, 500 h at a current density of 0.1 mA·cm^-2. The assembled all-solid-state Li-CO₂ battery behaved a long cycle life of 70 cycles at a current density of 100 mA·g^-1 with fixed capacity of 1, 000 mAh·g^-1. Our work provides new perspective to develop rechargeable all-solid-state Li-CO₂ batteries.

In recent years, development of all-solid-state batteries has become a promising approach to improve the safety of batteries. Herein, we report the preparation of a new composite polymer electrolyte (CPE) for use in all-solid-state sodium ion batteries. The CPE comprising of poly(methacrylate) (PMA), poly(ethylene glycol) (PEG), α-Al₂O₃ with acidic surface sites, and NaClO₄ exhibited high ionic conductivity (1.46 × 10^-4 S·cm^-1 at 70 ℃), wide electrochemical stability window (4.5 V vs. Na⁺/Na), and good mechanical strength. With the introduction of the prepared CPE and Na₃V₂(PO₄)₃, the final all-solid-state sodium ion batteries showed good rate and cycle performance, with a high reversible capacity of 85 mAh·g^-1 when operated at 0.5 C (1 C = 118 mA·g^–1) and 94.1% capacity retention rate after 350 cycles at 70 ℃. Our work provides a novel solid electrolyte for the development of all-solid-state sodium ion batteries.

Transition metal dichalcogenide nanodots (NDs) have received considerable interest. We report a facile bottom-up synthetic route for MoS₂ NDs by using molybdenum pentachloride and L-cysteine as precursors in oleylamine. The synthesis of NDs with a narrow size distribution ranging from 2.2 to 5.3 nm, was tailored by controlling the reaction time. Because of its coating characteristics, oleyalmine leads to uniformity and monodispersity of the NDs. Moreover, the NDs synthesized have large specific surface areas providing active sites. Graphene possesses outstanding conductivity. Combining the advantages of the two materials, the 0D/2D material exhibits superior electrochemical performance because of the 2D permeable channels for ion adsorption, energy storage, and conversion. The as-prepared MoS₂/rGO (~2.2 nm) showed a stable capacity of 220 mAh·g^-1 after 10,000 cycles at the current density of 20 A·g^-1. Furthermore, a reversible capacity ~140 mAh·g^-1 was obtained at a much higher current density of 40 A·g^-1. Additionally, this composite exhibited superior catalytic performance evidenced by a small overpotential (222 mV) to afford 10 mA·cm^-2, and a small Tafel slope (59.8 mV·decade^-1) with good acid-stability. The facile approach may pave the way for the preparation of NDs with these nanostructures for numerous applications.

We report on the preparation of three kinds of Ni nanoparticles supported on carbon (Ni/C) and their application in the catalytic hydrolysis of ammonia borane (AB). Three Ni/C catalysts were prepared from a Ni metal-organic framework (Ni-MOF) precursor by reduction with KBH₄, calcination at 700 ℃ under Ar, and a combination of calcination and reduction, the products being denoted as Ni/C-1, Ni/C-2, and Ni/C-3, respectively. The structure, morphology, specific surface area, and element valence were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), nitrogen adsorption-desorption measurements, and X-ray photoelectron spectra (XPS). The results demonstrate that Ni/C-1 is composed of amorphous Ni particles agglomerated on carbon, Ni/C-2 is characteristic of crystalline Ni nanoparticles (about 10 nm in size) supported on carbon with Ni oxidized on the surface, while the surface of the Ni particles in Ni/C-3 is less oxidized. The specific surface areas of Ni-MOF, Ni/C-1, Ni/C-2, and Ni/C-3 are 1239, 33, 470, and 451 m²·g^-1, respectively. The catalytic hydrolysis of AB with Ni/C-3 shows a hydrogen generation rate of 834 mL·min^-1·g^-1 at room temperature and an activation energy of 31.6 kJ/mol. Ni/C-3 shows higher catalytic activity than other materials, which can be attributed to its larger surface area of crystalline Ni. This study offers a promising way to replace noble metal by Ni nanoparticles for AB hydrolysis under ambient conditions.