Great Cycling Performance Research Articles

High‐Performance Asymmetric Li‐Ion Pseudocapacitors Based on Pyroprotein Nanowebs

AbstractModern industrial technologies require high power and energy storage devices with long‐term cycling stabilities; the electrochemical performances of these devices are mainly dependent on the active electrode materials and their energy storage mechanisms. In this study, nanoweb‐structured pyroprotein nanofibers (NW‐PNFs) were prepared from electrospun silk protein by pyrolysis. NW‐PNFs have an open macroporous structure formed by entangled nanofibers and numerous micropores originating from the amorphous pseudographitic microstructure of the nanofibers. In addition, they possessed a large number of heteroatoms (10.3 at. % oxygen and 5.2 at. % nitrogen). These material properties led to superior Li‐ion storage performances with high reversible capacity of about 1,050 mA h g−1 at 0.5 A g−1 and great cycling performance over 3,000 cycles. In particular, NW‐PNFs exhibited high rate capability even at the specific current of 50 A g−1, at which the high specific capacity of circa 400 mA h g−1 was achieved. Furthermore, asymmetric Li‐ion storage devices based on NW‐PNFs showed feasible electrochemical performances with a maximum specific energy of 235.7 Wh kg−1 at 188.6 W kg−1 and maximum power of 21,220 W kg−1 at 69.6 Wh kg−1.

Amorphous MoS3 Infiltrated with Carbon Nanotubes as an Advanced Anode Material of Sodium‐Ion Batteries with Large Gravimetric, Areal, and Volumetric Capacities

The search for earth‐abundant and high‐performance electrode materials for sodium‐ion batteries represents an important challenge to current battery research. 2D transition metal dichalcogenides, particularly MoS2, have attracted increasing attention recently, but few of them so far have been able to meet expectations. In this study, it is demonstrated that another phase of molybdenum sulfide—amorphous chain‐like MoS3—can be a better choice as the anode material of sodium‐ion batteries. Highly compact MoS3 particles infiltrated with carbon nanotubes are prepared via the facile acid precipitation method in ethylene glycol. Compared to crystalline MoS2, the resultant amorphous MoS3 not only exhibits impressive gravimetric performance—featuring excellent specific capacity (≈615 mA h g−1), rate capability (235 mA h g−1 at 20 A g−1), and cycling stability but also shows exceptional volumetric capacity of ≈1000 mA h cm−3 and an areal capacity of >6.0 mA h cm−2 at very high areal loadings of active materials (up to 12 mg cm−2). The experimental results are supported by density functional theory simulations showing that the 1D chains of MoS3 can facilitate the adsorption and diffusion of Na+ ions. At last, it is demonstrated that the MoS3 anode can be paired with an Na3V2(PO4)3 cathode to afford full cells with great capacity and cycling performance.

Boron nitride supported Ni nanoparticles as catalysts for hydrogen generation from hydrolysis of ammonia borane

We report on Ni nanoparticles supported on boron nitride spheres (BNSP) and sheets (BNSH) as catalysts for hydrogen generation via hydrolysis of ammonia borane (NH3BH3, AB). The Ni/BN catalysts were prepared through a redox replacement reaction. The structure, morphology, and chemical composition of the obtained samples were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) equipped with energy dispersive X-ray spectroscopy (EDX), and inductively coupled plasma emission spectroscopy (ICP). The characterization results showed that Ni nanoparticles were well dispersed on the BNSP and BNSH supports for the four Ni/BN catalysts prepared (Ni atomic contents of 6.8, 9.0, 9.2, and 12 wt%). The catalytic activity toward the hydrolysis of AB was found to correlate with the loading of the Ni/BN catalysts, which showed great cycle performance. Theoretical calculations revealed that BN sheets significantly influenced the electric character of Ni catalysts and thereby their catalytic properties.

Super long-life all solid-state asymmetric supercapacitor based on NiO nanosheets and α-Fe2O3 nanorods

Through a facile hydrothermal method at a mild temperature and a calcination process, we report the fabrication about the NiO nanosheets and α-Fe2O3 nanorods using nickel foam (NF) and carbon cloth (CC) as substrates. Analysis of data obtained from the electrochemical experiments show that NiO electrode possesses large areal capacitance (1.3Fcm−2 at 4mAcm−2). Also, α-Fe2O3 electrode delivers areal capacitance of 500mFcm−2 at current density of 4mAcm−2. Therefore, a high-performance all solid-state asymmetric supercapacitor (ASC) based on 3D sheet-like hierarchical NiO and α-Fe2O3 nanorods are designed and fabricated. New ASC can be cycled reversibly in a high voltage region ranging from 0 to 1.25V with high energy densities of 12.4Whkg−1 (power is 951Wkg−1) based on the total mass of active materials. Furthermore, the obtained data indicate that the fabricated NiO//α-Fe2O3 based supercapacitor device has a great cycle performance with 85% capacitance retention under 10,000 cycles. This work may help to open up new areas for fabrication of lightweight and low-cost materials for energy storage systems.

Template-free synthesis of Ni2P hollow microspheres with great photocatalytic and electrochemical properties

The hollow Ni2P microspheres were prepared using a facile one-step template-free solvothermal method. The products were characterized and the results showed that they were pure hexagonal Ni2P microspheres, made up of large amounts of Ni2P nanoparticles, and had an obvious inner space in the central of the microspheres. After being investigated, it was found that these Ni2P hollow spheres initially were some solid spheres, but after a specified time, they were converted to a hollow structure by an Ostwald ripening process, some even had a multi-wall hollow structure. Meanwhile, the as-prepared Ni2P hollow spheres showed a good photocatalytic degradation performance for Methylene Blue in aqueous solution. Electrochemical measurements turned out that the Ni2P hollow spheres have a great cycling performance. The initial discharge capacity capacity of is Ni2P hollow spheres up to 660 mAh g−1 and it always keep in about 300 mAh g−1 within 100 cycles at the current density of 100 mA g−1.

Organic electrode for non-aqueous potassium-ion batteries

Potassium-ion (K-ion) batteries can be an attractive alternative for grid-scale energy storage due to the abundance of K resources. For the first time, we designed and fabricated a non-aqueous K-ion battery (KIB) by employing 3,4,9,10-perylene–tetracarboxylicacid–dianhydride (PTCDA) as the cathode. The PTCDA electrode exhibits a high capacity of 131mAhg−1 in the potential range of 1.5–3.5V vs. K/K+, which corresponds to the insertion of two K ions per PTCDA molecule. The PTCDA cathode also shows great cycling performance, with a capacity retention of 66.1% over 200 cycles. Furthermore, K11PTCDA can be obtained when discharging PTCDA to 0.01V vs. K/K+, which delivers a high capacity of 753mAhg−1. The excellent electrochemical performance makes PTCDA a promising organic electrode based on K-ion chemistry for grid-scale energy storage.

Synthesis of SiGe-based three-dimensional nanoporous electrodes for high performance lithium-ion batteries

We demonstrate the synthesis of SiGe-based three-dimensional (3D) porous nanostructures via a template-assisted method. When tested as electrode in lithium-ion batteries, it exhibits a reversible capacity as high as 1311 mAh g−1 after 45 cycles at a current density of 4 A g−1. Even at a super high current rate of 16 A g−1, the electrode can deliver a stable capacity of about 1047 mAh g−1. The great cycling performance and superior rate capability can be attributed to the good electrical contact, fast electron transport and good strain accommodation of the 3D nanostructure of the porous electrode.

One step synthesis and capacitive performance of graphene nanosheets/Mn3O4 composite

By using KMnO4 as both the oxidant and Mn source in a modified Hummers’ method, a facile and economical procedure is proposed to synthesize graphene oxide/MnO2 composite. Then after annealing at 400°C, the graphene/Mn3O4 composite with 70.7wt.% Mn3O4 nanoparticles homogeneously anchored on each side of graphene nanosheets is obtained. The electrochemical performance of the graphene/Mn3O4 is investigated as a supercapacitor electrode material. It exhibits the high specific capacitance of 271.5Fg−1 at the current density of 0.1Ag−1 as well as great cycle performance. At the high current density of 10Ag−1, the capacitance retention even keeps about 100% after 20,000 cycles. The good electrochemical performance and the simple accessibility make this graphene/Mn3O4 composite a promising candidate as a supercapacitor electrode material.

Research on process of preparation and performance of iron phosphate as precusor of lithium iron phosphate

Lithium iron phosphate with the structure of olivine has many advantages: low price, environmentally friendly, great thermal stability and excellent cycle performance when used as the anode materials, making it one of the most promising anode materials. In this article, we used the precusor FePO4 pre-prepared to produce LiFePO4 and the performances were tested. The process of preparation of the precusor FePO4 were optimized and the reaction mechanism was probed into. The precusor FePO4 was prepared by the raw materials as follows: ferric nitrate, phosphoric acid and diammonium hydrogen phosphate, the temperature, PH, Fe/P and the time of reaction were considered. LiFePO4 was prepared by calcining the mixture of iron phosphate, lithium carbonate and glucose after mixed. The test of charge-discharge indicates that the sample of LiFePO4 holds the discharging voltage platform 3.4 V, the first charge-discharge specific capacity under 0.1C are 164.6 and 163.6 mAh/g respectively.