Feng Yu

Aqueous Rechargeable Zinc/Aluminum Ion Battery with Good Cycling Performance.

Developing rechargeable batteries with low cost is critically needed for the application in large-scale stationary energy storage systems. Here, an aqueous rechargeable zinc//aluminum ion battery is reported on the basis of zinc as the negative electrode and ultrathin graphite nanosheets as the positive electrode in an aqueous Al2(SO4)3/Zn(CHCOO)2 electrolyte. The positive electrode material was prepared through a simple electrochemically expanded method in aqueous solution. The cost for the aqueous electrolyte together with the Zn negative electrode is low, and their raw materials are abundant. The average working voltage of this aqueous rechargeable battery is 1.0 V, which is higher than those of most rechargeable Al ion batteries in an ionic liquid electrolyte. It could also be rapidly charged within 2 min while maintaining a high capacity. Moreover, its cycling behavior is also very good, with capacity retention of nearly 94% after 200 cycles.

Pseudocapacitance contribution in boron-doped graphite sheets for anion storage enables high-performance sodium-ion capacitors

Research on metal-ion hybrid capacitors is emerging as one of the hottest topics in energy storage fields because of their combination of high power and energy densities. To improve the sluggish faradaic reaction in traditional electrode materials for metal-ion hybrid capacitors, intercalation pseudocapacitive materials have been developed as attractive candidates. However, all the previously reported pseudocapacitances in intercalation/deintercalation reactions are based on cations (Li+, Na+, Zn2+etc.). In this work, we demonstrated the high pseudocapacitance contribution in boron-doped graphite (BG) sheets by taking advantage of anion storage. The BG electrode can reversibly store anions (PF6−) through both a surface-controlled pseudocapacitive reaction and a diffusion-limited intercalation/deintercalation reaction. The fabricated Na-ion hybrid capacitor with a BG cathode exhibits superior electrochemical performance. Density functional theory (DFT) calculation reveals that B-doping can significantly reduce the PF6− diffusion energy barrier in the graphite layers.

Ultrathin NiCo2S4@graphene with a core–shell structure as a high performance positive electrode for hybrid supercapacitors

NiCo 2 S 4 is a promising material for supercapacitors owing to its merits of high conductivity and activity in redox reactions. However it suffers poor cycling stability due to structural degradation of the electrode through the redox process. Herein we demonstrate a facile method for the synthesis of a NiCo 2 S 4 /graphene composite where NiCo 2 S 4 is encapsulated with an ultrathin graphene layer to form a core/shell structure (NiCo 2 S 4 @G). Transmission electron microscopy (TEM) indicates that the shell is only 3–5 layers of graphene and the NiCo 2 S 4 particle core has a uniform size of around 5–7 nm. The NiCo 2 S 4 @G composite exhibits excellent electrochemical performance with a specific capacitance of 1432 F g −1 at a current density of 1 A g −1 . A hybrid supercapacitor assembled using the synthesized NiCo 2 S 4 @G as a positive electrode and porous carbon as a negative electrode demonstrates a high energy density of 43.4 W h kg −1 at a power density of 254.3 W kg −1 in the voltage range 0–1.35 V. After 5000 charge/discharge cycles, the device still retains 83.4% of its initial capacitance.

Aqueous Dual-Ion Battery Based on Hematite Anode with Exposed {104} Facets

The aqueous rechargeable lithium battery (ARLB) is one of the most promising devices for large-scale grid applications. Currently, a key issue for ARLBs is to develop promising anode materials with favorable electrochemical performances. Here, for the first time, we demonstrate an aqueous battery that utilizes the reversible redox reaction with hydroxide ions (OH- ) in the hematite (Fe2 O3 ) anode and a commercial Li ion intercalation compound in neutral solution as the cathode. The fabricated aqueous battery displays a reversible capacity of 92u2005mAhu2009g-1 . The morphology of the used Fe2 O3 anode with exposed {1u20090u20094} facets for this aqueous battery is unique and attractive. Importantly, with the dual-pH neutral-alkaline hybrid electrolyte, many excellent anode materials that previously could only work in alkaline electrolytes can now be successfully combined with commercial cathodes in neutral solutions, which may significantly enrich the range of anode materials for ARLBs. In addition, the reported battery configuration can be extended to other aqueous batteries beyond Li-ion ones with lower cost.