Search

Exploring better electrochemical energy storage devices is a great challenge. Lithium‐ion capacitors have attracted much attention because they combine the advantages of Li‐ion batteries and supercapacitors, but the mismatch between the kinetics and capacity of the cathode and anode is still an extraordinary gap. In order to address this issue, a cubic‐phase perovskite fluoride KMnF3 via a simple and safe coprecipitation way is synthesized. The KMnF3 electrode exhibits a cubic‐phase structure and a pseudocapacitive kinetics by X‐ray diffractometer and cyclic voltammetry. The high specific capacity (189 mAh g−1 at 0.1 A g−1 for 500 cycles) and fast pseudocapacitive control dynamics (at the sweep speed of 0.2 mV s−1, the pseudocapacitance ratio is 62.12%) can be demonstrated in half cell, while the b‐value is up to 0.95. Further assembled with activate carbon to form lithium‐ion capacitors (LICs), KMnF3//AC delivers high energy density (24 Wh kg−1), high power density (3900 kW kg−1), and long cycle life over 4000 cycles. The findings shed lights on developing advanced electrode materials for high‐performance electrochemical LICs. [ABSTRACT FROM AUTHOR]

The high-performance and low-cost NiCoP//WPBC-6 LIC exhibits a high ED of 127.4 ± 3.3 Wh kg−1 and large PD of 18240 W kg−1 as well as excellent cycle stability (capacity retention of 76.4% after 7000 cycles). [Display omitted] • The NiCoP microspheres architecture is synthesized through a hard template and in situ phosphorization process. • The NiCoP microspheres anode material demonstrates prominent specific capacity and rate performance as well as outstanding cycle stability. • The watermelon-peel biomass-derived carbons (WPBCs) were purposefully synthesized and investigated as cathode material to further improve the electrochemical performance of the LICs. • The high-performance NiCoP@Co 2 P//WPBC-6 LIC device presents a high ED of 127.4 Wh kg−1 and a large PD of 18240 W kg−1. Lithium-ion capacitors (LICs) are emerging as one of the most advanced energy storage devices by combining the virtues of both supercapacitors (SCs) and lithium-ion batteries (LIBs). However, the kinetic and capacity mismatch between anode and cathode is the main obstacle to wide applications of LICs. Therefore, the effective strategy of constructing a high-performance LIC is to improve the rate and cycle performance of the anode and the specific capacity of the cathode. Herein, the nickel cobalt phosphate (NiCoP) microspheres anode is demonstrated with robust structural integrity, high electrical conductivity, and fast kinetic feature. Simultaneously, the watermelon-peel biomass-derived carbon (WPBC) cathode is demonstrated a sustainable synthesis strategy with high specific capacity. As expected, the NiCoP exhibits high specific capacities (567 mAh g−1 at 0.1 A g−1), superior rate performance (300 mAh g−1 at 1A g−1), and excellent cycle stability (58 mAh g−1 at 5 A g−1 after 15,000 cycles). The WPBC possesses a high specific surface area (SSA) of 3303.6 m2 g−1 and a high specific capacity of 226 mAh g−1 at 0.1 A g−1. Encouragingly, the NiCoP//WPBC-6 LIC device can deliver high energy density (ED) of 127.4 ± 3.3 and 67 ± 3.8Wh kg−1 at power density (PD) of 190 and 18240 W kg−1 (76.4% capacity retention after 7000 cycles), respectively. [ABSTRACT FROM AUTHOR]

The Lithium‐ion capacitor (LIC) is a potential candidate for the next generation of energy storage devices due to high power density, high energy density and excellent cycle stability. Nonetheless, the problem of matching optimization is still faced for LIC. Many different approaches are explored to find a balance between the two storage mechanisms so that high performance LICs can be obtained. Here, CoF2, prepared by solvothermal method, showed reversible specific capacity of 307 mAh g−1 after 900 cycles at 0.1 A g−1 and 81 mAh g−1 after 10,000 cycles at 4 A g−1. Meanwhile, coconut shell is used as precursor for preparing natural porous carbon as cathode materials of LIC. The coconut shell biomass carbon (CSBC‐5), outstanding specific surface area (2767 m2 g−1), holds a capacity of 120 mAh g−1 after 1000 cycles at 1 A g−1. The LIC, CoF2 as anode and CSBC‐5 as cathode, shows excellent cycle stability (65 % capacity retention after 5000 cycles), higher energy density of 82 Wh kg−1 (at power density of 190 W kg−1) and higher power density of 3800 W kg−1(at energy density of 50 Wh kg−1). Therefore, the material of CoF2 is a promising choice for the future anode and promotes the development of LIC. [ABSTRACT FROM AUTHOR]

[Display omitted] • We prepared VO 2 (B) nanoflakes with petal-shaped folds as a new cathode material. • The VO 2 (B) had higher activity and quicker electron transfer kinetics. • The cathode material got high capacity and excellent rate performance. • The VO 2 (B) obtained for 101.4% high capacity retention at 10 A g−1 after 2000 cycles. Vanadium dioxide is widely used as a low-cost, high-safety cathode material for aqueous zinc ion batteries because of its tunnel structure that facilitates the intercalates/de-intercalates of Zn2+. However, it has been a challenge to improve the rate performance of vanadium dioxide and its cycling stability at high current densities. Here, we report VO 2 (B) nanoflakes with petal-shaped folds at the top. Combine with a higher pseudocapacitance contribution and part of diffusion control, the VO 2 (B) led to higher electrochemical activity, quicker electron transfer kinetics and better electronic conductivity. The VO 2 (B) discovers a considerable capacity of 301.7 mA h g−1 at 1 A g−1, an impressive rate performance of 248.4 mA h g−1 after 1000 cycles at 5 A g−1,and 89.0 mA h g−1 at the current density of 50 A g−1. More surprisingly, the VO 2 (B) can keep 201.3 mA h g−1 after 2000 cycles at 10 A g−1, and obtain 101.4% high capacity retention. This method effectively improves the rate performance and long-cycle stability of vanadium dioxide, and also provides ideas for improving the performance of other cathode materials for aqueous zinc ion batteries. [ABSTRACT FROM AUTHOR]

The poor long-term cycle stability of cathode materials for aqueous zinc-ion batteries has always been one of the limiting factors affecting their further applications. In this work, a solvothermal method was used to change the morphology and structure of the V 2 O 5 precursor to prepare a curled hydrated VO 2 (B) nanosheet. The VO 2 (B) has a specific capacity of 400.2 mAh g−1 at 0.5 A g−1, and after 6,000 cycles at 5 A g−1, the VO 2 (B) can still achieve a discharge specific capacity of 223.5 mAh g−1, with a capacity retention rate of 84.3%. Moreover, the energy density and power density of the VO 2 (B) are also very impressive (300.7 Wh kg−1 at 168.61 W kg−1; 233.9 Wh kg−1 at 7317 W kg−1). Such excellent performance is closely linked to the suitable nanostructure, the high capacitance-controlled kinetic behavior, the fast diffusion of Zn2+ and the crystal water sustained the structure of VO 2 (B). And the energy storage mechanism of the material is H+/Zn2+ co-insertion. [Display omitted] • We used a solvothermal method converted V 2 O 5 to VO 2 (B)·0.25 H 2 O. • The cathode material got impressive energy density and power density. • The hydrated VO 2 (B) obtained for 223.5 mAh g−1 at 5 A g−1 after 6000 cycles. • Crystal water played a pillar role in the electrode material. • The H+/Zn2+ were co-inserted/extracted in the cathode material. [ABSTRACT FROM AUTHOR]