Bi-Interlayer Strategy for Modulating NiCoP-Based Heterostructure toward High-Performance Aqueous Energy Storage Devices.

Nickel-cobalt (NiCo) phosphides (NCPs) possess high electrochemical activity, which makes them promising candidates for electrode materials in aqueous energy storage devices, such as supercapacitors and zinc (Zn) batteries. However, the actual specific capacitance and rate capability of NCPs require further improvement, which can be achieved through reasonable heterostructural design and loading conditions of active materials on substrates. Herein, novel hierarchical Bi-NCP heterogeneous structures with built-in electric fields consisting of bismuth (Bi) interlayers (electrodeposited on carbon cloth (CC)) are designed and fabricated to ensure the formation of uniform high-load layered active materials for efficient charge and ion transport. The resulting CC/Bi-NCP electrodes show a uniform, continuous, and high mass loading (>3.5 mg) with a superior capacitance reaching 1200 F g-1 at 1 A g-1 and 4129 mF cm-2 at 1 mA cm-2 combined with high-rate capability and durable cyclic stability. Moreover, assembled hybrid supercapacitors (HSCs), supercapatteries, and alkaline Zn-ion (AZBs) batteries constructed using these electrodes deliver high energy densities of 64.4, 81.8, and 319.1 Wh kg-1, respectively. Overall, the constructed NCPs with excellent aqueous energy storage performance have the potential for the development of novel transition metal-based heterostructure electrodes for advanced energy devices.

Efficient fabrication of flower-like core-shell nanochip arrays of lanthanum manganate and nickel cobaltate for high-performance supercapacitors.

The low energy density issue raises serious concerns for the large-scale application of supercapacitors. However, the development and utilization of new electrode materials with a high specific capacity to improve the energy density of supercapacitors remain challenging. Herein, an LaMnO3@NiCo2O4/carbon cloth (LMO@NCO/CC) composed of a multilayer flower-like nanochip array is prepared for the first time using an efficient electrodeposition method. This novel structure exploits the high conductivity of LaMnO3/carbon cloth (LMO@CC) to provide an efficient electron transport path for the outer layer of the NiCo2O4/carbon cloth (NCO@CC) nanoarrays, broadening the potential window. Due to the unique nanostructure configuration and the strong synergistic effect of the developed LMO@NCO/CC, the prepared electrodes show excellent supercapacitor performance. At a current density of 1 A g-1, LMO@NCO/CC has a higher specific capacitance value of 942 F g-1. The application value is extended through the fabrication of asymmetric supercapacitors with a maximum energy density of 49 Wh kg-1 and excellent cycle stability (the initial capacitance value remains 106 % after 10,000 cycles of charging and discharging at a high current density of 10 A g-1). Our work paves the way for the development of next-generation electrode materials for high-performance supercapacitors.

Oxygen-vacancy abundant alpha bismuth oxide with enhanced cycle stability for high-energy hybrid supercapacitor electrodes.

Bi2O3 is an outstanding electrode material due to its high theoretical specific capacity. Hence, the synthesis of δ-Bi2O3 materials with high oxygen-vacancy contents could improve their electrochemical performances but causes easy conversion to α-Bi2O3 with low oxygen-vacancy contents, leading to poor cycling stability and limited practical applications. To overcome these problems, an effective strategy for constructing high oxygen vacancies α-Bi2O3 on activated carbon fiber paper (ACFP) is developed in this study. To this end, ACFP/Bi(OH)3 is first synthesized by the solvothermal method and then converted to ACFP/α-Bi2O3 by in situ electrochemical activation. The proposed innovative electrochemical method quickly and easily introduces oxygen vacancies while preserving the three-dimensional structure, thereby promoting the charge transfer and ions diffusion in ACFP/α-Bi2O3. Consequently, the specific capacity of ACFP/α-Bi2O3 reaches 906C g-1 at 1 A g-1, and the capacity retention remains above 70% after 3000 cycles, a value higher than that of δ-Bi2O3 (45%). Furthermore, the hybrid supercapacitor device assembled by ACFP/α-Bi2O3 delivers a maximum energy density of 114.9 Wh kg-1 at 900 W kg-1 and outstanding cycle stability with 73.56 % retention after 5500 cycles. In sum, the proposed ACFP/α-Bi2O3 with high performance and good stability looks promising for use as bismuth-based anode materials in supercapacitors and aqueous batteries.

Coaxial cable-like dual conductive channel strategy in polypyrrole coated perovskite lanthanum manganite for high-performance asymmetric supercapacitors.

Perovskite transition metal oxides are promising materials for supercapacitor electrodes due to their high theoretical capacities. However, these materials still suffer from poor conductivity, low specific capacitance, and moderate cycle stability, restraining their practical applications. In this study, LaMnO3@CC-PPy materials were prepared by two-step electrodeposition based on the inspiring design of coaxial cables. To this end, electrochemically active LaMnO3 was first grown on carbon cloth (CC) with good flexibility and conductivity and then followed by further coating with polypyrrole (PPy) layer. The best PPy load was identified by adjusting the deposition time. The resulting LaMnO3@CC-PPy electrodes showed excellent specific capacitance reaching 862F g-1 at 1 A g-1 with retention rate of 75% at high current density of 10 A g-1, indicative of excellent rate performance. The cycle stability of the electrodes also improved after 3000 cycles at 10 A g-1 with a retention rate reaching 66%. To assemble asymmetric supercapacitor (ASC) devices, NiCo2O4@CC cathodes were prepared by electrodeposition. Ultra-high energy density of about 73 Wh kg-1 and good cycle stability were recorded with the devices. The high performance of the as-obtained materials was attributed to the existence of internal and external double electric channels, as well as the abundant internal space. These features ensured good conductivity, rapid charge transfer, and fast ion diffusion, thereby significantly improving the overall material cycle stability. In sum, these findings look promising for future preparation of high-performance perovskite supercapacitors.

Two-step fabrication of lanthanum nickelate and nickel oxide core-shell dandelion-like materials for high-performance supercapacitors.

LaNiO3 and NiO are promising materials for supercapacitor applications. However, it is still challenging to design special structures based on these materials to improve the electrochemical performances of supercapacitor electrodes. In this work, a two-step method with low cost and convenient operation was developed to prepare dandelion-shaped LaNiO3/NiO (CSD-LaNiO3/NiO) with core-shell structure. The as-obtained CSD-LaNiO3/NiO showed high conductivity due to the core LaNiO3, which helped to provide an efficient electron transmission path for the shell NiO, producing a strong synergistic effect. The results of electrochemical properties of CSD-LaNiO3/NiO, LaNiO3 and NiO samples revealed the superior specific capacitance of CSD-LaNiO3/NiO (326.8 F g-1) at 1 A g-1 compared to LaNiO3 (166.5 F g-1) and NiO (44.2 F g-1). The as-obtained CSD-LaNiO3/NiO material was then mixed with activated carbon and assembled into an asymmetric supercapacitor, which exhibited a wide potential window of 1.8 V, energy density of 30.4 Wh kg-1 at 1800 W kg-1, and specific capacity retention of 97.7% after 3000 cycles. In sum, the as-obtained core-shell nanostructure prepared by the proposed synthesis method is very promising for future development of high-performance supercapacitors.