Coupling NiCoP bimetallic phosphide nanoparticles with alkali-induced 3D crinkled Ti3C2 effectively enhances the structural stability and improved reaction kinetics of anodes for SIBs.

Developing single-site catalysts featuring maximum atom utilization efficiency is urgently desired to improve oxidation-reduction efficiency and cycling capability of lithium-oxygen batteries. Here, we report a green method to synthesize isolated cobalt atoms embedded ultrathin nitrogen-rich carbon as a dual-catalyst for lithium-oxygen batteries. The achieved electrode with maximized exposed atomic active sites is beneficial for tailoring formation/decomposition mechanisms of uniformly distributed nano-sized lithium peroxide during oxygen reduction/evolution reactions due to abundant cobalt-nitrogen coordinate catalytic sites, thus demonstrating greatly enhanced redox kinetics and efficiently ameliorated over-potentials. Critically, theoretical simulations disclose that rich cobalt-nitrogen moieties as the driving force centers can drastically enhance the intrinsic affinity of intermediate species and thus fundamentally tune the evolution mechanism of the size and distribution of final lithium peroxide. In the lithium-oxygen battery, the electrode affords remarkably decreased charge/discharge polarization (0.40 V) and long-term cyclability (260 cycles at 400 mA g−1).

The novel PDDA-NPCNs/Ti3C2 hybrids via an electrostatic attraction self-assembly approach effectively accelerate reaction kinetics and improve electrochemical performance as PIBs anodes.

Until now, supercapacitors have been optimized in many ways to solve the abovementioned two main issues, such as the modification of existing materials, [5,6] the discovery of new materials, [7][8][9] the exploration of electrolytes, [10][11][12] the assembly of full supercapacitors, [13] the optimization of the voltage window etc. [14,15] Specifically, from the perspective of material development, RuO 2 is regarded as an ideal supercapacitor electrode material due to its high specific capacitance, but its high cost limits its practical application. [16,17] Thus, other nonnoble pseudocapacitive materials (for example, MnO 2 , [18] Fe 2 O 3 , [19] MoO 3 , [20] Nb 2 O 5 , [21] and VN [22] ) have attracted much attention. However, the poor electronic conductivity of most pseudocapacitor materials lead to their higher electrode resistances and lower power densities compared with those of EDLCs (Electrical Double Layer Capacitors) and electrolytic capacitors. [23] Very recently, 2D materials with high capacitances, such as MXenes, have been reported, but their main drawbacks are their complex synthetic processes and the use of highly toxic hydrofluoric acid (HF). [7,9] With regard to electrolytes, most researchers prefer aqueous electrolytes for their higher ionic concentration, lower resistance, lower cost, and better environmental-friendliness compared to those of organic electrolytes. [13,24,25] However, the limited potential window of aqueous supercapacitors, owing to the theoretical water splitting potential window of 1.23 V, is a challenge. To widen the potential window, supercapacitor electrodes must always be assembled into supercapacitor systems or so-called full supercapacitors, including symmetric supercapacitors, asymmetric supercapacitors, and hybrid supercapacitors. [4,5,13] To further enhance the voltage window of a single electrode or full supercapacitor, some methods have been adopted, including surface charge optimization, [14] electrode material modification, [15,26] electrolyte exploration, [5,10,24,27] and unique full supercapacitor system assemblies. [4,5,13] Although the above strategies have resulted in great progress for supercapacitors over the past few decades, the application of supercapacitors is still limited. Acquiring excellent performance while using simple methods is still a challenge. Thus, new strategies for the further development of supercapacitors are urgently needed. Herein, we propose a new view of the supercapacitor called the "integrated supercapacitor." As shown in the "supercapacitor tree" (Figure 1a), the integrated supercapacitor is a powerful strategy for integrating the traditional concepts of positive electrodes, negative electrodes, symmetric Charging times ranging from seconds to minutes with high power densities can be achieved by electrochemical capacitors in principle. Over the past few decades, the performance of supercapacitors has been greatly improved by the utilization of new materials, preparation of unique nanostructures, investigation of electrolytes, and ...

Unique layered Ti3C2/Ni–Co–Al layered double hydroxide (LDH) heterostructures alternatively stacked with molecular-level nanosheets are for the first time synthesized by a facile liquid-phase cofeeding and electrostatic attraction heteroassemble strategy between negatively charged Ti3C2 and positively charged Ni–Co–Al-LDH nanosheets. The molecular-level Ti3C2/Ni–Co–Al-LDH heterostructures possessing the merits of both conductive and pseudocapacitive components can show greatly enhanced dynamic behavior in Faradaic reaction, which is significant for obtaining a high power density. Electrons penetrate in Ti3C2 layers, while ions diffuse rapidly along two-dimensional galleries, displaying the shortest diffusion pathway and highest efficiency for charge transfer. The Ti3C2/Ni–Co–Al-LDH heterostructure exhibits a specific capacitance of 748.2 F g–1 at current density of 1 A g–1, showing an enhanced rate capacity. Importantly, a maximum energy density of 45.8 Wh kg–1 is obtained when Ti3C2/Ni–Co–Al-LDH acts as the positive electrode for an all-solid-state flexible asymmetric supercapacitor. The results indicate that molecular-level heterotructure is a promising candidate for future high-energy supercapacitors.