transportation sector with electric vehicles. [1] The potential of renewable energy to power electric vehicles can contribute to a future world with cleaner skies, cheaper energy, and healthier air. Energy distribution can also be simplified by sending electrons over the grid, or even by locally generating energy using solar panels, instead of shipping chemical fuels through pipelines or via road transport. One of the core technologies required to realize the viability of renewable energy sources is to develop improved electrochemical energy storage systems. [2] Electric doublelayer capacitors (EDLCs) are more appropriate for high-power applications, while secondary batteries are well suited for high-energy applications. EDLCs are thus sometimes used in tandem with batteries so that the former provide power and the latter provide energy for the integrated system. Current research in the field of energy storage is converging to target single devices that have EDLClevel power density as well as cycling stability and battery-level energy density. [3] Supercapacitors are an important technology for the future of energy storage. Supercapacitors are especially designed for applications that require a high rate capability, where a sudden burst of energy in a very short time interval is needed. However, supercapacitors have a rather limited energy density. Thus, different charge storage mechanisms, in addition to and/or in place of EDLCs, have been developed to boost the energy content of supercapacitors. [4] The most intriguing approach is the incorporation of nanostructured solid-state electrode materials, mainly transition metal oxides/sulfides, [5] layered double hydroxides, [2b] or conductive polymers, [6] that utilize fast Faradaic redox reactions for energy storage. Another intriguing approach is the development of hybrid ion capacitors, which are intermediate in energy between batteries and supercapacitors, while demonstrating supercapacitor-like power performance and cycling stability. [7] Inspired by the solid-state pseudocapacitive charge storage mechanism, the concept of liquid-state redox electrolytes has also been developed to supply extra energy. [8] Via this fascinating approach, the dead weight of the formerly inert electrolytes is utilized as an active component to augment the energy storage performance, and the wasted Discovering efficient pseudocapacitive charge storage materials has become one of the grand challenges to reduce the gap between high energy density batteries and high power density and durable electrical double-layer capacitors.This research direction is facilitated by the introduction of redox-active species that add Faradaic charge storage to the system. However, the astonishing abilities of organic redox species to increase energy density are insufficient to compensate for their poor electrical conductivity and inferior cyclability. Herein, it is proposed that these challenges can be simultaneously met by thoughtful selection of a redox species, thionine, that can be conjugate...

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The pursuit of new negative electrode materials for redox supercapacitors with a high capacitance, boosted energy, and high rate capability is still a tremendous challenge. Herein, we report a Nile Blue conjugated graphene aerogel (NB–GA) as a negative electrode material with excellent pseudocapacitive performance (with specific capacitance of up to 483 F g–1 at 1 A g–1) in all acidic, neutral, and alkaline aqueous electrolytes. The contribution from capacitive charge storage represents 93.4% of the total charge, surpassing the best pseudocapacitors known. To assess the feasibility of NB–GA as a negative electrode material across the full pH range, we fabricated three devices, namely, a symmetric NB–GA||NB–GA device in an acidic (1.0 M H2SO4) electrolyte, an NB–GA||MnO2 device in a pH-neutral (1.0 M Na2SO4) electrolyte, and an NB–GA||LDH (LDH = Ni–Co–Fe layered double hydroxide) device in an alkaline (1.0 M KOH) electrolyte. The NB–GA||NB–GA device exhibits a maximum specific energy of 22.1 Wh kg–1 and a specific power of up to 8.1 kW kg–1; the NB–GA||MnO2 device displays a maximum specific energy of 55.5 Wh kg–1 and a specific power of up to 14.9 kW kg–1, and the NB–GA||LDH device shows a maximum specific energy of 108.5 Wh kg–1 and a specific power of up to 25.1 kW kg–1. All the devices maintain excellent stability over 5000 charge–discharge cycles. The outstanding pseudocapacitive performances of the NB–GA nanocomposites render them a highly promising negative electrode material across the entire pH range.

The surging interest in high performance, low‐cost, and safe energy storage devices has spurred tremendous research efforts in the development of advanced electrode active materials. Herein, the in situ growth of zinc–iron layered double hydroxide (Zn–Fe LDH) on graphene aerogel (GA) substrates through a facile, one‐pot hydrothermal method is reported. The strong interaction and efficient electronic coupling between LDH and graphene substantially improve interfacial charge transport properties of the resulting nanocomposite and provide more available redox active sites for faradaic reactions. An LDH–GA||Ni(OH)2 device is also fabricated that results in greatly enhanced specific capacity (187 mAh g−1 at 0.1 A g−1), outstanding specific energy (147 Wh kg−1), excellent specific power (16.7 kW kg−1), along with 88% capacity retention after >10 000 cycles. This approach is further extended to Ni–MH and Ni–Cd batteries to demonstrate the feasibility of compositing with graphene for boosting the energy storage performance of other well‐known Ni‐based batteries. In contrast to conventional Ni‐based batteries, the nearly flat voltage plateau followed by a sloping potential profile of the integrated supercapacitor–battery enables it to be discharged down to 0 V without being damaged. These findings provide new prospects for the design of high‐performance and affordable superbatteries based on earth‐abundant elements.

Layered double hydroxides (LDHs) stand out as versatile structural platforms for modulating the electronic structure of highly reactive earth‐abundant transition metal‐based electrocatalysts for the hydrogen evolution reaction (HER), the oxygen evolution reaction (OER), and the oxygen reduction reaction (ORR). Herein, a Ni‐Co‐Fe LDH, electrodeposited on a Ni nanocones (NiNCs)‐decorated Ni foam, acts as a morphology driving template to direct the facile constant potential electrosynthesis of NiCoFeB from a K2B4O7 solution. The amorphous tri‐metal borate (TMB) displays excellent trifunctional electrocatalytic activities toward the HER (overpotential at 10 mA cm−2, η10 = 174 mV vs RHE), OER (η10 = 208 mV), as well as ORR (half‐wave potential = 0.723 V) with a low ΔEOER−ORR of 770 mV, and excellent durability of over 110 h in alkaline solutions. A zinc–air battery based on the TMB@NiNC dual oxygen catalyst cathode exhibits a high open‐circuit voltage of 1.477 V, a power density of 107 mW cm−2, a specific energy of 918 W h kgZn−1 and an outstanding cycling stability of over 1330 cycles at 10 mA cm−2, which outperforms the commercial noble metal benchmarks. These results demonstrate that LDHs are efficient sacrificial templates for the preparation of high‐performance multifunctional multi‐metal borate electrocatalysts for energy‐related applications.