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High‐voltage lithium metal batteries are the most promising energy storage technology due to their excellent energy density (>400 Wh kg−1). However, the oxidation decomposition of conventional carbonate‐based electrolytes at the high‐potential cathode, the detrimental reaction between the lithium anode and electrolyte, particularly the uncontrolled lithium dendrite growth, always lead to a severe capacity decay and/or flammable safety issues, hindering their practical applications. Herein, a solvation structure engineering strategy based on tuning intermolecular interactions is proposed as a strategy to design a novel nonflammable fluorinated electrolyte. Using this approach, this work shows superior cycling stability in a wide temperature range (−40 °C to 60 °C) for a 4.4 V‐class LiNi0.8Co0.1Mn0.1O2 (NCM811)‐based Li‐metal battery. By coupling the high‐loading of NCM811 cathode (3.0 mAh cm−2) and a controlled amount of lithium anode (twofold excess of Li deposition on Cu, Cu@Li) (N/P = 2), the Cu@Li || NCM811 full cell can cycle more than 162 cycles with high‐capacity retention of 80%. This work finds that the change of the coordination environment of Li+ with solvent and PF6− by tuning intermolecular interaction is an effective method to stabilize the electrolyte and electrode performance. These discoveries can provide a pathway for electrolyte design in metal ion batteries. [ABSTRACT FROM AUTHOR]

Carbonaceous materials are promising anodes for practical potassium‐ion batteries, but fail to meet the requirements for durability and high capacities at low potentials. Herein, we constructed a durable carbon anode for high‐energy‐density K‐ion full cells by a preferential pyrolysis strategy. Utilizing S and N volatilization from a π–π stacked supermolecule, the preferential pyrolysis process introduces low‐potential active sites of sp2 hybridized carbon and carbon vacancies, endowing a low‐potential "vacancy‐adsorption/intercalation" mechanism. The as‐prepared carbon anode exhibits a high capacity of 384.2 mAh g−1 (90 % capacity locates below 1 V vs. K/K+), which contributes to a high energy density of 163 Wh kg−1 of K‐ion full battery. Moreover, abundant vacancies of carbon alleviate volume variation, boosting the cycling stability over 14 000 cycles (8400 h). Our work provides a new synthesis approach for durable carbon anodes of K‐ion full cells with high energy densities. [ABSTRACT FROM AUTHOR]

Highlights: The N/S co-doped lignin-derived porous carbon (NSLPCs) with ultra-high heteroatom doping was prepared through a novel supramolecule-mediated pyrolysis strategy. Covalently bonded graphitic carbon/amorphous carbon intermediates induce the formation of high heteroatom doping. The high heteroatom doping of NSLPC could provide abundant defective active sites for the adsorption of K+. Amorphous carbons are promising anodes for high-rate potassium-ion batteries. Most low-temperature annealed amorphous carbons display unsatisfactory capacities. Heteroatom-induced defect engineering of amorphous carbons could enhance their reversible capacities. Nevertheless, most lignocellulose biomasses lack heteroatoms, making it a challenge to design highly heteroatom-doped carbons (> 10 at%). Herein, we report a new preparation strategy for amorphous carbon anodes. Nitrogen/sulfur co-doped lignin-derived porous carbons (NSLPC) with ultra-high nitrogen doping levels (21.6 at% of N and 0.8 at% of S) from renewable lignin biomacromolecule precursors were prepared through a supramolecule-mediated pyrolysis strategy. This supermolecule/lignin composite decomposes forming a covalently bonded graphitic carbon/amorphous carbon intermediate product, which induces the formation of high heteroatom doping in the obtained NSLPC. This unique pyrolysis chemistry and high heteroatom doping of NSLPC enable abundant defective active sites for the adsorption of K+ and improved kinetics. The NSLPC anode delivered a high reversible capacity of 419 mAh g‒1 and superior cycling stability (capacity retention of 96.6% at 1 A g‒1 for 1000 cycles). Potassium-ion hybrid capacitors assembled by NSLPC anode exhibited excellent cycling stability (91% capacity retention for 2000 cycles) and a high energy density of 71 Wh kg–1 at a power density of 92 W kg–1. [ABSTRACT FROM AUTHOR]

The popular metal‐ion batteries (MIBs) suffer from environmental and economic issues because of their heavy dependency on nonrenewable metals. Here, we propose a metal‐free ammonium (NH4+)‐based dual‐ion battery with a record‐breaking operation voltage of 2.75 V. The working mechanism of this sustainable battery involves the reversible anion (PF6−) intercalation chemistry in graphite cathode and NH4+ intercalation behavior in PTCDI (3,4,9,10‐perylenetetracarboxylic diimide) anode. This new battery configuration successfully circumvented the reduction susceptibility of NH4+ and the lack of mature NH4+‐rich cathodes for NH4+ ion batteries (AIBs). The customized organic NH4+ electrolyte endows the graphite||PTCDI full battery with durable longevity (over 1000 cycles) and a high energy density (200 Wh kg−1). We show that the development of AIBs should be high‐voltage‐oriented while circumventing low operation potential to avoid NH4+ reduction. [ABSTRACT FROM AUTHOR]

An electrochemical zinc ion capacitor (ZIC) is a hybrid supercapacitor composed of a porous carbon cathode and a zinc anode. Based on the low‐cost features of carbon and zinc metal, ZIC is a potential candidate for safe, high‐power, and low‐cost energy storage applications. ZICs have gained tremendous attention in recent years. However, the low energy densities and limited cycling stability are still major challenges for developing high‐performance ZICs. First, the energy density of ZIC is limited by the low capacitance of porous carbon cathodes. Second, aqueous electrolytes induce parasitic reactions, which results in limited voltage windows and poor cycling performances of ZICs. Third, the poor stabilities and low utilization of zinc anodes remain major challenges to develop practical ZICs. This review summarizes the recent progress in developing ZICs and highlights both the promising and challenging attributes of this emerging energy storage technology. Future research directions are proposed for developing better, lower cost, and more scalable ZICs for energy storage applications. [ABSTRACT FROM AUTHOR]

Cost, safety, and cycle life have emerged as prime concerns to build robust batteries to cater to the global energy demand. These concerns are impacted by all battery components, but the realizable energy density of lithium‐ion batteries (LIBs) is limited by the performance of cathodes. Thus, cathode materials have a significant role to play in advancing the performance and economics of secondary batteries. To realize next generation Li‐ion and post Li‐ion batteries, a variety of cathode insertion materials have been explored, but finding a cost effective and stable cathode material that can deliver high energy density has been a daunting task. Oxide cathode materials are ubiquitous in commercial applications, as they can deliver high capacity. In comparison, polyanionic insertion materials can offer tuneable (high) redox potential, operational safety, and structural as well as thermal stability. Indeed, a wide range of polyanionic materials like phosphates, borates, sulfates, and their complexes have been reported. In this article, the alkali metal fluorophosphates class of polyanionic cathodes for secondary batteries is discussed. The various reported fluorophosphate insertion materials are discussed in terms of their electrochemical and electrocatalytic properties. The historical overview, recent progress, and remaining challenges for polyanionic fluorophosphates are presented along with suggested future research directions and potential application. [ABSTRACT FROM AUTHOR]

New covalent organic frameworks (COFs), encompassing redox‐functionalized moieties and an aza‐fused π‐conjugated system, are designed, synthesized, and deployed as negative electrodes in asymmetric supercapacitors (ASC), for the first time. The Hex‐Aza‐COFs are synthesized based on the solvothermal condensation reaction of cyclohexanehexone and redox‐functionalized aromatic tetramines with benzoquinone (Hex‐Aza‐COF‐2) or phenazine (Hex‐Aza‐COF‐3). The redox‐functionalized Hex‐Aza‐COFs show a specific capacitance of 585 F g−1 for Hex‐Aza‐COF‐2 and 663 F g−1 for Hex‐Aza‐COF‐3 in a three‐electrode configuration. These values are the highest among reported COF materials and are comparable with state‐of‐the‐art pseudocapacitive electrodes. The Hex‐Aza‐COFs exhibit a wide voltage window (0 to −1.0 V), which allow the construction of a two‐electrode ASC device by combining them with RuO2. The complementary potential windows of Hex‐Aza‐COF‐3 and RuO2 enable an asymmetric device with a high voltage window of 1.7 V. The RuO2//Hex‐Aza‐COF‐3 ASC device achieves an energy density value of 23.3 W h kg−1 at a power density of 661.2 W kg−1. The newly developed negative COF materials open new prospects for the development of high‐performance ASCs. [ABSTRACT FROM AUTHOR]

Aqueous electrochemical zinc ion capacitors (ZICs) are promising next‐generation energy storage devices because of their high safety, inexpensive raw materials, and long cycle life. Herein, an aqueous ZIC with superior performance is fabricated by employing an oxygen‐rich porous carbon cathode. Excellent capacitance and energy density are obtained thanks to the electric double‐layer capacitance of porous carbon, and additional pseudocapacitances originating from the variation in oxidation states of oxygen functional groups and the reversible electrochemical hydrogen adsorption and desorption during each round‐trip charge–discharge cycle. Moreover, the cycling stability of ZIC is effectively prolonged by suppressing zinc dendrite growth with a simple surface carbon coating strategy. The assembled ZIC delivers a high capacitance of 340.7 F g−1, a high capacity of 179.8 mAh g−1 in a wide voltage window of 0–1.9 V, a maximum energy density of 104.8 Wh kg−1, and an ultrahigh power density of 48.8 kW kg−1. Furthermore, the as‐fabricated aqueous ZIC exhibits an ultralong cycle life of 30 000 cycles with a high capacity retention of 99.2%. This work provides a novel design strategy by incorporating reversible hydrogen and oxygen redox reactions to enhance the energy storage capability of aqueous ZICs toward practical energy storage applications. [ABSTRACT FROM AUTHOR]

Hybrid mobile ion capacitors (HMIC) are proposed as a way to incorporate the advantages of both batteries and supercapacitors into one system. Unfortunately, considering the much slower Li+ intercalation/deintercalation process, finding a suitable battery anode material with a high rate performance is still a major challenge. Herein, the fabrication of nitrogen‐doped laser‐scribed graphene (NLSG) with a 3D structure as a binder‐free and conductive additive‐free anode is reported. This NLSG anode has high nitrogen and oxygen doping (8.6 and 6.3 at%), leading to the formation of conductive electrodes with an expanded lattice spacing, providing more convenient pathways and reaction sites for Li+ ions. Hybrid Li‐ion capacitors (HLICs) are assembled by combining the NLSG anodes with hierarchical porous carbon (PC) cathodes. The NLSG//PC HLICs show an energy density (including the total weight of two electrodes) of 186 Wh kg−1 at 200 W kg−1. Even when power density increases to the level of conventional supercapacitors (20 kW kg−1), an energy density of 76 Wh kg−1 is still be obtained. Further, the devices exhibit excellent cycle life, retaining 87.5% of the initial value after 5000 cycles. Herein, laser‐scribed graphene is demonstrated as a very promising electrode for mobile ion capacitors. [ABSTRACT FROM AUTHOR]

Abstract: Cost‐effective aqueous rechargeable batteries are attractive alternatives to non‐aqueous cells for stationary grid energy storage. Among different aqueous cells, zinc‐ion batteries (ZIBs), based on Zn2+ intercalation chemistry, stand out as they can employ high‐capacity Zn metal as the anode material. Herein, we report a layered calcium vanadium oxide bronze as the cathode material for aqueous Zn batteries. For the storage of the Zn2+ ions in the aqueous electrolyte, we demonstrate that the calcium‐based bronze structure can deliver a high capacity of 340 mA h g−1 at 0.2 C, good rate capability, and very long cycling life (96 % retention after 3000 cycles at 80 C). Further, we investigate the Zn2+ storage mechanism, and the corresponding electrochemical kinetics in this bronze cathode. Finally, we show that our Zn cell delivers an energy density of 267 W h kg−1 at a power density of 53.4 W kg−1. [ABSTRACT FROM AUTHOR]

A simple and scalable direct laser machining process to fabricate MXene-on-paper coplanar microsupercapacitors is reported. Commercially available printing paper is employed as a platform in order to coat either hydrofluoric acid-etched or clay-like 2D Ti3C2 MXene sheets, followed by laser machining to fabricate thick-film MXene coplanar electrodes over a large area. The size, morphology, and conductivity of the 2D MXene sheets are found to strongly affect the electrochemical performance due to the efficiency of the ion-electron kinetics within the layered MXene sheets. The areal performance metrics of Ti3C2 MXene-on-paper microsupercapacitors show very competitive power-energy densities, comparable to the reported state-of-the-art paper-based microsupercapacitors. Various device architectures are fabricated using the MXene-on-paper electrodes and successfully demonstrated as a micropower source for light emitting diodes. The MXene-on-paper electrodes show promise for flexible on-paper energy storage devices. [ABSTRACT FROM AUTHOR]

On-chip energy storage using microsupercapacitors can serve the dual role of supplementing batteries for pulse power delivery, and replacement of bulky electrolytic capacitors in ac-line filtering applications. Despite complexity and processing costs, microfabrication techniques are being employed in fabricating a great variety of microsupercapacitor devices. Here, a simple, cost-effective, and versatile strategy is proposed to fabricate flexible and curvilinear microsupercapacitors (MSCs). The protocol involves writing sacrificial ink patterns using commercial marker pens on rigid, flexible, and curvilinear substrates. It is shown that this process can be used in both lift-off and etching modes, and the possibility of multistack design of active materials using simple pen lithography is demonstrated. As a prototype, this method is used to produce conducting polymer MSCs involving both poly(3,4-ethylenedioxythiophene), polyaniline, and metal oxide (MnO2) electrode materials. Typical values of energy density in the range of 5-11 mWh cm−3 at power densities of 1-6 W cm−3 are achieved, which is comparable to thin film batteries and superior to the carbon and metal oxide based microsupercapacitors reported in the literature. The simplicity and broad scope of this innovative strategy can open up new avenues for easy and scalable fabrication of a wide variety of on-chip energy storage devices. [ABSTRACT FROM AUTHOR]

Microsupercapacitors (MSCs) with high energy densities offer viable miniaturized alternatives to bulky electrolytic capacitors if the former can respond at the kilo Hertz (kHz) or higher frequencies. Moreover, MSCs fabricated on a chip can be integrated into thin‐film electronics in a compatible manner, serving the function of ripple filtering units or harvesters of energy from high‐frequency sources. In this work, wafer‐scale fabrication is demonstrated of MXene microsupercapacitors with controlled flake sizes and engineered device designs to achieve excellent frequency filtering performance. Specifically, the devices (100 nm thick electrodes and 10 µm interspace) deliver high volumetric capacitance (30 F cm−3 at 120 Hz), high rate capability (300 V s−1), and a very short relaxation time constant (τ0 = 0.45 ms), surpassing conventional electrolytic capacitors (τ0 = 0.8 ms). As a result, the devices are capable of filtering 120 Hz ripples produced by AC line power at a frequency of 60 Hz. This study opens new avenues for exploring miniaturized MXene MSCs as replacements for bulky electrolytic capacitors. [ABSTRACT FROM AUTHOR]

Conductive 2D metal–organic frameworks (MOFs) have merits beyond traditional MOFs for electrochemical applications, but reports on using MOFs as electrodes for electrochemical microsupercapacitors (MSCs) are practically non‐existent. In this work, a Ni‐catecholate‐based MOF (Ni‐CAT MOF) having good conductivity and exhibiting redox chemistry in the positive and negative voltage windows is developed. A novel process is developed to selectively grow the conductive Ni‐CAT MOF on 3D laser scribed graphene (LSG). The LSG with its superior wettability serves as a functional matrix‐current collector for the hybridization of conductive Ni‐CAT MOF nanocrystals. Impressively, MSCs fabricated using the hybrid LSG/Ni‐CAT MOF show significant improvement compared with MOF‐free LSG electrodes. Specifically, the LSG/Ni‐CAT MOF electrodes can deliver MSCs with a wide operating voltage (1.4 V), high areal capacitance (15.2 mF cm−2), energy density (4.1 µWh cm−2), power density (7 mW cm−2), good rate performance, and decent cycling stability. This work opens up an avenue for developing electrochemical microsupercapacitors using conductive MOF electrodes. [ABSTRACT FROM AUTHOR]

The development of wearable electronics and sensing networks has increased the demand for wearable power modules that have steady output, high energy density, and long cycle life. Current power modules, such as batteries, suffer from low energy density due to their limited storage capacity. One solution to avoid the issue is to build a hybrid device consisting of both energy harvesting elements that continuously harvest ambient mechanical energy, and electrochemical energy storage units to store the harvested energy. Here, a hybrid energy harvesting bracelet, which combines a dual electromagnetic and triboelectric nanogenerator to harvest wrist motions, is reported. The bracelet is able to charge the RuO2‐based microsupercapacitor to 2 V with a single shake of human wrist, which allows the supercapacitor to power most electronic devices for minutes, such as a calculator, relative humidity, and temperature sensors. [ABSTRACT FROM AUTHOR]