Manganese dioxide (MnO₂), based on a two-electron-transfer deposition/dissolution chemistry, features an ultrahigh theoretical capacity (616 mAh g⁻¹), a favorable redox potential (1.23 V vs. the standard hydrogen electrode), inherent non-toxicity and low cost, rendering it a promising cathode candidate for high-energy aqueous batteries. However, its practical application is hampered by limited electrochemical reversibility and cycling stability, primarily attributed to the formation and accumulation of electrochemically inactive manganese (Mn) species, often termed “dead Mn”. This review provides an in-depth analysis of the “dead Mn” dilemma inherent in Mn²⁺/MnO₂ chemistry. First, the fundamental causes of “dead Mn” — insufficient electron supply and imbalanced (insufficient or excessive) proton supply — are systematically analyzed, as it detracts active material utilization, cycle life, and energy density. Mitigation strategies are then examined from three aspects: (i) preventing “dead Mn” formation due to insufficient electron supply, (ii) mitigating “dead Mn” formation related to imbalanced proton supply, and (iii) activating and regenerating existing “dead Mn”. Finally, we envision future research directions to enhance practical viability of Mn²⁺/MnO₂ deposition/dissolution chemistry, aiming to catalyze advancements in high-energy aqueous battery systems.

The escalating demand for micro/nano-sized devices, such as micro/nano-robots, intelligent portable/wearable microsystems, and implantable medical microdevices, necessitates the expeditious development of integrated microsystems incorporating energy conversion, storage, and consumption. Critical bottlenecks in microscale energy storage/sensors and their integrated systems are being addressed by exploring new technologies and new materials, e.g., MXene, holding great potential for developing lightweight and deformable integrated microdevices. This review summarizes the latest progress and milestones in the realization of MXene-based micro-supercapacitors (MSCs) and sensor arrays, and thus discusses the design fundamentals and key advancements of MXene-based energy conversion-storage-consumption integrated microsystems. Finally, we outline the key challenges in fabricating MXene-based MSCs/sensors and their self-powered integrated microsystems, which is crucial for their practical applications. Particularly, we illuminate viable solutions to such unsolved issues and highlight the exciting opportunities.

The Li-ion capacitors (LICs) develop rapidly due to their double-high features of high-energy density and high-power density. However, the relative low capacity of cathode and sluggish kinetics of anode seriously impede the development of LICs. Herein, the precisely pore-engineered and heteroatom-tailored defective hierarchical porous carbons (DHPCs) as large-capacity cathode and high-rate anode to construct high-performance dual-carbon LICs have been developed. The DHPCs are prepared based on triple-activation mechanisms by direct pyrolysis of sustainable lignin with urea to generate the interconnected hierarchical porous structure and plentiful heteroatom-induced defects. Benefiting from these advanced merits, DHPCs show the well-matched high capacity and fast kinetics of both cathode and anode, exhibiting large capacities, superior rate capability and long-term lifespan. Both experimental and computational results demonstrate the strong synergistic effect of pore and dopants for Li storage. Consequently, the assembled dual-carbon LIC exhibits high voltage of 4.5 V, high-energy density of 208 Wh kg⁻¹, ultrahigh power density of 53.4 kW kg⁻¹ and almost zero-decrement cycling lifetime. Impressively, the full device with high mass loading of 9.4 mg cm⁻² on cathode still outputs high-energy density of 187 Wh kg⁻¹, demonstrative of their potential as electrode materials for high-performance electrochemical devices.

Ultracompact and customizable micro-supercapacitors (MSCs) are highly demanded for powering microscale electronics of 5G and Internet of Things technologies. So far, tremendous efforts have been concentrated on fabricating high-performance MSCs; however, compatible fabrication and monolithic integration of MSCs with microelectronic systems still remains a huge challenge taking into full consideration the factors such as electrode film fabrication, high-resolution microelectrode pattern, and electrolyte precise deposition. In this review, we summarize the recent advances of ultrasmall and integrated MSCs with tunable performance and customizable function, including key microfabrication technologies for patterning microelectrodes with superior resolution, precise deposition of customized electrolytes in an extremely small space, and feasible strategies for improving electrochemical performance by constructing thick microelectrodes and special electrode structure. Finally, the related challenges and key prospects of ultracompact and customizable MSCs, including compatible microfabrication methods for electrode materials and films, patterning microelectrodes, customizing shape-conformable electrolytes, performance optimization, and efficient integration with microelectronic systems, are put forward for further promoting their practical application.

With the rapid development of flexible and portable microelectronics, the extreme demand for miniaturized, mechanically flexible, and integrated microsystems are strongly stimulated. Here, biomass-derived carbons (BDCs) are prepared by KOH activation using Qamgur precursor, exhibiting three-dimensional (3D) hierarchical porous structure. Benefiting from unobstructed 3D hierarchical porous structure, BDCs provide an excellent specific capacitance of 433 F g⁻¹ and prominent cyclability without capacitance degradation after 50000 cycles at 50 A g⁻¹. Furthermore, BDC-based planar micro-supercapacitors (MSCs) without metal collector, prepared by mask-assisted coating, exhibit outstanding areal-specific capacitance of 84 mF cm⁻² and areal energy density of 10.6 μWh cm⁻², exceeding most of the previous carbon-based MSCs. Impressively, the MSCs disclose extraordinary flexibility with capacitance retention of almost 100% under extreme bending state. More importantly, a flexible planar integrated system composed of the MSC and temperature sensor is assembled to efficiently monitor the temperature variation, providing a feasible route for flexible MSC-based functional micro-devices.

Aqueous zinc ion batteries (ZIBs) with intrinsic safety have great potentials in portable devices, but suffer from limited cycling life mainly caused by serious dendrite growth and unavoidable side reactions of Zn anodes. Herein, graphene interpenetrated Zn (GiZn) hybrid foils are developed for dendritefree and long-term Zn anodes for high-performance ZIBs. The GiZn anode is prepared by interfacial assembly of reduced graphene oxide (rGO) on the skeletons of zinc foams, followed by mechanical compression into hybrid foils and drying process. The presence of the rGO nanosheets in the GiZn hybrid foils provides abundant zincophilic sites to induce horizontal Zn deposition for Zn metal anodes without the growth of dendrites. Meanwhile, the uniform distribution of rGO nanosheets endows the hybrid foils with superior conductivity and wetting ability with electrolytes for reduced interfacial resistances. As a result, GiZn-based symmetric cells exhibit a small voltage hysteresis of 30.4 mV and remarkable areal capacity of 30 mAh cm⁻² at 0.5 mA cm⁻². Further, GiZn anodes also enable the corresponding aqueous Zn||MnO₂ batteries with high capacity of 168.5 mAh g⁻¹ at 8 C, superior to the counterpart with pure Zn foil anodes (72.7 mAh g⁻¹). Therefore, GiZn hybrid foil anodes will shed light on the rational construction of 2D material-interpenetrated Zn hybrid foil anodes for highperformance ZIBs.

Two-dimensional (2D) boron nitride (BN), the so-called “white graphene,” has demonstrated a great potential in various fields, particularly in electronics and energy, by utilizing its wide bandgap (~5.5 eV), superior thermal stability, high thermal conductance, chemical inertness, and outstanding dielectric properties. However, to further optimize the performances from the view of structure–property relationship, the determinative factors such as crystallite sizes, layer thickness, dispersibility, and surface functionalities should be precisely controlled and adjusted. Therefore, in this review, the synthesis and functionalization methods including “top-down” and “bottom-up” strategies, and non-covalent and covalent modifications for 2D BN are systematically classified and discussed at first, thus catering for the requirements of versatile applications. Then, the progresses of 2D BN applied in the fields of microelectronics such as field-effect transistors and dielectric capacitors, energy domains such as thermal energy management and conversion, and batteries and supercapacitors are summarized to highlight the importance of 2D BN. Notably, these contents not only contain the state-of-the-art 2D BN composites, but also bring the current novel design of 2D BN-based microelectronic units. Finally, the challenges and perspectives are proposed to better broaden the scope of this material. Therefore, this review will pave an all-around way for understanding, utilizing, and applying 2D BN in future electronics and energy applications.