Electrochemically Exfoliated Graphene Additive-Free Inks for 3D Printing Customizable Monolithic Integrated Micro-Supercapacitors on a Large Scale

Three-dimensional (3D) printing technology with enhanced fidelity can achieve multiple functionalities and boost electrochemical performance of customizable planar micro-supercapacitors (MSCs), however, precise structural control of additive-free graphene-based macro-assembly electrode for monolithic integrated MSCs (MIMSCs) remains challenging. Here, the large-scale 3D printing fabrication of customizable planar MIMSCs is reported utilizing additive-free, high-quality electrochemically exfoliated graphene inks, which is not required the conventional cryogenic assistance during the printing process and any post-processing reduction. The resulting MSCs reveal an extremely small engineering footprint of 0.025 cm2, exceptionally high areal capacitance of 4900 mF cm-2, volumetric capacitance of 195.6 F cm-3, areal energy density of 2.1 mWh cm-2, and unprecedented volumetric energy density of 23 mWh cm-3 for a single cell, surpassing most previously reported 3D printed MSCs. The 3D printed MIMSC pack is further demonstrated, with the maximum areal cell count density of 16 cell cm-2, the highest output voltage of 192.5 V and the largest output voltage per unit area of 56 V cm-2 up to date are achieved. This work presents an innovative solution for processing high-performance additive-free graphene ink and realizing the large-scale production of 3D printed MIMSCs for planar energy storage.

The status and challenging perspectives of 3D-printed micro-batteries

In the era of the Internet of Things and wearable electronics, 3D-printed micro-batteries with miniaturization, aesthetic diversity and high aspect ratio, have emerged as a recent innovation that solves the problems of limited design diversity, poor flexibility and low mass loading of materials associated with traditional power sources restricted by the slurry-casting method. Thus, a comprehensive understanding of the rational design of 3D-printed materials, inks, methods, configurations and systems is critical to optimize the electrochemical performance of customizable 3D-printed micro-batteries. In this review, we offer a key overview and systematic discussion on 3D-printed micro-batteries, emphasizing the close relationship between printable materials and printing technology, as well as the reasonable design of inks. Initially, we compare the distinct characteristics of various printing technologies, and subsequently emphatically expound the printable components of micro-batteries and general approaches to prepare printable inks. After that, we focus on the outstanding role played by 3D printing design in the device architecture, battery configuration, performance improvement, and system integration. Finally, the future challenges and perspectives concerning high-performance 3D-printed micro-batteries are adequately highlighted and discussed. This comprehensive discussion aims at providing a blueprint for the design and construction of next-generation 3D-printed micro-batteries.

Hybrid ion/electron interfacial regulation stabilizes the cobalt/oxygen redox of ultrahigh-voltage lithium cobalt oxide for fast-charging cyclability

High-voltage and fast-charging LiCoO2 (LCO) is key to high-energy/power-density Li-ion batteries. However, unstable surface structure and unfavorable electronic/ionic conductivity severely hinder its high-voltage fast-charging cyclability. Here, we construct a Li/Na-B-Mg-Si-O-F-rich mixed ion/electron interface network on the 4.65 V LCO electrode to enhance its rate capability and long-term cycling stability. Specifically, the resulting artificial hybrid conductive network enhances the reversible conversion of Co3+/4+/O2-/n- redox by the interfacial ion-electron cooperation and suppresses interface side reactions, inducing an ultrathin yet compact cathode electrolyte interphase. Simultaneously, the derived near-surface Na+/Mg2+/Si4+-pillared local intercalation structure greatly promotes the Li+ diffusion around the 4.55 V phase transition and stabilizes the cathode interface. Finally, excellent 3 C (1 C = 274 mA g-1) fast charging performance is demonstrated with 73.8% capacity retention over 1000 cycles. Our findings shed new insights to the fundamental mechanism of interfacial ion/electron synergy in stabilizing and enhancing fast-charging cathode materials.

Monolithically integrated micro-supercapacitors with high areal number density produced by surface adhesive-directed electrolyte assembly

Accurately placing very small amounts of electrolyte on tiny micro-supercapacitors (MSCs) arrays in close proximity is a major challenge. This difficulty hinders the development of densely-compact monolithically integrated MSCs (MIMSCs). To overcome this grand challenge, we demonstrate a controllable electrolyte directed assembly strategy for precise isolation of densely-packed MSCs at micron scale, achieving scalable production of MIMSCs with ultrahigh areal number density and output voltage. We fabricate a patterned adhesive surface across MIMSCs, that induce electrolyte directed assembly on 10,000 highly adhesive MSC regions, achieving a 100 µm-scale spatial separation between each electrolyte droplet within seconds. The resultant MIMSCs achieve an areal number density of 210 cells cm-2 and a high areal voltage of 555 V cm-2. Further, cycling the MIMSCs at 190 V over 9000 times manifests no performance degradation. A seamlessly integrated system of ultracompact wirelessly-chargeable MIMSCs is also demonstrated to show its practicality and versatile applicability.

Metal telluride nanosheets by scalable solid lithiation and exfoliation

Transition metal tellurides (TMTs) have been ideal materials for exploring exotic properties in condensed-matter physics, chemistry and materials science1-3. Although TMT nanosheets have been produced by top-down exfoliation, their scale is below the gram level and requires a long processing time, restricting their effective application from laboratory to market4-8. We report the fast and scalable synthesis of a wide variety of MTe2 (M = Nb, Mo, W, Ta, Ti) nanosheets by the solid lithiation of bulk MTe2 within 10 min and their subsequent hydrolysis within seconds. Using NbTe2 as a representative, we produced more than a hundred grams (108 g) of NbTe2 nanosheets with 3.2 nm mean thickness, 6.2 µm mean lateral size and a high yield (>80%). Several interesting quantum phenomena, such as quantum oscillations and giant magnetoresistance, were observed that are generally restricted to highly crystalline MTe2 nanosheets. The TMT nanosheets also perform well as electrocatalysts for lithium-oxygen batteries and electrodes for microsupercapacitors (MSCs). Moreover, this synthesis method is efficient for preparing alloyed telluride, selenide and sulfide nanosheets. Our work opens new opportunities for the universal and scalable synthesis of TMT nanosheets for exploring new quantum phenomena, potential applications and commercialization.

Recent advancement and key opportunities of MXenes for electrocatalysis

MXenes are promising materials for electrocatalysis due to their excellent metallic conductivity, hydrophilicity, high specific surface area, and excellent electrochemical properties. Herein, we summarize the recent advancement of MXene-based materials for electrocatalysis and highlight their key challenges and opportunities. In particular, this review emphasizes on the major design principles of MXene-based electrocatalysts, including (1) coupling MXene with active materials or heteroatomic doping to create highly active synergistic catalyst sites; (2) construction of 3D MXene structure or introducing interlayer spacers to increase active areas and form fast mass-charge transfer channel; and (3) protecting edge of MXene or in situ transforming the surface of MXene to stable active substance that inhibits the oxidation of MXene and then enhances the stability. Consequently, MXene-based materials exhibit outstanding performance for a variety of electrocatalytic reactions. Finally, the key challenges and promising prospects of the practical applications of MXene-based electrocatalysts are briefly proposed.

Recent Advances in Flexible Wearable Supercapacitors: Properties, Fabrication, and Applications

A supercapacitor is a potential electrochemical energy storage device with high-power density (PD) for driving flexible, smart, electronic devices. In particular, flexible supercapacitors (FSCs) have reliable mechanical and electrochemical properties and have become an important part of wearable, smart, electronic devices. It is noteworthy that the flexible electrode, electrolyte, separator and current collector all play key roles in overall FSCs. In this review, the unique mechanical properties, structural designs and fabrication methods of each flexible component are systematically classified, summarized and discussed based on the recent progress of FSCs. Further, the practical applications of FSCs are delineated, and the opportunities and challenges of FSCs in wearable technologies are proposed. The development of high-performance FSCs will greatly promote electricity storage toward more practical and widely varying fields. However, with the development of portable equipment, simple FSCs cannot satisfy the needs of integrated and intelligent flexible wearable devices for long durations. It is anticipated that the combining an FSC and a flexible power source such as flexible solar cells is an effective strategy to solve this problem. This review also includes some discussions of flexible self-powered devices.

Breaking the Ru-O-Ru Symmetry of a RuO2 Catalyst for Sustainable Acidic Water Oxidation

Proton exchange membrane water electrolysis is a highly promising hydrogen production technique for sustainable energy supply, however, achieving a highly active and durable catalyst for acidic water oxidation still remains a formidable challenge. Herein, we propose a local microenvironment regulation strategy for precisely tuning In-RuO2 /graphene (In-RuO2 /G) catalyst with intrinsic electrochemical activity and stability to boost acidic water oxidation. The In-RuO2 /G displays robust acid oxygen evolution reaction performance with a mass activity of 671 A gcat -1 at 1.5 V, an overpotential of 187 mV at 10 mA cm-2 , and long-lasting stability of 350 h at 100 mA cm-2 , which arises from the asymmetric Ru-O-In local structure interactions. Further, it is unraveled theoretically that the asymmetric Ru-O-In structure breaks the thermodynamic activity limit of the traditional adsorption evolution mechanism which significantly weakens the formation energy barrier of OOH*, thus inducing a new rate-determining step of OH* absorption. Therefore, this strategy showcases the immense potential for constructing high-performance acidic catalysts for water electrolyzers.

Hierarchically Structured Nb2O5 Microflowers with Enhanced Capacity and Fast-Charging Capability for Flexible Planar Sodium Ion Micro-Supercapacitors

Highlights

Hierarchically structured Nb2O5 microflowers consiste of porous and ultrathin nanosheets. Nb2O5 microflowers exhibit enhanced capacity and rate performance boosting Na ion storage. Planar NIMSCs with charge and kinetics matching show superior areal capacitance and lifespan.

Abstract

Planar Na ion micro-supercapacitors (NIMSCs) that offer both high energy density and power density are deemed to a promising class of miniaturized power sources for wearable and portable microelectronics. Nevertheless, the development of NIMSCs are hugely impeded by the low capacity and sluggish Na ion kinetics in the negative electrode. Herein, we demonstrate a novel carbon-coated Nb2O5 microflower with a hierarchical structure composed of vertically intercrossed and porous nanosheets, boosting Na ion storage performance. The unique structural merits, including uniform carbon coating, ultrathin nanosheets and abundant pores, endow the Nb2O5 microflower with highly reversible Na ion storage capacity of 245 mAh g−1 at 0.25 C and excellent rate capability. Benefiting from high capacity and fast charging of Nb2O5 microflower, the planar NIMSCs consisted of Nb2O5 negative electrode and activated carbon positive electrode deliver high areal energy density of 60.7 μWh cm−2, considerable voltage window of 3.5 V and extraordinary cyclability. Therefore, this work exploits a structural design strategy towards electrode materials for application in NIMSCs, holding great promise for flexible microelectronics.

Supplementary Information

The online version contains supplementary material available at 10.1007/s40820-023-01281-5.

Protocol for fabrication of Pt/RuO2/graphene bifunctional oxygen catalyst in Li-O2 batteries

The commercial mass production of bifunctional oxygen catalysts with high activity and stability is critical for constructing high-performance lithium-oxygen (Li-O2) batteries, but remains challenging. Herein, we describe a protocol for the scalable fabrication of a 2D bifunctional electrocatalyst of Pt/RuO2/graphene by spatial confinement strategy and elaborately evaluate its oxygen reduction/evolution reactions for advanced Li-O2 batteries. We then detail the synthesis steps for preparing materials followed by assembly and evaluation of the three-electrode systems and coin-type Li-O2 batteries. For complete details on the use and execution of this protocol, please refer to Li et al. (2023).1.

A Biodegradable High-Performance Microsupercapacitor for Environmentally Friendly and Biocompatible Energy Storage

Biodegradable and biocompatible microscale energy storage devices are very crucial for environmentally friendly microelectronics and implantable medical applications. Herein, a biodegradable and biocompatible microsupercapacitor (BB-MSC) with satisfying overall performance is realized via the combination of three-dimensional (3D) printing technique and biodegradable materials. Due to the 3D-interconnected structure of electrodes and elaborated design of electrolyte, the as-prepared BB-MSC exhibits superior overall performance than most of biodegradable devices, including a wide operation voltage of 1.8 V, high areal specific capacitance of 251 mF/cm2, good cycle stability, and favorable low-temperature resistance (-20 °C), demonstrative of reliability and practicality of our devices even in frosty environments. Importantly, the smooth degradation has been realized for the BB-MSC after being buried in natural soil for ∼90 days, and its implantation does not affect the healthy status of SD rats. Therefore, this work explores avenues for the design and construction of environmentally friendly and biocompatible microscale energy storage devices.

Aqueous Organic Batteries Using the Proton as a Charge Carrier

Benefiting from the merits of low cost, nonflammability, and high operational safety, aqueous rechargeable batteries have emerged as promising candidates for large-scale energy-storage applications. Among various metal-ion/non-metallic charge carriers, the proton (H+ ) as a charge carrier possesses numerous unique properties such as fast proton diffusion dynamics, a low molar mass, and a small hydrated ion radius, which endow aqueous proton batteries (APBs) with a salient rate capability, a long-term life span, and an excellent low-temperature electrochemical performance. In addition, redox-active organic molecules, with the advantages of structural diversity, rich proton-storage sites, and abundant resources, are considered attractive electrode materials for APBs. However, the charge-storage and transport mechanisms of organic electrodes in APBs are still in their infancy. Therefore, finding suitable electrode materials and uncovering the H+ -storage mechanisms are significant for the application of organic materials in APBs. Herein, the latest research progress on organic materials, such as small molecules and polymers for APBs, is reviewed. Furthermore, a comprehensive summary and evaluation of APBs employing organic electrodes as anode and/or cathode is provided, especially regarding their low-temperature and high-power performances, along with systematic discussions for guiding the rational design and the construction of APBs based on organic electrodes.

High-Voltage MXene-Based Supercapacitors: Present Status and Future Perspectives

As an emerging class of 2D materials, MXene exhibits broad prospects in the field of supercapacitors (SCs). However, the working voltage of MXene-based SCs is relatively limited (typically ≤ 0.6 V) due to the oxidation of MXene electrode and the decomposition of electrolyte, ultimately leading to low energy density of the device. To solve this issue, high-voltage MXene-based electrodes and corresponding matchable electrolytes are developed urgently to extend the voltage window of MXene-based SCs. Herein, a comprehensive overview and systematic discussion regarding the effects of electrolytes (aqueous, organic, and ionic liquid electrolytes), asymmetric device configuration, and material modification on the operating voltage of MXene-based SCs, is presented. A deep dive is taken into the latest advances in electrolyte design, structure regulation, and high-voltage mechanism of MXene-based SCs. Last, the future perspectives on high-voltage MXene-based SCs and their possible development directions are outlined and discussed in depth, providing new insights for the rational design and realization of advanced next-generation MXene-based electrodes and high-voltage electrolytes.

Natural-Wood-Inspired Ultrastrong Anisotropic Hybrid Hydrogels Targeting Artificial Tendons or Ligaments

Hydrogels are able to mimic the flexibility of biological tissues or skin, but they still cannot achieve satisfactory strength and toughness, greatly limiting their scope of application. Natural wood can offer inspiration for designing high-strength hydrogels attributed to its anisotropic structure. Herein, we propose an integrated strategy for efficient preparation of ultrastrong hydrogels using a salting-assisted prestretching treatment. The as-prepared poly(vinyl alcohol)/cellulose nanofiber hybrid hydrogels show distinct wood-like anisotropy, including oriented molecular fiber bundles and extended grain size, which endows materials with extraordinarily comprehensive mechanical properties of ultimate breaking strength exceeding 40 MPa, strain approaching 250%, and toughness exceeding 60 MJ·m^-3, and outstanding tear resistance. Impressively, the breaking strength and toughness of the reswollen preoriented hydrogels approach 10 MPa and 25 MJ·m^-3, respectively. In vitro and in vivo tests demonstrate that the reswollen hydrogels do not affect the growth and viability of the cells, nor do they cause the inflammation or rejection of the mouse tissue, implying extremely low biotoxicity and perfect histocompatibility, showcasing bright prospects for application in artificial ligaments or tendons. The strategy provided in this study can be generalized to a variety of biocompatible polymers for the fabrication of high-performance hydrogels with anisotropic structures.

[Deepening the Action on Salt Reduction in China-suggestions on strategy and implementation plan]

Excessive sodium/salt intake is the leading dietary risk factor for the loss of healthy life in the Chinese population. The "Healthy China 2030" Action Plan set the goal of reducing salt intake by 20% by 2030. However, salt intake in China is still at a very high level in the world, with adults reaching 11 g/d, more than twice the recommended limit of 5 g/d. The current policies and action plans of China have targeted catering workers, children, adolescents, and home chefs in salt, oil, and sugar reduction actions. However, there are still obvious deficiencies in the coordinated promotion and implementation. This study, therefore, proposed a set of comprehensive strategies (named CHRPS that is composed of communication and education, salt reduction in home cooking, salt reduction in restaurants, reducing salt content in pre-packaged food, and surveillance and evaluation) and key implementation points for further deepening the salt reduction action in China. These strategies were developed based on the main sources of dietary sodium for Chinese residents, the status of"knowledge, attitude and practice"in salt reduction, evidence of effective intervention measures, existing policies and requirements, and the salt reduction strategies of the World Health Organization and experience from some other countries. As a scientific reference, the CHRPS strategies will help the government and relevant organizations quickly implement salt reduction work and facilitate the earlier realization of China's salt reduction goal.

Vapor-Liquid-Solid Growth of Site-Controlled Monolayer MoS2 Films Via Pressure-Induc ed Supercritical Phase Nucleation

In this study, a novel pressure-induced supercritical phase nucleation method is proposed to synthesize monolayer MoS₂ films, which is promoter free and can avoid contamination of films derived from these heterogeneous promoters in most of the existing techniques. The low-crystallinity and size-controlled MoO₂(acac)₂ particles are recrystallized on the substrate via the pressure-sensitive solvent capacity of supercritical CO₂ and these particles are used as growth sites. The size of single-crystal MoS₂ on the substrate is found to be dependent on the wetting area of the pyrolyzed precursor droplets (MoO₂) on the surface, and the formation of continuous films with high coverage is mainly controlled by the coalescence of MoO₂ droplets. It is enhanced by the increase of the nucleation site density, which can be adjusted by the supersaturation of the supercritical fluid solution. Our findings pave a new way for the controllable growth of MoS₂ and other two-dimensional materials and provide sufficient and valuable evidence for vapor-liquid-solid growth.

Monolithic integrated micro-supercapacitors with ultra-high systemic volumetric performance and areal output voltage

Monolithic integrated micro-supercapacitors (MIMSCs) with high systemic performance and cell-number density are important for miniaturized electronics to empower the Internet of Things. However, fabrication of customizable MIMSCs in an extremely small space remains a huge challenge considering key factors such as materials selection, electrolyte confinement, microfabrication and device-performance uniformity. Here, we develop a universal and large-throughput microfabrication strategy to address all these issues by combining multistep lithographic patterning, spray printing of MXene microelectrodes and controllable 3D printing of gel electrolytes. We achieve the monolithic integration of electrochemically isolated micro-supercapacitors in close proximity by leveraging high-resolution micropatterning techniques for microelectrode deposition and 3D printing for precise electrolyte deposition. Notably, the MIMSCs obtained demonstrate a high areal-number density of 28 cells cm^-2 (340 cells on 3.5 × 3.5 cm²), a record areal output voltage of 75.6 V cm^-2, an acceptable systemic volumetric energy density of 9.8 mWh cm^-3 and an unprecedentedly high capacitance retention of 92% after 4000 cycles at an extremely high output voltage of 162 V. This work paves the way for monolithic integrated and microscopic energy-storage assemblies for powering future microelectronics.

Designing Solid Electrolyte Interfaces towards Homogeneous Na Deposition: Theoretical Guidelines for Electrolyte Additives and Superior High-Rate Cycling Stability

Metallic Na is a promising metal anode for large-scale energy storage. Nevertheless, unstable solid electrolyte interphase (SEI) and uncontrollable Na dendrite growth lead to disastrous short circuit and poor cycle life. Through phase field and ab initio molecular dynamics simulation, we first predict that the sodium bromide (NaBr) with the lowest Na ion diffusion energy barrier among sodium halogen compounds (NaX, X=F, Cl, Br, I) is the ideal SEI composition to induce the spherical Na deposition for suppressing dendrite growth. Then, 1,2-dibromobenzene (1,2-DBB) additive is introduced into the common fluoroethylene carbonate-based carbonate electrolyte (the corresponding SEI has high mechanical stability) to construct a desirable NaBr-rich stable SEI layer. When the Na||Na₃ V₂ (PO₄ )₃ cell utilizes the electrolyte with 1,2-DBB additive, an extraordinary capacity retention of 94 % is achieved after 2000 cycles at a high rate of 10 C. This study provides a design philosophy for dendrite-free Na metal anode and can be expanded to other metal anodes.

A Thermoregulatory Flexible Phase Change Nonwoven for All-Season High-Efficiency Wearable Thermal Management

Phase change materials have a key role for wearable thermal management, but suffer from poor water vapor permeability, low enthalpy value and weak shape stability caused by liquid phase leakage and intrinsic rigidity of solid-liquid phase change materials. Herein, we report for the first time a versatile strategy for designed assembly of high-enthalpy flexible phase change nonwovens (GB-PCN) by wet-spinning hybrid graphene-boron nitride (GB) fiber and subsequent impregnating paraffins (e.g., eicosane, octadecane). As a result, our GB-PCN exhibited an unprecedented enthalpy value of 206.0 J g-1, excellent thermal reliability and anti-leakage capacity, superb thermal cycling ability of 97.6% after 1000 cycles, and ultrahigh water vapor permeability (close to the cotton), outperforming the reported PCM films and fibers to date. Notably, the wearable thermal management systems based on GB-PCN for both clothing and face mask were demonstrated, which can maintain the human body at a comfortable temperature range for a significantly long time. Therefore, our results demonstrate huge potential of GB-PCN for human-wearable passive thermal management in real scenarios.

Rational Design of an Artificial SEI: Alloy/Solid Electrolyte Hybrid Layer for a Highly Reversible Na and K Metal Anode

The practical application of a Na/K-metallic anode is intrinsically hindered by the poor cycle life and safety issues due to the unstable electrode/electrolyte interface and uncontrolled dendrite growth during cycling. Herein, we solve these issues through an in situ reaction of an oxyhalogenide (BiOCl) and Na to construct an artificial solid electrolyte interphase (SEI) layer consisting of an alloy (Na₃Bi) and a solid electrolyte (Na₃OCl) on the surface of the Na anode. As demonstrated by theoretical and experimental results, such an artificial SEI layer combines the synergistic properties of high ionic conductivity, electronic insulation, and interfacial stability, leading to uniform dendrite-free Na deposition beneath the hybrid SEI layer. The protected Na anode presents a low voltage polarization of 30 mV, achieving an extended cycling life of 700 h at 1 mA cm^-2 in the carbonate-based electrolyte. The full cell based on the Na₃V₂(PO₄)₃ cathode and hybrid SEI-protected Na anode shows long-term stability. When this strategy is applied to a K metal anode, the protected K anode also reaches a cycling life of over 4000 h at 0.5 mA cm^-2 with a low voltage polarization of 100 mV. Our work provides an important insight into the design principles of a stable artificial SEI layer for high-energy-density metal batteries.

3D Printing Flexible Sodium-Ion Microbatteries with Ultrahigh Areal Capacity and Robust Rate Capability

Rechargeable sodium-ion microbatteries (NIMBs) constructed using low-cost and abundant raw materials in planar configuration with both cathode and anode on the same substrate hold promise for powering coplanar microelectronics, but are hindered by the low areal capacity owing to the thin microelectrodes. Here, a prototype of planar and flexible 3D-printed NIMBs is demonstrated with 3D interconnected conductive thick microelectrodes for ultrahigh areal capacity and boosted rate capability. Rationally optimized 3D printable inks with appropriate viscosities and high conductivity allow the multilayer printing of NIMB microelectrodes reaching a very high thickness of ≈1200 µm while maintaining effective ion and electron-transfer pathways in them. Consequently, the 3D-printed NIMBs deliver superior areal capacity of 4.5 mAh cm^-2 (2 mA cm^-2 ), outperforming the state-of-the-art printed microbatteries. The NIMBs show enhanced rate capability with 3.6 mAh cm^-2 at 40 mA cm^-2 and robust long-term cycle life up to 6000 cycles. Furthermore, the planar NIMB microelectrodes, despite the large thickness, exhibit decent mechanical flexibility under various bending conditions. This work opens a new avenue for the construction of high-performance NIMBs with thick microelectrodes capable of powering flexible microelectronics.

Multifunctional Mesoporous Polyaniline/Graphene Nanosheets for Flexible Planar Integrated Microsystem of Zinc Ion Microbattery and Gas Sensor

The prosperity of smart portable microdevices urgently requires an advanced integrated microsystem equipped with cost-effective safe microbatteries and ultra-stable sensitive sensors. However, the practical application of smart microdevices is limited by complex active materials with single function. Here, the two-dimensional (2D) mesoporous nanosheets of polyaniline decorated on graphene with large specific surface area of 141 m²  g^-1 , ample active sites, comparable conductivity, and ordered mesopores of 18 nm for a new-type co-planar integrated microsystem of zinc ion microbattery and gas sensor are developed. These unique triple-function mesoporous nanosheets are well proved for dendrite-free zinc anode with long cyclability (>500 h) and small overpotential (48 mV), a high performance cathode of zinc ion microbattery with outstanding volumetric capacity of 78 mAh cm^-3 outperforming their counterparts reported, and a highly sensitive gas sensor with a resistance response (ΔR/R₀ %) of 118% for 20 ppm NH₃ . Moreover, the co-planar battery-sensor integrated microsystem exhibits superior mechanical stability and smart integration. Therefore, this work will open many opportunities to develop multifunctional 2D mesoporous materials for high performance smart integrated microsystems.

K-Functionalized Carbon Quantum Dots-Induced Interface Assembly of Carbon Nanocages for Ultrastable Potassium Storage Performance

Carbon nanocages (CNCs), with unique merits of morphology and structure, have attracted increasing attention for energy storage and conversion. However, the synthesis of CNCs reported so far suffers from relatively harsh conditions and expensive raw materials. Herein, porous CNCs are intelligently designed using low-cost glucose as the carbon precursor via a facile K-functionalized carbon quantum dots (K-CQDs)-induced assembly route under hydrothermal process. The resulting CNCs have a unique cage-like structure, large surface area, and rich carboxyl groups. With these elegant structural merits, the as-made CNCs anode shows a high reversible capacity of 270 mAh g^-1 at 100 mA g^-1 after 200 cycles and a long-term cycling stability of 206 mAh g^-1 at 2000 mA g^-1 after 4000 cycles. An intercalation reaction mechanism with the K⁺ intercalation compound is further identified through an in-situ Raman technique. Density functional theory simulations reveal that abundant carboxyl groups inherited from K-CQDs can significantly promote the potassium storage capacities of the CNCs electrode.

Multi-Layer Printable Lithium Ion Micro-Batteries with Remarkable Areal Energy Density and Flexibility for Wearable Smart Electronics

Pursuing high areal energy density and developing scalable fabrication strategies of micro-batteries are the key for the progressive printed microelectronics. Herein, the scalable fabrication of multi-layer printable lithium ion micro-batteries (LIMBs) with ultrahigh areal energy density and exceptional flexibility is reported, based on highly conductive and mechanically stable inks by fully incorporating the polyurethane binders in dibasic esters with high-conducting additives of graphene and carbon nanotubes into active materials to construct a cross-linked conductive network. Benefiting from relatively higher electrical conductivity (≈7000 mS cm^-1 ) and stably connected network of microelectrodes, the as-fabricated LIMBs by multi-layer printing display robust areal capacity of 398 µAh cm^-2 , and remarkable areal energy density of 695 μWh cm^-2 , which are much higher than most LIMBs reported. Further, the printed LIMBs show notable capacity retention of 88% after 3000 cycles, and outstanding flexibility without any structure degradation under various torsion states and folding angles. Importantly, a wearable smart bracelet, composed of a serially connected LIMBs pack, a temperature sensor, and a light-emitting diode, is realized for the automatic detection of body temperature. Therefore, this strategy of fabricating highly conductive and mechanically stable printable ink will open a new avenue for developing high-performance printable LIMBs for smart microelectronics.

OUP accepted manuscript

MXenes are one of the key materials for micro-supercapacitors (MSCs), integrating miniaturized energy-storage components with microelectronics. However, the energy densities of MSCs are greatly hampered by MXenes’ narrow working potential window (typically ≤0.6 V) in aqueous electrolytes. Here, we report the fabrication of high-voltage MXene-MSCs through the efficient regulation of reaction kinetics in 2D Ti₃C₂T_x MXene microelectrodes using a water-in-LiCl (WIL, 20 m LiCl) salt gel electrolyte. Importantly, the intrinsic energy-storage mechanism of MXene microelectrodes in WIL, which is totally different from traditional electrolytes (1 m LiCl), was revealed through insitu and exsitu characterizations. We validated that the suppression of MXene oxidation at high anodic potential occurred due to the high content of WIL regulating anion intercalation in MXene electrodes, which effectively broadened the voltage window of MXene-MSCs. Remarkably, the symmetric planar MXene-MSCs presented a record operating voltage of 1.6 V, resulting in an exceptionally high volumetric energy density of 31.7 mWh cm⁻³. With the ultra-high ionic conductivity (69.5 mS cm⁻¹) and ultralow freezing point (−57°C) of the WIL gel electrolyte, our MSCs could be operated in a wide temperature range of −40 to 60°C, and worked for a long duration even at −40°C, demonstrative of its practicality in extreme environments.

In Situ Modulation of A-Site Vacancies in LaMnO3.15 Perovskite for Surface Lattice Oxygen Activation and Boosted Redox Reactions

Modulation of A-site defects is crucial to the redox reactions on ABO₃ perovskites for both clean air application and electrochemical energy storage. Herein we report a scalable one-pot strategy for in situ regulation of La vacancies (V_La ) in LaMnO_3.15 by simply introducing urea in the traditional citrate process, and further reveal the fundamental relationship between V_La creation and surface lattice oxygen (O_latt ) activation. The underlying mechanism is shortened Mn-O bonds, decreased orbital ordering, promoted MnO₆ bending vibration and weakened Jahn-Teller distortion, ultimately realizing enhanced Mn-3d and O-2p orbital hybridization. The LaMnO_3.15 with optimized V_La exhibits order of magnitude increase in toluene oxidation and ca. 0.05 V versus RHE (reversible hydrogen electrode) increase of half-wave potential in oxygen reduction reaction (ORR). The reported strategy can benefit the development of novel defect-meditated perovskites in both heterocatalysis and electrocatalysis.

Scalable Production of Freestanding Few-Layer β12-Borophene Single Crystalline Sheets as Efficient Electrocatalysts for Lithium-Sulfur Batteries

Two-dimensional (2D) borophene has attracted tremendous interest due to its fascinating properties, which have potential applications in catalysts, energy storage devices, and high-speed transistors. In the past few years, borophene was theoretically predicted as an ideal electrode material for lithium-sulfur (Li-S) batteries because of its low-density, metallic conductivity, high Li-ion surface mobility, and strong interface bonding energy to polysulfide. But until now, borophene-based Li-S batteries have not yet been achieved in experiments due to the absence of a large-scale synthetic method of freestanding borophene nanostructures with a high enough structural stability, conductivity, and uniformity. Herein, we developed a low-temperature liquid exfoliation (LTLE) method to synthesize freestanding few-layer β₁₂-borophene single-crystalline sheets with a P6¯m2 symmetry in tens of milligrams. The as-synthesized 2D sheets were used as the polysulfide immobilizers and electrocatalysts of Li-S batteries. The resulting borophene-based Li-S battery delivered an extralarge areal capacity of 5.2 mAh cm^-2 at a high sulfur loading of 7.8 mg cm^-2, an excellent rate performance of 8 C (@721 mAh g^-1), and an ultralow capacity fading rate of 0.039% in 1000 cycles, outperforming commercial Li-ion batteries and many other 2D material-based Li-S batteries. Based on the density functional theory model, the excellent electrochemical performances of the borophene-based Li-S batteries should originate from the enormous enhancement of β₁₂-borophene sheets for both the surface migration of the Li-ions and the adsorption energy of Li₂S_n clusters. Our results thus demonstrate a great potential for scalable production of freestanding β₁₂-borophene single-crystalline sheets in future high-performance Li-S batteries.

α-MnO2/MWCNTs as an electrocatalyst for rechargeable relatively closed system Li-O2 batteries

Herein, a new, relatively closed system Li-O₂ (RCLO) battery, without extra oxygen being involved in the reaction during the charge and discharge process, is reported. This relatively closed system effectively solves the key issue of poor circulation caused by oxygen generation in conventional Li-O₂ batteries.

Phosphorus doping and phosphates coating for nickel molybdate/nickel molybdate hydrate enabling efficient overall water splitting

Earth-abundant transition metal-based bifunctional electrocatalysts are promising alternatives to noble metals for overall water electrolysis, but restricted by low activity and durability. Herein, a three-dimensional phosphorus-doped nickel molybdate/nickel molybdate hydrate @phosphates core-shell nanorod clusters on nickel foam self-supported electrode was fabricated by a combined hydrothermal and phosphating process. The phosphorus doping and phosphate coating induced by phosphating process bring in a synergistic effect to improve the electrical conductivity, provide abundant active surface sites and accelerate the surface reaction for nickel molybdate/nickel molybdate hydrate (NiMoO₄/NiMoO₄·nH₂O) heterostructures. These advantages enable the self-supported electrode to exhibit high hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) activity in 1.0 M KOH with low overpotentials of 148 and 260 mV at 10 mA cm^-2, respectively. When it was employed both as anode and cathode, a cell voltage of 1.62 V is only required to reach the current density of 10 mA cm^-2 in alkaline solution. Especially, the self-supported electrode reveals outstanding durability, which could maintain over 25 h at 10 mA cm^-2 for HER, OER or overall water splitting. This work provides a novel avenue to enhance the electrocatalytic performance of the catalysts by synergistically modulating the intrinsic electrical conductivity, active surface sites and surface reaction.

[Opportunities and challenges of schistosomiasis control during the construction of the Chengdu-Chongqing economic circle]

Chengdu-Chongqing economic circle is centered on Chengdu City and Chongqing Municipality, with aims to build the "fourth growth pole" of China's economy. During this circle, elimination of schistosomiasis had been achieved in 82.5% of the endemic counties (districts) of Sichuan Province, and schistosomiasis is not historically endemic in Chongqing Municipality; however, there is still a risk of schistosmiasis transmission in Sichuan Province and Chongqing Municipality because the natural and social factors affecting schistosomiasis transmission have not been completely eliminated in these areas. Based on the endemic situation of schistosomiasis in Sichuan Province and Chongqing Municipality, we analyzed the opportunities and challenges of schistosomiasis control during the construction of Chengdu-Chongqing economic circle, and proposed the corresponding suggestions, so as to provide insights into the sustainable development of schistosomiasis control in the context of the Chengdu-Chongqing economic circle construction.

Multitasking MXene Inks Enable High-Performance Printable Microelectrochemical Energy Storage Devices for All-Flexible Self-Powered Integrated Systems

The future of mankind holds great promise for things like the Internet of Things, personal health monitoring systems, and smart cities. To achieve this ambitious goal, it is imperative for electronics to be wearable, environmentally sustainable, and safe. However, large-scale manufacture of self-sufficient electronic systems by exploiting multifunctional materials still faces significant hurdles. Herein, multitasking aqueous printable MXene inks are reported as an additive-free high-capacitance electrode, sensitive pressure-sensing material, highly conducting current collector, metal-free interconnector, and conductive binder. By directly screen printing MXene inks, MXene-based micro-supercapacitors (MSCs) and lithium-ion microbatteries (LIMBs) are delicately fabricated on various substrates. The as-prepared MSCs exhibit ultrahigh areal capacitance of 1.1 F cm^-2 and the serially connected MSCs offer a record voltage of 60 V. The quasi-solid-state LIMBs deliver a robust areal energy density of 154 μWh cm^-2 . Furthermore, an all-flexible self-powered integrated system on a single substrate based on the multitasking MXene inks is demonstrated through seamless integration of a tandem solar cell, the LIMB, and an MXene hydrogel pressure sensor. Notably, this integrated system is exceptionally sensitive to body movements with a fast response time of 35 ms. Therefore, this multipurpose MXene ink opens a new avenue for powering future smart appliances.

[Surgical treatment of primary liver cancer:a report of 10 966 cases]

Objective: To summarize the experience of surgical treatment of primary liver cancer. Methods: The clinical data of 10 966 surgically managed cases with primary liver cancer, from January 1986 to December 2019 at Hepatobiliary Center, the First Affiliated Hospital of Nanjing Medical University, were retrospectively analyzed. The life table method was used to calculate the survival rate and postoperative recurrence rate. Log-rank test was used to compare the survival process of different groups, and the Cox regression model was used for multivariate analysis. In addition, 2 884 cases of hepatocellular carcinoma(HCC) with more detailed follow-up data from 2009 to 2019 were selected for survival analysis. Among 2 549 patients treated with hepatectomy, there were 2 107 males and 442 females, with an age of (56.6±11.1) years (range: 20 to 86 years). Among 335 patients treated with liver transplantation, there were 292 males and 43 females, with an age of (51.0±9.7) years (range: 21 to 73 years). The outcomes of hepatectomy versus liver transplantation, anatomic versus non-anatomic hepatectomy were compared, respectively. Results: Of the 10 966 patients with primary liver cancer, 10 331 patients underwent hepatectomy and 635 patients underwent liver transplantation. Patients with liver resection were categorized into three groups: 1986－1995(712 cases), 1996－2008(3 988 cases), 2009‒2019(5 631 cases). The 5-year overall survival rate was 32.9% in the first group(1986－1995). The 5-year overall survival rate of resected primary liver cancer was 51.7% in the third group(2009-2019), among which the 5-year overal survival rates of hepatocellular carcinoma, intrahepatic cholangiocarcinoma and mixed liver cancer were 57.4%, 26.6% and 50.6%, respectively. Further analysis was performed on 2 549 HCC patients with primary hepatectomy. The 1-, 3-, 5-, and 10-year overall survival rates were 88.1%, 71.9%, 60.0%, and 41.0%, respectively, and the perioperative mortality rate was 1.0%. Two hundred and forty-seven HCC patients underwent primary liver transplantation, with 1-, 3-, 5-, and 10-year overall survival rates of 84.0%, 64.8%, 61.9%, and 57.6%, respectively. Eighty-eight HCC patients underwent salvage liver transplantation, with the 1-, 3-, 5-, and 10-year overall survival rates of 86.8%, 65.2%, 52.5%, and 52.5%, respectively. There was no significant difference in survival rates between the two groups with liver transplantation (P>0.05). Comparing the overall survival rates and recurrence rates of primary hepatectomy (2 549 cases) with primary liver transplantation (247 cases), the 1-, 3-, 5-, and 10-year overall survival rates in patients within Milan criteria treated with hepatectomy and transplantation were 96.3%, 87.1%, 76.9%, 54.7%, and 95.4%, 79.4%, 77.4%, 71.7%, respectively (P=0.754). The 1-, 3-, 5-year recurrence rates were 16.3%, 35.9%, 47.6% and 8.1%, 11.7%, 13.9%, respectively(P<0.01). The 1-, 3-, 5-, 10-year overall survival rates in patients with no large vessels invasion beyond the Milan criteria treated with liver resection and transplantation were 87.2%, 65.9%, 53.0%, 33.0% and 87.6%, 71.8%, 71.8%, 69.3%, respectively(P=0.003); the 1-, 3-, 5-year recurrence rate were 39.2%, 57.8%, 69.7% and 29.7%, 36.7%, 36.7%, respectively (P<0.01). The 1-, 3-, 5-, and 10-year overall survival rates in patients with large vessels invasion treated with liver resection and transplantation were 62.1%, 36.1%, 22.2%, 15.0% and 62.9%, 31.8%,19.9%, 0, respectively (P=0.387); the 1-, 3-, 5-year recurrence rates were 61.5%, 74.7%, 80.8% and 59.7%, 82.9%, 87.2%, respectively(P=0.909). Independent prognostic factors for both overall survival and recurrence-free survival rates of HCC patients treated with liver resection included gender, neoadjuvant therapy, symptoms, AST, intraoperative or postoperative blood transfusion, tumor number, tumor size, cirrhosis, macrovascular invasion, microvascular invasion, and pathological differentiation. Propensity score matching analysis of 443 pairs further showed that there was no significant difference in overall survival rate between anatomical liver resection and non-anatomical liver resection(P=0.895), but the recurrence rate of non-anatomical liver resection was higher than that of anatomical liver resection(P=0.035). Conclusions: In the past decade, the overall survival rate of HCC undergoing surgical treatment is significantly higher than before. For HCC patients with good liver function reservation, surgical resection can be performed first, and salvage liver transplantation can be performed after recurrence. The effect of salvage liver transplantation is comparable to that of primary liver transplantation. As for the choice of liver resection approaches, non-anatomical resection can reserve more liver tissue and can be selected as long as the negative margin is guaranteed.

[Longitudinal surveillance of schistosomiasis in hilly regions of Sichuan Province from 2015 to 2019]

OBJECTIVE

To investigate the changes in the endemic situation of schistosomiasis in national surveillance sites of Sichuan Province, so as to provide the scientific evidence for formulating the schistosomiasis elimination strategy.

METHODS

From 2015 to 2019, 63 national schistosomiasis surveillance sites were assigned in Sichuan Province, in which Schistosoma japonicum infections were monitored in humans, livestock, wild feces and snails. The monitoring data were descriptively analyzed.

RESULTS

A total of 94 119 person-time local residents were serologically screened for S. japonicum infections in 63 national surveillance sites of Sichuan Province from 2015 to 2019, with sero-prevalence rates ranging from 1.28% to 3.11%, and the sero-positives were predominantly detected in local residents at ages of over 50 years and in farmers. A total of 94 119 person-time mobile populations were serologically screened for S. japonicum infections in the national surveillance sites during the 5-year period, with sero-prevalence of 1.10% to 1.59%. There were no egg-positives identified in either local residents or mobile populations. Among the 6 126 herd-time livestock detected, no egg-positives were identified, and no S. japonicum infection was detected in the 205 wild feces. Snail survey was performed covering an area of 8 484.08 hm², and 724.80 hm² snail habitats were identified, including 2.43 hm² emerging snail habitats and 63.00 hm² re-emerging snail habitats. The mean occurrence of frames with snails was 6.87% to 19.63%, and the mean density of living snails was 0.18 to 0.62 snails/0.1 m² in the national surveillance sites of Sichuan Province from 2015 to 2019; however, no S. japonicum infection was detected in snails.

CONCLUSIONS

The endemic situation of schistosomiasis has reduced to the lowest level in Sichuan Province; however, there is a rise in snail habitats, and there is still a risk of schistosomiasis resurgence. Further improvements of the surveillance system for schistosomiasis are required to achieve the goal of schistosomiasis elimination in Sichuan Province as soon as possible.

Operando surface science methodology reveals surface effect in charge storage electrodes

Surface and interface play critical roles in energy storage devices, calling for operando characterization techniques to probe the electrified surfaces/interfaces. In this work, surface science methodology, including electron spectroscopy and scanning probe microscopy, has been successfully applied to visualize electrochemical processes at operating electrode surfaces in an Al/graphite model battery. Intercalation of anions together with cations is directly observed in the surface region of a graphite electrode with tens of nanometers thickness, the concentration of which is one order higher than that in bulk. An intercalation pseudocapacitance mechanism and a double specific capacity in the electrode surface region are expected based on the super-dense intercalants and anion/cation co-intercalation, which are in sharp contrast to the battery-like mechanism in the electrode bulk. The distinct electrochemical mechanism at the electrode surface is verified by performance tests of real battery devices, showing that a surface-dominant, nanometer-thick graphite cathode outperforms a bulk-dominant, micrometer-thick graphite cathode. Our findings highlight the important surface effect of working electrodes in charge storage systems.

Unraveling the Nature of Excellent Potassium Storage in Small-Molecule Se@Peapod-Like N-Doped Carbon Nanofibers

The potassium-selenium (K-Se) battery is considered as an alternative solution for stationary energy storage because of abundant resource of K. However, the detailed mechanism of the energy storage process is yet to be unraveled. Herein, the findings in probing the working mechanism of the K-ion storage in Se cathode are reported using both experimental and computational approaches. A flexible K-Se battery is prepared by employing the small-molecule Se embedded in freestanding N -doped porous carbon nanofibers thin film (Se@NPCFs) as cathode. The reaction mechanisms are elucidated by identifying the existence of short-chain molecular Se encapsulated inside the microporous host, which transforms to K₂ Se by a two-step conversion reaction via an "all-solid-state" electrochemical process in the carbonate electrolyte system. Through the whole reaction, the generation of polyselenides (K₂ Se_n , 3 ≤ n ≤ 8) is effectively suppressed by electrochemical reaction dominated by Se₂ molecules, thus significantly enhancing the utilization of Se and effecting the voltage platform of the K-Se battery. This work offers a practical pathway to optimize the K-Se battery performance through structure engineering and manipulation of selenium chemistry for the formation of selective species and reveal its internal reaction mechanism in the carbonate electrolyte.