Ultrahigh Volumetric Energy Density Research Articles

Surface engineered covalent bridging strategy to in-situ fabricate MXene-based core-sheath fiber for flexible supercapacitors with ultrahigh volumetric energy density and mechanical properties

MXene fiber-based supercapacitors (SCs) are expected to make a major contribution to the ongoing development of wearable electronics and metaverse technologies in future. However, to fabricate fiber electrodes with high energy density and strong mechanical properties remains a major challenge for their usage in SCs. Herein, we fabricated a flexible core-sheath structural Ti3C2Tx MXene@polyaniline (MX@PA) fiber electrode with ultrahigh volumetric energy density and good tensile strength through surface engineered covalent bridging strategy via wet spinning and in situ oxidant-freepolymerization processes. Benefiting from the high-order core-sheath structure and strong Ti-O-N covalent bonds between MXene and PANI, an ultrahigh tensile strength (∼168.1 MPa) and super-toughed (∼1.75 MJ cm−3) fiber electrode was achieved. The assembled SC provided much higher volumetric capacitance of 631F cm−3 (based on the SC device) at a current density of 0.5 A cm−3 and ultralong-term cycling stability with 92.6 % capacitance retention after 10000 cycles due to the rapid electron conduction of core (MXene) and large pseudocapacitive charge transfer of the sheath (PANI). As a result, the SC delivers excellent volumetric energy density of 56.1 mWh cm−3 at a power density of 204.9 mW cm−3. The integrated SC found actual application to power a 2.5 V red LED.

Ultrathin, large area β-Ni(OH)2 crystalline nanosheet as bifunctional electrode material for charge storage and oxygen evolution reaction

Bifunctional electrode materials are highly desirable for meeting increasing global energy demands and mitigating environmental impact. However, improving the atom-efficiency, scalability, and cost-effectiveness of storage systems, as well as optimizing conversion processes to enhance overall energy utilization and sustainability, remains a significant challenge for their application. Herein, we devised an optimized, facile, economic, and scalable synthesis of large area (cm2), ultrathin (∼2.9 ± 0.3 nm) electroactive nanosheet of β-Ni(OH)2, which acted as bifunctional electrode material for charge storage and oxygen evolution reaction (OER). The β-Ni(OH)2 nanosheet electrode shows the volumetric capacity of 2.82 Ah.cm−3(0.82 µAh.cm−2) at the current density of 0.2 mA.cm−2. The device shows a high capacity of 820 mAh.cm−3 with an ultrahigh volumetric energy density of 0.33 Wh.cm−3 at 275.86 W.cm−3 along with promising stability (30,000 cycles). Furthermore, the OER activity of ultrathin β-Ni(OH)2 exhibits an overpotential (η10) of 308 mV and a Tafel value of 42 mV dec-1 suggesting fast reaction kinetics. The mechanistic studies are enlightened through density functional theory (DFT), which reveals that additional electronic states near the Fermi level enhance activity for both capacitance and OER.

Modulating oxygen vacancies in MXene/MoO3-x smart fiber by defect engineering for ultrahigh volumetric energy density supercapacitors and wearable SERS sensors

MXene fibers are expected to accelerate the sustainable development of intelligent era as multi-functional smart fibers. However, MXene fibers have serious obstacles when used for multi-functional applications. Here, we fabricated a multi-functional MXene fiber by incorporating MoO3-x nanobelts with abundant oxygen vacancies via wet spinning and defect engineering methods. Benefiting from the presence of abundant oxygen vacancies, the produced MXene/MoO3-x fibers not only provide more active sites to interact with electrolyte ions, but also substantially augment the rate capacities of fibers due to the enlarged distances between MXene flakes. Thus, the assembled fiber-based supercapacitor (SCs) realized high capacitance of 869.1F cm−3 at 0.5 A cm−3, good volumetric energy density of 77.3 mWh cm−3 at a power density of 204.8 mW cm−3 and long-term cycling stability along with 86.4 % capacity retention after 5000 cycles. Moreover, due to the narrowed bandgap of MoO3-x produced by defect engineering enhanced the charge transfer between the fiber and molecules, MXene/MoO3-x fiber also demonstrated a low limit of detection and reliable biomarkers detection in artificial sweat. These findings provide the potential application of MXene-based fibers in multi-functional devices.

Collapsed N&S dual-doped carbon nanocages as high-density anode for ultrahigh volumetric performance of Li-ion batteries

Compact lithium-ion batteries for miniaturized devices require high-volumetric-performance anodes. Either the graphite with high density or the porous nanocarbons with high gravimetric performance is limited in volumetric performance. Herein, we construct a series of anode materials, i.e. the collapsed carbon nanocages with different dopants, by capillarity compression, which achieves a high density of ∼0.97 g cm−3 but remains abundant micropores with increased active sites and enlarged interlayer distance. The N&S dual-doping redistributes the charges of sp2 carbon to an optimal status, leading to the high Li-ion capacity, meanwhile facilitates the wettability at the electrode/electrolyte interface, leading to the enhanced Li-ion diffusion coefficient. Accordingly, the collapsed N&S dual-doped carbon nanocages (cNSCNC) anode exhibits a record-high volumetric capacity of 1578 mAh cm−3 at 0.1 A g−1, excellent rate capability and cycling stability, thus achieving an ultrahigh volumetric energy density of 1087 Wh L−1 at 120 W L−1 for the cNSCNC//LiFePO4 full cell.

Edge-rich reduced microcrystalline graphite oxide for Li-ion hybrid capacitors with ultrahigh volumetric energy density

Compact and high-performance carbon cathode materials are vital to improve the gravimetric and volumetric energy/power density of advanced energy storage devices such as lithium-ion hybrid capacitors (LIHCs). Graphite has a high mass density and the areal specific capacitance at the edge plane is far larger than that in the basal plane. Hence, increasing the proportion of edges can effectively improve the specific capacitance of the carbon material. However, it is challenging to expose more edges of graphite due to its high thermal and chemical stability. In this work, a compact cathode is prepared through a facile high-temperature ammonia treatment of microcrystalline graphite oxide (MGO). The obtained edge-rich reduced microcrystalline graphite oxide (ER-RMGO) demonstrates abundant edge sites, a high mass density of 1.48 g cm−3 and an extremely high areal specific capacitance of up to 319.3 μF cm−2. As a result, the fabricated Li-ion hybrid capacitor delivers an ultrahigh volumetric energy density of 392 Wh L−1 and power density of 9.49 W LkW L−1. This work sheds light on the great potential of microcrystalline graphite derived edge-rich carbon materials for compact capacitive energy storage.

High Energy Density Solid‐State Lithium Metal Batteries Enabled by In Situ Polymerized Integrated Ultrathin Solid Electrolyte/Cathode

AbstractSolid‐state batteries (SSBs) are regarded as the most promising next‐generation energy storage devices due to their potential to achieve higher safety performance and energy density. However, the troubles in the preparation of ultrathin solid‐state electrolytes (SEs) as well as the resultant compromise in mechanical strength greatly limit the safety application of SSBs. Herein, a novel in situ polymerized integrated ultrathin SE/cathode design is developed. The ultrathin ceramic layer supported on the cathode serves not only as a rigid scaffold to prevent direct contact between the cathode and anode but also as active inorganic fillers to enhance the mechanical properties of in situ polymerized SE film. The unique Li‐ion coordination environments as well as the Li hopping mechanism profoundly promote fast ion transport in composite SEs. The in situ polymerized SEs simultaneously achieve the balance in ultrathin thickness (10 µm), fast ion transport (0.65 mS cm−1), superior Young's modulus (66.8 GPa), and excellent interface contact. The pouch cells with practical Li||LiNi0.8Co0.1Mn0.1O2 configuration achieve an ultrahigh volumetric energy density of 1018 Wh L−1 and safety performance. The in situ polymerized integrated ultrathin SE/cathode design exhibits great promise for the practical application of SSBs with high energy density and safety performance.

Mechanochemically Assisted Microwave-Induced Plasma Synthesis of a N-Doped Graphitic Porous Carbon-Based Aqueous Symmetric Supercapacitor with Ultrahigh Volumetric Capacitance and Energy Density

Mechanochemically Assisted Microwave-Induced Plasma Synthesis of a N-Doped Graphitic Porous Carbon-Based Aqueous Symmetric Supercapacitor with Ultrahigh Volumetric Capacitance and Energy Density

Constructing a Hierarchical Ternary Hybrid of PEDOT:PSS/rGO/MoS2 as an Efficient Electrode for a Flexible Fiber-Shaped Supercapacitor

Improving the specific capacitance and energy density of a fiber-shaped supercapacitor (FSSC) is critical to its applications as an energy storage device for advanced smart wearable electronics. In this paper, a heterogeneous poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate)/reduced graphene oxide/molybdenum disulfide (PEDOT:PSS/rGO/MoS2) fiber was prepared to achieve a high-performance and durable electrode for the FSSC. As indicated, pseudocapacitive MoS2 was in situ grown on a highly conductive acid-treated PEDOT:PSS/rGO assembly with a hierarchical structure. This structural design emphasizes the wrinkled morphology and high conductivity of the PEDOT:PSS/rGO backbone to maximize the MoS2 deposition and accelerate its electron transfer, which fully utilizes the pseudocapacitance of MoS2 and provides additional capacitance contribution to the obtained device. Attributed to the synergy, the prepared fiber electrode in the FSSC exhibits high volumetric/areal specific capacitance (325.8 F cm–3/405.3 mF cm–2 at 1 A cm–3 or 1.2 mA cm–2) and excellent rate performance (82%, 1–10 A cm–3). The corresponding device shows an ultrahigh volumetric energy density of 6.9 mW h cm–3 at a high power density of 173.6 mW cm–3 and an areal energy density of 8.5 μW h cm–2 at 215.9 μW cm–2, together with excellent cycle stability and mechanical flexibility, outperforming most of the previously reported FSSCs. Accordingly, the proposed strategy provides a great opportunity to develop a high-performance FSSC for further wearable electronics.

Laser-Induced Transient Self-Organization of TiNx Nano-Filament Percolated Networks for High Performance Surface-Mountable Filter Capacitors.

Filter capacitors (FCs) are substantial for digital circuits and microelectronic devices, and thus more compact FCs are eternally demanded for system miniaturization. Even though microsupercapacitors are broadly regarded as an excellent candidate for future FCs, yet due to the limitation of available electrode materials, the capacitive performance of reported MSCs drops sharply under high-frequency alternating current. Herein, wepresent a unique laser-induced transient self-organization strategy, which synergizes pulsed laser energy and multi-physical field controlled coalescence processes, leading to the rapid and controllable preparation of titanium nitride ultrafine nano-filaments (diameter ≈3-5 nm) networks. Their chaotic fractal nanoporous structure, superior specific surface area, and excellent conductivity render these nanostructures promising candidates for FCs. Surface-mounted filter capacitors based on this electrode material exhibit ultra-long cycle-life (2 000 000 cycles) with record ultrahigh volumetric energy density of 9.17 mWh cm-3 at 120 Hz in aqueous electrolyte, displaying advantages in function, size, and integrability compared with the state-of-the-art aluminum electrolytic capacitors. The method here provides a versatile toolbox for designing novel nanostructures with intriguing characteristics and insights for developing advanced and miniaturized filter and power devices.

Se with Se-C bonds encapsulated in a honeycomb 3D porous carbon as an excellent performance cathode for Li-Se batteries

Li-Se batteries have risen to prominence as promising lithium-ion batteries thanks to their ultrahigh volumetric energy density and the high electrical conductivity of Se. However, the use of Li-Se batteries is limited not only by the large volume expansion and dissolution of polyselenides in the cathodes during cycling, but also the low selenium loading. A highly effective and currently feasible approach to simultaneously tackle these problems is to position the selenium in a carbon matrix with a sufficient pore volume to accommodate the expansion while increasing the interfacial interaction between the selenium and carbon. We have synthesized a novel cathode material (Se@HPC) for Li-Se batteries of a honeycomb 3D porous carbon derived from a tartrate salt, that was impregnated with Se to produce Se-C bonds. The pore volume of the honeycomb 3D porous carbon was as high as 1.794 cm3 g−1, which allowed 65 wt% selenium to be uniformly encapsulated. Moreover, the strong chemical bonds between selenium and carbon stabilize the selenium, thus inhibiting its huge volume expansion and the dissolution of polyselenides, and promoting charge transfer during cycling. As expected, a Se@HCP cathode has excellent cyclability and a good rate performance. After 200 cycles at 0.2 C, its specific capacity remains at 561 mA h g−1, 83% of the theoretical value, and decays by only 0.058% per cycle. It also has a large capacity of 472.8 mA h g−1 under a high current density of 5 C.

A Highly integrated flexible photo-rechargeable system based on stable ultrahigh-rate quasi-solid-state zinc-ion micro-batteries and perovskite solar cells

Miniaturized flexible photo-rechargeable systems show bright prospects for wide applications in internet of things, self-powered health monitoring and emergency electronics. However, conventional systems still suffer from complex manufacturing processes, slow photo-charging and discharging rate, and mismatch between photovoltaic and energy storage components in size, mechanics and voltage, etc. Here, we demonstrate a facile inkjet printing and electrodeposition approach for fabricating a highly integrated flexible photo-rechargeable system by combining stable and ultra-high-rate quasi-solid-state Zn-MnO 2 micro-batteries (ZMBs) with flexible perovskite solar cells (FPSCs). In particular, Ni protective layer is first introduced into ZMBs to stabilize battery configuration and facilitate enhanced electrochemical performance. The optimized ZMB exhibits ultrahigh volumetric energy density of 148 mWh cm −3 (16.3 μWh cm −2 ) and power density of 55 W cm −3 (6.1 mW cm −2 ) at the current density of 400 C (5 mA cm −2 ), enabling them comparable with the state-of-the-art micro-batteries or supercapacitors fabricated by conventional methods. The embedded FPSCs show excellent photovoltaic performance, sufficient to charge ZMBs and create a self-charging system capable to offer energy autonomy in miniaturized wearable electronics. The integrated systems can achieve an ultrafast photo-charging within 30 s, with sufficient energy to power other functional electronics (e.g., LED bulb and pressure sensor) for tens of minutes. This prototype offers a promising scheme for next-generation miniaturized flexible photo-rechargeable systems.

Tuning the electrochemical activity of Li–Se batteries by redox mediator additives

A lithium–selenium (Li–Se) battery is considered as a promising next-generation energy storage system due to its ultrahigh volumetric energy density. However, the capacity attenuation due to the dissolution and shuttle effect of polyselenides is urgent to be addressed. Herein, 1,4-benzenedithiol (1,4-BDT) and benzeneselenol (PhSeH) are proposed as redox mediator additives in the electrolyte. They both change the multi-step reaction of Se and accelerate the redox kinetics, thus suppressing the shuttle effect of polyselenides and improving the cycling stability and rate performance. The Li–Se cell with 1,4-BDT exhibits steady 450 cycles at 1 C with capacity decay only 0.058% per cycle. Differently, the Li–Se cell with PhSeH features fast kinetics, which shows 91.4% capacity retention after 450 cycles at a high rate of 5 C. Due to the difference of molecular structures between 1,4-BDT and PhSeH, the cyclic oligomers formed in the Li–Se cell with 1,4-BDT diminish the solubility of polyselenides enhancing the cycling stability, while the chain-like diphenyl selenides generated in the Li–Se cell with PhSeH promote kinetics performance through a single-phase reaction. This work provides an effective redox regulation strategy that will stimulate interest in exploration of organic mediators for rechargeable batteries.

Compacted N-Doped 3D Bicontinuous Nanoporous Graphene/Carbon Nanotubes@Ni-Doped MnO2 Electrode for Ultrahigh Volumetric Performance All-Solid-State Supercapacitors at Wide Temperature Range.

Developing wide temperature range flexible solid-state supercapacitors with high volumetric energy density is highly desirable to meet the demands of the rapidly developing field of miniature consumer electronic devices and promote their widespread adoption. Herein, high-quality dense N-doped 3D porous graphene/carbon nanotube (N-3DG/CNTs) hybrid films are prepared and used as the substrate for the growth of Ni-doped MnO2 (Ni-MnO2 ). The integrated and interconnected architecture endows N-3DG/CNTs@Ni-MnO2 composite electrodes' high conductivity and fast ion/electron transport pathway. Subsequently, 2.4V solid-state supercapacitors are fabricated based on compacted N-3DG/CNTs@Ni-MnO2 positive electrodes, which exhibit an ultrahigh volumetric energy density of 78.88mWhcm-3 based on the entire device including electrodes, solid-state electrolyte, and packing films, excellent cycling stability up to 10 000 cycles, and a wide operating temperature range from -20 to 70°C. This work demonstrates a design of flexible solid-state supercapacitors with exceptional volumetric performance capable of operation under extreme conditions.

Chemical reduction-induced fabrication of graphene hybrid fibers for energy-dense wire-shaped supercapacitors

The emerging one-dimensional wire-shaped supercapacitors (SCs) with structural advantages of low mass/volume structural advantages hold great interests in wearable electronic engineering. Although graphene fiber (GF) has full of vigor and tremendous potentiality as promising linear electrode for wire-shaped SCs, simultaneously achieving its facile fabrication process and satisfactory electrochemical performance still remains challenging to date. Herein, two novel types of graphene hybrid fibers, namely ferroferric oxide dots (FODs)@GF and N-doped carbon polyhedrons (NCPs)@GF, have been proposed via a simple and efficient chemical reduction-induced fabrication. Synergistically coupling the electroactive units (FODs and NCPs) with conductive graphene nanosheets endows the fiber-shaped architecture with boosted electrochemical activity, high flexibility and structural integrity. The resultant [email protected] and [email protected] hybrid fibers as linear electrodes both exhibit excellent electrochemical behaviors, including large volumetric specific capacitance, good rate capability, as well as favorable electrochemical kinetics in ionic liquid electrolyte. Based on such two linear electrodes and ionogel electrolyte, a high-performance wire-shaped SC is effectively assembled with ultrahigh volumetric energy density (26.9 mW·h·cm−3), volumetric power density (4900 mW·cm−3) and strong durability over 10,000 cycles under straight/bending states. Furthermore, the assembled wire-shaped SC with excellent flexibility and weavability acts as efficient energy storage device for the application in wearable electronics.

2.4 V ultrahigh-voltage aqueous MXene-based asymmetric micro-supercapacitors with high volumetric energy density toward a self-sufficient integrated microsystem

Two-dimensional MXenes are key high-capacitance electrode materials for micro-supercapacitors (MSCs) catering to integrated microsystems. However, the narrow electrochemical voltage windows of conventional aqueous electrolytes (≤ 1.23 V) and symmetric MXene MSCs (typically ≤ 0.6 V) substantially limit their output voltage and energy density. Highly concentrated aqueous electrolytes exhibit lower water molecule activity, which inhibits water splitting and consequently widens the operating voltage window. Herein, we report ultrahigh-voltage aqueous planar asymmetric MSCs (AMSCs) based on a highly concentrated LiCl-gel quasi-solid-state electrolyte with MXene (Ti3C2Tx) as the negative electrode and MnO2 nanosheets as the positive electrode (MXene//MnO2-AMSCs). The MXene//MnO2-AMSCs exhibit a high voltage of up to 2.4 V, attaining an ultrahigh volumetric energy density of 53 mWh cm−3. Furthermore, the in-plane geometry and the quasi-solid-state electrolyte enabled excellent mechanical flexibility and performance uniformity in the serially/parallel connected packs of our AMSCs. Notably, the MXene//MnO2-AMSC-based integrated microsystem, in conjunction with solar cells and consumer electronics, could efficiently realize simultaneous energy harvesting, storage, and conversion. The findings of this study provide insights for constructing high-voltage aqueous MXene-based AMSCs as safe and self-sufficient micropower sources in smart integrated microsystems.

Novel Insight into the Concept of Favorable Combination of Electrodes in High Voltage Supercapacitors: Toward Ultrahigh Volumetric Energy Density and Outstanding Rate Capability (Global Challenges 4/2022)

In article 2100139, Mani Karthik and co-workers show that the design and construction of a new configuration using different carbon materials as supercapacitor electrodes can increase the volumetric energy density of supercapacitor devices for automobile and other high voltage applications.

Ti3C2Tx MXene-Based Micro-Supercapacitors with Ultrahigh Volumetric Energy Density for All-in-One Si-Electronics

MXene-based microsupercapacitors (MSCs) have promoted the development of on-chip energy storage for miniaturized and portable electronics due to the small size, high power density and integration density. However, restricted energy density and operating voltage invariably create obstacles to the practical application of MSCs. Here, we report a symmetric MXene-based on-chip MSC, achieving an ultrahigh energy density of 75 mWh cm-3 with high operating voltage of 1.2 V, which are almost the highest values among all reported symmetric MXene MSCs. The adjustment strategy of acetone on the viscosity and surface tension of MXene ink, along with the natural sedimentation strategy, can effectively prevent the orderly stacking of MXene sheets. Further, we developed an all-in-one Si-electronics with three series MSCs through laser-etching technology, obviously presenting high integration capacity and processing compatibility. Thus, this work will contribute to the development of high integration all-in-one electronics with high energy density MXene-based MSCs.

Novel Insight into the Concept of Favorable Combination of Electrodes in High Voltage Supercapacitors: Toward Ultrahigh Volumetric Energy Density and Outstanding Rate Capability.

Most of the biomass‐derived carbon‐based supercapacitors using organic electrolytes exhibit very low energy density due to their low operating potential range between 2.7 and 3.0 V. A novel insight into the concept of the different porous architecture of electrode materials that is employed to extend a device's operating potential up to 3.4 V using TEABF4 in acetonitrile, is reported. The combination of two high surface area activated carbons derived from abundant natural resources such as industrial waste cotton and wheat flour as sustainable and green carbon precursors is explored as an economical and efficient supercapacitor carbon electrode. Benefitting from the simultaneous achievement of the higher potential window (3.4 V) with higher volumetric capacitance (101 F cm–3), the supercapacitor electrodes exhibit higher volumetric energy density (42.85 Wh L–1). Bimodal pore size distribution of carbon with a tuned pore size and high specific surface area of the electrode can promote the fast transport of cations and anions. Hence, it exhibits a high rate capability even at 30 A g–1. In addition, the electrodes remain stable during operation cell voltage at 3.4 V upon 15 000 charging–discharging cycles with 90% capacitance retention.

Single crystal Ni-rich NMC cathode materials for lithium-ion batteries with ultra-high volumetric energy density

Ultra-high tap density of single crystal Ni-rich NMC cathode materials with the spherical-like particles coupled with high discharge capacity result in up to 40% enhancement in volumetric energy density.

Novel CoZnNi oxyphosphide-based electrode with high hydroxyl ion adsorption capacity for ultra-high volumetric energy density asymmetric supercapacitor

Achieving a high volumetric energy density supercapacitor is of great significance for portable energy storage devices while still a major challenge. Herein, we design and fabricate self-supporting electrodes using CoZnNi oxyphosphide nanoarrays sandwiched graphene/carbon nanotube (CZNP/GC) film with highly exposed active sites. Benefitting from the modified electronic structures, high accessible surface areas, and the integrated structure, the well-designed CZNP/GC electrode exhibits an ultra-high volumetric capacitance of 2096.4 F cm−3 at a current density of 1 A g−1. Moreover, a high-performance negative electrode of carbon/rGO/CNTs (C/GC) is also fabricated using the same CoZn-metal-organic frameworks precursor. The assembled asymmetric supercapacitor CZNP/GC//C/GC displays an ultra-high volumetric energy density of 71.8 W h L−1 at 960 W L−1. After 6000 charge-discharge cycles, the device still maintains 85.6% of the original capacitance. The density functional theory calculation is studied and the negative adsorption energy proves that the OH– adsoption process onto the surface of as-prepared electrode is thermodynamically favorable, facilitating the electrochemical reaction. This work provides a new option in constructing tailorable electrodes with a well-defined hierarchical structure for supercapacitor and beyond.