Poor Energy Density Research Articles

High energy storage performance MnSe2 cathode by one-step deposition strategy in aqueous zinc-ion batteries

The directly synthesized MnO2 using ambient temperature aqueous solution deposition strategy has great application prospects as the cathode material for aqueous zinc-ion batteries, which strategy has the advantages of simple process, large-scale and reproducible production. However, the single MnO2 suffers many problems, such as poor practical energy density and serious capacity fading. In order to improve the capacity and cycling stability of the cathode, we designed to use the method of ambient temperature aqueous solution deposition strategy. Using this method and adding a reducing agent and selenide to the original raw materials for the preparation of MnO2, the crystalline state of MnSe2 materials was finally synthesized creatively. This in situ one-step deposition method for the synthesis of MnSe2 is a very simple process and can be prepared on a large scale in a short period of time, saving time and effort. Compared with the MnO2 cathode materials, the MnSe2 cathode can reach the high capacity of 452.4 mAh g−1 at a low current density of 0.1 A g−1, an excellent rate capability of 242.7 mAh g−1 at 2.0 A g−1. After 2000 cycles (2 A g−1) of charging and discharging, the Zn/MnSe2 battery can maintain a specific capacity of over 231.5 mAh g−1 and a superior cycling retention of 86.3%, with a coulombic efficiency remains above 98%. This work provides a new way to develop simple, high-capacity and long-life aqueous zinc-ion batteries.

Unique hierarchical porous carbon nanosheet network for supercapacitors: Ultra-long cycling stability and enhanced electroactivity of oxygen at high temperature

Porous carbon-based supercapacitors (SCs) are promising electrochemical energy storage devices. However, the unreasonable design of porous carbon leads to poor energy density and unsatisfactory high-temperature cycling stability of SCs. Herein, we synthesize a hierarchical porous carbon nanosheet network by combining self-templated pyrolysis and KOH activation strategies. This carbon nanosheet network exhibits an extremely large active ion-accessible pore volume (V0.76–6 nm=1.654 m3 g−1) and a considerable supermesopore volume (V6–50nm 0.413 m3 g−1), which provide abundant active sites and fast diffusion channels for electrolyte ions, respectively. Futhermore, the enhanced electroactivity of oxygen at high temperature is demonstrated, which provides additional active sites. Inspiringly, the as-constructed EMIMBF4-based SCs can be well serviced at the high temperature of 80 °C with ultra-high energy/power density of 122.23 Wh kg−1/40.6 kW kg−1 and superior durability (81.1% retention after 8000 cycles at 20 A g−1). This work provides insights into the effect of temperature on the electroactivity of oxygen, as well as the construction of porous carbon-based high-temperature SCs with desired performance metrics.

Anion‐Trap Engineering toward Remarkable Crystallographic Reorientation and Efficient Cation Migration of Zn Ion Batteries

AbstractZn batteries are considered as potential candidates in future power sources, however suffer problems of rampant dendrite/by‐product on Zn anodes, torpid Zn2+ transfer/diffusion and poor energy density. Inspired by the host‐guest interaction chemistry, an anion‐trap agent β‐cyclodextrin (β‐CD) is introduced into the Zn(ClO4)2 electrolyte to induce dominant Zn (002) deposition and improve Zn2+ migration behaviors. The anion ClO4− is revealed to be trapped inside the cavity of β‐CD, impairing barriers for Zn2+ migration and significantly elevating the Zn2+ transference number to 0.878. Meanwhile, the β‐CD@ClO4− complex shows the function in preferential growth of the Zn (002), blocking the approach of dendrite growth. Above combined functions lead to substantial enhancement in long‐term stability and cell capacity, as proved by 10 times longer life of Zn||Zn symmetric cells and 57 % capacity increasement of Zn‐MnO2 full cells (at 0.1 A g−1) compared with that of pure Zn(ClO4)2 electrolyte.

Anion-Trap Engineering toward Remarkable Crystallographic Reorientation and Efficient Cation Migration of Zn Ion Batteries.

Zn batteries are considered as potential candidates in future power sources, however suffer problems of rampant dendrite/by-product on Zn anodes, torpid Zn2+ transfer/diffusion and poor energy density. Inspired by the host-guest interaction chemistry, an anion-trap agent β-cyclodextrin (β-CD) is introduced into the Zn(ClO4 )2 electrolyte to induce dominant Zn (002) deposition and improve Zn2+ migration behaviors. The anion ClO4 - is revealed to be trapped inside the cavity of β-CD, impairing barriers for Zn2+ migration and significantly elevating the Zn2+ transference number to 0.878. Meanwhile, the β-CD@ClO4 - complex shows the function in preferential growth of the Zn (002), blocking the approach of dendrite growth. Above combined functions lead to substantial enhancement in long-term stability and cell capacity, as proved by 10 times longer life of Zn||Zn symmetric cells and 57 % capacity increasement of Zn-MnO2 full cells (at 0.1 A g-1 ) compared with that of pure Zn(ClO4 )2 electrolyte.

3D Prussian blue decorated porous carbon composite electrode for advanced asymmetric supercapacitor applications

Irrational use of fossil fuels led to global warming and pollution. Therefore, the newer technologies should be sustainable and eco-friendly to combat climate change. In this context, supercapacitors (SCs) are demonstrated with carbon materials derived from natural biomaterials. The utilization of biomass-derived materials in energy storage not only converts biowaste material to value-added products but also reduces the production cost. Although SCs exhibit high power density, they are not considered a primary energy source due to their poor energy density. By taking advantage of the present work's asymmetric configuration, the operating voltage window and energy density of aqueous SCs are significantly enhanced. An asymmetric SC is developed by combining a porous 3D cubical-shaped Prussian blue (PB) decorated carbon derived from tamarind seeds (ACTS-800) (PB/ACTS-800) positive electrode with ACTS-800 negative electrode and aqueous 3 M KNO3 electrolyte. The resulting ACTS-800//PB/ACTS-800 (1:2) asymmetric SC demonstrated a broad electrochemical stable voltage window of 2.2 V in the aqueous medium. Impressively, a high energy density of 60 Wh/kg @ 551 W/kg realized is much superior to most of the carbon/carbon SCs operated in an aqueous medium.

Three-dimensional micro/nano-interconnected scaffold graphene-based micro-supercapacitors with high electrochemical performance

Micro-supercapacitors (MSCs) have emerged as one of the most promising power supply candidates to meet the ever-increasing requirement for various miniaturization application scenarios due to the merits of high power density, long life span, superior rate capabilities and ease of maintenance and integration. However, wide applications of MSCs were greatly hindered due to the poor energy density. In this regard, designing and constructing three-dimensional (3D) architecture electrodes have been considered an effective strategy to improve the energy density of MSCs, which secures enhanced electrochemical active sites and facilitates ions kinetics for efficient charge storage capability. Herein, high-performing MSCs have been achieved with a graphene-based electrode of a rational 3D micro/nano-interconnected scaffold, in which the robust 3D architecture can be effectively regulated by controlling the amount of carbon nanotubes (CNTs). Electrochemical mechanism and theoretical simulation results reveal that enhanced electrolyte ion accessible sites and facilitated ion kinetics can be ensured since the homogeneous electric streamlines distribution in the 3D micro/nano-interconnected scaffold. As expected, the resultant MSCs possess an outstanding electrochemical performance with an areal capacitance as high as 53.49 mF cm−2 under the pack of gel-based electrolytes, delivering a power density of 25 mW cm−2 and an energy density of 8.82 μWh cm−2. Moreover, the MSCs show superior long-term stability with 99% retention after 20 000 cycles, which is beyond most reported 3D graphene-based MSCs. The 3D micro/nano-interconnected scaffold electrodes might provide a method to enhance the electrochemical performance of micro-scale power sources for the applications of micro-devices.

(Digital Presentation) Electrochemical Measurements of Solvent Co-Intercalation Phenomenon Enabling Sodium-Ion Electrolyte Optimization for Graphite Anodes

Sodium-ion batteries (SIBs) is one of the more promising battery technologies that are starting to see commercialisation, were the low cost, abundance of necessary raw materials, higher safety and power and similar energy densities compared to lithium-ion batteries (LIBs) are often mentioned as their key advantages. SIBs, due to their great similarities with LIBs have seen a rapid development. One of the key differences, however, is the carbonaceous negative electrode, where SIBs, due to Na+ not forming stable intercalation compounds with graphite, the anode of choice for LIBs, are forces to use hard carbons. But, it was recently discovered by Jache et al. 1 that Na+ can form stable ternary graphite intercalation compounds through a solvent co-intercalation mechanism, thus enabling the use of graphite in SIBs. This sparked several follow-up studies exploring solvent co-intercalation as a way to use graphite in SIBs2, but the question of how many solvent molecules are intercalated along with the cation, and thus the stoichiometry of the redox reaction, was never settled. Here, we present a novel electrochemical method to directly measure the number of solvents that are brought along by the cation into the graphite host structure.The SIBs using the co-intercalation mechanism to enable the use of graphite has so far shown great kinetics, power densities and extreme cyclability, with great capacity retention over thousands of cycles2. They are, however, plagued by a low specific capacity, a great volume expansion, and high average voltage in half-cells vs. Na+/Na, leading to poor energy density. But, the knowledge of how many glymes entering the graphite host gained from our measurements enabled us to rationally design new electrolytes, composed of low amounts of glymes mixed with another co-solvent, that both increases the energy density of the system, by lowering the average voltage while retaining the capacity, and reduces the volume expansion, while also reducing the cost of the electrolyte (Figure 1). The impact of the new electrolytes on the structure of graphite is studies using operando dilatometry and XRD, while the local structure in the electrolyte is investigated with ab initio methods – together giving a comprehensive view of the system. Figure 1. Voltage profile of new electrolytes, showing a lowering of the average voltage a second plateau, and snap shot from ab initio molecular dynamics.

High energy storage density and efficiency in (Bi0.5Na0.5)0.94Ba0.06TiO3-based ceramics with broadened and flattened dielectric peaks

Currently, Bi0.5Na0.5TiO3-based lead-free ferroelectrics have attracted considerable attention as one of the promising candidates for dielectric materials due to their large spontaneous polarization, environmental friendliness and low cost. However, their poor energy density hinder the practical application of the materials. Herein, a novel ceramic of (1-x) (0.94Bi0.5Na0.5TiO3-0.06BaTiO3)-x(0.96NaNbO3-0.04CaSnO3) (BNBT-xNNCS) has been developed by the solid solution of antiferroelectric NaNbO3–CaSnO3 into ferroelectric Bi0.5Na0.5TiO3–BaTiO3 and the microstructure and electrical properties of the material have been systematically investigated. All the ceramics are lied within the coexistence zone of tetragonal (T) and rhombohedral (R) phases, ensuring to the large polarizations of the materials. Importantly, the introduction of NaNbO3–CaSnO3 shifts dielectric peaks at Ts towards room temperature and simultaneously broadens and flattens the dielectric peaks, destroying the ferroelectric long-range order of ferroelectric domains and inducing the generation of polar nanoregions (PNRs) to reduce the remanent polarization. As a result, the prominent energy storage properties with the charge energy storage density (Wtot) of 1.86 J/cm3, recoverable energy density (Wrec) of 1.64 J/cm3 and energy storage efficiency (η) of 88.23% are obtained in the BNBT-xNNCS ceramics with x = 0.20 (BNBT-20NNCS) under a comparatively low electric field strength of 149 kV/cm, accompanying with superior frequency (ΔWrec ≤ 3%, Δη ≤ 3%, 30–90 Hz) and thermal stability (ΔWrec ≤ 10%, Δη ≤ 10%, 25–175 °C).

Increasing Electric Bicycle Performance using Lithium Ferro Phospate Batteries with a Battery Management System

The depletion of fossil fuel sources and the increasing environmental pollution caused by the burning of motor vehicle fuels are major problems worldwide that need to be solved. One of the promising solutions to overcome energy security and environmental pollution is the use of electric vehicles. E-bikes are one of the most popular electric vehicles because of their many benefits. A valve-regulated lead acid battery (VRLA) is now the most common energy source for electric vehicles. It is heavy and unsafe for the user due to its poor energy density. Lithium ion batteries may be a feasible solution. One type of Li-ion battery that is environmentally friendly is lithium ferro phosphate (LFP). The potential that exists encourages researchers to conduct research and compare the performance of VRLA batteries with LFP batteries. The data retrieval method is carried out using the Arduino data logger application and is equipped with a microcontroller to read current and voltage. The test results prove that the LFP battery has good voltage stability. The distance that can be traveled is quite long, which is up to 50.16 km, because it is supported by a large capacity. On the other hand, VRLA can only travel 37.83 kilometers. Furthermore, the energy density of LFP batteries is great. The VRLA battery has a low energy density of 38.7 Wh/kg, whereas the LFP battery has a higher energy density of 117 Wh/kg, making it lighter and safer for users.

Multifunctional quasi-solid-state zinc-ion hybrid supercapacitors beyond state-of-the-art structural energy storage

Structural energy storage devices offer both electrochemical and mechanical performance in a single multifunctional platform, making them promising for weight- and/or volume-restricted applications such as electric vehicles, aircraft, and satellites. However, the development of state-of-the-art multifunctional energy storage is predominately hindered by poor energy density. Other parameters that influence the mechanical and electrochemical properties are also neglected, such as temperature, safety, etc. Herein, we assembled the first freeze-resistant, multifunctional quasi-solid-state zinc-ion hybrid supercapacitor (ZIHSC) using mechanically-strong hot-drawn, highly-porous nitrogen-doped carbon nanofibers as the load-bearing cathode and zinc foil as a paintable, malleable, low cost, highly safe, and robust anode. Considering the novel “two-birds-one-stone” strategy, the as-prepared multifunctional ZIHSCs outperform state-of-the-art structural energy storage devices in terms of a combination of energy storage and load-bearing capability. The structural ZIHSCs offer a battery-level gravimetric energy density of 113.1 Wh/kg, areal energy density of 300.0 μWh/cm2, strength of 308 MPa, Young's modulus of 14.40 GPa, toughness of 1.82 MJ/m3, and cycling stability over 7500 cycles. In addition, multifunctional ZIHSCs offer outstanding electrochemical and mechanical performance under a wide range of temperatures from cryogenic (−25 °C) to ambient (+25 °C) conditions.

Progress and Trends in Nonaqueous Rechargeable Aluminum Batteries

AbstractIt is important to research new energy storage technology for substituting the deficiencies of current energy storage devices, i.e., the poor energy density of lead‐acid batteries, the high cost of lithium‐ion batteries, etc. Rechargeable aluminum batteries (RABs) are regarded as one of the most promising storage devices due to the abundance of the materials required, superior security, and decent energy density of aluminum anodes. Nevertheless, there are some significant challenges, such as the developing energy density of cathodes, corrosion, and the high cost of electrolytes, which set obstacles to the industrialization of RABs. For avoiding the pitfalls of RABs research and boosting the development of RABs, the recent progress and trends in RABs covering mechanisms, components of RABs (electrodes, electrolytes, separators, and current collectors) and technology of assembly and packaging of devices are summarized and proposed.

Enhancement of discharge capacity and energy density by oxygen vacancies in nickel doped SrTiO3 as cathode for rechargeable alkaline zinc battery

Rechargeable alkaline zinc batteries (RAZBs) are promising aqueous battery due to the advantages of Zn metal as the anode. Although the Zn anode is low cost, non-toxic, and intrinsic safety, the use of metal oxide cathode suffers from poor discharge capacity and energy density in RAZBs. The preparation of Nickel doped SrTiO3 (NiSTO) as cathode has successfully improved the performance of RAZBs up to 596 mAh cm−3 (2 mA cm−2) with energy density of 68 mWh cm−3. The discharge capacity is remarkability enhanced by 54% as compared to that of pristine STO as cathode. This proven that the formation of oxygen vacancies (Vo¨) after doped with nickel play an important role. The creation of Vo¨ enable more charge storage sites and also improve the electric conductivity which facilitates the diffusion of ions/electrons. Based on the charge-transfer resistance, the electrical conductivity of NiSTO has improved 79% from the 7.8 to 1.6 Ω. This outstanding performance of NiSTO as cathode has benefited RAZBs.

Electrocatalytic and stoichiometric reactivity of 2D layered siloxene for high‐energy‐dense lithium–sulfur batteries

AbstractLithium–sulfur batteries (LSBs) have emerged as promising power sources for high‐performance devices such as electric vehicles. However, the poor energy density of LSBs owing to polysulfide shuttling and passivation has limited their further market penetration. To mitigate this challenge, two‐dimensional (2D) siloxene (2DSi), a Si‐based analog of graphene, is utilized as an additive for sulfur cathodes. The 2DSi is fabricated on a large scale by simple solvent extraction of calcium disilicide to form a thin‐layered structure of Si planes functionalized with vertically aligned hydroxyl groups in the 2DSi. The stoichiometric reaction of 2DSi with polysulfides generates a thiosulfate redox mediator, secures the intercalation pathway, and reveals Lewis acidic sites within the siloxene galleries. The 2DSi utilizes the corresponding in‐situ‐formed electrocatalyst, the 2D confinement effect of the layered structure, and the surface affinity based on Lewis acid–base interaction to improve the energy density of 2DSi‐based LSB cells. Combined with the commercial carbon‐based current collector, 2DSi‐based LSB cells achieve a volumetric energy density of 612 Wh Lcell−1 at 1 mA cm−2 with minor degradation of 0.17% per cycle, which rivals those of state‐of‐the‐art LSBs. This study presents a method for the industrial production of high‐energy‐dense LSBs.

Divulging the electrochemical hydrogen storage of ternary BNP-doped carbon derived from biomass scaled to a pouch cell supercapacitor

Activated carbon materials have been studied extensively as electrode materials for supercapacitors (SCs), but their poor capacitance and energy density have hampered their growth. We present a one-step synthesis of a ternary boron-nitrogen-phosphorous-doped carbon (BNPC) from biomass hemp fibre to determine its electrochemical hydrogen storage ability using SC applications. FESEM micrographs reveal mixed morphologies like square, diamond and cylindrical-shaped nanosheets, confirming the hetero-atom doping into the carbon skeleton. The optimized BNPC electrode delivers a half-cell specific capacitance and hydrogen-storage capacity of 520 Fg-1 (1 Ag-1) and 360 mAhg−1 (10 mVs−1), respectively. To demonstrate the practicability of the as-prepared BNPC electrode, a symmetric pouch-cell supercapacitor device was assembled which exhibits a full-cell specific capacitance of 262.56 Fg-1 at 1 Ag-1 and a specific energy of ~118 Wh kg−1 at a specific power of ~5759 Wkg-1 with an operating potential window of 1.8 V and 99.7% capacitance retention over 10,000 cycles. This excellent electrochemical performance can be ascribed to the synergetic properties of fast-electrolyte-ion diffusion due to the doping of heteroatoms into the carbon matrix, high conductivity and high specific surface area and effective microporosity of BNPC (1555.5 m2g-1). Also, the chemical stability of the BNPC materials, was investigated with density functional theory (DFT)-single point calculations, where the least molecular orbital energy gap was obtained by the BNPC, which confirms its structural stability. Thus, the prepared ternary BNP-doped carbon derived from biomass has provided a new direction to enhance the electrochemical energy storage potential.

MOF derived carbon with ultra-high specific surface area and pore volume for lithium-ion capacitor cathodes

Traditional supercapacitors have been studied extensively because of their high-power characters. However, their poor energy density severely limits its future applications. Different from the traditional supercapacitors, lithium-ion capacitors combine the high-power density of double-layer capacitors with the high energy density of lithium-ion batteries. In order to obtain the lithium-ion capacitors with such high performance, new electrode materials are inevitable. Herein, we use the metal-organic framework (MOF) technique to synthesize nano-sheets carbon-based materials with a large specific surface area and large pore volume. This new carbon-based material shows a very high specific capacity and long cycle life when being utilized in the cathode of lithium-ion capacitor. This method introduces a novel approach to the synthesis of high-specific surface activated carbon for lithium-ion capacitors.

Co2P wrapped Co3O4 grass-like nanowires for improved electrochemical performance in supercapacitors

As a new type of energy storage device, supercapacitor has gained a lot of popularity due to its superior power density than batteries. However, the poor energy density has become the impetus for the research of electrode materials with both high energy density and power density. In this paper, grass-like Co3O4@Co2P nanowires are prepared by a facile two-step method comprised of hydrothermal process and high temperature solid phase phosphating. As expect, the as-prepared sample shows an enhanced electrochemical performance. The specific capacity of Co3O4@Co2P can reach 652.1 C/g (1304.2 F/g) at a current density of 1 A/g, which is much higher than that of Co3O4 (228.5C/g). The rate capability and the cycling stability of Co3O4@Co2P are 64.3% at 10 A/g and 84% after 4000 cycles, respectively. Moreover, a hybrid supercapacitor (HSCs) has been assembled with Co3O4@Co2P as positive electrode and active carbon (AC) as negative electrodes. The maximum energy density and power density of HSC device are 31.3 Wh/kg and 8018.4 W/kg, respectively. Furthermore, the HSC device shows a cycling stability of 100% at the current density of 7 A/g after 10,000 cycles. These excellent properties show the potential applications of Co3O4@Co2P in the field of supercapacitors with high energy and power density.

Use of polyacrylonitrile-based carbon nanolayer modified Co3S4 to improve the overall performance of supercapacitors

Transition metal sulfides with high theoretical specific capacitance are widely used as electrode materials for supercapacitors, but their poor cycling stability and energy density prevent them from meeting the needs of practical applications. To solve this problem, it is urgent to design an electrode material with excellent electrochemical performance. Here, polyacrylonitrile polymer layer-modified Co3S4 microspheres are anchored on a Ni foam substrate and then subjected to high-temperature carbonization to prepare a Carbon@Co3S4/Ni3S2/NF core–shell composite electrode. Its areal specific capacitance reached 1716 mF cm−2 at a current density of 1 mA cm−2 and 1128.9 mF cm−2 at 20 mA cm−2. Compared with the Co3S4/Ni3S2/NF electrode, its cycling stability is significantly improved, and the capacitance retention rate reaches 109% after 10,000 cycles. In addition, the assembled symmetrical supercapacitor achieves a higher energy density of 11.15 mWh cm−3 at a power density of 600 mW cm−3 and excellent cycling performance (approximately 90.3% capacitance retention over 5000 cycles). More importantly, this study illustrates a new method for improving the cycling stability and specific capacitance of transition metal sulfides, which provides the possibility of further practical application of the materials.

Unveiling a binary metal selenide composite of CuSe polyhedrons/CoSe2 nanorods decorated graphene oxide as an active electrode material for high-performance hybrid supercapacitors

With the unceasing upsurge in the evolution of electric vehicles flea market, supercapacitors (SCs) must be able to function under severe ecological situations. Although SCs are at the frontline in various technologies, their poor conductivity and energy density needs to be improved for commercial applicability. In this regard, various highly active electrode materials with compatible nanostructures and tunable chemical properties have been prepared and employed. In this work, a new category of CoSe2 nanorod-CuSe polyhedron- decorated graphene oxide (GO) (CCS@GO) hybrid electrode material was designed and studied for its application in high-performance hybrid asymmetric SCs (HASCs) for the first time. Owing to their specific architecture, high mesoporosity, and rapid transportation of electrons/ions, an asymmetric SC device with a CCS@GO//activated-carbon (AC) electrode exhibited excellent electrochemical properties that endowed it with a high specific capacitance of 192.8 Fg−1 at 1 Ag−1 and extensive energy and power densities of 54.6 Whkg−1 and 700 Wkg−1 respectively. Furthermore, the long-term durability over 10,000 cycles with capacitance retention of 82.5% suggests that the CCS@GO//AC HASC has immense potential for future-generation electronic devices and hybrid electric vehicles.

Highly efficient textile supercapacitors fabricated with graphene/NiO:Yb electrodes printed on cotton fabric

We report in this work the electrochemical performance of textile supercapacitors (SCs) fabricated with conductive electrodes of cotton-fabric+graphene. NiO:Yb microparticles (YbNi MPs) with cubic phase and sizes of 1.5–45 µm were introduced into the SCs in order to enhance their capacitance and energy density. Two different asymmetric devices were fabricated with electrodes of cotton+graphene (cathode) and cotton+graphene+YbNi MPs (anode). The first device (named as YbNi-SC) employed as separator a biodegradable rice paper and the second one (named as YbNi-S-SC) used as separator a recycled dishwasher sponge. According to the electrochemical characterization, the YbNi-SC and YbNi-S-SC devices presented a maximum capacitance of 640.6 and 1153.1 F/g, respectively. These devices also presented a maximum energy density of 128.1 and 230.6 Wh/kg, respectively, which are among the highest reported so far for textile SCs. A reference G-SC device made without YbNi MPs was also fabricated, but it presented a poor capacitance and energy density of 11.2 F/g and 22.1 Wh/kg, respectively. Moreover, The GC-SC device was completely discharged after only 1683 s (28.05 min), while the devices made with YbNi MPs (YbNi-SC and YbNi-S-SC) had discharge times of 4171 s (69.6 min) and 16,604 s (276.7 min), respectively. Moreover, the YbNi-S-SC device had superior capacitance retention (≈95%) over the YbNi-S-SC device (≈83%) after 500 cycles of charge/discharge. The optical absorbance, Raman and XPS spectra confirmed the presence of oxygen vacancy defects, Yb3+/Yb2+ and Ni3+/Ni2+ species in the SC electrodes, which acted as redox centers for the charge storage. Impedance measurements were also carried out and a reduction of the electrical resistance (≈36%) at the electrode/electrolyte interface was produced in the SCs containing the YbNi MPs, which facilitated the ion diffusion/transport in the SC electrodes. Hence, the results obtained here demonstrate that the textile SCs made with YbNi MPs are efficient for wearable applications.

Microwave-induced structural tunability of 3D δ-MnO2 microflowers for high-performance aqueous Zn-ion batteries

Rechargeable aqueous Zn//MnO2 batteries are the promising alternatives to lithium-ion batteries owing to their high safety, high energy density, low cost, and environmental friendliness. However, the unstable MnO2 cathode causes poor practical energy density and serious capacity fading. To overcome this issue, herein, a unique 2D nanosheets self-supported 3D δ-MnO2 microflower hierarchical architecture is rationally designed and synthesized by taking advantage of its microwave-absorbing characteristics. The 2D nanosheets with high surface area could expose numerous active sites for ions/electrons transfer. Also, the 3D assembled structure acting as building blocks would ensure structural stability for long-life cycles. Benefiting from these synergistic merits, the δ-MnO2 microflowers deliver a high capacity of 287.6 mA h g−1 at 0.5 C, an excellent rate capability of 202.7 mA h g−1 at 5 C, and a superior cycling retention of 76.5% over 1000 cycles at 10 C. Furthermore, a storage mechanism of H+/Zn2+ co-insertion accompanied by the deposition of zinc sulfate hydroxide hydrate is clarified by the aid of ex-situ XRD and SEM technologies. This work provides a new pathway for developing high capacity and long lifespan ZIBs.