High Mass Loading Research Articles

Facile Synthesis of S/Ti3C2Tx Mxene@Se Cathode for High-Sulfur-Loading Lithium–Sulfur Batteries

Lithium–sulfur batteries (LSBs) are gaining much attention because they offer a much higher theoretical energy density compared to traditional lithium-ion batteries. However, the cycling performance of LSBs with high sulfur mass loading is poor due to the shuttle effect, limiting the practical application of LSBs. In this work, a unique porous sulfur/Ti3C2Tx Mxene@selenium (S/Ti3C2Tx@Se) cathode of a LSB is synthesized by a simple hydrothermal method to address these challenges. In this composite, Ti3C2Tx forms a conductive framework and Se is tightly anchored on the framework. The Se inhibits the agglomeration of Ti3C2Tx and prevents the collapse of Ti3C2Tx. The S/Ti3C2Tx@Se composite can adsorb lithium polysulfides (LiPSs) and suppresses the shuttle effect and volume changes during cycling, improving the cycling stability of LSBs with high S loading. A high capacity of 812.2 mAh g−1 at 0.1 C with 5.0 mg cm−2 sulfur mass loading after 100 cycles is obtained. This work could inspire further research into high-performance S host materials for high-S-loading LSBs.

A Conductive Cu-Based Metal-Organic Framework Ribbon with High-Density Redox-Active Centers as Cathode for Stable High-Capacity Lithium-Ion Batteries.

Conductive Cu-based metal-organic framework (Cu-MOF) materials hold significant potential as cathodes for lithium-ion batteries (LIBs) due to their flexible structural design, high electronic conductivity, and independence from costly resources. However, their practical application is often limited by their capacity and cyclability. In this study, we report a one-dimensional Cu-MOF (DDA-Cu, DDA=1, 5-Diamino-4, 8-dihydroxy-9, 10-anthraceneedione) featuring extended π-d conjugated coordination ribbon and high-density redox-active centers, making it a stable, high-capacity cathode for LIBs. The π-d conjugated Cu-O₃N motifs embedded within the ribbon not only serve as redox-active centers for enhanced lithium-ion storage capacity but also contribute to structural robustness, enabling resistance against electrode solubility in organic electrolytes, thus ensuring superior cyclability. Furthermore, these π-d conjugated Cu-O₃N units promote efficient charge transfer, leading to high electronic conductivity at room temperature. These advantageous properties allow the Cu-MOF cathode to deliver a remarkable capacity (353 mAh g-1 at 0.05 A g-1) and exceptional cyclability, achieving capacity retention of 78% after 1000 cycles, surpassing state-of-the-art MOF electrodes. Additionally, this DDA-Cu demonstrates considerable wettability with the electrolyte, achieving outstanding performance even when tested in a lean electrolyte environment (2 μL mg-1) with a high mass loading of the MOF (6.8 mg cm-2).

A Conductive Cu‐Based Metal‐Organic Framework Ribbon with High‐Density Redox‐Active Centers as Cathode for Stable High‐Capacity Lithium‐Ion Batteries

Conductive Cu‐based metal‐organic framework (Cu‐MOF) materials hold significant potential as cathodes for lithium‐ion batteries (LIBs) due to their flexible structural design, high electronic conductivity, and independence from costly resources. However, their practical application is often limited by their capacity and cyclability. In this study, we report a one‐dimensional Cu‐MOF (DDA‐Cu, DDA=1, 5‐Diamino‐4, 8‐dihydroxy‐9, 10‐anthraceneedione) featuring extended π‐d conjugated coordination ribbon and high‐density redox‐active centers, making it a stable, high‐capacity cathode for LIBs. The π‐d conjugated Cu‐O₃N motifs embedded within the ribbon not only serve as redox‐active centers for enhanced lithium‐ion storage capacity but also contribute to structural robustness, enabling resistance against electrode solubility in organic electrolytes, thus ensuring superior cyclability. Furthermore, these π‐d conjugated Cu‐O₃N units promote efficient charge transfer, leading to high electronic conductivity at room temperature. These advantageous properties allow the Cu‐MOF cathode to deliver a remarkable capacity (353 mAh g‐1 at 0.05 A g‐1) and exceptional cyclability, achieving capacity retention of 78% after 1000 cycles, surpassing state‐of‐the‐art MOF electrodes. Additionally, this DDA‐Cu demonstrates considerable wettability with the electrolyte, achieving outstanding performance even when tested in a lean electrolyte environment (2 μL mg‐1) with a high mass loading of the MOF (6.8 mg cm‐2)

Root‐Growth‐Inspired Self‐Morphology‐Evolution of Microsized Bismuth Surrounded by Microsized Hard Carbon for Stabilized Sodium‐Ion Storage

AbstractAlloy‐type materials are desirable for high‐energy sodium‐ion batteries. Different from nanoengineering with pre‐reserving void space and confined carbon coatings, microsized particles promise high specific/volumetric capacities, easy manufacturing, and low cost but are prone to rapid capacity loss. Herein, inspired by the process of “root growth in soil”, microsized Bi particles (µm‐Bi, as “seeds”) surrounded by microsized hard carbon particles (µm‐HC, as “soil”) are ingeniously dispersed through a simple mixing approach. This design utilizes the morphological self‐evolution of µm‐Bi into Bi‐nanonetworks between dispersed µm‐HC during repeated (de)sodiations, leading to a stable capacity retention of 99.8% for 2000 cycles, higher than that of the µm‐Bi electrode (7.2%) at a high mass loading of 5.5 mg cm−2. The interconnected Bi‐nanonetworks and µm‐HC particles provide continuous electron pathways and facilitate electrolyte infiltration, which effectively boosts electrical contact, stable cycling, and high‐rate capability. Especially, the hybrid Bi40HC60 (optimized weight ratio) thick‐film electrode shows boosted comprehensive electrochemical performance, superior to HC and µm‐Bi electrodes. The Bi40HC60||Na3V2(PO4)3 full cell, assembled without any pre‐treatment, delivers 4500 stable cycles. This nature‐inspired strategy provides a simple yet practical approach for employing the electrochemically driven evolution of micro‐sized active materials and realizing high specific/volumetric capacities, fast kinetics, and long‐term cycling stability.

Incorporating MXene with Redox Carriers on Capacitive Carbon Cloth-Based Freestanding Electrodes for Power Applications

Abstract Battery-like organic materials including quinone-based electrodes with electrochemical activity have been extensively investigated for their use as electrode materials in energy storage devices due to their economic competitiveness and sustainable benefits. However, the intrinsic electrical insulating nature of organic quinones and their electrochemical reactivity limit power capability and stability upon charge/discharge cycling, respectively. Here, we report the preparation of a concentric layered architecture, MXene/Anthraquinone/Carbon Cloth (M/AQ/CC), by physisorption of anthraquinone onto the surface of carbon cloth via non-covalent π–π interactions, followed by dipping in exfoliated MXene suspension. The M/AQ/CC electrode, with a high mass loading (18.2 mg cm-2), delivered a capacity of 46 mAh g-1 (about 1 mAh cm-2 areal capacity or 6 mAh mL-1 volume) at 0.5 A g-1, with good rate performance and an enhanced cyclability over 5k cycles. This simple preparation method can also be applied to incorporate MXene with a series of alternative organic redox carriers on freestanding carbon cloth, including thionin acetate and anthraquinone-2-sulfonate. The improvement in electrochemical performance highlights an efficient approach to store more charges via redox reactions from organic quinones pi-stacked at carbon surfaces, thanks to a protective MXene shield that stabilizes the Faradaic behavior of quinones over repetitive charge-discharge processes. The simplicity and versatility of this method should enable design of many advanced electrode materials based on MXene/quinones/carbon cloth for power devices

High‐Potential and Stable Organic Cathode for Rechargeable Batteries with Fast‐Charging and Wide‐Temperature Adaptability

AbstractOrganic carbonyl compounds have been recognized as promising electrodes due to multiple active sites, abundant element resources and flexible structural designability, while their practical applications are still hindered by the easy solubility and low discharge potential. Herein, a novel bipolar polymer composite (TAC) was well‐designed by grafting p‐type triphenylamine units onto n‐type anthraquinone to form an extended π‐conjugated structure and in situ growing on carbon nanotubes, which was proved not only with higher discharge potential but also effectively suppress the dissolution issues. Moreover, TAC combined the advantages of different active sites and behaved a dual‐ion storage mechanism. Benefitting from the in situ polymerization process, TAC with tube‐type core–shell structure exhibited enhanced electron transport and improved utilization of active sites, resulting in high capacity (193 mAh g−1), outstanding rate performance (fast charging within 17 s), long‐term stability (a high capacity retention of 87 % after 1000 cycles) and high mass loading (10 mg cm−2). Additionally, TAC can well adapt to the temperature change, outputting a capacity of 72 mAh g−1 at −60 °C and 165 mAh g−1 at 80 °C. Such versatile polymer structure inspires the design of high performance organic materials for rechargeable batteries to satisfy high stability and wide temperature operations.

Decoupled Water Reduction and Hydrazine Oxidation by Fast Proton Transport MoO3 Redox Mediator for Hydrogen Production.

Water electrolysis powered by renewable energy is a green and sustainable method for hydrogen production. Decoupled water electrolysis with the aid of solid-state redox mediator could separate the hydrogen and oxygen production in time and space without the use of the membrane, showing high flexibility. Herein, a MoO3 electrode with fast proton transport property is employed as a solid-state redox mediator to construct a membrane-free decoupled acidic electrolytic system. The MoO3 electrode exhibits high specific capacity (204.3mAhg-1 at 5Ag-1) and excellent rate performance (92.8mAhg-1 at 150Ag-1) in the acidic environment. Due to the dense oxide-ion arrays, MoO3 still exhibits excellent performance under high mass-loading. In addition, a hybrid decoupled electrolysis system is also constructed by combining water reduction and hydrazine oxidation, which can not only generate high-purity H2 but also remove hydrazine hazards in acidic wastewater with lower energy consumption.

A MXene Modulator Enabled High‐Loading Iodine Composite Cathode for Stable and High‐Energy‐Density Zn‐I2 Battery

AbstractAchieving both high iodine loading cathode and high Zn anode depth of discharge (DOD) is pivotal to unlocking the full potential of energy‐dense Zn‐I2 batteries. However, this combination exacerbates the detrimental shuttle effect of polyiodide intermediates, significantly impairing the battery's reversibility and stability. Herein, this study reports an advanced high‐loading iodine cathode (denoted as MX‐AB@I) enabled by a multifunctional Ti3C2Tx MXene modulator, which presents high stability and energy density in Zn‐I2 batteries. Through comprehensive experimental and theoretical analyses, the intrinsic regulating mechanisms are elucidated by which the MXene modulator effectively suppresses polyiodide shuttling, enhances iodine conversion kinetics, and dramatically improves Zn anode reversibility. With the aid of the MXene modulator, the MX‐AB@I composite cathode achieves a high iodine mass loading of 23 mg cm−2 and realizes a practically high areal capacity of 4.0 mAh cm−2. When paired with a thin Zn anode (10 µm), this configuration realizes a high Zn DOD of 78.7% and a high energy density of 171.3 Wh kg−1, surpassing the majority of Zn‐I2 battery systems reported in the literature. This study presents an effective approach to designing high‐loading iodine cathodes for Zn‐I2 batteries by leveraging MXene modulators to regulate critical electrochemical reaction processes.

An Ultrafast and Ultralow‐Temperature 3D‐Printed All‐Organic Proton Pseudocapacitor

AbstractA critical challenge for pseudocapacitors applications is the rapid capacitance fading under extreme environments, which originates from sluggish diffusion kinetics of inorganic materials and tortuous ionic channels in conventional bulk electrodes. Herein, a novel 3D‐printed all‐organic proton pseudocapacitor (composed of 2,6‐diaminoanthraquinone (DQ)‐based anode and polyaniline‐based cathode) with chemical and structural stability is developed, which exhibits an extraordinary rate performance and cycle stability under ultralow temperature. The DQ molecules are anchored on reduced graphene oxide, which enhances the electronic conductivity and structural stability. Theoretical calculation and spectroscopic characterization reveal that the two‐electron transfer process involves quinone/hydroquinone transition. Exploiting the synergy of fast reaction kinetics of organic and the efficient ion diffusion paths of the 3D architecture, the 3D‐printed anode achieves an impressive areal capacitance of 10.14 F cm−2 at high mass loading (28.73 mg cm−2). The 3D‐printed all‐organic proton pseudocapacitor shows stable cycling performance at −80 °C and releases a high energy density of 0.76 mWh cm−2 at −60 °C. This work is instructive for the development of competitive ultra‐low temperature energy storage devices via integrating organic materials and 3D architectural electrode designs.

Electrodeposition Decoration of Pd0 on F‐Co(OH)2 Nanoarrays with Intentionally Introduced Pd2+ Species for Efficient Electrocatalytic Hydrodechlorination of 2,4‐Dichlorophenol

AbstractDeveloping a Pd‐based catalyst possessing high efficiency and low mass loading remains a big obstacle for the large‐scale application of electrocatalytic hydrodechlorination (EHDC) of chlorophenols (CPs). Herein, high dispersion Pd nanoparticles imbedded in Pd2+ hydroxide species are decorated on the surface of F−Co(OH)2 nanowire arrays with a newly developed electrodeposition and hydrolysis coupled process. EHDC of 2,4‐dichlorophenol (2,4‐DCP) with the as‐obtained Pd/F−Co(OH)2/NF‐a exhibits superior performance than other control samples in this work and literature reports. A 100 % removal of 2,4‐DCP is accomplished within 120 min, featuring fast reaction kinetics (kobs=5.0×10−2 min−1) and mass activity (MA=22.2 min−1 g−1Pd). Mechanism investigation shows that the intentionally introduced Pd2+ sites play a pivotal role in the adsorption of 2,4‐DCP, while high dispersion of Pd facilitates the generation of active H*, thus promoting the catalytic performance. This work presents a valuable example for designing high‐performance Pd‐based EHDC catalysts by composition tuning.

In Situ Construction of PANI/SHG/CNT Composite Electrodes with High Mass Loading for Flexible Supercapacitors by Rapid Frozen Interfacial Polymerization

In Situ Construction of PANI/SHG/CNT Composite Electrodes with High Mass Loading for Flexible Supercapacitors by Rapid Frozen Interfacial Polymerization

High Spin-State Modulation of Catalytic Centers by Weak Ligand Field for Promoting Sulfur Redox Reaction in Lithium-Sulfur Batteries.

The spin state of transition-metal compounds in lithium-sulfur batteries (LSBs) significantly impacts the electronic properties and the kinetics of sulfur redox reactions (SRR). However, accurately designing the spin state remains challenging, which is crucial for understanding the structure-performance relationship and developing high-performance electrocatalysts. Herein, the CoF2, specifically the Co2+ with 3d7 electrons in a high-spin state distribution (t2g 5eg 2), were tailored predictably for the first time through the weak coordination field effect of the F element. Both DFT calculations and experimental results confirm that the spin state of Co2+ transitions from low- to high-spin configurations and strongly interacts with sulfur species through Co-S and Li-F bonds during the SRR process. This interaction weakens the S-S bond, promoting its facile cleavage from both ends while also facilitating the rapid and uniform nucleation of Li2S2/Li2S, thus resulting in LSBs with a capacity of 447.7 mAh g-1 at 10 C rates and stable cycling for 1000 cycles, with an acceptable practical capacity of 585 mAh g-1 at a high sulfur loading mass of 10 mg cm-2. This work achieves rational control of the active Co2+ d electron state through the field effect and enriches the application of spin control to accelerate SRR in LSBs.

Breaking Mass Transport Limit for Hydrogen Evolution-Inhibited and Dendrite-Free Aqueous Zn Batteries.

It is commonly accepted that batteries perform better at low current densities below the mass-transport limit, which restricts their current rate and capacity. Here, it is demonstrated that the performance of Zn metal electrodes can be dramatically enhanced at current densities and cut-off capacities exceeding the mass-transport limit by using pulsed-current protocols. These protocols achieve cumulative plating/stripping capacities of 11.0 Ah cm-2 and 3.8 Ah cm-2 at record-high current densities of 80 and 160 mA cm-2, respectively. The study identifies and understands the promoted (002)-textured Zn growth and suppressed hydrogen evolution based on the thermodynamics and kinetics of competing reactions. Furthermore, the over-limiting pulsed-current protocol enables long-life Zn batteries with high mass loading (29 mgcathode cm-2) and high areal capacity (7.9 mAh cm-2), outperforming cells using constant-current protocols at equivalent energy and time costs. The work provides a comprehensive understanding of the current-capacity-performance relationship in Zn plating/stripping and offers an effective strategy for dendrite-free metal batteries that meet practical requirements for high capacity and high current rates.

Synergistic Regulation of Anode and Cathode Interphases via an Alum Electrolyte Additive for High‐Performance Aqueous Zinc‐Vanadium Batteries

AbstractA zinc (Zn) metal anode paired with a vanadium oxide (VOx) cathode is a promising system for aqueous Zn–ion batteries (AZIBs); however, side reactions proliferating on the Zn anode surface and the infinite dissolution of the VOx cathode destabilise the battery system. Here, we introduce a multi‐functional additive into the ZnSO4 (ZS) electrolyte, KAl(SO4)2 (KASO), to synchronise the in situ construction of the protective layer on the surface of the Zn anode and the VOx cathode. Theoretical calculations and synchrotron radiation have verified that the high‐valence Al3+ plays dual roles of competing with Zn2+ for solvation and forming a Zn−Al alloy layer with a homogeneous electric field on the anode surface to mitigate the side reactions and dendrite generation. The Al‐containing cathode–electrolyte interface (CEI) considerably alleviates the irreversible dissolution of the VOx cathode and the accumulation of byproducts. Consequently, the Zn||Zn cell with KASO exhibits an ultra‐long cycle of 6000 h at 2 mA cm−2. Importantly, the VOx cathodes (VO2, V2O5 and NH4V4O10) in the ZS−KASO electrolyte showed excellent cycling stability, including Zn powder||VO2 cells and Zn||VO2 pouch cells. Even better, the full cell exhibits excellent cycling stability at low negative/positive (N/P) ratio of 2.83 and high mass loading (~16 mg cm−2). This study offers a straightforward and practical reference for concurrently addressing challenges at the anode and cathode of AZIBs.

Synergistic Regulation of Anode and Cathode Interphases via an Alum Electrolyte Additive for High-Performance Aqueous Zinc-Vanadium Batteries.

A zinc (Zn) metal anode paired with a vanadium oxide (VOx) cathode is a promising system for aqueous Zn-ion batteries (AZIBs); however, side reactions proliferating on the Zn anode surface and the infinite dissolution of the VOx cathode destabilise the battery system. Here, we introduce a multi-functional additive into the ZnSO4 (ZS) electrolyte, KAl(SO4)2 (KASO), to synchronise the in situ construction of the protective layer on the surface of the Zn anode and the VOx cathode. Theoretical calculations and synchrotron radiation have verified that the high-valence Al3+ plays dual roles of competing with Zn2+ for solvation and forming a Zn-Al alloy layer with a homogeneous electric field on the anode surface to mitigate the side reactions and dendrite generation. The Al-containing cathode-electrolyte interface (CEI) considerably alleviates the irreversible dissolution of the VOx cathode and the accumulation of byproducts. Consequently, the Zn||Zn cell with KASO exhibits an ultra-long cycle of 6000 h at 2 mA cm-2. Importantly, the VOx cathodes (VO2, V2O5 and NH4V4O10) in the ZS-KASO electrolyte showed excellent cycling stability, including Zn powder||VO2 cells and Zn||VO2 pouch cells. Even better, the full cell exhibits excellent cycling stability at low negative/positive (N/P) ratio of 2.83 and high mass loading (~16 mg cm-2). This study offers a straightforward and practical reference for concurrently addressing challenges at the anode and cathode of AZIBs.

High‐Entropy Electrolyte Driven by Multi‐Solvation Structures for Long‐Lifespan Aqueous Zinc Metal Pouch Cells

Aqueous zinc metal batteries (AZMBs) are promising for grid‐scale energy storage due to their low cost and high safety. However, poor stability and an unfavorable freezing point hinder their actual application. Herein, a ternary salts‐based high‐entropy electrolyte (HEE) composed of Zn0.2Na0.4Li0.4(ClO4)1.2·7H2O is proposed to address the above issues. The addition of perchlorate salts with different cations reduces the size of ion clusters, significantly increases the solvation structure species, and promotes the anion‐rich Zn2+ solvation structures, resulting in an enlarged electrochemical stability window, favorable viscosity and ionic conductivity, and low freezing point. Furthermore, characterization and calculations confirm that multiple types of solvation structures effectively increase the electrolyte entropy. As a consequence, the Zn/Zn symmetric cells in HEE can sustainably cycle for at least 1000 hours and 1500 hours under room and subzero temperatures, respectively. The Na0.33V2O5/Zn and polyaniline/Zn full cells can even last for 30000 and 20000 cycles without capacity decay at −20 °C, respectively. The pouch cells employing HEE deliver promising capacity and stability, even at high mass loading of active materials. This strategy of introducing multiple salts with different cations to construct a high‐entropy environment provides a facile approach for high‐performance and long‐lifespan AZMBs across a wide temperature range.

High-Entropy Electrolyte Driven by Multi-Solvation Structures for Long-Lifespan Aqueous Zinc Metal Pouch Cells.

Aqueous zinc metal batteries (AZMBs) are promising for grid-scale energy storage due to their low cost and high safety. However, poor stability and an unfavorable freezing point hinder their actual application. Herein, a ternary salts-based high-entropy electrolyte (HEE) composed of Zn0.2Na0.4Li0.4(ClO4)1.2·7H2O is proposed to address the above issues. The addition of perchlorate salts with different cations reduces the size of ion clusters, significantly increases the solvation structure species, and promotes the anion-rich Zn2+ solvation structures, resulting in an enlarged electrochemical stability window, favorable viscosity and ionic conductivity, and low freezing point. Furthermore, characterization and calculations confirm that multiple types of solvation structures effectively increase the electrolyte entropy. As a consequence, the Zn/Zn symmetric cells in HEE can sustainably cycle for at least 1000 hours and 1500 hours under room and subzero temperatures, respectively. The Na0.33V2O5/Zn and polyaniline/Zn full cells can even last for 30000 and 20000 cycles without capacity decay at -20 °C, respectively. The pouch cells employing HEE deliver promising capacity and stability, even at high mass loading of active materials. This strategy of introducing multiple salts with different cations to construct a high-entropy environment provides a facile approach for high-performance and long-lifespan AZMBs across a wide temperature range.

High-Potential and Stable Organic Cathode for Rechargeable Batteries with Fast-Charging and Wide-Temperature Adaptability.

Organic carbonyl compounds have been recognized as promising electrodes due to multiple active sites, abundant element resources and flexible structural designability, while their practical applications are still hindered by the easy solubility and low discharge potential. Herein, a novel bipolar polymer composite (TAC) was well-designed by grafting p-type triphenylamine units onto n-type anthraquinone to form an extended π-conjugated structure and in situ growing on carbon nanotubes, which was proved not only with higher discharge potential but also effectively suppress the dissolution issues. Moreover, TAC combined the advantages of different active sites and behaved a dual-ion storage mechanism. Benefitting from the in situ polymerization process, TAC with tube-type core-shell structure exhibited enhanced electron transport and improved utilization of active sites, resulting in high capacity (193 mAh g-1), outstanding rate performance (fast charging within 17 s), long-term stability (a high capacity retention of 87 % after 1000 cycles) and high mass loading (10 mg cm-2). Additionally, TAC can well adapt to the temperature change, outputting a capacity of 72 mAh g-1 at -60 °C and 165 mAh g-1 at 80 °C. Such versatile polymer structure inspires the design of high performance organic materials for rechargeable batteries to satisfy high stability and wide temperature operations.

3D-printed Bio-inspired porous electrode by bidirectional enhancement strategy with high mass loading and enhanced energy density for supercapacitors

The effective strategy for increasing areal capacity involves the use of 3D printed thick-electrode with high mass loading. However, thick-electrode still encounters challenges such as incomplete electrolyte penetration and slow ion transport. Here, we successfully prepared lignocellulosic nanofibrils (LCNFs) from abundant bamboo biomass and developed functional ink composed of LCNFs/ carbon nanotubes (CNTs) / polyaniline (PANI) / polyvinyl alcohol (PVA) for printing. An innovative 3D printing bidirectional enhancement strategy was proposed to increase the mass loading of active materials in the vertical direction and construct ion transport channels in the transverse direction. The biomimetic porous N-doped electrode obtained after annealing treatment exhibits a more continuous conductive network, larger surface area, higher utilization of active materials, and smoother ion transport pathways compared to thick-electrode. Therefore, the Triangles biomimetic electrode exhibits an enhanced areal/specific capacitance compared to thick-electrode, reaching 5.30 F·cm−2 (184.03 F·g−1) and 4.40 F·cm−2 (122.22 F·g−1) at 2 mA·cm−2, respectively. The symmetric device demonstrates an areal capacitance of 1.34 F·cm−2 at 1 mA·cm−2 and achieves an energy density of 0.186 mWh·cm−2 at a power density of 0.49 mW·cm−2. The work provides valuable insights into the design of electrode structures for high-performance supercapacitors.

Unravelling the critical role of electrochemical deposition parameters in determining cycling reversibility of alpha-nickel hydroxide in alkaline electrolyte

Nickel hydroxide (α-Ni(OH)2) with large interlayer spacing is a promising pseudocapacitive material with high theoretical capacitance and good rate capability. However, the phase transition reversibility between α-Ni(OH)2 and γ-NiOOH in alkaline electrolyte upon charging/discharging is still vague. In this study, the cycling reversibility of α-Ni(OH)2 has been systematically investigated via adjusting the electrochemical deposition parameters. Structure characterizations and electrochemical analysis clearly revealed that the precursor concentration, deposition voltage and time significantly affect the mass loading of active material, the thicknesses of deposited films and their morphologies. Increasing the precursor concentration, deposition voltage and time lead to high mass loading, thick film and agglomerated nanosheets, which deteriorated the charge transfer and ion diffusion that lead to inferior cycling reversibility. In contrast, thin film with small mass loading and vertically-aligned nanosheets can be obtained upon deposition under low precursor concentration, small deposition voltage and short time, which shows facilitated charge transfer, ion diffusion and thereby high phase transition reversibility. Therefore, choosing appropriate deposition parameters would be beneficial to improve the electrode's cycling reversibility, which can effectively guide the development of more metal hydroxides with enhanced charge storage capability.