Areal Current Density Research Articles

Visualising the Effect of Areal Current Density on the Performance and Degradation of Lithium Sulfur Batteries Using Operando Optical Microscopy

The degradation of lithium sulfur (Li-S) batteries poses significant challenges to their commercial viability and occurs largely due to the complex electrochemical reactions and structural transformations that take place during charge-discharge cycles. This study employs optical microscopy techniques to investigate and quantify the degradation mechanisms in Li-S batteries. By capturing high-resolution, time-lapsed images of both electrodes and the electrolyte-filled interelectrode space, key morphological changes can be identified and analysed, such as the formation and growth of lithium dendrites, sulfur dissolution, and electrode-electrolyte interface degradation. Quantitative image analysis is conducted to measure the extent of these changes, providing insights into their impact on battery performance. Our findings reveal critical correlations between specific morphological features and electrochemical inefficiencies, contributing to a deeper understanding of the degradation pathways in Li-S batteries. This optical microscopy approach offers a non-destructive, cost-effective, real-time method to monitor battery health, potentially guiding the development of more durable and efficient Li-S batteries.

Synergistic Configuration of Binary Rhodium Single Atoms in Carbon Nanofibers for High-Performance Alkaline Water Electrolyzer.

Electrochemical alkaline water electrolysis offers significant economic advantages; however, these benefits are hindered by the high kinetic energy barrier of the water dissociation step and the sluggish kinetics of the hydrogen evolution reaction (HER) in alkaline media. Herein, the ensemble effect of binary types of Rh single atoms (Rh-Nx and Rh-Ox) on TiO2-embedded carbon nanofiber (Rh-TiO2/CNF) is reported, which servesas potent active sites for high-performance HER in anion exchange membrane water electrolyzer (AEMWE). Density functional theory (DFT) analyses support the experimental observations, highlighting the critical role of binary types of Rh single atoms facilitated by the TiO2 sites. The Rh-TiO2/CNF demonstrates an impressive areal current density of 1 A cm-2, maintaining extended durability for up to 225 hin a single-cell setup. Furthermore, a 2-cell AEMWE stack utilizing Rh-TiO2/CNF is tested under industrial-scale conditions. This research makes a significant contribution to the commercialization of next-generation high-performance and durable AEMWE stacks for clean hydrogen production.

Polymer electrolyte with inorganic and organic salts for Na-Ion supercapacitor

The optimized high ion conducting polymer electrolyte film containing copolymer PVdF-HFP, 10 wt.% inorganic salt {sodium bis(trifluoromethane sulfonyl)imide (NaTFSI)} and 70 wt.% organic salt {1-butyl-1-methypyrrolidinium bis(trifluoromethane sulfonyl) imide ([BMPYr] [TFSI])} have been used for the fabrication of Na-ion supercapacitor. The optimized composition of the electrolyte film possesses maximum room temperature (RT) ionic conductivity (∼0.87 mS/cm), excellent mechanical stability and large operating potential window (∼5.5 V). Using this film and activated carbon electrode (ACE (AC∼0.8 mg/cm2)), electrochemical double layer capacitor (EDLC)/Na-ion supercapacitor has been fabricated. The bulk resistance of this cell is found to be 22.9 Ω which is an evidence of good electrode-electrolyte contact. The cyclic voltammetric (CV) results of the EDLC-cell displays almost rectangular shape which demonstrates their capacitive behavior. The fabricated Na-ion supercapacitor has delivered specific capacities of ∼173 F/g, 151.91 F/g, 145.32 F/g and 122.33 F/g at different areal current densities (∼0.5, 0.8, 1.0 and 2.0 mA/cm2, respectively) along with the coulombic efficiency ranging from 97.6% to 99.9% upto 4500 cycles at 1 mA/cm2. The obtained value of the specific capacitance(s) of the EDLC cell from cyclic voltammetry is in good agreement with the value obtained from galvanostatic charge-discharge (GCD) measurements. Also, a nearly stable cycling performance has been obtained at 1 mA/cm2 upto 2500 cycles and after that the value of the specific capacitance (CSP/CD) decreases slightly upto 4500 cycles. This decrease in CSP/CD value may be because of increased thickness of solid electrolyte interface (SEI) layer and its corresponding interfacial resistance. The maximum specific energy and power density at 0.5 mA/ cm2 areal current density for first cycle are 31.52 Wh/Kg and ∼472.8 kW/Kg, respectively. On using ACE having AC∼1.6 mg/cm2, the fabricated Na-ion EDLC-cell has given maximum value of specific capacitance as ∼72.6 F/g at 0.5 mA/cm2 alongwith coulombic efficiency in the range of 96.5 % to 99.5 %. For the first cycle, the energy as well power density increase (∼40.31 Wh/Kg and ∼499.12 kW/Kg, respectively) and show stable cyclability upto 3000 cycles.

Conformal Li2O2 Growth and Decomposition Within 3D Lithiophilic Nanocages of Metal–Organic Frameworks for High‐Performance Li─O2 Batteries

AbstractLi─O2 batteries (LOBs) have the largest theoretical capacity among current batteries, but the irreversible growth and decomposition of Li2O2 products in positive electrodes cause dramatic degradation of their capacities over charging–discharging cycles. Herein, a metal–organic framework is reported with bipyridinic N linkers attached to graphene (bpyN‐MOF/g) as a positive electrode material to overcome the challenge. The bpyN‐MOF/g promotes conformal Li2O2 growth during discharging, while allowing Li2O2 decomposition at a low overpotential (0.487 V vs Li+/Li at 200 mA gc−1) during charging process, outperforming the Pt/C‐based electrode (0.857 V). Moreover, 3D‐tomography and density functional theory calculations consistently support the Li2O2 growth and decomposition mechanism inside bpyN‐MOF/g. Furthermore, bpyN‐MOF/g//Li LOBs achieve an exceptional discharge capacity (17 275 mAh gc−1 at 100 mA gc−1) and steady cycling for 270 cycles at 1000 mAh gc−1 under 2000 mA gc−1. Additionally, high gravimetric capacity at low mass loadings (0.27–0.44 mg cm−2) and stable cycle operation at a high areal current density (0.5 mA cm−2) open new opportunities for various practical applications.

Achieving High‐Performance in Zinc Hybrid Capacitors with Zn(TFSI)2/PEGDME Molecular Crowding Electrolytes

AbstractAqueous Zinc‐hybrid capacitors (ZHCs) are gaining attention for their high‐safety, low cost, easy maintenance, high‐power, and longevity. Despite various strategies to mitigate dendrites, corrosion, and HER, practical application remains challenging. Here, we utilize an advanced polyethylene glycol dimethyl ether (PEGDME)‐based molecular crowding electrolyte (MCE) to significantly enhance performance of ZHCs. Our MCE offers a wider electrochemical stability window (2.7 V), low HER activity, and superior Zn anti‐corrosion properties due to reduced water activity compared to conventional electrolyte. This results in higher coulombic efficiencies (98–100 %) at various areal capacities and current densities, and longer longevity of Zn//Cu and Zn//Zn symmetric cells with MCE compared to conventional and water‐in‐salt electrolytes. The Zn/MCE/AC displays an enhanced voltage window (∼2 V), achieving the highest capacitance (281 F/g), competitive energy density (138 Wh/kg), low self‐discharge, and excellent cyclability (19100 cycles at 1 A/g with 100 % capacity retention), indicating that MCE is a promising approach for practical energy storage applications.

Low-tortuosity, high-loading electrodes for fast-charging quasi-solid-state lithium metal batteries

Structural design of electrodes is a widely adopted approach towards enhanced electrochemical performance in various battery systems. However, in quasi-solid-state lithium metal batteries, research has predominantly focused on developing gel polymer electrolytes (GPEs), with limited attention given to utilizing electrodes with specialized structural design. Herein, by exploiting the excellent wettability and permeability of the GPE, high-loading NMC-811 cathodes featuring aligned channels achieved through freeze-casting are integrated with in-situ UV-polymerized poly (butyl acrylate) (PBA). The aligned channels in the freeze-cast electrodes provide low-tortuosity pathways for smooth Li+ transport, facilitating rapid kinetics. Consequently, superior areal capacity can be delivered under high areal current density (e.g. 1 mAh cm−2 at 2 mA cm−2 and 0.7 mAh cm−2 at 3.8 mA cm−2), demonstrating the fast-charging capability of quasi-solid-state lithium metal batteries.

Zn-anode stability in additive added perchlorate electrolyte for aqueous Zn-MnO2 battery

Extensive research has been conducted on aqueous Zn-MnO2 batteries in the most common ZnSO4 electrolyte. However, the present study focuses on Zn anode stability and subsequent pairing with the commonly utilized MnO2 cathode in a low-concentration aqueous Zn (ClO4)2 electrolyte containing an organic additive, triethyl phosphate (TEP). The structural stability of Zn anodes in optimized additive-added and additive-free electrolytes is analyzed by assembling series of Zn∥Zn symmetry cells under various electrochemical conditions with varying depth of discharges between 20 and 60 %. As such, additive added electrolyte stabilizes the Zn anode over 250 h under high areal capacity/low areal current density of 38.3 mAh cm−2/11.3 mA cm−2 with 60 % depth of discharge at long half-cycle time of 29.5 h. The Zn-MnO2 paired cells in the Zn (ClO4)2 electrolyte with and without additives registered reversible capacities of 262 and 247 mAh g−1, respectively, at 0.05 A g−1. These electrochemical features are completely different from those of the common ZnSO4 electrolyte, whose electrochemical mechanism is still a subject of debate.

Theoretical design and performance of three-dimensional, pillared FeS2 cathodes

Three-dimensional (3D) electrode design can provide improved capacities and rate capabilities over conventional two-dimensional electrodes by enhancing electrical and ionic transport. Expanding upon our previous modeling efforts for conversion chemistry lithium-ion batteries, we develop a pseudo-four-dimensional (P4D) approach that is subsequently used to investigate the design of a pillared FeS2 electrode. The model considers transport in three dimensions with an additional “fourth” dimension corresponding to the solid-state lithium transport within the active material particles. Additionally, we allow for expansion of the active material during the conversion reaction to understand how internal stresses impact the electrochemical performance of the cell. By optimizing the model with respect to areal capacity, we are able to predict areal capacities up to 16.8mAh/cm2 for an areal current density of 1.78mA/cm2 and a 103% improvement for the three-dimensional electrodes over planar electrodes of equal volume. Despite the promising results, our simulations suggest that 3D design may be difficult for conversion cathode materials due to the large internal stresses that arise during conversion. Nevertheless, the model is robust and adaptable to other materials that may be more suitable for 3D electrodes due to a lesser change in volume during discharge.

Achieving Planar Zn Electroplating in Aqueous Zinc Batteries with Cathode-Compatible Current Densities by Cycling under Pressure.

The value of aqueous zinc-ion rechargeable batteries is held back by the degradation of the Zn metal anode with repeated cycling. While raising the operating current density is shown to alleviate this anode degradation, such high cycling rates are not compatible with full cells, as they cause Zn-host cathodes to undergo capacity decay. A simple approach that improves anode performance while using more modest cathode-compatible current densities is required. This work reports reversible planar Zn deposition under cathode-compatible current densities can instead be achieved by applying external pressure to the cell. Employing multiscale characterization, this work illustrates how cycling under pressure results in denser and more uniform Zn deposition, analogous to that achieved under high cycling rates, even at low areal current densities of 1 to 10mAcm-2. Microstructural mechanical measurements reveal that Zn structures plated under lower current densities are particularly susceptible to pressure-induced compression. The ability to achieve planar Zn plating at cathode-compatible current densities holds significant promise for enabling high-capacity Zn-ion battery full cells.

Bimetallic metal-organic frameworks -derived lithiophilic and conductive MnO/Co/C enabled intermittent deposition model for high-performance lithium metal anode

The design of lithiophilic three-dimensional (3D) skeletons has proven to be effective in inhibiting dendrite growth and improving the Coulombic efficiency of lithium metal anodes (LMAs). However, for the 3D skeletons with homogenous lithiophilicity, Li would preferentially deposit on the top of 3D collectors, what's more, the intrinsic low electrical conductivity of metal-organic frameworks (MOFs)-derived oxides which are often employed as the lithiophilic materials on 3D skeletons affects their electrochemical kinetics. We firstly prepare MnO/Co/C derived from MnCo-MOFs on carbon cloths (CC) by a simple method and a composite anode (Li-CC@MnO/Co/C) is obtained. The synergistic effect of the electrical conductivity of Co and lithiophilicity of MnO facilitates their electrochemical kinetics. The Li-CC@MnO/Co/C composite anode exhibites long cycle life and low hysteretic voltage in the symmetrical cell with a high areal capacity and current density (5 mA h cm−2, 5 mA cm−2) and a steady cycle performance of 80 mA h g−1 at 10 C for nearly 300 cycles in easter-based electrolyte. This work might propose a rational design for a high-performance LMA, particularly suitable for practical applications.

Rational Design of an In-Situ Polymer-Inorganic Hybrid Solid Electrolyte Interphase for Realising Stable Zn Metal Anode under Harsh Conditions.

The in-depth understanding of the composition-property-performance relationship of solid electrolyte interphase (SEI) is the basis of developing a reliable SEI to stablize the Zn anode-electrolyte interface, but it remains unclear in rechargeable aqueous zinc ion batteries. Herein, a well-designed electrolyte based on 2 M Zn(CF3SO3)2-0.2 M acrylamide-0.2 M ZnSO4 is proposed. A robust polymer (polyacrylamide)-inorganic (Zn4SO4(OH)6.xH2O) hybrid SEI is in situ constructed on Zn anodes through controllable polymerization of acrylamide and coprecipitation of SO4 2- with Zn2+ and OH-. For the first time, the underlying SEI composition-property-performance relationship is systematically investigated and correlated. The results showed that the polymer-inorganic hybrid SEI, which integrates the high modulus of the inorganic component with the high toughness of the polymer ingredient, can realize high reversibility and long-term interfacial stability, even under ultrahigh areal current density and capacity (30 mA cm-2~30 mAh cm-2). The resultant Zn||NH4V4O10 cell also exhibits excellent cycling stability. This work will provide a guidance for the rational design of SEI layers in rechargeable aqueous zinc ion batteries.

Rational Design of an In‐Situ Polymer‐Inorganic Hybrid Solid Electrolyte Interphase for Realising Stable Zn Metal Anode under Harsh Conditions

AbstractThe in‐depth understanding of the composition‐property‐performance relationship of solid electrolyte interphase (SEI) is the basis of developing a reliable SEI to stablize the Zn anode‐electrolyte interface, but it remains unclear in rechargeable aqueous zinc ion batteries. Herein, a well‐designed electrolyte based on 2 M Zn(CF3SO3)2‐0.2 M acrylamide‐0.2 M ZnSO4 is proposed. A robust polymer (polyacrylamide)‐inorganic (Zn4SO4(OH)6.xH2O) hybrid SEI is in situ constructed on Zn anodes through controllable polymerization of acrylamide and coprecipitation of SO42− with Zn2+ and OH−. For the first time, the underlying SEI composition‐property‐performance relationship is systematically investigated and correlated. The results showed that the polymer‐inorganic hybrid SEI, which integrates the high modulus of the inorganic component with the high toughness of the polymer ingredient, can realize high reversibility and long‐term interfacial stability, even under ultrahigh areal current density and capacity (30 mA cm−2~30 mAh cm−2). The resultant Zn||NH4V4O10 cell also exhibits excellent cycling stability. This work will provide a guidance for the rational design of SEI layers in rechargeable aqueous zinc ion batteries.

Protective layer for stable lithium-metal anodes at 60 mA·h/cm2 and 60 mA/cm2 with ion channel and inductive effect

Contradiction between ultrafast nucleation and deposition rates of lithium (Li) crystals at high rate and heterogeneity of Li+ flux resulting from concentration polarization has compromised the performance of Li metal anodes especially at high areal capacity and current density. Here, multifunctional protective layer consisting of MoO3 nanobelt films (MoO3-NF) is introduced on the surface of Li by a simple rolling method. The strong binding energy between Li and MoO3 guides the homogeneous nucleation and deposition of Li, while the nanobelt networks provide effective ion channels for uniform distribution of the Li+ flux. Because of the novel multifunctional protective layer, the MoO3-NF@Li anodes demonstrate a remarkable stability for 800 h with ultralow overpotential of 159 mV at extreme harsh conditions of 60 mA·h/cm2 and 60 mA/cm2. MoO3-NF@Li||LiNi0.6Co0.2Mn0.2O2 full-cells can run 100 cycles with a superior capacity retention of 84.2% under practical test conditions, demonstrating great potential for high output and energy-density metal batteries.

Prestoring lithium in a 3D carbon fiber cloth coated with MOF-derived MnO for composite lithium anodes with high areal capacity and current density

We propose a facile design utilizing a commercial carbon fiber cloth (CFC) coated with metal–organic-framework-derived MnO nanoparticles as a 3D host for prestoring molten lithium and successfully fabricate a CFC@MnO@Li composite anode.

Co3O4 nanoparticle modified N, P co-doped carbon paper as sodium carrier to construct stable anodes for Na-metal batteries.

Sodium (Na) metal batteries such as Na-ion batteries and Na-CO2 batteries are considered to be excellent alternatives to lithium batteries in terms of their potential applications because of their high specific capacity and low cost. However, the sodium anode showed low efficiency and poor cycling in Na-metal battery performance due to the formation of sodium dendrites and serious corrosion. In this work, nitrogen (N), phosphorus (P) co-doped carbon paper (NP-CP) modified with cobalt tetroxide (Co3O4) nanoparticles was prepared as the Na anode carrier (Co3O4@NP-CP), and a sodium-based composite anode (Na-Co@NP-CP) was further prepared by electrodepositing sodium. The experimental results indicate that the N, P and Co3O4 multi-doped carbon paper has good sodiophilicity, which can induce the uniform plating/stripping of Na+ ions and inhibit the growth of Na dendrites. The N, P doped carbon paper provides a high surface area and tremendous three-dimensional (3D) framework to effectively reduce the areal current density, facilitate the transfer of electrons, and enhance battery life. Therefore, Na-Co@NP-CP based symmetric cells exhibit stable cycling of over 1100 hours at current densities of 1 mA cm-2 and fixed capacity of 1 mA h cm-2. When the Na-Co@NP-CP anode couples with CO2, the assembled batteries can deliver a stable cycling of 165 cycles at current densities of 500 mA g-1 and limited capacity of 500 mA h g-1. When Na-Co@NP-CP anode couples with Na3V2(PO4)3 (NVP) cathode, the assembled cells exhibit lower hysteresis and batter cycling performance.

Toward feasible single atom-based hydrogen evolution electrocatalysts via artificial ensemble sites for anion exchange membrane water electrolyzer

Approaching an efficient anion exchange membrane water electrolyzer (AEMWE) with satisfactorily high kinetics in the alkaline hydrogen evolution reaction (HER) is desired. We design an advanced platinum (Pt) single atom (SA)-based electrocatalyst by incorporating the Ni nanoparticle as an artificial ensemble site adjacent to Pt SA. The designed Pt SA electrocatalyst achieves higher areal current density (500 mA cm−2 at 1.8 V) in the single cell of the AEMWE and better cell voltage stability than the Pt/C electrocatalyst. The Ni nanoparticle assists in separating the binding sites of H* and OH*, in which Ni atoms provide adsorption sites for H*, while OH* adsorbs on the Pt SA. This separation effect drastically accelerates the energy barrier required for the water dissociation reaction in the Volmer step and simultaneously optimizes the H* and OH* binding energy, which extremely enhances the alkaline HER kinetics, thereby demonstrating the feasibility of Pt SA electrocatalysts for AEMWE.

Architecture of hybrid electrode by the composition of CoMoO4 /rGO/PANI for asymmetric supercapacitors

The enormous developments in the area of smart and wearable technology have led to grow interest in innovative and portable energy storage devices. This study described the development and electrochemical behavior of asymmetric supercapacitors with a negative electrode of activated-carbon (AC) and positive electrode of cobalt-molybdate/reduced graphene-oxide/polyaniline (CoMoO4 /rGO/PANI). The positive electrode materials of CoMoO4 /rGO/PANI were synthesized using a facile hydrothermal approach. The nanocomposites were characterized using physico-chemical methods including nitrogen adsorption-desorption isotherm analysis, X-ray diffraction (XRD), field-emission scanning electron microscopy (FESEM), X-ray Photon Spectroscopy (XPS) and Raman spectroscopy. The CoMoO4/rGO/PANI nanocomposite showed a noticeable specific capacity of 630 C g−1 when tested with three electrodes in 3 M alkaline solution (KOH). The CoMoO4 /rGO/PANI //AC asymmetric device demonstrated the optimal specific capacitance of 350 C g−1 with an energy density of 96 W h kg−1 with current density of 1.4 A g−1. The assembled device demonstrated enhanced cyclic stability with outstanding capacitance retention of nearly 97 % after 10,000 cycles (at 51 mA cm2 areal-current density). This composite electrode has a lot of promise for usage in wearable technology, flexible electronics, and technological gadgets.

An intermittent lithium deposition model based on CuMn-bimetallic MOF derivatives for composite lithium anode with ultrahigh areal capacity and current densities

An intermittent lithium deposition model based on CuMn-bimetallic MOF derivatives for composite lithium anode with ultrahigh areal capacity and current densities

A Conversion Type Iron Anode for High-Areal-Capacity Hybrid Redox Flow Batteries

Redox flow battery (RFB) is one of the most promising technologies for energy storage owing to its advantages of high safety, high efficiency, and low cost.1 Hybrid RFBs such as Zn-based RFBs offer a much higher energy density compared to all liquid RFBs. However, they rely on metal dissolution/deposition electrodes, which suffer from severe dendrite issues and poor reversibility, especially at high areal capacity and high current density. These inherent challenges of metal electrodes preclude their practical deployment for large-scale and long-duration energy storage applications.To break from this intrinsic limitation, in this work, we exploited a high-loading conversion electrodes to replace metal deposition electrodes to achieve high cycling stability at high areal capacity/current density for hybrid RFBs. With this strategy, using Fe3O4/Fe(OH)2 conversion negative electrode as an example coupling with ferricyanide/ferrocyanide positive electrode, we demonstrated conversion type all-iron hybrid RFBs with an unprecedented high cycling areal capacity of 126.6 mAh cm–2 at 50 mA cm–2 for 200 cycles (1000 hours) and 215 mAh cm–2 at 60 mA cm–2 for 100 cycles (700 hours) without capacity decay.2 The conversion electrode eliminates the dendrite issues and limitations on metal areal capacity, demonstrating unprecedented high cycling areal capacity and current density compared to conventional dissolution/deposition zinc metal negative electrode. We will discuss the compositional/morphological stability of the Fe3O4/Fe(OH)2 conversion iron negative electrode during the hybrid RFB operation and the techno-economic analysis of developed conversion type all-iron hybrid RFB for practical applications. Acknowledgment: The work described herein was supported by a grant from the Research Grant Council (RGC) of the Hong Kong Special Administrative Region, China (project no. C1002-21G). Reference: (1) Yao, Y. X.; Lei, J. F.; Shi, Y.; Ai, F.; Lu, Y. C. Assessment methods and performance metrics for redox flow batteries. Nat. Energy 2021, 6 (6), 582.(2) Shi, Y.; Wang, Z.; Yao, Y.; Wang, W.; Lu, Y.-C. High-Areal-Capacity Conversion Type Iron-Based Hybrid Redox Flow Batteries. Energy Environ. Sci. 2021, 10.1039/D1EE02258J.

Realizing high energy density supercapacitors assisted by light-induced charging

The increasing demand for energy storage devices has initiated research on alternative sustainable energy storage mechanisms, such as supercapacitors. Here, we report a skillful design strategy that harvests visible light energy and has immense potential applications in boosting the storage capacity of supercapacitors – one of the energy storage devices. A down-conversion phosphor layer is introduced over a reduced graphene oxide-based supercapacitor electrode having an optical window to harvest visible light. The fabricated cell exhibits an excellent areal energy density of 233 μWh/cm2 (at an areal current density of 4 mA/cm2 for the voltage ranging from 2 to 4.25 V) under optical illumination, which is 2.5 times higher than that achieved without illumination. Under light illumination, the cell operates across a high voltage range (0–4 V) and current density (40 mA/cm2) and shows a light-induced charging voltage of 354 mV, without any external bias. Thus, such exceptional supercapacitor performance generates significant possibilities for developing novel energy storage devices with high energy and power densities, through which portable devices can be charged using visible light.