Charge-discharge Process Research Articles

Electrochemical Characteristics of Novel Fluorinated Ether Solvent for Lithium-Sulfur Batteries

Introduction In recent years, the development of electric airplanes, large drones, and other equipment has created a need for batteries with high energy density and high power density. Lithium-sulfur batteries have been investigated as such batteries. Electrolyte solutions applying carbonate solvents and ether solvents have been developed as electrolyte for lithium-sulfur batteries1. An electrolyte with ether-based solvents is lighter than that with carbonate-based solvents, so the former is expected to be an electrolyte for lithium sulfur batteries with high energy density. However, lithium-sulfur batteries based on ether solvents have difficulty in reversible charge-discharge reactions due to the dissolution of lithium polysulfide (Li2S x ) that occurs during the charge-discharge process2. In this study, we investigate the electrochemical characteristics of electrolytes to apply a new fluorinated ether (C14) which is resistant to elution of Li2S x . Experimental Sulfur-carbon composite (S-C) was prepared by compositing activated carbon (C-novel, Toyo Tanso) and sulfur in a ratio of 35:65 by weight using a thermal impregnation method. S-C was used as the active material and mixed with acetylene black (AB, DENKA), carboxymethyl cellulose (CMC), and styrene-butadiene rubber (SBR) to prepare a slurry. The cathode was obtained by coating the obtained slurry on an aluminum foil by a doctor blade method. An electrochemical cell was assembled with the obtained cathode as the working electrode, Li foil as the counter electrode, and LiTFSI dissolved in a mixture of dioxolane (DOL), dimethoxyethane (DME), and C14 at a concentration of 1 mol L-1 as the electrolyte. In order to clarify the electrochemical characteristics of the lithium sulfur battery with these electrolytes, constant current charge-discharge tests were conducted using the electrochemical cell described above. To clarify the coordination state of the solvent to lithium ions and lithium polysulfide in the electrolyte, IR spectra were measured for these electrolytes. Results and Discussion In the IR spectra for the solutions of Li2S x dissolved in DME, the intensity of the peak attributed to the asymmetric stretching of the C-O-C bond, which can be seen at around 1090 cm-1, increases with increasing concentration of Li2S x . The change in peak intensity appears to be due to the coordination of the structure of the diether in DME to the Li+ of Li2S x . On the other hand, in the IR spectra of Li2S x immersed in C14, the intensity of the corresponding peak was found to be similar to that of C14 only, regardless of the concentration of Li2S x . The results indicate that C14 is hard to coordinate to Li2Sx. This may be due to the fact that the functional group with fluorine in the structure of C14 is an electron-withdrawing group, which delocalizes the electrons located around O in the diether and weakens the coordinative force to Li2Sx. As a result of the constant-current charge-discharge test, it was confirmed that the voltage stagnated at about 2.3 V in the charge curves of the cell to which 1M LiTFSI / DOL : DME = 1 : 1 by vol.% was applied. The stagnation of the voltage is considered to be due to the shuttle reaction caused by the coordination of DME to lithium polysulfide and its dissolution into the electrolyte during the charge-discharge process. On the other hand, in the charge-discharge curves of the cell with 1M LiTFSI / C14, the stagnation of voltage that was observed in the cell with 1M LiTFSI / DME could not be confirmed, and it was turned out that the irreversible capacity was small. This should be due to the inability of C14 to coordinate with Li2S x . Acknowledgement A part of this research was conducted under a subcontract (JPNP15005) from the New Energy and Industrial Technology Development Organization (NEDO), a national research and development corporation. Reference 1) L. Gordin et al, ACS Appl. Mater. Interfaces, 6 (2014) 8006−80102) B. Zhang et al, ACS Energy Lett., 6 (2021) 537−546

Optimization of ternary composite @PANI/MoO3/h-BN and its electrochemical evaluation as an electrode material for supercapacitor application

The rapid charge-discharge process, high power density and longer cycle life which supercapacitor possess paves way as an important energy storage device in the electronic technology sector. Fast expanding applications in electric vehicles and portable electronics demand high energy storage electrodes. The expansive applications of two dimensional hexagonal boron nitride (h-BN) nanostructures accelerate usage in energy storage systems. Synthesis of Ternary composite consisting of polyaniline (PANI), h-BN (hexagonal boron nitride), molybdenum trioxide (MoO3) is reported with highest capacitance 518 F/g for PMB-135 composite at current density of 1 A/g. The highest energy density among all the composites was PMB-135 observed as 10.34 Wh/kg. This study with controlled size and uniformity may provide extensive self-attaining property for high performance energy storage materials.

Leave-Intercalation Theory and Conductive Mechanism during Charge-Discharge Process for Secondary Battery

The source of conductive ions in the charge and discharge process of AB5/β-Ni(OH)2, 2H-graphite/ LiMeO2and 2H-graphite/LiFePO4batteries is thought to be provided by the phase transition of positive active materials, so it is called phase transition theory. Through the detailed study of the charge and discharge processes of AB5/β-Ni(OH)2, 2H-graphite/ Li(Ni1/3Co1/3Mn1/3)O2and 2H-graphite/LiFePO4, it is found that the source of conductive ions is the de-intercalation of H (nickel-hydrogen battery) and Li (lithium-ion battery) in positive and negative active materials, and the de-intercalation theory is proposed. On this basis, the conductive mechanisms of these three types of batteries are clarified: The directional migration and movement of conductive ions under the action of electric field

The Influence of Reduced Graphene Oxide on the Texture and Chemistry of N,S-Doped Porous Carbon. Implications for Electrocatalytic and Energy Storage Applications.

In this work, we study the influence of reduced graphene oxide (rGO) on the morphology and chemistry of highly porous N,S-doped carbon cryogels. Simultaneously, we propose an easily upscalable route to prepare such carbons by adding graphene oxide (GO) in as-received suspended form to the aqueous solution of the ι-carrageenan and urea precursors. First, 1.25-5 wt% GO was incorporated into the dual-doped polymer matrix. The CO2, CO, and H2O emitted during the thermal treatments resulted in the multifaceted modification of the textural and chemical properties of the porous carbon. This facilitated the formation of micropores through self-activation and resulted in a substantial increase in the apparent surface area (up to 1780 m2/g) and pore volume (up to 1.72 cm3/g). However, adding 5 wt% GO led to overactivation. The incorporated rGO has an ordering effect on the carbon matrix. The evolving oxidative species influence the surface chemistry in a complex way, but sufficient N and S atoms (ca. 4 and >1 at%, respectively) were preserved in addition to the large number of developing defects. Despite the complexity of the textural and chemical changes, rGO increased the electrical conductivity monotonically. In alkaline oxygen reduction reaction (ORR) tests, the sample with 1.25 wt% GO exhibited a 4e- mechanism and reasonable stability, but a higher rGO content gradually compromised the performance of the electrodes. The sample containing 5 wt% GO was the most sensitive under oxidative conditions, but after stabilization it exhibited the highest gravimetric capacitance. In Li-ion battery tests, the coulombic efficiency of all the samples was consistently above 98%, indicating the high potential of these carbons for efficient Li-ion insertion and reinsertion during the charge-discharge process, thereby providing a promising alternative for graphite-based anodes. The cell from the 1.25 wt% GO sample showed an initial discharge capacity of 313 mAh/g, 95.1% capacity retention, and 99.3% coulombic efficiency after 50 charge-discharge cycles.

Insertion of AlCl3 in graphite as both cation and anion insertion host for dual-ion battery

Dual-ion batteries (DIBs) are emerging energy storage devices with the unique energy storage mechanism in which both anions and cations are involved during charge-discharge processes. Graphite is usually used as both cathode and anode in DIBs, however, the limited layer spacing and the elongated diffusion channels make the ion migration resistance larger. To break the bottleneck, a strategy is proposed by incorporating AlCl3 into the layer of graphite, which increases the layer spacing while acting as a pillar to stabilize the structure. In addition, a significant fraction of defects is inducted at the edges of the folds of graphite. This engineering accelerates the electron/ion transport on the stable graphite stacking microstructure. As a result, it could be used as both cation and anion insertion host in DIBs. Electrochemical tests showed that AlCl3-GICs-5 materials could deliver a Li+ storage capacity of 169.1 mAh g−1 at 2A g−1 when cycles consistently for over 500 cycles which is much higher than graphite (60.7 mAh g−1). Furthermore, when used as a PF6− insertion cathode in a DIB, it showed a high specific capacity of 100.8 mAh g−1at 100 mA g−1. This research is anticipated to provide inspiration to design new materials for DIBs.

LiFePO4 as a dual-functional coating for separators in lithium-ion batteries: A new strategy for improving capacity and safety

Lithium-ion batteries (LIBs) require separators with high performance and safety to meet the increasing demands for energy storage applications. Coating electrochemically inert ceramic materials on conventional polyolefin separators can enhance stability but comes at the cost of increased weight and decreased capacity of the battery. Herein, a novel separator coated with lithium iron phosphate (LFP), an active cathode material, is developed via a simple and scalable process. The LFP-coated separator exhibits superior thermal stability, mechanical strength, electrolyte wettability, and ionic conductivity than the conventional polyethylene (PE) separator. Moreover, the LFP coating can actively participate in the electrochemical reaction during the charge-discharge process, thus enhancing the capacity of the battery. The results show that the LFP-coated separator can increase the cell capacity by 26%, and improve the rate capability by 29% at 4 C compared with the conventional PE separator. The LFP-coated separator exhibits only 1.1% thermal shrinkage at 140 °C, a temperature even above the melting point of PE. This work introduces a new strategy for designing separators with dual functions for the next-generation LIBs with improved performance and safety.

Co9S8@N-doped carbon entangled with self-grown N-doped carbon nanotubes for advanced Li-ion storage

Herein, composites consisting of Co9S8 nanoparticles coated by N-doped carbon coating layer and self-grown N-doped carbon nanotubes (Co9S8@NC-NCNTs) were prepared and used for lithium storage. Co9S8@NC-NCNTs composites can deliver reversible capacities of 627 mAh·g−1 at 0.2 A·g−1 and 531 mAh·g−1 at 0.5 A·g−1, and are able to maintain a specific capacity of 494 mAh·g−1 at 2.0 A·g−1 after 1000 cycles. The excellent properties should be attributed to NC-NCNTs coating layer in composites which can not only promote the rapid transport of electrons and ions, but also ensure integrity of electrodes during charge–discharge processes.

The configuration of BiFe-PBA derived Bi2O3/BiFeO3 rectangular nanorods and NiCo-LDH/rGO for high-performance asymmetric hybrid supercapacitor with high energy density

The rectangular nanorods microstructure with abundant pores can reduce structural damage caused by the volume contraction during charging-discharging processes and enhance the specific capacitance. In this work, to enhance the energy density and accelerate the marketable applications of supercapacitors, Bi2O3/BiFeO3 rectangular nanorods with rich mesoporous structure derived from the iron‑bismuth based Prussian blue analogue are rationally designed to achieve a large specific capacitance through precipitation and annealing measures. There are a huge specific capacity of 741 F g−1 and long cycle life. The NiCo-LDH/rGO (954 F g−1) demonstrated an impressive stability of 86 % after 10,000 cycles and is utilized to establish asymmetric supercapacitor device. Amazingly, the NiCo-LDH/rGO//Bi2O3/BiFeO3 device achieves an enormous energy density of 59.7 Wh kg−1 at 800 W kg−1. In addition, the capacity retention ratio is 79.3 % after 7000 cycles. The work has suggested that Bi2O3/BiFeO3 has great potential as a negative electrode of supercapacitors.

Binder-Free LiNi0.8Mn0.1Co0.1O2/Multi-Walled Carbon Nanotube Prepared by One-Step Electrophoretic Deposition Method for Efficient Li-Ion-Battery Cathodes

A binder-free composite electrode of LiNi0.8Mn0.1Co0.1O2 (NMC811)/multi-walled carbon nanotube (MWCNT) with an extremely high NMC811 mass ratio (91 wt%) is prepared using an electrophoretic deposition process in a quick time (∼3 min). The spherical NMC811 particles are homogenously incorporated in the network created by MWCNTs, with desirable contact between these two components of the composite. The NMC811/MWCNT composite electrode showed a high first discharge capacity of 1.89 mAh cm−2 (163.4 mAh g−1) and 1.67 mAh cm−2 after 150 cycles at 0.1C with 88.3% capacity retention in the charge-discharge process. Compared with the conventional NMC811 electrodes prepared by the electrophoretic process (with carbon black and polyvinylidene fluoride) or doctor-blade strategy, superior electrochemical performance achieved in the binder-free composite NMC811/MWCNT electrode prepared by the electrophoretic process. This improvement is possible because the NMC811/MWCNT composite electrode could allow for a higher surface area and conductivity of the cathode material, a reactive interphase and adjustable available space in the electrode, and a homogenous distribution of the NMC particles in the MWCNT network. This scale-able, simple, binder and NMP-free, time-saving method with controllable growth deposit can be used to fabricate a variety of electrodes in storage systems.

In-situ strain characterization and stress analysis of SnO2@graphite@CNT electrodes for lithium-ion batteries by digital image correlation method

In this study, SnO2@graphite@CNT composite was synthesized by growing SnO2 nanoparticles within the interconnected three-dimensional network of graphite and carbon nanotubes using an acoustic chemistry method and a followed annealing treatment. As anode material for lithium-ion batteries, the composite exhibits high specific capacity and excellent cycling stability. The deformation behavior of the SnO2@graphite@CNT electrodes was in-situ monitored and recorded during discharge-charge process, and the strain fields onto the electrode surface was analyzed using digital image correlation technique. The dynamic evolution of plane stress in the electrode was evaluated by combining strain data with a mechano-electrochemical constitutive equation, and the contributions of mechanical and electrochemical parts to the plane stress also be discussed, respectively. The results provide valuable insights into the volume deformation behavior and mechano-electrochemical failure mechanism of SnO2-based electrodes for lithium-ion batteries.

Adaptive Interfacial Contact between Copper Nanoparticles and Triazine Functionalized Graphdiyne Substrate for Improved Lithium/Sodium Storage

AbstractThe high activity of nano‐sized metal particles (NMPs) makes it easy to appear uncontrolled aggregation, which seriously affects Li/Na storage in electrode materials. Introducing adaptive substrates with proper affinity to NMPs is an effective strategy that optimizes the stability and capacity of the related electrodes. Herein, a comprehensive strategy for the fabrication of adaptive interfacial contacts between metallic Cu nanoparticles (NPs) and triphenyl‐substituted triazine graphdiyne (TPTG) substrates is reported. The sp C in the acetylenic linkers and N heteroatoms in the triazine groups synergistically stabilized the Cu NPs loaded onto the TPTG substrates. The stabilizing effect of the TPTG substrate induces a reversible lattice change of the Cu NPs during the charge–discharge process, thus efficiently facilitating the stable transfer of Li+/Na+. Intrinsic mechanism analysis indicates that the heterojunction contact interface of Cu NPs/TPTG provides branched charge transfer pathways from Li/Na to the Cu NPs and TPTG substrates, which synergistically adjusts the affinity to Li/Na atoms and ultimately improves the electrochemical performance in Li/Na storage. The investigation of the structure–property relationship deepens the understanding of the function of heterointerfaces, which is essential for optimizing the performance of energy storage devices.

Improvement of Lithium-Sulfur Battery Performance by Porous Carbon Selection and LiFSI/DME Electrolyte Optimization.

High-concentration lithium bis(fluorosulfonyl)imide/1,2-dimethoxyethane (LiFSI/DME) electrolytes are promising candidates for highly reversible lithium-metal anodes. However, the performance of lithium-sulfur (Li-S) batteries with a high concentration of LiFSI/DME declines because LiFSI reacts irreversibly with lithium polysulfide, which is formed during the charge-discharge process of Li-S batteries. Hence, to apply high-concentration LiFSI/DME to Li-S batteries, we investigated carbon with an appropriate pore size for use in a sulfur composite cathode and optimized the composition of high-concentration LiFSI/DME. The results showed that the combination of carbon with mesopores of 2-3 nm diameter and 3 M LiFSI in DME/1,1,2,2-tetrafluoroethyl 2,2,3,3-tetrafluoropropylether (HFE) (1:1 by vol.) provided a high-rate capability (943 mA h g-1 at a rate of 2 C). Moreover, the ratio of the 50th discharge capacity to the 2nd discharge capacity (capacity retention) improved from 50.0 to 61.6% with HFE dilution of high-concentration LiFSI/DME. The improved performance was achieved by suppressing the dissolution of lithium polysulfide, decreasing the viscosity of the electrolyte, and forming a thin solid electrolyte interface on the lithium-metal anode due to HFE dilution.

Ferroelectric-Enhanced cathode kinetics toward High-Performance aqueous Zinc-Ion batteries

Rechargeable aqueous zinc ion batteries (AZIBs) offer promising potential for large-scale energy storage systems due to their high affordability and safety. However, their practical applications are hindered by the undesired rate capability and cycling stability of the used cathode, attributed to sluggish ions kinetics during charge–discharge process. Herein, we propose an electric field balancing strategy to regulate the electrolyte ions behavior by constructing a ferroelectric interface on the cathode surface using a prototypical of MnO2-based cathode. An appropriate thickness coating of ferroelectric materials coating (i.e., β-PVDF) on the MnO2 surface is theoretically and experimentally demonstrated to enhance the ion kinetics due to the optimized electrical distribution during electrochemical operations. Further comprehensive electrochemical mechanism studies reveal that the ferroelectric interface on the MnO2@β-PVDF not only promotes the diffusion of Zn2+ but also reduces the electrochemical overpotential (17.6 mV), resulting in improved electrochemical reversibility and capacity performance. The resultant MnO2@β-PVDF cathode exhibits the highest capacity of 277.6 mAh g−1 (at 0.1 A g−1) and capacity retention of 68.6% after 120 cycles, surpassing both the pristine MnO2 and non-ferroelectric materials coated MnO2 electrodes. This success presents a new approach to enhance the overall electrochemical performance of the cathodes for the practical application of AZIBs.

Aerosol derived carbon dots decorated boron nitride supported Zn-doped MoS2 for high performing flexible asymmetric supercapacitor

Alternative finding of toxic pollutant materials in proper utilization is a great challenge. Toxic and pollutant cigarette smoke having different π-conjugated organic components may work well as a precursor for carbon dots (CDs). In this work, cigarette smoke aerosol has been used for the synthesis of CDs and CDs have been further used for the fabrication of supercapacitor electrode. This methodology could be able to mitigate the two major problems-energy crisis and environment pollution. The smart combination of EDLC-type CDs deposited boron nitride (BN) and pseudocapacitive type Zn-doped MoS2 was able to enhance the supercapacitive performances. Heteroatom doping into MoS2 enhances the capacitive performances through the effective Faradic reactions. CDs and CDs deposited BN (CDs@BN) have been characterized using different characterization techniques. Zn-doped MoS2 has been uniformly grown on the CDs decorated BN (Zn–MoS2/CDs@BN) resulting in the stabilization of the electrode system. Zn–MoS2/CDs@BN nanohybrid delivered a specific capacitance (Sp.C) of 397 F/g in three-electrode system. Further, the asymmetric supercapacitor (ASC) device using Zn–MoS2/CDs@BN as cathode demonstrated wide potential range (up to 1.8 V) with a volumetric energy density of 3.42 mW h/cm3 and retaining a capacitance of ∼89% after 10,000 charging-discharging processes. Moreover, a flexible ASC device was made-up using viscous ionic electrolyte and it was able to glow a red LED, while it was bended in different angles. The methods described here will give a straightforward approach for using toxic-pollutant cigarette smoke to fabricate supercapacitor electrodes in order to compensate the upcoming energy crisis in a sustainable way.

Analytical solution for thermal-diffusion induced stress model and numerical simulation of battery structure during charging-discharging process

During the course of thousands of charging and discharging cycles, batteries commonly undergo capacity fade and resistance growth, known as electrode aging. This phenomenon is attributed to local inhomogeneous deformation, as well as the possibility of fracture within electrode particles due to complex multi-physical couplings. To mitigate electrode aging and slow down the rate of fading, it is crucial to develop protective designs and tailored battery management strategies. However, accurately predicting potential fracturing and conducting precise battery simulations remain open challenges. This study presents a battery aging simulation model that incorporates multiphysical couplings of heat, concentration, stress, electric, and phase fields to assess battery performance at both the structural and electrode particle levels. Initially, an analytical solution is derived to determine stress distribution at the particle level within the thermal-concentration-mechanical deformation coupling, enabling quick calculation of stress distribution. Subsequently, a comprehensive battery structure is constructed to simulate discharge performance. Furthermore, the model computes the stress levels and fracture potential of the electrodes, thereby identifying locations prone to aging. Analytical and numerical findings indicate that tensile stress on the surface of an individual electrode acts as the driving force for fracture during lithium intercalation. Moreover, electrodes in close proximity to the electrolyte generate higher heat, while those near the electrode current collector are more susceptible to fracturing.

Effect of charging operating conditions on open zeolite/water vapor sorption thermal energy storage system

Sorption thermal energy storage (STES) is one of the most promising solutions to realize inter-seasonal thermal energy storage for building heating. However, the analysis of charging operation parameters on the thermal energy storage performance of STES system is insufficient. In this paper, a STES experimental bench using zeolite 4A/water vapor as the sorption working pairs was built, and the charging/discharging experiments were conducted. The thermal energy chain during the full charging-discharging process was analyzed. The experimental results indicated that approximately 60% of the thermal energy provided by the heater was directly lost through the reactor outlet in the charging process, which seriously hindered the improvement of the thermal energy storage performance of the STES system, such as the coefficient of performance (COP). In addition, the influence of charging conditions on the thermal energy storage performance of the system was also investigated. Both the improvement of charging temperature and the reduction of charging air humidity are beneficial to enhancing the thermal energy storage performance of the STES system. When the charging temperature was 150 °C, the energy storage density of zeolite reached a maximum of 251 kWh/m3. The COP of system reduced by 28% when the relative humidity of charging air rose from 20% to 70%. The effect of the volume flow rate of charging air on the thermal energy storage performance of the system is insignificant. The COP of system maintained around 0.212 at different charging air volume flow rates.

Density Functional Theory Study of Bilayer Borophene-Based Anode Material for Rechargeable Lithium Ion Batteries.

The bilayer borophene has been successfully fabricated in experiments recently and possesses superior antioxidation and robust metallic properties, which holds great promise for the future anode materials of Li-ion batteries. Herein, using first-principles calculations, two bilayer borophenes including P6/mmm or P6̅m2 symmetry groups with or without vacancy defects are comprehensively explored and acted as electrode materials with high performance in Li-ion batteries. The charge density difference, adsorption energies, and Bader charge analysis are calculated and discussed for single lithium adsorbed on bilayer borophene. The results shown that with the increase of lithium concentration, the adsorption energies are rapidly decreased due to the repulsion of boron atoms except for the P6̅m2 systems with double side adsorption and corresponding energies remain the narrow range. Meanwhile, the partial density of states shows metallic character after lithium adsorption and indicates good conductivity for the charge-discharge process. Furthermore, small diffusion barriers, low average open-circuit voltage, can be achieved, and large storage capacity is up to 930.2 mA h/g at the lower lithium content of 0.375. These results propose that bilayer borophene might be a good choice for anode material applications in future Li-ion batteries with fast ion diffusion and high power density.

Carbon-doped Cu1.96S/C hollow microspheres for high-rate sodium storage performance

Currently, transition metal sulfides (TMSs) have attached great attention of researchers due to their various structural types and outstanding electrochemical activities. As one of typical TMSs, CuxS materials owes advantages of abundant reserves, lower material cost, excellent electronic conductivity when applied for sodium ion batteries (SIBs). However, CuxS materials inevitably suffer from the differentiation and volume expansion caused by the transformation reaction, which leads to poor electrochemical performance (especially the inferior cycling stability) in low voltage charge-discharge process. Herein, we utilized a facile way to synthesize Cu1.96S/C hollow microspheres by using a carbon-doped strategy. The Cu1.96S/C electrode was tested with optimized cut-off voltage range, demonstrating a remarkable reversible capacity of 351 mAh g−1 after 1500 cycles at 20 A g−1 current density, along with an average coulombic efficiency close to 100%. The outstanding rate performance and long-term cyclic performance of Cu1.96S/C electrode can be attributed to its carbon doped structure and pseudocapacitance behavior. These findings suggest that Cu1.96S/C composites exhibit the potential to enhance the high-rate capability of SIBs for industrial applications.

Development of a capacitive deionization stack with highly porous oxygen-doped carbon electrodes for brackish water desalination in remote coastal areas

This study demonstrates the development and application of a capacitive deionization (CDI) stack in treating saline water to provide safe drinking water to remote coastal areas. The commercial coconut shell-derived electrode (CAC) was chosen by its favorable characteristics, such as high porosity and specific surface area of 1742 m2 g−1, and a rich abundance of oxygen functional groups. CAC also displays exceptional capacitive properties, as evidenced by a specific capacitance of 72.7 F g−1, suggesting the potential for high-performance capacitive storage applications. Desalination experiments were conducted in both laboratory and field settings to assess the system's efficacy. On a laboratory scale, the CDI cell demonstrated a high desalination capacity of 14.95 mg g−1 and low energy requirements of 0.088 kWh m−3. The 40-pair CDI stack was successfully upscaled for desalination in the field, showing impressive capability for desalination and removal of unwanted ions in various water sources, including surface water, shallow groundwater, and deep groundwater. The CDI-treated effluent from the commonly used shallow groundwater source had a low electrical conductivity of 57 μS cm−1. Notably, the system maintained excellent desalination performance (98.4% Na+ and 96.9% Cl− removal) with steady repetition in the charging-discharging processes of the purified effluent over a 5-week operation, while also demonstrating impressive softening efficiency with a 97.6% reduction in CaCO3 hardness. Furthermore, the ion selectivity of the system was evaluated, with the following order observed: Na+ < K+ < Mg2+ < Ca2+ for cations, and As < Cl− < NO3− < SO42− for anions.

Proton-self-doped PANI@CC as the cathode for high-performance aqueous zinc-ion battery

Aqueous zinc-ion batteries (AZIB) have several advantages such as low cost, large theoretical capacity and good safety. However, the development of polyaniline (PANI) cathode materials has been limited by slow diffusion kinetics. Herein, proton-self-doped polyaniline@carbon cloth (CC) (PANI@CC) was prepared via in-situ polymerization, where polyaniline was deposited on an activated carbon cloth. The PANI@CC cathode exhibits a high specific capacity of 234.3 mA h g−1 at 0.5 A g−1, and excellent rate performance, delivering a capacity of 143 mA h g−1 at 10 A g−1. Furthermore, the reversible redox conversion during the charge–discharge process was studied using ex-situ X-ray photoelectron spectroscopy (XPS) and ex-situ Raman spectra. The results show that the excellent performance of the PANI@CC battery can be attributed to the formation of a conductive network between the carbon cloth and polyaniline. Also, a mixing mechanism involving insertion/extraction of Zn2+/H+ and a double-ion process is proposed. PANI@CC electrode is a novel idea for developing high-performance batteries.