Capacitive Deionization Cell Research Articles

2D hollow leaf shaped mesoporous carbon derived from ZIF-L for efficient capacitive deionization

Electrochemical treatment of saline or brackish water by capacitive deionization (CDI) is a novel resource-saving solution to ensure the availability of freshwater resources in the environment. MOF (metal–organic framework) derived carbon as a novel carbonaceous material in CDI has received considerable research attention. Among them, ZIF-L-derived carbon (ZC) suffers from problems such as self-aggregation, poor mesoporous structure, and low electrical conductivity, which lead to poor CDI performance. In this paper, a strategy of ZIF-L coated with polydopamine (PDA) is proposed to solve the above problems. When the amount of PDA was 0.5 g, ZIF-L@PDA0.5-derived carbon composite (ZPC0.5) is obtained for efficient capacitive deionization. The ZPC0.5 composite not only maintains the 2D leaf shaped structure consistent with ZIF-L, exposing more active sites, but also has an elevated mesopore occupancy ratio to promote solution diffusion. Meanwhile, the interaction between PDA and ZIF-L makes the ZPC0.5 have a cavity structure, which improves the mass transfer capacity. The resulting ZPC0.5 composite has a specific capacitance (165.8F g−1) that is 3.86 times higher than that of ZC (42.9F g−1). Consequently, in 1.2 V, 500 mg/L NaCl solution, the symmetric CDI cell ZPC0.5//ZPC0.5 exhibits an excellent desalination capacity (29.6 mg/g), which is 2.69 times that of the ZC//ZC.

Rational design of MoS2 nanoflowers-decorated carbon nanofibers with enhanced electronic transmission for boosting capacitive deionization

Capacitive deionization (CDI) has sparked considerable interest for its promising application in handling brackish water. Unfortunately, most traditional carbonaceous materials are still plagued by the limited desalination capacity and sluggish adsorption kinetics with the single adsorption mechanism and irrational pore structure. Herein, we developed a facile and affordable strategy to integrate electrospinning with hydrothermal method to fabricate MoS2 nanoflowers-decorated carbon nanofibers (MoS2/CNF) composite for boosting desalination performance. CNF not only serves as a supportive framework to inhibit the agglomeration of MoS2 nanosheets favoring the full contact with salt solutions, but also typically diminishes the charge transfer resistance of the composite. By taking advantage of the double layer adsorption of CNF and the hierarchically micro-mesoporous structure of MoS2 nanoflowers with large interlayer spacer for salt ions intercalation, the optimized sample MoS2/CNF-1 employed as a cathode for the asymmetric hybrid CDI cell showed an eminent capacity for desalination of 30.9 mg·g−1, an ultrafast rate for desalination of 3.7 mg·g−1·min−1, and an attractive circulation stability for desalination with the capacity reservation remaining at 94.8 % after 30 cycles in the solution of 500 mg·L−1 NaCl at 1.2 V. This research sheds fresh light on the evolution of advanced CDI electrode materials for practical utilization.

Nitrate and phosphate removal by capacitive deionization using nanocellulose/polypyrrole electrodes

Capacitive deionization (CDI) is a desalination technology that shows promise for removing nitrate and phosphate ions. The main components of CDI cells are electrodes, which are typically made from activated carbon (AC). However, the electrosorption performance of AC electrodes is limited because of the negative zeta potential, hydrophobicity, and oxidation resulting in co–ions’ repulsion. This study investigates binder-free polypyrrole-coated nanocellulose (NC/PPy) electrodes, which are hydrophilic and possess various functional groups, as an alternative to AC electrodes. An asymmetric CDI cell with an NC/PPy positive electrode demonstrated greater energy and charge efficiencies compared to a symmetric cell. The NC/PPy electrode exhibited a threefold electrosorption capacity towards nitrate ions compared to the AC electrode, and 4.5 times higher than for phosphate ions. The electrosorption mechanism revealed by first-principles modeling indicates similar sorption energies for nitrate and phosphate ions, with higher nitrate capacity due to co-ion repulsion and diffusion effects.

Understanding degradation of capacitive deionization cells: Full–cell simulations with anode corrosion

Capacitive deionization (CDI) is notable for its ability to perform low–energy desalination of brackish water and selective separation/recovery of salt and metal ions. However, redox side–reactions at porous carbon electrodes, such as the formation of weakly–acidic, oxygen–containing surface groups, limit ion electrosorption into double layers and electrode lifespan. In this study, we employ porous electrode theory to investigate the coupled effects of transport, electrosorption, redox reactions, and acid/base surface chemistry in practical flow through electrode (FTE) CDI cells, and we develop an efficient numerical solver that allows us to perform full–cell simulations over numerous charging/discharging cycles. We verify that our high fidelity model's predictions agree with analytical solutions in the limit of small voltage perturbations, and we demonstrate the significance of accurately capturing interplay between pH dynamics and surface chemistry. Our simulations demonstrate that anodic oxidation in FTE CDI is substantially inhomogeneous in space and in time, exhibiting cyclic protonation/deprotonation of surface groups and traveling, shock–like pH fronts. Moreover, we uncover connections between microscopic behavior and macroscopic performance parameters, demonstrating that this theoretical and numerical approach may substantially benefit the practical design optimization of CDI cells.

Scalable Production of 2D Non‐Layered Metal Oxides through Metal–Organic Gel Rapid Redox Transformation

Two‐dimensional (2D) nonlayered metal compounds with porous structure show broad application prospects in electrochemistry‐related fields due to their abundant active sites, open ions/electrons diffusion channels, and faradaic reactions. However, scalable and universal synthesis of 2D porous compounds still remains challenging. Here, inspired by blowing gum, a metal‐organic gel (MOG) rapid redox transformation (MRRT) strategy is proposed for the mass production of a wide variety of 2D porous metal oxides. Adequate crosslinking degree of MOG precursor and its rapid redox with NO3‐ are critical for generating gas pressure from interior to exterior, thus blowing the MOG into 2D carbon nanosheets, which further act as self‐sacrifice template for formation of oxides with porous and ultrathin structure. The versatility of this strategy is demonstrated by the fabrication of 39 metal oxides, including 10 transition metal oxides, one II‐main group oxide, two III‐main group oxides, 22 perovskite oxides, four high‐entropy oxides. As an illustrative verification, the 2D transition metal oxides exhibit excellent capacitive deionization (CDI) performance. Moreover, the assembled CDI cell could act as desalting battery to supply electrical energy during electrode regeneration. This MRRT strategy offers opportunities for achieving universal synthesis of 2D porous oxides with nonlayered structures and studying their electrochemistry‐related applications.

Scalable Production of 2D Non-Layered Metal Oxides through Metal-Organic Gel Rapid Redox Transformation.

Two-dimensional (2D) nonlayered metal compounds with porous structure show broad application prospects in electrochemistry-related fields due to their abundant active sites, open ions/electrons diffusion channels, and faradaic reactions. However, scalable and universal synthesis of 2D porous compounds still remains challenging. Here, inspired by blowing gum, a metal-organic gel (MOG) rapid redox transformation (MRRT) strategy is proposed for the mass production of a wide variety of 2D porous metal oxides. Adequate crosslinking degree of MOG precursor and its rapid redox with NO3 - are critical for generating gas pressure from interior to exterior, thus blowing the MOG into 2D carbon nanosheets, which further act as self-sacrifice template for formation of oxides with porous and ultrathin structure. The versatility of this strategy is demonstrated by the fabrication of 39 metal oxides, including 10 transition metal oxides, one II-main group oxide, two III-main group oxides, 22 perovskite oxides, four high-entropy oxides. As an illustrative verification, the 2D transition metal oxides exhibit excellent capacitive deionization (CDI) performance. Moreover, the assembled CDI cell could act as desalting battery to supply electrical energy during electrode regeneration. This MRRT strategy offers opportunities for achieving universal synthesis of 2D porous oxides with nonlayered structures and studying their electrochemistry-related applications.

Carbon-modified bentonite ion-exchange electrode in rocking-chair capacitive deionization with superior desalination capacity and high stability

Conventional carbon electrodes possess low desalination capacity and poor cycling stability, while faraday electrode materials are not economical with limited resource for capacitive deionization (CDI) technology. Therefore, exploring new type of electrode materials with high desalination capacity, low cost and excellent cycle stability is highly desirable. Bentonite (Bent) is an excellent ion-exchange material, with high natural abundance, super stability, but it has low conductivity. In this paper, a nitrogen-doped carbon modified Bent (NC@Bent) was prepared by in-situ polymerization of dopamine on the surface of Bent followed by carbonization. The N,C-modified thin layer on Bent improved the conductivity, boosting the charge transportation and ion diffusion. The NC@Bent was used as ion-adsorption electrode, exhibiting excellent electro-adsorption behavior. In a rocking-chair CDI (RCDI) cell, it delivered an extraordinary desalination capacity of 82 mg g−1 and super cycling stability with 90 % capacity retention in 50 cycles. Finally, the total dissolved salts in the actual groundwater were effectively reduced by using the current RCDI cell, meeting the WHO recommendation for drinking water. In consideration of the unique feature of low-cost and non-toxicity of Bent, this ion-exchange electrode material (NC@Bent) has much potential for drinking-water purification.

Manganese doping strategy for enhanced capacitive deionization performance of MoS2

Molybdenum disulfide (MoS2) has gained enormous attention as the electrode for capacitive deionization (CDI) by virtue of its fascinating layer structure and ion storage property. However, the sluggish intrinsic conductivity and limited ion storage capacity of MoS2 hampered their practical applications. In this work, a manganese doping strategy via a one-step hydrothermal process was adopted to fabricate manganese-doped MoS2 nanosheets (Mn-MoS2) for efficient capacitive desalination. It is shown that Mn-MoS2 presents an enlarged interlamellar spacing, enriched mesoporous structure, and excellent hydrophilicity. When used as a working electrode in a hybrid CDI cell, Mn-MoS2 delivered an outstanding salt removal capacity of 24.5 mg g−1 in a 500 mg L−1 NaCl solution. Notably, Mn-MoS2 presented fast kinetics in the desalination process, which reached equilibrium in 8 minutes with a removal rate of 3.06 mg g−1 min−1 and superior stability after 30 cycles, which outperformed the performance of most MoS2 based CDI electrode. XPS spectra indicated that the electronic structure of MoS2 could be modulated by Mn doping to generate 1 T phase, which further improved the intrinsic activity and ion storage capacity. This study paves a way for the design of MoS2 and its application in outstanding performance and durable CDI cell.

Plasma-assisted preparation of NiCoAl-layered double hydroxides with alarge interlayer spacing on carbon cloth forelectrochemical deionization

Capacitive deionization has been considered an emerging desalination technique in recent years, especially for its economic and energy-saving characteristics for brackish water. However, there are currently few studies on chloride ion removal electrodes, and the slow desalination kinetics limits their development. Ar-NiCoAl- layered double hydroxide (LDH)@ACC materials with an increased interlayer spacing were prepared by the in-situ growth of NiCoAl-LDHs nanosheet arrays on acid-treated carbon cloth (ACC) and subsequent Ar plasma treatment. The carbon cloth suppresses the agglomeration of the NiCoAl-LDHs nanosheets and improves the electrical conductivity, while the plasma treatment increases the interlayer spacing of NiCoAl-LDHs and improves its hydrophilicity. This provides rapid diffusion channels and more interlayer active sites for chloride ions, achieving high desalination kinetics. A hybrid capacitive deionization (HCDI) cell was assembled using Ar-NiCoAl-LDHs@ACC as the chloride ion removal electrode and activated carbon as the sodium ion removal electrode. This HCDI cell achieved a high desalination capacity of 93.26 mg g−1 at 1.2 V in a 1000 mg L−1 NaCl solution, a remarkable desalination rate of 0.27 mg g−1 s−1, and a good charge efficiency of 0.97. The capacity retention remained above 85% after 100 cycles in a 300 mg L−1 NaCl solution at 0.8 V. The work provides new ideas for the controlled preparation of two-dimensional metal hydroxide materials with a large interlayer spacing and the design of high-performance electrochemical chlorine ion removal electrodes.

Scalable NH4V4O10 clusters as functional network nodes on toughened porous carbon nanofibers for hybrid capacitive deionization

Layered vanadium-based compound (e.g., NH4V4O10) is acknowledged as an outstanding candidate for intercalation pseudocapacitance electrode of capacitive deionization (CDI) cells. However, the directed production of high-efficiency NH4V4O10-based self-supporting CDI electrodes and their structure–activity connection warrant more in-depth study. Herein, the delicate design and controllable construction of NH4V4O10 clusters on the freestanding porous carbon nanofiber (PCNF) scaffolds (the composite PCNFs/NH4V4O10 is defined as CNVO) using a new organic reducing agent of citric acid is proposed, where NH4V4O10 clusters as functional network nodes can improve the mechanical toughness, electrochemical capacitive performance, and desalination capability of the CNVO hybrid. The Na+ adsorption mechanism on CNVO is confirmed by ex-situ experimental characterizations and density functional theory (DFT) calculations. The hybrid CDI (HCDI) cell composed of the optimized CNVO cathode and PCNFs anode shows a desirable desalination capacity (45.07 mg g−1), a superior salt removal rate (16.4 mg g−1 min−1), an excellent energy utilization, and an acceptable cyclic regeneration ability in 500 mg L-1 NaCl solution. More importantly, the assembled HCDI system is promising for the desalination of reclaimed water from the printing and dyeing enterprise. This work highlights a scalable strategy that is experimentally and theoretically feasible to design and fabricate high-efficiency CDI electrodes.

Comprehensive investigation of capacitive deionization cells by response surface methodology

Freshwater resources are limited; thus, different technologies for desalination of brackish and seawater have been developed. Capacitive deionization (CDI) is one of the most promising desalination technologies owing to its low cost, simplicity, nonmoving parts, and low energy consumption. However, its energy consumption significantly increases with desalination of high-salinity water. In this regard, a good understanding of the effects of different process parameters on CDI energy consumption is crucial for further performance improvement. Therefore, the surface response methodology (RSM) was adopted to systematically study the effects of applying voltage, Stern layer capacity, volume and concentration of feed water, and volume of micropores on energy consumption and desalination time. The results showed that the Stern layer capacity and volume of micropores reduced desalination time by approximately 25% without significant changes in energy consumption. With the design of an improved electrode (improving the micropore structure for ion adsorption), the desalination time (Cycle) was reduced and a slight reduction in energy consumption was achieved. It can be claimed that any improvement in the physical (porosity) and electrical properties of the electrodes, results in an important increase in the performance of the CDI system.

Integration of capacitive deionization and forward osmosis for high water recovery and ultrapure water production: concept, modelling and performance analysis

ABSTRACT Forward Osmosis (FO), a membrane desalination technology and Capacitive Deionization (CDI), an electrically operated desalination technology, are numerically integrated utilizing four different configurations for the high-water recovery rate and ultrapure water production from brackish water resource. To minimize the wastewater rejection, the CDI desorption stream is continuously fed to the FO unit, efficiently recovering the remaining freshwater. To produce ultrapure water, freshwater stream obtained from FO is provided to the CDI cell, which adsorbs the remaining dissolved solute particles. These two configurations serve the purpose of both industrial as well as domestic water supply requirements. Continuing this concept, the formation of the other two configurations allows us to obtain fresh water and ultrapure water simultaneously and up to a 90% freshwater recovery rate for the areas with inadequate supply. The performance parameters to assess the integration are the Water Recovery Rate (WRR) and Specific Energy Consumption (SEC). The first configuration (CDI-FO), proposed for a high freshwater recovery rate, resulted in 79.33% WRR with an SEC of 0.689 kWh / m 3 . While, for the second configuration (FO-CDI), 34.25% water was recovered as 2.87 ppm ultrapure water along with 34.25% freshwater. The third proposed configuration (CDI-FO-CDI) had a WRR of 79.33%, 14.67% of which was recovered as ultrapure water of concentration 2.86 ppm. The fourth configuration (CDI-FO-FO) developed for high water recovery, removed the maximum of water from the feed stream with a WRR of 91.33% and remained energy-efficient, consuming an SEC of 0.908 kWh / m 3 .

Activated carbon cloth electrodes for capacitive deionization: a neutron imaging study

Neutron imaging was employed to track the uptake of Gd3+\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$^{3+}$$\\end{document} ions by the sub 2 nm micropores of charged activated carbon cloth electrodes from an aqueous Gd(NO3\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$_3$$\\end{document})3\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$_3$$\\end{document} solution. The transmitted neutron intensity evinces the persistent presence of Gd3+\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$^{3+}$$\\end{document} in the micropores during the discharge cycle, which is caused by the adsorption of oppositely charged ions. The charge efficiency of the activated carbon cloth system was determined by direct comparison with the imaged Gd3+\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$^{3+}$$\\end{document} concentration changes, with which the influence of ion swapping and resistive losses on capacitive deionization cells can be ascertained.

Optimization of activated carbon electrodes for desalination using capacitive deionization technique: strategies toward capacitive deionization cell refreshment

Optimization of activated carbon electrodes for desalination using capacitive deionization technique: strategies toward capacitive deionization cell refreshment

Desalination Performance of a Unique Capacitive Deionization Cell Optimized with ANSYS Flow Simulation

Desalination Performance of a Unique Capacitive Deionization Cell Optimized with ANSYS Flow Simulation

Construction of fully coated polypyrrole oxygen-barrier film based on MXene nanosheets for high reliability capacitive deionization

MXene has emerged as a promising capacitive deionization (CDI) faradic material for the advantages of excellent hydrophilicity, outstanding specific capacitance, and highly reversible ions intercalation/de-intercalation. However, its practical applications are severely restricted by the bottleneck problems of severe self-stacking and susceptibility to be oxidized by dissolved oxygen in aqueous solution. Herein, polypyrrole (PPy) oxygen-barrier film was fabricated and fully coated on the surface of MXene by the in-situ polymerization method to construct the composite electrode of PPy@MXene. In this unique architecture, the PPy oxygen-barrier film both enhances the antioxidant properties of MXene and weakens the strong interfacial interactions between MXene nanosheets to reduce the self-aggregation. Meanwhile, by doping different ions (Cl– and dodecyl benzene sulfonate, DBS–), PPy films were provided with excellent conductivity, abundant hole sites, and good ion exchange properties, which significantly promoted the charge priority adsorption capability of PPy-Cl@MXene and PPy-DBS@MXene electrodes. Consequently, compared with MXene//MXene cell, the PPy-Cl@MXene//PPy-DBS@MXene CDI cell presents dominant deionization capacity (55 mg g−1) and outstanding cycling stability (3 % degradation after 40 cycles). Most importantly, the morphology, structure and surface charge characteristics of the electrodes after long-term desalination confirmed that the MXene with fully coated PPy film was not destroyed by dissolved oxygen and maintained good structural integrity, which is conducive to improving the reliability of the MXene-based electrodes in CDI. Additionally, ion doped PPy@MXene electrodes highlight preferential adsorption to divalent cations. The work proposes a new strategy to advance the practical application of MXene by simultaneously solving its self-stacking and oxidative degradation issues.

Synthesis of black TiO2 nanotubes decorated biomass-derived spongy carbon as an electrode material for producing deionized water through capacitive deionization technology

The capacitive deionization (CDI) technique is considered a promising eco-friendly desalination method due to its high energy efficiency, ease of operation, and simplistic electrode regeneration capability. Thus, significant research is focused on developing highly efficient electrode materials with high electrochemical stability and salt electro-adsorption capacity (Sc) behavior during operation because these are the governing factors in examining the measured activity of fabricated CDI cells. In this manuscript, we report the synthesis of hydrogenated titanium nanotubes@spongy activated carbon (HTiO2 NTs@SAC) using pyrolysis and hydrothermal processes. The SAC is synthesized by the pyrolysis of spongy loofa in an inert atmosphere and further hydrothermally activating it in an aqueous potassium hydroxide solution. The hydrothermal process activates and enhances the hydrophilicity of SAC. HTiO2 is synthesized electrochemically at 20 V in 0.1 M perchloric acid. Such HTiO2 NTs@SAC configuration can provide excellent pathways to increase ion adsorption and improve the kinetics of charge transfer by enhancing the contact between the electrolyte and electrode at the interface. It is found that HTiO2 NTs@SAC has a specific capacitance (Cs) of 385.7 F g−1 compared with 332.7 F g−1 for SAC. The salt electrosorption capacity (Sc) of HTiO2 NTs@SAC electrode material is found to be 24.90 mg g−1 in 250 μS cm−1 saline solution at 1.2 V, which is much higher than the values obtained for SAC (9.8 mg g−1). HTiO2 NTs@SAC has also shown an antimicrobial effect toward gram-negative bacteria and exhibited good performance in the supercapacitor application, wherein HTiO2 NTs@SAC showed a higher Cs (505.55 F g−1) than SAC (380 F g−1) at 1 A g−1. Thus, we demonstrate that the prepared composite can be used as an energy storage material, an antibacterial material, and a CDI electrode in the CDI technology.

Pore engineering in robust carbon nanofibers for highly efficient capacitive deionization

Capacitive deionization (CDI) is considered as a revolutionary desalination method to alleviate the global water crisis. However, the current carbon-based CDI cells are constrained by the inferior desalination efficiency, resulting from the undesirable pore structure and sluggish electron/ion transport. Herein, a new porogen of silicalite-1 is proposed for the tailorable fabrication of flexible porous carbon nanofibers (PCNFs) by electrospinning, carbonization and alkali etching, where the surface area, total pore volume, mechanical robustness, specific capacitance, and electrosorption performance of the developed PCNFs are associated with the silicalite-1 dosage. The symmetric CDI unit assembled by the freestanding PCNF membrane electrodes shows a state-of-the-art desalination capacity (38.64 mg g−1), a remarkable salt removal rate (12.1 mg g−1 min−1), a desirable charge efficiency (82.36 %), an acceptable energy consumption (0.668 Wh g−1), and a satisfactory cyclic durability, and such excellent deionization performance can be explained by that the abundant hierarchical pores, the large accessible surface area, and the interconnected conductive carbon network effectively expedite the electron/ion transport. Additionally, the home-made CDI device has a favorable desalination capability toward the high-ion concentration seawater from the Yellow Sea (Xiaomai Island). This work not only validates the feasibility of silicalite-1 as the pore-forming agent for the targeted preparation of flexible PCNFs, but also it highlights the potential of pore engineering in freestanding PCNFs for advanced CDI.

Constructing ion-transport blockchain by polypyrrole to link CoTi-ZIF-9 derived carbon materials for high-performance seawater desalination

The instability and poor electronic conductivity of carbon materials derived from bimetallic zeolite imidazolate frameworks (ZIFs) pose significant challenges for utilizing these carbon materials as direct electrodes for achieving rapid electron transfer and high-performance capacitive deionization (CDI). However, modifying ZIFs through conductive polymers is a wise tool to enhance the target characteristics of ZIFs. Herein, a strategy is proposed to use polypyrrole (PPy) to interlink the carbon units derived from CoTi-ZIF-9 to construct a blockchain network system with high capacity and fast electrochemical kinetics for high performance CDI. In this system, PPy serves as a branched link connecting each carbon unit, so that the ions in the electrolyte can achieve low barrier and fast transmission in the three-dimensional network structure between the unit structures. As expected, with the improved charge transfer efficiency between electrode materials and electrolyte, the CDI cell exhibits excellent desalination capacity (77.3 mg g−1). In addition, density functional theory calculations also indicate that the introduction of PPy results in a higher electron density near the fermi surface of carbon material, which is conducive to electron transport and reaction kinetics. This work may provide important concepts for the design of CDI electrodes with high-conductivity and high-performance.

Binder-Free LiMn2 O4 Nanosheets on Carbon Cloth for Selective Lithium Extraction from Brine via Capacitive Deionization.

In this study, a three-step strategy including electrochemical cathode deposition, self-oxidation, and hydrothermal reaction is applied to prepare the LiMn2 O4 nanosheets on carbon cloth (LMOns@CC) as a binder-free cathode in a hybrid capacitive deionization (CDI) cell for selectively extracting lithium from salt-lake brine. The binder-free LMOns@CC electrodes are constructed from dozens of 2D LiMn2 O4 nanosheets on carbon cloth substrates, resulting in a uniform 2D array of highly ordered nanosheets with hierarchical nanostructure. The charge/discharge process of the LMOns@CC electrode demonstrates that visible redox peaks and high pseudocapacitive contribution rates endow the LMOns@CC cathode with a maximum Li+ ion electrosorption capacity of 4.71mmol g-1 at 1.2V. Moreover, the LMOns@CC electrode performs outstanding cycling stability with a high-capacity retention rate of 97.4% and a manganese mass dissolution rate of 0.35% over ten absorption-desorption cycles. The density functional theory (DFT) theoretical calculations verify that the Li+ selectivity of the LMOns@CC electrode is attributed to the greater adsorption energy of Li+ ions than other ions. Finally, the selective extraction performance of Li+ ions in natural Tibet salt lake brine reveals that the LMOns@CC has selectivity ( = 7.48) and excellent cycling stability (100 cycles), which would make it a candidate electrode for lithium extraction from salt lakes.