Ion Sieve Research Articles

Electrical Control of Magnetism through Proton Migration in Fe3O4/Graphene Heterostructure.

Ion migration has direct and crucial bearing on the crystal lattice field, electron filling, orbital occupation and spin polarization, which in turn changes the physical properties. Electric field is an effective way to control ion migration, but it may include simultaneous movement of multiple ions and increase the complexity of the system. Therefore, controllable and selective single ion migration with an unambiguous mechanism is highly desired. Here, the magnetic moments of Fe3O4 could be reversibly controlled by ionic liquid gating on the basis of migration of pure protons. A bilayer graphene could serve as an ion sieve, allowing only protons rather than oxygen ions or hydroxyl groups to participate in the gating process, thus guaranteeing the reversibility of magnetic property changes. This work is expected to supply an ideal arena for electrically sketching the functionalities of solid state materials based on the selective ion migration.

Unexpected Ion Sieving in Graphene Oxide Membranes

Unexpected Ion Sieving in Graphene Oxide Membranes

The Optimization of the Transition Zone of the Planar Heterogeneous Interface for High-Performance Seawater Desalination

Reverse osmosis has become the most prevalent approach to seawater desalination. It is still limited by the permeability-selectivity trade-off of the membranes and the energy consumption in the operation process. Recently, an efficient ionic sieving with high performance was realized by utilizing the bi-unipolar transport behaviour and strong ion depletion of heterogeneous structures in 2D materials. A perfect salt rejection rate of 97.0% and a near-maximum water flux of 1529 L m−2 h−1 bar−1 were obtained. However, the energy consumption of the heterogeneous desalination setup is a very important factor, and it remains largely unexplored. Here, the geometric-dimension-dependent ion transport in planar heterogeneous structures is reported. The two competitive ion migration behaviours during the desalination process, ion-depletion-dominated and electric-field-dominated ion transport, are identified for the first time. More importantly, these two ion-transport behaviours can be regulated. The excellent performance of combined high rejection rate, high water flux and low energy consumption can be obtained under the synergy of voltage, pressure and geometric dimension. With the appropriate optimization, the energy consumption can be reduced by 2 orders of magnitude, which is 50% of the industrial energy consumption. These findings provide beneficial insight for the application and optimized design of low-energy-consumption and portable water desalination devices.

Constructing chemical stable 4-carboxyl-quinoline linked covalent organic frameworks via Doebner reaction for nanofiltration

Covalent linkages are the key component of covalent organic frameworks (COFs). The development of stable and functional linkages is essential to expand the COFs family and broaden their application prospects. In this work, we report the synthesis of crystalline and chemical stable 4-carboxyl-quinoline linked COFs (QL-COFs) via Doebner reactions in both one-pot (OP) and post-synthetic modification (PSM) methods. Both methods can be universally applied to most of the reported imine COFs family via bottom-up construction or linkage conversion. Owing to the contractive pore size, more hydrophilic structure and better chemical stability than the conventional imine COFs endowed by 4-carboxyl-quinoline linkage, QL-COFs are supposed to possess a wider application range. We further demonstrate the nanofiltration membrane (NFM) based on QL-COF exhibited a desirable separation capacity with high rejection for small dye molecules (> 90%), high water permeance (850 L m−2 h−1 MPa−1) and tolerance of extreme conditions (1 M HCl/NaOH), which were benefitted from the enhanced properties of QL-COFs. Additionally, efficient ion sieving properties were also achieved by QL-COF membrane. We anticipate that this work opens up a way for the construction of robust and functional COFs materials for practical applications.

Hierarchically Self‐Assembled MOF Network Enables Continuous Ion Transport and High Mechanical Strength

AbstractComposite solid electrolytes have attracted significant interest because they overcome the defects of single‐component solid electrolytes. However, the discontinuous ion transport and weak mechanical support caused by randomly distributed powders lead to inferior ionic conductivity and poor mechanical strength. Herein, a hierarchically self‐assembled metal‐organic framework (MOF) network is designed to provide continuous ion transport and mechanical support for composite polymer electrolytes. This unique structure is achieved by constructing well‐ordered MOF nanocrystals along 1D polyimide fibers to provide continuous linear pathways for lithium ions at the micrometer scale, and the 1D MOF fibers are interconnected to form a monolithic 3D network for continuous Li+ transport in the bulk of composite electrolytes. Meanwhile, sub‐nano pores and Lewis acid sites in MOF nanocrystals can selectively confine the movement of larger anions as ion sieves to promote Li+ transport. In addition, the strong banding between MOF and polyimide, coupled with the robustness of the polyimide skeleton, endows the MOF network with high mechanical strength and flexibility. Accordingly, the resultant composite electrolyte delivers a high ionic conductivity and desired mechanical strength. This work shows that rational spatial arrangement of incorporated powders from disorder to order by a self‐assembly strategy can yield novel properties for composite solid electrolytes and solid‐state lithium batteries.

Fish‐scale‐like nano‐porous membrane based on zeolite nanosheets for long stable zinc‐based flow battery

AbstractZinc‐based flow batteries receive widespread attention due to their advantages of low cost and high energy density. However, zinc dendrites are easy to appear during the charge process, pierce the membrane and thus destroy the battery, which seriously restrict its further development. In this article, MFI‐type zeolite nanosheets (ns‐MFIs) with high mechanical strength and hydrophobicity arein situintroduced to porous polymer membranes, which spontaneously form turnup fish‐scale‐like structure through the one‐step phase inversion/surface segregation process. This special structure well disperses mechanical energy to provide effective protection characteristics to resist the penetration of zinc dendrites, and meanwhile promotes the uniform zinc depositions on the electrode by alleviating the water migration and accelerating zincate ion diffusion, so as to prolong the cycle life of the battery for more than 600 cycles, which is 4 times and 2.5 times longer than the commercial Nafion 212 and pristine porous polymer membrane, respectively. Moreover, the sub‐nano size pores and high‐aspect‐ratio ofns‐MFIs afford membranes extra ion sieving ability and transport area for the charging‐balancing ions OH−to ensure superior battery performance, delivering an average coulombic efficiency (CE) of ~98.5%, voltage efficiency (VE) of ~83.2%, and energy efficiency (EE) of ~81.9% at 80 mA/cm2.

Spray-drying assisted layer-structured H2TiO3 ion sieve synthesis and lithium adsorption performance

A spray-drying assisted solid-state method to prepare spherical layer-structured H 2 TiO 3 ion sieve (LSTIS) particles is reported herein. The effects of synthesis parameters (calcination temperature, calcination time, and the lithium-titanium molar ratio) on adsorption–desorption performance (the delithiation ratio, titanium dissolution loss, and the adsorption capacity) were investigated. The as-prepared LSTIS exhibited an equilibrium adsorption capacity of 30.08 mg·g −1 (average of 25.85 mg·g −1 over 5 cycles) and ultra-low titanium dissolution loss of less than 0.12% (average of 0.086% over 5 cycles). The LSTIS showed excellent selectivity toward Li + in Na + , K + , Mg 2+ , and Ca 2+ coexisting saline solutions where its adsorption capacity reached 27.45 mg·g −1 and the separation factors of Li + over the coexisting cations exceeded 100. The data suggests that the LSTIS is promising to competitively enrich Li + from saline solutions.

A high-performance hydroxide exchange membrane enabled by Cu2+-crosslinked chitosan.

Ion exchange membranes are widely used to selectively transport ions in various electrochemical devices. Hydroxide exchange membranes (HEMs) are promising to couple with lower cost platinum-free electrocatalysts used in alkaline conditions, but are not stable enough in strong alkaline solutions. Herein, we present a Cu2+-crosslinked chitosan (chitosan-Cu) material as a stable and high-performance HEM. The Cu2+ ions are coordinated with the amino and hydroxyl groups of chitosan to crosslink the chitosan chains, forming hexagonal nanochannels (~1 nm in diameter) that can accommodate water diffusion and facilitate fast ion transport, with a high hydroxide conductivity of 67 mS cm-1 at room temperature. The Cu2+ coordination also enhances the mechanical strength of the membrane, reduces its permeability and, most importantly, improves its stability in alkaline solution (only 5% conductivity loss at 80 °C after 1,000 h). These advantages make chitosan-Cu an outstanding HEM, which we demonstrate in a direct methanol fuel cell that exhibits a high power density of 305 mW cm-2. The design principle of the chitosan-Cu HEM, in which ion transport channels are generated in the polymer through metal-crosslinking of polar functional groups, could inspire the synthesis of many ion exchange membranes for ion transport, ion sieving, ion filtration and more.

Role of stacking faults and hydroxyl groups on the lithium adsorption/desorption properties of layered H2TiO3

Layered H2TiO3 ion sieve materials have shown promising selective lithium adsorption properties from brine solutions. Chemical delithiation of Li2TiO3 results in an increase of stacking faults and formation of isolated and hydrogen bonded OH groups. There is a critical knowledge gap in understanding the role of these stacking faults in lithium adsorption/desorption kinetics. Moreover, there is a lack of understanding in manipulation of surface hydroxyl groups to improve the lithium adsorption properties. In this work, layered Li2TiO3 (LTO) was synthesized using two different techniques, i.e., solid-state (ss-LTO) and hydrothermal (HT-LTO) methods to introduce varying concentrations of stacking faults. It was observed that HT-LTO synthesis method has a higher concentration of stacking faults, which results in slower elution of lithium from the precursor compared to ss-LTO. Interestingly, after complete lithium elution, both ss-H2TiO3 and HT-H2TiO3 ion sieves showed similar lithium adsorption properties. We also show that the lithium adsorption properties of layered H2TiO3 can be increased by oxygen annealing of the Li2TiO3 ion sieve precursor. Oxygen annealing improved the maximum lithium adsorption capacity by over 7% in a buffered solution (pH = 9.50) due to the increase in the relative amount of lattice oxygen and isolated surface hydroxyl groups. Spectroscopic studies (XPS, FTIR, and Raman) were used to further investigate and corroborate role of stacking faults and surface hydroxyl groups in the lithium adsorption/desorption process.

Integrate multifunctional ionic sieve lithiated X zeolite-ionic liquid electrolyte for solid-state lithium metal batteries with ultralong lifespan

Solid-state lithium metal batteries with higher energy density and safety are regarded as the promising next-generation energy storage devices. Porous materials hybrid with ionic liquids are becoming an important solid electrolyte due to the high ionic conductivity and enhanced interfacial compatibility. However, their poor electrochemical stability and limited Li+ transport pathways remain challenged. Herein, an ionic-liquid-X zeolite hybrid is designed as the solid composite electrolyte to settle the above issues. The three-dimensional open framework of X zeolite acts as the “reservoir” of the ionic liquid providing a solid interconnected pathway to facilitate an effective lithium transmission. This transport is supported by both the TFSI− adsorption and EMIM+ substitution in zeolite structure, which benefits the compatibility at electrolyte/lithium anode interface. The obtained composite electrolyte (Li-X-30) exhibits a superior ionic conductivity of 3.3 × 10−4 S·cm−1 and a widened electrochemical window of 5.4 V. An ultralong lifespan of the assembled solid-state LiFePO4//metallic lithium battery is achieved with an outstanding capacity retention of 96% after 850 cycles. The designed electrolyte with ultra-long cycling stability may provide inspiration for the development of frontier solid electrolytes with potential applications in K, Na and other types of energy storage systems.

An ion sieving conjugated microporous thermoset ultrathin membrane for high-performance Li-S battery

Lithium-sulfur (Li-S) battery is an attractive candidate for next-generation energy storage devices due to its high theoretical energy density, but its practical applications are hindered by polysulfides shuttling and lithium dendrite growth. In this study, a solution-processable conjugated microporous thermoset (CMT) was used as an ultrathin ion sieving layer on a commercial PP separator. The CMT layer is as thin as ∼200 nm and possesses continuous sub-nanochannels. Molecular dynamic simulations show that the nanoporous polymeric network allows Li-ion passage while blocking polysulfides shuttling between the electrodes based on size-exclusive effects. In addition, the CMT layer acts as a buffer zone for the uniform distribution of Li ions on the surface of the Li anode to suppress the growth of lithium dendrites. As a result, Li-S battery employing the CMT-modified polypropylene separator achieves a high initial capacity of 849.6 mAh g−1 with an ultralow attenuation rate of 0.037% per cycle over 1000 cycles at 1 C, as well as a capacity of 619.0 mAh g−1 at an ultrahigh current density of 10 C. Remarkably, it exhibits a capacity of 727.8 mAh g−1 with ∼ 77% capacity retention over 500 cycles lifespan at a high current density of 5C, showing great potential for practical high-performance Li-S batteries.

Biomimetic KcsA channels with ultra-selective K+ transport for monovalent ion sieving

Ultra-selective and fast transport of K+ are of significance for water desalination, energy conversion, and separation processes, but current bottleneck of achieving high-efficiency and exquisite transport is attributed to the competition from ions of similar dimensions and same valence through nanochannel communities. Here, inspired by biological KcsA channels, we report biomimetic charged porous subnanometer cages that enable ultra-selective K+ transport. For nanometer to subnanometer scales, conically structured double-helix columns exhibit typical asymmetric transport behaviors and conduct rapid K+ with a transport rate of 94.4 mmol m−2 h−1, resulting in the K+/Li+ and K+/Na+ selectivity ratios of 363 and 31, respectively. Experiments and simulations indicate that these results stem from the synergistic effects of cation-π and electrostatic interactions, which impose a higher energy barrier for Li+ and Na+ and lead to selective K+ transport. Our findings provide an effective methodology for creating in vitro biomimetic devices with high-performance K+ ion sieving.

Partially Reduced Graphene Oxide Membranes Crosslinked by an Anionic Porphyrin: Green Fabrication for High‐Performance Ion Sieving

AbstractGO membranes crosslinked by planar cation (e. g. TMPyP, a cationic porphyrin) meet the requirements of green fabrication, because TMPyP can pre‐assemble on GO sheets. However, their ion sieving performance are unsatisfactory. With shortened water channels, reduced graphene oxide (rGO) membranes owe high water flux, yet the retention of multivalent anions may goes down distinctly on account of Donnan effect decreasing obviously. Herein, we focus on the assembly between partially reduced graphene oxide (p‐rGO) and Anionic planar molecule (tetrasulfonic tetraphenyl porphyrin, TPPS), and then fabricate p‐rGO/TPPS composite membranes via assembling p‐rGO/TPPS sheets on base membrane. Anionic planar molecule is firstly used as crosslinking agent for graphene‐based membranes, which has the advantage of 100% atomic efficiency. The fabricated p‐rGO/TPPS membranes show better sieving performance than GO/TMPyP membranes on both side of rejection of Na2SO4 and water flux. Moreover, water flux go up to around another double though rejection decline slightly as the polyther sulfone (PES) base membrane with large surface pores is used.

MOF‐801 polycrystalline membrane with sub‐10 nm polymeric assembly layer for ion sieving and flow battery storage

AbstractMolecular sieving metal–organic framework (MOF) polycrystalline membranes have great potential for ion sieving and are desirable as efficient separators for devices of energy storage such as flow battery. Herein, we report a continuous MOF‐801 polycrystalline membrane with an ultrathin polymeric assembly layer (less than 10 nm) for the vanadium flow battery (VFB). Owing to the precise sub‐nanometer sieving pores and abundant H‐bond networks in MOF‐801 frameworks, the membrane exhibited better H/V selectivity (up to 194) and conductivity (about 0.028 S/cm) than commercial Nafion‐117 membrane (H/V selectivity: ~9.5, conductivity: 0.017 S/cm). VFB results revealed that a cell with above MOF polycrystalline membrane showed high coulombic efficiency (CE: 96.1%) and excellent energy efficiency (EE: 83.2%) at 20 mA/cm2, which was much comparable to Nafion membrane. This work demonstrates that MOF polycrystalline membrane is a promising candidate as ion sieving membrane for energy technique.

Constructing MIL-101(Cr) membranes on carbon nanotube films as ion-selective interlayers for lithium–sulfur batteries

It is of significant importance to suppress the polysulfide shuttle effect for the commercial application of lithium–sulfur batteries. Herein, continuous MIL-101(Cr) membranes were successfully fabricated on carbon nanotube films utilizing a simple in situ growth method, aiming at constructing interlayer materials for inhibiting the shuttle effect. Owing to the suitable pore aperture and super electrolyte wettability, the as-developed MIL-101(Cr) membrane can effectively inhibit the shuttle behaviour of polysulfides while allowing the fast transport of Li-ions simultaneously, working as an ionic sieve. Additionally, this MOFs membrane is also helpful in accelerating the polysulfide catalytic conversion. Therefore, the proposed interlayer delivers an extraordinary rate capability, showing a remarkable capacity of 661.9 mAh g−1 under 5 C. Meanwhile, it also exhibits a high initial capacity of 816.1 mAh g−1 at 1 C and an exceptional durability with an extremely low capacity fading of 0.046% per cycle over 500 cycles.

Composite membranes with nanofilms assembled on nanofiber supports for high-performance nanofiltration with antibacterial property

Nanofiltration has been widely applied in the field of desalination, wastewater treatment and water softening as an emerging and promising membrane separation technology. In order to break the trade-off effect between selectivity and permeability, we develop a novel thin-film composite nanofiltration membrane via a one-step interfacial assembly strategy of PDA/PEI nanofilms on nanofiber substrates. The ultrathin PDA/PEI nanofilm is defect-free, acting as the selective layer for ion sieving. The nanofiber substrate with high porosity provides plenty of mass transfer channels to reduce the membrane resistance, resulting in a enhanced water permeability of 18.1 L m-2 h-1 bar-1, which is 3 times higher than that prepared with commercial substrates. Attributed to the universally adhesive property of PDA, the PDA/PEI nanofilm can well integrate with the nanofiber substrate, enhancing the interfacial interaction strength and thus the composite structure stability. As a versatile platform, the abundant Ag nanoparticles are immobilized onto the PDA/PEI nanofilm surface, endowing the membrane with significant antibacterial property. This is of importance for membrane antifouling during the long-term and practical applications. This work could pave a facile way to develop advanced nanofiltration membranes with outstanding separation performance and various functions.

Crown-Ether Functionalized Graphene Oxide Membrane for Lithium Recovery from Water.

The massive worldwide transition of the transport sector to electric vehicles has dramatically increased the demand for lithium. Lithium recovery by means of ion sieves or supramolecular chemistry has been extensively studied in recent years as a viable alternative approach to the most common extraction processes. Graphene oxide (GO) has also already been proven to be an excellent candidate for water treatment and other membrane related applications. Herein, a nanocomposite 12-crown-4-ether functionalized GO membrane for lithium recovery by means of pressure filtration is proposed. GO flakes were via carbodiimide esterification, then a polymeric binder was added to improve the mechanical properties. The membrane was then obtained and tested on a polymeric support in a dead-end pressure setup under nitrogen gas to speed up the lithium recovery. Morphological and physico-chemical characterizations were carried out using pristine GO and functionalized GO membranes for comparison with the nanocomposite. The lithium selectivity was proven by both the conductance and ICP mass measurements on different sets of feed and stripping solutions filtrated (LiCl/HCl and other chloride salts/HCl). The membrane proposed showed promising properties in low concentrated solutions (7 mgLi/L) with an average lithium uptake of 5 mgLi/g in under half an hour of filtration time.

Solid-Phase Synthesis of ZnO@Bi2O3 Core–Shell Composites for Long-Life NiZn Batteries

In this work, core-shell ZnO@Bi2O3 composites are fabricated by a solid-phase method. SEM, TEM, and element mapping images confirm the uniform distribution of Bi2O3 film over the surface of ZnO particles. The formation mechanism is proposed. In addition, the electrochemical performance of core–shell ZnO@Bi2O3 composites is measured with the help of CV and EIS, and the optimal reaction parameters are obtained. Furthermore, the optimized ZnO@Bi2O3 with 3 wt % Bi2O3 as anode materials is used for the NiZn battery, which has delivered a high energy density of 177.23 W h kg–1 and outstanding cycle stability up to 3400 cycles. The Bi2O3 layer suppresses hydrogen evolution and effectively mitigates the migration of Zn(OH)42–, dendrite formation, and passivation of zinc anode due to substance effect and as ion sieve. We propose that this is a facile and easy synthetic method that can be scaled and may provide guidance for the synthesis of other core–shell structures.

An Ultrathin Functional Layer Based on Porous Organic Cages for Selective Ion Sieving and Lithium-Sulfur Batteries.

Thin films with effective ion sieving ability are highly desired in energy storage and conversion devices, including batteries and fuel cells. However, it remains challenging to design and fabricate cost-effective and easy-to-process ultrathin films for this purpose. Here, we report a 300 nm-thick functional layer based on porous organic cages (POCs), a new class of porous molecular materials, for fast and selective ion transport. This solution processable material allows for the design of thin films with controllable thickness and tunable porosity by tailoring cage chemistry for selective ion separation. In the prototype, the functional layer assembled by CC3 can selectively sieve Li+ ions and efficiently suppress undesired polysulfides with minimal sacrifice for the system's total energy density. Separators modified with POC thin films enable batteries with good cycle performance and rate capability and offer an attractive path toward the development of future high-energy-density energy storage devices.

Constructing MIL-101(Cr) membranes on carbon nanotube films as ion-selective interlayers for lithium-sulfur batteries.

It is of significant importance to suppress the polysulfide shuttle effect for the commercial application of lithium-sulfur batteries. Herein, continuous MIL-101(Cr) membranes were successfully fabricated on carbon nanotube films utilizing a simple in-situ growth method, aiming at constructing interlayer materials for inhibiting the shuttle effect. Owing to the suitable pore aperture and super electrolyte wettability, the as-developed MIL-101(Cr) membrane can effectively inhibit the shuttle behaviour of polysulfides while allowing the fast transport of Li-ions simultaneously, working as an ionic sieve. Additionally, this MOFs membrane is also helpful in accelerating the polysulfide catalytic conversion. Therefore, the proposed interlayer delivers an extraordinary rate capability, showing a remarkable capacity of 661.9 mAh g-1 under 5 C. Meanwhile, it also exhibits a high initial capacity of 816.1 mAh g-1 at 1 C and an exceptional durability with an extremely low capacity fading of 0.046 % per cycle over 500 cycles.