Ion Desolvation Research Articles

Ultra-Stable Aqueous Zinc Anodes: Enabling High-Performance Zinc-Ion Batteries via a ZnSiF6-Derived Protective Interphase.

Zinc-ion batteries (ZIBs) hold immense promise as next-generation energy storage solutions, however, the practical application of zinc anodes is hindered by dendrite formation and parasitic side reactions. Engineering a stable solid- eletrolyte interphase (SEI) is crucial for addressing these issues. This study proposes a novel strategy to enhance Zn anode performance by incorporating a ZnSiF6 additive into a standard ZnSO4 (ZSO) electrolyte. The ZnSiF6 additive facilitates the formation of a stable, fluorine-rich SEI on the Zn anode surface. Characterization reveals a hierarchical SEI structure, primarily composed of porous alkali zinc sulfate (ZHS) with embedded ZnF2. This unique architecture promotes rapid zinc ion desolvation and efficient transport, enhances corrosion resistance, and mitigates hydrogen evolution. Consequently, ZnSiF6-modified cells exhibit exceptional cycling stability, exceeding 3000 hours at 0.5 mA cm-2 and 560 hours at 10 mA cm-2, significantly outperforming ZSO-based cells. The modified cells also achieve high areal capacities (10 mAh cm-2), indicating superior zinc utilization. This work provides key insights for designing stable electrode/electrolyte interfaces, contributing to the development of high-performance aqueous ZIBs.

Push-Pull Electrolyte Design Strategy Enables High-Voltage Low-Temperature Lithium Metal Batteries.

Lithium (Li) metal batteries hold significant promise in elevating energy density, yet their performance at ultralow temperatures remains constrained by sluggish charge transport kinetics and the formation of unstable interphases. In conventional electrolyte systems, lithium ions are tightly locked in the solvation structure, thereby engendering difficulty in the desolvation process and further exacerbating solvent decomposition. Herein, we propose a new push-pull electrolyte design strategy, utilizing molecular electrostatic potential (ESP) screening to identify 2,2-difluoroethyl trifluoromethanesulfonate (DTF) as an optimal cosolvent. Importantly, DTF exhibits a moderate ESP minimum (-21.0 kcal mol-1) to strike a balance between overly strong and overly weak Li ion affinity, which allows the sulfonyl group to effectively pull Li ions without disrupting the anion-rich solvation structure. Simultaneously, the difluoromethyl group, with a high ESP maximum (37.3 kcal mol-1), pushes solvent molecules via competitive hydrogen bonding. This design reconstructs existing solvation structures and expedites Li ion desolvation. Furthermore, fluorinated DTF demonstrates excellent stability at elevated voltage and facilitates the formation of robust inorganic-rich interphases. Impressively, rapid charge transfer kinetics can be achieved employing designed electrolyte, and the LiNi0.8Mn0.1Co0.1O2 (NMC811)||Li cells demonstrate excellent charge-discharge cycling stability with a high capacity exceeding 153 mAh g-1 even at -40 °C, retaining over 93% of initial capacity after 100 cycles under a 4.8 V charging cutoff. This work provides insights into the design of low-temperature electrolytes with a wide electrochemical window, advancing the development of batteries for extreme conditions.

Heteroatom Immobilization Engineering toward High-Performance Metal Anodes.

Heteroatom immobilization engineering (HAIE) is becoming a forefront approach in materials science and engineering, focusing on the precise control and manipulation of atomic-level interactions within heterogeneous systems. HAIE has emerged as an efficient strategy to fabricate single-atom sites for enhancing the performance of metal-based batteries. Despite the significant progress achieved through HAIE in metal anodes for metal-based batteries, several critical challenges such as metal dendrites, side reactions, and sluggish reaction kinetics are still present. In this review, we delve into the fundamental principles underlying heteroatom immobilization engineering in metal anodes, aiming to elucidate its role in enhancing the electrochemical performance in batteries. We systematically investigate how HAIE facilitates uniform nucleation of metal in anodes, how HAIE inhibits side reactions at the metal anode-electrolyte interface, and the role of HAIE in promoting the desolvation of metal ions and accelerating reaction kinetics within metal-based batteries. Finally, we discuss various strategies for implementing HAIE in electrode materials, such as high-temperature pyrolysis, vacancy reduction, and molten-salt etching and anchoring. These strategies include selecting appropriate heteroatoms, optimizing immobilization methods, and constructing material architectures. They can be utilized to further refine the performance to enhance the capabilities of HAIE and facilitate its widespread application in next-generation metal-based battery technologies.

Electrolyte Formulation with Improved Ion Desolvation and Diffusion Kinetics, and Superior Anti-Corrosion Properties for Ultrawide-Temperature Supercapacitors (–70∼100°C)

Electrochemical energy storage (EES) devices operating over a wide temperature range are crucial for extreme applications like near-space exploration (–70 °C) and desert exploitation (80 °C). However, their electrochemical performance is still hindered by the high-energy-barrier desolvation process at low temperature and the parasitic redox corrosion reactions at high temperature. In this work, an ultrawide-operating-temperature-window supercapacitor is proposed by simultaneously regulating ion kinetics of electrolyte and modulating anti-corrosion property of current collector. The optimized kinetics at low temperatures (–70 °C) refer to the enhanced ion dissociation and accelerated desolvation process, which is precisely regulated by the medium dielectric constant and low donor number of both methyl propyl ketone (MPK) and methyl ethyl ketone (MEK) cosolvents. Meanwhile, the remarkable cycling stability at high temperatures (100 °C) is realized by the strengthened corrosion resistance of carbon cloth current collector. The combination of MEK/MPK based electrolyte and carbon cloth current collector enables the supercapacitor to achieve a superior low-temperature capacitance retention (91.13 % @ –60 °C and 75.4 % @ –70 °C), extended high-temperature cycling stability (69.2 % @ 100 °C, 10,000 cycles) and excellent power and energy densities (13,820 W kg–1 @ 20.68 W h kg–1). This research is expected to provide valuable references for the advanced design of EES devices with wide-operating-temperature range in future studies.

Deciphering the structural and kinetic factors in lithium titanate for enhanced performance in Li+/Na+ dual-cation electrolyte

The widespread application of Li4Ti5O12 (LTO) anode in lithium-ion batteries has been hindered by its relatively low energy density. In this study, we investigated the capacity enhancement mechanism of LTO anode through the incorporation of Na+ cations in an Li+-based electrolyte (dual-cation electrolyte). LTO thin film electrodes were prepared as conductive additive-free and binder-free model electrodes. Electrochemical performance assessments revealed that the dual-cation electrolyte boosts the reversible capacity of the LTO thin film electrode, attributable to the additional pseudocapacitance and intercalation of Na+ into the LTO lattice. Operando Raman spectroscopy validated the insertion of Li+/Na+ cations into the LTO thin film electrode, and the cation migration kinetics were confirmed by ab initio molecular dynamic (AIMD) simulation and electrochemical impedance spectroscopy, which revealed that the incorporation of Na+ reduces the activation energy of cation diffusion within the LTO lattice and improves the rate performance of LTO thin film electrodes in the dual-cation electrolyte. Furthermore, the interfacial charge transfer resistance in the dual-cation electrolyte, associated with ion de-solvation processes and traversal of the cations in the solid-electrolyte interphase (SEI) layer, are evaluated using the distribution of relaxation time, Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy. Our approach of performance enhancement using dual-cation electrolytes can be extrapolated to other battery electrodes with sodium/lithium storage capabilities, presenting a novel avenue for the performance enhancement of lithium/sodium-ion batteries.

π-d Interaction to promote Zn ion de-solvation and transference toward high-performance Zn-MnO2 battery

Aqueous zinc ion batteries (AZIBs) are one class of high-safety and low-cost electrochemical energy storage devices supplementary to the current lithium ion technologies. However, their cycling performance has been severely tethered by the high de-solvation barrier of hydrated Zn ions and uncontrolled dendrite growth and side reactions on the Zn anodes. Herein, an artificial zincophilic passivation layer is constructed on the Zn anode surface by impregnating the porous Zn-based zeolitic imidazole frameworks (ZIF-8) with polypyrrole of rich π-electron donation. This not only lowers the de-solvation and nucleation barriers through π-d interaction, but also offers spatial room for accommodating 3D matrix Zn storage, lending smooth Zn plating/stripping with greatly improved kinetics in addition to inhibited dendrite formation and side reactions. Consequently, at 5 mA cm−2 the as-modified Zn anodes demonstrate a high CE of 99.6 % for more than 1500 cycles in half-cells and a stable operation for more than 2500 h in symmetrical cells. The aqueous Zn-MnO2 full cells further present a superb cycling performance with a capacity retention of 86.3 % after 1200 cycles at 1 A g−1. This work underscores the application of zincophilic and porous passivation layer to mediate smooth Zn plating/stripping by modulating the de-solvation and nucleation energy barriers.

Investigation of ion desolvation in aqueous electrolyte with carbon electrode via electrochemical in-situ Raman

Energy storage is an essential means to stabilize the fluctuation of renewable energy generation. Based on desolvation of electrolyte ions, high density charge storage in nanoporous electrodes has attracted widespread attention. The mechanism of ion transport within nanopores is currently under exploration. In this work, electric double layer capacitor was established using porous carbon electrode. Electrolytes with different hydrated/desolvatd ion radii were selected. The ion desolvation process was observed indirectly and concisely by using electrochemical in situ Raman technique on the carbon electrode. It was found that for ion with bigger solvation shells, its Raman intensity fluctuated with the cell charging voltage, which was caused by the desolvation of electrolyte ions. The desolvated ion has a strong polarization effect on the electron cloud of carbon. The influence of electrolyte concentrations on desolvation was also explored. High concentration electrolyte exhibits greater increase in Raman peak intensity. Our approach provides a way to study the physical mechanism and interface behavior of ion desolvation in electrochemical devices.

Interfacial Zn ion capture and desolvation engineering for high-performance Zn metal anode

The uneven surface of planar zinc (Zn) metal anodes fundamentally reduces the electrochemical reversibility of aqueous Zn metal batteries due to dendritic growth. Herein, an interphase protection layer engineering is formed on the surface of the Zn metal anode through a solution-processed coating method. This interesting carbon layer, composed of carbon nanoparticles obtained from outer flame-derived candle soot (OFCS), exhibits excellent Zn ion capturing and storage capabilities, effectively reducing the accumulation of charge density on the Zn metal surface, providing a homogeneous Zn ion flux and inducing even Zn metal deposition. The OFCS@Zn can promote the desolvation of [Zn(H2O)6]2+ through strong interaction with Zn ions, mitigating corrosion and hydrogen evolution reactions. The multifunctional integration of the OFCS layer synergistically induces uniform Zn metal plating and inhibits side reactions. Consequently, in the OFCS @Zn | OFCS @Zn symmetric-cell tests, high-rate performance and deep charge/discharge capabilities are demonstrated. The OFCS@Zn anode-based pouch cell exhibits a high discharge capacity of 156.2 mAh g-1 and maintains a significant capacity retention rate of 95.4 % for 200 cycles at the current density of 1 A g-1, indicating its potential for enhanced battery stability and efficiency.

Topological Defect-Regulated Porous Carbon Anodes with Fast Interfacial and Bulk Kinetics for High-Rate and High-Energy-Density Potassium-Ion Batteries.

Carbonaceous materials are regarded as one of the most promising anodes for potassium-ion batteries (PIBs), but their rate capabilities are largely limited by the slow solid-state potassium diffusion kinetics inside anode and sluggish interfacial potassium ion transfer process. Herein, high-rate and high-capacity PIBs are demonstrated by facile topological defect-regulation of the microstructure of carbon anodes. The carbon lattice of the as-obtained porous carbon nanosheets (CNSs) with abundant topological defects (TDPCNSs) holds relatively highpotassium adsorption energy yet low potassium migration barrier, thereby enabling efficient storage and diffusion of potassium inside graphitic layers. Moreover, the topological defects can induce preferential decomposition of anions, leading to the formation of high potassium ion conductive solid electrolyte interphase (SEI) film with decreased potassium ion de-solvation and transfer barrier. Additionally, the dominant sp2-hybridized carbon conjugated skeleton of TDPCNSs enables high electrical conductivity (39.4 S cm-1) and relatively low potassium storage potential. As a result, the as-constructed TDPCNSs anode demonstrates high potassium storage capacity (504mA h g-1 at 0.1 A g-1), remarkable rate capability (118mA h g-1 at 40 A g-1), as well as long-term cycling stability.

High-pressure intrusion of double salt aqueous solution in pure silica chabazite: searching for cation selectivity

Heterogeneous lyophobic systems (HLSs), i.e. systems composed of a nanoporous solid and a non-wetting liquid, have attracted much attention as promising candidates for innovative mechanical energy storage and dissipation devices. In this work, a new HLS based on a pure silica chabazite (Si-CHA) and a ternary electrolyte solution (KCl + CaCl2) is studied from porosimetric and crystallographic points of view. The combined approach of this study has been fundamental in unravelling the properties of the system. The porosimetric experiments allowed the determination of the energetic behaviour, while high-pressure in situ crystallographic analyses helped elucidate the mechanism of intrusion. The results are compared with those obtained for systems involving the same zeolite but intruded with solutions containing only single salts (CaCl2 or KCl). The porosimetric results of the three Si-CHA systems intruded by simple and complex electrolyte solutions (KCl 2 M, CaCl2 2 M and the mixture KCl 1 M + CaCl2 1 M) suggest that the intrusion pressure is mainly influenced by the nature of the cations. The CaCl2 2 M solution shows the highest intrusion pressure and KCl 2 M the lowest, whereas the mixture KCl 1 M + CaCl2 1 M is almost in the middle. These differences are probably related to the higher hydration enthalpy and Gibbs energy of Ca2+ compared with those of K+. It has been demonstrated that partial ion desolvation is needed to promote the penetration of the species, and a higher solvation energy requires higher pressure. The `intermediate' value of intrusion pressure shown by the complex electrolyte solution arises from the fact that, statistically, the second/third solvation cation shells can be assumed to be partially shared between K+ and Ca2+. The stronger interaction of Ca2+ with H2O molecules thus also influences the desolvation of K+, increasing the pressure needed to activate the process compared with the pure KCl 2 M solution. This is confirmed by the structural investigation, which shows that at the beginning of intrusion only K+, Cl− and H2O penetrate the pores, whereas the intrusion of Ca2+ requires higher pressure, in agreement with the hydration enthalpies of the two cations.

Influence of the Capillary Design and Conditions upon the Transmission Efficiency of a Portable Ion Trap Mass Spectrometer

The capillary is a widely used atmospheric pressure interface in mass spectrometers that may be heated to enhance the desolvation of ions. In this study, the ion transmission efficiency of a portable ion trap mass spectrometer was investigated using capillaries with different inner diameters and temperatures, different vacuum pressures, and different ion optics designs. Due to the incomplete desolvation and the space charge effect inside the miniature ion funnel, the increase of ion intensities with the inner diameter of the capillary leveled off when the inner diameter of the capillary was larger than 0.37 mm. With the increase of capillary temperature, the ion intensities first increase due to better desolvation and then decrease due to greater diffusion loss. The optimal temperature of the capillary increases with the inner diameter of the capillary and the mass-to-charge ratio of ion. In addition, the pressures of different vacuum stages also exerted remarkable effects on the sensitivity of the portable mass spectrometer. From the perspective of instrument miniaturization, optimal transmission efficiency can be obtained when the first-stage vacuum pressure is maintained from 4 to 6 mbar. For a capillary with an inner diameter of 0.37 mm, the background of mass spectrum can be significantly reduced by replacing the pinhole behind the ion funnel with an off-axis skimmer.

Consummating ion desolvation in hard carbon anodes for reversible sodium storage

Hard carbons are emerging as the most viable anodes to support the commercialization of sodium-ion (Na-ion) batteries due to their competitive performance. However, the hard carbon anode suffers from low initial Coulombic efficiency (ICE), and the ambiguous Na-ion (Na+) storage mechanism and interfacial chemistry fail to give a reasonable interpretation. Here, we have identified the time-dependent ion pre-desolvation on the nanopore of hard carbons, which significantly affects the Na+ storage efficiency by altering the solvation structure of electrolytes. Consummating the pre-desolvation by extending the aging time, generates a highly aggregated electrolyte configuration inside the nanopore, resulting in negligible reductive decomposition of electrolytes. When applying the above insights, the hard carbon anodes achieve a high average ICE of 98.21% in the absence of any Na supplementation techniques. Therefore, the negative-to-positive capacity ratio can be reduced to 1.02 for full cells, which enables an improved energy density. The insight into hard carbons and related interphases may be extended to other battery systems and support the continued development of battery technology.

Impact of Source Conditions on Collision Cross Section Determination by Trapped Ion Mobility Spectrometry.

Collision cross section (CCS) values determined in ion mobility-mass spectrometry (IM-MS) are increasingly employed as additional descriptors in metabolomics studies. CCS values must therefore be reproducible and the causes of deviations must be carefully known and controlled. Here, we analyzed lipid standards by trapped ion mobility spectrometry-mass spectrometry (TIMS-MS) to evaluate the effects of solvent and flow rate in flow injection analysis (FIA), as well as electrospray source parameters including nebulizer gas pressure, drying gas flow rate, and temperature, on the ion mobility and CCS values. The stability of ion mobility experiments was studied over 10 h, which established the need for a delay-time of 20 min to stabilize source parameters (mostly pressure and temperature). Modifications of electrospray source parameters induced shifts of ion mobility peaks and even the occurrence of an additional peak in the ion mobility spectra. This behavior could be essentially explained by ion-solvent cluster formation. Changes in source parameters were also found to impact CCS value measurements, resulting in deviations up to 0.8%. However, internal calibration with the Tune Mix calibrant reduced the CCS deviations to 0.1%. Thus, optimization of source parameters is essential to achieve a good desolvation of lipid ions and avoid misinterpretation of peaks in ion mobility spectra due to solvent effects. This work highlights the importance of internal calibration to ensure interoperable CCS values, usable in metabolomics annotation.

Ion Sieve Interface Assisted Zinc Anode with High Zinc Utilization and Ultralong Cycle Life for 61 Wh/kg Mild Aqueous Pouch Battery.

The cycling stability of a thin zinc anode under high zinc utilization has a critical impact on the overall energy density and practical lifetime of zinc ion batteries. In this study, an ion sieve protection layer (ZnSnF@Zn) was constructed in situ on the surface of a zinc anode by chemical replacement. The ion sieve facilitated the transport and desolvation of zinc ions at the anode/electrolyte interface, reduced the zinc deposition overpotential, and inhibited side reactions. Under a 50% zinc utilization, the symmetrical battery with this protection layer maintained stable cycling for 250 h at 30 mA cm-2. Matched with high-load self-supported vanadium-based cathodes (18-20 mg cm-2), the coin battery with 50% zinc utilization possessed an energy density retention of 94.3% after 1000 cycles at 20 mA cm-2. Furthermore, the assembled pouch battery delivered a whole energy density of 61.3 Wh kg-1, surpassing the highest mass energy density among reported mild zinc batteries, and retained 76.7% of the energy density and 85.3% (0.53 Ah) of the capacity after 300 cycles.

Graphene acid-enhanced interfacial layers with high Zn2+ ion selectivity and desolvation capability for corrosion-resistant Zn-metal anodes

A Zn anode artificial interface capable of accelerating Zn2+ transfer/transport while achieving uniform and promoted Zn nucleation, ultimately resulting in stable and corrosion-free Zn anodes.

Solvation structure dependent ion transport and desolvation mechanism for fast-charging Li-ion batteries.

The solvation structures of Li+ in electrolytes play prominent roles in determining the fast-charging capabilities of lithium-ion batteries (LIBs), which are in urgent demand for smart electronic devices and electric vehicles. Nevertheless, a comprehensive understanding of how solvation structures affect ion transport through the electrolyte bulk and interfacial charge transfer reactions remains elusive. We report that the charge transfer reaction involving the desolvation process is the rate-determining step of the fast charging when ion conductivity reaches a certain value as determined by investigating electrolytes with eight conventional solvents (linear/cyclic carbonate/ether). The physicochemical characteristics of solvent molecules can result in strong ion-ion, moderate ion-dipole, strong ion-dipole, and weak ion-dipole/ion-ion interactions, respectively, in which the speed of the charge transfer reaction follows the above order of interactions. Among all solvents, dioxolane (DOL) is found to enable strong ion-ion interactions in electrolytes and thus exhibits exceptional fast-charging performance and it can still retain 60% of the initial capacity at 20C (1C = 170 mA g-1) with a polarization of merely 0.35 V. Further experimental characterization and theoretical calculation reveal that the aggregates in DOL electrolytes contribute to hopping assisted ion transport and facilitate the desolvation process of Li+. Our results deepen the fundamental understanding of the behavior of Li+ solvation and provide an effective guiding principle for electrolyte design for fast-charging batteries.

Three-dimensional covalent organic framework-based artificial interphase layer endows lithium metal anodes with high stability

A 3D COF with a fully covalent dia topology was successfully utilized as artificial SEI layers to modulate the Li+ microscopic dynamics related to Li ion desolvation, charge transfer, migration pathways, and deposition morphology.

The Zn Deposition Mechanism and Pressure Effects for Aqueous Zn Batteries: A Combined Theoretical and Experimental Study

AbstractA new reactive force field based on quantum mechanical data for describing formation of the Zn electrode‐electrolyte interface (EEI) chemistry in aqueous zinc‐ion batteries (ZIBs) is developed. This is the first demonstration in which Reactive Molecular Dynamics (RMD) simulation is used to follow the Zn reduction and anode structural evolution at the EEI. It is found that under axial pressure, Zn dendrite formation is inhibited. This is associated with accelerated ion transport and reduction while increasing preference towards horizontal (002) plane growth. Pressure‐induced desolvation of Zn ions within the electric double layer, which promotes faster reduction kinetics is observed. It is found that axial pressure stabilizes adatoms on the (002) plane by decreasing axial atom stress during nucleation and by increasing favorable lateral adatom diffusion, which reduces atomic scale dendrite formation. Finally, these are confirmed results by experimental characterization and electrochemical tests.

Disclosing the Interfacial Electrolyte Structure of Na-Insertion Electrode Materials: Origins of the Desolvation Phenomenon.

Among a variety of promising cathode materials for Na-ion batteries, polyanionic Na-insertion compounds are among the preferred choices due to known fast sodium transfer through the ion channels along their framework structures. The most interesting representatives are Na3V2(PO4)3 (NVP) and Na3V2(PO4)2F3 (NVPF), which display large Na+ diffusion coefficients (up to 10-9 m2 s-1 in NVP) and high voltage plateaux (up to 4.2 V for NVPF). While the diffusion in the solid material is well-known to be the rate-limiting step during charging, already being thoroughly discussed in the literature, interfacial transport of sodium ions from the liquid electrolyte toward the electrode was recently shown to be important due to complex ion desolvation effects at the surface. In order to fill the blanks in the description of the electrode/electrolyte interface in Na-ion batteries, we performed a molecular dynamics study of the local nanostructure of a series of carbonate-based sodium electrolytes at the NVP and the NVPF interfaces along with careful examination of the desolvation phenomenon. We show that the tightness of solvent packing at the electrode surface is a major factor determining the height of the free energy barrier associated with desolvation, which explains the differences between the NVP and the NVPF structures. To rationalize and emphasize the remarkable properties of this family of cathode materials, a complementary comparative analysis of the same electrolyte system at the carbon electrode interface was also performed.

Achieving stable zinc metal anodes by regulating ion transfer and desolvation behavior

Aqueous Zn ion batteries (AZIBs) are considered to be highly promising rechargeable secondary batteries. However, the growth of zinc dendrites and irreversible side reactions hinder its further application. In this paper, an artificial interfacial protective layer of phenol–formaldehyde resin (PF) was constructed to achieve high-performance zinc anode. There is a strong interaction between hydroxyl groups in PF and Zn ions. This interaction modulates the solvation sheath of Zn ions and promotes the desolvation of [Zn(H2O)6]2+, which reduces the side reactions induced by reactive H2O. Furthermore, the pore structure of PF provides ion-confinement effect to regulate the Zn ions flux, thus reducing the growth of dendrites caused by inhomogeneous deposition. Thus, the PF coating has the dual effect of fast desolvation and ion confinement, which is beneficial to the uniform Zn ions deposition and achieves highly stable zinc anodes. Consequently, the Zn@PF||MnO2 full cell can be stably cycled for 1500 cycles at 1.5 A/g and the capacity retention remains 82.4 %. This method provides a convenient and practical approach to tackle the problems of zinc anodes, and establishes the foundation for their further application.