Optimizing Interplanar Spacing, Oxygen Vacancies and Micromorphology via Lithium-Ion Pre-Insertion into Ammonium Vanadate Nanosheets for Advanced Cathodes in Aqueous Zinc-Ion Batteries

Ammonium vanadates, featuring an N─H···O hydrogen bond network structure between NH4 + and V─O layers, have become popular cathode materials for aqueous zinc-ion batteries (AZIBs). Their appeal lies in their multi-electron transfer, high specific capacity, and facile synthesis. However, a major drawback arises as Zn2+ ions tend to form bonds with electronegative oxygen atoms between V─O layers during cycling, leading to irreversible structural collapse. Herein, Li+ pre-insertion into the intermediate layer of NH4 V4 O10 is proposed to enhance the electrochemical activity of ammonium vanadate cathodes for AZIBs, which extends the interlayer distance of NH4 V4 O10 to 9.8 Å and offers large interlaminar channels for Zn2+ (de)intercalation. Moreover, Li+ intercalation weakens the crystallinity, transforms the micromorphology from non-nanostructured strips to ultrathin nanosheets, and increases the level of oxygen defects, thus exposing more active sites for ion and electron transport, facilitating electrolyte penetration, and improving electrochemical kinetics of electrode. In addition, the introduction of Li+ significantly reduces the bandgap by 0.18 eV, enhancing electron transfer in redox reactions. Leveraging these unique advantages, the Li+ pre-intercalated NH4 V4 O10 cathode exhibits a high reversible capacity of 486.1 mAh g-1 at 0.5 A g-1 and an impressive capacity retention rate of 72% after 5,000 cycles at 5 A g-1 .

Highly Selective Transport and Enrichment of Lithium Ions through Bionic Ion Pair Receptor Nanochannels

Inspired by ion pair cotransport channels in biological systems, a bionic nanochannel modified with lithium ion pair receptors is constructed for selective transport and enrichment of lithium ions (Li⁺). NH₂-pillar[5]arene (NP5) is chosen as ion pair receptors, and the theoretical simulation and NMR titration experiments illustrate that NP5 has good affinity for the ion pair of LiCl through a strong host-guest interaction at the molecular level. Due to the confinement effect and ion pair cooperation recognition, an NP5-based receptor was introduced into an artificial PET nanochannel. An I-V test indicated that the NP5 channel realized the highly selective recognition for Li⁺. Meanwhile, transmembrane transport and COMSOL simulation experiments proved that the NP5 channel achieved the transport and enrichment of Li⁺ through the cooperative interaction between NP5 and LiCl. Moreover, the receptor solution of transmembrane transport LiCl in the NP5 channel was used to cultivate wheat seedlings, which obviously promoted their growth. This nanochannel based on the ion pair recognition will be much useful for practical applications like metal ion extraction, enrichment, and recycle.

Lithium Pyrene Squarate Covalent Organic Frameworks for Efficient Lithium and Magnesium Separation from Salt Water

The increasing pressure for lithium resources from the electric vehicle and nuclear energy industries means that new technologies to separate Mg²⁺ from Li⁺ from salt water are in demand. To address this need, we fabricated lithium pyrene squarate covalent organic frameworks (Li-SQCOFs) to separate Mg²⁺/Li⁺ mixtures from salt water. We optimized the effect of the electrolyte and the amount of the adsorbent and then carried out a kinetics study on the adsorbent recovery at various pH levels using both batch and continuous flow adsorption methods. Li-SQCOF was found to have excellent selectivity for solutions containing a mixture of Mg²⁺/Li⁺ ions. This work represents a unique path for the separation of Mg²⁺/Li⁺ through direct adsorption using a covalent organic framework (COF). The COF-supported ultrafiltration bed made in this study gave a Mg²⁺ separation flux of 60.5 h^-1 m^-2.

The Integration of Biopolymer-Based Materials for Energy Storage Applications: A Review

Biopolymers are an emerging class of novel materials with diverse applications and properties such as superior sustainability and tunability. Here, applications of biopolymers are described in the context of energy storage devices, namely lithium-based batteries, zinc-based batteries, and capacitors. Current demand for energy storage technologies calls for improved energy density, preserved performance overtime, and more sustainable end-of-life behavior. Lithium-based and zinc-based batteries often face anode corrosion from processes such as dendrite formation. Capacitors typically struggle with achieving functional energy density caused by an inability to efficiently charge and discharge. Both classes of energy storage need to be packaged with sustainable materials due to their potential leakages of toxic metals. In this review paper, recent progress in energy applications is described for biocompatible polymers such as silk, keratin, collagen, chitosan, cellulose, and agarose. Fabrication techniques are described for various components of the battery/capacitors including the electrode, electrolyte, and separators with biopolymers. Of these methods, incorporating the porosity found within various biopolymers is commonly used to maximize ion transport in the electrolyte and prevent dendrite formations in lithium-based, zinc-based batteries, and capacitors. Overall, integrating biopolymers in energy storage solutions poses a promising alternative that can theoretically match traditional energy sources while eliminating harmful consequences to the environment.

Spinel LiMn2O4 as a Capacitive Deionization Electrode Material with High Desalination Capacity: Experiment and Simulation

Capacitive deionization (CDI) is a newly developed desalination technology with low energy consumption and environmental friendliness. The surface area restricts the desalination capacities of traditional carbon-based CDI electrodes while battery materials emerge as CDI electrodes with high performances due to the larger electrochemical capacities, but suffer limited production of materials. LiMn₂O₄ is a massively-produced lithium-ion battery material with a stable spinel structure and a high theoretical specific capacity of 148 mAh·g^-1, revealing a promising candidate for CDI electrode. Herein, we employed spinel LiMn₂O₄ as the cathode and activated carbon as the anode in the CDI cell with an anion exchange membrane to limit the movement of cations, thus, the lithium ions released from LiMn₂O₄ would attract the chloride ions and trigger the desalination process of the other side of the membrane. An ultrahigh deionization capacity of 159.49 mg·g^-1 was obtained at 1.0 V with an initial salinity of 20 mM. The desalination capacity of the CDI cell at 1.0 V with 10 mM initial NaCl concentration was 91.04 mg·g^-1, higher than that of the system with only carbon electrodes with and without the ion exchange membrane (39.88 mg·g^-1 and 7.84 mg·g^-1, respectively). In addition, the desalination results and mechanisms were further verified with the simulation of COMSOL Multiphysics.

Robust 2D MoS2 Artificial Synapse Device Based on a Lithium Silicate Solid Electrolyte for High-Precision Analogue Neuromorphic Computing

High-precision artificial synaptic devices compatible with existing CMOS technology are essential for realizing robust neuromorphic hardware systems with reliable parallel analogue computation beyond the von Neumann serial digital computing architecture. However, critical issues related to reliability and variability, such as nonlinearity and asymmetric weight updates, have been great challenges in the implementation of artificial synaptic devices in practical neuromorphic hardware systems. Herein, a robust three-terminal two-dimensional (2D) MoS₂ artificial synaptic device combined with a lithium silicate (LSO) solid-state electrolyte thin film is proposed. The rationally designed synaptic device exhibits excellent linearity and symmetry upon electrical potentiation and depression, benefiting from the reversible intercalation of Li ions into the MoS₂ channel. In particular, extremely low cycle-to-cycle variations (3.01%) during long-term potentiation and depression processes over 500 pulses are achieved, causing statistical analogue discrete states. Thus, a high classification accuracy of 96.77% (close to the software baseline of 98%) is demonstrated in the Modified National Institute of Standards and Technology (MNIST) simulations. These results provide a future perspective for robust synaptic device architecture of lithium solid-state electrolytes stacked with 2D van der Waals layered channels for high-precision analogue neuromorphic computing systems.

Pressure-Engineered Ti3C2Tx MXene with Enhanced Conductivity and Accelerated Reaction Kinetics of Lithium Storage

We studied the structure-function relationship of compressed Ti₃C₂T_x MXene using high-pressure in situ synchrotron radiation, impedance spectroscopy, Hall effect measurements, and first-principles calculations. With increasing pressure, the conductivity of Ti₃C₂T_x MXene increases along with its continued lattice shrinkage. A pressure range of 0.4-2.2 GPa exhibits a sharp decrease in resistance, which decreases by more than one order of magnitude from 3.3 × 10⁴ to 1.4 × 10³ Ω. A pressure range of 2.2-6.6 GPa exhibits a steady resistance with a slight decrease of 0.2%. As the pressure drops to atmospheric conditions, the resistance increases slightly to 4.2 × 10³ Ω. This is accompanied by a transformation of the semiconductor into metal. An irreversible increase in conductivity is observed owing to an increase in the electron concentration and a decrease in the grain-boundary potential barrier. Furthermore, abundant Ti₃C₂T_x undergoing prepressure treatments (0.4, 2.0, and 4.0 GPa) was first prepared using a double-anvil hydraulic press. The recycled samples retain an accordion-like layered structure with slight lattice shrinkage while the voids between the sheets contract considerably, increasing the density. Correspondingly, electrochemical results show a pressure threshold of 2.0 GPa based on the rapid quenching from the hydraulic press. This weakens the electric polarization in redox reactions and increases the ionic transport rate for the formation of a Ti₃C₂T_x anode owing to pressure improving the conductivity and interlaminar densification. Our study shows a new, simple, and universal way to regulate various MXenes and also promotes the application of MXene-based materials in energy storage and related fields.

Three-Dimensional Monolithically Self-Grown Metal Oxide Highly Dense Nanonetworks as Free-Standing High-Capacity Anodes for Lithium-Ion Batteries

Transition metal oxides (TMOs) have been widely studied as potential next-generation anode materials, owing to their high theoretical gravimetric capacity. However, to date, these anodes syntheses are plagued with time-consuming preparation processes, two-dimensional electrode fabrication, binder requirements, and short operational cycling lives. Here, we present a scalable single-step reagentless process for the synthesis of highly dense Mn₃O₄-based nanonetwork anodes based on a simple thermal treatment transformation of low-grade steel substrates. The monolithic solid-state chemical self-transformation of the steel substrate results in a highly dense forest of Mn₃O₄ nanowires, which transforms the electrochemically inactive steel substrate into an electrochemically highly active anode. The proposed method, beyond greatly improving the current TMO performance, surpasses state-of-the-art commercial silicon anodes in terms of capacity and stability. The three-dimensional self-standing anode exhibits remarkably high capacities (>1500 mA h/g), a stable cycle life (>650 cycles), high Coulombic efficiencies (>99.5%), fast rate performance (>1.5 C), and high areal capacities (>2.5 mA h/cm²). This novel experimental paradigm acts as a milestone for next-generation anode materials in lithium-ion batteries, and pioneers a universal method to transform different kinds of widely available, low-cost, steel substrates into electrochemically active, free-standing anodes and allows for the massive reduction of anode production complexity and costs.

Improved diffusion and storage of lithium ions via recrystallization induced conducting pathways in a Li:Ta2O5-based electrolyte for all-solid-state electrochromic devices with enhanced performance

In this study, we have investigated the improvements in the performance of an all-solid-state complementary electrochromic device (ECD) by using the proposed high pressure treatment (HPT). The Li:Ta₂O₅electrolyte layer was recrystallized by the HPT utilizing pressurized CO₂gas (∼200 atm) and at low temperature (<60 °C), which enhanced the coloration performance of the WO₃/Li:Ta₂O₅/NiO complementary ECD by ∼20%. The reliability and durability of the ECD were confirmed by long term transmittance retention measurements, which indicated an improvement in the coloration performance by ∼14% upon the release of the bias voltages. The ability of the devices that were fabricated with and without the HPT process to withstand high temperature environments was also verified. In addition, photoluminescence (PL) and transmittance measurements were carried out to examine the effects of the bonding between WO₃and NiO. To determine the differences in lithium-ion (Li⁺) injection, electrical measurements were performed by utilizing varying pulse rising speeds to confirm device characteristics. The materials were characterized in terms of their composition and structure using high-resolution transmission electron microscopy along with energy-dispersive x-ray spectroscopy. Finally, a mechanistic model has been proposed to explain the improved EC characteristics based on the amorphous to crystalline transition accompanying the HPT process.

Dynamic Color Tuning with Electrochemically Actuated TiO2 Metasurfaces

Dynamic tuning of metamaterials is a critical step toward advanced functionality and improved bandwidth. In the visible spectrum, full spectral color tuning is inhibited by the large absorption that accompanies index changes, particularly at blue wavelengths. Here, we show that the electrochemical lithiation of anatase TiO₂ to Li_0.5TiO₂ (LTO) results in an index change of 0.65 at 649 nm with absorption coefficient less than 0.1 at blue wavelengths, making this material well-suited for dynamic visible color tuning. Dynamic tunability of TiO₂ is leveraged in a Fabry-Perot cavity and a gap plasmon metasurface. In the Fabry-Perot configuration, the device exhibits a shift in reflectance of over 100 nm when subjected to only 2 V bias while the gap plasmon metasurface achieves enhanced switching speed. The dynamic range, speed, and cyclability indicate that the TiO₂/LTO system is competitive with established actuators like WO₃, with the additional advantage of reduced absorption at high frequencies.

Development and Progression of Polymer Electrolytes for Batteries: Influence of Structure and Chemistry

Polymer electrolytes continue to offer the opportunity for safer, high-performing next-generation battery technology. The benefits of a polymeric electrolyte system lie in its ease of processing and flexibility, while ion transport and mechanical strength have been highlighted for improvement. This report discusses how factors, specifically the chemistry and structure of the polymers, have driven the progression of these materials from the early days of PEO. The introduction of ionic polymers has led to advances in ionic conductivity while the use of block copolymers has also increased the mechanical properties and provided more flexibility in solid polymer electrolyte development. The combination of these two, ionic block copolymer materials, are still in their early stages but offer exciting possibilities for the future of this field.

Design of phosphoryl containing podands with Li+/Na+ selectivity using machine learning

In this work we demonstrated, that machine learning opens a way for real design of ligands with required metal ion selectivity. We performed the ensemble QSPR modelling of the Li⁺/Na⁺ complexation selectivity and the stability constants for the Li⁺L and Na⁺L complexes of phosphoryl podands in nonaqueous solvent THF/СНCl₃ (4:1 v/v). The models were built and cross-validated using MLR with the ISIDA QSPR program and SVM with the libSVM package. The program SVMsmf was implemented to fulfil an ensemble modelling using libSVM and the Substructural Molecular Fragments (SMF) descriptors. SMF were used as descriptors for the ensemble modelling, properties predictions by consensus models and design of combinatorial library of new ligands. SMF such as the P=O group, the ether and P=O groups bound through the aromatic ring contribute significantly to the Li⁺/Na⁺ selectivity. The developed models were applied for the prediction of the studied properties for a focused virtual library of 3057 phosphoryl podands generated using SMF contributions promising for selective binding of lithium. Consensus models selected hits for a synthesis by combinatorial library screening. Among the constructed selective ligands - hits, three new podands were synthesized, for which the experimentally estimated selectivity is in satisfactory agreement with that predicted.

Proton and Li-Ion Permeation through Graphene with Eight-Atom-Ring Defects

Defect-free graphene is impermeable to gases and liquids but highly permeable to thermal protons. Atomic-scale defects such as vacancies, grain boundaries, and Stone-Wales defects are predicted to enhance graphene's proton permeability and may even allow small ions through, whereas larger species such as gas molecules should remain blocked. These expectations have so far remained untested in experiment. Here, we show that atomically thin carbon films with a high density of atomic-scale defects continue blocking all molecular transport, but their proton permeability becomes ∼1000 times higher than that of defect-free graphene. Lithium ions can also permeate through such disordered graphene. The enhanced proton and ion permeability is attributed to a high density of eight-carbon-atom rings. The latter pose approximately twice lower energy barriers for incoming protons compared to that of the six-atom rings of graphene and a relatively low barrier of ∼0.6 eV for Li ions. Our findings suggest that disordered graphene could be of interest as membranes and protective barriers in various Li-ion and hydrogen technologies.

Paper-Based Device for the Facile Colorimetric Determination of Lithium Ions in Human Whole Blood

Lithium carbonate is an effective medicine for the treatment of the bipolar disorder, but the concentration of lithium in the patient's blood must be frequently monitored because of its toxicity. To date, no colorimetric methods of lithium ion detection in whole blood without pretreatment have been reported. Here, we report a colorimetric paper-based device that allows point-of-care testing in one step. This device is composed of two paper-based elements linked to each other: a blood cell separation unit and a colorimetric detection unit. After a portion of whole blood has been placed on the end of the separation unit, plasma in the sample is automatically transported to the detection unit, which displays a diagnostic color. The key feature of this device is its simple, user-friendly operation. The limit of detection is 0.054 mM and the coefficient of variance is below 6.1%, which are comparable to those of conventional instruments using the same colorimetric reaction. Furthermore, we achieved high recovery (>90%) and reproducibility (<9.8%) with spiked human blood samples. Thus, the presented device provides an alternative method for the regular monitoring of lithium concentrations in the treatment of bipolar disorder by augmenting the coefficient of variation (maximum value, 6.1%).

There Is a Future for N-Heterocyclic Carbene Iron(II) Dyes in Dye-Sensitized Solar Cells: Improving Performance through Changes in the Electrolyte

By systematic tuning of the components of the electrolyte, the performances of dye-sensitized solar cells (DSCs) with an N-heterocyclic carbene iron(II) dye have been significantly improved. The beneficial effects of an increased Li+ ion concentration in the electrolyte lead to photoconversion efficiencies (PCEs) up to 0.66% for fully masked cells (representing 11.8% relative to 100% set for N719) and an external quantum efficiency maximum (EQEmax) up to approximately 25% due to an increased short-circuit current density (JSC). A study of the effects of varying the length of the alkyl chain in 1-alkyl-3-methylimidazolium iodide ionic liquids (ILs) shows that a longer chain results in an increase in JSC with an overall efficiency up to 0.61% (10.9% relative to N719 set at 100%) on going from n-methyl to n-butyl chain, although an n-hexyl chain leads to no further gain in PCE. The results of electrochemical impedance spectroscopy (EIS) support the trends in JSC and open-circuit voltage (VOC) parameters. A change in the counterion from I- to [BF4]- for 1-propyl-3-methylimidazolium iodide ionic liquid leads to DSCs with a remarkably high JSC value for an N-heterocyclic carbene iron(II) dye of 4.90 mA cm-2, but a low VOC of 244 mV. Our investigations have shown that an increased concentration of Li+ in combination with an optimized alkyl chain length in the 1-alkyl-3-methylimidazolium iodide IL in the electrolyte leads to iron(II)-sensitized DSC performances comparable with those of containing some copper(I)-based dyes.

Copper Silicide Nanowires as Hosts for Amorphous Si Deposition as a Route to Produce High Capacity Lithium-Ion Battery Anodes

Herein, copper silicide (Cu₁₅Si₄) nanowires (NWs) grown in high densities from a metallic Cu substrate are utilized as nanostructured hosts for amorphous silicon (aSi) deposition. The conductive Cu₁₅Si₄ NW scaffolds offer an increased surface area, versus planar substrates, and enable the preparation of high capacity Li-ion anodes consisting of a nanostructured active material. The formation method involves a two-step process, where Cu₁₅Si₄ nanowires are synthesized from a Cu substrate via a solvent vapor growth (SVG) approach followed by the plasma-enhanced chemical vapor deposition (PECVD) of aSi. These binder-free anodes are investigated in half-cell (versus Li-foil) and full-cell (versus LCO) configurations with discharge capacities greater than 2000 mAh/g retained after 200 cycles (half-cell) and reversible capacities of 1870 mAh/g exhibited after 100 cycles (full-cell). A noteworthy rate capability is also attained where capacities of up to 1367 mAh/g and 1520 mAh/g are exhibited at 5C in half-cell and full-cell configurations, respectively, highlighting the active material's promise for fast charging and high power applications. The anode material is characterized prior to cycling and after 1, 25, and 100 charge/discharge cycles, by scanning electron microscopy (SEM) and transmission electron microscopy (TEM), to track the effects of cycling on the material.

Blueprint and Implementation of Rural Stand-Alone Power Grids with Second-Life Lithium Ion Vehicle Traction Battery Systems for Resilient Energy Supply of Tropical or Remote Regions

Developed societies with advanced economic performance are undoubtedly coupled with the availability of electrical energy. Whilst industrialized nations already started to decrease associated carbon emissions in many business sectors, e.g., by substituting combustion engines with battery-powered vehicles, less developed countries still lack broad coverage of reliable electricity supply, particularly in rural regions. Progressive electrification leads to a need for storage capacity and thus to increasing availability of advanced battery systems. To achieve a high degree of sustainability, re-used batteries from the electromobility sector are appropriate, as they do not consume further primary resources and still have sufficient residual capacity for stationary electrical storage applications. In this article, a blueprint for the electrification of a remote region by utilizing second-life lithium ion traction batteries for an integrated energy system in a stand-alone grid is presented and the implementation by the example case of a Tanzanian island in Lake Victoria is demonstrated. First, economic potentials and expected trends in the disposability of second-life lithium ion batteries and their foreseeable costs are outlined. Subsequently, key decision variables are identified to evaluate logistic aspects and the feasibility of the implementation of an off-grid electrical system in remote areas for economically and geographically unfavorable environments. The practical realization is pictured in detail with a focus on technical performance and safety specificities associated with second-life applications. Therefore, a new type of battery management system is introduced, which meets the special requirements of climate compatibility, low maintenance, enhanced cell balancing capability and cell configuration flexibility, and combined with a fiber-optical sensor system, provides reliable status monitoring of the battery. By carrying out on-site measurements, the overall system efficiency is evaluated along with a sustainability analysis. Finally, the socioeconomic and humanitarian impact for the people on the island is debated.

The Role of Zr Doping in Stabilizing Li[Ni0.6 Co0.2 Mn0.2 ]O2 as a Cathode Material for Lithium-Ion Batteries

Ni-rich layered LiNi_1-x-y Co_x Mn_y O₂ systems are the most promising cathode materials for high energy density Li-ion batteries (LIBs). However, Ni-rich cathode materials inevitably suffer from rapid capacity fading and poor rate capability owing to structural instability and unstable surface side reactions. Zr doping has proven to be an effective method to enhance the cycle and rate performances by stabilizing the structure and increasing the Li⁺ diffusion rate. Herein, effects of Zr-doping on the structural stability and Li⁺ diffusion kinetics are thoroughly investigated in LiNi_0.6 Co_0.2 Mn_0.2 O₂ (LNCM) cathode material using atomic-resolution scanning transmission electron microscopy imaging, XRD Rietveld refinement, and density functional theory calculations. Zr doping mitigates the degree of cation mixing, decreases the structural transformation, and facilitates Li⁺ diffusion resulting in improved cyclic performance and rate capability. Based on the obtained results, an atomistic model is proposed to explain the effects of Zr doping on the structural stability and Li⁺ diffusion kinetics in LNCM cathode materials.

Interaction in Li@Fullerenes and Li+@Fullerenes: First Principle Insights to Li-Based Endohedral Fullerenes

This work reveals first principle results of the endohedral fullerenes made from neutral or charged single atomic lithium (Li or Li⁺) encapsulated in fullerenes with various cage sizes. According to the calculated binding energies, it is found that the encapsulation of a single lithium atom is energetically more favorable than that of lithium cation. Lithium, in both atomic and cationic forms, exhibits a clear tendency to depart from the center in large cages. Interaction effects dominate the whole encapsulation process of lithium to carbon cages. Further, the nature of the interaction between Li (or Li⁺) and carbon cages is discussed based on reduced density gradient, energy decomposition analysis, and charge transfer.

Structure, Dynamics, and Adsorption of Charged Guest within the Nanocavity of Polymer-Functionalized Neutral Macrocyclic Host

Host-guest encapsulation has been widely applied for purification and seizing of the metal ions. Macrocyclic crown ethers are one of the most popular hosts in the field of host-guest chemistry, which on functionalization with polymers are employed as an effective adsorbent. In spite of their vast applications, the microscopic information about their sensing mechanism toward cations/molecules is very scarce. Therefore, the present study is focused on the molecular insights of ion-exchange mechanism within the cavity of crown ether-functionalized polymers using molecular dynamics (MD) simulations. This present study investigates the molecular-level events of chloromethylated polystyrene (CMPS) bearing dibenzo-18-crown-6 (DB18C6) in the aqueous and acidic environment, which has been found to be particularly successful in sensing of various alkali and alkali earth metal ions. A strategy has been envisaged to design a crown ether-based functionalized polymeric resin, which exhibits good match of properties with the in-house-synthesized resin. The MD studies well capture the experimentally observed Langmuir-type adsorption isotherms of Li⁺ ions on crown ether-grafted polymer resins. The presence of acid reduces the adsorption of Li⁺ ions due to the competition with H₃O⁺ ions. In addition, the results revealed that the "adsorption in crown cavity" follows a dual residence time function. To the best of our knowledge, this is the first report on the adsorption isotherm of functionalized crown ether using MD simulations. The structure and dynamics of binding sites were explored using radial distribution functions and diffusion coefficients. All of these effects have been studied for different Li⁺-ion concentrations, acid concentrations, and counterions as well as different lengths of polymer chains and degrees of polymerization. Overall, the present study provides insights into and quantitative information about adsorption on the CMPS-DB18C6 resin, which might be useful in myriads of host-guest-based adsorption experiments.

V2O5/Graphene Hybrid Supported on Paper Current Collectors for Flexible Ultrahigh-Capacity Electrodes for Lithium-Ion Batteries

An ultrahigh-capacity, flexible electrode made with vanadium pentoxide/graphene (with a specific capacity of 396 mAh/g) supported on paper-based current collectors has been developed. The ultrahigh-capacity graphene-modified vanadium pentoxide is fabricated by incorporating graphene sheets (2 wt %) into the vanadium pentoxide nanorods to improve the specific capacity, cycle life, and rate capability. This active material is then incorporated with the paper-based current collectors [carbon nanotube (CNT)-microfiber paper] to provide flexible electrodes. The flexible current collector has been made by depositing single-wall CNTs over wood microfibers through a layer-by-layer self-assembly process. The CNT mass loading of the fabricated current collectors is limited to 10.1 μg/cm². The developed electrodes can be used to construct the flexible battery cells, providing a high-capacity/energy and rechargeable energy storage unit for flexible electronic devices.

Simultaneous Perforation and Doping of Si Nanoparticles for Lithium-Ion Battery Anode

Silicon nanostructures have served as promising building blocks for various applications, such as lithium-ion batteries, thermoelectrics, and solar energy conversions. Particularly, control of porosity and doping is critical for fine-tuning the mechanical, optical, and electrical properties of these silicon nanostructures. However, perforation and doping are usually separated processes, both of which are complicated and expensive. Here, we demonstrate that the porous nano-Si particles with controllable dopant can be massively produced through a facile and scalable method, combining ball-milling and acid-etching. Nano-Si with porosity as high as 45.8% can be achieved with 9 orders of magnitude of conductivity changes compared to intrinsic silicon. As an example for demonstration, the obtained nano-Si particles with 45.8% porosity and 3.7 atom % doping can serve as a promising anode for lithium-ion batteries with 2000 mA h/g retained over 100 cycles at the current density of 0.5 C, excellent rate performance with 1600 mA h/g at the current density of 5 C, and a stable cycling performance of above 1500 mA h/g retained over 940 cycles at the current density of 1 C with carbon coating.

Enhancing Multifunctionalities of Transition-Metal Dichalcogenide Monolayers via Cation Intercalation

We have demonstrated that multiple functionalities of transition-metal dichalcogenide (TMDC) monolayers may be substantially improved by the intercalation of small cations (H⁺ or Li⁺) between the monolayers and underlying substrates. The functionalities include photoluminescence (PL) efficiency and catalytic activity. The improvement in PL efficiency may be up to orders of magnitude and can be mainly ascribed to two effects of the intercalated cations: p-doping to the monolayers and reducing the influence of substrates, but more studies are necessary to better understand the mechanism for the improvement in the catalytic functionality. The cation intercalation may be achieved by simply immersing substrate-supported monolayers into the solution of certain acids or salts. It is more difficult to intercalate under the monolayers interacting with substrates stronger, such as as-grown monolayers or the monolayers on 2D material substrates. This result presents a versatile strategy to simultaneously optimize multiple functionalities of TMDC monolayers.

Lithium-Ion Insertion Properties of Solution-Exfoliated Germanane

The high theoretical energy density of alloyed lithium and germanium (Li₁₅Ge₄), 1384 mAh/g, makes germanium a promising anode material for lithium-ion batteries. However, common alloy anode architectures suffer from long-term instability upon repetitive charge-discharge cycles that arise from stress-induced degradation upon lithiation (volume expansion >300%). Here, we explore the use of the two-dimensional nanosheet structure of germanane to mitigate stress from high volume expansion and present a facile method for producing stable single-to-multisheet dispersions of pure germanane. Purity and degree of exfoliation were assessed with scanning electron microscopy, transmission electron microscopy, and Raman spectroscopy. We measured representative germanane battery electrodes to have a reversible Li-ion capacity of 1108 mAh/g when cycled between 0.1 and 2 V vs Li/Li⁺. These results indicate germanane anodes are capable of near-theoretical-maximum energy storage, perform well at high cycling rates, and can maintain capacity over 100 cycles.

Electrolyte Volume Effects on Electrochemical Performance and Solid Electrolyte Interphase in Si-Graphite/NMC Lithium-Ion Pouch Cells

This study aims to explore the correlations between electrolyte volume, electrochemical performance, and properties of the solid electrolyte interphase in pouch cells with Si-graphite composite anodes. The electrolyte is 1.2 M LiPF₆ in ethylene carbonate:ethylmethyl carbonate with 10 wt % fluoroethylene carbonate. Single layer pouch cells (100 mA h) were constructed with 15 wt % Si-graphite/LiNi_0.5Mn_0.3CO_0.2O₂ electrodes. It is found that a minimum electrolyte volume factor of 3.1 times to the total pore volume of cell components (cathode, anode, and separator) is needed for better cycling stability. Less electrolyte causes increases in ohmic and charge transfer resistances. Lithium dendrites are observed when the electrolyte volume factor is low. The resistances from the anodes become significant as the cells are discharged. Solid electrolyte interphase thickness grows as the electrolyte volume factor increases and is nonuniform after cycling.

Investigating the Mechanism of Reversible Lithium Insertion into Anti-NASICON Fe2(WO4)3

The gram-scale preparation of Fe₂(WO₄)₃ by a new solution-based route and detailed characterization of the material are presented. The resulting Fe₂(WO₄)₃ undergoes a reversible electrochemical reaction against lithium centered around 3.0 V with capacities near 93% of the theoretical maximum. Evolution of the Fe₂(WO₄)₃ structure upon lithium insertion and deinsertion is probed using a battery of characterization techniques, including in situ X-ray diffraction, neutron total scattering, and X-ray absorption spectroscopy (XAS). A structural transformation from monoclinic to orthorhombic phases is confirmed during lithium intercalation. XAS and neutron total scattering measurements verify that Fe₂(WO₄)₃ consists of trivalent iron and hexavalent tungsten ions. As lithium ions are inserted into the framework, iron ions are reduced to the divalent state, while the tungsten ions are electrochemically inactive and remain in the hexavalent state. Lithium insertion occurs via a concerted rotation of the rigid polyhedra in the host lattice driven by electrostatic interactions with the Li⁺ ions; the magnitude of these polyhedral rotations was found to be slightly larger for Fe₂(WO₄)₃ than for the Fe₂(MoO₄)₃ analog.

Gallium-Doped Li7La3Zr2O12 Garnet-Type Electrolytes with High Lithium-Ion Conductivity

Owing to their high conductivity, crystalline Li_7-3xGa_xLa₃Zr₂O₁₂ garnets are promising electrolytes for all-solid-state lithium-ion batteries. Herein, the influence of Ga doping on the phase, lithium-ion distribution, and conductivity of Li_7-3xGa_xLa₃Zr₂O₁₂ garnets is investigated, with the determined concentration and mobility of lithium ions shedding light on the origin of the high conductivity of Li_7-3xGa_xLa₃Zr₂O₁₂. When the Ga concentration exceeds 0.20 Ga per formula unit, the garnet-type material is found to assume a cubic structure, but lower Ga concentrations result in the coexistence of cubic and tetragonal phases. Most lithium within Li_7-3xGa_xLa₃Zr₂O₁₂ is found to reside at the octahedral 96h site, away from the central octahedral 48g site, while the remaining lithium resides at the tetrahedral 24d site. Such kind of lithium distribution leads to high lithium-ion mobility, which is the origin of the high conductivity; the highest lithium-ion conductivity of 1.46 mS/cm at 25 °C is found to be achieved for Li_7-3xGa_xLa₃Zr₂O₁₂ at x = 0.25. Additionally, there are two lithium-ion migration pathways in the Li_7-3xGa_xLa₃Zr₂O₁₂ garnets: 96h-96h and 24d-96h-24d, but the lithium ions transporting through the 96h-96h pathway determine the overall conductivity.

Novel Conjugated Ladder-Structured Oligomer Anode with High Lithium Storage and Long Cycling Capability

Herein we report the development of nanostructured poly(1,4-dihydro-11H-pyrazino[2',3':3,4]cyclopenta[1,2-b]quinoxalin-11-one) (PPCQ), a novel conjugated ladderlike oligomer with the presence of a rich amount of heteroatoms, as the anode material. Beyond its remarkable lithium storage of 972 mAh g(-1) after 120 cycles, the superior cycle life and stable capacity performance of 489 mAh g(-1) revealed by ultralong testing of 1000 cycles (with an average Coulombic efficiency 99.8%) at a high current density of 2.5 A g(-1) indicate its excellent electrochemical stability to be promisingly applied for high-performance lithium-ion batteries (LIBs).

Role of Manganese Deposition on Graphite in the Capacity Fading of Lithium Ion Batteries

Lithium ion batteries utilizing manganese-based cathodes have received considerable interest in recent years for their lower cost and more favorable environmental friendliness relative to their cobalt counterparts. However, Li ion batteries using these cathodes combined with graphite anodes suffer from severe capacity fading at high operating temperatures. In this paper, we report on how the dissolution of manganese impacts the capacity fading within the Li ion batteries. Our investigation reveals that the manganese dissolves from the cathode, transports to the graphite electrode, and deposits onto the outer surface of the innermost solid-electrolyte interphase layer, which is known to be a mixture of inorganic salts (e.g., Li2CO3, LiF, and Li2O). In this location, the manganese facilitates the reduction of the electrolyte and the subsequent formation of lithium-containing products on the graphite, which removes lithium ions from the normal operation of the cell and thereby induces the severe capacity fade.

Enhanced Lithiation Cycle Stability of ALD-Coated Confined a-Si Microstructures Determined Using In Situ AFM

Microfabricated amorphous silicon (a-Si) pits ∼4 μm in diameter and 100 nm thick were fabricated to be partially confined in a nickel (Ni) current collector. Corresponding unconfined pillars were also fabricated. The samples were coated with 1.5, 3, or 6 nm of Al2O3 ALD. These samples were tested in electrolytes of 3:7 by weight ethylene carbonate:ethyl methyl carbonate (EC:EMC) with 1.2 M LiPF6 salt with and without 2% fluoroethylene carbonate (FEC) and in a pure FEC electrolyte with 10 wt % LiPF6. The samples were imaged with an atomic force microscope during electrochemical cycling to evaluate morphology evolution and solid electrolyte interphase (SEI) formation. The partially confined a-Si structures had superior cycle efficiency relative to the unconfined a-Si pillars. Additionally, samples with 3 nm of ALD achieved higher charge capacity and enhanced cycle life compared to samples without ALD, demonstrated thinner SEI formation, and after 10 cycles at a 1 C rate remained mostly intact and had actually decreased in diameter. Finally, the samples with 3 nm of ALD had better capacity retention in the baseline 3:7 EC:EMC than in either of the FEC containing electrolytes.

Preferential Solvation of Lithium Cations and Impacts on Oxygen Reduction in Lithium-Air Batteries

The solvation of Li+ with 11 nonaqueous solvents commonly used as electrolytes for lithium batteries was studied. The solvation preferences of different solvents were compared by means of electrospray mass spectrometry and collision-induced dissociation. The relative strength of the solvent for the solvation of Li+ was determined. The Lewis acidity of the solvated Li+ cations was determined by the preferential solvation of the solvent in the solvation shell. The kinetics of the catalytic disproportionation of the O2•- depends on the relative Lewis acidity of the solvated Li+ ion. The impact of the solvated Li+ cation on the O2 redox reaction was also investigated.

Uniquely arranged graphene-on-graphene structure as a binder-free anode for high-performance lithium-ion batteries

3D graphene interconnected frameworks homogeneously connected with a few-layer graphene film (3DG/FLG) constitute a novel hierarchical hybrid structure for anodes in lithium-ion batteries. The pore-rich 3D graphene network is favorable for Li(+) diffusion and electron transport, and the FLG is a non-metallic current collector that effectively collects/transports charge carriers from/to the 3D graphene network and provides an excellent scaffold to support the 3DG.

Control of Carbon Nanotube Electronic Properties by Lithium Cation Intercalation

We show that the electronic properties of single walled carbon nanotubes (SWCNTs) can be tuned continuously from semiconducting to metallic by varying the location of ions inside the tubes. Focusing on the Li(+) cation inside the (26,0) zigzag semiconducting and (15,15) armchair metallic SWCNTs, we found that the Li(+)-SWCNT interaction is attractive. The interaction is stronger for the metallic SWCNT, indicating in particular that metallic tubes can enhance performance of lithium-ion batteries. The electronic properties of the metallic SWCNT are virtually independent of the presence of ions: Li(+) creates an energy level in the valence band slightly below the Fermi energy. On the contrary, the semiconducting SWCNT can be made metallic by placing ions close to the tube axis: Li(+) generates a new bottom of the conduction band. Letting the ions approach SWCNT walls recovers the semiconducting behavior.