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P2-type layered Na 0.67 MnO 2 has been considered to be a promising candidate cathode material for sodium ion batteries. Nevertheless, the undesired phase transitions during operation and the large Na + radius induced sluggish ion diffusion remain the stumbling blocks to realize its high performance. Herein, we propose a Zn/Mg co-doping strategy, which is proved to have bifunctional effects. First, relative to the pristine P2-Na 0.67 MnO 2 and the single-ion (Zn/Mg) doped samples, the Zn/Mg dual-doped P2-Na 0.67 MnO 2 demonstrates a lower Mn 3+ /Mn 4+ ratio and a higher lattice O content, which facilitate the structural stability of the cathode material. More intriguingly, the Zn/Mg co-doping gives rise to enlarged interplanar spacing, which provides spacious ion diffusion channels for fast Na + intercalation/extraction. As a result, the Zn/Mg dual-doped sample exhibits a high Na + diffusion coefficient and a solid-solution reaction during charge/discharge, with a cell volume change determined to be only 0.55%. Taking advantages of the above favorable features, the Zn/Mg dual-doped P2-Na 0.67 MnO 2 demonstrates a high rate performance with 67.2 mAh·g −1 delivered at 10 C and a decent cycling stability with a capacity retention of 93.8% achieved at 1 C after 100 cycles. This work introduces the Zn/Mg co-doping strategy to simultaneously improve the cycling stability and rate capability of P2-Na 0.67 MnO 2 , which may offer a promising avenue for further performance enhancement of the layered Na-ion batteries cathode materials.

Conversion/alloying anode materials exhibiting high K storage capacities suffer from large volume variations and unstable electrode/electrolyte interfaces upon cycling. Herein, taking SnS/reduced graphene oxide (SnS/rGO) anodes as an example, the electrochemical performance of SnS/rGO could significantly be improved via employing potassium bis(fluorosulfonyl)imide (KFSI) salt in electrolytes and ultrathin TiO 2 coating. KF-rich inorganic layer was demonstrated to help form robust SEI layer, which could suppress the side reactions to increase the Coulombic efficiency. The formed potassiated K x TiO 2 coating layer was constructed to boost charge transfer capability and K-ion diffusion kinetics. The as-prepared SnS/rGO@TiO 2 -20 electrode in KFSI electrolyte delivers the high CE of 99.1% and 424 mAh·g −1 after 200 cycles with an ultrahigh capacity retention of 98.5%.

LiFePO4 (LFP) has undergone extensive research and is a promising cathode material for Li-ion batteries. The high interest is due to its low raw material cost, good electrochemical stability, and high-capacity retention. However, poor electronic conductivity and a low Li+ diffusion rate decrease its electrochemical reactivity, especially at fast charge/discharge rates. In this work, the volumetric energy density of lithium-ion batteries is successfully increased by using different amounts of conductive carbon (Super P) in the active material content. The particle size and morphology of the electrode material samples are studied using field emission scanning electron microscopy and dynamic light scattering. Two-point-probe DC measurements and adhesive force tests are used to determine the conductivity and evaluate adhesion for the positive electrode. Cyclic voltammetry, electrochemical impedance spectroscopy (EIS), and charge/discharge tests are used to analyze the electrochemical properties of the battery. The samples containing 88% LFP, 5.5% Super P, and 6.5% PVDF perform best, with discharge capacities reaching 169.8 mAh g−1 at 0.1 C, and they can also manage charging/discharging of 5 C. EIS indicates that this combination produces the lowest charge-transfer impedance (67 Ω) and the highest Li+ ion diffusion coefficient (5.76 × 10−14 cm2 s−1).

Hydrotalcite, known as layered double hydroxides (LDHs), is a new type of admixture used to delay the corrosion of reinforcement. The aim of this study was to investigate the chloride ion diffusion behavior of C30 concrete with varying amounts of calcined hydrotalcite (0%, 2%, 4% and 6%) in a chloride salt environment. The NT-Build 443 test was adopted to characterize the one-dimensional accelerated chloride ion penetration of concrete. The distribution of chloride ion concentration in hydrotalcite concrete with different mix proportions immersed in sodium chloride solution for 30 days and 60 days was determined, and the chloride ion diffusion coefficient and surface chloride ion concentration were fitted based on Fick’s second law to establish the chloride ion diffusion model considering the influence of multiple factors. This model was validated using COMSOL Multiphysics finite element software. The results show that concrete mixed with LDHs can meet its compressive strength requirements and that the resistance of concrete with 2% calcined hydrotalcite to chloride ion penetration is the best with a 19.6% increase in the 30-day chloride ion penetration coefficient. The chloride ion diffusion process under chloride salt immersion conditions is in accordance with Fick’s second law. The chloride ion concentrations calculated with COMSOL software and the test results are in good agreement, which verifies the reliability of the chloride ion diffusion model.

The physiochemical nature of reactive metal electrodeposits during the early stages of electrodeposition is rarely studied but known to play an important role in determining the electrochemical stability and reversibility of electrochemical cells that utilize reactive metals as anodes. We investigated the early-stage growth dynamics and reversibility of electrodeposited lithium in liquid electrolytes infused with brominated additives. On the basis of equilibrium theories, we hypothesize that by regulating the surface energetics and surface ion/adatom transport characteristics of the interphases formed on Li, Br-rich electrolytes alter the morphology of early-stage Li electrodeposits; enabling late-stage control of growth and high electrode reversibility. A combination of scanning electron microscopy (SEM), image analysis, X-ray photoelectron spectroscopy (XPS), electrochemical impedance spectroscopy (EIS), and contact angle goniometry are employed to evaluate this hypothesis by examining the physical–chemical features of the material phases formed on Li. We report that it is possible to achieve fine control of the early-stage Li electrodeposit morphology through tuning of surface energetic and ion diffusion properties of interphases formed on Li. This control is shown further to translate to better control of Li electrodeposit morphology and high electrochemical reversibility during deep cycling of the Li metal anode. Our results show that understanding and eliminating morphological and chemical instabilities in the initial stages of Li electroplating via deliberately modifying energetics of the solid electrolyte interphase (SEI) is a feasible approach in realization of deeply cyclable reactive metal batteries.

HighlightsA new and compact device configuration was created with two interpenetrated, individually addressable electrodes, allowing precise control over the geometric features and interactions between the electrodes.The interpenetrated electrode design improves ion diffusion kinetics in electrochemical energy storage devices by shortening the ion diffusion length and reducing ion concentration inhomogeneity.The device with interpenetrated electrodes outperformed the traditional separate electrode configuration, enhancing both volumetric energy density and capacity retention rate.The architectural design of electrodes offers new opportunities for next-generation electrochemical energy storage devices (EESDs) by increasing surface area, thickness, and active materials mass loading while maintaining good ion diffusion through optimized electrode tortuosity. However, conventional thick electrodes increase ion diffusion length and cause larger ion concentration gradients, limiting reaction kinetics. We demonstrate a strategy for building interpenetrated structures that shortens ion diffusion length and reduces ion concentration inhomogeneity. This free-standing device structure also avoids short-circuiting without needing a separator. The feature size and number of interpenetrated units can be adjusted during printing to balance surface area and ion diffusion. Starting with a 3D-printed interpenetrated polymer substrate, we metallize it to make it conductive. This substrate has two individually addressable electrodes, allowing selective electrodeposition of energy storage materials. Using a Zn//MnO2 battery as a model system, the interpenetrated device outperforms conventional separate electrode configurations, improving volumetric energy density by 221% and exhibiting a higher capacity retention rate of 49% compared to 35% at temperatures from 20 to 0 °C. Our study introduces a new EESD architecture applicable to Li-ion, Na-ion batteries, supercapacitors, etc.

The Qinghai–Tibet Plateau features a high-altitude, cold, and arid climate, with harsh environmental conditions. It is also one of the regions in China where chloride-rich salt lakes are abundant. These circumstances pose significant challenges to the durability of concrete. This study explored the impact of recycled fine powders (RFP) on the resistance of concrete to chloride ion erosion. To evaluate this, a 3.5% sodium chloride solution and Qarhan Salt Lake brine were employed as erosion media. The depth and concentration of chloride ion penetration, the free chloride ion diffusion coefficient (Df), and the microstructure of the concrete were measured. The results demonstrated that when the replacement rate of RFP was 20%, the concrete displayed excellent resistance to chloride ion erosion in both the sodium chloride solution and the Salt Lake brine. XRD analysis and SEM images revealed that the addition of RFP enabled the concrete to bind more Cl− to form Friedel’s salt, which filled the pores of the concrete and reduced the diffusion of Cl− within the concrete. Moreover, as the soaking time extended continuously, the erosion and damage effects of the Salt Lake brine solution on the concrete were more severe than those of the sodium chloride solution.

This study investigates Li-ion diffusion characteristics in Li-contained and Li-free bismuth oxide crystals, aiming to explore their potential as solid electrolytes for next-generation lithium-ion batteries. Although bismuth oxide has been widely applied as a solid electrolyte in fuel cells, its suitability for Li-ion battery applications remains unexplored. Using molecular dynamics simulations, we analyzed the Li-ion diffusion behavior in two distinct Li-contained bismuth oxide crystals with layered and non-layered structures, as well as four Li-free bismuth oxide phases. It is demonstrated that the layered structure exhibits a simpler and more organized diffusion pathway compared to the complex and bottlenecked pathways in the non-layered structure, resulting in superior Li-ion diffusivity. For Li-free bismuth oxide phases, diffusion coefficients vary significantly depending on structural characteristics, with the highest diffusion coefficient observed in the phase with minimal void fraction. A notable inverse relationship between void fraction and Li-ion diffusivity efficiency highlights the importance of structural design in enhancing ionic transport. This study provides valuable insights into the diffusion mechanisms of Li ions in bismuth oxide systems and offers strategic guidance for designing high-performance solid electrolytes, contributing to the advancement of all-solid-state battery technologies.

This study was conducted to investigate the chloride ion transport in coral aggregate seawater concrete (CASC) with varying water–cement ratios under different loads. The ultimate compressive strength was obtained by conducting compression testing of three groups of CASC with different water–cement ratios. Steady loads of 0%, 10%, and 20% of their respective ultimate compressive strengths were applied to the concrete specimens with different water–cement ratios. After being subjected to a seawater erosion test for 30, 60, 90, 120, and 180 days, the chloride ion concentration at different depths was measured to determine the chloride ion diffusion coefficient. Meanwhile, the chloride ion diffusion coefficients of CASC were verified by comparing them with results obtained from numerical simulations performed using COMSOL software. The test results show that the internal pore space of CASC expands, leading to acceleration of the chloride ion transport rate when applied loads are increased. The initial chloride ion concentration of CASC rises as the water–cement ratio rises, and the concentration gradient formed with artificial seawater lowers, decreasing the chloride ion transport rate. When the water cement ratio decreases and the load increases, the diffusion coefficient increases. Using the numerical simulation method of COMSOL software, it was proved that the model has good applicability and accuracy in predicting chloride ion transport in CASC.

A highly polar perovskite SrTiO3 (STO) layer is considered as one of the promising artificial protective layers for the Zn metal anode of aqueous zinc-ion batteries (AZIBs). Although it has been reported that oxygen vacancies tend to promote Zn(II) ion migration in the STO layer and thereby effectively suppress Zn dendrite growth, there is still a lack of a basic understanding of the quantitative effects of oxygen vacancies on the diffusion characteristics of Zn(II) ions. In this regard, we comprehensively studied the structural features of charge imbalances caused by oxygen vacancies and how these charge imbalances affect the diffusion dynamics of Zn(II) ions by utilizing density functional theory and molecular dynamics simulations. It was found that the charge imbalances are typically localized close to vacancy sites and those Ti atoms that are closest to them, whereas differential charge densities close to Sr atoms are essentially non-existent. We also demonstrated that there is virtually no difference in structural stability between the different locations of oxygen vacancies by analyzing the electronic total energies of STO crystals with the different vacancy locations. As a result, although the structural aspects of charge distribution strongly rely on the relative vacancy locations within the STO crystal, Zn(II) diffusion characteristics stay almost consistent with changing vacancy locations. No preference for vacancy locations causes isotropic Zn(II) ion transport inside the STO layer, which subsequently inhibits the formation of Zn dendrites. Due to the promoted dynamics of Zn(II) ions induced by charge imbalance near the oxygen vacancies, the Zn(II) ion diffusivity in the STO layer monotonously increases with the increasing vacancy concentration ranging from 0% to 16%. However, the growth rate of Zn(II) ion diffusivity tends to slow down at relatively high vacancy concentrations as the imbalance points become saturated across the entire STO domain. The atomic-level understanding of the characteristics of Zn(II) ion diffusion demonstrated in this study is expected to contribute to developing new long-life anode systems for AZIBs.