Superior electroadhesion force with permittivity-engineered bilayer films using electrostatic simulation and machine learning approaches.

Electroadhesive forces are crucial in various applications, including grasping devices, electro-sticky boards, electrostatic levitation, and climbing robots. However, the design of electroadhesive devices relies on speculative or empirical error approaches. Therefore, we present a theoretical model comprising predictive coplanar electrodes and protective layers for analyzing the electrostatic fields between an object and electroadhesive device. The model considers the role of protective layer and the air gap between the electrode surface and the object. To exert a higher electroadhesive force, the higher permeability of the protective layer is required. However, a high permeability of the protective layer is hard to withstand high applied voltage. To overcome this, two materials with different permeabilities were employed as protective layers-a low-permeability inner layer and a high-permeability outer layer-to maintain a high voltage and generate a large electroadhesive force. Because a low-permeability inner layer material was selected, a more permeable outer layer material was considered. A theoretical analysis revealed complex relationships between various design parameters. The impact of key design parameters and working environments on the electroadhesion behavior was further investigated. This study reveals the fundamental principles of electroadhesion and proposes prospective methods to enhance the design of electroadhesive devices for various engineering applications.

Sustaining Surface Lithiophilicity of Ultrathin Li-Alloy Coating Layers on Current Collector for Zero-Excess Li-Metal Batteries.

Zero-excess Li-metal batteries (ZE-LMBs) have emerged as the ultimate battery platform, offering an exceptionally high energy density. However, the absence of Li-hosting materials results in uncontrolled dendritic Li deposition on the Cu current collector, leading to chronic loss of Li inventory and severe electrolyte decomposition, limiting its full utilization upon cycling. This study presents the application of ultrathin (≈50 nm) coatings comprising six metallic layers (Cu, Ag, Au, Pt, W, and Fe) on Cu substrates in order to provide insights into the design of Li-depositing current collectors for stable ZE-LMB operation. In contrast to non-alloy Cu, W, and Fe coatings, Ag, Au, and Pt coatings can enhance surface lithiophilicity, effectively suppressing Li dendrite growth, thereby improving Li reversibility. Considering the distinct Li-alloying behaviors, particularly solid-solution and/or intermetallic phase formation, Pt-coated Cu current collectors maintain surface lithiophilicity over repeated Li plating/stripping cycles by preserving the original coating layer, thereby attaining better cycling performance of ZE-LMBs. This highlights the importance of selecting suitable Li-alloy metals to sustain surface lithiophilicity throughout cycling to regulate dendrite-less Li plating and improve the electrochemical stability of ZE-LMBs.

Diagnosis of Current Flow Patterns Inside Fault-Simulated Li-Ion Batteries via Non-Invasive, In Operando Magnetic Field Imaging.

With the growing popularity of Li-ion batteries in large-scale applications, building a safer battery has become a common goal of the battery community. Although the small errors inside the cells trigger catastrophic failures, tracing them and distinguishing cell failure modes without knowledge of cell anatomy can be challenging using conventional methods. In this study, a real-time, non-invasive magnetic field imaging (MFI) analysis that can signal the battery current-induced magnetic field and visualize the current flow within Li-ion cells is developed. A high-speed, spatially resolved MFI scan is used to derive the current distribution pattern from cells with different tab positions at a current load. Current maps are collected to determine possible cell failures using fault-simulated batteries that intentionally possess manufacturing faults such as lead-tab connection failures, electrode misalignment, and stacking faults (electrode folding). A modified MFI analysis exploiting the magnetic field interference with the countercurrent-carrying plate enables the direct identification of defect spots where abnormal current flow occurs within the pouch cells.

Enhanced Cycling Performance of a Li-Excess Li2CuO2 Cathode Additive by Cosubstitution Nanoarchitectonics of Ni and Mn for Lithium-Ion Batteries.

The adoption of Li2CuO2 has drawn interest as a Li-excess cathode additive for compensating irreversible Li+ loss in anodes during cycling, which would move forward high-energy-density lithium-ion batteries (LIBs). Li2CuO2 provides a high irreversible capacity (>200 mAh g-1) in the first cycle and an operating voltage comparable with commercial cathode materials, but its practical use is still restricted by the structural instability and spontaneous oxygen (O2) evolution, resulting in poor overall cycling performance. It is thus crucial to reinforce the structure of Li2CuO2 to make it more reliable as a cathode additive for charge compensation. Pursuing the structural stability of Li2CuO2, herein, we demonstrate cosubstitution by heteroatoms, such as nickel (Ni) and manganese (Mn), for improving the structural stability and electrochemical performance of Li2CuO2. Such an approach effectively enhances the reversibility of Li2CuO2 by suppressing continuous structural degradation and O2 gas evolution during cycling. Our findings provide new conceptual pathways for developing advanced cathode additives for high-energy LIBs.

One-Dimensional Porous Li-Confinable Hosts for High-Rate and Stable Li-Metal Batteries.

Li-confinable core-shell hosts have been extensively studied because they mitigate Li dendrite growth and volume change by reducing the effective current density and storing Li inside the core space during consecutive cycling. However, despite these fascinating features, these hosts suffer from unwanted Li growth on their surface (i.e., top plating) due to the carbon shell hindering Li-ion movement especially at higher current densities and capacities, resulting in poor electrochemical performance. In this study, we propose a one-dimensional porous Li-confinable host with lithiophilic Au (Au@PHCF), which is synthesized by a scalable dual-nozzle electrospinning. Because of the well-interconnected conductive networks forming three-dimensional structure, porous shell design enabling facile Li-ion transport, and hollow core space with lithiophilic Au storing metallic Li, the Au@PHCF can suppress the Li top plating and improve the Li stripping/plating efficiency compared to their counterparts even at 5 mA cm-2, eventually achieving stable cycling performances of the LiFePO4 full cell and Au@PHCF-Li symmetric cell for over 1000 and 2000 cycles, respectively. Finite element analysis reveals that the structural merit and lithiophilicity of Au enable fast reversible Li operation at the designated core space of the Au@PHCF, implying that the structural design of the Li-confinable host is crucial for the stable operation of promising Li-metal batteries at a practical test level.

Surface Stabilization of Ni-Rich Layered Cathode Materials via Surface Engineering with LiTaO3 for Lithium-Ion Batteries.

Recently, Ni-rich layered cathode materials have become the most common material used for lithium-ion batteries. From a structural viewpoint, it is crucial to stabilize the surface structures of such materials, as they are prone to undesirable side reactions and particle cracking in which intergranular microcracks form at the particle surfaces and then propagate inside. As a simplified engineering technique for obtaining Ni-rich cathode materials with high reversibility and long-term cycling stability, we propose a facile surface coating of piezoelectric LiTaO3 onto a Ni-rich cathode material to enhance the charge transfer reaction and surface structural integrity. Based on theoretical and experimental investigation, we demonstrate that this surface protection approach is effective at enhancing the reversibility and mechanical strength of Ni-rich cathode materials, leading to a stable cycle performance at up to 150 cycles, even at 60 °C. Furthermore, the piezoelectric characteristics of the surface LiTaO3 can enhance the rate capability of Ni-rich cathode materials at current densities of up to 2.0C. The results of this study provide a practical insight on the development of Ni-rich cathode materials for practical use in electric vehicle applications.

Strategic Approaches to the Dendritic Growth and Interfacial Reaction of Lithium Metal Anode.

Utilization of lithium (Li) metal anode is highly desirable for achieving high energy density batteries. Even so, the unavoidable features of Li dendritic growth and inactive Li are still the main factors that hinder its practical application. During plating and stripping, the solid electrolyte interphase (SEI) layer can provide passivation, playing an important role in preventing direct contact between the electrolyte and the electrode in Li metal batteries. Because of complexities of the electrolyte chemical and electrochemical reactions, the various formation mechanisms for the SEI are still not well understood. What we do know is that a strategic artificial SEI achieved through additives electrolyte can suppress the Li dendrites. Otherwise, the dendrites keep generating an abundance of irreversible Li, resulting in severe capacity loss, internal short-circuiting, and cell failure. In this minireview, we focus on the phenomenon of dendritic Li-growth and provide a brief overview of SEI formation. We finally provide some clear insights and perspectives toward practical application of Li metal batteries.

A cooperative biphasic MoOx-MoPx promoter enables a fast-charging lithium-ion battery.

The realisation of fast-charging lithium-ion batteries with long cycle lifetimes is hindered by the uncontrollable plating of metallic Li on the graphite anode during high-rate charging. Here we report that surface engineering of graphite with a cooperative biphasic MoOx-MoPx promoter improves the charging rate and suppresses Li plating without compromising energy density. We design and synthesise MoOx-MoPx/graphite via controllable and scalable surface engineering, i.e., the deposition of a MoOx nanolayer on the graphite surface, followed by vapour-induced partial phase transformation of MoOx to MoPx. A variety of analytical studies combined with thermodynamic calculations demonstrate that MoOx effectively mitigates the formation of resistive films on the graphite surface, while MoPx hosts Li+ at relatively high potentials via a fast intercalation reaction and plays a dominant role in lowering the Li+ adsorption energy. The MoOx-MoPx/graphite anode exhibits a fast-charging capability (<10 min charging for 80% of the capacity) and stable cycling performance without any signs of Li plating over 300 cycles when coupled with a LiNi0.6Co0.2Mn0.2O2 cathode. Thus, the developed approach paves the way to the design of advanced anode materials for fast-charging Li-ion batteries.

Everlasting Living and Breathing Gyroid 3D Network in Si@SiOx/C Nanoarchitecture for Lithium Ion Battery.

Silicon-based materials are the most promising candidates to surpass the capacity limitation of conventional graphite anode for lithium ion batteries. Unfortunately, Si-based materials suffer from poor cycling performance and dimensional instability induced by the large volume changes during cycling. To resolve such problems, nanostructured silicon-based materials with delicately controlled microstructure and interfaces have been intensively investigated. Nevertheless, they still face problems related to their high synthetic cost and their limited electrochemical properties and thermal stability. To overcome these drawbacks, we demonstrate the strategic design and synthesis of a gyroid three-dimensional network in a Si@SiOx/C nanoarchitecture (3D-Si@SiOx/C) with synergetic interaction between the computational prediction and the synthetic optimization. This 3D-Si@SiOx/C exhibits not only excellent electrochemical performance due to its structural stability and superior ion/electron transport but also enhanced thermal stability due to the presence of carbon, which was formed by a cost-effective one-pot synthetic route. We believe that our rationally designed 3D-Si@SiOx/C will lead to the development of anode materials for the next-generation lithium ion batteries.

Anisotropic Compositional Expansion and Chemical Potential of Lithiated SiO2 Electrodes: Multiscale Mechanical Analysis.

The use of high-capacity electrode materials (i.e., Si) in Li-ion batteries is hindered by their mechanical degradation. Thus, oxides (i.e., SiO2) are commonly used to obtain high expected capacities and long-term cycle performances. Despite extensive studies of the electrochemical-mechanical behaviors of high-capacity energy storage materials, the mechanical behaviors of amorphous SiO2 during electrochemical reaction remain largely unknown. Here, we systematically investigate the stress evolution, electronic structure, and mechanical deformation of lithiated SiO2 through first-principles computation and the finite element method. The structural and thermodynamic role of O in the amorphous Li-O-Si system is reported and compared with that in Si. Strong Si-O bonds in SiO2 show high mechanical strength and brittle behavior, but as Li is inserted, the Li-rich SiO2 phases become mechanically softened. The relaxation kinetics of SiO2, inducing deviatoric inelastic strains under mechanical constraints, is also compared with that of Si. The finite element model including the kinetic model for anisotropic expansion demonstrates that the long-term cycling stability of core-shell Si-SiO2 nanoparticles mainly arises from the reaction kinetics and high mechanical strength of SiO2. These results provide fundamental insights into the chemomechanical behavior of SiO2 for practical use.

Mechanochemically Reduced SiO2 by Ti Incorporation as Lithium Storage Materials.

This study presents a simple and effective method of reducing amorphous silica (a-SiO2 ) with Ti metal through high-energy mechanical milling for improving its reactivity when used as an anode material in lithium-ion batteries. Through thermodynamic calculations, it is determined that Ti metal can easily take oxygen atoms from a-SiO2 by forming a thermodynamically stable SiO2-x /TiOx composite, meaning that electrochemically inactive a-SiO2 is partially reduced by the addition of Ti metal powder during milling. This mechanically reduced SiO2-x /TiOx composite anode exhibits a greatly improved electrochemical reactivity, with a reversible capacity of more than 700 mAh g(-1) and excellent cycle performance over 100 cycles. Furthermore, an enhancement in the mechanical and thermal stability of the composite during cycling can be mainly attributed to the in situ formation of the SiO2-x /TiOx phase. These findings provide new insight into the rational design of robust, high-capacity, Si-based anode materials, as well as their reaction mechanism.