Search

A physics-based model of lithium-ion batteries (LIBs) has been developed to predict the decline in their performance accurately. The model considers both electrochemical and mechanical factors. During charge and discharge cycles, the solid electrolyte interphase (SEI) layer thickens, leading to increased resistance, higher overvoltage, more lithium deposition, dendrite growth, and reduced discharge capacity. Additionally, graphite expands during lithium insertion and contracts during extraction, causing mechanical stress and cracks. These cracks expose more surface area for SEI growth, intensifying lithium loss. The model also considers the loss of active material within the electrodes, which further reduces discharge capacity. This comprehensive LIB degradation model provides valuable insights for optimizing battery design and improving performance. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

The low-temperature operation of lithium-ion batteries (LIBs) is a challenge in achieving high-stability battery technology. Moreover, the design and analysis of low-temperature electrolytes are impeded by the limited understanding of various solvent components and their combinations. In this study, we present a data-driven strategy to design electrolytes with high ionic conductivity at low temperature using various machine-learning algorithms, such as random forest and feedforward neural networks. To establish a link between prediction of electrolyte chemistry and cell performance of LIBs, we performed parameter-free molecular dynamics (MD) prediction of various salt concentrations and temperatures for target solvents. Finally, electrochemical modeling was performed using these properties as the required material parameters. Combining works of the fully parameterized Newman models, parameter-free MD, and data-driven prediction of electrolyte chemistry can help measure the discharge voltage of batteries and enable in silico engineering of electrolyte development for realizing low-temperature operation of LIBs. [ABSTRACT FROM AUTHOR]

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. Fast-charging of lithium-ion batteries is hindered by the uncontrollable plating of metallic Li on the graphite anode during cycling. Here, the authors demonstrate the fast chargeability and long cycle lifetimes via surface engineering of graphite with a cooperative biphasic MoOx–MoPx promoter. [ABSTRACT FROM AUTHOR]

Silicon (Si) is one of the most promising anodes for next-generation lithium (Li)-ion batteries because of its high capacity. However, the commercial uses of Si anodes are hindered by extremely poor cycling stability caused by huge volume expansion during charging and discharging processes as well as by a change in material properties according to Li concentration. Given these reasons, we propose the multiscale analysis of Si nanowire anode using a diffusion-induced stress model with Li concentration effects, such as softening of mechanical modulus and enhancement of Li diffusion. From the geometry context, the diffusion-induced stress model exhibits stress relaxation during the lithiation and optimal condition of the Si nanowire. We then construct an approximated stress criteria equation for the safe operation of Si nanowire of various sizes and shapes. Our multiscale analysis predicts the various types of Si nanowire, including holecaped Si nanowires, which are beneficial to mechanical stability. This study provides insights into the physics of Li-Si compound behaviors and introduces the possibility of developing Si-based anodes with mechanical stability. [ABSTRACT FROM AUTHOR]

An investigation of Li-M (M: Si, Sn) components using density functional theory (DFT) is presented. Calculation of total energy, structural optimizations, bulk modulus and elastic constants with Li-Sn, Li-Si are performed through DFT calculations. From the comparable study of Li-Sn and Li-Si, it is found that silicon experience drastic mechanical degradation during lithiation than tin-based Li-Sn components. With increasing lithium net charge transfer to metals, the filling of anti-bonding orbital makes M-M covalent bonding weak ionic bonding in both Li-Si and Li-Sn. However, the difference of change of mechanical degradation during lithiation in Li-Si and Li-Sn results from the sensitivity of transition of covalent bonding. We check this from sharp decreasing of yield stress in Li-Si case. Furthermore, we simply make up amorphous Si cell with an additional Li atom at the center of the largest void to simulate the lithiation of amorphous silicon. Volume expansion of amorphous silicon cell agrees with the experiment observation and theoretical data of Li-Si compounds. [ABSTRACT FROM AUTHOR]