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Although all‐solid‐state batteries are suggested as a means to tackle the safety concerns associated with current Li‐ion batteries, there is presently a lack of comprehensive understanding regarding their thermal safety. In this context, critical factors contributing to the thermal runaway of thiophosphate solid electrolytes with charged Li1‐xNi0.8Co0.1Mn0.1O2 (NCM) under thermal and mechanical abuse conditions are demonstrated, considering parameters such as heating rate under thermal abuse conditions and the hybridization of S atom in structure. In particular, the thermal behavior of various solid electrolytes, including thiophosphates, thioantimonates, and halides, is investigated to clarify critical elements in Li6PS5Cl (LPSCl) contributing to its thermal instability when combined with charged NCM. Various ex situ analyses, along with density functional theory calculations, reveal a correlation between the hybridization of S atoms and the thermal instability of solid electrolytes, suggesting that sulfur acts as a key element triggering the thermal runaway of sulfide‐based solid electrolytes. [ABSTRACT FROM AUTHOR]

In this study, microwave irradiation is employed for the phenolation of acid-insoluble Klason lignin. Microwave irradiation significantly reduces the reaction temperature (180 → 100 °C) and time (6 h → 10 min) without noticeable differences in the chemical structure of the phenolated lignin compared with the products prepared using a conventional heating method. As the reaction temperature increases (100 → 150 °C), lignin decomposition and crosslinking occur simultaneously, as did phenolation. Upon increasing the phenol-to-lignin ratio, the fragmentation of lignin is enhanced, while the crosslinking reaction is inhibited, leading to a decrease in the molecular weight and glass transition temperature of the phenolated lignin. Density functional theory is applied to elucidate the thermal and non-thermal effects of the electromagnetic field on the phenolation of Klason lignin. The solubility of Klason lignin in tetrahydrofuran and methanol is highly enhanced after phenolation, which allows for its adhesive application on glass, polyethylene naphthalate, and polyimide substrates. [ABSTRACT FROM AUTHOR]

Summary: Understanding the role of the oxygen content in silicon suboxides (SiOx) is important for the improvement of their performance as promising negative electrode materials for Li‐ion batteries. Furthermore, sufficient research has not been conducted on tailoring the oxidation of silicon suboxides to employ them as anodes. To address these limitations, we demonstrated the lithiation of SiO2 and amorphous SiOx up to four Li atoms per SiOx and performed density functional theory calculations to examine the energetics, structural evolution, charge effects, mechanical properties, and volume energy density of lithiated a‐SiOx. Our calculations show that two Li defects effectively break a Si‐O bond in SiO2 and a single Li defect is easily stabilized by oxygen in a‐SiOx. With lithiation, oxygen‐tailored SiOx exhibits a difference in volume change and in voltage profiles. The tradeoff between the decreasing volume change ratio and increasing potential as the O content increases results in varied volume energy densities. The detailed reduction mechanism of Li in the a‐SiOx system was analyzed by calculating the Bader charge. Our results emphasize the importance of tailoring the O content to obtain desired lithiation properties and give the physical insight of the development and rational design strategy of high‐performance SiOx anodes dependent on the oxidation conditions. [ABSTRACT FROM AUTHOR]

In this study, newly designed cathode material LiFeP 1-x Si x O 4 , with silicon mixed in LiFePO 4 is investigated using the density functional theory. Its most optimized structure is the olivine structure of the Pnma space group. Bonding length show the anti-site defect which hinders Li diffusivity is prevented in the LiFeP 1-x Si x O 4. Lithium migration energy barriers in the (010) path of LiFeP 1-x Si x O 4 (x = 0, 0.5, and 1) are calculated by using nudged elastic band calculations, and the average values are determined as 0.180, 0.245, and 0.280 eV for LiFePO 4 , LiFeP 0.5 Si 0.5 O 4 , and LiFeSiO 4 , respectively. This signifies that the Li ionic diffusivity is degraded thermodynamically, which is contrary to that indicates by the calculated bonding length, however, the difference is negligibly small. Furthermore, the intercalation voltage increases up to 4.97 V, depending on the Si ratio to P, and is much higher than that of the pristine cathode materials LiFePO 4 (∼3.47 V) enabling voltage optimization by Si substitution. The energy density is proportional to the intercalation voltage, hence the energy density is increased, respectively. Finally, the Total density of states show that the electronic conductivity of LiFeP 1-x Si x O 4 (x = 0–1) is better than that of LiFePO 4. • Novel cathode material LiFeP 1-x Si x O 4 is detail designed using ab-initio study. • Optimized LiFeP 1-x Si x O 4 crystal structure is olivine structure Pnma space group. • LiFeP 1-x Si x O 4 cathode material diminishes anti-site defect and enhances electronic conductivity. • LiFeP 1-x Si x O 4 cathode material overcome low intercalation voltage and control the voltage. • LiFeP 1-x Si x O 4 cathode material improves volumetric energy density. [ABSTRACT FROM AUTHOR]

In this study, we revealed the interfacial strengthening mechanism between a Stone- Thrower-Wales (STW) defective single layer graphene and polypropylene (PP), through a density functional theory (DFT) simulation and atomistic molecular dynamics simulations. In quantum mechanical simulation, the adhesion energy of propylene monomer on STW defective graphene is calculated with van der Waals interaction. An improved adsorption characteristic of propylene to the STW defective graphene is clearly observed, compared with a pristine counterpart. For deeper understanding of the adsorption, the electronic structure calculation and geometrical analysis of the adsorbed structures are also performed. In molecular dynamics simulation, three transversely isotropic nanocomposite unit cell structures consisting of PP and single layer graphene having a different number of STW defects are constructed. The stress-strain curves of nanocomposites according to the density of STW defects are obtained from uniaxial tension and shear tests. Since the properties of graphene itself are degraded by the STW defects, the overall stress-strain characteristics of nanocomposites involving the deformation of graphene are degraded by the addressed STW defects. However, in longitudinal shearing, where interfacial shearing between graphene and PP is involved, the STW defect can critically improve the shear load bearing capability. The increased interfacial shear load transfer is mostly attributed to the rippling of graphene at the STW defective sites, and the resultant surface roughness of graphene. [ABSTRACT FROM AUTHOR]

We study the piezoelectric behavior of metal-doped monolayer MoS 2. Its three-dimensional charge density, work function (WF), and piezoresponse with various metal dopants are theoretically predicted based on density functional theory, and the real-time piezoelectric power of these samples is experimentally verified. Selected p -type metal dopants (Au, Ag, Pd, Pt, and Al) increase the WF of monolayer MoS 2 , affecting electron emission from the MoS 2 surface. The reason is that p -type metal dopants suppress excess electrons and prevent screening effects. A nanogenerator constructed from Au-doped monolayer MoS 2 has been used to explore the possibility of a practical device. [Display omitted] [ABSTRACT FROM AUTHOR]

A diffusion induced stress (DIS) model based on the finite element method was used to analyze mechanical stress within a multiscale framework for silicon nanowire anodes designed for use in Li-ion batteries. With a prelithiated nanowire, the mechanical moduli of lithium silicide and the migration energy barriers of lithium were calculated by density functional theory method, while the diffusion constants for lithium silicide were obtained using kinetic Monte Carlo simulations. Unlike previous DIS analyses, this multiscale approach reveals a decreasing hoop stress with increasing lithium concentration. Furthermore, an increase in the diffusion coefficient with Li concentration was also found to be a much more significant factor than the reduction in the mechanical moduli, causing a prelithiated silicon anode to experience lower stress levels than pristine silicon. On the basis of this finding, it is concluded that prelithiation reduces the loss in cycling performance that typically occurs due largely to an excess of induced stress. [ABSTRACT FROM AUTHOR]

Energetics and kinetics of Li insertion into c-Si and a-Si systems are investigated using the density functional (DFT) theory calculations and kinetic Monte Carlo (KMC) simulations. DFT formation energies show the mechanism of phase separation between crystalline silicon and amorphous lithium silicide. Both crystalline and amorphous Si show similar trends in volume expansion and phase transition under lithiation, and kinetics of Li diffusion in bulk silicon (from DFT and KMC) shows a big difference between c-Si and a-Si. The Li migration barrier is 0.6 eV in c-Si, and quickly decreases to 0.4 eV under increasing Li concentration or Si volume expansion. To simulate Li diffusion in amorphous silicon using KMC, we have developed a formulation for environment dependent migration energy barriers of Li in a-Si using a volume dependent function. KMC simulations are performed for Li diffusion in both c-Si and a-Si, and the diffusion coefficient of Li in a-Si is an order of magnitude larger than in c-Si. These studies help to understand mechanisms of lithiation with atomic scale details and elucidate the phase separation between c-Si and lithium silicide. [ABSTRACT FROM AUTHOR]

[Display omitted] • A new fast Li-ion conductor with an organic framework is demonstrated. • Li-SPAF1 shows superior ion-conductivity of 0.102 mS cm−1 at room temperature. • DFT calculation proves the vacancy-mediated diffusion for Li-ion conduction. Solid polymer electrolytes (SPEs) have been received significant attention due to their inherent advantages of high safety and high electrochemical stability as fast Li-ion conductors. However, conventional SPEs of dual-ion conductors (i.e. , conducting both anions and cations) are prone to induce concentration polarization and thus decrease in ionic conductivities, which remains a significant hurdle for their practical applications. Here, we propose a new host of porous aromatic frameworks (PAFs) as a promising single Li-ion conducting SPEs. PAF1 is one of the promising types for crystalline polymers with the integration of aromatic organic building units into a 3-dimensional framework, having plenty of voids space inside. By covalently tethering the sulfonate on aromatic groups, anions are immobilized onto the frameworks, and the exchanging process of protons with Li-ions makes it perform as a fast Li-ionic conductor. Consequently, Li sulfonated PAF1 (denoted as Li-SPAF1) shows superior ion-conducting properties of 0.102 mS cm−1 at room temperature with the activation energy of 0.21 eV. It is demonstrated that the aromatic groups have high chemical and thermal stabilities, even stable with Li metal, which is advantageous for delivering stable electrochemical performances. Also, the structure and conduction mechanism are theoretically investigated by using density functional theory calculations. [ABSTRACT FROM AUTHOR]

[Display omitted] • Defect in graphene-silicon(d-Gr/Si) composites enhances electrochemical performance. • Li adsorption energies in the d-Gr/Si were less than -0.6 eV and 0.25 eV at pristine Gr/Si. • Defected Gr/Si is more thermionically stable than pristine Gr/Si. • Charge transfer on defects improves electrical conduction and mechanical strength at interfaces. • Our analyses elucidate that defect engineering enhances Li capacity and mechanical strength. Carbon-coated silicon materials are considered as promising anode materials in high-capacity lithium-ion batteries (LIBs). Theoretically, using graphene as the anode material in the LIB would afford high electrical conductivity, mechanical stability of Si, and suppression of the unstable solid–electrolyte interface. However, its usage is hindered by its electrochemical characteristic, which is not electrochemically active when combined with lithium. Therefore, research on graphene as the anode and coated material in LIBs has been conducted using defect engineering to enhance the storage capacity of graphene. Although the electrochemical characteristics of various defects in graphene have been studied experimentally and theoretically, graphene-based composite anode materials such as graphene–silicon composite electrodes have rarely been studied from the electrochemical and mechanical perspectives. In this study, lithium adsorptions are conducted on various defected graphene and graphene–silicon composites using density functional theory calculation. The formation energies of Li on the various defected graphene are assessed, and the mechanical strengths of the graphene–silicon composites are analyzed. Our calculations validate that the defects in graphene enhance the electrochemical adsorptions and interfacial mechanical strengths of the graphene and graphene–silicon composites. During lithiation, the defects mediate greater interfacial adhesion of the silicon–graphene composite. Hence, we elucidate that defected graphene increases the electro-chemo mechanical stabilities of silicon composites in high-capacity LIBs. [ABSTRACT FROM AUTHOR]

The true potential of Mg–S batteries is not yet realized despite its great advantages in material cost and safety. This is due to the lethargic reaction kinetics involved in the dissociation of Mg polysulfide (MgPS) on the cathode. Herein, we propose nitrogen–doped mesoporous carbon (N d MC) materials with suitable nitrogen content and surface moieties that can be utilized as catalytic hosts to enhance polysulfide fragmentation and electron access to the redox active sites in Mg–S batteries. In controlled N d MC, the surface nitrogen atoms located at the pyridinic positions can strongly bind MgPS and accelerate the reduction of MgPS to MgS, while the graphitic wall structure facilitates facile electron transport to the reaction sites. This synergic effect enables the composite electrode made of tuned N d MC and sulfur to exhibit an enhanced reversible capacity and good cycling capacity retention in Mg–S batteries. This study offers a new strategy for improving the performance of Mg–S batteries by fine-tuning the structural properties of the carbon hosts. [Display omitted] • N-doped graphitic mesoporous carbon is utilized as a host for S 8 imbibition. • Suitable surface moiety and wall structure of carbon host is proposed. • The pyridinic-N stronly binds MgPS and accelerates its dissociation. • Synergic effect enables an enhanced performance for Mg–S batteries. [ABSTRACT FROM AUTHOR]

[Display omitted] • Three types of bimetallic ZIFs with different zinc (Zn) to cobalt (Co) ratio were synthesized and carbonized. • Co nanocatalyst induced graphitization during pyrolysis. • The size of Co nanocatalyst affected the carbon nanotube growth. • Carbon nanotube dramatically improved the electrical conductivity. Carbon nanotubes are the most effective way to enhance electrical conductivity between particles, although the growth mechanism in zeolitic imidazolate frameworks still remains elusive. According to our density functional theory calculations and experimental studies, the role of cobalt nanoparticles as catalysts was proved to induce graphitization during pyrolysis. In particular, the sizes and exposed facets of the Co particles play an important role in triggering a hierarchical carbon nanotubes. This work paves the way to control the growth of carbon nanotubes toward various applications. [ABSTRACT FROM AUTHOR]