Molecular Reactivity and Interface Stability Modification in In-Situ Gel Electrolyte for High Performance Quasi-Solid-State Lithium Metal Batteries

Quasi-solid-state lithium metal battery is a promising candidate for next generation high energy density and high safety power supply.Despite intensive efforts on electrolytes,uncontrolled interfacial reactions on lithium with electrolyte and patchy interfacial contacts still hinder its practical process.Herein,we bring in rationally designed F contained groups into polymer skeleton via in-situ gelation for the first time to establish quasi-solid-state battery.This method achieves a capacity retention of 90%after 1000 cycles at 0.5C with LiFePO_(4)cathodes.The interface constructed by polymer skeleton and reaction with–CF_(3)lead to the predicted solid electrolyte interface species with high stability.Furthermore,we optimize molecular reactivity and interface stability with regulating F contained end groups in the polymer.Comparisons on different structures reveal that high performance solid stable lithium metal batteries rely on chemical modification as well as stable polymer skeleton,which is more critical to construct robust and steady SEI with uniform lithium deposition.New approach with functional groups regulation proposes a more stable cycling process with a capacity retention of 94.2%at 0.5C and 87.6%at 1C after 1000 cycles with LiFePO_(4) cathodes,providing new insights for the practical development of quasi-solid-state lithium metal battery.

Shock-induced energy localization and reaction growth considering chemical-inclusions effects for crystalline explosives

Chemical inclusions significantly alter shock responses of crystalline explosives in macroscale gap experiments but their microscale dynamics origin remains unclear.Herein shock-induced energy localization,overall physical responses,and reactions in a-1,3,5-trinitro-1,3,5-triazinane(a-RDX)crystal entrained various chemical inclusions were investigated by the multi-scale shock technique implemented in the reactive molecular dynamics method.Results indicated that energy localization and shock reaction were affected by the intrinsic factors within chemical inclusions,i.e.,phase states,chemical compositions,and concentrations.The atomic origin of chemical-inclusions effects on energy localization is dependent on the dynamics mechanism of interfacial molecules with free space volume,which includes homogeneous intermolecular compression,interfacial impact and shear,and void collapse and jet.As introducing various chemical inclusions,the initiation of those dynamics mechanisms triggers diverse decay rates of bulk RDX molecules and hereby impacts on growth speeds of final reactions.Adding chemical inclusions can reduce the effectiveness of the void during the shock impacting.Under the shockwave velocity of 9 km/s,the parent RDX decay rate in RDX entrained amorphous carbon decreases the most and is about one fourth of that in RDX with a vacuum void,and solid HMX and TATB inclusions are more reactive than amorphous carbon but less reactive than dry air or acetone inclusions.The lessdense shocking system denotes the greater increases in local temperature and stress,the faster energy liberation,and the earlier final reaction into equilibrium,revealing more pronounced responses to the present intense shockwave.The quantitative models associated with the relative system density(RD_(sys))were proposed for indicating energy-localization mechanisms and evaluating initiation safety in the shocked crystalline explosive.RD_(sys)is defined by the density ratio of defective RDX to perfect crystal after dynamics relaxation and reveals the global density characteristic in shocked systems filled with chemical inclusions.When RD_(sys)is below 0.9,local hydrodynamic jet initiated by void collapse dominates upon energy localization instead of interfacial impact.This study sheds light on novel insights for understanding the shock chemistry and physical-based atomic origin in crystalline explosives considering chemical-inclusions effects.

Quantitative prediction and ranking of the shock sensitivity ofexplosives via reactive molecular dynamics simulations

A deep understanding of explosive sensitivities and their factors is important for safe and reliable applications.However,quantitative prediction of the sensitivities is difficult.Here,reactive molecular dynamics simulation models for high-speed piston impacts on explosive supercells were established.Simulations were also performed to investigate shock-induced reactions of various high-energy explosives.The fraction of reacted explosive molecules in an initial supercell changed linearly with the propagation distance of the shock-wave front.The corresponding slope could be used as a reaction rate for a specific shock-loading velocity.Reaction rates that varied with the shock-loading pressure exhibited two-stage linearities with different slopes.The two inflection points corresponded to the initial and accelerated reactions,which respectively correlated to the thresholds of shock-induced ignition and detonation.Therefore,the ignition and detonation critical pressures could be determined.The sensitivity could then be a quantitative prediction of the critical pressure.The accuracies of the quantitative shock sensitivity predictions were verified by comparing the impact and shock sensitivities of common explosives and the characteristics of anisotropic shock-induced reactions.Molecular dynamics simulations quantitatively predict and rank shock sensitivities by using only crystal structures of the explosives.Overall,this method will enable the design and safe use of explosives.

The mechanism study of low-pressure air plasma cleaning on large-aperture optical surface unraveled by experiment and reactive molecular dynamics simulation

Low-pressure air plasma cleaning is an effective method for removing organic contaminants on large-aperture optical components in situ in the inertial confinement fusion facility.Chemical reactions play a significant role in plasma cleaning,which is a complex process involving abundant bond cleavage and species generation.In this work,experiments and reactive molecular dynamics simulations were carried out to unravel the reaction mechanism between the benchmark organic contaminants of dibutyl phthalate and air plasma.The optical emission spectroscopy was used to study the overall evolution behaviors of excited molecular species and radical signals from air plasma as a reference to simulations.Detailed reaction pathways were revealed and characterized,and specific intermediate radicals and products were analyzed during experiments and simulation.The reactive species in the air plasma,such as O,HO_(2)and O_(3)radicals,played a crucial role in cleaving organic molecular structures.Together,our findings provide an atomic-level understanding of complex reaction processes of low-pressure air plasma cleaning mechanisms and are essential for its application in industrial plasma cleaning.

Microscopic mechanism study and process optimization of dimethyl carbonate production coupled biomass chemical looping gasification system

Biomass chemical looping gasification technology is one of the essential ways to utilize abundant biomass resources.At the same time,dimethyl carbonate can replace phosgene as an environmentfriendly organic material for the synthesis of polycarbonate.In this paper,a novel system coupling biomass chemical looping gasification with dimethyl carbonate synthesis with methanol as an intermediate is designed through microscopic mechanism analysis and process optimization.Firstly,reactive force field molecular dynamics simulation is performed to explore the reaction mechanism of biomass chemical looping gasification to determine the optimal gasification temperature range.Secondly,steady-state simulations of the process based on molecular dynamics simulation results are carried out to investigate the effects of temperature,steam to biomass ratio,and oxygen carrier to biomass ratio on the syngas yield and compositions.In addition,the main energy indicators of biomass chemical looping gasification process including lower heating value and cold gas efficiency are analyzed based on the above optimum parameters.Then,two synthesis stages are simulated and optimized with the following results obtained:the optimal temperature and pressure of methanol synthesis stage are 150℃ and 4 MPa;the optimal temperature and pressure of dimethyl carbonate synthesis stage are 140℃ and 0.3 MPa.Finally,the pre-separation-extraction-decantation process separates the mixture of dimethyl carbonate and methanol generated in the synthesis stage with 99.11%purity of dimethyl carbonate.Above results verify the feasibility of producing dimethyl carbonate from the perspective of multi-scale simulation and realize the multi-level utilization of biomass resources.

Enhanced production of hydrogen via catalytic methane decomposition on a Pt_(7)-Ni(110)substrate:a reactive molecular dynamics investigation

Numerous researchers in the energy field are engaged in a competitive race to advance hydrogen as a clean and environmentally friendly fuel.Studies have been conducted on the different aspects of hydrogen,including its production,storage,transportation and utilization.The catalytic methane decomposition technique for hydrogen production is an environmentally friendly process that avoids generating carbon dioxide gas,which contributes to the greenhouse effect.Catalysts play a crucial role in facilitating rapid,cost-effective and efficient production of hydrogen using this technique.In this study,reactive molecular dynamics simulations were employed to examine the impact of Pt7 cluster decoration on the surface of a Ni(110)catalyst,referred to as Pt7-Ni(110),on the rates of methane dissociation and molecular hydrogen production.The reactive force field was employed to model the atomic interactions that enabled the formation and dissociation of chemical bonds.Our reactive molecular dynamics simulations using the Pt7-Ni(110)catalyst revealed a notable decrease in the number of methane molecules,specifically~11.89 molecules per picosecond.The rate was approximately four times higher than that of the simulation system utilizing a Ni(110)catalyst and approximately six times higher than that of the pure methane,no-catalyst system.The number of hydrogen molecules generated during a simulation period of 150000 fs was greater on the Pt7-Ni(110)surface than in both the Ni(110)and pure methane systems.This was due to the presence of numerous dissociated hydrogen atoms on the Pt7-Ni(110)surface.

Atomistic understanding of rough surface on the interfacial friction behavior during the chemical mechanical polishing process of diamond

The roughness of the contact surface exerts a vital role in rubbing.It is still a significant challenge to understand the microscopic contact of the rough surface at the atomic level.Herein,the rough surface with a special root mean square(RMS)value is constructed by multivariate Weierstrass–Mandelbrot(W–M)function and the rubbing process during that the chemical mechanical polishing(CMP)process of diamond is mimicked utilizing the reactive force field molecular dynamics(ReaxFF MD)simulation.It is found that the contact area A/A0 is positively related with the load,and the friction force F depends on the number of interfacial bridge bonds.Increasing the surface roughness will increase the friction force and friction coefficient.The model with low roughness and high lubrication has less friction force,and the presence of polishing liquid molecules can decrease the friction force and friction coefficient.The RMS value and the degree of damage show a functional relationship with the applied load and lubrication,i.e.,the RMS value decreases more under larger load and higher lubrication,and the diamond substrate occurs severer damage under larger load and lower lubrication.This work will generate fresh insight into the understanding of the microscopic contact of the rough surface at the atomic level.

Friction reactions induced by selective hydrogenation of textured surface under lubricant conditions

The passivation of hydrogen atoms and the conformation of textured surfaces under oil-lubricated conditions are effective strategies to obtain amorphous carbon(a-C)films with extremely low friction.It is critical to understanding the influence mechanism of selective surface hydrogenation on the tribological behaviors of textured a-C film under oil-lubricated conditions.In particular,the interactions of hydrogen atoms and lubricants are confusing,which is enslaved to the in situ characterization technique.The reactive molecular dynamics(RMD)simulations were conducted to analyze the friction response of textured a-C films with selective hydrogenation surfaces under oil-lubricated conditions.The results indicate that the existence of hydrogen atoms on specific bump sites significantly decreases the friction coefficient(μ)of textured a-C film,which is highly dependent on the surface hydrogen content.The repulsion between hydrogen atoms and lubricant molecules prompts the formation of a dense lubricant film on the surface of the mating material.Interestingly,with the enhancement of the surface hydrogen content,the passivation of the friction interface and the repulsion between hydrogen atoms and lubricants play dominant roles in reducing the friction coefficient instead of hydrodynamic lubrication.

Impact of lithium nitrate additives on the solid electrolyte interphase in lithium metal batteries

Lithium metal batteries(LMBs)represent a promising frontier in energy storage technology,offering high energy density but facing significant challenges.In this work,we address the critical challenge of lithium dendrite for-mation in LMBs,a key barrier to their efficiency and safety.Focusing on the potential of electrolyte additives,specifically lithium nitrate,to inhibit dendritic growth,we employ advanced multi-scale simulation techniques to explore the formation and properties of the solid electrolyte interphase(SEI)on the anode surface.Our study introduces a novel hybrid simulation methodology,HAIR(Hybrid ab initio and Reactive force field Molecular Dynamics),which combines ab initio molecular dynamics(AIMD)and reactive force field molecular dynamics(RMD).This approach allows for a more precise and reliable examination of the interaction mechanisms of nitrate additives within LMBs.Our findings demonstrate that lithium nitrate contributes to the formation of a stable and fast ionic conductor interface,effectively suppressing dendrite growth.These insights not only advance our un-derstanding of dendrite formation and mitigation strategies in lithium metal batteries,but also highlight the efficacy of HAIR as a pioneering tool for simulating complex chemical interactions in battery materials,offering significant implications for the broader field of energy storage technology.

Molecules with a TEMPO-based head group as high-performance organic friction modifiers

High-performance organic friction modifiers(OFMs)added to lubricating oils are crucial for reducing energy loss and carbon footprint.To establish a new class of OFMs,we measured the friction and wear properties of N-(2,2,6,6-tetramethyl-1-oxyl-4-piperidinyl)dodecaneamide referred to as C12Amide-TEMPO.The effect of its head group chemistry,which is characterized by a rigid six-membered ring sandwiched by an amide group and a terminal free oxygen radical,was also investigated with both experiments and quantum mechanical(QM)calculations.The measurement results show that C12Amide-TEMPO outperforms the conventional OFMs of glyceryl monooleate(GMO)and stearic acid,particularly for load-carrying capacity,wear reduction,and stability of friction over time.The friction and wear reduction effect of C12Amide-TEMPO is also greatly superior to those of C12Ester-TEMPO and C12Amino-TEMPO,in which ester and amino groups replace the amide group,highlighting the critical role of the amide group.The QM calculation results suggest that,in contrast to C12Ester-TEMPO,C12Amino-TEMPO,and the conventional OFMs of GMO and stearic acid,C12Amide-TEMPO can form effective boundary films on iron oxide surfaces with a unique double-layer structure:a strong surface adsorption layer owing to the chemical interactions of the amide oxygen and free radical with iron oxide surfaces,and an upper layer owing to the interlayer hydrogen-bonding between the amide hydrogen and free radical or between the amide hydrogen and oxygen.Moreover,the intralayer hydrogen-bonding in each of the two layers is also possible.We suggest that in addition to strong surface adsorption,the interlayer and intralayer hydrogen-bonding also increases the strength of the boundary films by enhancing the cohesion strength,thereby resulting in the high tribological performance of C12Amide-TEMPO.The findings in this study are expected to provide new hints for the optimal molecular design of OFMs.