Synthesizing an inorganic-rich solid electrolyte interphase by tailoring solvent chemistry in carbonate electrolyte for enabling high-voltage lithium metal batteries

High-voltage(>4.0 V)lithium metal battery(LBM)is considered to be one of the most promising candidates for next-generation high-energy batteries.However,the commercial carbonate electrolyte delivers a poor compatibility with Li metal anode,and its organic dominated solid electrolyte interphase(SEI)shows a low interfacial energy and a slow Li^(+)diffusion ability.In this work,an inorganic LiF-Li_(3)N rich SEI is designed to enable high-voltage LBM by introducing nano-cubic LiF and LiNO_(3)into1 M LiPF_(6)ethylene carbonate(EC)/dimethyl carbonate(DMC)(v:v=1:1)electrolyte.Specifically,the unique nano-cubic structure of as-synthetized LiF particles achieves its high concentration dissolution in carbonate electrolyte to enhance the interfacial energy of SEI.In addition,tetramethylene sulfolane(TMS)is used as a carrier solvent to dissolve LiNO_(3)in the carbonate electrolyte,thereby deriving a Li_(3)N-rich SEI.As a result,the as-designed electrolyte shows a high average Li plating/striping CE of 98.3%after 100 cycles at 0.5 m A cm^(-2)/0.5 mA h cm^(-2).Furthermore,it also enables the ultrathin Li(~50μm)‖LiNi_(0.8)Co_(0.1)Mn_(0.1)O_(2)(NCM,4.4 mA h cm^(-2))full cell to deliver a high-capacity retention of 80.4%after 100 cycles with an outstanding average CE of 99.7%.Notably,the practical application prospect of the modified electrolyte is also estimated in LiNi_(0.8)Co_(0.1)Mn_(0.1)O_(2)‖Li pouch cell with an energy density of 261.2 W h kg^(-1).This work sheds light on the internal mechanism of Li^(+)transport within the inorganic dominated SEI and provides a simple approach to stabilize the high-voltage LMBs.

Stable lithium metal anode enabled by a robust artificial fluorinated hybrid interphase

One of the key challenges for achieving stable lithium(Li) metal anode is the construction of the rational solid electrolyte interphase(SEI),but its realization still faces enormous challenges.In this work,a robust artificial fluorinated hybrid interphase consisting of lithium-bismuth(Li3Bi) alloy and lithium-fluoride(LiF) was designed to regulate Li deposition without Li dendrite growth.The obtained hybrid interphase showed the high Li+diffusion rate(3.5 × 10^(-4)S cm^(-1)),high electron resistivity(9.04 × 10^(4)Ω cm),and high mechanical strength(1348 MPa),thus enabling the uniform Li deposition at the Li/SEI interface.Specifically,Li3Bi alloy,as a superionic conductor,accelerated the Li+transport and stabilized the hybrid interphase.Meanwhile,LiF was identified as a superior electron-blocker to inhibit the electron tunneling from the Li anode into the SEI.As a result,the modified Li anode showed the stable Li plating/stripping behaviors over 1000 cycles even at 20 mA cm^(-2).Moreover,it also enabled the Li(50 μm)‖LiNi_(0.8)Co_(0.1)Mn_(0.1)O_(2)(4.4 mA h cm^(-2)) full cell to achieve an average Coulombic efficiency(CE) of 99.6%and a high-capacity retention of 79.2% after 100 cycles,whereas the bare Li anode only exhibited a low-capacity retention of 8.0%.This work sheds light on the internal mechanism of Li+transport within the hybrid interface and provides an effective approach to stabilize the interface of Li metal anode.

Topology Optimization of Sound-Absorbing Materials for Two-Dimensional Acoustic Problems Using Isogeometric Boundary Element Method

In this work,an acoustic topology optimizationmethod for structural surface design covered by porous materials is proposed.The analysis of acoustic problems is performed using the isogeometric boundary elementmethod.Taking the element density of porousmaterials as the design variable,the volume of porousmaterials as the constraint,and the minimum sound pressure or maximum scattered sound power as the design goal,the topology optimization is carried out by solid isotropic material with penalization(SIMP)method.To get a limpid 0–1 distribution,a smoothing Heaviside-like function is proposed.To obtain the gradient value of the objective function,a sensitivity analysis method based on the adjoint variable method(AVM)is proposed.To find the optimal solution,the optimization problems are solved by the method of moving asymptotes(MMA)based on gradient information.Numerical examples verify the effectiveness of the proposed topology optimization method in the optimization process of two-dimensional acoustic problems.Furthermore,the optimal distribution of sound-absorbingmaterials is highly frequency-dependent and usually needs to be performed within a frequency band.

轴对中的激光测量工艺在船舶修船的应用

对激光测量进行了初步的介绍,之后针对泵浦对中测量、主机和艉轴孔轴线对中测量分别讲解了其测量工艺的改进。

Regulating the d band in WS_(2)@NC hierarchical nanospheres for efficient lithium polysulfide conversion in lithium-sulfur batteries

The performance of lithium-sulfur batteries is deteriorated by the inferior conductivity of sulfur,the shuttle effect of lithium polysulfides(LiPSs),sluggish redox kinetics of polysulfide intermediates and serious volumetric expansion of sulfur.To overcome these challenges,we report a versatile route to prepare multi-functional nanocomposites with tuable hierarchical structure via ammonium hydroxide(NH_(3)·H_(2) O)induced self-assembly.The versatility of the system has been demonstrated that the organization of the hierarchical structure can be regulated by adding different amounts of NH_(3)·H_(2) O,and WS_(2) and Co_(9)S_(8) with nitrogen-doped carbon coating(denoted as WS_(2)@NC and Co_(9)S_(8)@NC)can be prepared by adding different precursor salts.When the as-prepared materials are applied for Li-S batteries,the WS_(2)@NC composite exhibits a reversible capacity of 1107.4 mAh g^(-1) at 0.1 C after 500 cycles and even 728.9 mAh g^(-1) at2 C for 1000 cycles,which is significantly better than the Co_(9)S_(8) counterpart and other reported WS_(2) sulfur hosts.Experimentally,the advantageous performance of WS_(2) could be attributed to its higher surface area and total pore volume,giving rise to the easier access to electrolyte and better ability to buffer the volume change during the charge/discharge process.Theoretically,the density function theory(DFT)calculation reveals that the as-prepared WS_(2) has a higher binding energy towards LiPSs as well as a lower energy barrier for Li^(+)diffusion on the surface than Co_(9)S_(8).More significantly,the density of states(DOS)analysis further confirms that the superior performance is mainly ascribed to the more prominent shifting and the more charge compensation from d band of W than Co,which increase electronic concentration and give more hybridization of d-p orbitals in the Fermi level of the adsorbed Li2 S4 to accelerate the lithium polysulfide interfacial redox and conversion dynamics in WS_(2).By proposing this mechanism,this work sheds new light on the understanding of catalytic conversion of lithium polysulfides at the atomic level and the strategy to develop advanced cathode materials for high-performance lithium-sulfur batteries.

Trajectory Design for UAV-Enabled Maritime Secure Communications:A Reinforcement Learning Approach

This paper investigates an unmanned aerial vehicle(UAV)-enabled maritime secure communication network,where the UAV aims to provide the communication service to a legitimate mobile vessel in the presence of multiple eavesdroppers.In this maritime communication networks(MCNs),it is challenging for the UAV to determine its trajectory on the ocean,since it cannot land or replenish energy on the sea surface,the trajectory should be pre-designed before the UAV takes off.Furthermore,the take-off location of the UAV and the sea lane of the vessel may be random,which leads to a highly dynamic environment.To address these issues,we propose two reinforcement learning schemes,Q-learning and deep deterministic policy gradient(DDPG)algorithms,to solve the discrete and continuous UAV trajectory design problem,respectively.Simulation results are provided to validate the effectiveness and superior performance of the proposed reinforcement learning schemes versus the existing schemes in the literature.Additionally,the proposed DDPG algorithm converges faster and achieves higher utilities for the UAV,compared to the Q-learning algorithm.

Conceptual framework of modern Zangxiang concept: a qualitative content analysis

Background:Some scholars believe modern Zangxiang concept is conceived under the thought of bio-medicine (Western medicine),which differs greatly compared to the ancient one.The view put forward stirs up great argument.Therefore,we attempt to explore whether the modern Zangxiang concept can fully reflect the specific content and structural relationship of ancient one through analyzing the frame structure of modern Zangxiang concept.Methods:The qualitative content analysis was used.The document was selected from Zangxiang Chapter in Fundamental Theory of Traditional Chinese Medicine (7th edition).The textual document was added to QSR International's NVivo qualitative data analysis software.Text was manually coded line by line according to the content described,and new categories were identified which were further divided into initial code,sub-theme,and theme.The relationships among them were explored,and a visual map of the body of knowledge (BoK) in Zangxiang theory was depicted.The similarities and differences between modern and ancient Zangxiang concepts were discussed by interpreting these themes,relationships and the visual map.Results:After analysis,there were 126 initial codes,13 sub-themes,and 4 themes including structure,function,functional outcome and the corresponding external sign.Two principal relationships,generation and mutual promotion,restriction,and inter-dependence in function were obtained.By analyzing four themes and two kinds of principal relationships,we found five different aspects between modern Zangxiang concept and ancient Zangxiang theory.Conclusion:The BoK of the modern Zangxiang concept contains four themes:structure,function,functional outcome,and the corresponding external sign.The principal relationship is referring to generation between structure and function,and between function and its corresponding outcomes.Great differences exist when talking about modern Zangxiang concept which doesn't reflect TCM characteristics and is more inclined to bio-medicine in structure from the perspective of ancient TCM theory.

Incoherent pulse Doppler lidar as the velocimeter system

This note reports a new type of incoherent pulse laser Doppler lidar velocimeter with iodine molecular filter as a frequency discriminator. Its transmitter subsystem applies a Nd:YAG pulse laser which is injected with a single longitudinal-mode diode pumped continuous seeder laser. The field experiment proved that this velocimeter measurement results are consistent with those measured by photoelectric velocimeter. Measurements of eight different velocities show that the standard deviation is 0.56m/s, the range resolution is 3.75m.

Method for segmentation of overlapping fish images in aquaculture

Individual fish segmentation is a prerequisite for feature extraction and object identification in any machine vision system.In this paper,a method for segmentation of overlapping fish images in aquaculture was proposed.First,the shape factor was used to determine whether an overlap exists in the picture.Then,the corner points were extracted using the curvature scale space algorithm,and the skeleton obtained by the improved Zhang-Suen thinning algorithm.Finally,intersecting points were obtained,and the overlapped region was segmented.The results show that the average error rate and average segmentation efficiency of this method was 10%and 90%,respectively.Compared with the traditional watershed method,the separation point is accurate,and the segmentation accuracy is high.Thus,the proposed method achieves better performance in segmentation accuracy and effectiveness.This method can be applied to multi-target segmentation and fish behavior analysis systems,and it can effectively improve recognition precision.

Synthesis ofα-Li FeO_(2)/Graphene nanocomposite via layer by layer self-assembly strategy for lithium-ion batteries with excellent electrochemical performance

As a potential alternative cathode material,α-LiFeO2 suffers a realization handicap,mainly due to its poor electrical conductivity and low lithium ion diffusion rate.In this work,we have successfully synthesized α-LiFeO2/rGO nanocomposite through a layer by layer self-assembly modification process and annealing treatment.Due to the strong electrostatic attraction between opposite cha rged spices,α-LiFeO2 nanoparticles were homogeneously dispersed on the graphene sheet to form a typical interconnected conducting network which was bene ficial for electronic conductivity and ionic diffu sivity.In comparison to pristine α-LiFeO2,the α-LiFeO2/rGO displayed an excellent electrochemical perfo rmance with average discharge capacities of 238.9,187.2,178.4,121.8 and 99.5 mA hg^-1 at 0.1,0.2,0.5,1 and 2 C,respectively.Besides,the specific capacity retained 164.9 mA h g^-1 and 107.98 mA h g^-1 after 50 cycles at 0.5 C and 1 C,respectively.The remarkable progress in rate capability and cycling ability of this new nanocomposite developed a new approach to improve the electrochemical performance of α-LiFeO2.