Mg-doped,carbon-coated,and prelithiated SiO_(x) as anode materials with improved initial Coulombic efficiency for lithium-ion batteries

Silicon suboxide(SiO_(x),x≈1)is promising in serving as an anode material for lithium-ion batteries with high capacity,but it has a low initial Coulombic efficiency(ICE)due to the irreversible formation of lithium silicates during the first cycle.In this work,we modify SiO_(x) by solid-phase Mg doping reaction using low-cost Mg powder as a reducing agent.We show that Mg reduces SiO_(2) in SiO_(x) to Si and forms MgSiO_(3) or Mg_(2)SiO_(4).The MgSiO_(3) or Mg_(2)SiO_(4) are mainly distributed on the surface of SiO_(x),which suppresses the irreversible lithium-ion loss and enhances the ICE of SiO_(x).However,the formation of MgSiO_(3) or Mg_(2)SiO_(4) also sacrifices the capacity of SiO_(x).Therefore,by controlling the reaction process between Mg and SiO_(x),we can tune the phase composition,proportion,and morphology of the Mg-doped SiO_(x) and manipulate the performance.We obtain samples with a capacity of 1226 mAh g^(–1) and an ICE of 84.12%,which show significant improvement over carbon-coated SiO_(x) without Mg doping.By the synergistical modification of both Mg doping and prelithiation,the capacity of SiO_(x) is further increased to 1477 mAh g^(–1) with a minimal compromise in the ICE(83.77%).

Recent advances in hard carbon anodes with high initial Coulombic efficiency for sodium-ion batteries

Initial Coulombic efficiency(ICE)has been widely adopted in battery research as a quantifiable indicator for the lifespan,energy density and rate performance of batteries.Hard carbon materials have been accepted as a promising anode family for sodium-ion batteries(SIBs)owing to their outstanding performance.However,the booming application of hard carbon anodes has been significantly slowed by the low ICE,leading to a reduced energy density at the cell level.This offers a challenge to develop high ICE hard carbon anodes to meet the applications of high-performance SIBs.Here,we discuss the definition and factors of ICE and describe several typical strategies to improve the ICE of hard carbon anodes.The strategies for boosting the ICE of such anodes are also systematically categorized into several aspects including structure design,surface engineering,electrolyte optimization and pre-sodiation.The key challenges and perspectives in the development of high ICE hard carbon anodes are also outlined.

Enhancing Li cycling coulombic efficiency while mitigating “shuttle effect” of Li-S battery through sustained release of LiNO_(3)

In practical lithium-sulfur batteries(LSBs),the shuttle effect and Li cycling coulombic efficiency(CE) are strongly affected by the physicochemical properties of solid electrolyte interphase(SEI).LiNO_(3) is widely used as an additive in electrolytes to build a high-quality SEI,but its self-sacrificial nature limits the ability to mitigate the shuttle effect and stabilize Li anode during long-term cycling.To counteract LiNO_(3) consumption during long-term cycling without using a high initial concentration,inspired by sustainedrelease drugs,we encapsulated LiNO_(3) in lithiated Nafion polymer and added an electrolyte co-solvent(1,1,2,2-tetrafluoroethylene 2,2,2-trifluoromethyl ether) with poor LiNO_(3) solubility to construct highquality and durable F-and N-rich SEI.Theoretical calculations,experiments,multiphysics simulations,and in-situ observations confirmed that the F-and N-rich SEI can modulate lithium deposition behavior and allow persistent repair of SEI during prolonged cycling.Hence,the F-and N-rich SEI improves the Li anode cycling CE to 99.63% and alleviates the shuttle effect during long-term cycling.The lithium anode with sustainable F-and N-rich SEI shows a stable Li plating/stripping over 2000 h at 1 mA cm^(-2).As expected,Li‖S full cells with this SEI achieved a long lifespan of 250 cycles,far exceeding cells with a routine SEI.The Li‖S pouch cell based on F-and N-rich SEI also can achieve a high energy density of about300 Wh kg^(-1) at initial cycles.This strategy provides a novel design for high-quality and durable SEls in LSBs and may also be extendable to other alkali metal batteries.

Boosting high initial coulombic efficiency of hard carbon by in-situ electrochemical presodiation

Hard carbon(HC)is a promising anode material for sodium ion batteries(SIBs),whereas inferior initial coulombic efficiency(ICE)severely limits its practical application.In the present work,we propose an in situ electrochemical presodiation approach to improve ICE by mixing sodium biphenyl(Na-Bp)dimethoxyethane(DME)solution with DME-based ether electrolyte.A solid electrolyte interface(SEI)could be formed beforehand on the HC electrode and Na^(+)was absorbed to nanopores and graphene stacks,compensating for the sodium loss and preventing electrolyte decomposition during the initial charge and discharge cycle.By this way,the ICE of half-cells was increased to nearly 100%and that of full-cells from 45%to 96%with energy density from 132.9 to 230.5 W h kg^(-1).Our work provides an efficient and facile method for improving ICE,which can potentially promote the practical application of HCbased materials.

Simple synthesis of sandwich-like SnSe2/rGO as high initial coulombic efficiency and high stability anode for sodium-ion batteries

Metal selenides owing to their high theoretical capacity and good conductivity are considered as one of the potential candidates for the anode materials of sodium-ion batteries(SIBs).However,their practical applications are greatly restricted by the poor cycling performances and complicated synthesis methods.In this work,a sandwich-like Sn Se2/reduced graphene oxide(r GO)composite with a small amount of r GO(7.3%)is synthesized by a simple one-pot solvothermal technique.The as-synthesized Sn Se2/r GO shows improved initial coulombic efficiency(ICE)of 73.7%,high capacity of 402.0 m Ah g-1 after 150 cycles at 0.1 A g-1 with a retention of 86.2%and outstanding rate performances.The abundant Sn-O-C bonds of synthesized material not only accelerate the charge transfer at the interface but also enhance the mechanical strength to accommodate volume variation and prevent active material loss during cycling.Moreover,the compact structure leads to thin solid electrolyte interface(SEI)so that high initial coulombic efficiency was obtained.Furthermore,full cells are assembled to test its potential application.This work offers a simple method to synthesize Sn Se2/r GO as a candidate anode for SIBs.

Engineering Mesoporous Structure in Amorphous Carbon Boosts Potassium Storage with High Initial Coulombic Efficiency

Amorphous carbon shows great potential as an anode material for high-performance potassium-ion batteries;however,its abundant defects or micropores generally capture K ions,thus resulting in high irreversible capacity with low initial Coulombic efficiency(ICE)and limited practical application.Herein,pore engineering via a facile self-etching strategy is applied to achieve mesoporous carbon(meso-C)nanowires with interconnected framework.Abundant and evenly distributed mesopores could provide short K^+ pathways for its rapid diffusion.Compared to microporous carbon with highly disordered structure,the meso-C with Zn-catalyzed short-range ordered structure enables more K^+to reversibly intercalate into the graphitic layers.Consequently,the mesoC shows an increased capacity by ~100 mAh g^-1 at 0.1 A g^-1,and the capacity retention is 70.7% after 1000 cycles at 1 A g^-1.Multiple in/ex situ characterizations reveal the reversible structural changes during the charging/discharging process.Particularly,benefiting from the mesoporous structure with reduced specific surface area by 31.5 times and less defects,the meso-C generates less irreversible capacity with high ICE up to 76.7%,one of the best reported values so far.This work provides a new perspective that mesopores engineering can effectively accelerate K^+ diffusion and enhance K^+ adsorption/intercalation storage.

Natural Stibnite for Lithium‑/Sodium‑Ion Batteries:Carbon Dots Evoked High Initial Coulombic Efficiency

The application of Sb_(2)S_(3)with marvelous theoretical capacity for alkali metal-ion batteries is seriously limited by its poor electrical conductivity and low initial coulombic efficiency(ICE).In this work,natural stibnite modified by carbon dots(Sb_(2)S_(3)@xCDs)is elaborately designed with high ICE.Greatly,chemical processes of local oxidation–partial reduction–deep coupling for stibnite reduction of CDs are clearly demonstrated,confirmed with in situ high-temperature X-ray diffraction.More impressively,the ICE for lithium-ion batteries(LIBs)is enhanced to 85%,through the effect of oxygen-rich carbon matrix on C–S bonds which inhibit the conversion of sulfur to sulfite,well supported by X-ray photoelectron spectroscopy characterization of solid electrolyte interphase layers helped with density functional theory calculations.Not than less,it is found that Sb–O–C bonds existed in the interface effectively promote the electronic conductivity and expedite ion transmission by reducing the bandgap and restraining the slip of the dislocation.As a result,the optimal sample delivers a tremendous reversible capacity of 660 mAh g^(−1)in LIBs at a high current rate of 5 A g^(−1).This work provides a new methodology for enhancing the electrochemical energy storage performance of metal sulfides,especially for improving the ICE.

An almost full reversible lithium-rich cathode: Revealing the mechanism of high initial coulombic efficiency

Low initial Coulombic efficiency (ICE) is an important impediment to practical application of Li-rich layered oxides (LLOs), which is due to the irreversible oxygen release. It is generally considered that surface oxygen vacancies are conducive to the improvement of ICE of LLOs. To reveal the relation of oxygen vacancies and ICE, sample PLO (Li-Mn-Cr-O) and its treated product (TLO) are comprehensive investigated in this work. During the treated process, part of oxygen atoms return to original constructed vacancies. It makes oxygen vacancies in sample TLO much poorer than those in sample PLO, and induces the formation of Li-poor spinel-layered integrated structure. Electrochemical measurement indicates the ICE of sample PLO is only 80.8%, while sample TLO is almost full reversible with the ICE of ~97.1%. In term of high-energy X-ray diffraction, scanning transmission electron microscopy, X-ray photoelectron spectroscopy and synchrotron hard/soft X-ray absorption spectroscopy, we discover that the ICE is difficult to be improved significantly just by building oxygen vacancies. LLOs with high ICE not only have to construct suitable oxygen vacancies, but also require other components with Li-poor structure to stabilize oxygen. This work provides deep insight into the mechanism of high ICE, and will contribute to the design and development of LLOs for next-generation high-energy lithium-ion batteries.

Sn Alloy and Graphite Addition to Enhance Initial Coulombic Efficiency and Cycling Stability of SiO Anodes for Li-Ion Batteries

Silicon monoxide(SiO)has aroused increased attention as one of the most promising anodes for high-energy density Li-ion batteries.To enhance the initial Coulombic efficiencies(ICE)and cycle stability of SiO-based anodes,a new facile composition and electrode design strategy have been adapted to fabricate a SiO-Sn-Co/graphite(G)anode.It achieves a unique structure where tiny milled SiO-Sn-Co particles are dispersed among two graphite layers.In this hybrid electrode,Sn-Co alloys promoted Li;extraction kinetics,and the holistic reversibility of SiO and graphite enhanced the electrical conductivity.The SiO-Sn-Co/G electrode delivered an average ICE of 77.6%and a reversible capacity of 640 mAh g^(-1)at 800 mA g^(-1),and the capacity retention was above 98%after 100 cycles,which was much higher than that of the SiO with an ICE of 55.3%and a capacity retention of 50%.These results indicated that this was reliable method to improve the reversibility and cycle ability of the SiO anode.Furthermore,based on its easy and feasible fabrication process,it may provide a suitable choice to combine other alloy anodes with the graphite anode.

Cautious interpretation of coulombic efficiency(CE) in lithium metal batteries

The soaring demand for electrical energy storage technologies stimulated by advanced portable devices, prospering electric vehicles, and large-scale grid storage applications have triggered explosive research on Li metal battery (LMB), which has been widely acknowledged as the most promising energy storage technology of the future that can break the energy-density bottleneck of the state-of-art lithium-ion battery (LIB) technology [1,2].

Coulombic interaction in the colloidal oriented-attachment growth of tetragonal nanorods

In this report, the analytical expression of Coulombic interaction between a spherical nanoparticle and a tetragonal nanorod is derived. To evaluate the Coulombic interaction in the oriented attachment growth of tetragonal nanorods, we analyze the correlation between the Coulombic interaction and the important growth parameters, including： nanoparticle- nanorod separation, aspect ratio of the nanorods, and surface charge density. Our work opens up the opportunity to investi-gate interparticle interactions in the oriented attachment growth of tetragonal nanorods.

Low-temperature-pyrolysis preparation of nanostructured graphite towards rapid potassium storage with high initial Coulombic efficiency

Industrially prepared artificial graphite(AG)is attractive for potassium-ion batteries(PIBs),but its rate performance is poor and the production process is energy intensive,so developing an efficient strategy to produce novel graphite with low energy consumption and high performance is economically important.Herein,a nanostructured graphite composed of multi-walled carbon nanotubes(MWCNTs)and graphite shells was prepared by one-pot method through low-temperature pyrolysis of iron-based metal-organic framework(MOF)and carbon source.The high graphitization degree of nanostructured graphite makes the initial Coulombic efficiency(ICE)exceed 80%,and the three-dimensional(3D)conductive network ensures a specific capacity of 234 mAh·g^(−1)after 1000 cycles at a high current density of 500 mA·g^(−1).In addition,the typical graphite potassium storage mechanism is also demonstrated by in situ X-ray diffraction(XRD)and in situ Raman spectroscopy,and its practicality is also proved by the voltage of the full cells.This work provides a feasible way to optimize the practical production process of AG and expand its application in energy storage.

Fabricating multi-porous carbon anode with remarkable initial coulombic efficiency and enhanced rate capability for sodium-ion batteries

Due to the abundant sodium reserves and high safety,sodium ion batteries(SIBs)are foreseen a promising future.While,hard carbon materials are very suitable for the anode of SIBs owing to their structure and cost advantages.However,the unsatisfactory initial coulombic efficiency(ICE)is one of the crucial blemishes of hard carbon materials and the slow sodium storage kinetics also hinders their wide application.Herein,with spherical nano SiO_(2)as pore-forming agent,gelatin and polytetrafluoroethylene as carbon sources,a multi-porous carbon(MPC)material can be easily obtained via a co-pyrolysis method,by which carbonization and template removal can be achieved synchronously without the assistance of strong acids or strong bases.As a result,the MPC anode exhibited remarkable ICE of 83%and a high rate capability(208 m Ah/g at 5 A/g)when used in sodium-ion half cells.Additionally,coupling with Na3V2(PO4)3as the cathode to assemble full cells,the as-fabricated MPC//NVP full cell delivered a good rate capability(146 m Ah/g at 5 A/g)as well,implying a good application prospect the MPC anode has.

Improving the Initial Coulombic Efficiency of Carbonaceous Materials for Li/Na‑Ion Batteries:Origins,Solutions,and Perspectives

Carbonaceous materials for lithium(Li)/sodium(Na)-ion batteries have attracted significant attention because of their widespread availability,renewable nature,and low cost.During the past decades,although great efforts have been devoted to developing high-performance carbonaceous materials with high capacity,long life span,and excellent rate capability,the low initial Coulombic efficiency(ICE)of high-capacity carbonaceous materials seriously limits their practical applications.Various methods have been successfully exploited,and a revolutionary impact has been achieved through the utilization of different techniques.Different carbonaceous materials possess different ion storage mechanisms,which means that the initial capacity loss may vary.However,there has rarely been a special review about the origins of and progress in the ICE for carbonaceous materials from the angle of the crystal structure.Hence,in this review,the structural differences between and ion storage mechanisms of various carbonaceous materials are first introduced.Then,we deduce the correlative factors of low ICE and thereafter summarize the proposed strategies to address these issues.Finally,some challenges,perspectives,and future directions on the ICE of carbonaceous materials are given.This review will provide deep insights into the challenges of improving the ICE of carbonaceous anodes for high-energy Li/Na-ion batteries,which will greatly contribute to their commercialization process.

空间连杆引纬机构的刚柔耦合磨损分析

为准确预测空间连杆引纬机构间隙磨损机制,通过结合Lankarani-Nikravesh与Bai碰撞力模型,建立可变刚度与阻尼系数非连续接触碰撞力模型,采用改进的Coulomb摩擦力模型描述含间隙机构旋转铰的切向摩擦力,通过Lagrange方法对系统动力学建模;其次选取空间连杆为柔性化对象,综合Ansys与Adams分析,对空间连杆引纬机构进行刚柔耦合动力学仿真;最后将系统的动态仿真响应结果与Archard模型相结合,求解运动副磨损情况。结果表明:柔性构件可以有效缓解机构间隙碰撞的冲击作用,间隙为0.15 mm条件下,剑头加速度振荡最大幅值缩减53.2%;当间隙升至0.5 mm后,虽磨损范围大幅增加,但间隙磨损深度并未随之大幅提升。

Access to advanced sodium-ion batteries by presodiation:Principles and applications

Sodium-ion batteries(SIBs)are expected to offer affordability and high energy density for large-scale energy storage system.However,the commercial application of SIBs is hurdled by low initial coulombic efficiency(ICE),continuous Na loss during long-term operation,and low sodium-content of cathode materials.In this scenario,presodiation strategy by introducing an external sodium reservoir has been rationally proposed,which could supplement additional sodium ions into the system and thereby markedly improve both the cycling performance and energy density of SIBs.In this review,the significance of presodiation is initially introduced,followed by comprehensive interpretation on technological properties,underlying principles,and associated approaches,as well as our perspectives on present inferiorities and future research directions.Overall,this contribution outlines a distinct pathway towards the presodiation methodology,of significance but still in its nascent phase,which may inspire the targeted guidelines to explore new chemistry in this field.

Molten-LiCl induced thermochemical prelithiation of SiOx:Regulating the active Si/O ratio for high initial Coulombic efficiency

The low initial Coulombic efficiency(ICE)of SiOx anode caused by the irreversible generation of LiySiOz and Li20 during lithiation process limits its application for high energy-density lithium-ion batteries.Herein,we report a molten-salt-induced thermochemical.prelithiation strategy for regulating the electrochemically active Si/O ratio of SiOx and thus enhancing ICE through thermal treatment of pre-synthesized LiNH2-coated SiOx in molten LiCl at 700℃.Bulk SiOx micro-particle was transformed into pomegranatelike prelithiated micro-cluster composite(M-Li-SiOx)with SiOx core and outer nano-sized agglomerates consisting of Li2Si20s,SiO2,and Si.Through the analysis of the reaction intermediates,molten-UC!could initiate reactions and promote mass transfer by the continuous extraction of oxygen component from SiOx particle inner in the form of inert Li2Si20s and SiO2 nanotubes to realize the.prelithiation.The degree of prelithiation can be regulated by adjusting the coating amount of LiNH2 layer,and the resulted M-Li-SiOx displays a prominent improvement of ICE from 58.73%to 88.2%.The graphite/M-Li-SiOx(8:2)composite electrode delivers a.discharge capacity of 497.29 mAh·g^(-1) with an ICE of 91.79%.By pairing graphite/M-Li-SiOx anode and LiFeP04 cathode in a full-cell an enhancement of energy density of 37.25%is realized compared with the full-cell containing graphite/SiOx anode.Furthermore,,ex-situ X-ray photoelectron spectroscopy(XPS)/Raman/X-ray diffraction(XRD)and related electrochemical measurements reveal the SiOx core and Si of M-Li-SiOx participate in the lithiation,and pre-generated Li2Si20s with u+diffusivity and pomegranate-like.structure reduces the reaction resistance and interface impedance of the solid electrolyte interphase(SEI)film.

Surface engineering based on in situ electro-polymerization to boost the initial Coulombic efficiency of hard carbon anode for sodium-ion battery

Hard carbon(HC) is considered as a commercial candidate for anode materials of sodium-ion batteries due to its low cost and excellent capacity. However, the problem of low initial Coulombic efficiency is still urgently needed to be solved to promote the industrialization of HC.In this paper, 2,2-dimethylvinyl boric acid(DEBA) is used to modify the surface of HC to prepare HC-DEBA materials. During the cycling, the C = C bonds of DEBA molecules will be in situ electro-polymerized to form a polymer network, which can act as the passive protecting layer to inhibit irreversible decomposition of electrolyte,and induce a thinner solid electrolyte interface with lower interface impedance. Therefore, HC-DEBA has higher initial Coulombic efficiency and better cycling stability. In ester-based electrolyte, the initial Coulombic efficiency of the optimized HC-DEBA-3% increases from 65.2% to77.2%. After 2000 cycles at 1 A·g^(-1), the capacity retention rate is 90.92%. Moreover, it can provide a high reversible capacity of 294.7 m Ah·g^(-1) at 50 mA·g^(-1). This simple surface modification method is ingenious and versatile,which can be extended to other energy storage materials.

Methods of improving the initial Coulombic efficiency and rate performance of both anode and cathode materials for sodium-ion batteries

Sodium-ion batteries(SIBs) have gained more scientists’ interest, owing to some facts such as the natural abundance of Na, the similarities of physicochemical characteristics between Li and Na. The irreversible Na+ions consumption during the first cycle of charge/discharge process(due to the formation of the solid electrolyte interface(SEI) on the electrode surface and other irreversible reactions) is the factor that determines high performance SIBs and largely reduces the capacity of the full cell SIBs. Thus, the initial coulombic efficiency(ICE) of SIBs for both anode and cathode materials, is a key parameter for high performance SIBs, and the point is to increase the transport rate of the Na+ions. Therefore, developing SIBs with high ICE and rate performance becomes vital to boost the commercialization of SIBs. Here we provide a review on the methods to improve the ICE and the rate performance, by summarizing some methods of improving the ICE and rate performance of the anode and cathode materials for SIBs, and end by a conclusion with some perspectives and recommendations.

An effective artificial layer boosting high-performance all-solid-state lithium batteries with high coulombic efficiency

All-solid-state lithium batteries(ASSLBs)employ high-capacity lithium(Li)metal as the anode and exhibit a higher energy density than that of conventional Li-ion batteries.However,the problems arose from the Li dendrites induce severely parasitic reaction between Li and electrolytes,leading to low coulombic efficiency(CE)and poor cyclic stability.Herein,a poly(vinylidene-co-hexafluoropropylene)/lithium nitrate(PVDF-HFP/LiNO_(3),marked as PFH/LN)artificial layer is employed to modified Li and achieve high CE ASSLBs with polyethylene oxide-Li_(6.4) La_(3)Zr_(1.4)Ta_(0.6)O_(12)(PEO-LLZTO)electrolyte.LN serves as a functionalized additive to facilitate the formation of a robust solid electrolyte interface(SEI),effi-ciently suppressing the formation of Li dendrites.Additionally,LN as a“binder”effectively links PFH with Li,providing good contact.PFH possesses high mechanical strength and moderate flexibility,which can not only physically inhibit the growth of Li dendrites,but also maintain the structural integrity of arti-ficial layer over long-term cycles.Finally,Li/Li cells with such artificial layer demonstrate ultralong cycle life of 1800 and 1000 h under 0.2 and 0.4 mA cm^(-1),respectively.Furtherly,high CE can be achieved when applied in both LiFePO 4 full cells and Li-Cu half cells.This work offers a facile and efficient strategy to greatly promote CE in PEO-based ASSLBs.