Understanding the combustion behavior of electric bicycle batteries and unveiling its relationship with fire extinguishing

In this study,a detailed analysis of the combustion behaviors of the lithium iron phosphate(LFP)and lithium manganese oxide(LMO)batteries used in electric bicycles was conducted.This research included quantitative measurements of the combustion duration,flame height,combustion temperature,heat release rate,and total heat release.The results indicated that LMO batteries exhibited higher combustion temperatures of 600–700°C,flame heights of 70–75 cm,a significantly higher heat release rate of40.1 k W(12 Ah),and a total heat release of 1.04 MJ(12 Ah)compared to LFP batteries with the same capacity.Based on these experimental results,a normalized total heat release(NORTHR)parameter was proposed,demonstrating good universality for batteries with different capacities.Utilizing this parameter,quantitative calculations and optimization of the extinguishing agent dosage were conducted for fires involving these two types of batteries,and the method was validated by extinguishing fires for these two types of battery packs with water-based extinguishing fluids.

Constructing high-toughness polyimide binder with robust polarity and ion-conductive mechanisms ensuring long-term operational stability of silicon-based anodes

Silicon-based materials have demonstrated remarkable potential in high-energy-density batteries owing to their high theoretical capacity.However,the significant volume expansion of silicon seriously hinders its utilization as a lithium-ion anode.Herein,a functionalized high-toughness polyimide(PDMI) is synthesized by copolymerizing the 4,4'-Oxydiphthalic anhydride(ODPA) with 4,4'-oxydianiline(ODA),2,3-diaminobenzoic acid(DABA),and 1,3-bis(3-aminopropyl)-tetramethyl disiloxane(DMS).The combination of rigid benzene rings and flexible oxygen groups(-O-) in the PDMI molecular chain via a rigidness/softness coupling mechanism contributes to high toughness.The plentiful polar carboxyl(-COOH) groups establish robust bonding strength.Rapid ionic transport is achieved by incorporating the flexible siloxane segment(Si-O-Si),which imparts high molecular chain motility and augments free volume holes to facilitate lithium-ion transport(9.8 × 10^(-10) cm^(2) s^(-1) vs.16 × 10^(-10) cm^(2) s~(-1)).As expected,the SiO_x@PDMI-1.5 electrode delivers brilliant long-term cycle performance with a remarkable capacity retention of 85% over 500 cycles at 1.3 A g^(-1).The well-designed functionalized polyimide also significantly enhances the electrochemical properties of Si nanoparticles electrode.Meanwhile,the assembled SiO_x@PDMI-1.5/NCM811 full cell delivers a high retention of 80% after 100 cycles.The perspective of the binder design strategy based on polyimide modification delivers a novel path toward high-capacity electrodes for high-energy-density batteries.

Surface Coating Enabling Sulfide Solid Electrolytes with Excellent Air Stability and Lithium Compatibility

All-solid-state lithium metal batteries(ASSLMBs)featuring sulfide solid electrolytes(SEs)are recognized as the most promising next-generation energy storage technology because of their exceptional safety and much-improved energy density.However,lithium dendrite growth in sulfide SEs and their poor air stability have posed significant obstacles to the advancement of sulfide-based ASSLMBs.Here,a thin layer(approximately 5 nm)of g-C_(3)N_(4)is coated on the surface of a sulfide SE(Li_(6)PS_(5)Cl),which not only lowers the electronic conductivity of Li_(6)PS_(5)Cl but also achieves remarkable interface stability by facilitating the in situ formation of ion-conductive Li3N at the Li/Li_(6)PS_(5)Cl interface.Additionally,the g-C_(3)N_(4)coating on the surface can substantially reduce the formation of H_(2)S when Li_(6)PS_(5)Cl is exposed to humid air.As a result,Li-Li symmetrical cells using g-C_(3)N_(4)-coated Li_(6)PS_(5)Cl stably cycle for 1000 h with a current density of 0.2 mA cm^(-2).ASSLMBs paired with LiNbO_(3)-coated LiNi_(0.6)Mn_(0.2)Co_(0.2)O_(2)exhibit a capacity of 132.8 mAh g^(-1)at 0.1 C and a high-capacity retention of 99.1%after 200 cycles.Furthermore,g-C_(3)N_(4)-coated Li_(6)PS_(5)Cl effectively mitigates the self-discharge behavior observed in ASSLMBs.This surface-coating approach for sulfide solid electrolytes opens the door to the practical implementation of sulfide-based ASSLMBs.

Failure analysis of pouch-type Li–O2 batteries with superior energy density

Li–O2 batteries have attracted significant interest in the past decade owing to their superior high specific energy density in contrast to conventional lithium ion batteries.An 8.7-Ah Li–O2 pouch cell with768.5 Wh kg^-1 was fabricated and characterized in this investigation and the factors that influenced the electrochemical performance of the Li–O2 pouch cell were studied.In contrast to coin/Swagelok-type Li–O2 cells,it was demonstrated that the high-loading air electrode,pulverization of the Li anode,and the large-scale inhomogeneity of the large pouch cell are the major reasons for the failure of Li–O2 batteries with Ah capacities.In addition,safety tests of large Li–O2 pouch cells were conducted for the first time,including nail penetration,crushing,and thermal stability.It was indicated that a self-limiting mechanism is a key safety feature of these batteries,even when shorted.In this study,Li–O2 batteries were investigated in a new size and capacity-scale,which may provide useful insight into the development of practical pouch-type Li–O2 batteries.

Review of the electrochemical performance and interfacial issues of high-nickel layered cathodes in inorganic all-solid-state batteries

All-solid-state batteries potentially exhibit high specific energy and high safety,which is one of the development directions for nextgeneration lithium-ion batteries.The compatibility of all-solid composite electrodes with high-nickel layered cathodes and inorganic solid electrolytes is one of the important problems to be solved.In addition,the interface and mechanical problems of high-nickel layered cathodes and inorganic solid electrolyte composite electrodes have not been thoroughly addressed.In this paper,the possible interface and mechanical problems in the preparation of high-nickel layered cathodes and inorganic solid electrolytes and their interface reaction during charge–discharge and cycling are reviewed.The mechanical contact problems from phenomena to internal causes are also analyzed.Uniform contact between the high-nickel cathode and solid electrolyte in space and the ionic conductivity of the solid electrolyte are the prerequisites for the good performance of a high-nickel layered cathode.The interface reaction and contact loss between the high-nickel layered cathode and solid electrolyte in the composite electrode directly affect the passage of ions and electrons into the active material.The buffer layer constructed on the high-nickel cathode surface can prevent direct contact between the active material and electrolyte and slow down their interface reaction.An appropriate protective layer can also slow down the interface contact loss by reducing the volume change of the high-nickel layered cathode during charge and discharge.Finally,the following recommendations are put forward to realize the development vision of high-nickel layered cathodes:(1)develop electrochemical systems for high-nickel layered cathodes and inorganic solid electrolytes;(2)elucidate the basic science of interface and electrode processes between high-nickel layered cathodes and inorganic solid electrolytes,clarify the mechanisms of the interfacial chemical and electrochemical reactions between the two materials,and address the intrinsic safety issues;(3)strengthen the development of research and engineering technologies and their preparation methods for composite electrodes with high-nickel layered cathodes and solid electrolytes and promote the industrialization of all-solid-state batteries.

High-Performance Quasi-Solid-State Pouch Cells Enabled by in situ Solidification of a Novel Polymer Electrolyte

Conventional lithium-ion batteries(LIBs)with liquid electrolytes are challenged by their big safety concerns,particularly used in electric vehicles.All-solid-state batteries using solid-state electrolytes have been proposed to significantly improve safety yet are impeded by poor interfacial solid–solid contact and fast interface degradation.As a compromising strategy,in situ solidification has been proposed in recent years to fabricate quasi-solid-state batteries,which have great advantages in constructing intimate interfaces and cost-effective mass manufacturing.In this work,quasi-solid-state pouch cells with high loading electrodes(≥3 m Ah cm^(-2))were fabricated via in situ solidification of poly(ethylene glycol)diacrylate-based polymer electrolytes(PEGDA-PEs).Both single-layer and multilayer quasi-solid-state pouch cells(2.0 Ah)have demonstrated stable electrochemical performance over500 cycles.The superb electrochemical stability is closely related to the formation of robust and compatible interphase,which successfully inhibits interfacial side reactions and prevents interfacial structural degradation.This work demonstrates that in situ solidification is a facile and cost-effective approach to fabricate quasi-solid-state pouch cells with both excellent electrochemical performance and safety.

Investigation on step overcharge to self-heating behavior and mechanism analysis of lithium ion batteries

To obtain intrinsic overcharge boundary and investigate overcharge mechanism,here we propose an innovative method,the step overcharge test,to reduce the thermal crossover and distinguish the overcharge thermal behavior,including 5%state of charge(SOC)with small current overcharge and resting until the temperature equilibrium under adiabatic conditions.The intrinsic thermal response and the self-excitation behaviour are analysed through temperature and voltage changes during the step overcharge period.Experimental results show that the deintercalated state of the cathode is highly correlated to self-heating parasitic reactions.Before reaching the upper limit of Negative/Positive(N/P)ratio,the temperature changes little,the heat generation is significantly induced by the reversible heat(endothermic)and ohmic heat,which could balance each other.Following that the lithium metal is gradually deposited on the surface of the anode and reacts with electrolyte upon overcharge,inducing selfheating side reaction.However,this spontaneous thermal reaction could be“self-extinguished”.When the lithium in cathode is completely deintercalated,the boundary point of overcharge is about 4.7 V(~148%SOC,>40℃),and from this point,the self-heating behaviour could be continuously triggered until thermal runaway(TR)without additional overcharge.The whole static and spontaneous process lasts for 115 h and the side reaction heat is beyond 320,000 J.The continuous self-excitation behavior inside the battery is attributed to the interaction between the highly oxidized cathode and the solvent,which leads to the dissolution of metal ions.The dissolved metal ions destroy the SEI(solid electrolyte interphase)film on the surface of the deposited Li of anode,which induces the thermal reaction between lithium metal and the solvent.The interaction between cathode,the deposited Li of anode,and solvent promotes the temperature of the battery to rise slowly.When the temperature of the battery reaches more than 60℃,the reaction between lithium metal and solvent is accelerated.After the temperature rises rapidly to the melting point of the separator,it triggers the thermal runaway of the battery due to the short circuit of the battery.

Preparation of high-purity straight silicon nanowires by molten salt electrolysis

Silicon nanowires of high purity and regular morphology are of prime importance to ensure high specific capacities of lithium-ion batteries and reproducible electrode assembly process.Using nickel formate as a metal catalyst precursor,straight silicon nanowires(65–150 nm in diameter)were directly prepared by electrolysis from the Ni/SiO2 porous pellets with 0.8 wt%nickel content in molten CaCl2 at 900℃.Benefiting from their straight appearance and high purity,the silicon nanowires therefore offered an initial coulombic efficiency of 90.53% and specific capacity of 3377 m Ah/g.In addition,the silicon nanowire/carbon composite exhibited excellent cycle performance,retaining 90.38%of the initial capacity after 100 cycles.Whilst further study on the charge storage performance is still ongoing,these preliminary results demonstrate that nickel formate is an efficient and effective metal catalyst precursor for catalytic preparation of high purity straight silicon nanowires via the molten salt electrolysis,which is suitable for large-scale production.

Novel polyimide binder for achieving high-rate capability and long-term cycling stability of LiNi_(0.8)Co_(0.1)Mn_(0.1)O_(2) cathode via constructing polar and micro-branched crosslinking network structure

LiNi_(0.8)Co_(0.1)Mn_(0.1)O_(2)(NCM811)material,as the promising cathode candidate for next-generation highenergy lithium-ion batteries,has gained considerable attention for extremely high theoretical capacity and low cost.Nevertheless,the intrinsic drawbacks of NCM811 such as unstable structure and inevitable interface side reaction result in severe capacity decay and thermal runaway.Herein,a novel polyimide(denoted as PI-Om DT)constructed with the highly polar and micro-branched crosslinking network is reported as a binder material for NCM811 cathode.The micro-branched crosslinking network is achieved by using 1,3,5-Tris(4-aminophenoxy)benzene(TAPOB)as a crosslinker via condensation reaction,which endows excellent mechanical properties and large free volume.Meanwhile,the massive polar carboxyl(-COOH)groups provide strong adhesion sites to active NCM811 particles.These functions of PIOm DT binder collaboratively benefit to forming the mechanically robust and homogeneous coating layer with rapid Li+diffusion on the surface of NCM811,significantly stabilizing the cathode structure,suppressing the detrimental interface side reaction and guaranteeing the shorter ion-diffusion and electron-transfer paths,consequently enhancing electrochemical performance.As compared to the NCM811 with PVDF binder,the NCM811 using PI-Om DT binder delivers a superior high-rate capacity(121.07 vs.145.38 m Ah g^(-1))at 5 C rate and maintains a higher capacity retention(80.38%vs.91.6%)after100 cycles at 2.5–4.3 V.Particularly,at the high-voltage conditions up to 4.5 and 4.7 V,the NCM811 with PI-Om DT binder still maintains the remarkable capacity retention of 88.86%and 72.5%after 100 cycles,respectively,paving the way for addressing the high-voltage operating stability of the NCM811 cathode.Moreover,the full-charged NCM811 cathode with PI-Om DT binder exhibits a significantly enhanced thermal stability,improving the safety performance of batteries.This work opens a new avenue for developing high-energy NCM811 based lithium-ion batteries with long cycle-life and superior safety performance using a novel and effective binder.

Facet-dependent Thermal and Electrochemical Degradation of Lithium-rich Layered Oxides

Lithium-rich layered oxides(LLOs)are promising candidate cathode materials for safe and inexpensive high-energy-density Li-ion batteries.However,oxygen dimers are formed from the cathode material through oxygen redox activity,which can result in morphological changes and structural transitions that cause performance deterioration and safety concerns.Herein,a flake-like LLO is prepared and aberration-corrected scanning transmission electron microscopy(STEM),in situ high-temperature X-ray diffraction(HT-XRD),and soft X-ray absorption spectrum(sXAS)are used to explore its crystal facet degradation behavior in terms of both thermal and electrochemical processes.Void-induced degradation behavior of LLO in different facet reveals significant anisotropy at high voltage.Particle degradation originates from side facets,such as the(010)facet,while the close(003)facet is stable.These results are further understood through ab initio molecular dynamics calculations,which show that oxygen atoms are lost from the{010}facets.Therefore,the facet degradation process is that oxygen molecular formed in the interlayer and accumulated in the ab plane during heating,which result in crevice-voids in the ab plane facets.The study reveals important aspects of the mechanism responsible for oxygen-anionic activity-based degradation of LLO cathode materials used in lithium-ion batteries.In particular,this study provides insight that enables precise and efficient measures to be taken to improve the thermal and electrochemical stability of an LLO.

Trimethyl phosphate-enhanced polyvinyl carbonate polymer electrolyte with improved interfacial stability for solid-state lithium battery

The polyvinyl carbonate(PVC)polymer solid electrolyte can be in-situ generated in the assembled lithium-ion battery(LIBs);however,its rigid characteristic leads to uneven interface contact between electrolyte and electrodes.In this work,trimethyl phosphate(TMP)is introduced into the precursor solution for in-situ generation of flexible PVC solid electrolyte to improve the interfacial contact of elec-trolyte and electrodes together with ionic conductivity.The PVC-TMP electrolyte exhibits good interface compatibility with the lithium metal anode,and the lithium symmetric battery based on PVC-TMP electrolyte shows no obvious polarization within 1000 h cycle.As a consequence,the initial interfacial resistance of battery greatly decreases from 278Ω(LiFePO_(4)(LFP)/PVC/Li)to 93Ω(LFP/PVC-TMP/Li)at 50℃,leading to an improved cycling stability of the LFP/PVC-TMP/Li battery.Such in-situ preparation of solid electrolyte within the battery is demonstrated to be very significant for commercial application.

A high-performance lithium anode based on N-doped composite graphene

Lithium(Li)metal is the most promising electrode for next-gene ration rechargeable batteries.In order to push the commercialization of the lithium metal batteries,a kind of nitrogen(N)-doped composite graphene(NCG)adopted as the Li plating host was prepared to regulate Li metal nucleation and suppress dendrite growth.Furthermore,a new kind of sandwich-type composite lithium metal(STCL)electrode was developed to improve its application.The STCL electrode can be used as convenient as a piece of Li foil but no dendrite growth.In a symmetric battery,the STCL electrode cycled for more than 4500 h with the overpotential of less than 40 mV.And due to the creative design,the STCL promises the Li-S battery with a prolonged cycling lifespan.

Atomistic mechanism of high ionic conductivity in lithium ytterbium-based halide solid electrolytes:A first-principles study

As the next generation of commercial automotive power batteries begins replacing liquid lithium batteries,many look towards all-solid-state batteries to pioneer the future.All-so lid-state batteries have attracted the attention of countless researchers around the world because of their high safety and high energy density.In recent times,halide solid-state electrolytes have become a research hotspot within solid-state electrolytes because of their potentially superior properties.In this paper,in the framework of DFT,we investigated the atomic mechanisms of improving the ionic conductivity and stability of Li_(3)YbCl_(6).Our calculations show that both trigonal and orthorhombic Li_(3)YbCl_(6) exhibit wide electrochemical windows and metastable properties(100 meV/atom>Ehull>0 meV/atom).However,the orthorhombic Li_(3)YbCl_(6) can be stabilized at high temperatures by taking the vibrational entropy into account,which is supported by the experimental results.Moreover,it is expected that because of the Yb/Li synergistic interactions that,due to their strong mutual coulomb repulsion,influence the Li^(+)transport behavior,the orthorhombic Li_(3)YbCl_(6) might have superior ionic conductivities with appropriate Li+migration paths determined by the Yb^(3+) distribution.Also,higher ionic conductivities can be obtained by regulating the random distribution of Li^(+) ions.Further Li^(+)-deficiency can also largely increase the ionic conductivity by invoking vacancies.This study helps gain a deeper understanding of the laws that govern ionic conductivities and stabilities and provides a certain theoretical reference for the experimental development and design of halide solid-state electrolytes.

Diffusion-Free All-Solid-State Batteries Enabled by an Ionic/Electronic Dual-Conductive Anode

Silicon(Si)is one of the most promising anodes for enabling all-solid-state batteries(ASSBs)with high energy density and safety.However,the tremendous volume change and sluggish kinetics result in poor electrochemical performance.Herein,we proposed an ionic/electronic dual-conductive material of Li_(x)Si as a diffusion-rapid and all-active anode for ASSBs.Compared with pure Si anode,the as-fabricated Li_(x)Si showed dramatic promotions of 35 times electronic and 400 times ionic conductivities.The three-dimensional(3D)ionic-electronic transport system of Li_(x)Si enabled rapid kinetics and uniform volume change of electrode materials in the whole electrode,corresponding to a lower volumechange rate.As a result,the ASSBs with LiCoO_(2)cathode exhibited a reversible discharge capacity of 154.4 mAh g−1,corresponding to an initial Coulombic efficiency of 97.3%.Besides,the batteries delivered a high rate capacity of 99.3 mAh g^(−1)at 2 C and long-term cycle stability of 94.0%after 800 cycles at 1 C,which was much better than the pure Si anode.This study sheds light on a new understanding of the importance of ionic conductivity for Si-based anode and might help inspire the design of advanced anode materials for ASSBs.

A scalable synthesis of silicon nanoparticles as high-performance anode material for lithium-ion batteries

In this work, a scalable and cost-effective method including mechanical milling, centrifugation and spray drying was developed to fabricate Si nanoparticles.The synthesized Si nanoparticles show an average size of 62 nm and exhibit a narrow particle size distribution. The influence of particle sizes on electrochemical performance of Si-based electrode was investigated, and it is found that as the particle size decreases in the studied range, the Si particles show a lower specific capacity and a higher irreversible capacity loss(ICL). Furthermore, an oxide layer with thickness of ～3 nm was detected on the surface of the as-received Si nanoparticles, and this layer can be effectively removed by hydrofluoric acid(HF) etching,resulting in much improved electrochemical performance over the as-received samples.

Electrolytic silicon/graphite composite from SiO_(2)/graphite porous electrode in molten salts as a negative electrode material for lithium-ion batteries

Nano-silicon(nano-Si)and its composites have been regarded as the most promising negative electrode materials for producing the next-generation Li-ion batteries(LIBs),due to their ultrahigh theoretical capacity.However,the commercial applications of nano Si-based negative electrode materials are constrained by the low cycling stability and high costs.The molten salt electrolysis of SiO_(2)is proven to be suitable to produce nano-Si with the advantages of in-situ microstructure control possibilities,cheap affordability and scale-up process capability.Therefore,an economical approach for electrolysis,with a SiO_(2)/graphite porous electrode as cathode,is adopted to produce nano-Si/graphite composite negative electrode materials(SGNM)in this study.The electrolytic product of the optimized porous electrode is taken as the negative electrode materials for LIBs,and it offers a capacity of 733.2 mAh·g^(-1)and an initial coulombic efficiency of 86.8%in a coin-type cell.Moreover,the capacity of the SGNM retained 74.1%of the initial discharging capacity after 50 cycles at 0.2C,which is significantly higher than that of the simple mixture of silicon and graphite obtained from the formation of silicon carbide(SiC)between nano-Si and graphite particles.Notably,this new approach can be applied to a large-scale production.

A comparison of core–shell Si/C and embedded structure Si/C composites as negative materials for lithium-ion batteries

Silicon materials have attracted wide attention as negative materials due to exceptional gravimetric capacity and abundance. The strategy of using nano-silicon materials as structural units to construct nano/micro-structured silicon-based negative materials for lithium-ion batteries has come into sight in recent years. In order to provide guidance for the material structure design of micro-sized silicon-based negative materials in practical application, in this work, two commercialized nano/micro-structured silicon-based negative materials with a specific capacity of about 650 mAh·g^(-1) were investigated and compared in the aspects of material microstructure, electrochemical performance of half cells, and electrode morphological evolution during cycling. The cycling performance(with capacity retention ratio of about 17% higher after 100 cycles) and electrode structure maintenance of the embedded structure Si/C material are superior to those of core–shell Si/C material. This research can provide guidance on design and application of nano/micro-structured silicon-based negative materials.

Current Status and Future Directions in Environmental Stability of Sulfide Solid-State Electrolytes for All-Solid-State Batteries

Recently,sulfide-based solid-state electrolytes(SSEs)have attracted much attention owing to their high ionic conductivity and feasible mechanical features.The environmental stability of sulfide-based SSEs is one of the critical aspects due to the possible decomposition,and ionic conductivity change will affect the fabrication and electrochemical performance of the batteries.Thus,important efforts have been made to reveal and improve their environmental stability,and a timely summary of the progress is urgently needed.In this review,we first clarify the definition of environmental stability and its significance in the context of practical use.After indicating the degradation mechanisms of sulfide-based SSEs,we summarize several effective strategies to improve their stability and also highlight the related theoretical studies.The stability of organic solvents of sulfide SSEs is also summarized and discussed,which may help reliable sulfide SSEs in the battery system.The main target of this review is to gain insights and provide useful guidance to further improve the environmental stability of sulfide SSEs,which will finally promote the commercialization of sulfide-based all-solid-state batteries.

Interfacial Challenges and Strategies toward Practical Sulfide-Based Solid-State Lithium Batteries

All-solid-state lithium batteries are considered as the priority candidates for next-generation energy storage devices due to their better safety and higher energy density.As the key part of solid-state batteries,solid-state electrolytes have made certain research progress in recent years.Among the various types of solid-state electrolytes,sulfide electrolytes have received extensive attention because of their high roomtemperature ionic conductivity and good moldability.However,sulfide-based solid-state batteries are still in the research stage.This situation is mainly due to the fact that the application of sulfide electrolytes still faces challenges in particular of interfacial issues,mainly including chemical and electrochemical instability,unstable interfacial reaction,and solid-solid physical contact between electrolyte and electrode.Here,this review provides a comprehensive summary of the existing interfacial issues in the fabrication of sulfide-based solid-state batteries.The in-depth mechanism of the interfacial issues and the current research progress of the main coping strategies are discussed in detail.Finally,we also present an outlook on the future development of sulfide-based solid-state batteries to guide the rational design of nextgeneration high-energy solid-state batteries.