The research, led by Qindong Yang of Tsinghua University with colleagues from the National Institute for Environmental Studies in Japan, the University of Southern Denmark and Tianjin and Nankai Universities, is the first to couple province-resolved fleet projections for China with explicit battery degradation modelling and dynamic material flow analysis. That combination matters, because most previous assessments of shared mobility’s resource benefits assumed batteries simply last a fixed number of years. In reality, a shared electric car can be on the road for many more hours a day than a privately owned one, racking up charge cycles and deep discharges that age its cells far faster than the average owner’s vehicle would.

The team’s modelling shows just how consequential that distinction is. For vehicles equipped with lithium nickel manganese cobalt oxide batteries, the high-energy chemistry known as NMC811 that many manufacturers favour for long-range driving, shared mobility was expected to save between 5.3 and 8.1 million tonnes of cumulative lithium demand by 2060 under static lifetime assumptions. When degradation was factored in realistically, those savings shrank to between 2.6 and 4.7 million tonnes. In other words, the faster turnover of degraded shared-fleet batteries could consume a large share of the raw material reductions that car sharing was supposed to deliver.

Not every chemistry suffers equally, however. The study finds that more durable batteries, notably lithium iron phosphate, the chemistry that dominates China’s mass-market electric fleet, and lithium nickel cobalt aluminium oxide cells, can preserve or even amplify the material savings of shared mobility. This creates what the authors describe as a chemistry-dependent dividend: the environmental case for sharing vehicles is only as strong as the longevity of the batteries inside them. A shared fleet built on robust, degradation-resistant packs delivers genuine resource relief, while one built on energy-dense but fragile cells may simply burn through minerals at nearly the same pace as private ownership.

Behind these numbers lies a subtle temporal trap that the researchers call a trade-off in timing. Intensive use accelerates battery retirement, which sounds bad but has a hidden benefit: retired packs feed the recycling stream sooner, boosting the supply of secondary materials recovered from end-of-life batteries. At the same time, many circular-economy strategies route retired electric vehicle batteries into second-life applications, typically stationary grid storage, before they are finally recycled. The study shows that this detour delays recycling, locks secondary material supply to vehicle manufacturing timelines, and increases near-term demand for newly mined lithium and other critical minerals. The very strategy designed to squeeze extra value from spent batteries can, paradoxically, deepen short-term dependence on primary resources.

The scale of the analysis is one of its distinguishing strengths. Rather than treating China as a single homogeneous market, the team resolved their projections at the provincial level, capturing the enormous variation in climate, driving conditions and use intensity across the country. Batteries in hot southern provinces degrade faster than those in cooler northern regions, and the duty cycles of ride-hailing fleets in megacities differ sharply from those of private cars in smaller urban areas. By overlaying these regional degradation patterns on dynamic material flow models, the researchers could track how lithium, cobalt and nickel circulate through the Chinese fleet year by year, distinguishing between material locked in operating vehicles, material awaiting recycling and material returning from the scrap stream.

Dynamic material flow analysis, the methodological backbone of the study, treats the vehicle fleet as a kind of reservoir of embodied metals. Batteries enter that reservoir at manufacturing and exit at end of life, where they can either be recycled back into the production loop or diverted into second-life storage before eventual recovery. The timing of these flows determines whether a closed-loop system, in which recycled material fully satisfies new battery demand, arrives in time to relieve mining pressure. The study maps the conditions under which China’s battery system achieves that closed loop, and finds that degradation assumptions shift the timing substantially. Shared mobility with fast-degrading NMC811 packs floods the recycling pipeline earlier but with a much larger total volume of batteries that must be replaced, while durable chemistries slow the flow but reduce cumulative demand overall.

The findings carry immediate relevance for policy and industry strategy, both in China and beyond. China’s Ministry of Industry and Information Technology has already established standards for the comprehensive utilisation of waste electric vehicle batteries, and the country’s dominance in lithium-ion battery recycling gives it a head start on circular supply chains. But this study suggests that policy cannot treat recycling, second-life deployment, battery chemistry selection and mobility models as independent levers. A fleet-planning decision as mundane as whether ride-hailing vehicles use lithium iron phosphate or NMC811 cells propagates through decades of material demand, recycling capacity needs and import dependence. The authors argue that accounting for battery degradation is therefore critical to aligning shared mobility, battery choice and circular strategies with transport decarbonization goals.

There is also a broader lesson about how the clean energy transition is modelled. Life cycle assessments and material demand projections frequently rely on static assumptions about product lifetimes, an approach that is computationally simpler but can misrepresent systems in which usage intensity fundamentally alters durability. The battery community has made rapid progress on the science of degradation, from physics-based ageing models to machine-learning approaches that can predict cycle life from early discharge data, and this study demonstrates how powerful it is to embed that understanding directly into resource assessments. The same logic likely applies to other heavily used clean technologies, from grid-scale storage batteries to hydrogen fuel cells in commercial fleets, where duty cycles differ dramatically from laboratory baselines.

For consumers and investors watching the electric vehicle market, the takeaways are tangible. Durable chemistry choices, thoughtful thermal management and realistic usage projections all shape how much mining the mobility transition ultimately requires. Shared mobility remains a valuable tool for cutting emissions and materials demand, but the new analysis makes clear that it is not automatically a resource panacea. Whether car sharing delivers its promised material dividend depends on batteries that can endure the punishing schedules of shared fleets, on recycling systems timed to collect retired packs without unnecessary detours, and on planners who treat degradation not as an afterthought but as a first-order variable in the circular economy of transport.

Subject of Research: Material demand and circularity implications of battery degradation in shared electric mobility in China

Article Title: Material circularity implications of battery degradation in shared electric mobility

Article References: Yang, Q., Xu, G., Chen, W., Tong, D., & Cao, Z. (2026). Material circularity implications of battery degradation in shared electric mobility. Nature Sustainability. https://doi.org/10.1038/s41893-026-01969-7

Image Credits: AI Generated

DOI: 10.1038/s41893-026-01969-7

Keywords: shared mobility, battery degradation, lithium, NMC811, lithium iron phosphate, recycling, second-life batteries, material flow analysis, critical minerals, China, electric vehicles, circular economy

The new binder is built from remarkably humble ingredients: polyacrylic acid and carboxymethyl cellulose, two inexpensive and widely available polymers, crosslinked by citric acid, a common food-grade molecule. What makes this combination powerful is not any single component but the architecture of the network they form together. When the binder is cured, the citric acid creates covalent crosslinks between the polymer chains, while the abundant carboxyl groups along the polyacrylic acid backbone engage in hydrogen bonding with one another and form ionic interactions with the active electrode particles and the metal current collectors. The result is a three-dimensional network that integrates hydrogen, covalent, and ionic bonding simultaneously, a design that solves a long-standing problem in sustainable electrode engineering.

Previous attempts to replace PVDF have often turned to bio-derived binders that can be processed in water, an attractive proposition because water eliminates the need for toxic solvents and dramatically reduces processing costs. However, these bio-based alternatives typically depend on hydrogen bonding alone to hold electrodes together. Hydrogen bonds are individually weak and can break down under the mechanical stresses of battery operation or the harsh electrochemical conditions inside a cell, particularly at high voltages where oxidative degradation becomes a threat. The new crosslinked network overcomes this limitation by layering multiple bonding modes on top of one another. The covalent crosslinks provide permanent structural integrity, the hydrogen bonds offer energy dissipation and flexibility, and the ionic interactions anchor the binder firmly to both active particles and current collectors, delivering strong adhesion along with good oxidative stability and thermal stability.

To test the concept, the researchers fabricated positive electrodes using lithium iron phosphate, a cathode chemistry prized for its safety and longevity in electric vehicles and stationary storage. Electrodes made with the fluorine-free binder delivered an initial capacity comparable to control electrodes made with conventional PVDF, meaning the new binder sacrifices nothing in terms of how much energy the battery can store on first use. More strikingly, the fluorine-free electrodes exhibited better cycle stability than their PVDF counterparts, retaining their capacity more effectively over repeated charge and discharge cycles. This improvement likely stems from the robust multi-bond network, which better accommodates the volume changes and mechanical fatigue that electrodes experience during cycling, keeping active material particles connected to the conductive pathways that carry electrons in and out.

The versatility of the binder chemistry proved to be another key strength. The researchers showed that the same fluorine-free formulation applies to a wide range of both positive and negative electrode materials, suggesting that it is not a niche solution tailored to a single chemistry but a general-purpose platform that could be adopted across the battery industry. This breadth matters enormously for commercialization, because battery manufacturers produce many different electrode chemistries for different applications, and a binder that only worked for one material would offer limited value. A single binder system that works across the portfolio of lithium-ion technologies could simplify manufacturing lines and accelerate adoption.

Perhaps the most consequential finding of the study concerns what happens at the end of a battery’s life. Direct recycling, in which spent electrode materials are recovered and rejuvenated rather than broken down into their elemental constituents, is widely regarded as the most energy-efficient and environmentally friendly recycling pathway. Yet PVDF has been a persistent obstacle to direct recycling because its fluorinated structure generates harmful fluorinated residues during processing and complicates the separation of active materials from the binder matrix. The new fluorine-free binder dissolves this problem. Because it is water-processable and free of fluorine, the researchers were able to demonstrate full recovery of spent positive and negative electrodes, restoring the recovered materials to the same level of performance as pristine ones without generating any fluorinated waste.

The implications of this full-recovery demonstration extend beyond the laboratory. When the team performed a life-cycle analysis comparing batteries made and recycled with the new binder against those based on PVDF, the fluorine-free system showed significant reductions in both energy cost and emissions. This analysis captures the entire journey of the materials, from initial manufacturing through use and into recycling, and it reveals that the environmental benefits compound at every stage. Manufacturing in water instead of N-methyl-2-pyrrolidone saves energy and eliminates toxic solvent handling. Recycling without fluorinated residues avoids hazardous waste streams. And because the recovered electrode materials perform identically to pristine ones, they can re-enter the production loop indefinitely, closing the circle that conventional battery manufacturing leaves stubbornly open.

The research also benefited from sophisticated analytical capabilities. The team used beamlines at the National Synchrotron Light Source II, a U.S. Department of Energy Office of Science user facility operated by Brookhaven National Laboratory, to probe the structure and behavior of their binder system at the molecular level. Such advanced characterization is essential for understanding exactly how the hydrogen, covalent, and ionic bonds distribute themselves within the electrode and how they respond to the stresses of battery operation, knowledge that guides further optimization of the formulation. The work was supported in part by the ECS Toyota Young Investigator Fellowship, reflecting the strong automotive industry interest in sustainable battery technologies, and the researchers have filed a patent application related to the technology, a signal that they see a viable path toward commercial deployment.

What makes this advance resonate beyond the technical community is the elegant simplicity of the underlying idea. Rather than inventing exotic new materials, the researchers combined three inexpensive, well-understood substances in a way that exploits the full spectrum of intermolecular interactions. Polyacrylic acid and carboxymethyl cellulose are already produced at industrial scale for applications ranging from diapers to food thickeners, and citric acid is one of the most abundant organic acids in the world. This means the supply chains and processing knowledge needed to manufacture the binder at scale largely already exist, removing one of the most common barriers that laboratory discoveries face on the road to real-world impact.

As the world electrifies transportation and grids, the volume of lithium-ion batteries reaching end of life is projected to grow into the millions of tonnes per year, making recycling infrastructure not just an environmental nicety but an economic and strategic necessity. Binders have long been treated as a minor, almost invisible component of battery design, yet this study demonstrates that they sit at the very heart of the sustainability challenge, dictating how electrodes are made, how they perform, and how easily their valuable contents can be reclaimed. By replacing a fluorinated polymer and a toxic solvent with a water-based, fully recoverable alternative that actually improves cycle life, the researchers have shown that circularity and performance need not be trade-offs. If the technology scales as hoped, the batteries of the future may be born in water, live longer, and return intact to the factory floor, again and again.

Subject of Research: Fluorine-free polymer binders for sustainable manufacturing and direct recycling of lithium-ion battery electrodes

Article Title: Fluorine-free polymer binder enables circular manufacturing and recycling of lithium-ion batteries

Article References: Lin, J., Mu, A., Tang, W., Li, F., Zhu, Y., Li, M., Yeerella, R. H., Potts, C., Cai, S., Mu, L., Muldoon, J., & Chen, Z. (2026). Fluorine-free polymer binder enables circular manufacturing and recycling of lithium-ion batteries. Nature Communications. https://doi.org/10.1038/s41467-026-78215-3

Image Credits: AI Generated

DOI: 10.1038/s41467-026-78215-3

Keywords: lithium-ion batteries, polymer binder, PVDF, recycling, circular economy, water processing, polyacrylic acid, carboxymethyl cellulose, citric acid crosslinking, life-cycle analysis, lithium iron phosphate, sustainability

The research team constructed three-dimensional heterogeneous composite electrode models in which the active particles were represented as ellipsoids rather than the idealized spheres used in most classical battery theory. This choice matters, because real electrode particles are rarely perfect spheres, and their aspherical shapes can create nonuniform lithium intercalation patterns that simpler models miss entirely. Using a graphite–lithium iron phosphate system as a representative platform, the researchers simulated the discharge process under different microstructural scenarios, comparing electrodes built from particles of a single uniform size, known as monodisperse systems, with electrodes containing a mixture of small and large particles, known as bidisperse systems.

The simulations, which coupled the physics of ion transport in the electrolyte, electronic conduction, and solid-state diffusion within the particles, yielded a clear hierarchy of effects. The dominant factor controlling overall electrochemical performance turned out to be solid-phase diffusion limitation, the sluggishness with which lithium ions move inside the active material itself. This limitation becomes especially punishing in electrodes built from large particles, where lithium must travel farther to reach or leave the interior of each grain. In practical terms, a battery electrode crowded with oversized particles simply cannot keep up when the cell is asked to discharge rapidly, because the inner volume of each particle remains electrochemically stranded.

Perhaps the most striking insight from the work concerns the division of labor inside polydisperse electrodes, those containing a range of particle sizes. The simulations revealed that small particles dominate the initial stage of discharge, shouldering most of the electrochemical reaction while the cell is fresh and concentration gradients are shallow. As discharge proceeds, however, the large particles become increasingly active, gradually taking over the workload as the small particles approach their capacity limits. This temporal handoff between particle populations had been hypothesized before, but the new three-dimensional models quantify it with a clarity that earlier pseudo-two-dimensional approaches, which average away much of the microstructural detail, could not achieve.

The researchers went further, showing that the presence of small particles does more than simply add extra reactive surface area. Incorporating them actively modulates both the transport resistance through the porous electrode and the reaction kinetics at particle surfaces, thereby altering the entire pattern of mass transport during discharge. In other words, the microstructure does not merely scale performance up or down; it reshapes the way current and lithium flow through the electrode as a whole. This mechanistic understanding is precisely what electrode designers need, because it transforms particle size distribution from a manufacturing afterthought into a deliberate engineering lever.

One of the study’s most counterintuitive findings is that the relationship between the fraction of small particles and discharge capacity is not monotonic. Adding small particles initially boosts capacity, as their short diffusion paths and abundant surface area accelerate reaction kinetics. But beyond a certain point, further increases in the small-particle fraction cause capacity to decline again, likely because an excess of fine particles congests the pore network and impedes electrolyte transport through the electrode. The result is a curve that first rises and then falls, meaning there is a genuine optimum rather than a simple rule of thumb that more small particles are always better.

That optimum, the team reports, corresponds to a total volume fraction of 57.4 percent for the bidisperse system they studied. At this composition, the electrode achieves the best balance between kinetic enhancement, delivered by the small particles, and transport efficiency through the available pore space. This kind of quantitative design target is rare in battery microstructure research, where guidance often remains qualitative. For manufacturers, a number like this offers a concrete starting point for tuning slurry formulations and calendering processes, the industrial steps that ultimately fix the particle arrangement inside a commercial electrode.

The study focuses on thin-electrode configurations, and the authors are careful to frame their conclusions within that context. Thin electrodes, in which ions face relatively short tortuous paths through the porous matrix, are increasingly relevant for high-power applications where rate capability matters more than maximum energy density. The finding that solid-phase diffusion is the governing bottleneck in such geometries clarifies which design strategies are worth pursuing: reducing particle size or blending size classes attacks the true limiting step, whereas efforts focused solely on improving electrolyte-phase transport may yield diminishing returns in thin electrodes.

The work also sits within a broader movement in battery science toward microstructure-resolved modeling. Traditional pseudo-two-dimensional models, descended from the framework developed by John Newman and colleagues decades ago, treat electrodes as homogeneous continua and represent particles with averaged radii. While computationally efficient, such models can obscure the heterogeneity that modern imaging techniques, from X-ray nano-computed tomography to scanning electrochemical microscopy, have revealed inside real electrodes. By building fully three-dimensional heterogeneous models with realistic ellipsoidal particle shapes and explicit size distributions, the Jiangsu University team bridges the gap between what microscopes actually see and what simulations can predict.

The implications extend beyond the graphite–lithium iron phosphate chemistry used as the test platform. Because the governing physics of solid-state diffusion, interfacial reaction kinetics, and porous transport applies broadly across intercalation materials, the design principles extracted here, including the non-monotonic capacity trend and the existence of an optimal bidisperse composition, provide a theoretical foundation that can be adapted to other chemistries and electrode architectures. As demand grows for batteries that can charge in minutes and deliver high power without sacrificing longevity, studies like this one demonstrate that some of the most valuable improvements may come not from new chemistry, but from arranging familiar materials with new precision, one particle at a time.

Subject of Research: 3D multiphysics modeling of particle size distribution effects on lithium-ion battery electrode performance

Article Title: 3D multiphysics modeling and optimization of li-ion battery electrodes: effects of particle size and distribution

Article References: Wu, B., Wu, J.-C., Zhou, H., Gao, H., Deng, Y., Wang, T., Lan, H., & Wang, N. (2026). 3D multiphysics modeling and optimization of li-ion battery electrodes: effects of particle size and distribution. Ionics. https://doi.org/10.1007/s11581-026-07556-2

Image Credits: AI Generated

DOI: 10.1007/s11581-026-07556-2

Keywords: lithium-ion batteries, electrode microstructure, particle size distribution, 3D modeling, multiphysics simulation, solid-phase diffusion, graphite anode, lithium iron phosphate, rate capability, discharge capacity, bidisperse electrodes, electrochemical optimization

The research addresses a deceptively simple question: what actually happens to the cathode material inside a real, commercially manufactured cell as lithium ions are progressively extracted? Laboratory-scale studies of pristine electrode powders have long described the two-phase reaction mechanism of lithium iron phosphate, in which a lithium-rich olivine phase converts to an iron-rich delithiated phase as the battery charges. But commercial cells contain engineered particle coatings, conductive carbon networks, binders, and electrolyte decomposition products that can all blur or modify this textbook picture. By working with actual pouch cells rather than idealized half-cells, the team sought a multiparameter fingerprint of cathode evolution that reflects what first responders, forensic engineers, and battery safety analysts would encounter in the field.

The experimental design was straightforward but demanding. The researchers prepared identical commercial lithium iron phosphate pouch cells and brought each one to a different state of charge: 0, 25, 50, 75, 100, and 125 percent. The 125 percent condition deliberately pushed the cells into mild overcharge territory, a scenario relevant to charging faults, battery management system failures, and the abusive conditions that precede many real-world battery fires. Each cathode was then harvested and interrogated with three techniques that probe the material at different scales. X-ray diffraction revealed the bulk crystalline structure, X-ray photoelectron spectroscopy exposed the chemical states of elements at the particle surfaces, and inductively coupled plasma mass spectrometry quantified exactly how much lithium, iron, and phosphorus remained in the electrode.

The X-ray diffraction results traced a clear structural trajectory. As the state of charge increased, the diffraction intensity of the lithium-rich lithium iron phosphate phase declined overall, reflecting the progressive conversion of that phase into its delithiated counterpart as lithium ions were drawn out of the olivine framework. At the same time, the unit-cell volume of the material shrank, a consequence of removing lithium from the crystal lattice and the accompanying contraction of the phosphate structure. These observations confirm that the fundamental two-phase transformation operates as expected inside commercial cells, but they also establish a quantitative baseline: the ratio of the two phases, and the lattice dimensions themselves, encode how deeply the cell was charged.

The surface-sensitive X-ray photoelectron spectroscopy measurements added a second, independent layer of evidence. The fraction of the iron signal attributable to trivalent iron — the oxidation state characteristic of the delithiated, charged phase — rose steadily as the state of charge increased, climbing from 53.02 percent in the fully discharged cell to 63.74 percent at the highest charging level examined. Because XPS samples only the outermost atomic layers of the cathode particles, this measurement captures the surface chemistry where side reactions with the electrolyte occur first. A systematic shift in surface iron oxidation state with charging level suggests that the cathode surface carries a readable record of its electrochemical history, one that survives even after the cell has been cooled, opened, and examined.

Inductively coupled plasma mass spectrometry supplied the third pillar of the analysis, delivering bulk elemental composition with exquisite sensitivity. The lithium content of the cathode material fell continuously as the state of charge rose, exactly as the extraction of lithium ions during charging would predict. More intriguing was the behavior of iron and phosphorus, which did not follow a simple monotonic trend but instead varied in a non-uniform way across the charging series. This non-monotonic element migration hints at subtle redistribution processes — possibly involving dissolution, surface reconstruction, or interaction with decomposition products — that a single-technique study would have missed entirely. The combination of a predictable lithium decline with an irregular iron and phosphorus pattern illustrates why the authors argue that no single measurement can reliably characterize a cathode’s history.

The most dramatic findings emerged from the 125 percent overcharge sample, which displayed a constellation of mild overcharge signatures. Fluorine-related signals in the spectroscopic data weakened, weak sodium and sulfur peaks that appeared at other charging levels disappeared, and the cell itself showed physical swelling accompanied by gas generation. These observations paint a picture of an electrolyte under stress: as the cell is pushed past its designed capacity, parasitic reactions begin to consume and transform the fluorinated species of the electrolyte, volatile products accumulate, and trace contaminants are displaced from the electrode surface. For battery forensics, such signatures are potentially invaluable, because they distinguish a cell that was merely fully charged from one that was driven into abusive overcharge before failure.

The implications extend well beyond the laboratory. Micro-mobility vehicles — electric bicycles, scooters, and similar lightweight machines — have been repeatedly implicated in urban battery fires, often in charging cabinets and residential settings where cells may be charged with mismatched equipment or beyond their rated limits. The state of charge is well known to influence how violently a lithium-ion cell fails thermally, with highly charged cells releasing more energy and generating more combustible vent gas. By establishing how cathode crystallinity, surface oxidation states, and elemental composition shift systematically with charging level, this work lays a preliminary scientific foundation for post-incident analysis: an investigator examining cathode debris could, in principle, reconstruct whether the cell was empty, full, or overcharged at the moment of failure.

The authors are careful to frame their results as a starting point rather than a finished forensic toolkit. The study examined cells from a single manufacturer in a defined state of health, and the samples were prepared under controlled laboratory conditions rather than recovered from actual fire debris, where heat, soot, and water from suppression efforts could alter the very signatures the technique relies upon. Validation across different cell makers, aging histories, and realistic post-fire environments will be required before the method can support quantitative conclusions in accident investigations. The researchers also emphasize that their findings provide a multiparameter basis — combining diffraction, spectroscopy, and elemental analysis — rather than a single decisive test, reflecting the inherent complexity of real battery materials.

Even with those caveats, the study marks a meaningful step toward treating spent battery cathodes as data-rich evidence rather than charred debris. The idea that a crystal lattice’s contraction, a surface’s oxidation balance, and a trace element’s wanderings can together narrate a cell’s charging history speaks to a broader shift in battery science: from designing materials that store energy to understanding everything those materials remember. As lithium iron phosphate continues its global expansion into vehicles, storage systems, and countless portable devices, techniques that can read the electrochemical past written into its structure may become as essential to safety engineering as the batteries themselves are to modern technology. The work was supported by the Key Laboratory of Electrochemical Energy Safety under the Ministry of Emergency Management and by a key research special project of the China People’s Police University, underscoring the growing institutional investment in battery accident investigation science.

Subject of Research: Crystalline phase transition and element migration in lithium iron phosphate cathodes of commercial pouch cells at different states of charge

Article Title: Crystalline phase transition and element migration in cathode materials of commercial lithium iron phosphate pouch cells at different state-of-charge levels

Article References: Zhang, C., Mei, Z., Pei, Y., Liu, X., Geng, X., Wang, H., Xu, C., & Feng, X. (2026). Crystalline phase transition and element migration in cathode materials of commercial lithium iron phosphate pouch cells at different state-of-charge levels. Ionics. https://doi.org/10.1007/s11581-026-07552-6

Image Credits: AI Generated

DOI: 10.1007/s11581-026-07552-6

Keywords: lithium iron phosphate, lithium-ion batteries, state of charge, cathode materials, X-ray diffraction, X-ray photoelectron spectroscopy, ICP-MS, overcharge, battery safety, thermal runaway, battery forensics, micro-mobility