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