To extend a lithium-metal EV battery’s life, just drain it and let it sit, find Stanford scientists
Stanford University researchers found that the best way to extend the life of a lithium-metal EV battery is to drain it and let it rest for a few hours.
The study, “Resting restores performance of discharged lithium-metal batteries,” published on February 7 in the journal Nature, found that this straightforward approach restored battery capacity and boosted overall performance.
Study co-lead author Wenbo Zhang, a Stanford PhD student in materials science and engineering, said:
We were looking for the easiest, cheapest, and fastest way to improve lithium metal cycling life.
We discovered that by resting the battery in the discharged state, lost capacity can be recovered and cycle life increased.
These improvements can be realized just by reprogramming the battery management software, with no additional cost or changes needed for equipment, materials, or production flow.
The study results could provide EV manufacturers with practical insights into adapting lithium metal technology to real-world driving conditions.
Lithium-metal batteries could double the range of EVs, but they rapidly lose their capacity to store energy after just a few cycles of charging and discharging, rendering them useless for routine driving.
A conventional lithium-ion battery consists of two electrodes – a graphite anode and a lithium metal oxide cathode – separated by a liquid or solid electrolyte that shuttles lithium ions back and forth.
In a lithium-metal battery, the graphite anode is replaced with electroplated lithium metal, which enables it to store twice the energy of a lithium-ion battery in the same amount of space. The lithium-metal anode also weighs less than the graphite anode, which is essential for EVs. Lithium-metal batteries can hold at least a third more energy per pound than Li-ion batteries.
When a lithium-metal battery is discharged, micron-sized bits of lithium metal become isolated and trapped in the solid electrolyte interphase (SEI). This spongy matrix forms where the anode and electrolyte meet.
“The SEI matrix is essentially decomposed electrolyte,” Zhang explained. “It surrounds isolated pieces of lithium metal stripped from the anode and prevents them from participating in any electrochemical reactions. For that reason, we consider isolated lithium dead.”
Repeated charging and discharging results in the build-up of additional dead lithium, causing the battery to lose capacity rapidly. So, an EV with a lithium-metal battery would lose range much faster than a Li-ion-powered EV.
Drain it and let it sit
Previous research at Stanford found that the SEI matrix begins to dissolve when the battery is idle. Based on that finding, the researchers conducting this study decided to see what would happen if the battery was allowed to rest while discharged.
They completely discharged the battery so it had zero current running through it and found that if the battery rests in the discharged state for just an hour, some of the SEI matrix surrounding the dead lithium dissolves away.
When the lithium-metal battery is recharged, the dead lithium will reconnect with the anode because there’s less solid mass in the way. Reconnecting with the anode brings dead lithium back to life, enabling the battery to generate more energy and extend its cycle life.
The research team initially thought the energy loss was irreversible, but using time-lapse video microscopy, they found that lost capacity could be recovered simply by resting the discharged battery.
IRL application
The average driver in the US spends about an hour behind the wheel each day, so resting a car battery for several hours isn’t out of the question.
A typical EV may have 4,000 batteries arranged in modules controlled by a battery management system. In a lithium-metal battery, an existing management system can be programmed to discharge an individual module entirely so that it has zero capacity left.
Zhang said:
You can implement our protocol as fast as it takes you to write the battery management system code.
We believe that in certain types of lithium metal batteries, discharged-state resting alone can increase EV cycle life significantly.
Read more: Researchers achieve super-safe, ultrafast Li-ion battery charging
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Paris’ bike-share system, Vélib has long been considered one of the shining success stories of urban micromobility. With a massive fleet of over 20,000 pedal and electric-assist bicycles around Paris, the service has helped millions of residents and tourists get around the City of Light without needing a car or scooter. But lately, a growing problem is threatening to knock the wheels off this urban mobility marvel: theft and joyriding.
According to city officials and the service operator, more than 600 Vélib bikes are now going missing every single week. That’s over 30 bikes a day simply vanishing from the system – some stolen outright, others taken on “joy rides” and never returned.
“At the moment we’re missing 3,000 bikes,” explained Sylvain Raifaud, head of the Agemob company that currently operates the Velib system. That’s nearly 15% of over 20,000 Vélib bikes across Paris.
The sticky-fingered culprits aren’t necessarily professional thieves or organized crime rings. Instead, they’re often regular users who treat the shared bikes like disposable toys.
The city estimates that many people have figured out how to pry the bikes out of the system’s parking docks, unlocking one for a casual cruise and then ditching it somewhere far from a docking station.
Once pried free, the bikes are technically usable for the next 24 hours until their automatic locking feature kicks in. At that point, the bikes are often simply abandoned. Some end up in alleyways. Others get tossed in rivers. A few just disappear completely.
And since the bikes are intended to be parked at their many docking stations around the city, they don’t have GPS chips, further complicating recovery of “liberated” bikes.
The issue started small but has grown into more than an inconvenience – it’s beginning to undermine the entire purpose of the service. With bikes going missing at such a high rate, many Vélib docking stations are left empty, especially during rush hours.
Riders looking for a quick commute or a convenient hop across town are increasingly finding themselves without available bikes, or having to walk long distances to find a functioning one.
That kind of unreliability chips away at user confidence and threatens to drive potential riders back into cars, cabs, or other less sustainable forms of transport at a time when Paris has already made great strides to dramatically reduce car usage in the city.
The losses are financially painful, too. Replacing stolen or vandalized bikes isn’t cheap, and the resources spent on tracking down missing equipment or reinforcing anti-theft measures are stretching thin. Vélib has faced theft and vandalism issues before, especially during its early years, but this latest surge has officials sounding the alarm with renewed urgency.
Officials acknowledge that there’s no easy fix. Paris, like many cities with bike-share systems, walks a fine line between accessibility and accountability. Part of what makes Vélib so successful is its ease of use and widespread availability. But those same features make it vulnerable to misuse – especially when enforcement is limited and the consequences for abuse are minimal.
The timing of the problem is especially unfortunate. In recent years, Paris has seen impressive results in reducing car traffic, expanding bike lanes, and promoting cycling as a key part of its sustainable transport strategy. Vélib is a cornerstone of that plan. But if the system becomes too unreliable, it risks losing the very people it was designed to serve.
Meanwhile, as Parisians increasingly find themselves staring at empty docks, the challenge for the city and Vélib will be to restore confidence in the system without making it harder to use. That means striking the right balance between freedom and responsibility, between open access and protection against abuse.
In a city where cycling is supposed to be the future of mobility, losing thousands of bikes to joyriders and sticky fingers isn’t just frustrating; it’s unsustainable.
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