Beyond the Grid: 700 Wh/kg Lithium-Metal Battery Cell Technology and My Personal Reflections

I am finalising this article from the departure lounge at Izmir Adnan Menderes Airport, heading back from a visit to my parents. There is something about returning to Türkiye, the country where I was born and where my engineering journey began, that makes me reflect on the progress we have achieved.

A Personal Prologue: From Izmir to 700 Wh/kg

About twenty-five years ago, fresh out of university, I joined the research group of Prof. Dr. Nejat Tuncay. He was, and remains, a truly visionary man, a guiding light whose impact reached hundreds of young engineers like me. Under his leadership, my very first professional assignment was to design and develop the energy storage solution for the first electric vehicle, in serial hybrid powertrain form, developed in Türkiye, quite possibly one of the first anywhere in the world.

To put that into perspective, the battery pack I designed and built consisted of thirty 12V, 50Ah lead-acid batteries connected in series. If my memory serves well, the whole thing weighed around 360 kilograms. Three hundred and sixty kilograms of lead and acid, just to store a modest amount of energy that a modern EV battery a fraction of its size would easily surpass. The idea of electrifying anything beyond a small prototype felt like a beautiful, stubborn act of defiance against the physics of energy density. Prof. Tuncay taught us to see beyond the limitations of today and engineer for the possibilities of tomorrow.

I was fortunate enough to pursue that belief into a career. My lifelong passion for motorsport and my profession came together in the most extraordinary way. I became one of the engineers developing the battery pack for the first Formula 1 Grand Prix-winning hybrid power unit. I then went on to architect the battery pack that powered the first generation of Formula E racing cars, and I have developed various battery solutions across passenger and commercial vehicle segments along the way.

A lot has been written about that first generation Formula E pack over the years, but there is one reality that very few people have touched on. It was the only structural battery pack ever to power a Formula racing car. The pack was not simply a component bolted into the chassis; it was the chassis. It was the structural building block of the racing car itself, holding the tub at the front and the powertrain at the back. For a mechanical engineer, it was an Achilles' heel of the most exciting kind: every energy density figure, every Wh/kg metric quoted for that pack, must carry the footnote that this battery was simultaneously a load-bearing structural member of a racing car and required additional mechanical components to maintain its structural integrity.

And here is a fact that, to my knowledge, no one has ever publicly mentioned: that structural battery pack passed a formal crash test under live conditions in a lab environment in Italy, and was then proven in the real world at the last corner of the very first FIA Formula E race ever held in Beijing, China, a few months later. It did exactly what it was designed to do.

Today, at Williams Grand Prix Technologies, I am privileged to work alongside a brilliant team of engineers and business professionals as we push to disrupt yet another sector with our battery technology. More on that will be coming later this year.

I should be honest about something. Throughout my career, I have never pursued electrification because of sustainability targets. I pursued it because electric powertrains are better. Faster torque response, higher precision, more elegant packaging, fewer moving parts. I grew up as a member of the Star Wars generation, educated on the sound of the future, so it was just normal to me. When you have spent years designing power systems for racing cars, you learn to follow the physics, and the physics points to electric. The environmental benefit is real, and I welcome it, but it was always a byproduct of chasing performance while playing the long game. I think that distinction matters, because the strongest case for electrification is not that we should do it. It is that it simply works better. Now many people feel that exhilarating surge of acceleration in their own electric vehicles, at a much lower cost than a fast combustion car.

So when my regular AI research flagged a lithium-metal battery paper published in Nature on 25 February, I started digging in. I have a few work processes that use AI to regularly scan the technology landscape, filtering the noise and surfacing what matters. The results are usually hit-and-miss, and the process so far warrants a human-in-the-loop approach. So I pick up the output and start reading, searching further when something captures my interest. I was reading about this on the 26th. That speed of awareness, from journal publication to my screen in under 24 hours, is itself a sign of how much the world has changed.

What I found out was that a 711.3 Wh/kg lithium-metal cell was not entirely new. Chinese researchers at the Institute of Physics in Beijing first demonstrated that energy density figure in a laboratory setting back in 2023. What matters is that researchers at Nankai University have now published in Nature with a practical electrolyte solution that addresses the key barriers to real-world use, specifically dendrite formation, cycling stability, and temperature tolerance. That is the difference between a laboratory proof of concept and a credible pathway to manufacturing.

For those of you who like to learn more about challenges particularly around solid-state battery technology, I had come across this excellent blog post from QuantumScape when I was preparing for an executive review meeting about 5 years ago now. Some of the concepts and challenges highlighted are transferable for further learning.

Solid-State Battery Landscape — QuantumScape

I do not process a headline like 700 Wh/kg as an abstract number. I process it against the physical memory of wiring battery modules that weighed a small fortune and delivered a fraction of what we needed. I process it against twenty-five years of hard-won gains in energy density, each one expanding the horizon of what electrification could reach.

The Uncoupling of Power and Infrastructure

For decades, the industrial world has operated under a split energy model. Stationary environments, manufacturing plants, assembly lines, heavy processing facilities, have long relied on electric machines. I still remember my internship summer at an iron ore factory in Izmir, where electric motors ran everything on the factory floor with a precision and reliability that combustion engines could not possibly match. The reason is simple: stationary facilities are connected directly to the electrical grid, giving them access to uninterrupted, highly controllable power.

Bringing this electric advantage to mobile applications, however, has always been a major engineering challenge. Vehicles, construction machinery, and agricultural equipment are not connected to any grid. They are limited by the amount of energy they can carry on board. This single constraint made liquid fuels, mainly diesel and petrol, the dominant energy source for mobile industries. Fossil fuels offer a very dense way to store chemical energy, allowing machines to operate for long periods far from any power connection. But this reliance on combustion comes with poor system efficiency, high mechanical complexity, and serious environmental costs.

Over the past four decades, advances in electrochemical storage have steadily begun to challenge the internal combustion engine, but the progress has been defined by hard-won gains. Moving from early chemistries to advanced lithium-ion designs has enabled the electrification of passenger vehicles and light commercial transport. Yet heavy-duty applications, agricultural combine harvesters, long-haul freight, mining trucks, have remained largely out of reach. These machines demand punishing duty cycles at higher power levels that traditional lithium-ion batteries cannot meet without sacrificing payload or range or total cost of ownership or simply packaging space.

A Journey Measured in Watt-Hours Per Kilogram

Over the span of my own career, I have witnessed battery pack energy densities grow from a modest 30 Wh/kg to over 200 Wh/kg. Discussing 700 Wh/kg at the cell level is, frankly, incredibly exciting.

The 1980s were dominated by lead-acid and nickel-cadmium systems, heavy, toxic, and hopelessly energy-poor. Sony's commercialisation of the first lithium-ion battery in 1991 changed that, and by the time I was building my first EV pack in the workshop, the horizon had genuinely opened up. I must recognise that having access to advanced tech from a developing country was not fully in our control, hence our humbling start. Through the 2000s and into the 2010s, new cathode chemistries pushed energy densities past 200 Wh/kg, moving the battery-electric passenger vehicle from niche prototype to commercial reality. Over that thirty-year arc, cell costs fell by roughly 99 percent while top-tier energy density increased fivefold. Today, top-tier commercial lithium-ion cells have reached 250 to 350 Wh/kg, approaching the theoretical ceiling of the graphite anode architecture. Breaking through 400 Wh/kg and reaching the applications that remain out of reach, electric aviation, heavy agriculture, demands a chemistry change. That means moving to pure lithium metal.

For those who want to explore the current commercially available cell landscape in detail, I would point them to one of my favourite UK battery businesses, About:Energy. They also help bridging model world with real world data. For me, About:Energy is to battery cells what Artificial Analysis is to AI models — an indispensable reference point.

It is also worth noting that lithium-metal is not the only alternative chemistry gaining ground. On the lower cost spectrum, sodium-ion has come remarkably far since my early hands-on experiments with it in the 2010s, when it was promising on paper but nowhere near ready for use. Nevertheless, we built a bicycle demonstrator. I thought it was the end for that technology. One of my many incorrect calls! CATL's Naxtra cell now achieves 175 Wh/kg at a fraction of the cost and without any dependence on lithium supply chains, and their next generation is targeting 200 Wh/kg. The battery landscape is broadening, with different chemistries serving different applications, and the pace of that diversification is accelerating.

The 700 Wh/kg Breakthrough: What They Actually Did

The headline energy density figure of 711.3 Wh/kg was first demonstrated in 2023 by researchers at the Chinese Academy of Sciences in Beijing. Their work, published in Chinese Physics Letters, proved the number was real. But the team were candid about what remained unsolved: the chemistry was unstable, the cell degraded quickly, and the pathway to a real product was far from clear.

The 2026 Nature paper from Nankai University is what changes that picture. The Beijing team proved how much energy you could store. The Nankai team solved how to keep the cell alive long enough to be useful.

The core problem with lithium metal batteries has always been the electrolyte, the medium that carries charge between the electrodes. Lithium metal reacts aggressively with conventional electrolytes, corroding from the inside with every charge cycle, and growing microscopic metallic needles called dendrites that can pierce the internal separator and cause a short circuit. This is why the chemistry has been tantalising but impractical for decades.

What Zhao Qing and Academician Chen Jun's team achieved was a new class of electrolyte molecule that stabilises lithium metal without sacrificing conductivity, a combination the industry had been chasing for years. The result is a cell that can charge and discharge repeatedly without the internal degradation that previously made this chemistry unworkable outside the laboratory.

That is the distinction that matters. This is no longer just an impressive number. It is a credible engineering pathway.

Thermodynamics and Driveline Efficiency: The Real Comparison

When evaluating whether a 700 Wh/kg battery is commercially viable for heavy machinery, it must be compared against diesel fuel. This is where the conversation gets really interesting, because the raw numbers are deeply misleading. I have been quite vocal on misrepresentation of these figures openly at various conferences and workshops and I will carry on doing so.

On a raw chemical basis, diesel fuel contains roughly 12,000 Wh/kg, or 45.5 MJ/kg. Comparing a 700 Wh/kg battery cell to 12,000 Wh/kg of diesel suggests batteries are disadvantaged by a factor of roughly 17 to 1. On paper, it seems impossible for electric power to compete.

However, raw energy density is a deceptive metric. What actually matters in mobile applications is not the chemical energy stored in the tank, but the useful work delivered to the wheels or implements. This requires an honest accounting of thermodynamic limits and conversion efficiencies.

The Inefficiencies of Combustion

An internal combustion engine is a heat engine governed by the Carnot cycle, which sets the maximum theoretical efficiency based on temperature differences. Because of these laws of physics, the combustion engine is inherently wasteful. Energy is lost as heat through the exhaust. More energy must be removed through the cooling system to prevent overheating. Further energy is consumed by internal friction, pumping losses, and auxiliary systems.

A well-optimised heavy-duty diesel engine reaches a peak thermal efficiency of about 40%. In real field conditions, especially under variable loads or during idle periods, average efficiency is often much lower. Even at the best case of 40%, this means 60% of the 12,000 Wh/kg is wasted as heat and friction before reaching the transmission output shaft. The actual usable work from one kilogram of diesel is reduced to a maximum of 4,800 Wh/kg.

The Efficiency of Electric Drive

Battery-electric drivetrains bypass the thermodynamic limits of heat engines altogether. Converting stored electrochemical energy into electrical current, and then into mechanical rotation via an electric motor, is a very direct and efficient process. I graduated from Istanbul Technical University Electrical Engineering Department with a speciality on electric machines and power electronics. Some may call me biased but I kept developing electric drives for vehicles and racing cars throughout my career as an engineer and as a leader. As a propulsion unit, there is no comparison between the precision, responsiveness and efficiency of an electric drive and an engine.

Modern electric motors routinely achieve efficiencies of 90% or higher. Including minor losses in the battery's internal resistance and the power inverter, the overall battery-to-wheel efficiency remains very high, typically 80% to 85%. Electric drives can also recover energy through regenerative braking, capturing kinetic energy that would otherwise be lost as heat in conventional brake pads.

At the cell level, 700 Wh/kg is the headline figure. But a realistic cell-to-pack ratio of approximately 80% must be applied to account for the structural housing, thermal management, bus bars, and battery management electronics. This gives a pack-level energy density of approximately 560 Wh/kg. Applying the 85% driveline efficiency then delivers approximately 476 Wh/kg of precise, usable mechanical work.

The Narrowing Gap

The gap is no longer 17 to 1. It is 4,800 Wh/kg of usable diesel energy versus roughly 476 Wh/kg of usable electric energy at the pack level. The ratio falls to approximately 10 to 1.

A full system comparison must also include the hardware needed to convert the energy. A diesel powertrain needs a heavy cast-iron engine block, multi-speed gearbox, catalytic converters, radiators, turbochargers, and exhaust systems. Electric motors are vastly smaller, simpler, and lighter. To show just how far electric machine technology has come, consider what YASA has recently achieved with its axial flux motor. Their latest prototype weighs just 12.7 kilograms and delivered a peak output of 750 kW, over 1,000 bhp, setting an unofficial world record power density of 59 kW/kg. That is roughly three times the performance density of the leading radial flux motors available today. When you pair energy storage at 700 Wh/kg with electric machines at this level of power density, the total system mass advantage of electrification becomes compelling. When you compare the total mass of energy storage plus conversion hardware, the weight penalty of a high-density battery system becomes entirely manageable for heavy commercial and agricultural applications.

Agricultural Combine Harvesters: The Ultimate Stress Test

To ground this in reality, consider one of the most demanding applications currently running on diesel. The agricultural combine harvester has one of the toughest duty cycles in industry. During peak harvest, these machines must run continuously for 12 to 14 hours and maybe more a day, processing thousands of tonnes of dense crop material under extreme dust, vibration, and heat.

If a 700 Wh/kg battery can meet the demands of agriculture, it can meet virtually any mobile industrial application.

The Compound Losses of Mechanical and Pneumatic Drives

A traditional combine harvester is not a single machine but a complex factory on wheels. It must cut the crop via the header, feed the material into a threshing drum to beat the grain from the stalk, use straw walkers to further separate the material, and deploy cleaning shoes and high-power blowers to separate chaff from clean grain.

All of this power comes from a single large diesel engine, routed through a network of mechanical belts, chains, hydrostatic pumps, and pneumatic blowers. Pneumatic systems are notoriously inefficient, frequently operating at 50% efficiency or less when converting prime mover energy into useful work. The diesel engine at 40% thermal efficiency, followed by pneumatic or belt drives at 50% efficiency, gives a total system efficiency of just 20%. The 12,000 Wh/kg of raw diesel energy is reduced to only 2,400 Wh/kg of actual useful work on the crop. The rest is lost to heat, noise, and friction.

The Distributed Electric Drive Solution

High-density battery technology enables a complete redesign. Instead of one diesel engine driving inefficient belts and pneumatic pumps, an electric combine can use distributed electric drives. Individual, highly efficient electric motors sit directly at each point of load: one for the cutting header, another for the threshing drum, independent variable-speed motors for the cleaning fans and grain augers.

Replacing a 50% efficient pneumatic drive with a 90% efficient direct-drive electric motor eliminates the compounding losses. Applying the same efficiency pathway established in the thermodynamics section, the pack-level figure of approximately 476 Wh/kg holds. Comparing 2,400 Wh/kg from the diesel-pneumatic system to 476 Wh/kg from the battery-electric system gives a practical energy ratio of roughly 5 to 1. Given that modern combine harvesters regularly exceed 15 to 20 tonnes, designing a chassis to carry this volume of advanced batteries is entirely feasible. The battery pack can even be placed in the lower chassis to lower the centre of gravity, improving stability on uneven ground.

Overcoming Operational Constraints

Proving the numbers on paper is only the first step. Agriculture demands that machinery runs almost non-stop during short, weather-dependent harvest windows. A combine cannot sit idle for hours to recharge mid-harvest.

The solution lies in high-capacity mobile energy buffers and Megawatt Charging Systems (MCS), capable of delivering power well above 1 MW. An electric combine can top up its battery during naturally occurring pauses, for example the frequent stops to unload its grain tank into a chaser bin. Fleet operators will use mobile Battery Energy Storage System (BESS) trailers brought directly to the field edge, drawing power slowly from the rural grid overnight and acting as rapid charging hubs during the harvest day. This "Charging-as-a-Service" approach effectively separates the harvester's high-power needs from the low-power capacity of the rural grid.

Electrification as the Enabler of Autonomy

In racing, we learned that the precision of electric power delivery is not just convenient, it is a competitive advantage. The ability to adjust torque in milliseconds, to recover energy under braking, to redistribute power across systems instantly, these capabilities transformed what the car could do. The same principles apply to agricultural machinery, only the stakes are arguably higher, because the output is food, not trophies.

Electric drives are controlled digitally by inverters and respond in milliseconds. A fully electric combine allows its computer to adjust the speed of the header, threshing drum, cleaning shoe, and wheels independently and instantly. If sensors and AI detect denser, wetter crop entering the header, the computer can immediately speed up the threshing drum while slightly reducing ground speed. Mechanical, hydraulic, and pneumatic systems simply cannot respond at this speed.

This is the point that I think deserves more attention than it currently receives. Automation and autonomous operation are already a central research focus in Agritech, with or without electrification. But the relationship between the two technologies is not neutral. As autonomous systems become more capable and more commercially compelling, the demand for the precise, digitally controllable power delivery that only electric drive can provide will intensify. Autonomy does not simply benefit from electrification. It actively accelerates the case for it, even in the most demanding applications where combustion once seemed irreplaceable.

Pairing electric platforms with autonomous navigation also removes the human fatigue factor. No operator can maintain perfect focus across a twelve-hour harvest shift. Autonomous electric harvesters, guided by GPS and sensor fusion, can operate around the clock, returning to a charging point at the field edge, topping up during a natural pause, and resuming without human intervention. The logic is not far removed from the robotic vacuum cleaner that quietly recharges itself before finishing the job, except the stakes, and the machine, are considerably larger.

I have a few highly experienced innovators in my network in this field, and I am sure they will point out challenges I have not covered here. Total cost of ownership, soil compaction, and tough logistics operations have been the key ones I learned during my earlier years at CNH Industrial. There are many problems on earth that need engineers to solve, and increasingly those engineers will solve them not by being replaced by AI but by using it as another tool in their hands.

Pragmatic Optimism

I use this phrase deliberately, because it reflects how I have learned to approach every major technology shift in my career, one may say in a hard way. I often describe this in my talks as the convergence of technological and commercial readiness.

The 700 Wh/kg lithium-metal cell is proven in the laboratory, and the efficiency maths clearly favour electrification. But moving this chemistry into mass production requires honest assessment of the industrial challenges ahead.

Scaling global production of this technology will require billions in capital investment. Manufacturing timelines and cost structures are still evolving. Early versions will carry a premium price, initially limiting use to high-value sectors like electric aviation or defence before economies of scale bring costs down for agriculture.

Proving the long-term cycle life of these cells under the punishing vibration and heat of heavy farm machinery will also take time. While the new electrolytes show strong promise, the degradation behaviour of lithium metal must be validated outside the laboratory. Fleet operators, whose livelihoods depend on absolute equipment reliability during a short harvest window, will need extensive field testing before committing to replace their diesel machines.

Despite these near-term hurdles, the broader direction is clear. The historical barriers of battery weight and range are being systematically broken down by breakthroughs in materials science. When the practical, efficiency-adjusted energy density of a battery pack approaches the usable output of a diesel engine, the advantages of electric drive become hard to argue against. Electric machines are far simpler mechanically. They need a fraction of the maintenance, with no oil changes, no exhaust after-treatment, and far fewer moving parts. They run with high precision, drastically cut local noise and particulate pollution, and integrate naturally with the digital systems needed for autonomous control.

Looking Forward: A Personal Conviction

The path to electrifying our most demanding mobile applications is no longer blocked by physics. It is now a clearly mapped process of scaling up chemistry and manufacturing. The foundational technology is moving fast.

Twenty-five years ago, in a laboratory in Gebze, I helped wire together battery modules for what was, at the time, a radical experiment: an electric vehicle in a country where the concept barely existed. The cells were heavy, the range was modest, and the sceptics were plentiful. Since then, I have had the privilege of applying the same principles to Formula 1 hybrid power units, to the first generation of Formula E, to passenger and commercial vehicles, and now to the work we are doing at Williams Grand Prix Technologies to push these boundaries further still.

I am looking forward, with great hope, to seeing the day when there are no more sectors that would benefit from electrification but have not yet been reached. I believe that day will come within my lifetime, hoping that I have still 20 years mileage left! The evidence shows that, eventually, most combustion-based systems, from the smallest passenger car to the heaviest combine harvester, will run on electricity. This transition will complete the evolution of power, moving the efficiency and precision of the connected factory floor out into the open field.

The journey from 30 Wh/kg to 700 Wh/kg has been extraordinary. And we are not finished yet.

Speaking of new eras, the 2026 FIA Formula 1 season starts next Sunday in Melbourne. This is not just another season. The new regulations bring 100% sustainable fuel powered engines with a full hybrid architecture, where the electric power contribution is now roughly equal to the combustion side. For someone who came up through motorsport battery engineering, this regulation change feels less like a news item and more like the closing of a chapter I helped to write.

As a proud member of the Williams Group, I am extremely excited. I would like to congratulate everyone at the Atlassian Williams F1 Team ahead of the season for their courage, resilience, and determination to carry on competing on the world stage. Here is to a great season ahead.

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Selin Aria Tur | Managing Director & CTO, Williams Grand Prix Technologies

About the Author

Selin Aria Tur is Managing Director and Chief Technology Officer at Williams Grand Prix Technologies. She has spent twenty-five years developing battery and electrification systems across Formula 1, Formula E, passenger and commercial vehicle applications. She has since expanded her engineering horizon to the technologies driving automation and autonomous systems, applying the same performance-first rigour she developed in motorsport to some of the most demanding real-world challenges in industry today.

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References

1. CarNewsChina, "New Breakthrough in Lithium Battery Technology Enables 700 Wh/kg Energy Density," 26 February 2026. Link
2. Li, Q., Yang, Y., Yu, X., Li, H., Chinese Physics Letters (2023). Link
3. Zhao, Q., Chen, J. et al., Nature (2026). Link
4. YASA Limited, "YASA smashes own unofficial power density world record," 22 October 2025. Link
5. CATL confirms 2026 large-scale sodium-ion battery deployment, CarNewsChina, 29 December 2025. Link
6. About:Energy, Voltt Cell Library. Link
7. QuantumScape, "Solid-State Battery Landscape," February 2021. Link

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Disclaimer: I am a technologically curious engineer, and that curiosity extends to every part of my working and personal life, including how I research and write. In producing this piece, I have made use of various AI tools, namely Perplexity, Anthropic Claude, Google Gemini, OpenClaw and Notion. What those tools cannot provide, however, is the more than ten hours I spent deep-diving the subject matter, drafting, and editing, nor the two decades of engineering experience and personal memoir that I hope give this writing its texture. My aim is that the reader leaves having learnt something, thought about something, and perhaps been entertained along the way. I hold my strong views loosely and recognise change of opinions as part of learning and growth journey.

© 2026 Selin Aria Tur. Licensed under CC BY 4.0. Reuse allowed with credit.

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This article was originally published on LinkedIn on 1 March 2026.