Chemistry lessons

Solid-state chemistry is also a much talked about battery technology, which in theory could revolutionise battery tech by replacing the liquid electrolyte with a solid. Outside of the laboratory, however, manufacturers are finding it less than robust in mass production and introduction dates are starting to creep over the event horizon. There are solid state scooters working on a test bench, but so far as car makers are concerned, the tech is still stuck in the same R&D department in which it has loitered for many years.

Then there’s the out-there tech which doesn’t even have a date or in some cases, work at all. File these into one of the two categories: aluminium-graphite, lithium-air and redox-flow batteries in one, and then batteries which aren’t really batteries at all such as graphene supercapacitors or even fuel cells.

So where are the big advances for the immediate future and how likely are they to be adopted? We asked the experts at the Faraday Institution.

The Faraday Institution is the UK’s principle programme for electro-chemical energy storage, research, skill development, market analysis and early commercialisation. Funded mainly by the government, it is based in Harwell, Oxfordshire, and its associated researchers work at the coal face of battery development.

EV batteries are described as having no moving parts, but they have hundreds of thousands of ions whizzing across the electrolyte and parking (or in cases slamming) into the cathode or anode when they are being driven or charged. Using different chemicals and materials for these electrodes affects the properties of the battery – how much energy it can store and its output, how much power it can provide or the number of times it can be discharged and recharged.

In a conventional Li-ion battery this charging and discharging process is reversible over many cycles and years, and furthermore Li-ion batteries carry more charge for less weight than alternatives such as state-of-the-ark lead acid or nickel-metal-hydride cells, hence their widespread use in the motor industry.

But as we have already seen, the charging/discharging process isn’t without consequence to battery health and longevity. Electrode materials are layered and they degrade.

As Serena Cussen, Chair in Functional Materials and Professor in Chemical and Biological Engineering at the University of Sheffield explained, ‘one can think of the cathode like sheets of stacked paper, in between which the lithium ions can slot. As the material undergoes multiple charge and discharge cycles, there are mechanical and chemical processes that can “weather” the cathode and lead to its degradation. These can take the form of rearrangement of atoms, volume changes and even particle cracking.’

There is also a process of degradation, where reactions between the electrodes and electrolyte can lead to trapped lithium ions, reducing the battery’s capacity and therefore its ability to hold a charge. And how you treat the battery, its temperature, the amount of fast charging and pressure in the cell will also affect its life.

Of all the battery components, it is the cathode which has arguably the strongest influence on a battery’s performance, safety and cost. As John-Joseph Marie, an energy analyst with the Faraday Institution explains, the cathode is about one half of the cost of a typical battery cell and in the current generation of Li-ion batteries, the cathode is the capacity limiting factor in the cell rather than the anode. Anodes, however, do have their limitations and safety considerations, not the least being the growth of dendrites, which look like Romanesco cauliflowers growing out from the electrode and threatening to pierce the separator, or cell walls, and short circuit the cell.

Yet lithium-ion batteries, when properly made, monitored, cooled and controlled are remarkably reliable devices; their failure rate is tiny. Their main issue is price.

Despite dramatic cost reductions over the last 18 months, they’re still flipping expensive. In November Bloomberg was estimating a lithium-ion cell pack cost of roughly $139 per kWh. Another analyst, Fastmarkets, reported price falls of Li-ion cells from China from $135.2 per kWh for a typical Li-ion Nickel Cobalt Manganese (NMC) 111 cell battery in January 2022 to $86.6 in October in 2023. But the same report shows that because of higher labour, power and raw material costs, the same cells produced in Germany cost $111 per kWh and nearer to $120 per kWh in the USA.

But if you disregard the differences across countries, why are batteries so expensive?

Louis Piper is Warwick University’s Professor of Battery Innovation and co-leader of the Faraday Institution Degradation and FutureCat Phase II teams. He says while the process of making batteries is automated, it’s quite slow and long winded and there are potential savings to be made.

‘There are three things,’ he says, ‘the production, the packaging and the chemistry.’

He explains there are close similarities with food and battery industrial production. So initially the cathode materials are mixed together like a cake mix.

‘It’s like The Great British Bake Off,’ he says. ‘The materials are mixed together in solvent slurry to ensure a nice even mix and then they are spread onto copper and aluminium foils and baked.’

The foils are produced in machines with rollers which drive the foils through the various processes. It’s a classic continuous production process a bit like that for fuel cell membranes, but the drying steps are expensive and time consuming. Piper says there is research into saving time and money by using extrusion production techniques in widespread use in the plastics industry.

Another way of reducing the price of the cells is to look at the packaging, which is expensive, takes up a lot of room and is often duplicated so the battery ends up being swaddled in ever increasing layers of metal casings.

‘Like the food industry which is dispensing with excess packaging, the battery industry is doing the same,’ says Piper.

So that means cell-to-pack, and even cell-to-(car)-body techniques can be used, where there isn’t a separate battery pack as such, just a lot of cells built into a space in the floor of the car’s body. BMW’s Neue Klasse, slated for arrival in 2025, uses this sort of technique, where the cells look like giant AA batteries and just slot into a space in the car. Similarly BYD’s blade-structured cells actually form part of the vehicle’s structure (though BYD uses LFP cells).

Piper explains that the industry thinks that while nickel-rich NMC-based Li-ion cells will be the predominant cell chemistry for premium cars in future, there are several new developments in the pipeline, which should increase their efficiency, offering the potential of greater range, faster charging speeds and lower costs. This is the chemistry part of the equation, which consists of increasing the nickel content of the NMC cathode material, which is slated for introduction at most car makers and battery suppliers.

‘You can increase the nickel content in NMC,’ says Piper, ‘which means that at a given voltage you can access more of the lithium.’

The other big development is a subtle rebalance of the size of each electrode and the amount of electrolyte. Put simply, it means right-sizing your battery-cell components for maximum efficiency, though the research to guide the process is formidable.

Some of these developments are being used by researchers into solid-state development. Solid-state is touted as the panacea of battery tech, but it’s slow going and even Piper reckons ‘there’s an emerging unity in most manufacturers and scientists that solid-state batteries will be no more than 12 per cent of all production by 2035.’

Could it be that part of that slow going is a reluctance to re-equip most battery factories, which are currently set up to produce the sort of slurry-on-foil continuous process for Li-ion cells, both NMC and LFP based?

The solid-state research effort might be worth the candle, though, as there appears to be a trickle-down effect from it into the research into the improvement of Li-ion and even LFP batteries.

And what of the other chemistries? Certainly LFP is the coming down-tech solution for cheaper and smaller battery cars. VW chief executive Thomas Schäfer said last year that any small car of VW Polo dimensions would have to use LFP chemistry to allow its maker to garner any profit. Rival car makers are beginning to find the same thing.

Given its robust qualities, long life and ability to accept repeated fast charging, could LFP be the preferred chemistry for the vast majority of smaller and cheaper battery cars?

I ask whether that will be the chemistry of choice for used buyers in future.

‘The LFP market was only about six per cent of the European market in 2021,’ says Stephen Gifford, the Faraday Institution’s chief economist, ‘but we’re expecting that to be more like 30 per cent by 2030. Cheaper cars will always be open to alternatives and the market could drive an LFP renaissance’.

Overall the Faraday Institution sees a couple of future scenarios, the first where Li-ion development continues gradually and the technology still dominates the markets as far forward as 2040. That gives a tiny share to sodium-ion and lithium-sulphur cells, but in the second scenario a breakthrough is assumed and the new chemistries occupy 38 per cent of the market by 2040, though NMC and LFP based Li-ion cells still retain a total 46 per cent of the market.

Unlike a 2023 Goldman Sachs report which saw the future chemistries divided by continent (America and Europe going for Li-ion NMC, China and the far east for LFP), the Faraday Institution experts see the market splitting according to the type of vehicle, premium products sticking with Li-ion NMC batteries.

Further developments in cathode manufacturing could help prevent cracking and increase cycle life, but the Faraday Institution ‘recognises both the pros and cons of the increasing use of nickel,’ (or doping), which can affect cell life and overall thermal stability. These super powerful cells, it predicts, will be the new standard in the premium car markets where range and performance are demanded. Further, the Faraday Institution thinks that economies of scale and better lithium extraction techniques should ensure a more ethical stance to battery making in future.

In the end, as Piper says, ‘when it comes to batteries and the future, everything is directed by a dollar sign.’

So if you were thinking about an EV, there’s not much stopping you right now apart from price, though that’s arguable. The current generation of Li-ion cells are generally reliable, safe and have a usable life well in excess of a decade, probably nearer 15 years. And the UK government’s spread of incentives to fleet and company buyers (but not private individuals) might trickle down into the market. The Porsche Taycan is one of the best battery cars out there with a new price starting at £86,500, yet at the time of writing there are 718 examples on the AutoTrader website, many at or around half the new price with quite modest mileages of around 40,000 to 60,000 miles.

The lack of demand for used EVs could be an ill wind for new private buyers. Mind you, if you are thinking of switching to a second-hand battery car, now might be just the right time to buy.