With a stream of major cell suppliers regularly announcing ‘major’ breakthroughs in solid-state cell technology, it is proving difficult to discern the reality of the state of play at present.
The harsh reality is that 90% of news, plans and solid-state plant activity appears to be bogus, as start of production (SOP) dates slip or vanish, with this being particularly true of information coming from China. One major player in the solid-state landscape announced very recently that it was re-focusing its efforts on cost reduction and given that its primary focus is solid-state, one does question the likelihood of a strong business case underpinning the product.
Theoretically, solid-state cells offer a true benefit to the light vehicle automotive market because, in their most basic form, such cells are volumetrically more energy-dense than current mass market solutions as there is much less ‘wasted’ space between the current collectors. However, in reality, achieving a mass production-capable product remains a long way off. Indeed, multiple companies are claiming that they have achieved the manufacture of solid-state batteries (SSBs) already, but they are produced very expensively and only in small batches, and yes, they do offer an energy density benefit, but there is still no real business case until manufacturing methods become significantly cheaper.
The most promising research in solid-state technology from a mass-manufacture viability standpoint seems to suggest a ceramic-based electrolyte which is layered with the electrodes. But therein lies the mass manufacture issue - the core material is ceramic/glass meaning that the structure is incredibly fragile. On top of this, the interface between the current collectors needs to be so perfect that factories would need to be hermetically sealed, and the equipment used would need to be at a nanometer level of precision, somewhat like the semiconductor industry.
Solid-state cell technology has been on many companies' agendas for a long time, but postponed release dates - a well-known Japanese OEM being the worst in this regard - and other companies dialling back investments indicate a low likelihood of true solid-state coming to fruition this decade in the light vehicle sector. Semi-solid-state cells offer slightly greater manufacturing tolerance with some such cells using an inert liquid to act as a ‘transfer’ device to aid molecular transfer. In fact, a China-based major car manufacturer does offer a 150kWh semi-solid-state battery pack for use on the roads today. But at a cost of more than EUR35,000, it isn’t currently an option to be factory-fitted and sold along with the car, rather customers can rent this battery at a daily or weekly charge.
Polymer-based solid electrolyte technology offers a more manufacturable solution, and this type of cell has been produced on a relativity large scale to date. We are also aware of a large-scale Chinese cell manufacturer bringing a new version of this technology to market. However, there are drawbacks of polymer-based solid electrolyte cells including indifferent power capability and poor cold ambient temperature performance. There is the potential for these cells to be used in warm ambient markets, but without heating mechanisms or other tradeoffs, we remain hesitant over this technology entering the market in a significant way until we see technological enablers for more widespread use.
Sodium-ion is continuing to gain momentum with information being received that smaller plant lines are in production and larger cell lines are planned. One major cell manufacturer recently stated that a major cell production line is being constructed but information received at a recent event in Frankfurt implies that there is still hesitation around the technology and, similar to solid-state, what is being disseminated in company releases and reports may be exaggerating the current state of play of this technology.
What might be the situation in 20 years’ time? In the best-case scenario, all mass manufacturing tolerancing and fatigue issues would be resolved, and solid-state batteries would become the dominant technology given the clear volumetric and gravitational advantages they offer over the incumbent Li-ion technology. We may see a situation where solid-state is the default technology for midsize and larger vehicles where high-performance and/or long-range is required while sodium-ion can offer truly affordable BEVs in the low-cost small vehicles segments where currently battery vehicles struggle to compete with ICE from a cost perspective.
Oliver Petschenyk, Powertrain Analyst, GlobalData
This article was first published on GlobalData’s dedicated research platform, the Automotive Intelligence Center.
