Weekend reading: Boost and Assurance for solid-state batteries

The Boost and Assurance of solid-state batteries (SSBs) continues to grow as industries from automotive make big bets on the storage technology.  A roll call of major battery makers and start-ups scrambling to get from lab to fab.  The authenticity of SSBs is in question.  As Marija Maish reports, now is the window of opportunity for decades-old technology to take the next big step toward commercialization.

Toyota’s Concept-i 02. The Japanese automaker has produced prototype electric powered motors powered with the aid of using stable-country batteries, however says its first manufacturing car to characteristic the era could be a hybrid, because it expects SSBs to initially be too expensive for a full electric vehicle.  .  A larger battery is required.

This is a moment of truth for dozens of companies working on SSBs as their technology emerges from cloistered labs and makes its way to the factory floor.  Having mobilised a large investment, SSB manufacturers now need to prove that they have not only solved the challenges associated with the use of solid electrolytes, but have commercial-scale success.  If proven, SSBs will be in a position to deliver on the twin promises of improved performance and safety compared to their ubiquitous, liquid-filled cousins.  “When it involves the industrial viability of SSBs, we should distinguish among era instructions – SSBs primarily based totally on polymer electrolytes are already at the market, at the same time as the ones based on oxide and sulphide electrolytes are mostly at the prototype stage,” says Thomas Schmaltz of the German Fraunhofer Institute for Systems and Innovation Research (ISI).

Schmaltz and his colleagues developed a roadmap where the three most promising solid electrolyte variants were tested and compared with expected developments in liquid electrolyte lithium-ion batteries (LIBs).  Their results showed that SSBs must exhibit significant performance improvements relative to state-of-the-art LIBs to gain any relevant market share.  What’s extra, they want to do it fast.

“There is always a certain opportunity and reluctance to switch to new technologies. All KPIs for LIBs are constantly improving, and SSBs’ KPIs [Key Performance Indicators] to increase power density and sufficient safety may soon be difficult to justify the higher costs,” Schmaltz says.  He estimates that SSBs will have to prove their viability in the next five years.

According to expected market developments, SSB production – currently less than 2 GWh globally and based on polymer SSB – is expected to increase significantly between 2025 and 2030, when oxide and sulphide electrolyte-based SSBs begin to roll off production lines on a large scale.  According to the Fraunhofer ISI guideline, production capacity is estimated to be between 15 and 55 GWh in 2030 and 40 and 120 GWh in 2035 – still less than 2% of the expected LIB market.

A flurry of activity

The findings mirror announcements from CATL, the world’s largest electric vehicle (EV) battery manufacturer.  Earlier this year, it said SSBs for retail electric cars would not be mass-produced before 2030, after first emerging from its labs by 2025.  Following in its footsteps, battery makers Samsung SDI, SKI and LG are gearing up.  SSBs for market introduction after 2027, 2029 and 2030 respectively.  Meanwhile, a joint venture between Panasonic and Japanese car giant Toyota has already presented a prototype car equipped with SSB.

Toyota, despite failing to capitalise on its early success in hybrid EVs, is now a major carmaker with more than 1,000 SSB patents.  It’s pumping more than $35 billion into EVs by the end of the decade, half of which will go into battery R&D.  However, earlier this year, the automaker clarified that the first Toyota hybrid with SSBs will serve as a testbed.  “Solid-state batteries are still not cheap, and full-size in a BEV could increase the cost of the car,” says Gil Pratt, Toyota’s chief scientist.

Meanwhile, Japanese rivals Nissan and Honda have revealed plans to set up SSB production lines in-house.  Western automakers including Volkswagen, Mercedes-Benz, Stellantis, BMW and Ford are also exploring SSBs through partnerships with start-ups.

Technical challenges

Today, there are three competing ways to make solid-state electrolytes, and each has its own technical hurdles.  “In the EV space, sulphide-based solid electrolytes are particularly promising, with some major developers including CATL, BYD, Samsung SDI and Toyota,” says Max Reid, research analyst at Wood Mackenzie. “It incorporates ample substances and has a fantastically excessive lithium-ion conductivity as compared with different stable electrolytes, which shows right overall performance for excessive cycles. However, the material is unstable in air and releases toxic and flammable H2S gas.

The second method, the oxide-based electrolyte, is the most chemically stable version.  But its manufacturing process, particularly high-temperature sintering procedures, makes mass production an easy affair.

“Their separator layer is susceptible and cannot be rolled, so that you should stack the mobileular like a deck of cards. There’s no established process today, so it remains to be seen whether it can be done in a cost-effective way,” says John Jacobs, chief marketing officer of Solid Power, a Colorado-based startup specialising in sulphide SSBs. From BMW and Ford  Support, Solid Power claims to use the same processes and equipment currently used in state-of-the-art LIB manufacturing.

Finally, there are polymer-based solid electrolytes, which are much easier to manufacture compared to the other two categories.  “An extraction process for polymers without using any solvent has already been established and used commercially,” says Fraunhofer ISI’s Schmaltz.  “If scaled-up, that is a inexpensive manufacturing approach than the ones mounted for LIBs.”

However, SSBs with polymer-based electrodes have a typical ionic conductivity of only 10-7S/cm at room temperature, which is below the level of current liquid electrolytes.  They have very poor oxidation stability with high-voltage cathodes (only compatible with LFePO4/LFP), all of which greatly impair the energy density of polymer-based batteries.

Cost is king

What we hear today from many developers involved in the SSB space is that they have solutions to these challenges, and now many are facing the next big problem: high cost.  “The value of stable-country batteries is better than modern LIBs. The higher energy density saves module and pack costs, replacing graphite anodes with thin sheets of lithium metal, and replacing liquid electrolytes with solids containing elements like germanium and lanthanum increases costs,” says Woodmac’s Reid.  Looking at the SSB supply chain, there are not many benefits.  An obvious obstacle is the lithium metal anode material.  This could see cell producers opt for a more abundant anode material – silicon – which offers higher performance but not as much as lithium metal.  Otherwise, SSBs use essentially the same amount of cathode material as current LIBs, depending on the cell voltage.  This means that SSBs face the same challenges found in the battery space today.

The cost depends not only on raw materials, but also investment in production processes and equipment.  To some extent, it is possible to use equipment in existing Li-ion factories to produce SSBs.  Namely, the cathode structure may be similar to current LIBs and the same device may be used in SSB fabrication, the anode being completely different.

 “Lithium metallic sheets are both delaminated withinside the mobileular shape or a proprietary approach is used to construct the silicon anode, [using] fantastically new techniques,” Reid says. “With post-electrolytes, injectable fluids are changed with a beneficial aid the usage of robust electrolyte manufacturing techniques. This is a monumental change to the current factory process, and with each gigafactory costing $3 billion or more, it will be more expensive to retrofit these facilities to produce SSBs alone.

A popular topic

In particular, the production cost of oxide-based and sulphide-based electrolytes is high, so they are less likely to be applied in more cost-sensitive sectors than automotive sectors, such as the stationary storage industry.  Here, small space/mass performance requirements are low, so polymer electrolytes are the most popular choice in stationary storage applications today.  Polymer-based SSBs have already been deployed in the field, for example in mini grid projects conducted by France’s Blue Solutions, the first SSB manufacturer to achieve mass production in the hundreds of MWh.

The capacity of the opposite  electrolyte instructions in desk bound garage has but to be completely proven. Yet the movement is on.  Earlier this year, German and US-owned energy storage heavyweight Fluence entered into a multi-year deal with US battery start-up Quantumscape to introduce oxide-based SSB technology into stationary storage applications.

“We are working together to validate and test QuantumScape’s SSB cells for use in Fluence’s proprietary stationary storage products.  “Our team is particularly excited about the potential of oxide SSBs to enable lithium metal anodes with corresponding cost and density improvements,” says Brett Galura, SVP, Fluence Next and CTO. “These capabilities assist cut back set up footprints with the aid of using a 3rd and protection capabilities that require fewer system-stage components.  delivers, simplifying total system security approaches.”

Proof of performance

Indeed, higher power and greater safety are often cited as the main advantages of SSB technology, with higher energy density and faster recharge times compared to LIBs being regularly claimed.  However, proven results are hard to come by.  “Enthusiasts in the market game claim that their SSBs have the right standard of overall performance but it is very difficult to pick the actual numbers when they provide these. Only third-party tested values ​​allow for an independent assessment of actual cell performances,” says Schmaltz.

Taiwanese SSB start-up ProLogium, which signed a technology cooperation agreement with Mercedes-Benz earlier this year, says its prototype is already in testing: “To date, ProLogium has shipped 7,300 EV cells with a capacity of 50 – 60 Ah worldwide. One million to vehicle partners and customers for consumer applications for verification.  Cells are distributed,” says Lisa Hsu, Prologium’s vice director of marketing.

Cell makers have acknowledged that they face challenges in ramping up production capacity globally at a pace that meets consumer demand. “[Prologium] is the simplest stable-country lithium ceramic battery producer able to generating at scale and supplying a solid deliver to the worldwide EV industry,” he says. The plan is to start the company’s first 3 GWh production plant in early 2023.

Earlier this year, a ceramic separator and 2.5 kWh capacity battery were unveiled with Taiwanese scooter maker Gogoro, which has an extensive network of battery swap infrastructure.  When it comes to technology perks, the Prologium has a long list, with roughly 80% higher pack energy density, more than 60% faster charging and lower cost, as well as 90% solid-state electrolyte recycling.

Other experts in the field are also keen to highlight the advantages of SSBs over LIBs, especially for the automotive sector.  “There’s a lot of smoke and mirrors out there but cost is always important,” says Solid Power’s Jacobs.  “The first advantage is excessive strength density, which makes it feasible to percent 30 to 40% extra strength into an SSB mobileular than latest excellent liquid-primarily based totally LIB cells, and gives automakers the option to increase the range or reduce the number of batteries needed inside and thus save money in the company’s B A prototype EV.  The cell is targeted at 390 Wh/kg and 930 Wh/L.

An added benefit is that carmakers can enjoy greater savings by eliminating the battery pack cooling system. “When latest liquid LIBs get hot, even if the auto is simply parked withinside the sun, the cells degrade.  “SSBs like to be hot,” says Jacobs.  But in the case of arguably the most promising startup working on sulphide electrolytes, Solid Energy still has a long way to go to start production, currently making just 150 kg of electrolyte per month;  But growing.

“Our upcoming second facility can be expanded to 10 tons per month, which is enough to make thousands of EV cells per year, which automakers need to pass validation testing, but not enough cells to meet the car program.  ,” says Jacobs.  “To provide you with a few idea, 10 GWh can deliver among 100,000 and 200,000 motors, so proper now our cells and strength era ability is masses of MWh.”

SSBs are pick and mix

Cathode: Similar supply chains and processing routes are already established for advanced LIBs, including transition metal-based oxides (NMC, NCA) and lithium iron phosphate (LFP).

Anode: Although graphite has been shown to work in several solid electrolyte cell concepts, lithium metal and silicon are the go-to anode active materials.  Lithium metal is considered the most promising because it enables high energy density on the anode side.

Solid electrolyte type: oxide, sulphide, and polymer are the three main categories today, although mixed methods are also possible.