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The silicon anode industry could be hampered by the supply of silane gas, given the limited scale of non-Chinese production and competition with the growing solar sector, which also uses the gas, Vincent Pluvinage, chief executive officer and co-founder of OneD Battery Sciences, told Fastmarkets.
Silicon increases the energy density of lithium-ion anodes and has been used in small quantities in electric vehicles for several years.
And according to Pluvinage, silane gas is the most cost-effective way to purify metallurgical silicon to the levels required for use in both silicon-based photovoltaic cells for the solar sector and in battery anodes for EVs.
Nameplate mono-silane gas production capacity in North America totals less than 30,000 tonnes per year (tpy), but the majority of this is earmarked for the solar sector, Pluvinage said in an interview with Fastmarkets in February.
And while there is a greater production capacity for trichlorosilane (TCS) – a precursor to silane gas – outside of China, this is generally not converted to the mono-silane gas that OneD uses in its silicon anode material, Pluvinage added, noting that the conversion process was not found by the company’s research to be cost-effective.
China’s combined production capacity of mono-silane gas and TCS, at roughly 1 million tpy, dwarfs the total production capacity for both substances outside China, Pluvinage said.
Furthermore, according to Pluvinage, the gas’s continued widespread use in the mature solar sector shows that the substance is the sole practical way to reach the high purities of silicon required for solar and anode materials.
“People have tried to create pure silicon for solar cells for decades using other methods,” he said, but these were not successful and “all have been abandoned.”
Although silicon can increase the energy density of lithium-ion anodes, its use has historically been limited by its tendency to degrade during the charging and discharging cycle.
But in their pursuit of longer-range, higher-capacity and more cost-competitive battery cells, innovators are working to increase the use of silicon in anodes, with OneD among a handful to be making progress in this space outside China.
Along with silane gas, developers are also working on solutions based on silicon oxide, silicon-carbon composites and high-purity silicon metal.
Experts see the drive toward the development of more cost-competitive battery cells as holding the key for further adoption of EVs.
“In saturated markets, particularly Europe, the lack of affordability has limited EV adoption,” Fastmarkets battery raw materials analyst Phoebe O’Hara said.
“To maintain momentum in the EV transition, EV prices must come down,” Fastmarkets’ battery manufacturing cost modeler Muthu Krishna agreed, adding: “To do this, expensive, oversized battery electric vehicles [BEVs] with oversized battery packs must give way to affordable BEVs with smaller battery packs whilst the charging infrastructure is drastically improved.”
Silicon stores 10 times the energy of graphite – the currently prevalent anode material – spurring a race among battery materials developers worldwide to innovate its use in anodes, either as a replacement for or complement to graphite.
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OneD Battery Sciences is set to open a pilot plant in Moses Lake, Washington, before scaling production to commercial volumes later, capitalizing on its dedicated supply of silane gas.
Pluvinage emphasized the cost benefits of OneD’s anode material, named SINANODE, which adds silicon nanowires to natural graphite anodes.
SINANODE increases the costs to produce the silicon portion of a battery cell by $3.50 per kilowatt hour, Pluvinage said; in contrast, synthetic graphite adds $7 per kilowatt hour to the cost, making the addition of SINANODE cost-competitive.
The company can introduce silicon to an otherwise majority graphite-based anode material, resulting in a cell that contains around 10-30% silicon by weight, he explained.
“So we are producing a composite active material for the anode which contains silicon and graphite, which in the bill of material of each cell costs less than pure graphite,” Pluvinage said. “We target that the battery pack cost reduction should be about 20% compared to a [common lithium-ion] battery pack based on a pure graphite anode.”
OneD plans to introduce its own silane gas production for commercial anode material production via an exclusive partnership with process engineering design and modular construction firm Koch Modular.
Under this agreement, the company will scale up silane gas production by building a modular silane gas plant adjacent to a planned SINANODE processing plant.
“Koch Modular is designing for OneD modular plants, and the first location in North America will produce 4,800 tpy of mono-silane gas for exclusive use in making SINANODE,” Pluvinage said.
He expects the silane gas costs from the process to be about 50% lower than other sources of mono-silane gas.
Increased demand for silicon as an anode material comes as demand for solar photovoltaic production inside and outside China is also on the rise.
In its Renewables 2023 report, the International Energy Agency (IEA) observed that rising photovoltaic demand and limited polysilicon capacity has placed supply of the raw material under pressure.
Competition between the solar and anode sectors for high-purity silicon is already evident.
A major North American silicon producer, REC Silicon, reported in its fourth-quarter 2023 presentation that its newly reopened Moses Lake facility, with its nameplate 24,000-tpy silane gas capacity, would ramp up polysilicon production for the solar sector.
But the vast majority of the facility’s output is already earmarked for the solar sector, under an offtake agreement with energy solutions provider Hanwha, announced in November 2023.
OneD has made access to a strong supply chain of raw materials central to its silicon-boosted anode offering.
“There is nothing more important than the supply chain,” Pluvinage said.
He believes OneD’s access to scalable silane gas production and its production process’s adaptability to already qualified battery-grade graphite will allow consumers to use their existing graphite supply without needing to requalify for SINANODE.
With its dedicated supply of silane gas, adjacent to the SINANODE plant, the company hopes to be able to avoid the supply difficulties Pluvinage expects other silane gas consumers outside of China will face.
The modularity of the plant should allow OneD to scale production to meet increasing demand and eventually produce anode material in Europe as well, Pluvinage said.
The company plans to source low-carbon metallurgical-grade silicon at competitive prices from North America. With a number of major producers in North America and Europe the supply of metallurgical-grade silicon is more geographically balanced than other battery raw materials, like graphite, whose production is overwhelmingly concentrated in China.
This is a particular advantage for silicon consumers during this period of geopolitical tension between China and the West.
China introduced export controls on graphite-related products in October, and graphite production in the rest of the world remains relatively limited.
This has created incentives to foster new raw material production, including the Inflation Reduction Act in the US, which has already been credited with helping to spur developments on multiple fronts in the graphite anode sector.
For manufacturers to benefit from the incentives, however, they are required to source raw materials from countries considered to be friendly to the US.
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