Chinese scientists say they have developed a new solid-state battery technology to match cutting-edge performance at just 4 per cent of the cost.
Most EV batteries are of the lithium-iron phosphate or ternary lithium variety, and each has its own merits in terms of cost stability and energy density. However, both contain liquid electrolytes.
Liquids have a lower energy storage density than solids. Despite advancements in liquid battery technology, their bulkiness, weight and potential fire risk prevent their usage in lightweight EVs.
But researchers at the University of Science and Technology of China (USTC) in Anhui province have been able to develop all-solid-state batteries – using solid electrolytes for conduction – that also come at a fraction of the cost, holding out great promise for commercial applications of the technology.
Solid-state batteries have numerous advantages over the conventional kind, such as double the energy density, faster charging speeds, and unrestricted charging temperatures.
As they are non-flammable, non-corrosive and leakproof, these next-generation batteries also represent a much safer option for the electric vehicle and energy storage industries.
However, large-scale application has been held back by high production costs.
Solid electrolytes require expensive metals like lanthanum and cobalt, and the manufacturing process calls for a high degree of precision and dedicated production lines.
To address this challenge, a USTC team led by Professor Ma Cheng developed a new solid electrolyte, called lithium zirconium oxychloride. Its performance was found to be comparable to that of advanced sulphide and chloride solid electrolytes but at only 4 per cent of the cost, according to findings published in peer-reviewed journal Nature Communications last month.
A commercially viable solid-state lithium battery electrolyte must show high ionic conductivity, good “deformability” or capacity for shock absorption, and cost under US$50 per kg.
None of the existing electrolytes can meet all these criteria. Ceramic electrolytes generally lack deformability, while sulphides and chlorides are expensive, all costing over US$200 per kg.
However, the lithium zirconium oxychloride electrolyte developed by Ma and his team achieved room-temperature ionic conductivity that was more than double the standard required for real-life application. Meanwhile, its excellent deformability allowed the material to maintain its shape under high pressure, meeting application requirements.
“The team provided two synthesis routes, one with a raw material cost of only US$11.6 per kg and the other less than US$7 per kg. In application tests, a battery using lithium zirconium oxychloride took only 12 minutes to charge and maintained stable cycles over 2,000 times at room temperature,” USTC said in a statement.
Both the academic community and industrial producers have speeded up their pursuit of this next generation technology. However, China’s EV companies have so far opted for semi-solid batteries, given the high material and manufacturing costs of the all-solid variety.
Japanese car giant Toyota, which uses sulphides as solid electrolytes, is also planning to commercialise solid-state battery technology, The Financial Times reported on July 4.
Keiji Kaita, president of Toyota’s Carbon Neutral Advanced Engineering Development Centre, said their goal was to halve the size, weight and cost of both liquid and solid batteries, according to the report.
He said Toyota had developed methods to improve battery durability and believed it could manufacture solid-state batteries with a range of 1,200km (745 miles) and a charging time of 10 minutes or less.
Toyota’s push will undoubtedly intensify competition in the EV battery field with China, whose lithium-ion battery exports last year accounted for nearly 70 per cent of global shipments.
However, Toyota’s products are not expected to hit the market until at least 2025, with mass production likely only after 2027.
“With the world’s largest new energy vehicle market and a leading position in relevant scientific publications, China is poised to make significant strides in the industrialisation of solid-state batteries,” Dong Yang, vice-chairman of the China Electric Vehicle Association think tank told Shanghai-based website Guancha in January.