Solving "range anxiety" with all-solid-state batteries still requires time.

"Range anxiety" is one of the core pain points facing the development of electric vehicles, and all-solid-state batteries are seen by the industry as a "seed player" to solve this problem.

According to reports, China's first large-capacity all-solid-state battery production line was recently completed and is currently undergoing small-batch testing, with plans to gradually move to mass production between 2027 and 2030.

What are the differences between all-solid-state batteries and lithium-ion batteries? Can they truly solve the "range anxiety" of electric vehicles? What challenges still need to be overcome to achieve large-scale promotion and application in the future? To address these hot topics, a reporter from Science and Technology Daily interviewed experts in the battery field.

First question: What are the differences between all-solid-state batteries and lithium-ion batteries?

"Compared to traditional lithium-ion batteries, the difference in all-solid-state batteries lies in the replacement of the electrolyte and the optimization of the entire positive and negative electrode materials," said Chu Shulei, Dean of the Carbon Neutrality and Technology Innovation Research Institute at Wenzhou University.

Xiang Yuxuan, Assistant Professor at the School of Engineering, Westlake University, told reporters that all-solid-state batteries use non-flammable solid electrolytes to replace traditional liquid organic electrolytes. Currently, there are three main technical routes: sulfide electrolytes, oxide electrolytes, and polymer electrolytes.

Xiang Yuxuan explained that the main structure of a traditional lithium-ion battery includes a graphite anode, a lithium iron phosphate cathode (or ternary cathode), and a porous polymer membrane and liquid organic electrolyte between the cathode and anode. During charging and discharging, lithium ions migrate back and forth between the cathode and anode using the liquid organic electrolyte.

"In contrast, all-solid-state batteries use a solid electrolyte membrane instead of a porous polymer membrane and organic electrolyte. During charging and discharging, lithium ions between the cathode and anode can be transported through special ion channels in the solid electrolyte," Xiang Yuxuan said. He added that all-solid-state batteries not only avoid the leakage, corrosion, and combustion problems associated with liquid organic electrolytes, but also allow for the use of higher-capacity cathode and anode materials, thus theoretically potentially significantly improving battery safety and energy density.

Second question: How to improve the driving range of electric vehicles?

“Range anxiety is a major pain point in the new energy vehicle industry. The root cause is the relatively low energy density of current lithium-ion batteries, making it difficult to provide sufficient electrical energy within the constraints of battery pack size and weight,” said Xiang Yuxuan.

Xiang explained that the energy density of lithium-ion batteries is primarily limited by the low specific capacity of the positive and negative electrode materials. All-solid-state batteries, due to the stability and safety of solid-state electrolytes, can use positive and negative electrode materials with higher theoretical specific capacities, directly leading to a significant increase in battery energy density.

Furthermore, the safety advantages of all-solid-state batteries allow for the reduction of some of the safety features of traditional batteries during system integration, resulting in a more compact overall structure.

“If all-solid-state batteries are applied to electric vehicles, more electrical energy can be stored with the same battery pack size and weight, greatly increasing the driving range of electric vehicles. Theoretically, this could allow electric vehicles to travel over 1000 kilometers,” Xiang Yuxuan believes. While the large-scale mass production of all-solid-state batteries currently faces technological and cost challenges, in the long run, all-solid-state batteries are expected to become one of the key breakthroughs in solving the “range anxiety” problem of electric vehicles.

Third question: How far are we from large-scale promotion and application?

"Currently, the research and development of all-solid-state batteries is still in its early stages, and its core material is a solid electrolyte, a unique property that makes it significantly different from the existing manufacturing processes of lithium-ion batteries," Xiang Yuxuan told reporters. He added that several key technical challenges need to be overcome to achieve large-scale application of all-solid-state batteries.

Chu Shulei also believes that all-solid-state batteries face several challenges in achieving both high energy density and long cycle life, and realizing large-scale application.

Xiang Yuxuan analyzed that the core materials used in all-solid-state batteries, such as the high-performance solid electrolyte, have high raw material and process costs. For example, the preparation and use of key materials are sensitive to air, requiring special equipment and strict environmental control. This requires further breakthroughs in large-scale and low-cost synthesis and preparation technologies; therefore, the all-solid-state battery industry chain will still take time to mature.

At the same time, the positive and negative electrode active materials and the solid electrolyte in all-solid-state batteries form a solid-solid interface, and the volume change of the active materials during charging and discharging will pose a significant challenge to the stability of this "rigid" interface contact. Chu Shulei gave an example: when all-solid-state batteries use silicon-carbon anodes, significant volume expansion occurs, generating interfacial impedance. Under experimental conditions, very high pressure is required for the battery to function properly.

"This requires researchers to conduct in-depth mechanistic studies on the electrochemical and mechanical properties of solid-state electrolytes, in order to overcome the solid-solid interface stability problem as soon as possible," said Xiang Yuxuan. He added that overcoming these key technical challenges requires collaborative innovation breakthroughs in multiple fields, including materials and equipment, ultimately driving the large-scale production and application of all-solid-state batteries.