Electrification is the future trend of automobile development. Currently, the proportion of new energy vehicles is soaring, and technologies such as components are gradually maturing. The only remaining major obstacle to the overall cost of vehicles is the power battery. How long it will take for new energy vehicles, especially pure electric vehicles, to become widespread depends on when power batteries can be commercialized on a large scale. At present, the goals for power batteries are clear: to improve range, increase safety, and reduce costs to achieve affordability.
Considering factors such as technology, cost, and commercialization, solid-state batteries have gained significant momentum and become a major research direction for next-generation batteries. As is well known, compared to traditional lithium-ion batteries, solid-state batteries differ in that their electrolyte is solidified, offering advantages such as high energy density and superior safety.
Traditional liquid lithium batteries are known to scientists as "rocking chair batteries." The two ends of the rocking chair represent the positive and negative electrodes, with a liquid electrolyte in the middle. Lithium ions move back and forth between the two ends of the rocking chair, completing the charging and discharging process by moving from the positive electrode to the negative electrode and back to the positive electrode. Solid-state batteries operate on the same principle, but the electrolyte is solid.
What are the advantages and disadvantages of solid-state batteries?
Solid electrolytes offer high safety compared to liquid electrolytes, which are prone to ignition and explosion after being punctured or crushed. Solid electrolytes are non-flammable, non-corrosive, non-volatile, and do not leak.
Solid-state batteries have high energy density, allowing the electrolyte to hold more high-voltage cathode materials. In addition, their small size and stability simplify battery management, naturally leading to a significant increase in energy density.
Lightweight: In traditional lithium-ion batteries, the separator and electrolyte together account for nearly 40% of the battery's volume and 25% of its mass, while using a solid electrolyte can naturally reduce both volume and mass.
It has strong cycle performance. Because solid electrolytes solve the problems of solid electrolyte interface film and lithium dendrite formation during the charging and discharging process of liquid electrolytes, the cycle performance and service life of lithium batteries are greatly improved.
Of course, solid-state batteries are not perfect; they also have drawbacks such as high interface impedance, difficulty in fast charging, and high cost.
If the interfacial impedance is too high, the interface between the solid electrolyte and the electrode material is in a solid-solid state. Therefore, the effective contact between the electrode and the electrolyte is weak, and the ion transport kinetics in the solid material are low.
Fast charging is quite difficult. Issues such as battery impedance and conductivity manifest as high internal resistance, which hinders charging and causes energy loss during the charging process. This energy waste is a problem that cannot be ignored.
High cost is inevitable because the current solid-state battery manufacturing technology and processes are not mature enough.
What are the future challenges of solid-state batteries?
From the perspective of when the theory was first proposed, solid-state batteries are not a new concept, and their research and development has not progressed as rapidly as expected over the years. Although solid-state batteries have shown significant advantages in many aspects, there are also some problems that need to be solved.
Because the electrolyte material in solid-state batteries is entirely solid, and the conduction process involves point contact, the manufacturing process itself requires addressing the issue of interfacial impedance. Secondly, the current state of solid-state battery cycling equipment is not yet optimal.
Solid-state batteries use solid active materials for the positive electrode, negative electrode, and electrolyte. The contact between them is point contact, not surface contact. As a result, the ionic conductivity of solid electrolytes is not as high as that of liquid electrolytes. Secondly, based on the difference between point contact and surface contact, the problem of interfacial impedance needs to be solved in the battery manufacturing process.
Solid-state batteries are not simply solid during charging and discharging. Like all batteries, they expand and contract during charging and discharging. While liquid batteries have a certain tolerance for this, slight expansion during the charging and discharging process is easily absorbed. However, solid-state batteries may crack during expansion and contraction, affecting their usability. Therefore, the quality of solid-state battery cycling equipment is still insufficient, which is a problem.
When will commercial mass production begin?
Currently, the manufacturing technology for solid-state batteries still needs further development, and many difficulties remain to be overcome for commercial production expansion. However, it is expected that with continuous advancements in research and industrial technology, the scientific and technological challenges in all-solid-state batteries will gradually be alleviated.
Globally, solid-state batteries are expected to achieve small-scale mass production around 2020. BMW claims it expects to achieve a breakthrough in solid-state batteries by 2026 and subsequently mass-produce them; Toyota is also fully committed to developing solid-state batteries and has already developed a battery prototype. Toyota has stated that this battery will be commercially available around 2020 and substantially improved by 2025.
