When it comes to the next big thing in battery technology, the term “solid-state” almost always comes up. It’s considered the ultimate form of battery technology after liquid lithium-ion batteries, yet year after year, we hear that it’s “coming soon”—and yet, year after year, it remains confined to the lab.

I. What Exactly Has Changed with Solid-State?

Current lithium-ion batteries use liquid electrolytes, which conduct electricity but are prone to leakage and sensitive to high temperatures. Solid-state batteries replace these with solid electrolytes, allowing for the use of lithium-metal anodes. This has the potential to boost energy density from the current level of just over 200 Wh/kg to 400 or even 500 Wh/kg. Non-flammable and capable of operating across a wide temperature range—it all sounds like nothing but advantages.

II. Different Factions, Each With Their Own Agenda

The polymer-based process most closely resembles existing production lines, but its room-temperature conductivity is relatively low; oxides (such as LLZO with a garnet structure) are stable but hard and brittle, making it difficult to bond interfaces; Sulfide materials exhibit the highest ionic conductivity and are the focus of significant investment by Toyota and Samsung, but they are sensitive to water and oxygen and are extremely demanding in terms of manufacturing environments.

Route Ionic Conductivity Interface Contact Challenges in Mass Production
Polymers On the low side Okay Lower
Oxide Chinese Difficult Chinese
Sulfides High Chinese High (sensitive to water and oxygen)

III. How Far Are We from Mass Production?

Semi-solid-state batteries have already made their way into vehicles; for example, NIO’s early 150-kilowatt-hour semi-solid-state battery pack can be considered a “preview” of solid-state technology. As for all-solid-state batteries, Toyota has set a demonstration timeline for 2027–2028, while China’s CATL and Weilan are also pushing forward with their development. However, for all-solid-state batteries to see truly large-scale adoption, three major hurdles—solid-solid interface impedance, lithium dendrites, and cost—must first be overcome. The general consensus is that this will take another five to ten years.

Don’t Overhype Solid-State Storage: Start with Semi-Solid-State to Improve the User Experience; All-Solid-State Is the “Ultimate Solution,” but It Will Take Patience.

So solid-state batteries aren’t “just around the corner”—they’re already at the doorstep, but the door is still a little heavy.