How Do Semi-Solid State Batteries Work?

02/03/2025

Like all batteries, semi-solid state batteries generate electricity through chemical reactions between positive and negative electrode materials. The electrolytes in semi-solid state batteries have a consistency closer to gel than in traditional batteries. In traditional lithium batteries, the positive and negative electrodes act as “energy reservoirs,” while the electrolyte serves as a “channel” that allows lithium ions to move freely between the electrodes. This structure is why they are referred to as liquid batteries. The development of semi-solid state batteries is based on innovations in electrode materials. These batteries contain a “clay-like” substance formed by mixing fine lithium compound particles with liquid electrolyte, serving as the electrode material. This hybrid design achieves a balance between the high safety of solid-state batteries and the fast ion transmission rates of liquid batteries. The advantages of semi-solid state batteries also apply to qapasity’s Arctic Series, which features high safety and a C-rate of 1 due to its fast ion transmission.

What distinguishes semi-solid state (LFP) from “traditional” LFP?

	Semi-Solid-State LFP	Traditional LFP
Safety	⭐⭐⭐⭐⭐	⭐⭐⭐⭐
Energy density	⭐⭐⭐⭐⭐	⭐⭐⭐
Performance in low temperatures	⭐⭐⭐⭐	⭐⭐⭐
Performance in high temperatures	⭐⭐⭐⭐	⭐⭐⭐

The Difference Between Solid State and Semi-Solid State

What’s the difference between semi-solid state and “full” solid state batteries? Solid state batteries use a solid electrolyte instead of the liquid electrolyte found in traditional lithium-ion batteries, eliminating any liquid components. This makes them potentially safer, as they remove the risk of leaks and fires associated with liquid electrolytes.

Semi-solid state batteries, on the other hand, still contain some liquid electrolyte, making them less safe than full solid state batteries but safer than conventional batteries. Solid state batteries also offer higher energy density, allowing them to store more energy per unit volume than semi-solid state batteries. Their solid electrolytes enable faster charging rates and longer lifespan. However, solid state batteries are still under development and are not yet commercially available. The industry expects these batteries to become available within 5 to 10 years.

	Semi-solid state	“Full” solid state
Technology maturity	Industrial manufacturing by a few high-tech producers	Not yet commercialized
Electrolyte	Porous and moist. Uses a combination of partially solid and liquid electrolytes, typically with a ceramic or polymer solid and a traditional liquid electrolyte. This design enhances ion conductivity and interface stability.	Dry ceramic electrolyte. Uses only solid electrolytes, which can be ceramic, polymer, or other solid materials, providing high stability and safety.
Safety	Higher safety than traditional LFP due to reduced risk of liquid electrolyte leakage.	Highest safety, completely eliminating the risk of leaks and fires associated with liquid electrolytes.
Temperature Sensitivity	Performs well in both cold and hot climates.	Very high performance, including charging capability at temperatures as low as -40°C.
Energy Density	Higher than traditional batteries due to improved stability and charging/discharging efficiency.	Even higher, with potential energy density significantly surpassing both traditional and semi-solid state batteries.
Charge Rate (charging/discharging)	High	Very High
Lifespan	Long lifespan	Currently short, but research is ongoing to improve it
Production Cost	More complex than traditional batteries but less costly than full solid state, as some production processes from traditional batteries can still be used.	Complex production with high current costs, though technological advancements and large-scale production are expected to lower costs.

Advantages of Semi-Solid State Batteries

High energy density:
The energy density of liquid lithium-ion batteries is generally around 300Wh/kg to 400Wh/kg. In contrast, semi-solid state batteries have a theoretical energy density of up to 700Wh/kg, nearly twice as high as today’s most advanced lithium batteries.
Overcoming challenges with cold (and hot) temperatures:
Semi-solid state batteries use solid electrolytes that are not affected by low temperatures, effectively addressing the issue of battery lifespan during winter for electric vehicles. qapasity’s Arctic Series also includes an integrated heating element in the battery module to maintain performance in cold conditions.
Higher safety:
Semi-solid state batteries contain significantly less liquid electrolyte, and their thick, gel-like consistency minimizes the risk of fire or explosion when damaged or punctured. This same safety feature applies to qapasity’s Arctic Series, which uses a gel-like electrolyte instead of liquid.
Longer lifespan:
Current semi-solid state batteries retain over 85% of their capacity after 2,000 cycles at room temperature. In comparison, traditional liquid batteries retain only about 80% after 1,200 cycles under the same conditions.