What is Semi-Solid 21700 Battery?

Blog | Published by Alex on October 28, 2025

About 21700 Semi-Solid Battery

The semi-solid 21700 battery is a new type of battery technology that falls between conventional 21700 battery (with liquid electrolytes) and all-solid-state 21700 battery. It primarily uses high-concentration electrolytes or gel-like electrolytes, reducing the amount of liquid electrolyte. This design suppresses lithium dendrite growth and lowers the risk of thermal runaway, thereby enhancing battery safety while maintaining high energy density and good cycle performance. Compared to conventional 21700 battery, semi-solid batteries offer superior leakage prevention, fire resistance, and thermal stability, while being easier to manufacture and commercialize than full solid-state batteries. Semi-solid 21700 battery standard size is 21 mm in diameter and 70 mm in length, widely used in electric vehicles (EVs), power tools, and energy storage systems due to its high capacity and energy density.

What is the Structure of Semi-Solid 21700 Battery?

The positive electrode (cathode) of a semi-solid 21700 battery typically uses NCM, LFP, or NCA materials (with NCA being less common), offering high specific capacity and stable cycling performance. The negative electrode (anode) is usually graphite or silicon-carbon composite to enhance capacity and rate capability. The semi-solid electrolyte fills the space between the electrodes, providing ionic conductivity through high-concentration salt solutions or gel form. This design ensures sufficient ion transport while reducing electrolyte fluidity, which helps prevent thermal runaway and electrolyte leakage, enhancing safety. The separator is usually made of polyolefin materials, 0.03–0.05 mm thick, to accommodate the viscosity and interface characteristics of the semi-solid electrolyte. Multi-layer PE/PP composite films are preferred for improved thermal stability.

What is the Advantages of Semi-Solid 21700 Battery?

1. Enhanced Safety: Even under high temperature or extreme conditions such as puncture, semi-solid 21700 batteries are less likely to catch fire or explode.

2. Higher Energy Density: By reducing liquid content and optimizing electrode structures, energy density increases by roughly 5–10%, allowing greater capacity without increasing battery size—ideal for EVs and high-performance energy storage systems.

3. Longer Cycle Life: High-concentration electrolytes and gel interfaces reduce side reactions and slow electrode degradation, enabling 2,000–3,000 deep cycles under normal usage conditions.

4. Good Temperature Adaptability: Semi-solid electrolytes maintain relatively high ionic conductivity at low temperatures, outperforming all-solid-state 21700 batteries in cold environments, though still slightly below conventional liquid electrolyte 21700 batteries.

Manufacturing Challenges and Costs of Semi-Solid 21700 Battery

Producing semi-solid 21700 battery is more complex, requiring precise control of electrolyte uniformity and electrode interface contact to prevent increased internal resistance and reduced rate performance. Production costs are 10%–20% higher than conventional 21700 battery.

Rate Capability: Semi-Solid 21700 Battery VS Conventional 21700 Battery VS All-Solid-State 21700 Battery

Semi-solid 21700 battery offer higher charge/discharge rate performance than full solid-state batteries but are slightly lower than or comparable to conventional 21700 battery.

Semi-Solid 21700 Battery Applications

These batteries are primarily used in electric vehicles (EVs), autonomous vehicles (AVs), energy storage systems (ESS), drones, FPV, and more.
Semi-solid 21700 battery serve as an important transitional technology between conventional and full solid-state 21700 battery.

Where to buy high-quality 21700 battery?

Joinsun has extensive experience in 21700 battery manufacturing and has successfully developed 4000mAh 4Ah 3C-Rate 12A 21700 battery (NCM Lithium / UL, FCC, CE, CB, IEC, BIS, PSE, CCC, BSMI). You are welcome to reach out to the Joinsun sales team for detailed information on pricing and technical documents.

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