How 21700 Lithium Cell Pass Puncture Testing Without Catching Fire?

Blog | Published by Alex on July 30, 2025

The Solutions

To ensure that 21700 lithium batteries can pass puncture testing without catching fire, manufacturers typically make improvements in several key areas:

Enhanced Battery Casing Design

High-Strength Casing Materials:

Using stronger metals (such as stainless steel, aluminum alloys) or composite materials for the battery casing effectively increases the battery's puncture resistance. These materials' high strength and toughness help reduce the damage caused by external objects, preventing internal short circuits.

Multi-Layer Protection Design:

Some 21700 batteries feature multi-layer protective casings. The layers are filled with shock-absorbing materials that provide extra cushioning when punctures occur, preventing short circuits inside the battery and reducing the risk of thermal runaway.

Optimized Separator and Electrolyte

Puncture-Resistant Separator:

The separator is an essential component of the battery that prevents short circuits between the anode and cathode. By using high-strength, puncture-resistant separator materials (such as ceramic-coated separators or reinforced polyolefin separators), the risk of short circuits after puncture can be significantly reduced.

Stable Electrolyte:

The stability of the electrolyte is crucial for determining the safety of the battery. By using low-flashpoint and chemically stable electrolytes, the likelihood of chemical reactions within the battery after puncture is minimized, thereby reducing the risk of fire.

Solid-State Electrolyte Technology

Solid-State Electrolyte Batteries:

Solid-state electrolyte batteries use solid electrolytes instead of traditional liquid electrolytes. These batteries do not contain liquid components, meaning that puncturing the battery will not lead to electrolyte leakage, thus preventing fires caused by electrolyte spills. Additionally, solid-state electrolytes typically offer higher thermal stability, maintaining safety even after puncture.

Ion-Conductive Solid Electrolytes:

Materials used in solid-state electrolytes (such as sulfides, oxides, or polymers) are stable over a wide temperature range, helping reduce thermal runaway triggered by punctures.

Thermal Management and Thermal Runaway Protection

Thermal Isolation Layers:

Using excellent heat-conductive materials (like graphite, aluminum foil, etc.) as thermal isolation layers inside the battery helps dissipate heat quickly and prevents localized overheating that could lead to thermal runaway.

Thermal Mitigation Materials:

Some manufacturers incorporate thermal mitigation materials into the battery, which can absorb excess heat when the battery's temperature rises abnormally, effectively reducing the internal temperature and preventing fire.

Optimized Internal Battery Structure

Multi-Layer Isolation Design:

To prevent short circuits after puncture, some manufacturers use a multi-layer isolation design. By adding multiple separator layers inside the battery, the risk of direct contact between the positive and negative electrodes is minimized when the battery is subjected to external shocks, thus reducing the possibility of short circuits.

Self-Extinguishing Design:

Some batteries incorporate self-extinguishing technology, which automatically cuts off the current path when the battery overheats or experiences a short circuit. This prevents the further spread of thermal runaway.

Closing Remarks

As a high-energy-density battery, the safety of 21700 lithium batteries under extreme conditions such as puncture is of paramount importance. By optimizing the battery casing design, enhancing the puncture resistance of separators, adopting solid-state electrolyte technology, and improving thermal management, the safety of 21700 batteries can be effectively enhanced, preventing fires or explosions caused by short circuits or thermal runaway. With continuous advancements in related technologies, future 21700 lithium batteries will demonstrate even higher safety in high-power applications, driving their widespread use in electric vehicles, energy storage systems, and other fields.