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Technical Guidance
Semi-Solid Battery Safety: Nail Penetration, Overcharge & Thermal Runaway Test Results
At PPCELL, we believe that next-generation battery technology must deliver both high energy density and uncompromising safety. Our 350Wh/kg semi-solid soft pack cells have been rigorously tested under extreme abuse conditions to validate their intrinsic safety advantages over conventional liquid-electrolyte lithium-ion batteries.
Why Safety Testing Matters
Conventional lithium-ion batteries contain flammable organic electrolytes. In the event of an internal short circuit (e.g., from nail penetration, crush, or manufacturing defects), localized heating can trigger thermal runaway – a self-sustaining chain reaction that leads to fire or explosion.
PPCELL’s semi-solid technology replaces most of the liquid electrolyte with a non-flammable gel-like matrix. The following tests demonstrate how this architecture fundamentally changes the safety profile of high-energy-density cells.
Test 1: Nail Penetration – Simulating the Worst-Case Internal Short Circuit
Test Method
Cell type: PPCELL semi-solid pouch cell, 29.5Ah, 350Wh/kg
State of charge: 100% (fully charged, 4.2V)
Nail: φ3mm high-temperature steel needle
Penetration speed: 20mm/s
Ambient temperature: 25±5°C
Test Results
| Observation | Result |
|---|---|
| Instantaneous voltage drop | Yes (from 4.2V to near 0V) |
| Smoke generation | None |
| Fire | No fire |
| Explosion | No explosion |
| Maximum cell surface temperature | 68°C |
| Thermal propagation to adjacent cells | None |
Analysis
Within seconds of nail penetration, the semi-solid electrolyte prevented rapid exothermic reactions. Unlike conventional cells that often vent flames within 2‑5 seconds, the PPCELL semi-solid cell showed no visible smoke or fire. The peak temperature of 68°C remained far below the thermal runaway threshold (>150°C). The test was repeated ten times with identical results – zero failures.
Test 2: Overcharge – Pushing Beyond Safe Voltage Limits
Test Method
Cell: PPCELL semi-solid pouch cell, starting at 100% SOC
Charging current: 0.5C (14.75A)
Cut-off condition: 6.0V or until fire/explosion
Test Results
| Voltage Stage | Observation |
|---|---|
| 4.2V → 5.0V | Normal, slight temperature rise |
| 5.0V → 5.5V | Safety vent opened; gas released |
| 5.5V → 6.0V | No fire, no explosion |
| Maximum temperature | 82°C |
| Post-test cell condition | Swollen but intact, no electrolyte leakage |
Analysis
Conventional liquid-electrolyte cells typically fail catastrophically between 4.5V and 5.0V due to electrolyte decomposition and internal pressure buildup. PPCELL’s semi-solid cell survived up to 6.0V – a 30% higher overcharge tolerance. The safety vent functioned correctly, releasing gas without fire, demonstrating an extra safety margin against charger or BMS malfunctions.
Test 3: Thermal Runaway Propagation – Does One Cell Take Down the Pack?
Test Method
Module configuration: 3 cells in series (3S1P)
Trigger: Nail penetration of the middle cell
Monitoring: Temperature sensors on all three cells and module enclosure
Test Results
| Cell / Location | Peak Temperature | Fire/Explosion |
|---|---|---|
| Trigger cell (middle) | 71°C | No fire |
| Adjacent cell (left) | 42°C | No fire |
| Adjacent cell (right) | 44°C | No fire |
| Module enclosure | 38°C | – |
Analysis
In conventional modules, thermal runaway propagation is a major safety concern – one cell’s failure triggers its neighbors, potentially engulfing an entire battery pack. In this test, even the triggered PPCELL semi-solid cell did not reach thermal runaway temperatures. Adjacent cells experienced only a mild temperature rise (42‑44°C), well within normal operating limits. This confirms that PPCELL semi-solid cells are inherently non‑propagating – a critical advantage for electric vehicle (EV) and energy storage system (ESS) applications.
Comparison: PPCELL Semi-Solid vs. Conventional Li-Ion Safety
| Test | Conventional Li-Ion (NMC) | PPCELL Semi-Solid Pouch Cell |
|---|---|---|
| Nail penetration | Fire within 2‑5 seconds | No fire, no smoke |
| Overcharge tolerance | 4.5‑5.0V | 6.0V+ |
| Thermal runaway propagation | Often propagates | No propagation |
| Peak temperature (nail penetration) | >400°C | <70°C |
| Post-test cell condition | Destroyed, burned | Intact, swollen but safe |
How PPCELL Semi-Solid Technology Achieves Superior Safety
The safety advantages come from three key innovations:
Non-flammable gel electrolyte – The semi-solid matrix contains no free liquid that can ignite. Even when heated, it does not produce flammable vapor.
High-temperature resistant separator – A ceramic‑coated separator maintains dimensional stability at elevated temperatures, preventing internal short circuits.
Intrinsic cathode stability – Our cathode materials are formulated to suppress oxygen release, removing the fuel source for thermal runaway.
Implications for Real‑World Applications
Electric Vehicles (EVs)
No thermal propagation means a single cell failure will not destroy the entire battery pack.
Higher overcharge tolerance provides a safety buffer against charger or BMS faults.
No fire during nail penetration dramatically reduces the risk of post-crash vehicle fires.
Energy Storage Systems (ESS)
Non‑propagating design allows simpler, lower-cost fire suppression systems.
Stable at elevated temperatures reduces cooling requirements and operating costs.
Passed nail penetration ensures safety even under extreme mechanical abuse.
Drones & UAVs
350Wh/kg high energy density with safety – no trade-off.
No fire risk during crash landings or propeller strikes that might damage the battery.
Industry Standards & Certifications
All PPCELL semi-solid cells have passed the following safety tests according to GB 31241 and enterprise standards:
| Test | Result |
|---|---|
| External short circuit | No fire, no explosion |
| Overcharge (up to 6.0V) | No fire, no explosion |
| Forced discharge | No fire, no explosion |
| Crush | No fire, no explosion |
| Nail penetration | No fire, no explosion |
| Temperature cycling (-40°C ↔ 85°C, 5 cycles) | No fire, no explosion |
| Low pressure (≤11.6kPa) | No fire, no explosion |
Conclusion
PPCELL’s semi-solid battery technology delivers a step-change in safety compared to conventional lithium-ion cells. Independent nail penetration, overcharge, and thermal runaway propagation tests consistently show no fire, no explosion, and minimal temperature rise – even under extreme abuse conditions.
For engineers and product managers evaluating next‑generation batteries, PPCELL semi-solid offers the pragmatic path: 350Wh/kg high energy density combined with proven safety, available today.