The last few months of 2016, I wrote several posts about lithium-ion safety issues. This included reporting on the cost of the Samsung Galaxy Note 7 failure, and that it was just the latest in a series of high-profile lithium-ion battery mishaps. Previously, I had written about how Li-ion battery safety problems were the legacy of Sony’s decision to repurpose audio cassette magnetic recording tape equipment for battery production in 1991.
By contrast, our modern approach to Li-ion battery design and production combines 3D cell architecture, photolithography and solar-grade wafer production. This virtually eliminates the possibility of thermal runaway that has produced the fiery failures of conventional Li-ion batteries in smartphones, laptops, hoverboards, and even passenger aircraft.
We decided to test this thesis by comparing our prototype cell for a wearable device with a comparable commercial Li-ion cell. We intentionally created a highly unlikely, precarious scenario. We overcharged a conventional 130 mAh Li-ion cell and our 100 mAh 3D silicon Li-ion cell to 250% of capacity and simultaneously punctured the package of each. As the video shows, the conventional Li-ion cell burst into flames, while our 3D silicon Li-ion cell did not experience thermal runaway or its dangerous and potentially damaging result.
Let me be clear, the point of this test is not to show that a conventional Li-ion cell can be driven to thermal runaway and a resulting fire when subjected to what, by my own admission, is a highly unlikely combination of overcharging and package rupture. Rather, the point is that when our cell was subjected to the same extraordinary conditions, it did not undergo thermal runaway and erupt into flames. This is because our 3D cell architecture incorporates several safety features which are not obtainable with a conventional Li-ion cell structure.
- The cell architecture allows for a ceramic separator that tolerates higher temperatures than the polymeric separator in a conventional Li-ion battery.
- Surplus capacity in our patented silicon anode reduces the risk of lithium metal plating during overcharge conditions.
- Distributed collectors limit current if an electrical short occurs.
- A walled off cathode limits propagation of material breakdown.
In addition, high thermal dissipation of our 3D cell mitigates local cell hot spots. Collectively, the features of our 3D cell architecture significantly reduce the possibility of thermal runaway and the danger of a resulting explosion or fire.