LIFEPO4 Battery Safety

  |   Lithium Battery Safety

 

The safety issues and subsequent recall occurring with the Samsung Galaxy smartphone can potentially enhance public skepticism concerning the widespread usage of Lithium ion batteries. Since we at Dragonfly Energy consider it our mission to facilitate the mass proliferation of energy storage – particularly Lithium ion batteries – it behooves us to make a statement about these current events.

 

The problems that are plaguing Samsung stem from the desire for smartphones to perform more energy intensive tasks within a smaller form factor and on a battery that lasts a long time on a single charge. This means that the battery must hold more energy in a smaller volume. It must be “energy dense”. The battery must therefore use the most energy dense material (i.e. a Lithium metal oxide cathode). It also means that the assembly of the phone includes a production step that compresses the battery, so that it fits into the case. It is likely that this compression may have triggered an internal short-circuit, which became more prominent over time due to cycling of the battery or just handling of the phone. At some point this short-circuit produces enough internal heat to worsen the short-circuit and ultimately cause thermal runaway. This condition is much more accessible using the more energy-dense materials, like Lithium metal oxides.

 

In Samsung’s defense, increasing the energy density of batteries represents the cutting edge of Li-ion battery technology. It’s what makes devices last longer and electric vehicles go farther on a single charge. As technology continues to evolve, the envelope will get pushed and growing pains will happen. Fortunately, in the case of Samsung, the problem was detected and the recall initiated prior to there being any casualties. Samsung is a large and diverse company and will survive, even as their short-term attempt to compete with the iPhone suffers.

 

By comparison, Dragonfly Energy is not pushing the limits of safety by squeezing more energy into a smaller volume. We are currently producing a line of deep cycle Lithium ion batteries that we believe will completely displace lead-acid batteries for deep cycle applications. Our challenge is to create a product that is safer, more energy dense, less toxic, less corrosive, more cost effective, and more environmentally friendly than lead-acid. Fortunately, these criteria are less stringent, in that we are not directly competing with gasoline engines, nor are we trying to produce the most energy-dense battery on the market. This allows us to select the safest and most stable Li-ion materials – such as our choice of Lithium iron phosphate as the cathode material. Lithium iron phosphate is known to be much safer than Lithium metal oxides, because the breakdown temperature of the material is much higher (662 F for Lithium iron phosphate, compared to 150 C for Lithium metal oxides). When the cathode decomposes thermally, oxygen is released inside the cell, increasing the potential for explosions or fires. This is much less likely to happen in our cells.