A Better Battery for EVs?

A new type of lead-acid battery could give more sophisticated, and expensive, batteries like nickel-metal-hydride or lithium-ion competition for use in battery and hybrid electric vehicles. That's one goal of Firefly Energy Inc., a spin-off of Caterpillar, the industrial machine and engine manufacturer that's made significant research and development investments in an effort to come up with better batteries for its heavy-duty equipment.

 

Firefly's Microcell technology uses carbon-graphite foam grids impregnated with a lead oxide slurry rather than traditional heavy lead metal grids.  The resulting negative and positive plates have greatly increased surface areas compared to conventional lead-acid grid structures. This means greater active material utilization levels of 70-90 percent compared to today's 20-70 percent, as well as enhanced fast-recharge capability. The large surface area doesn't corrode like a two-dimensional grid.

 

Other benefits include reduced weight and simpler manufacturing. The carbon-graphite foam dissipates heat very efficiently so the Firefly battery also operates much cooler, which means longer life. This battery technology allows putting out 70 percent of its maximum power even at 0 degrees F, an important distinction since reduced cold weather capacity is a major drawback for ordinary lead-acid batteries. Reducing lead content has environmental benefits in itself, and what lead is used can be recovered and reused. The carbon-graphite foam serves as a fuel that increases the lead smelting temperature to make the process more efficient.

 

The company's two technologies, 3D and 3D2, use the porous three dimensional material in either flooded or VRLA (valve-regulated lead acid) battery designs. In the 3D, the negative lead metal grids are replaced with the graphite foam. The positive lead metal grids are also replaced in the 3D2. Husqvarna, the company's first customer, plans to use the Firefly battery in its battery-powered outdoor lawn and garden equipment. A timeline for automotive applications has not been identified.