Iron is catching up to cobalt in lithium-ion batteries

Lithium-ion batteries made it to where they are today—in cars, phones, and computers—thanks to cobalt. But cobalt’s price is in flux, and its mining operations are marred by reports of child labor and human rights abuses. More abundant, less expensive iron could curb battery makers’ reliance on cobalt. Yet batteries using iron-based cathode materials, such as lithium iron phosphate, LiFePO₄, lag behind their cobalt-containing counterparts in terms of performance. Fujitsu Laboratories has now unveiled batteries using lithium iron pyrophosphate cathodes that match the voltage supplied by conventional cobalt-based devices, according to a press release. Using a proprietary process, Fujitsu created Li_5.33Fe_5.33(P₂O₇)₄ crystals in which iron-oxygen clusters are distorted compared with the regular octahedrons of lithium iron phosphate. This crystal structure likely helps batteries hit higher voltages. Furthermore, the structure could be optimized to help iron-based materials catch up to cobalt in other areas, such as charge capacity, says Fujitsu research manager Shintaro Sato. Karim Zaghib, who develops lithium-ion technology for the energy supplier Hydro-Québec, commends the work, saying the new material is a good addition to research efforts aimed at minimizing cobalt in batteries.