Unsupported claims of ultrafast charging of LiFePO4 Li-ion batteries

Energy storage by batteries has become an issue of strategic importance. A scientific breakthrough in this context is the lithiumion battery. Indeed, lithium-ion batteries can store up to three times more electricity and generate twice the power of nickel–metalhydride batteries now in use, making possible great improvements in energy storage for electric vehicles and portable electronics. Major investments are beingmadefor thecommercial development of Li-ion batteries and there are government funds available offering $billions in grants for research, development, and manufacturing. In this context, we wish to call attention to a deceptive paper that recently appeared in Nature [1], which has receivedmuch publicity since it announced an impossibly high recharging rate capability for a Li-ion battery of 9 s! Close examination of the work [1] shows that the authors have no direct evidence in support of such a high recharging rate, but imply their dramatic conclusion only from the high discharge rate. Experienced batterymaterials scientistswould understand that the charge and discharge processes of batteries are basically asymmetric, resulting in rates of discharge that are generallymuch higher than rates suitable for recharge! The ability of a battery to be rechargedina fewseconds, as the authors claim,would indeed be of great benefit, but this goal remains unmet despite the claims of Kang and Ceder [1] as we will explain herein. The olivine material LiFePO4, used in thework reported by Kang and Ceder [1] is a very promising material that was first proposed in 1996 [2]. Hydro Quebec (HQ) recognized the potential of this material for Li-ion batteries after discussions with Professor John Goodenough in the same year. HQ has much experience with this material and has invested in R&D to promote this material for battery applications in order to make it practical for lithium rechargeable batteries by coating it with carbon [3].