Journal Article

Battery materials for ultrafast charging and discharging

Ceder, Gerbrand, Kang, Byoungwoo

2009

Overview

High-speed batteries Batteries are thought of as having high energy density but low power rates, while for fast-discharging supercapacitors the opposite is true. Byoungwoo Kang and Gerbrand Ceder have now developed a lithium-ion battery that challenges that assumption, discharging extremely rapidly and maintaining a power density similar to a supercapacitor, two orders of magnitude higher than a normal lithium-ion battery. This is achieved by modifying LiFePO 4 , a material widely used in batteries. The starting point is nanosized LiFePO 4 , which already gives relatively fast discharge rates, which is then coated with a similar compound that is slightly Fe,P,O-deficient. On heating, the coating forms a glassy top layer that enhances lithium-ion mobility. The performance of batteries based on this technology could lead to new applications for electrochemical energy storage. This paper demonstrates a lithium-ion battery that discharges extremely fast and maintains a power density similar to a supercapacitor, two orders of magnitude higher than a normal lithium-ion battery. The storage of electrical energy at high charge and discharge rate is an important technology in today’s society, and can enable hybrid and plug-in hybrid electric vehicles and provide back-up for wind and solar energy. It is typically believed that in electrochemical systems very high power rates can only be achieved with supercapacitors, which trade high power for low energy density as they only store energy by surface adsorption reactions of charged species on an electrode material 1 , 2 , 3 . Here we show that batteries 4 , 5 which obtain high energy density by storing charge in the bulk of a material can also achieve ultrahigh discharge rates, comparable to those of supercapacitors. We realize this in LiFePO 4 (ref. 6 ), a material with high lithium bulk mobility 7 , 8 , by creating a fast ion-conducting surface phase through controlled off-stoichiometry. A rate capability equivalent to full battery discharge in 10–20 s can be achieved.

• Publisher: Nature Publishing Group UK,Nature Publishing Group
• Subject: Alternative energy sources / Applied sciences / Batteries / Carbon black / Direct energy conversion and energy accumulation / Electric vehicles / Electrical engineering. Electrical power engineering / Electrical power engineering / Electrochemical conversion: primary and secondary batteries, fuel cells / Electrochemistry / Electrodes / Exact sciences and technology / Humanities and Social Sciences / Iron / letter / Lithium / Lithium cells / Lithium compounds / Materials / multidisciplinary / Phosphorus content / Scanning electron microscopy / Science / Science (multidisciplinary) / Solar energy / Transmission electron microscopy