Simultaneous enhancement of electronic and Li+ ion conductivity in LiFePO4

Enhancing the electronic and ionic conductivity in Li compounds can significantly impact the design of batteries. Here, we explore the influence of biaxial strain on the electronic and Li+ ion conductivities of LiFePO4 by performing first-principles calculations. We find that 4% biaxial tensile strain (BTS) leads to 15 times increase in electronic conductivity and 50 times increase in Li+ ion conductivity at 300 K, respectively. Electronic conductivity is enhanced because BTS softens lattice distortions around a polaron, resulting in a reduction of the activation barrier. The extra volume introduced by tensile strain also reduces the barrier of Li+ ion migration. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.4737212]