Towards innovative electrode materials obtained by high-pressure: Experimental and computational study of HP-FePO4

In the search for new electrodes for lithium batteries processing under high pressure opens new paths to innovative materials. The High Pressure (HP) polymorph of α-FePO4 crystallizes in the CrVO4 structural-type; first principles calculations predict that Li insertion would occur at 3.36 V. Accordingly, crystalline samples of HP-FePO4 display electrochemical activity with a lithium insertion process occurring at 3 V, which has not been observed in the α-FePO4 polymorph. This reduction process is characterized by a large cell polarization that suggests a very slow kinetics. The poor electrochemical performance of highly crystalline HP-FePO4 is favored in iron phosphate samples obtained under mild conditions of pressure and temperature, that produce a partially amorphous material and prevent an excessive particle growth.