Spin-Lattice Coupling Studies of Electrode Material for 2nd Battery

Crystal and Magnetic structure of second battery electrode materials using neutron power diffraction is essential because of its sensitivity to observe the light element atom such as Li, Na and O. It is very important to define a position and occupation of conduction ion(Li-ion) for recognizing their reaction mechanisms.  To do further advanced research combined Rietveld refinement and MEM (Maximum Entropy Method) is revealed the useful information for understanding the conduction mechanism.

 By detailed structural analysis of electrode materials for rechargeable battery with neutron powder diffraction, we should understand an iso-structural change such as an oxygen ion tilting, a change of bond distance and an occupation variation etc. for studying the conduction mechanism. An iso-structural change in electrode is appeared by the charging/discharging, size-control, doping and spin ordering process. The control of iso-structure change as functions of several external conditions is very substantial to realize next generation 2^nd battery with high-capacity, high-efficiency and good-safety.  In this study, we have investigated the magnetic and crystal structure of electrode Na_xFe₃(PO₄)₂(P₂O₇) using neutron powder diffraction. We have observed that the spin ordering of Fe induces the iso-structure change of Na_xFe₃(PO₄)₂(P₂O₇). Even though the spin ordering of this material is happened at a very low temperature, the imagination about correlation between crystal and magnetic structure in electrode should be proposed us the clue to realize the new concept’ 2^nd battery which the conduction property of electrode can be controlled by the spin ordering of magnetic ion.