Ray works on modeling and simulation of porous battery materials with complex (phase separating) thermodynamics. He has done work on phase separating materials which are used both in negative and positive battery electrodes, and he couples these materials to full porous battery electrodes which exchange ions between the electrodes via an electrolyte through the battery separator. His work on LiFePO4 (positive electrode), in collaboration William Chueh's group at Stanford for experimental results, helped show a transition from a particle-by-particle filling to a concurrent filling of electrode active particles as current transitions from low to moderate rates. These results helped resolve a highly debated question in the literature about how many particles are typically actively supplying the total applied current. More recently, Ray has studied graphite (negative electrode) phase behavior in collaboration with Louis Brus's group at Columbia University. From this work, using a simple 2-layer free-energy-based model, they were able to directly capture the visually observed phase behavior of a far-from-equilibrium graphite particle as it was filled with lithium (see figure).