Ren's research interests focus on phase transitions and the structure-property studies of correlated electron systems, engineered materials, nanoparticles and nanocomposites, and energy storage and conversion materials. He utilises synchrotron X-ray and neutron scattering alongside other techniques. He has published over 950 peer-reviewed articles in Nature, Science, Physical Review Letters and other prestigious journals. He is a Clarivate Highly Cited Researcher (2022, 2023).