Hidden atomic distortions explain why promising lithium battery cathodes waste energy

A team of battery researchers has traced one of the most stubborn problems in next-generation lithium batteries to a surprisingly subtle source: the way individual metal atoms sit slightly off-centre inside their oxygen cages. In a study published in Nature Nanotechnology, Yu Mei of Central South University and colleagues show that atomic-scale structural distortion and nanoscale short-range ordering together govern the voltage hysteresis that plagues lithium-rich cation-disordered rocksalt cathodes, a class of materials widely viewed as strong candidates for high-capacity positive electrodes in lithium metal batteries.

Potential hysteresis is the gap between the voltage at which a battery charges and the lower voltage at which it discharges. Every rechargeable cell shows some of it, but in lithium-rich disordered rocksalt materials the gap can be pronounced, meaning that a substantial fraction of the electrical energy pumped into the battery during charging is never recovered during discharge. That lost energy is dissipated as heat, lowering round-trip energy efficiency and complicating thermal management. For a technology whose appeal rests on packing more energy into the same volume, a large and poorly understood hysteresis is a serious obstacle to commercialisation.

Cation-disordered rocksalt compounds, often abbreviated DRX, break with the ordered crystal structures that dominate today’s lithium-ion cathodes. Instead of arranging lithium and transition metal ions on neat, alternating planes, DRX materials scatter them almost randomly across the same lattice sites. The disorder is a feature, not a bug: it frees designers from the strict compositional rules of layered oxides and allows lithium-rich formulations that store charge both in transition metal redox reactions and in the oxidation of lattice oxygen itself, the so-called anionic redox that underpins their exceptional capacities.

Yet the same structural freedom that unlocks capacity also makes DRX cathodes notoriously difficult to understand. During battery operation the material evolves in complicated ways, and previous work has implicated transition metal migration, oxygen-oxygen bond formation, trapped molecular oxygen and ligand-to-metal charge transfer in the voltage hysteresis. Because so many processes overlap, the field has struggled to separate the thermodynamic contributions, which reflect genuine differences in the energy landscapes of charged and discharged states, from the kinetic contributions, which arise when lithium transport and structural relaxation lag behind the applied current.

The new study tackles this ambiguity by comparing two closely related model compounds, one containing niobium and one that does not, through an unusually broad suite of characterisation techniques. The team combined synchrotron X-ray absorption spectroscopy, X-ray pair distribution function analysis and neutron pair distribution function measurements to probe structure from the longest length scales down to individual atomic bonds, supplemented by scanning transmission electron microscopy to image nanoscale domains directly and by density functional theory calculations to interpret what the experiments revealed.

The central finding concerns the stereochemistry of d0 transition metals, ions such as niobium in its highest oxidation state whose d electron shells are empty. Decades of solid-state chemistry have shown that such ions tend to shift away from the centre of their octahedral oxygen coordination, an out-of-centre distortion driven by the pseudo Jahn-Teller effect, a vibronic instability in which low-lying electronic states couple to atomic displacements. In the niobium-containing compound, the researchers found that these distorted octahedra disrupt the cation short-range order that would otherwise develop in the nominally disordered lattice.

That disruption turns out to matter enormously for performance. Short-range order in DRX materials is a double-edged sword: it can stabilise the lattice, but it can also block the percolating network of face-sharing tetrahedral sites through which lithium ions must hop to move through the crystal. By breaking up ordered domains, the out-of-centre distortion of the niobium octahedra opens a more connected lithium percolation pathway, allowing charge and discharge to proceed more reversibly at high rates. In effect, a purely geometric quirk of empty d-shell ions acts as a kinetic lever on the whole electrode.

The pseudo Jahn-Teller effect also operates on the thermodynamic side of the hysteresis ledger. The team’s spectroscopic and computational results indicate that the distortion weakens the ligand-to-metal charge transfer process associated with the nickel-oxygen bonds, the electronic event that couples nickel redox to oxygen redox and has previously been linked to large voltage gaps. With that coupling softened, the oxidation and reduction of lattice oxygen become more reversible, so the energy stored in charged oxygen species is more faithfully returned on discharge. In the niobium-containing DRX electrode, both the kinetic and thermodynamic components of the potential hysteresis in lithium metal cells were effectively mitigated.

The significance of the work lies in its multiscale framing. Rather than attributing hysteresis to a single culprit, the researchers demonstrate that phenomena at very different length scales are entangled: an atomic displacement of a fraction of an angstrom remodels nanoscale chemical ordering, which in turn reshapes both the thermodynamics of oxygen redox and the kinetics of lithium transport. Disentangling these contributions required correlating electrochemical measurements with structural probes across scales, an approach the authors suggest should become standard practice for evaluating DRX chemistry.

For battery designers, the message is actionable. The choice of redox-inactive, d0 transition metals is not merely a way to tune capacity or stability; it is a stereochemical tool that can be used deliberately to sculpt local structure. Compounds engineered so that distorted octahedra suppress deleterious short-range order could deliver the high capacities of lithium-rich disordered rocksalt cathodes without the energy efficiency penalty that has held them back. As lithium metal anodes mature, pairing them with hysteresis-minimised DRX cathodes brings the industry a step closer to batteries that store more energy and waste less of it on every cycle.

Subject of Research: Stereochemical origins of voltage hysteresis in lithium-rich cation-disordered rocksalt battery cathodes

Article Title: Stereochemical origin of potential hysteresis in lithium metal batteries with lithium-rich cation-disordered rocksalt positive electrodes

Article References: Mei, Y., Xia, F., Chen, H., Li, Y., Gao, J., Zhu, K., He, L., Wu, S., Li, H.-F., Fan, L., Zhan, C., Ni, L., Wang, H., Jian, W., Wang, K., Silvester, D. S., Banks, C. E., Wu, J., Deng, W., … Ji, X. (2026). Stereochemical origin of potential hysteresis in lithium metal batteries with lithium-rich cation-disordered rocksalt positive electrodes. Nature Nanotechnology. https://doi.org/10.1038/s41565-026-02301-2

Image Credits: AI Generated

DOI: 10.1038/s41565-026-02301-2

Keywords: lithium metal batteries, cation-disordered rocksalt, voltage hysteresis, anionic redox, pseudo Jahn-Teller effect, short-range order, d0 transition metals, niobium, lithium percolation, cathode materials, energy efficiency, Nature Nanotechnology