As demand for rechargeable batteries grows, the need for sustainable and cost-effective materials to improve their lifespan and performance becomes increasingly critical. The next-generation lithium-ion batteries are being designed with new cathode active materials for high-performance energy storage that avoid hazardous materials like cobalt. Among the most promising positive electrode candidates are nickel-rich layered oxide materials. However, these materials face significant challenges in long-term stability due to structural degradation. A crucial yet frequently overlooked factor affecting their stability is the precise positioning of lithium atoms within the lattice—a characteristic extremely difficult to determine due to lithium's weak interaction with standard X-ray methods.

A recent study published in Nature Communications addresses this challenge with advanced characterization techniques, including synchrotron X-ray and neutron diffraction, to analyse and optimize lithium distribution within nickel-rich electrodes. This work was a collaborative effort involving scientists from Shenzhen and Shanxi Universities (China), ICN2, and ICREA (Spain) alongside scientists from the ALBA Synchrotron, the Institute Laue-Langevin (France), the Karlsruhe Institute of Technology (Germany) and the UM6P (Morocco).

By adjusting lithium incorporation and adding multiple high-valence dopants (Nb⁵⁺, W⁶⁺, Mo⁶⁺), researchers identified two electrode materials with better durability and stability. The optimization of the material performance was also achieved by creating superlattice domains, that is ensuring that the distribution of the lithium ions is not random. Small changes in lithium occupancy in nickel-rich positive electrodes can significantly enhance electrochemical performance.  

Researchers examined the internal structure of these electrodes with a variety of techniques and synchrotron facilities. In particular, researchers monitored the real-time structural evolution of the nickel-rich positive electrodes during battery operation using in situ synchrotron X-ray diffraction (SXRD) at the MSPD beamline at ALBA. The high-resolution diffraction patterns provided by this beamline allowed the tracking of lithium positioning as well as of their phase transitions and lattice changes.

“The ability to study electrodes under operating conditions was critical to show how lithium occupancy influences stability and performance, which are both key parameters for the development of more durable Li-ion battery materials”, says Alexander Missyul, beamline scientist at MSPD.

This work identified two optimized electrode materials with important gains in battery cyclability. The first, with a lithium content of 1.08, stabilized the lithium/nickel exchange, and improved mechanical durability. The second, with a lithium content of 1.20, promoted oxygen redox activity, which helped electrode integrity at higher voltages. Both materials demonstrated a capacity retention of over 90% after extended cycling, significantly outperforming conventional nickel-rich electrodes.

“By using a novel lithium-regulation strategy and state-of-the-art synchrotron characterization methods, we have shown how the control of structural defects in lithium-ion battery materials can improve the electrochemical properties and stability of nickel-rich electrodes. These findings pave the way for durable, high-energy-density lithium-ion batteries for large-scale energy storage”, says researcher Hang Li from KIT Institute for Applied Materials -Energy Storage Systems.

Schematic illustration of the different structural models for nickel(Ni)-rich positive electrode materials. The double arrows represent locations where lithium(Li)/Ni exchange takes place, and the single arrows highlight where Li appears in Transition Metal (TM) layers.

2D contour pattern of the in situ SXRD of 102 (a.) and RM (b.) cathodes. The corresponding SXRD patterns are displayed on the left side (λ = 0.4139 Å). The location of the 003 reflections in the pristine state and SoC 81% are labelled.