Direct recycling of Li‐ion battery cathodes offers a sustainable and potentially cost‐effective alternative to conventional methods, often involving complex chemical processes and significant material losses. This study focuses on the relithiation of cathode materials from quality control reject (QCR) and end‐of‐life (EoL) Li‐ion cells to restore their physical structure, morphology, and electrochemical performance. Two NMC532/graphite pouch cells from the same manufacturer were studied. QCR cells, stored under ambient conditions, experienced corrosion and degradation before recycling, while EoL cells were cycled to the end of life. The cells were disassembled, and the cathode materials were delaminated using NaOH solution, then relithiated with LiOH at 700 °C for 15 hours in the air. Extensive characterization analyzed elemental composition, structural properties, thermal stability, and particle size distribution. Results indicated that relithiation successfully restored lithium content and improved the structural ordering and morphology of the cathode materials. The electrochemical performance of the relithiated cathodes exhibited good stability over 100 charge‐discharge cycles. The relithiated QCR samples achieved a capacity of 155.57 mAh g⁻¹, while EoL samples reached 152.53 mAh g⁻¹, comparable to pristine materials. This study highlights relithiation's potential to extend the lifecycle of Li‐ion cathodes, contributing to a more sustainable circular economy for battery materials.

Low value Mn based spinel from an EOL EV battery is selectively leached and upcycled to higher value next generation cathode materials.

A new synthesis route to MnNb₂O₆ and the first report of Ca_0.25Mn_0.75Nb₂O₆ has been developed using different alkaline bases under hydrothermal conditions. The Li-ion storage mechanism of the materials varies with composition and morphology.

A new synthesis route to isolate low oxidation states of transition-metal cations in niobates is developed under reducing conditions to yield a Mn²⁺ phase whose redox response with respect to lithium storage is studied.

Lithium nickel oxide (LiNiO2, LNO) is a promising Co-free cathode but suffers structural degradation at high and low voltages. Here we report the synthesis of a cation-disordered rock-salt LiNiO2 (DRS-LNO; Li:Ni ≈ 1:1) from mechanochemical treatment of layered LNO. Its electrochemical behaviour arises from the interplay between local and average structure: reverse Monte Carlo modelling of total scattering data reveals pronounced Li–Li and Ni–Ni clustering (Warren–Cowley α ^(NiLi) = 0.054(4)) and expanded Li–O distances, enabling Li diffusion pathways that allow ~70% of Li to participate in long-range transport. This accounts for the unexpectedly high first-cycle charge capacity of 185(9) mAh g ^-1 at 10 mA g ^-1 despite the absence of Li excess. The disordered average structure leads to small isotropic volume changes (~2.1%) over large electrochemical windows, also accessing reversible capacity from low-voltage Ni ³⁺ /Ni ²⁺ redox at low voltages. Operando total scattering suggests that reversible Ni migration takes place at high delithiation, forming regions of α-NaFeO2-like local order. On discharge, the reduction from Ni ³⁺ to Ni ²⁺ is associated with the reversible formation of a secondary phase whose formation can be partially suppressed at higher current densities, with implications in the cycling stability of DRS-LNO. These results show that mechanochemistry can access unique local structural motifs that tune electrochemical behaviour, expanding the design space for next-generation cathodes.

Lithium tantalum phosphate (LiTa ₂ PO ₈ ) is among the fastest oxide Li ⁺ conductors, yet the relationship between the disordered Li ⁺ substructure and ion transport remains unclear owing to the coexistence of competing structural models and the lack of local experimental probes of Li ⁺ dynamics. Here, we combine powder neutron diffraction (PND), bond valence site energy (BVSE) calculations and muon spin relaxation (μ ⁺ SR) spectroscopy to establish a microscopic picture for Li ⁺ diffusion. Rietveld refinement of the structure using the PND data indicates that the Li ⁺ substructure is best described with two partially occupied sites, while BVSE identifies low-energy 1D diffusion channels that become interconnected to form a 3D percolating network. μ ⁺ SR reveals two thermally activated dynamical regimes, corresponding to localized Li ⁺ hopping at low temperatures and long-range diffusion above 210 K, with an activation energy of 0.300(25) eV. Combining the refined crystal structure with the μ ⁺ SR hopping rates yields a Li ⁺ self-diffusion coefficient of 5.4 × 10 ^-10 cm ² s ^-1 at 290 K, thereby providing a unified structural and dynamical description of Li ⁺ transport in LiTa ₂ PO ₈ .