Bo Dong

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 .

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 .

Accurate electrochemical parameterisation of lithium-ion batteries is essential for physics-based modelling, electrode design, and safety assessment, yet conventional approaches such as galvanostatic intermittent titration (GITT) for diffusion and electrochemical impedance spectroscopy (EIS) for reaction kinetics are typically performed separately and require several weeks to generate comprehensive temperature and state of charge (SOC) resolved datasets. Here, a hybrid symmetrical galvanostatic pulse-EIS (SGP-EIS) methodology is introduced that determines both reaction and diffusion kinetics within a single integrated workflow. A symmetric charge-discharge pulse sequence at each SoC point preserves the open-circuit voltage and minimises SoC drift, enabling the thermodynamically consistent extraction of reaction kinetics (charge-transfer resistance, exchange current density, electrode reaction rate) and diffusion kinetics (lithium diffusion coefficient) directly from transient voltage responses. Subsequent EIS measurements at the same SoC provide independent validation of the reaction kinetics via distribution of relaxation times (DRT) analysis. Applied to NMC622//Li and graphite//Li half-cells over 20~100 % SoC and 10~45 °C, the methodology yields parameter maps in strong agreement with conventional GITT and EIS, while reducing total characterisation time from several weeks to approximately four days. The resulting temperature, and SoC-dependent kinetic maps reveal high-resistance and diffusion-limited operating regimes associated with elevated polarisation, heat generation, and lithium plating risk, providing a practical and fast route to safety-informed cell design and physics-based model parameterisation applicable across electrode chemistries and formats for battery energy storage.

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.

Accurate electrochemical parameterisation of lithium-ion batteries is essential for physics-based modelling, electrode design, and safety assessment, yet conventional approaches such as galvanostatic intermittent titration (GITT) for diffusion and electrochemical impedance spectroscopy (EIS) for reaction kinetics are typically performed separately and require several weeks to generate comprehensive temperature and state of charge (SOC) resolved datasets. Here, a hybrid symmetrical galvanostatic pulse-EIS (SGP-EIS) methodology is introduced that determines both reaction and diffusion kinetics within a single integrated workflow. A symmetric charge-discharge pulse sequence at each SoC point preserves the open-circuit voltage and minimises SoC drift, enabling the thermodynamically consistent extraction of ohmic resistance, charge-transfer resistance, exchange current density, electrode reaction rate, and lithium diffusion coefficient directly from transient voltage responses. Subsequent EIS measurements at the same SoC provide independent validation of the reaction kinetics via distribution of relaxation times (DRT) analysis. Applied to NMC622//Li and graphite//Li half-cells over 20~100% SoC and 10~45 °C, the methodology yields parameter maps in strong agreement with conventional GITT and EIS, while reducing total characterisation time from several weeks to approximately four days. The resulting temperature, and SoC-dependent kinetic maps reveal high-resistance and diffusion-limited operating regimes associated with elevated polarisation, heat generation, and lithium plating risk, providing a practical route to safety-informed cell design and physics-based model parameterisation applicable across electrode chemistries and formats.

Lithium imide is an underexplored candidate for an all-solid-state battery electrolyte. Here it is shown to possess many desirable properties and unusual electrochemical behaviour, alongside its first operation in two lithium metal batteries.

All-solid-state batteries utilising a Li-metal anode have long promised to be the next-generation of high-performance energy storage device, with a step-change in energy density, cycling stability and cell safety touted as potential advantages compared to conventional Li-ion battery cells. A key to enabling this technology is the development of solid-state electrolytes with the elusive combination of high ionic conductivity, wide electrochemical stability and the ability to form a conductive and stable interface with Li metal. Presently, oxide and sulfide-based materials, particularly garnet and argyrodite-type structures, have proved most promising for this application. However, these still suffer from a number of challenges, including resistive lithium metal interfaces, poor lithium dendrite suppression (at high current density) and low voltage stability. Here we report the first application of lithium imide, an antifluorite-structured material, as a solid electrolyte in a Li-metal battery. Low-temperature synthesis of lithium imide produces promising Li-ion conductivity, reaching > 1 mS cm-1 at 30 ˚C using a modest post-synthetic mechanochemical treatment, as well as displaying at least 5 V stability vs Li+/Li. In situ electrochemical operation of lithium imide with Li-metal electrodes reveals a 1000-fold increase in its measured ionic conductivity, whilst appearing to remain an electronic insulator. It is postulated that stoichiometry variation at the grain boundary leads to a highly disordered quasi-liquid state, facilitating this conductivity improvement. Furthermore, the material is shown to possess impressive stability under high current density conditions (70 mA cm-2) as well as the ability to operate in Li-metal battery cells. These results not only highlight the promising performance of lithium imide, but also its potential to be the basis for a new family of antifluorite based solid electrolytes.

While garnet Li ion conductors are attracting considerable interest as potential solid state electrolytes for Li ion batteries, a key challenge is to improve the conductivity, which is associated with the Li content in the structure, and the density of the sintered electrolyte membranes. In this work we show that Zn can be doped on the 16a octahedral Nb site increasing the Li content, while also leading to substantially improved sintering in Li_5+xLa₃Nb_2−xZr_xO₁₂. As a result of the enhanced sintering, and the increase in Li content, the conductivities were significantly enhanced on Zn doping, up to 2.1 × 10⁻⁴ S cm⁻¹ at 25 °C for Li_6.6La₃ZrNb_0.8Zn_0.2O₁₂. Computational modelling supports favourable doping of Zn on the Nb site with 3 Li interstitials as per experimental findings. Furthermore, it suggests Li ion diffusion via a knock-on mechanism, but crucially the saturation of sites closest to the Zn means that migration barriers are similar for doped and pure systems, with the increased Li ion conductivity attributed to larger pre-factors due to increased number of Li ions in the doped material. A challenge with these Zn doped garnet is the reduction of Zn in contact with Li metal. Nevertheless, surface fluorination or employing the Zn doped garnet as a buffer layer with an alternative garnet electrolyte is shown to be effective to inhibit dendrite growth, and stable cycling exceeding 250 hours is demonstrated.

Polyanion modification represents an alternative low-cost strategy to improve the performance of lithium nickel oxide cathode materials.

In this paper, a high-entropy type lithium garnet is presented that rapidly sinters/densifies from the precursors, with favourable electrochemical properties in terms of both conductivity and limiting dendrite propagation.