Research data supporting "Parameterization and modelling protocols for ultra-fast charging Wadsley-Roth lithium-ion batteries from coin to pouch cells"

First zip folder contains raw battery cell data in .txt format, embodying a full study of the electrochemistry of the Wadsley-Roth structure (with Nb2O5 as its simplest composition) in different cell formats. The filename refers to the type of cell and type of test.$$\$$ Full low-rate electrochemical parameterization data is collected in half cells versus lithium with EIS combined with Galvanostatic Intermittent Titration Technique (GITT), reference cycles (ref), discharge rate tests (dischargerate) and voltage sweeps (VS). Full high-rate electrochemical parameterization data is acquired in 3-electrode cells versus NCA (LiNi0.8Co0.15Al0.05O2) with lithium as reference electrode with alternating pulses with increasing current (sGITT) after formation (form).$$\$$ Based on this, pulse (sGITT) and rate performance (chargerate and dischargerate) is modelled (model) in full coin cells (fullcell) and pouch cells (pouchcell) versus NCA. Validation (validation) is carried out with rate (chargerate and dischargerate) experiments in full coin cells and pouch cells from 0.1C to 20C. $$\$$ All files have time, current, voltage and capacity data and are linked to the cell parameters including electrode areal mass loading, porosity and thickness as reported in the associated publication. The publication also contains more information regarding the parameterization and modelling method used to acquire the data. $$\$$ Second zip folder contains the cell testing program settings that were used to generate this data in .txt format. This format can also be openened with Biologic BT-lab or EC-lab cell cyling software directly. The first half of the filename refers to the type of test (linking to the data above). The second half contains extra information on specific settings. "A" and "T" mean test for anode half cell and three electrode cell respectively. "C" and "D" indicate if the test is testing (fast) charge or discharge capability respectively. "P" indicates if a predelithiation step is added before the rest of the test is started. "R" indicates that the data is collected at high resolution. "E" indicates whether the test is combined with PEIS tests. "####V" indicates the voltage window. '##C' indicates the maximum C-rate used in the test.The work was carried out as part of research activities conducted and funded by Echion Technologies Ltd

The thermodynamics, kinetics and modelling of fast-charging lithium-ion batteries featuring crystallographic shear niobium metal oxide anodes

The world increasingly depends on batteries to store renewable energy and use that same energy in our vehicles and portable communication devices. This puts exceeding pressure on global resources. We need batteries that charge faster and live longer, such that we can use less resources. Faster charge and longer life are currently limited by the negative electrode, typically graphite, because fast charging would push the potential into the regime of hazardous and cycle-life degrading lithium plating. The ideal potential for fast charge would be low, but just above the around 1 V reduction potential of the electrolyte. Niobium-based metal oxides have the optimal electronegativity to strike this balance, with a nominal potential around 1.6 V, charging rates >5C and a cycle-life projected over 10,000 cycles. Chapter 1 shows that the exact potential can be tuned further by changing the average oxidation state through substitution of Nb5+ with for example W6+ or Ti4+. The range of average oxidation states then directly spans a material phase space classed by anion-to-cation ratios of 2.33 ≤ *y* 3-type blocks of corner-sharing octahedra that have ample window sites to rapidly intercalate many lithium-ions, interspaced with *y*=2.5 crystallographic shear planes of edge-sharing octahedra that add stability and electronic conductivity to the structure, and anchored at their corner by *y*=2 regions of tetrahedra or edge-sharing octahedra. The influence of this structure on cell performance is relatively unknown. Numerous publications exist on individual members of this Wadsley-Roth (WR) material family, but gaps in theory and varying experimental conditions make it impossible to compare. The aim of this thesis is to provide a fair and fundamental comparison across this material class, relating compositional and structural properties to cell thermodynamics and kinetics that can then be used to optimise the material selection and model any full-scale cell geometry. In total 16 different compounds were synthesised with comparable geometrical parameters. Subsequently, they were fully parameterised with various electrochemical tests. Current theory is still too firmly based on traditional metal plate electrodes. Because the WR materials allow extreme conditions of high currents and could be tuned over an extensive structural and compositional range, their study forms an excellent opportunity to modernise the fundamental understanding of the thermodynamics and kinetics of intercalation lithium-ion batteries, in general, and in relation to structural and compositional parameters. Chapter 2, on thermodynamics and energy density, introduces fundamental principles of configurational entropy to explain the steep bends at the cell potential ends and the detailed peaks in the cyclovoltammogram. Density function theory (DFT) exposed a site filling order and structural straightening. Via molecular orbital theory this was then related to enthalpic effects of relatively steeper potential regions due to progressively poorer charge-compensation and relatively poor shielding, but also relatively flatter potential regions related to metal-to-metal repulsion and pseudo Jahn-Teller effects at the block edge. Owing to their increased edge-sharing, low *y* materials could thus reach lower potentials without reaching the voltage cut-off earlier. Low *y* materials thus exhibit high energy density, particularly considering that they also consist of more lightweight elements. The structural straightening upon reduction was identified as the crucial mechanism that provides a competitive energy density to the WR material. The first cycle data and DFT also revealed the mechanism that tetrahedral linkages are irreversibly trapping lithium and that they can be left out of the structure to achieve nearly 100% first cycle efficiencies. On the other hand, the study in Chapter 3 of their intercalation kinetics through temperature-dependent GITT and PEIS with novel application of the compensation effect shows that lower *y* is at the cost of lower entropy of the diffusion pathways, such that their intercalation diffusion coefficients are lower. In general, the compensation effect and the effect of entropy can not be underestimated, while the effect of activation enthalpy could be misleading. Various PEIS, cyclovoltammetry, PITT and GITT techniques had to be critically reviewed and stripped from metal-plate concepts, to identify the formation of film layers and the trends in diffusion. The charge transfer reaction rate and lithium intercalation diffusion were identified as the main contributors to loss, limiting the charge/discharge rate. However, this study observed that the chemical lithium intercalation diffusion coefficient increases with rate. This surprising effect is no longer adequately described by the conventional mass-transfer theory and suggests effects of non-equilibrium driving forces, excited lithium hopping, lattice vibrations and energy barrier softening. Such a mechanism is essential to explain the high rate performance of WR materials and intercalation materials in general and provides an important direction for future theory and experimental research. All in all, this study showed a tradeoff between energy and rate, with TiNb2O7, Zn2Nb34O87 and PNb9O25 as winners. Independent of the tradeoff, performance could be further improved in the future with the substitution of lightweight cations, and by increasing the crystallographic entropy with multiple cations. In general, this work identified several new applications of theory to the modern battery cell, which will hopefully become more widely applied and further underpinned by in-situ direct observation methods on the particle level. All the theory and full parameterisation methods above were combined into a full cell continuum model in Chapter 4, that not only validates these approaches but also allows the design, verification and prediction of any commercial format multilayer cell geometry. This paves the way for this new class of ultra fast-charge long-life batteries that can power more of the world, with fewer batteries.Echion Technologies Ltd

Optimization of Electrode and Cell Design for Ultrafast-Charging Lithium-Ion Batteries Based on Molybdenum Niobium Oxide Anodes

[Image: see text] Niobium oxides are an emerging class of anode materials for use in high-power lithium-ion batteries. Galvanostatic cycling and electrochemical impedance spectroscopy (EIS) were used in this study to investigate the influence of electrode porosity, electrode mass ratio, and cycling rate on the capacity, cycle life, and ionic conductivity of Li-ion battery cells based on a modified micron-sized MoNb(12)O(33) (MNO) anode powder. Both electrode and cell designs were found to have a significant impact on the rate performance and cycle life of Li-ion half- and full cells. A higher specific capacity, improved rate performance, and a longer cycle life were obtained in both anode and cathode half-cells by lowering the electrode porosity through calendaring. MNO/Li half-coin cells displayed excellent cyclability, reaching 80% state of health (SOH) after 600 cycles at C/2 charge and 1C discharge. MNO/NMC622 full-coin cells displayed a high capacity of 179 mAh g(–1) at 100 mA g(–1) (0.5 mA cm(–2)) and excellent cyclability at 25 °C, reaching 70% SOH after over 1000 cycles at 1 mA cm(–2) after optimizing their N/P ratio. Excellent cyclability was obtained at both 1C/1C and fast 2C/2C cycling, reaching 80% SOH after 700 and 470 cycles, respectively. Full-coin and small pouch cells had outstanding rate performance as they could be charged from 0 to 84% capacity in less than 5 min at 10 mA cm(–2) and to 70% SOC in 120 s at 20 mA cm(–2)