Lithium-ion batteries (LIBs) have an important role in the shift required to achieve a global net-zero carbon target of 2050. Electrode manufacture is amongst the most expensive steps of the LIB manufacturing process and, despite its apparent maturity, optimised manufacturing conditions are arrived at by largely trial and error. Currently, LIB manufacturing plants are controlled to follow the fixed "recipe" obtained by trial and error, which may nonetheless be suboptimal. Moreover, regulating the process as a whole to conform to the set conditions is not widespread. Inspired by control approaches used in other film and sheet processes, we discuss opportunities for implementing real-time process control of electrode-related products, which has the potential to reduce the electrode manufacturing cost, CO2 emissions, usage of resources by increases in process yield, and throughput. We highlight the challenges and significant opportunities of implementing real-time process control in LIB electrode production lines.

Solid-state batteries can outperform lithium-ion batteries in energy per unit mass or volume when operating with a Li metal anode. However, Li anodes pose significant manufacturing challenges. Anode-free cells avoid these challenges by plating metallic Li at the anode on the first charge, but subsequent nonuniform cyclic stripping and plating decrease the Coulombic efficiency and encourage Li dendrites and early cell failure. We report a new spray-printed nanocomposite bilayer of silver/carbon black (Ag/CB) between anodic current collectors and a Li6PS5Cl solid electrolyte comprising an Ag-rich region at the current collector and a CB-rich region at the solid electrolyte. Compared with previous Ag/CB mixtures, this bilayer promoted more uniform Li anode plating and improved cycling. Cells with a high-Ni oxide cathode had an initial discharge capacity of >190 mAh/g and a Coulombic efficiency of >98% over 100 cycles. Improved Li plating uniformity with the structured Ag/CB interlayer was confirmed by using secondary-ion mass spectrometry (SIMS) imaging.

The fraction of polytetrafluoroethylene (PTFE) binder in solvent-free Li-ion battery electrodes is shown to have a dramatic impact on their processability, microstructural evolution and elec- trochemical performance. We show experimentally that increasing binder fraction from 0.5 to 4 wt.% transformed the electrode microstructure from an efficient, open structure containing PTFE nano-fibrils to a cemented morphology with blocked porosity. The solvent-free electrodes showed a classical visco-elastic response during compression, comprising three distinct regions of deformation. The electrode stiffness and yield/flow strength increased non-linearly with binder fraction such that for higher binder contents (>2wt.%), there was extensive LiNi0.6Co0.2Mn0.2O2 (NMC) particle fracture during the calendering process, with cracks propagating along the grains of polycrystalline NMC particles. Conversely at lower binder fraction (<2wt.%), the PTFE readily fibrillated into highly textured (100) crystalline nano-fibrils and NMC particles remained largely intact. These electrodes showed superior electrochemical performance due to higher ionic mobility through the open nano-fibrillar microstructure and intact NMC particles.

Spatial distributions in current, temperature, state-of-charge and degradation across the plane of large format lithium-ion battery pouch cells can significantly impact their performance, especially at high C-rates. In this paper, a method to smooth out these spatial distributions by grading the electrode microstructure in-the-plane is proposed. A mathematical model of a large format pouch cell is developed and validated against both temperature and voltage experimental data. An analytical solution for the optimal graded electrode that achieves a uniform current distribution across the pouch cell is then derived. The model predicts that the graded electrodes could significantly reduce the likelihood of lithium plating in large format pouch cells, with grading increasing the C-rate at which plating occurs from 2.4C to 4.3C. These results indicate the potential of designing spatially varying electrode architectures to homogenise the response of large format pouch cells and improve their high rate performance.

Many battery applications target fast charging to achieve an 80 % rise in state of charge (SOC) in < 15 min. However, in the case of all-solid-state batteries (SSBs), they typically take several hours to reach 80 % SOC while retaining a high specific energy of 400 W h kg(cell)(-1). We specify design strategies for fast-charging SSB cathodes with long cycle life and investigate the fast-charging capability of a sulfide-based single crystal Li-Ni-Mn-Co oxide composite cathode. At 30 degrees C and charging at 15 mA cm(-2), a specific capacity of 150 mA h g(-1) was achieved in similar to 8 min, with 81 % capacity retention after 3000 cycles. Critically, a 3-electrode arrangement was used to avoid the common problem of overcharging at high current densities. By following the design strategy and optimized manufacturing, a 210 mu m thick cathode was able to be charged at an extraordinary current density of 50 mA cm(-2) to reach an areal capacity of 8 mA h cm(-2) in only 10 min, suggesting practical cathodes for SSBs with 400 W h kg(cell)(-1) may be within reach.

The Selective Metallization Technique shows promise for roll-to-roll in-line patterning of flexible electronics using evaporated metals, but challenges arise when applied to sputtering functional materials. This study overcomes these challenges with simultaneous sputtering of Bi-Sb-Te and evaporation of metal (Ag or Cu) for thermoelectric layers when using Selective Metallization Technique. Large-scale manufacturing is demonstrated through roll-to-roll processing of a 0.8 m wide polymer web at 25 m/min, achieving high-throughput production of functional thin-film patterns with nanometer thickness. The room-temperature-deposited material system exhibits significantly enhanced thermoelectric performance and facilitates an n-type-to-p-type transition in the Cu- or Ag-containing Bi-Sb-Te-based composite film. Here, we show that while applying Selective Metallization Technique, the evaporation of metal modifies the impact of residual oil on Bi-Sb-Te, which can be effectively removed with a few seconds of plasma exposure, and the fabricated thermoelectric devices are validated in wearable applications utilizing a coiled-up wristband design.

Li-rich disordered rocksalts are promising next-generation cathode materials for Li-ion batteries. Recent reports have shown it is also possible to obtain Na-rich disordered rocksalts, however, it is currently poorly understood how the knowledge of the structural and redox chemistry translates from the Li-rich to the Na-rich analogs. Here, the properties of Li2MnO2F and Na2MnO2F are compared, which have different ion sizes (Li+ = 0.76 vs Na+ = 1.02 Å) but the same disordered rocksalt structure and stoichiometry. It is found that Na2MnO2F exhibits lower voltage Mn- and O-redox couples, opening access to a wider compositional range within the same voltage limits. Furthermore, the intercalation mechanism switches from predominantly single-phase solid solution behavior in Li2MnO2F to a two-phase transition in Na2MnO2F, accompanied by a greater decrease in the average Mn─O/F bond length. Li2MnO2F retains its long-range disordered rocksalt structure throughout the first cycle. In contrast, Na2MnO2F becomes completely amorphous during charge and develops a local structure characteristic of a post-spinel. This amorphization is partially reversible on discharge. The results show how the ion intercalation behavior of disordered rocksalts differs dramatically when changing from Li- to Na-ions and offers routes to control the electrochemical properties of these high-energy-density cathodes.

Solid-state electrolytes have enabled the design of bipolar all-solid-state lithium batteries (BPSSBs) as a promising energy storage technology, offering a simplified architecture, high voltage, and low manufacturing costs compared to conventional liquid electrolyte lithium-ion batteries and solid-state batteries (SSBs). The bipolar architecture, characterized by the direct electrical connection of multiple electrochemical cells in series without external wiring, increases energy density and reduces internal resistance. Despite their advantages, several challenges remain in the development of advanced BPSSBs. These challenges include internal short circuits due to misalignment of cells, corrosion of bipolar layers or current collectors, and manufacturing complexities that affect the scalability of production processes. Additionally, the volume expansion of electrodes and solid electrolytes during charge and discharge induces mechanical stress, which can lead to cracks and eventual failure under repeated cycling. To the best of our knowledge, there are no specific reports on the introduction of soft and flexible interlayers for LPSC-based BPSSBs, even though such interlayers have been used in conventional SSBs. Among various solid electrolytes, the argyrodite-type Li₆PS₅Cl (LPSC) solid electrolyte (SE) stands out due to its low-temperature processing capability, remarkable ionic conductivities exceeding 10⁻³ S/cm at room temperature, and ability to minimize interface resistance, thereby improving overall battery performance. However, the electrochemical properties and failure mechanisms of LPSC-based pouch type BPSSBs have been rarely investigated. This study explores the electrochemical performance, mechanisms, and challenges associated with integrating LPSC solid electrolytes and flexible interlayers into pouch type BPSSB configurations. Advanced characterization methods, such as X-ray computed tomography (XCT), were utilized to investigate interfacial dynamics and degradation mechanisms. The results indicate that proper cell alignment and assembly, combined with optimized interface design, significantly improve the electrochemical performance of pouch type BPSSBs. The integration of LPSC solid electrolytes into bipolar configurations also paves the way for the development of next-generation solid-state batteries with high energy and power densities, making them suitable for electric vehicle applications. Figure 1

Lithium-ion batteries (LIB) are synonymous with the modern age of electrification, yet advances in battery design, manufacturing, and chemistry are still urgently needed. Mathematical modelling plays an important role in understanding LIB performance and can provide physics informed design directions, optimisation and explain outcomes. We present an exploration and detailed comparison of the commonly used homogenised Doyle-Fuller Newman (DFN) model and the high fidelity X-ray computed tomography (CT) based microstructural model for LIBs. We provide insights into the relative benefits of each model and highlight why they are important to battery technology development. Alongside experiments, we use the models to explore and compare two common cathode chemistries, lithium nickel manganese cobalt oxide, Li[Ni 0.6 Co 0.2 Mn 0.2 ]O 2 (NMC622), and lithium iron phosphate, LiFePO 4 (LFP), and investigate the influence of electrode thickness and discharge current density. The DFN and CT image-based models show good alignment for averaged LIB metrics, such as the voltage response and active material utilisation, demonstrating that homogenised, computationally inexpensive models are an essential basis for battery design and optimisation. The CT-based microstructural model provides further insight into localised particle and electrode dynamics, taking into account heterogeneities that are a source of battery degradation. Qualitatively, the models also compare well with experimental secondary ion mass spectrometry (SIMS) mapping of the Li concentration in the active particles across the electrode thickness.

Avoiding lithium dendrites at the lithium/ceramic electrolyte interface and as a result avoiding cell short-circuit when plating at practical current densities remains a significant challenge for all-solid-state batteries. Typically, values are limited to around 1 mA cm-2, even, for example, for garnets with a relative density of >99%. It is not obvious that simply densifying ceramic electrolytes will deliver high plating currents. Here we show that plating currents of 9 mA cm-2 can be achieved without dendrite formation, by densifying Argyrodite, Li6PS5Cl, to 99%. Changes in the microstructure of Li6PS5Cl on densification from 83 to 99% were determined by FIB-SEM tomography and used to calculate their effect on the critical current density (CCD). Not all changes in microstructure with densification act to increase CCD. While smaller pores and shorter cracks increase CCD, lower pore population and narrower cracks act to decrease CCD. Calculations show that the former changes dominate over the latter, predicating an overall increase in CCD, as observed experimentally.

Bilayer cathodes comprising two active materials are explored for their ability to improve lithium-ion battery charging performance. Electrodes are manufactured with various arrangements of lithium nickel manganese cobalt oxide Li[Ni0.6Co0.2Mn0.2]O2 (NMC622) and lithium iron phosphate LiFePO4 (LFP) active particles, including in two different discrete sub-layers. We present experimental data on the sensitivity of the electrode C rate performance to the electrode design. To understand the complex bilayer electrode performance, and to identify an optimal design for fast charging, we develop an extension to the Doyle-Fuller-Newman (DFN) model of electrode dynamics that accommodates different active materials in any number of sub-layers, termed the multilayer DFN (M-DFN) model. The M-DFN model is validated against experimental data and then used to explain the performance differences between the electrode arrangements. We show how the different open circuit potential functions of NMC and LFP can be exploited synergistically through electrode design. Manipulating the Li electrolyte concentration increases achievable capacity. Finally the M-DFN model is used to further optimise the best performing bilayer electrode arrangement by adjusting the ratio of the LFP and NMC sub-layer thickness.

Hot tears can arise during the late part of alloy solidification because of the shrinkage of isolated liquid as it turns to solid and may have a catastrophic effect on cast tensile properties. Although there are correlations to suggest alloy hot tear sensitivity to casting conditions, they do not capture the influence of microstructure on tearing, such as second-phase particles or intermetallic compounds (IMCs) commonly present in engineering alloys. We use in situ X-ray radiography to quantify the formation and growth behaviour of hot tears in Al-5Cu and Al-5Cu-1Fe alloys during solidification. An automated hot tear detection, tracking and merging algorithm is developed and applied to reveal the role of Fe-rich IMC particles, typical of recycled alloys, on hot tear behaviour. These defects are termed hot tears here on the basis of their complex, extended inter-connected morphology, distinct from more rounded shrinkage porosity. We also visualise and quantify the velocity of interdendritic flow driven by solidification shrinkage, and estimate the pressure changes due to shrinkage. Hot tearing starts at lower solid fraction when IMCs are present due to reduced interdendritic flow, and hot tear formation is more spatially homogeneous, less clustered and more numerous. We show that the largest, most damaging hot tears form from many merging events, that is enhanced by the presence of IMCs.

Modern batteries are highly complex devices. The cells contain many components—which in turn all have many variations, both in terms of chemistry and physical properties. A few examples: the active materials making the electrodes are coated on current collectors using solvents, binders and additives; the multicomponent electrolyte, contains salts, solvents, and additives; the electrolyte can also be a solid ceramic, polymer or a glass material; batteries also contain a separator, which can be made of glass fibres, polymeric, ceramic, composite, etc. Moving up in scale all these components are assembled in cells of different formats and geometries, coin cells and Swagelok cells for funamental testing and understanding, and pouch, prismatic and cylindrical cells for application. Given this complexity dictated by so many components and variations, there is no wonder that addressing the crucial issue of true sustainability is an extremely challenging task. How can we make sure that each component is sustainable? How can the performance can be delivered using more sustainable battery components? What actions do we need to take to address battery sustainability properly? How do we actually qualify and quantify the sustainability in the best way possible? And perhaps most importantly; how can we all work—academia and battery industry together—to enable the latter to manufacture more sustainable batteries for a truly cleaner future? This Roadmap assembles views from experts from academia, industry, research institutes, and other organisations on how we could and should achieve a more sustainable battery future. The palette has many colours: it discusses the very definition of a sustainable battery, the need for diversification beyond lithium-ion batteries (LIBs), the importance of sustainability assessments, the threat of scarcity of raw materials and the possible impact on future manufacturing of LIBs, the possibility of more sustainable cells by electrode and electrolyte chemistries as well as manufacturing, the important role of new battery chemistries, the crucial role of AI and automation in the discovery of the truly sustainable batteries of the future and the importance of developimg a circular battery economy.

Additive manufacturing (AM) is increasingly being used to fabricate end-use and high-value-added parts in a range of industries. AM’s ability to create complex geometries and vary the internal composition of a part has enabled the design of many novel devices, including radio frequency (RF) devices that rely on the spatial variation of electromagnetic (EM) properties. However, current AM processes for fabricating complex parts are typically run without any part monitoring or online feedback control, and as a result, the printed parts may be compromised by defects or have poor tolerances. Manufacturing parts in this way also requires extra quality testing since there is no knowledge of their interior quality. For these reasons, introducing process monitoring and corrective action to the AM process has become an important area of research as AM is being used to create safety-critical parts. This work proposes a control algorithm to enable closed-loop control of an EM property, specifically dielectric permittivity, within a print using a fused filament fabrication (FFF) printer. The control system used a split-ring resonator (SRR) to measure the permittivity of printed thermoplastic, and the control action was applied by updating the printed infill density layer to layer. This control system was tested by printing a proof-of-concept graded-index (GRIN) lens with spatially varying permittivity through the lens’ length. The results demonstrate the ability of the controller to follow a constantly varying reference signal, indicating the potential of closed-loop control for improved fabrication of functional RF devices that depend on precise variations in relative permittivity.

The two deformation modes of meta-biomaterials during cyclic loading have been revealed: stochastic and deterministic strut failure processes. Biomimetic Voronoi structures with a range of strut thicknesses and number of cells per unit volume are printed. We show that when the strut thickness is 200 μm or above, the fatigue fracture process of the lattice is deterministic and the fatigue scatters are below 15%. As the strut is thinned to 150 μm, the local failures occur randomly within the structure, which may lead to a high fatigue scatter (>30%). The two distinct behaviours result from the processing limit of the laser powder bed fusion technique. We demonstrate that the fatigue scatter and the location of the failure process within the lattice are related to the probability that a cluster of unconnected struts larger than a critical value can exist within the lattice. Unlike solid parts, porosity hardly triggers any damage in metallic lattices during cyclic deformation. The discovery of the Janus-like failure process opens up our understanding of meta-biomaterials and defines the pathway towards the design of mechanically durable intricate implants.

A sample size effect which influences the fatigue behaviour of laser powder bed fusion Ti-6Al-4V is identified and quantified. Two cylindrical samples are considered: ∅ 1.3 mm and ∅ 2.0 mm. The larger specimen demonstrates better fatigue resistance particularly in the high-cycle regime, with the differing surface roughness contributing to this effect. It is also confirmed that processing-induced porosity can compromise the fatigue performance even when the initiation sites are surface defects. The larger contribution of porosity to the fatigue fracture process of the larger specimen results in a higher scatter in the fatigue life. Differences in microstructure do not seem to contribute strongly to the variation in fatigue properties of the two specimens, but we present some evidence that the coarser microstructure of the larger specimen promotes a stronger tolerance to defects and induces more tortuous crack paths which hinders fatigue crack growth.

The orientation dependency of the fatigue behaviour of laser powder bed fusion Ti-6Al-4V has been analyzed and rationalized. Seven build orientations relative to the build plate have been studied. The 75° specimen demonstrates the highest fatigue life owing to the optimal surface quality and low proportions of grains near-parallel to the loading direction. When the build orientation is 30° or below, only defects on the downward-facing surface serve as the fatigue crack initiation sites as a result of the poor surface quality. Beyond 45°, cracks begin to initiate from the otherward-facing surface owing to the reduced variation in Ra across the sample surface. The large variation in the size and number of pore clusters near the initiation site governs the highest fatigue scatter of the 75° specimen whereas the difference in crack initiation sites of the 45° specimen results in the large difference in fatigue life. Our results demonstrate that the orientation effect is a critical factor to consider for the design of fatigue-tolerant intricate components.

Using a Li metal anode, the all-solid-state battery (ASSB) promises a step change in specific energy over Li-ion batteries and the potential for increased battery safety. ASSBs rely critically on the efficient movement of Li charge carriers through a Li-conducting solid electrolyte (SE) separator and throughout a composite cathode (CC) comprising active particles, particulate SE, polymeric binder, and carbon. Unfortunately, there is no readily accessible laboratory method to visualise Li distributions at both particle and electrode scales to help understand and optimise Li electrode dynamics in ASSBs. We report a method to map all electrode elements in a 3D volume, including Li, within a typical ASSB composite cathode. The method combines a xenon plasma focused-ion beam (PFIB) for 3D milling, energy dispersive X-ray spectroscopy (EDS) to map non-Li elements, and secondary ion mass spectrometry (SIMS) to map Li. We manipulate 3D EDS and SIMS datasets into a common format and then recombine them in 3D to differentiate the different materials at high resolution. This new approach can be applied to understand and optimise the role of microstructure in controlling ASSB performance.

Lithium-ion batteries (LIBs) are playing an increasingly important role in enabling the transition to a low-carbon global economy, in electric vehicle and grid storage applications. Despite increasing LIB ubiquity, there remains gaps in our understanding of how to optimize further LIB electrode design and structure, and how to achieve such designs in practice and at scale without excessive trial-and-error experimentation. For example, thicker electrodes are desirable for improved volumetric capacity but particularly during rapid charging and discharging cycles, a significant through-electrode thickness Li ion concentration gradient in the electrolyte builds up. This leads to a spatially varying concentration overpotential that in turns leads to uneven utilization of the active material, resulting in diminished capacity and accelerated degradation. Although models of electrode dynamics can help qualitatively to understand concentration polarization effects as a function of electrode design, there are few practical experimental tools to visualize or resolve Li-ion concentration gradients in practice. For example, the widely-used energy dispersive X-ray spectroscopy (EDS) in a scanning electron microscopy cannot resolve elements with very low atomic number such as Li. In this presentation we describe the development of a methodology to visualize Li-ion concentration gradients across a range of electrodes based on secondary ion mass spectroscopy (SIMS). We combine SIMS with EDS to collect elemental maps of all principle LIB electrode elements in a single workflow, which is also extended to 3D by further combining with a plasma field ion microscope (P-FIB) capability. We apply the new methodology for LIB cathodes based on LiFePO4 (LFP) and LiMn2O4 (LMO) that are at different state of overall charge, achieved at a range charging rates. The electrodes also span a range of thicknesses from 100 to 700 µm. We show how the approach can operate over cross-sections large enough to encompass all the electrode thickness while maintaining sufficient spatial resolution to capture key features of the local Li concentration. While EDS elemental maps, with appropriate calibration, can be correlated to local element concentration with good accuracy, SIMS spectra and specifically the intensity of the 7Li+ peaks cannot be readily related to local Li concentration since the yield of 7Li+ ion relates to additional factors, such as the local atomic environment, surface topology and more. We describe how we inter-relate the EDS and SIMS maps for non-Li elements to account for some of these features, and show how these reveals the underlying Li distributions. We consider how these measurements of the Li concentration in the solid particles of the electrode relate to the local state of charge, and the conditions in the electrolyte when charge/discharge was halted and the sample was retrieved from the cell for examination. Fine-scale variations in local 7Li+ ion intensity are also revealed and explained in terms of local microstructural features such as particle size, any particle cracking, the growth of secondary electrolyte interphase, etc.

In recent years, solid-state battery (SSB) performance has steadily improved with the use of sulfide solid electrolytes (SEs). However, most research has focused on small (diameter <10 mm), thick (separator >500 μm) pellet-type cells that use non-scalable manufacturing routes and yield a low cell energy density. Technical applications require thinner and larger sheet-type cells made by scalable techniques. We examine the applicability of a scalable layer-by-layer spray printing approach for manufacturing sheet-type SSB components. Sprayed sulfide SE separators with thickness as thin as 10 μm and high ionic conductivity of 1 mS cm−1 are fabricated, along with a sprayed composite cathode that delivered a capacity retention of 63% after 800 cycles. Finally, the flexibility of spray printing for process integration is demonstrated by the fabrication of an anode-free cell consisting of a sprayed Ag-C layer and a sprayed SE layer.