High-performance batteries had disruptive impact in the electronics sector, are pivotal in electrifying transport, and will play a crucial role in grid-scale storage solutions. In particular, Li-Ion and Na-Ion batteries are set to facilitate greater and more efficient use of renewable energy. Application demand for highest possible energy density and power, however, necessitates volatile chemistries and careful consideration of safety aspects as a number of high-profile battery accidents have made strikingly clear in recent years. The most catastrophic failure of Li-ion battery systems is a cascading thermal runaway. Thermal runaway can occur due to thermal, electrical, or mechanical abuse. It can result in the venting of toxic and highly flammable gases and the release of significant heat, potentially leading to explosions and severe damage to the battery, surrounding equipment and/or people. This project will provide materials technologies to physically safeguard Li-Ion and Na-Ion batteries against thermal runaway and thermally accelerated degradation, superseding existing external safety measures. Rather than changing the active material on the positive side, we will replace conductivity additives, an otherwise passive component of the electrodes, with smart materials. Electrical resistivity of the smart additives will increase by orders of magnitude at or above temperatures where it would otherwise be unsafe to operate the battery. As a consequence, uncontrolled electrochemical reactions, the initial heat source in a thermal runaway event, will cease, making electrochemically initiated thermal runaway impossible. The approach has several advantages: (1) it provides a drop-in solution, applicable to all active material chemistries in Li-Ion and Na-Ion batteries; (2) it is transferable to other battery technologies (e.g, Al-Ion); (3) it safeguards against a full range of abuse scenarios triggering thermal runaway; and (4) the protection mechanisms will be reversible with lifetime benefits of batteries under real-world situations. Smart additives will be developed utilising rational materials design driven by close integration between simulations at the atomistic and micro-scale with a comprehensive synthesis and characterisation program including a full array of in operando advanced electrochemical/spectroscopic techniques and x-ray tomography, complemented by state-of-the-art ex situ materials characterisation. Relevant abuse protocols will be developed and utilised to test batteries comprising electrodes with the smart additives at the cell and pack level. Further, we will exploit secondary characteristics of the smart additives to realise and demonstrate high-fidelity, non-invasive diagnostics and battery management to add an active safety layer for superior longevity. Alignment with ISCF objectives: Bringing together a complete value chain including SMIs (REAPsystems, Denchi), tier 1+2 suppliers (Johnson Matthey, Faradion, Yuasa), and larger OEMs (QinetiQ, Lloyd's, Dstl) with leading academics from engineering and chemistry (objectives 3+4), this project will innovate to deliver safer battery technologies and associated IP for automotive and other applications, increasing the UKs attractiveness for inward investment (objective 5) from global automotive OEMs and suppliers. Leveraged with over £150k support from industry, the program will increase the UKs R&D capacity/capability in battery research and deliver a world-leading, multi-disciplinary research program (objective 1) that is perfectly aligned with the 'Faraday Challenge' objectives, a UK flagship investment to develop and manufacture batteries for the electrification of vehicles (objective 2).