Lithium-ion technology is an increasing choice for battery powered systems, offering long-lasting, reliable and efficient energy storage. However, significant safety and performance challenges within the technology are still apparent. The current state of the art for monitoring cells performance is typically based on observing full cell voltage and occasional temperature sensor on the skin of a cell. Consequently, it is extremely difficult to track cells’ health and predict safety events within complex, especially high-performance, battery systems. Here we show the design and manufacturing methods of transforming normal cells into smart systems. Embedding reference electrodes, fibre optics and temperature sensors. This enables in-situ and operando data collection during cells’ real-life operations. The sensing methodologies and modification techniques developed in this work can be applied to all range of cells from small bespoke systems that are used within mobiles phones up to large scale battery modules and packs for electric vehicles and off-grid storage. We further demonstrate that our solution is compatible with long term operation and can be used to enhance the performance and safety of cells.