Lithium-ion batteries (LIBs) are today considered as one of the best solutions towards an energy model based on renewable sources and zero-emission electric vehicles. However, the increased production of LIBs raises concerns regarding cost and availability of key materials such as lithium, cobalt or graphite. Indeed, after almost 20 years of cost decrease, the price of lithium-ion batteries is slowing down [1]. This is related to the fact that a lot of raw materials and metals (mainly copper, aluminum and cobalt) that are used in LiBs have increased relentlessly their prices because of its continuous demand. In this sense, are needed better performing, more price competitive and sustainable battery storage solutions beyond lithium that take into consideration the overall value chain, from access to raw material, innovative advanced materials, production, recycling and second life.

In this context, disposal and recycling are essential for the sustainability of this market and new recycling processes for LIBs are needed. Today there are processes that can recover high-value raw materials from LIBs (mainly copper, aluminum, and cobalt) but direct recycling of materials such as LiFePO₄ (LFP) that has less economic value and are environmentally much more sustainable represents an economic challenge for the battery market and future research.

NaFePO₄ (NFP) has been indeed proposed as one of the cheapest and most sustainable sodium-ion (Na-ion) cathode materials, [2-3] but it is not a thermodynamically stable phase and it is necessary to obtain it from LFP through redox reactions usually using expensive, toxic and hazardous reagents, cutting down its commercialization.[3-5] LFP recovering from spent LIBs can contribute to reducing the manufacturing costs of the NFP and increase the interest to recycle Li-ion batteries based on LFP cathodes.

In the perspective of a circular economy market, we propose in this work to explore the recovery of aged LFP electrodes and their reuse in new Na-ion batteries.