The recycling of spent lithium-ion batteries is an effective approach to alleviating environmental concerns and promoting resource conservation. LiFePO₄ batteries have been widely used in electric vehicles and energy storage stations. Currently, lithium loss, resulting in formation of Fe(III) phase, is mainly responsible for the capacity fade of LiFePO₄ cathode. Another factor is poor electrical conductivity that limits its rate capability. Here, we report the use of a multifunctional organic lithium salt (3,4-dihydroxybenzonitrile dilithium) to restore spent LiFePO₄ cathode by direct regeneration. The degraded LiFePO₄ particles are well coupled with the functional groups of the organic lithium salt, so that lithium fills vacancies and cyano groups create a reductive atmosphere to inhibit Fe(III) phase. At the same time, pyrolysis of the salt produces an amorphous conductive carbon layer that coats the LiFePO₄ particles, which improves Li-ion and electron transfer kinetics. The restored LiFePO₄ cathode shows good cycling stability and rate performance (a high capacity retention of 88% after 400 cycles at 5 C). This lithium salt can also be used to recover degraded transition metal oxide-based cathodes. A techno-economic analysis suggests that this strategy has higher environmental and economic benefits, compared with the traditional recycling methods.

Smart electronics and wearable devices require batteries with increased energy density, enhanced safety, and improved mechanical flexibility. However, current state‐of‐the‐art Li‐based rechargeable batteries (LBRBs) use highly reactive and flowable liquid electrolytes, severely limiting their ability to meet the above requirements. Therefore, solid polymer electrolytes (SPEs) are introduced to tackle the issues of liquid electrolytes. Nevertheless, due to their low Li⁺ conductivity and Li⁺ transference number (LITN) (around 10⁻⁵ S cm⁻¹ and 0.5, respectively), SPE‐based room temperature LBRBs are still in their early stages of development. This paper reviews the principles of Li⁺ conduction inside SPEs and the corresponding strategies to improve the Li⁺ conductivity and LITN of SPEs. Some representative applications of SPEs in high‐energy density, safe, and flexible LBRBs are then introduced and prospected.