High‐value recycling of photovoltaic silicon waste is an important path to achieve “carbon neutrality.” However, the current remelting and refining technology of Si waste (WSi) is tedious with high secondary energy consumption and repollution, and it can only achieve its relegation recycling. Here, an efficient and high‐value recycling strategy is proposed in which photovoltaic WSi is converted to high energy density and stable Si nanowires (SiNWs) electrodes for lithium‐ion batteries (LIBs) in milliseconds. The flash heating and quenching (≈2100 K, 10 ms) provided by an electrothermal shock drive directional diffusion of Si atoms to form SiNWs within the confined space between graphene oxide films. As a result, the SiNWs self‐assemble to form a conductive SiNWs–reduced graphene oxide composite (SiNWs@RGO). When applied as a binder‐free anode for LIBs the SiNWs@RGO electrode exhibits an ultrahigh initial Coulombic efficiency (89.5%) and robust cycle stability (2381.7 mAh g−1 at 1 A g−1 for more than 500 cycles) at high Si content of 76%. Moreover, full LIBs constructed using the commercial Li[Ni0.8Co0.16Al0.04]O2 cathode exhibit impressive cycling performance. In addition, this clean high‐value recycling method will promote economic, environmentally friendly, and sustainable development of renewable energy.

The development of efficient strategies to recycle lithium-ion battery (LIB) electrode materials is an important yet challenging goal for the sustainable management of battery waste. This work reports a facile and economically efficient method to convert spent cathode material, LiFePO 4 , into a high-performance NiFe oxy/hydroxide catalyst for the oxygen evolution reaction (OER). Herein, Ni-LiFePO 4 is synthesized via the wetness impregnation method and further evolves into defect-rich NiFe oxy/hydroxide nanosheets during the OER. The introduction of the Ni promoter together with in situ evolution strengthens the electronic interactions among the metal sites and creates an abundance of defects. Experimentally, the evolved Ni-LiFePO 4 delivers a low overpotential of 285 mV at 10 mA cm −2 and a small Tafel slope of 45 mV dec −1 , outperforming pristine LiFePO 4 and is even superior to the benchmark catalyst RuO 2 . Density functional theory (DFT) calculations reveal that the introduction of Ni effectively activates Fe sites by optimizing the free energy of the *OOH intermediate and that the abundance of oxygen defects facilitates the oxygen desorption step, synergistically enhancing the OER performance of LiFePO 4 . As a green and versatile method, this is a new opportunity for the scalable fabrication of excellent electrocatalysts based on spent cathode materials.

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