Spin Charge of Co Nanoparticles Loaded on the Carbon Substrate Enabling Rate‐Capable Lithium Storage at High Mass‐Loadings

Abstract Developing high mass‐loading electrodes is crucial for enhancing the energy density of current batteries, yet challenges such as poor rate performance and cycling instability must be addressed. Spin charge storage on transition metal nanoparticle surfaces, characterized by rapid charging and the absence of phase transitions, offers an ideal storage behavior for high mass‐loading electrodes. In this study, electrospinning is utilized to fabricate free‐standing carbon nanofibers incorporating Co nanoparticles for high‐mass loading and high‐performance anodes. The resulting anode, with a maximum mass loading of 6.8 mg cm⁻², exhibits remarkable cycle stability and high‐rate performance of 2 A g⁻¹ at a capacity over 3 mAh cm⁻², superior than reported results. Magnetometry and electron paramagnetic resonance spectroscopy are employed to monitor the charge storage mechanism of the Co@CNFs, involving both the reversible formation of a spin capacitance and the growth of radical anions in the solid electrolyte interface. Additionally, in situ X‐ray diffraction and optical microscopy provide direct evidence of the absence of mechanical stress‐induced phenomena within the spin charge process, attributed to high‐rate capable lithium storage under high mass loading. The strategic approach presented herein offers a reliable methodology for engineering high‐energy‐density lithium‐ion batteries.