The coupled effects of the contact wire (CW) working surface profile and ambient humidity on the contact strip (CS) wear were investigated using a high-speed current-carrying friction and wear test rig. The experimental results revealed that the CW’s working surface profile determined the CS wear law of different friction pairs under high ambient humidity. Under low ambient humidity, when the current was less than or equal to 200 A, the ambient humidity determined the CS wear law; after the current exceeded 200 A, the change in the CW working surface profile became the decisive factor. Interestingly, when the current surpassed 300 A, the CW working surface profile significantly influenced the CS wear law.

In this study, spent LiFePO₄ (LFP) cathode materials were recycled and transformed into amorphous FePO₄ (a-FePO₄) via a leaching–precipitation method for further use as a high-performance cathode material in lithium-ion batteries. To enhance its electrochemical performance, a-FePO4 was composited with graphene oxide (GO) and subsequently reduced at different temperatures (250–450 °C) under N₂ atmosphere to obtain a series of a-FePO₄/rGO composites. Among them, the a-FePO₄-rGO-1 (reduced at 250 °C) exhibited the most superior performance, delivering a specific high discharge capacity of 117 mAh·g⁻¹ after 100 cycles at 1 C and an excellent rate capability of 98 mAh·g⁻¹ even at 10 C. Electrochemical impedance spectroscopy revealed that this composite possessed the lowest charge transfer resistance and most efficient Li⁺ diffusion kinetics. This study demonstrates that moderate-temperature thermal reduction is a critical strategy for optimizing the conductive network of a-FePO₄-rGO composites, thereby significantly improving the electrochemical properties of recycled FePO₄-based cathode materials.

In this study, we successfully synthesized olivine-type FePO₄ via an in situ oxidation method and further developed two composite cathode materials (o-FePO₄-1/GR-1 and o-FePO₄-1/GR-2) by incorporating graphene. The composites were characterized using scanning electron microscopy (SEM), X-ray diffraction (XRD), and X-ray Photoelectron Spectroscopy (XPS), revealing a three-dimensional porous layered structure with an enhanced surface area and strong interaction between FePO₄ nanoparticles and graphene layers. Electrochemical tests demonstrated that the composite electrodes exhibited significantly improved performance compared to pristine FePO₄, with discharge capacities of 147 mAh g⁻¹ at 1C and 163 mAh g⁻¹ at 0.1C for o-FePO₄-1/GR-2, approaching the level of LiFePO₄. The incorporation of graphene effectively enhanced the electrochemical reaction kinetics, highlighting the innovation of our method in developing high-performance cathode materials for lithium-ion batteries.