In this work, we first report the composite of CuNi₂(PO₄)₂/C (CNP/C) can be employed as the high-capacity conversion-type cathode material for rechargeable Li-ion batteries (LIBs), delivering a reversible capacity as high as 306 mA h g^–1 at a current density of 20 mA g^–1. Furthermore, CNP/C also presents good rate performance and reasonable cycling stability based on a nontraditional conversion reaction mode. X-ray diffraction (XRD) and high-resolution transmission electron microscopy (HRTEM) characterizations show that CNP is reduced to form Cu/Ni and Li₃PO₄ during the discharging process, which is reversed in the following charging process, demonstrating that a reversible conversion reaction mechanism occurs. X-ray absorption spectroscopy (XAS) discloses that Ni²⁺/Ni⁰ exhibits a better reversibility compared to Cu²⁺/Cu during the conversion reaction process, while Cu⁰ is more difficult to be reoxidized during the recharge process, leading to capacity loss as a consequence. The fundamental understanding obtained in this work provides some important clues to explore the high-capacity conversion-type cathode materials for rechargeable LIBs.

中文翻译：

---

新型锂离子电池正极材料CuNi ₂（PO ₄）₂ / C电化学反应机理的见解

在这项工作中，我们首先报告了CuNi ₂（PO ₄）₂ / C（CNP / C）的复合材料可用作可再充电锂离子电池（LIB）的高容量转换型正极材料，可逆容量高达306毫安汞柱^-1以20mA g的电流密度^-1。此外，基于非传统转化反应模式，CNP / C还具有良好的速率性能和合理的循环稳定性。X射线衍射（XRD）和高分辨率透射电子显微镜（HRTEM）表征表明，CNP被还原形成Cu / Ni和Li ₃ PO ₄在放电过程中，其在随后的充电过程中被逆转，表明发生了可逆的转化反应机理。X射线吸收光谱法（XAS）揭示，与Cu ²⁺ / Cu相比，Ni ²⁺ / Ni ⁰在转化反应过程中具有更好的可逆性，而Cu ⁰在充电过程中更难被再氧化，从而导致容量增加。结果是损失。在这项工作中获得的基本理解为探索可再充电LIB的高容量转换型阴极材料提供了一些重要线索。