In-Mg-Al共掺杂高电压钴酸锂正极材料的研究

Research on In-Mg-Al Co-doped high voltage LiCoO2 cathode materials

钴酸锂正极材料(LiCoO_(2))具有较高的能量密度,是当今锂离子电池正极材料的主流。然而钴酸锂在高压条件下的不可逆相变与析氧会导致容量的快速衰减与安全隐患,严重制约了钴酸锂正极材料的实际应用。采用In-Mg-Al共掺杂方法,制备了高压钴酸锂正极材料,采用X射线衍射与扫描电镜研究其物相结构与表面形貌;采用电化学阻抗谱研究元素掺杂对正极表面固体电解质膜的影响。通过组装钴酸锂/金属锂扣式半电池与钴酸锂/石墨软包全电池评估其电化学性能。结果发现,In-Mg-Al共掺杂后,所组装的钴酸锂/金属锂扣式半电池在3~4.6 V区间的0.1 C放电克容量可达到217.6 mAh/g,在0.1~5C区间倍率性能均优于未经掺杂与经Mg-Al共掺杂的钴酸锂样品。所组装的钴酸锂/石墨软包全电池0.5 C循环500圈后容量保持率可达75.1%。

Due to its high energy density,lithium cobalt oxide(LiCoO_(2))cathode material is the mainstream of lithiumion battery cathode material.However,the irreversible phase transformation and oxygen release under high voltage can cause rapid capacity degradation and safety problems,which seriously restrict the practical application of LiCoO_(2).In this study,In-Mg-Al co-doping was used to prepare the high voltage LiCoO_(2)cathode material.The phase structure and surface morphology were studied by X-ray diffraction and scanning electron microscopy.Electrochemical impedance spectroscopy was used to study the effect of element doping on solid electrolyte interphase on the positive electrode surface.The electrochemical performance was evaluated by assembling LiCoO_(2)/lithium metal coin-type half cells and LiCoO_(2)/graphite pouch-type full cells.With In-Mg-Al co-doping,the as-assembled LiCoO_(2)/lithium metal half cells delivere a 0.1C discharge capacity of 217.6 mAh/g in the range of 3-4.6 V,and have better rate performances than the undoped and the Mg-Al co-doped LiCoO_(2)from 0.1 to 5C.The capacity re‐tention rate of the LiCoO_(2)/graphite pouch-type full cell is 75.1%after 500 cycles at 1C.