微量Mg/F表面梯度渗透改善高电压LiCoO₂界面脆弱

采用高温固相法在1050℃下烧结，制备了LiCoO₂低浓度梯度改性样品，分别为LiF掺杂包覆(LCOLF、LCO@LF)和MgF₂掺杂包覆(LCOMF、LCO@MF)。通过光电子能谱、透射电子显微镜和电化学技术等表征方法，对比分析材料形貌及电化学性能。结果表明，体相掺杂复合电极中，LCOLF热重测试显示出最优热稳定性，LCOMF晶体中(003)和(104)晶面间距收缩；45℃下1C倍率循环70圈后，LCOLF和LCOMF比容量分别为141.45和166.98mAh·g^-1，循环性能优于LiCoO₂。表面包覆复合电极中，LCO@LF和LCO@MF晶粒表面光洁且晶格氧键价都向更高结合能方向增强；LCO@MF构建了坚实且紧密的包覆层，循环70圈后，放电比容量和容量保持率分别为183mAh·g^-1和91.26%(LCO@LF分别为154.38mAh·g^-1和77.54%)，循环性能显著优于体相掺杂。

Low-concentration gradient-modified samples of LiCoO₂ were prepared by sintering at 1 050℃ using high-temperature solid-phase method, and were coated with LiF doping (LCOLF, LCO@LF) and MgF₂ doping (LCOMF, LCO@MF). The material morphologies and electrochemical properties were compared and analyzed utilizing characterization tests such as X-ray photoelectron spectroscopy, transmission electron microscopy, and electrochemical techniques. The results show that in bulk-doping composite electrodes, the thermogravimetric test demonstrated that LCOLF had optimal thermal stability. In LCOMF crystals, crystal plane spacing of (003) and (104) contracted; after 70 cycles at 1C rate under 45 ℃, the specific capacities of LCOLF and LCOMF were 141.45 and 166.98 mAh·g^-1 respectively, and their cycling performance was superior to that of the LiCoO₂. In the surface-coated composite electrodes, LCO@LF and LCO@MF grains had clean surfaces and the bond valence of lattice oxygen was enhanced toward higher binding energy; LCO@MF built a solid and compact coating layer, and the specific capacity and capacity retention after 70 cycles were 183 mAh·g^-1 and 91.26% (that of LCO@LF were respectively 154.38 mAh·g^-1 and 77.54%). The cycling performance of surface-coated composite electrodes was significantly better than that of bulk-doping composite electrodes.