Yeh Nan-Hung, Wang Fu-Ming, Khotimah Chusnul, Wang Xing-Chun, Lin Yi-Wen, Chang Shih-Chang, Hsu Chun-Chuan, Chang Yung-Jen, Tiong Lester, Liu Chia-Hao, Lu Ying-Rui, Liao Yen-Fa, Chang Chung-Kai, Haw Shu-Chih, Pao Chih-Wen, Chen Jeng-Lung, Chen Chi-Liang, Lee Jyh-Fu, Chan Ting-Shan, Sheu Hwo-Shuenn, Chen Jin-Ming, Ramar Alagar, Su Chia-Hung
Graduate Institute of Applied Science and Technology, National Taiwan University of Science and Technology,Taipei 106335, Taiwan.
Sustainable Energy Center, National Taiwan University of Science and Technology, Taipei 106335, Taiwan.
ACS Appl Mater Interfaces. 2021 Feb 17;13(6):7355-7369. doi: 10.1021/acsami.0c22295. Epub 2021 Feb 3.
Ni-rich high-energy-density lithium ion batteries pose great risks to safety due to internal short circuits and overcharging; they also have poor performance because of cation mixing and disordering problems. For Ni-rich layered cathodes, these factors cause gas evolution, the formation of side products, and life cycle decay. In this study, a new cathode electrolyte interphase (CEI) for Ni self-oxidation is developed. By using a branched oligomer electrode additive, the new CEI is formed and prevents the reduction of Ni to Ni on the surface of Ni-rich layered cathode; this maintains the layered structure and the cation mixing during cycling. In addition, this new CEI ensures the stability of Ni that is formed at 100% state of charge in the crystal lattice at high temperature (660 K); this prevents the rock-salt formation and the over-reduction of Ni to Ni. These findings are obtained using in situ X-ray absorption spectroscopy, operando X-ray diffraction, operando gas chromatography-mass spectroscopy, and X-ray photoelectron spectroscopy. Transmission electron microscopy reveals that the new CEI has an elliptical shape on the material surface, which is approximately 100 nm in length and 50 nm in width, and covers selected particle surfaces. After the new CEI was formed on the surface, the Ni self-oxidation gradually affects from the surface to the bulk of the material. It found that the bond energy and bond length of the Ni-O are stabilized, which dramatically inhibit gas evolution. The new CEI is successfully applied in a Ni-rich layered compound, and the 18650- and the punch-type full cells are fabricated. The energy density of the designed cells is up to 300 Wh/kg. Internal short circuit and overcharging safety tests are passed when using the standard regulations of commercial evaluation. This new CEI technology is ready and planned for future applications in electric vehicle and energy storage.
富镍高能量密度锂离子电池由于内部短路和过充电而对安全构成巨大风险；由于阳离子混合和无序问题，它们的性能也很差。对于富镍层状正极，这些因素会导致气体逸出、副产物形成以及循环寿命衰减。在本研究中，开发了一种用于镍自氧化的新型阴极电解质界面（CEI）。通过使用支化低聚物电极添加剂，形成了新的CEI，并防止富镍层状阴极表面的镍还原为镍；这维持了循环过程中的层状结构和阳离子混合。此外，这种新型CEI确保了在高温（660 K）下晶格中在100%充电状态下形成的镍的稳定性；这防止了岩盐的形成以及镍过度还原为镍。这些发现是通过原位X射线吸收光谱、原位X射线衍射、原位气相色谱 - 质谱以及X射线光电子能谱获得的。透射电子显微镜显示，新的CEI在材料表面呈椭圆形，长度约为100 nm，宽度约为50 nm，并覆盖选定的颗粒表面。在表面形成新的CEI后，镍自氧化逐渐从材料表面影响到整体。发现Ni - O的键能和键长得以稳定，这极大地抑制了气体逸出。新的CEI成功应用于富镍层状化合物，并制备了18650型和冲压型全电池。所设计电池的能量密度高达300 Wh/kg。按照商业评估的标准规定进行测试时，通过了内部短路和过充电安全测试。这种新型CEI技术已准备好并计划在电动汽车和储能领域未来应用。
