High-voltage Ni-rich cathodes, which show high energy density and large cost-effectiveness, hold great promise for power Li-ion batteries. However, the unstable cyclic structure rooted in stress restricts their practical applications. In this work, we propose a strategy using a dispersed Eu 2 O 3 buffer phase to mitigate the high-voltage cyclic stress . The optimized Ni-rich cathode shows excellent high-voltage thermal stability and practical long-term cycling stability. For the constructed 4.6 V full cell, a superior capacity retention of 92 % after 200 cycles is observed. The enhanced cyclic properties are ascribed to the mitigated stress, as revealed by multi-characterizations such as in-situ X-ray diffractions and finite element simulation. As expected, the mitigated stress well stabilizes the oxygen lattice and preserves the particle structures. More importantly, the approach is confirmed to be versatile in other high-voltage cathodes. Also, other available elements including La and Dy for the construction of buffer phases are outlooked.
Xiaojuan Lu,Mingyang Duan,Jingyu Xiang,Yuning Liang,Songtao Liu
Although solid-state lithium electrolytes have the potential to reduce the safety issues associated with organic liquid electrolytes , disadvantages such as low total conductivity, large interface impedance, and delamination of the interface due to cyclic stress still need to be addressed. The solid-state lithium-ion conductor Li 0.33 La 0.56 TiO 3 (LLTO) was prepared via a hydrothermal route by using CTAB as templates in this paper. Perovskite LLTO with micro-porous channels was obtained and the total conductivity is comparable to the non-porous LLTO. Porous LLTO pellets are infiltrated with the non-porous LLTO precursor solution, and the total conductivities of the infiltrated porous LLTO are all higher than those without infiltration. After infiltration, the porous LLTO calcined at 600 °C achieves the highest total conductivity, 7.88 × 10 −5 S/cm. The fracture toughness of the infiltrated LLTO is higher than that of the non-porous LLTO. The results demonstrate a new way to prepare solid-state lithium-ion conductors with high ionic conductivity and great tolerance to cyclic stress.
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