Jie Biao,Bing Han,Yidan Cao,Qidong Li,Guiming Zhong,Jiabin Ma,Likun Chen,Ke Yang,Jinshuo Mi,Yonghong Deng,Ming Liu,Wei Lv,Feiyu Kang,Yan-Bing He
Poor ion and high electron transport at the grain boundaries (GBs) of ceramic electrolytes are the primary reasons for lithium filament infiltration and short-circuiting of all-solid-state lithium metal batteries (ASLMBs). Herein, it is discovered that Li 2 CO 3 at the GBs of Li 7 La 3 Zr 2 O 12 (LLZO) sheets is reduced to highly electron-conductive LiC x during cycling, resulting in lithium penetration of LLZO. The ionic and electronic conductivity of the GBs within LLZO can be simultaneously tuned using sintered Li 3 AlF 6 . The generated LiAlO 2 (LAO) infusion and F-doping at the GBs of LLZO (LAO-LLZOF) significantly reduce the Li 2 CO 3 content and broaden the energy bandgap of LLZO, which decreases the electronic conductivity of LAO-LLZOF. LAO forms a 3D continuous ion transport network at the GB that significantly improves the total ionic conductivity. Lithium penetration within LLZO is suppressed and an all-solid-state LiFePO 4 /LAO-LLZOF/Li battery stably cycled for 5500 cycles at 3 C. This work reveals the chemistry of Li 2 CO 3 at the LLZO GBs during cycling, presents a novel lithium penetration mechanism within garnet electrolytes, and provides an innovative method to simultaneously regulate the ion and electron transport at the GBs in garnet electrodes for advanced ASLMBs.
Run Yu,Yongjin Chen,Chengyu Li,Shaojun Wang,Pengcheng Li,Ruihan Tang,Cong Gao,Chuanlong Lin,Xiang Gao
The garnet-type oxide Li 7 La 3 Zr 2 O 12 solid-state electrolytes (SSEs) are considered as a reliable option in all-solid-state lithium batteries (ASSLBs) due to its excellent properties. However, it still faces challenges such as limited ionic conductivity and low air stability. In this work, Ga 3+ and Ta 5+ co-doped samples Li 7−3 x − y Ga x La 3 Zr 2− y Ta y O 12 (Ga x Ta y -LLZO) synthesized via the solid-state method are demonstrated to stabilize the cubic phase, regulate the concentration of Li vacancies in LLZO, and improving the Li + transport channels. As a result, the Ga0.1Ta0.3-LLZO sample achieves a high conductivity of ∼1 mS cm −1 . Furthermore, we discovered that in addition to the previously reported effects of decreasing grain boundary density and the inert LiGaO 2 secondary phase at grain boundaries, the synergistic effect of introducing multiple dopant ions, which enhances lattice stability, is also a key factor contributing to improved air stability. Our findings demonstrate that co-doping strategy with Ga 3+ /Ta 5+ is an effective method for simultaneously enhancing conductivity and air stability of LLZO, laying solid foundation for the application of SSEs in ASSLBs.
Replacing flammable liquid electrolytes with solid polymer electrolytes is a promising route to improve safety of lithium (Li)-metal batteries. However, developing a suitable high-performance electrolyte with both high ionic conductivity and interface stability against electrodes remains as a challenge. Herein, we design a poly(propylene carbonate) (PPC)/poly(vinylidene fluoride-hexafluoropropylene) [P(VDF-HFP)]–based asymmetric solid electrolyte with a 3D blow-spun Li 7 La 3 Zr 2 O 12 (LLZO) framework. The controllable degradation of PPC facilitates the wettability and stability between the electrolyte and Li metal. The P(VDF-HFP) with good electrochemical stability is used to match with cathode. With the support of the 3D LLZO Li-ion conductor, the electrolyte displays high ionic conductivity (4.9 × 10 −4 S cm −1 at room temperature). The Li||Li symmetric cells assembled with this electrolyte show a long cycling life of more than 2700 h at 100 μA cm −2 . The electrolyte also delivers an excellent cycling performance in solid-state LiFePO 4 ||Li batteries (300 cycles with a capacity retention of 91.3%).
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