A key challenge in enabling all-solid-state Li-ion batteries is the development of solid electrolyte materials with high Li ionic conductivity and good electrochemical stability.Current research efforts on solid-state Li-ion conductors focus mostly on oxides and sulfides. Unfortunately, oxide and sulfide chemistries have an undesirable trade-off between ionic conductivity and stability. New solid-state chemistries that can exhibit a low activation energy, good stability, and other desirable properties are a promising research direction for new solid electrolytes in solid-state batteries.

Using ab initio computation, we systematically explored new anion chemistries beyond oxides and sulfides, such as nitrides and halides. Our computation found nitride anion chemistry exhibits unique stability against Li metal, which is either thermodynamically intrinsic or a result of stable passivation. Many nitrides materials can serve as promising lithium metal protection materials to achieve long-term stability.

In addition, our first principles computation study confirmed that chlorides and bromides exhibit fast Li-ion conduction, wide electrochemical stability, and good cathode interface compatibility. We found Cl and Br anion chemistries can achieve fast Li-ion conduction in a variety of anion sublattices, and do not require the rare bcc anion lattice as in current fast ion-conducting sulfides or the concerted migration mechanism in current fast-conducting oxides. Further, we found chlorides and bromides generally exhibit wide electrochemical windows, poor electronic conductivity, and good cathode interface compatibility, and thus hold desirable conducting and stability properties for SE applications.

Our presentation highlight nitrides, chlorides and bromides as highly promising alternative chemistries for solid electrolytes in solid-state batteries.

References:

Shuo Wang, Qiang Bai, Adelaide M. Nolan, Yunsheng Liu, Sheng Gong, Qiang Sun, and Yifei Mo, “Lithium Chlorides and Bromides as Promising Solid-State Chemistries for Fast Ion Conductors with Good Electrochemical Stability”, Angewandte Chemie (online)

Adelaide Nolan, Yizhou Zhu, Xingfeng He, Qiang Bai, Yifei Mo, “Computation-Accelerated Design of Materials and Interfaces for All-Solid-State Lithium-Ion Batteries”, Joule, 2, 2016-2046 (2018)

Yizhou Zhu, Xingfeng He, Yifei Mo, “Strategies Based on Nitride Materials Chemistry to Stabilize Li Metal Anode”, Advanced Science, 1600517 (2017)