Inorganic NASCION‐type Li conductors have great potential to bring high capacity solid‐state lithium batteries (SSLBs) to realization, due to properties such as high ionic conductivity, stability under ambient conditions, wide electrochemical stability window, and inexpensive production. However, despite the merits, the integration of NASCION-type electrolytes in SSLBs is still hampered by the formation of a chemically unstable interface when it is coupled with a Li metal anode.

Scientists at Chalmers University of Technology, Sweden, and Xi’an Jiaotong University, China have now developed a multifunctional interlayer between the electrolyte and the Li-metal anode, made of a spreadable material that helps improve solid-state battery current density tenfold, while also increasing performance and safety.

The interlayer makes the battery cell much more stable, and therefore able to withstand much higher current density. It is also very easy to apply the soft mass onto the lithium metal anode in the battery. Source: Chalmers

… the LAGP‐IL interlayer, which is of ultrahigh thermal stability and non‐inflammability, is able to physically separate the bulk LAGP electrolyte and Li metal avoiding the formation of an MCI and eventually suppressing the degradation reactions as well as thermal runaway. This interlayer significantly lowers the interfacial resistance and allows the use of a high areal current density, 1.0 mA cm⁻², at ambient temperature, which is roughly an order of magnitude higher than previously reported (0.1–0.3 mA cm⁻²).

—Xiong et al.

The interlayer between electrolyte and Li metal anode is designed as a hybrid paste formed by ball milling of a NASICON-type superionic conducting glass ceramics (Li_1+xAl_xGe_2−x(PO₄)₃ (LAGP)) nanoparticles and a room temperature ionic liquid (IL). The liquid encapsulates the LAGP particles and makes the interlayer soft and protective.

The functionality of the interlayer stems from the high ionic conductivity of both components and the formation of a chemically stable interphase on the Li metal anode by controlled breakdown of the IL (N‐Methyl‐(n‐butyl) imidazolium bis(fluorosulfonyl)imide, BMIM‐FSI).

This interlayer makes the battery cell significantly more stable, and therefore able to withstand much higher current density. What is also important is that it is very easy to apply the soft mass onto the lithium metal anode in the battery—like spreading butter on a sandwich.

—Shizhao Xiong, Department of Physics at Chalmers

Alongside Chalmers Professor Aleksandar Matic and Professor Song’s research group in Xi’an, Shizhao Xiong has been working for a long time on crafting a suitable interlayer to stabilize the interface for solid-state batteries. An open-access paper on the work appears in the journal Advanced Functional Materials.

This is an important step on the road to being able to manufacture large-scale, cost-effective, safe and environmentally friendly batteries that deliver high capacity and can be charged and discharged at a high rate.

—Aleksandar Matic, Professor at the Department of Physics at Chalmers

The researchers are active at Chalmers University of Technology, Xi’an Jiaotong University, China, the Technical University of Denmark and the National University of Defense Technology, Changsha, Hunan, China.

Resources

• Xiong, S., Liu, Y., Jankowski, P., Liu, Q., Nitze, F., Xie, K., Song, J., Matic, A., (2020) “Design of a Multifunctional Interlayer for NASCION‐Based Solid‐State Li Metal Batteries.” Adv. Funct. Mater. doi: 10.1002/adfm.202001444