Rechargeable batteries with lithium metal anodes can deliver > 2x energy density improvement over state of the art lithium ion batteries. The lithium metal anode, however, suffers from dendrite growth, large volume change, and poor efficiency due to parasitic chemical reactions with the electrolyte.

We have taken a comprehensive approach involving surface protection layers, 3D hosts and new electrolyte compositions to address these challenges.

1. Long-life Li/SPAN batteries

Li-S batteries are ideal choices for energy storage due to theoretically high energy density, low cost material, and a lack of need for transition metals. However, sulfur cathode has been plagued with complex degradation mechanisms that limit its cycle life. We have focused on developing new electrolyte compositions that can simultaneously enable high efficiency lithium metal cycling and long-life sulfur cathode using a polymer-sulfur cathode known as SPAN. This cell chemistry holds to promise to finally overcome the cycling stability barrier for Li-S batteries.

Cycling performance of Li||SPAN cells. (A) Comparison of capacities of SPAN in different electrolytes. Charge/discharge voltage profiles of SPAN: (B) In 1 M LiFSI/EC-DEC electrolyte. (C) In 1 M LiFSI/DEE electrolyte. (D) In 1.8 M LiFSI/DEE-BTFE electrolyte. At 0.5 mA cm–2, between 1 V and 3 V.

Ultrahigh coulombic efficiency electrolyte enables Li||SPAN batteries with superior cycling performance, Haodong Liu, John Holoubek, Hongyao Zhou, Amanda Chen, Naijen Chang, Zhaohui Wu, Sicen Yu, Qizhang Yan, Xing Xing, Yejing Li, Tod A. Pascal, Ping Liu, Materials Today, DOI: 10.1016/j.mattod.2020.09.035

2. In-situ solution coatings to protect lithium

In this approach, we develop solution reactions to form desired coating layer on lithium in-situ. Recently, lithium methyl carbonate, a well-known compound in the solid electrolyte interface, has been shown to form directly on lithium surface through a prescribed solution reaction. This coating effectively suppresses dendrite formation and enables stable lithium metal cycling. We are extending this approach to other liquid phase reactions to form protective layers directly on lithium metal electrodes.

Suppressing Lithium Dendrite Growth with a Single-Component Coating, Haodong Liu, Hongyao Zhou, Byoung-Sun Lee, Xing Xing, Matthew Gonzalez, and Ping Liu, ACS Applied Materials & Interfaces, 2017

3. 3D host to minimize volume change

Lithium metal electrode experiences large volume changes during deposition and stripping. A properly designed 3D conducting host can reduce effective currently density and minimize macroscopic volume change. The host needs to be easily fabricated, preferably using coating processes compatible with current battery manufacturing. Finally, the use of 3D host increases the area between lithium metal and the electrolyte, which might reduce Coulombic efficiency. We have developed a multifunctional host made of carbon and lithium nitrate. Here the nitrate serves as both a structural member to host lithium metal and a reservoir of additive to improve lithium metal deposition when it slows leaches into the electrolyte.

A Scalable 3D Lithium Metal Anode, Haodong Liu, Xiujun Yue, Xing Xing, Qizhang Yan, Jason Huang, Victoria Petrova, Hongyao Zhou, Ping Liu, Energy Storage Materials. DOI:10.1016/j.ensm.2018.09.021