Transforming Energy Storage: Xin Li's Advances in Solid-State Batteries

Breaking the Wall of Solid-State Battery Innovation

Winner Interview 2024: Engineering & Technology

Xin Li is at the forefront of solid-state battery innovation. His research addresses the unique electrochemical interfaces in these batteries, offering groundbreaking design strategies that enhance performance and safety. By bridging experimental work and computational design, and fostering collaboration between academia and industry, Li's work promises to revolutionize energy storage and accelerate the electrification of mobile devices.

Which wall does your research or project break?

My research breaks the walls of solid-state battery innovation. Solid-state battery is a new type of battery that can potentially replace the commercial Li-ion battery by breakthrough performance and safety. A successful transition to solid-state battery will greatly speed up the electrification of mobile devices, which provides an important technological solution for our society to combat climate-change. However, the unique solid-solid interface in such new batteries show drastically different electrochemical behavior in comparison with the conventional solid-liquid interface in commercial Li-ion batteries, which challenges our understanding and limits our design capability. My group's research focused on fundamental scientific understandings of such unique electrochemical interfaces, which breaks the wall of solid-state battery innovation by identifying design opportunities for advanced solid-state batteries that utilize beneficial interface reactions to arrest Li dendrite penetration and prevent cathode interface reaction from proceeding progressively.

This design strategy allows our battery to work with the desired Li metal anode and a variety of high energy cathodes. We demonstrated breakthrough battery performance, making the battery technology extremely attractive to scale up to larger capacity for industrial applications. It is worth noting that those interface reactions were previously thought to be detrimental and should be avoided in a solid-state battery design. Our counterintuitive design strategy is pivotal here by articulating for the first time that these reactions can amazingly become a big design opportunity upon properly being transformed into beneficial reactions.

The wall that my research also breaks is the barrier between experimental work and computational design capability. Through a combined understanding between experimental characterization and computational simulation we were able to design the simplest computational descriptor that is compatible with the materials genome approach, whose power is further unlocked by machine learning and AI approach to design new materials for advanced solid-state batteries.

Furthermore, my research breaks the wall between university research and commercialization. My group focuses on the most performance-relevant understanding and interacts frequently with battery experts from battery industry, making sure that the technology is compatible with future industrial scaling-up throughout the development process in the university lab. I also encourage my graduate students to think big and discuss battery startup cases frequently in the group, which forms one important foundation for the startup company that I cofounded, as it turns out later that both the CEO and CTO are PhD students graduated from my group. 

What are the three main goals of your research or project?

The first goal of my research is to enable the Li metal as anode for solid-state batteries, which is considered as the holy grail in the anode design for Li-ion batteries due to the attractive high energy density of such a battery cell (potentially double the energy density of Li ion batteries). However, Li metal anode was never commercialized in Li-ion batteries due to the Li dendrite penetration issue that can easily cause short circuit of batteries. We created the multi-electrolyte-layer for the separator design to arrest the Li dendrite at the interface between two solid electrolyte layers and implemented the silicon-graphite anode protection for Li metal anode that allows homogeneous Li deposition at high cathode loading and current density through the interaction between Li and Si at the all-solid interface. The design enabled Li metal anode to run stably at 5 ~ 10 times higher current density (superfast charging speed) than commercial Li-ion batteries and 5 ~ 10 times longer cycling lifetime (a type of battery that can potentially run for a century).

The 2nd goal of my research is to obtain fundamental understanding of those unique electrochemical interfaces in all solid-state batteries that can be used for the design of advanced materials. My group uses a combination of electrochemical measurement, experimental synthesis and characterization, and computational simulation approaches. We try our best to articulate experimentalists’ invaluable intuition into physical picture that can be described by fundamental languages in thermodynamics and kinetics, with the goal to identify the descriptor that is most relevant to the performance of interest and compatible with high-throughput computation and AI-based materials design. Our design has led to successful computational design of materials that greatly enhanced the performance of solid-state batteries.

The 3rd goal of my research is to minimize the barriers from lab research to future scaling up process in the battery industry. We respect the existing expertise from Li-ion battery industry and interact frequently with them. We think carefully about the compatibility with future scaling up when we innovate in the lab. Our innovation toward much longer lifetime of batteries also brings down the cost per cycle dramatically, which is important to the cost-performance of such commercial battery product in the future.

What advice would you give to young scientists or students interested in pursuing a career in research, or to your younger self starting in science?

I will suggest that young scientists or students when pursuing a career in research to choose emerging new fields with strong society needs, as there will be much more opportunities. For example, solid-state battery is such a field when I entered it, and my career grows together with the surge of the field. Also, for energy-related research, if there is a related industry but your research studies a relatively new direction, you will also benefit from the interaction with such an industry in terms of industrial funding and commercialization opportunities. In addition, breakthrough in your research is often not from planning. You should follow your intuition and gut feeling, even it is sometimes counterintuitive to the conventional wisdom in the field. You should have the gut to insist in some of your ideas, especially when it is criticized, as real breakthrough results or concepts often make most people in the field feel uncomfortable to accept. That said, you should carefully study and test your hypothesis, ideally by a combination of experiment and computation nowadays. Lastly, you won’t be able to finish all works by yourself, so seeking for collaborators with complementary skillsets who can share passion with you and argue with you frankly. 

What impact does your research or project have on society?

Solid state battery will show breakthrough performance beyond commercial Li-ion battery in the future, which will greatly speed up global electrification and help combat climate-change.