Researchers have created a solid material through which lithium ions can freely flow, meaning it could be used to replace liquid electrolytes in sustainable lithium-ion batteries, making them safer and more efficient. 

Humanity is now well aware of the effect that the burning of fossil fuels and the release of greenhouse gasses has on the climate. This has increased the need for energy alternatives to fossil fuels, with rechargeable batteries at the forefront of this demand.

In particular, lithium-ion batteries have emerged and matured, powering everything from the electronics in our pockets to the vehicles that carry us. In fact, Statista estimated in 2020 that lithium-ion batteries accounted for 185 gigawatts (GWh) of energy consumed, with this projected to reach 2,035 GWh by 2030. 

Resolving flaws in this technology has become arguably more pressing. Lithium-ion batteries are composed of a negative iodine electrode and a positive zinc electrode with a liquid or ‘aqueous’ electrolyte medium between the two. The electrolyte of the battery transfers charge-carrying particles called ions back and forth between the battery’s two electrodes as the battery charges and discharges. 

The use of a liquid electrolyte to shuttle lithium-ions in these batteries means a lower energy output compared to commercial non-aqueous lithium batteries, and causes the growth of jagged outcrops of zinc called dendrites  on anodes that can result in reduced efficiency during charge/recharge cycles, even short-circuiting. This latter aspect of these batteries can cause one of the major issues with lithium-ion batteries, which is the inherent risk of burning or even explosion as the result of thermal runaway, with overheated batteries responsible for a number of fires in the past.

Thus, materials scientists are hard at work developing substances that can make lithium-ion batteries both safer and more efficient. A new paper published in the journal Science reports the development of a solid material that is composed of non-toxic, earth-abundant elements that rapidly conduct lithium ions. 

The material has high enough lithium ion conductivity to replace the liquid electrolytes in current lithium-ion batteries, improving both energy capacity and safety.

An interdisciplinary AI-guided approach to lithium-ion batteries

Andrij Vasylenko, a computational material scientist at the University of Liverpool and co-author on the study, explained the secret to this material’s conductivity to lithium ions is the high number of various atomic coordinations within it, which result in multiple, low-energy barrier pathways for lithium atoms to move through.

“This results in high conductivity and its ‘easy flow’ of lithium ions comparable to that in liquid electrolytes,” he said. “The latter determines a range of technical parameters of a battery, such as duration of charging and charge density, or in terms of electric vehicles, the range accessible to them on a single charge.”

The team from the University of Liverpool used an interdisciplinary approach that combined computation and experiment guided by artificial intelligence (AI) to support the decisions made by its chemistry experts. This allowed them to synthesize the material in the lab and then determine the arrangement of atoms in that material’s structure to determine how freely ions would flow through it and finally demonstrate its capability in a battery cell.

“Thanks to our design strategy, the discovered material opens up a new understanding of what atomic coordination — the arrangement of atoms in materials — should be sought after for developing new highly functional materials for battery applications and beyond,” said Vasylenko.

The team said that this transformative approach and the use of AI led to the creation of one of the only solid lithium-ion transporting materials that is capable of replacing liquid electrolytes in batteries, and in the process, changing what high-performance solid-state electrolytes look like.

Vasylenko added that substituting liquid electrolytes with solid-state materials, like the new solid ion-transferring material the team developed, could not only dramatically improve these parameters but can also lower the risk of exploding, which is a weak spot of the current technology.

Before the material can be widely adopted, more research is needed to ensure it can be manufactured in a sustainable way without producing harmful by-products or consuming non-sustainable materials, and to determine if scalability is viable. The interface between the electrolyte and the electrodes, essential parts of batteries, must be investigated. 

“Having developed the AI model to identify the likely combinations of chemical elements to be synthetically accessible in the lab, I was surprised how many of the predicted elemental combinations have actually found their material realization, as this is the fifth set of elements that have led to the discovery of a new material in our group, I hope, with more to come,” Vasylenko concluded.

Reference: Guopeng Han., et al., Superionic lithium transport via multiple coordination environments defined by two-anion packing, Science (2024). DOI: 10.1126/science.adh5115

Feature image credit: Daniel Falcão on Unsplash