Researchers Tackle Problems With Silicon-Anode Batteries

Before unlocking a more sustainable future, better-performing batteries are needed. For example, applications like electric vehicles (EVs) and renewable energy require high-capacity batteries to function. 

 

EVs and renewables need high-capacity batteries. Image used courtesy of Adobe Stock

 

To make this dream a reality, many are looking past lithium-ion batteries in favor of promising new battery chemistries. One such chemistry is silicon-anode batteries, which have greater potential but are hindered by outstanding technical challenges.

Recently, researchers from Rice University have gotten closer to making silicon-anode batteries a reality. This article examines the promise of silicon-anode batteries, the technical challenges they face, and the research from Rice University.

 

The Promise of Silicon-Anode Batteries

One of the most promising emerging alternatives to lithium-ion batteries is the silicon-anode battery.

A silicon anode battery is one in which the conventional graphite anode of a lithium-ion battery is replaced by one made of silicon. The advantage here is that silicon as a material has the potential to bond with much more lithium-ions than graphite, resulting in it being able to store as much as 10x more lithium. The result is that silicon-anode batteries have the potential to significantly increase the energy storage capacity of a conventional lithium-ion battery.

A comparison of anode materials. Image used courtesy of C&EN

 

Another benefit of the improved material properties of silicon as compared to graphite is that silicon-anode batteries have the potential for faster charging times. Able to store more ions at a time, the silicon-anode battery can theoretically charge faster than a graphite-anode battery.

 

Silicon-Anode Challenges

Despite the potential benefits of silicon-anode batteries, technical challenges still exist.

One such challenge is the behavior of the solid-electrolyte interphase (SEI) layer at the electrode/electrolyte interface. An SEI layer is a natural passivation layer that forms in lithium-ion batteries due to reactions between the electrolyte and electrode in the initial phases of battery operation. However, in silicon-anode batteries, it represents a problem.

 

Silicon anode batteries form an SEI layer at the anode/electrolyte interface. Image used courtesy of UPS Battery Center

 

In standard lithium-ion batteries, the SEI layer eventually insulates the electrolyte from the anode, preventing the reaction from continuing. Small amounts of lithium are consumed to form this layer, which takes away from the battery’s capacity. Since this only happens once in lithium-ion batteries, its effects are negligible.

In a silicon-anode battery, however, the SEI can break throughout the subsequent charge and discharge cycles due to changes in volume during cycling. The result is that the SEI layer is continually formed and broken down in silicon-anode batteries. This continuation consumption of lithium ions to form the SEI layer depletes the batteries’ lithium ions, significantly degrades energy storage, and hurts battery lifetime.

 

Prelithiation Research

In their recently published research paper, researchers from Rice discuss a new method for avoiding the lithium depletion caused by the SEI layer.

 

Prelithiation with surfactant. Image used courtesy of Rice University

 

To do this, the researchers employed a technique called prelithiation, which introduces lithium ions into the anode of a battery during manufacturing to compensate for the ions lost during the formation of SEI layers. The researchers applied the idea of prelithiation in a unique way by using a surfactant material in the prelithiation process to disperse the particles evenly throughout the electrode. The researchers found that applying their surfactant in a spray-painting method was the most effective at achieving uniform distribution while remaining compatible with standard manufacturing processes.

The result of the research was that applying a spray-coated prelithiation mixture to the silicon anode improved battery life by 22%. When surfactant was added to the equation, battery life was improved by 44%.

 

Silicon-Anode and a Sustainable Future

Silicon anode technology has gained significant popularity as the world demands higher-capacity batteries. With the new results from Rice University, the researchers believe that they’ve found a way to make silicon-anode batteries more feasible by improving battery life with a new manufacturing-compatible process for prelithiation.