We now know that the formation of dendrites was the reason that Samsung's lithium-ion batteries malfunctioned last year. Research from Drexel University and Tsinghua University has found a way to mitigate this issue, opening the door to safer batteries in future generations of mobile devices.

Lithium-ion batteries have become the standard in portable electronic devices and, for the most part, people have grown accustomed to having power to their devices for extended usage. This has led to a quite an interesting problem where newer electronics, which are smaller and typically require more power, have less space to provide that power.

Lithium-ion batteries do offer the required energy, along with a massive amount of charge cycles, however, they run into issues as we reduce their size.

After Samsung’s Galaxy S7 fiasco, there was quite a bit of research invested into the cause of exploding Li-ion batteries. It was found to be that the dendrites, which in Lithium-ion batteries are microscopic fibers of lithium that spread across the electrolyte. These fibers typically form after a multitude of charge cycles and even more so when the battery is undergoing expeditious charging and discharging. If these fibers grew too quickly, they could pierce the electrolyte barrier and cause a short circuit in the other electrode.

 

These two images show dendrite formation. All images courtesy of Nature Communications [CC-BY 4.0]. Above image cropped from a larger image.

 

Preventing Dendrite Formation with Nanodiamonds

To resolve the dendrite issue, researchers developed a graphite electrode casing and filled it with lithium to prevent their formation. While this did resolve the safety concerns, it had inhibiting effects on the performance of the battery in regards to factors such as energy storage, which can be decreased by tenfold compared to pure lithium batteries.

A team of researchers, led by Yury Gogotsi and consisting of members from Drexel University in Philadelphia and Tsinghua University in Beijing, have developed an electrolyte solution with the addition of nanodiamonds that could have a significant influence on future battery design. The research team's effort was focused on creating uniform lithium plating and an overall more stable lithium anode.

The electroplating industry already makes use of the properties of nanodiamonds to create more uniform plating. When deposited, nanodiamonds have a tendency to slide together to create a uniform and smooth surface. The research team tested the nanodiamond-coated electrode by adding a commonly-used electrolyte solution to the electrode. It was found that the lithium ions from the electrolyte solution were capable of binding to the electrode plating in a uniform manner due to the nanodiamond surface having a low diffusion energy barrier. The result was uniform deposits of lithium, instead of long dendrites.

 

The electrolyte solution with (right) and without (left) nanodiamonds added.

 

The team ran tests on the nanodiamond coated battery and found that it had fully prevented the formation of dendrites under 100 charge cycles with 200-hour duration. While the charge cycle is far below the standards of our modern phones and laptops, the intention is to conduct additional research that could lead to a modified approach resulting in electrochemically-enhanced lithium battery performance.  

The researchers are currently working on testing various battery cells with different charge cycles to completely ensure dendrite suppression. Gogotsi noted that additional precautions will be needed such as safer electrode materials to completely safeguard the battery.

“Battery safety is a key issue for this research,” Gogotsi said. “Small primary batteries in watches use lithium anodes, but they are only discharged once. When you start charging them again and again, dendrites start growing. There may be several safe cycles, but sooner or later a short-circuit will happen. We want to eliminate or at least minimize that possibility."

The original research article can be found in the journal Nature Communications.

 

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