The need for better battery energy storage systems is evident. The percentage of those with smart phones continually increases, and electric cars are certainly the future. Battery solutions for these items tend to make up roughly a quarter of the overall cost when purchasing them. To date, lithium batteries have provided the best solution, offering both high density and convenience. But these are not without problems. In addition to being costly and large, their primary substance, lithium, is not overly abundant in supply. As a result, researchers are actively pursuing other options for battery energy storage.
Some of the most recent investigations in this regard has involved different types of ions. Rather than using lithium, some researchers are exploring zinc batteries and sodium batteries. Likewise, they are also identifying new ways to create batter energy storage systems without the typical anode structure. Novel techniques are being employed to eliminate the anode component, which offers the possibility for smaller and less costly solutions. Based on these recent developments, it may just be that anode-free zinc and sodium batteries could soon replace traditional ones. And if so, this could be a major game-changer overall.
“The problem has been, with this [anode-free battery] chemistry, no one ever showed this anode-free battery can have a reasonable lifetime. They always fail very quickly or have a very low capacity or require special processing of the current collector.” – Peng Bai, Assistant Professor, Department of Energy, Environmental & Chemical Engineering, McKelvey School of Engineering, University of Washington, St. Louis
The Basics of Batter Energy Storage
In order to appreciate how anode-free batteries might be a good idea, the basics of battery energy storage should be understood. In a traditional battery, including lithium batteries, there is a cathode and an anode. (Read up on lithium batteries and their alternatives in this Bold story.) The cathode and anode have different charges, and the metal ions like lithium travel from one to the other. When lithium ions travel from anode to cathode, they release electrons which are collected by a current collector. This provides the battery with energy, which we use on our devices and other items. Recharging of the battery then occurs when the lithium ions move back from the cathode to the anode.
For some time, scientists have tried to eliminate the anode component in battery energy storage systems. Rather than using the anode, they instead insert a metal current collector where the metal ions can form and generate a charge. The problem, however, has been that the metal ions formed often have irregularities called dendrites. These dendrites cause batteries to short circuit or have limited life-spans. This has been especially true for zinc and sodium batteries in the lab. Until now, no one had figured out how to prevent these irregularities from forming.
“In our discovery, there are no dendrites, no finger-like structures. This kind of growth mode has never been observed for this kind of alkali metal.” – Bingyuan Ma, Doctoral Student, Department of Energy, Environmental & Chemical Engineering, McKelvey School of Engineering
Breakthroughs with Anode-Free Zinc and Sodium Batteries
Some notable breakthroughs have recently taken place in terms of anode-free batter energy storage systems. Researchers at the University of Washington in St. Louis made a notable discovery concerning anode-free sodium batteries. Previously, it had been thought that dendrite formation with sodium batteries were inevitable. But they found that reducing the water content in the electrolyte solution prevented these from forming. As a result, they were able to create anode-free sodium batteries that functioned as well as lithium batteries. Not only are these sodium batteries lighter, smaller, and durable, but they are much cheaper. Plus, sodium is readily available, especially when compared to lithium.
In other research labs, similar discoveries have been made concerning anode-free zinc batteries. These batteries, like sodium batteries, have been previously challenging to make because of dendrite formation as well. But scientists at Stanford University have been successful by providing a carbon nano-technologies to coat the materials collecting current. In doing so, zinc metal ions form without irregularities, and the battery energy storage system operates at 62.5% efficiency. They are now exploring changes that could increase this to as high as 95% efficiency. zinc is also readily available, which makes it another attractive alternative to lithium batteries as well.
“The disposable alkaline batteries used in many everyday electronics are based on zinc, but researchers are making real progress in making these systems rechargeable.” – Marshall A. Schroeder, Materials Engineer, US Army Combat Capabilities Development Command Army Research Laboratory
No Anode Looks to Be the Best Anode
The benefits to anode-free battery energy storage stems from several features. Without an anode, batteries will be more compact and smaller, requiring less space. This means devices could become even smaller and more mobile. In addition, anode-free zinc and sodium batteries are much less costly to make. In part, this is because both materials are in abundance. As more devices and items become dependent on battery energy storage, this will be important. Relying on lithium for a growing dependence on electric energy is concerning from a sustainability perspective. This is why both rechargeable zinc and sodium batteries could be the key to our future energy needs.
While lithium batteries remain the best option for battery energy storage presently, it’s likely this will change in the years to come. Anode-free batteries make logical sense, especially given their advantages. If zinc and sodium batteries can be made to be rechargeable, their other features will make them much more attractive. And with several research labs making tremendous progress in these areas, this shift will likely occur sooner rather than later. For the moment, it looks like anode-free batteries will indeed be the next big thing in sustainable energy solutions.
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