New Battery Breakthrough: Rock Salt-polyanion Cathodes

New research has made an advancement in increasing the practical energy density of the battery.

Demand for batteries is on the rise worldwide, thanks to their increasing use in the automotive industry, the growing popularity of portable consumer electronics, and stringent environmental regulations. As a result, the global battery market is projected to reach $800 billion by 2036, up from about $120 billion in 2023.

In light of this expected growth, researchers are continuously developing and testing new materials and chemicals to improve critical parts of batteries, which affect properties such as energy output, energy storage, power capacity, and cycling capacity.

These components include a cathode (positive electrode), an anode (negative electrode), an electrolyte (for ion transportation between electrodes), and a separator.  

Most battery-powered devices today, such as EVs, smartphones, and energy storage systems, rely on lithium-ion battery technology. Lithium-ion batteries can store a huge amount of energy in compact sizes, charge fast, and last long.

However, with the growing demand for batteries with greater capabilities, new technologies are being researched and developed to improve efficiency, reduce cost, enhance safety, and promote sustainability.

Over the years, continuous research has led to advancements that offer promising alternatives to lithium-ion and lead-acid batteries. 

Sodium-ion batteries offer a more affordable and safer option that performs better at lower temperatures. These batteries are similar to lithium-ion batteries but utilize saltwater as an electrolyte, making them more suitable for energy storage, though they are yet to be optimized. Researchers are even using electrolyte gel to make nanowires more resilient and fit for battery use. 

Solid-state batteries, on the other hand, use a solid electrolyte such as glass, ceramic, or polymer instead of gel or liquid electrolyte. These batteries are far more efficient, weigh less, charge faster, and are already being used in smartphones and pacemakers. Toyota and BMW are currently working on launching solid-state battery-powered cars, though it will still take a few years.

New battery technologies further include lithium-sulfur batteries, which are cost-efficient but have a durability limitation, and cobalt-free lithium-ion batteries, which can help address human rights concerns in cobalt mining. However, alternatives like TAQ are still new and need more testing.

Zinc-based batteries are also being explored, with technologies including zinc-manganese dioxide, zinc-air, zinc-bromine, and zinc-ion batteries. However, they are inefficient, sometimes involve unexpected chemical conversion reactions, and are expensive to manufacture, requiring more research.

As the world increasingly relies on batteries, scientists globally are focused on achieving breakthroughs in storage times, power output, production costs, and instant readiness.

Latest Battery Breakthrough: Rock Salt-polyanion Cathodes 

New research has made an advancement in increasing the practical energy density of the battery. Published in Nature Energy late last month, the study titled “Integrated rocksalt–polyanion cathodes with excess lithium and stabilized cycling,” was conducted by the MIT Department of Nuclear Science and Engineering.

The study focuses on a new cathode material found in disordered rock salt, which has been studied as an advanced cathode material for use in lithium-ion batteries for over a decade. 

MIT researchers made sure that the material can create high-energy, low-cost storage for EVs, mobile phones, and renewable energy storage.

Led by Ju Li, the Tokyo Electric Power Company Professor in Nuclear Engineering, the team discovered DRXPS, or disordered rock salt-polyanionic spinel, as the new material.

This new category of partially disordered rock salt cathode, integrated with polyanions, is found to deliver high energy density at high voltages with enhanced cycling stability. This is a great achievement, given that there is typically a trade-off between energy density and cycling stability in cathode materials.

“With this work, we aim to push the envelope by designing new cathode chemistries.”

– Yimeng Huang, the paper’s first author, a postdoc at the NSE

Now, how is the new material family able to achieve both high energy density and good cycling stability? The answer lies in the integration of two key cathode materials — rock salt and polyanionic olivine. By combining them, it was able to get both of their benefits.

Another thing at play here is manganese (Mn), a hard, silvery metal found in abundance on Earth and much cheaper than other elements currently used in today’s cathodes. 

たとえば、マンガンはコバルト (Co) より約 30 分の 1、ニッケル (Ni) より 5 分の 1 安く、どちらも電池によく使用されます。さらに、マンガンはより高いエネルギー密度を達成する上で重要な役割を果たします。 

「（そのような）物質が地球上により多く存在することは、非常に大きな利点です。」

– Li、材料科学および工学教授

研究者らによれば、この利点は、再生可能エネルギーインフラを必要とするゼロカーボンの未来にとって非常に価値があるという。 

バッテリーは重要な役割を果たします

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