Researchers at Tokyo University of Science have taken another step in the ongoing quest to bring the next generation of sodium ion batteries to the market. They have achieved higher energy density in sodium ion batteries than in lithium ion batteries.
Lithium ion versus sodium ion
So far, lithium-ion batteries are number 1 among rechargeable batteries. Lithium-ion batteries prioritize energy density, allowing cars to travel farther, over long life or stability. In addition, they are competitively priced and have a fast charging time. But lithium, and other small and precious metals such as cobalt and copper, are not among the most abundant materials on Earth, and their increasing demand can lead to supply problems.
James Quinn, CEO of Faradion Ltd., a sodium ion battery developer in Sheffield, England, told Bloomberg in September:
Sodium is the sixth most abundant element on Earth, it is essentially unlimited, and it is sustainable. You harvest it – you don’t mine it that often.
Sodium ion batteries are emerging as a cheaper alternative. Several studies are underway in a number of countries on how sodium ion batteries can be made commercially viable.
The team’s sodium ion breakthrough
In a recent study published in Angewandte Chemie International Edition, The team revealed that they have found an energy efficient method to produce a new carbon-based material for sodium ion batteries with a very high sodium storage capacity.
The study focused on the synthesis of hard carbon, a highly porous material that serves as the negative electrode of rechargeable batteries, by using magnesium oxide (MgO) as an inorganic template of nano-sized pores in hard carbon.
The Tokyo University of Science release states:
The researchers explored a different technique to mix the ingredients of the MgO template to fine-tune the nanostructure of the resulting hard carbon electrode. After multiple experimental and theoretical analyzes, they have clarified the optimal manufacturing conditions and ingredients to produce hard carbon with a capacity of 478 mAh / g, the highest ever reported in this type of material.
The capacity of this newly developed hard carbon electrode material exceeds that of graphite (372 mAh / g), which is currently used as a negative electrode material in lithium-ion batteries.
Graphite doesn’t work in sodium ion batteries, and Faradion already uses a hard carbon anode, but this latest breakthrough makes the carbon even harder.
While a sodium ion battery with this hard carbon negative electrode would, in theory, operate with a 0.3 volt lower voltage differential than a standard lithium ion battery, the higher capacity of the former would lead to a much greater energy density by weight (1600 Wh / kg versus 1430 Wh / kg), resulting in a 19% increase in energy density.
Professor Shinichi Komaba of the research team said:
Our study proves that it is possible to realize high-energy sodium-ion batteries, invalidating the common belief that lithium-ion batteries have a higher energy density. The extremely high capacity hard carbon we developed has opened a door to the design of new sodium storage materials.
Further studies will be needed to verify that the proposed material actually offers superior life, input-output characteristics and low temperature operation in sodium ion batteries.
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