Researchers at the Nagoya Institute of Technology (NITech) in Japan have demonstrated that a specific material can act as an efficient battery component for sodium-ion batteries that will compete with lithium-ion batteries for several battery characteristics, especially speed of charge.

Lithium-ion batteries have several benefits: they are rechargeable and have a wide application spectrum. They are used in devices such as laptops and cell phones as well as in hybrid and fully electric cars.

The electric vehicle is an important player in the efforts to solve the energy and environmental crises. One downside to lithium is the fact that it is a limited resource. Not only is it expensive, but its annual output is (technically) limited (due to drying process). Given increased demand for battery-powered devices and particularly electric cars, the need to find an alternative to lithium - one that is both cheap as well as abundant - is becoming urgent.

Sodium-ion batteries are an attractive alternative to lithium-based ion batteries due to several reasons. Sodium is not a limited resource - it is abundant in the earth's crust as well as in seawater. Also, sodium-based components have a possibility to yield much faster charging time given the appropriate crystal structure design. However, sodium cannot be simply swapped with lithium used in the current battery materials, as it is a larger ion size and slightly different chemistry. Therefore, researchers are requested to find the best material for sodium ion battery among vast number of candidates by trial-and-error approach.

Scientists at NITech have found a rational and efficient way around this issue. After extracting about 4300 compounds from crystal structure database and following a high-throughput computation of said compounds, one of them yielded favourable results and was, therefore, a promising candidate as a sodium-ion battery component. The researchers identified that Na2V3O7 demonstrates desirable electrochemical performance as well as crystal and electronic structures. This compound shows fast charging performance, as it can be stably charged within 6 minutes. Besides, the researchers demonstrated that the compound leads to long battery life as well as a short charging time.

A high-throughput computation for Na migration energies is conducted for about 4,300 compounds in the inorganic crystal structure database, which the compound indeed exhibited excellent high-rate performance and cyclic durability; in detail, the compound exhibits stable 10C cycling, which corresponds to the rate of only six minutes for full charge/discharge, and ca. 94 percent capacity retention after 50 charge/discharge cycles at room temperature. These results are comparable with or outperform representative cathode materials for sodium ion batteries

The aim for this study was to tackle the biggest hurdle that large-scale batteries face in applications such as electric cars that heavily rely on long charge durations. The research team approached the issue via a search that would yield materials efficient enough to increase a battery's rate performance.

Despite the favourable characteristics and overall desired impact on sodium-ion batteries, the researchers found that Na2V3O7 underwent deterioration in the final charging stages, which limits the practical storage capacity to the half of theoretical one. As such, in their future experiments, the researchers aim to focus on improving the performance of this material so that it can remain stable throughout the entire duration of the charging stages.

By: DocMemory
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