Researchers at the Beijing University of Technology claim that they had synthesized a series of phosphorus(P)-/tin (Sn)-based composites that serve as high-capacity and high-stability anode materials, enabling a sodium-ion battery with a capacity retention of 97.7% after 50 cycles.

The researchers said sodium-ion batteries would be a vital alternative to lithium-ion batteries due to the high abundance and low cost of sodium resources. High-capacity anode materials like phosphorus are known for their high theoretical capacities, low discharge voltages, and low costs. But they often suffer from large volume expansion, leading to problems like structural collapse and particle pulverization, declining performance rapidly. Therefore, they alloyed phosphorous with tin and constructed well-designed microstructures to buffer these issues.

The researchers used a low-cost one-step ball milling procedure to synthesize a series of phosphorus-/tin-based composites. They embedded and separated an optimal structure comprising crystalline nanodomains like tin phosphide (Sn4P3) and Sn in an amorphous phosphorus matrix. The new architecture hindered the aggregation of metallic tin-based particles and helped improve the conductivity of amorphous phosphorus, enhancing the efficiency of electrochemical reactions. With its small crystalline domain and amorphous nature, phosphorus enabled the material with high stability.

Due to highly disordered composite anode materials, the researchers also faced challenges in gaining structure information of diverse microstructures. However, they introduced pair distribution function methodology, which helped provide local structure information for complicated systems and quantify the components in ordered or even disordered materials. This helped them analyze the structure and proportion of SnPx crystalline domains.

In August 2021, researchers at Sandia National Laboratories designed a new class of molten sodium batteries for grid-scale energy storage. This new battery could operate at a much lower 230 degrees Fahrenheit than the commercially available molten sodium batteries, which typically operate at 520-660 degrees Fahrenheit.

Last year, researchers at the Washington State University and Pacific Northwest National Laboratory announced that they had developed a sodium-ion battery that could be made using cheap and widely available materials. They said these batteries work as well as commercially available lithium-ion batteries, adding that they offer similar performance and could retain over 80% of their charge even after 1,000 charge cycles.