A New Strategy for Maximizing the Storage Capacity of Lithium in Carbon Materials.

A novel strategy for maximizing the lithium storage capacity of carbon materials is reported. To redesign the interior structure, a large amount of Li, 4 wt%, is doped into the carbon during its synthesis. The Li-doped carbon is subsequently annealed, during which the diffusion of Li induces a disordered structure, thereby generating many nanocavities. The diffused Li atoms aggregate into a superdense state within the carbon structure; when the Li agglomerates escape from the carbon during the delithiation process, new void spaces are created at their location. Thus, the interior of carbon is evacuated to form a new structure capable of storing a large amount of Li, realizing a high reversible capacity during charging. At a rate of 1 C, the average reversible capacity of the material is three times higher than that of commercial graphite, with a stable cycling performance over 300 cycles. This is a remarkably improved Li storage performance for pure carbon, without the need for the silicon, tin, or transition metal oxide, that are becoming popular as next-generation materials. Therefore, this novel strategy can potentially aid in the design of high-performance materials via better carbon material design and combinations with other types of materials.

A lithium superionic conductor for millimeter-thick battery electrode.

No design rules have yet been established for producing solid electrolytes with a lithium-ion conductivity high enough to replace liquid electrolytes and expand the performance and battery configuration limits of current lithium ion batteries. Taking advantage of the properties of high-entropy materials, we have designed a highly ion-conductive solid electrolyte by increasing the compositional complexity of a known lithium superionic conductor to eliminate ion migration barriers while maintaining the structural framework for superionic conduction. The synthesized phase with a compositional complexity showed an improved ion conductivity. We showed that the highly conductive solid electrolyte enables charge and discharge of a thick lithium-ion battery cathode at room temperature and thus has potential to change conventional battery configurations.

Novel Approach Through the Harmonized Sulfur in Disordered Carbon Structure for High-Efficiency Sodium-Ion Exchange.

Sodium-ion batteries (SiBs) have recently attracted considerable interest due to the plentiful supply of raw materials for their production and their electrochemical behavior, which is similar to that of lithium-ion batteries (LiBs). However, the relatively larger radius of sodium ions than that of lithium ions is not suitable for storage in conventional graphite, which is widely used as the anode. To resolve this issue, in this study, we developed a new harmonized carbon material with a three-dimensional (3D) grapevine-like structure and a sulfur component using an efficient synthesis process. On the basis of these advantages, the harmonized sulfur-carbon material exhibited a highly reversible capacity of 146 mA h g-1 at an extremely high specific current of 100 A g-1 and long-term galvanostatic cycling stability at 10 and 100 A g-1 with superior electrochemical performance. Our results are anticipated to provide new insights into SiB anode materials that would advance their production.

In Situ Synthesis of Silicon-Carbon Composites and Application as Lithium-Ion Battery Anode Materials.

Silicon can be used in a variety of applications. Particularly, silicon particles are attracting increased attention as energy storage materials for lithium-ion batteries. However, silicon has a limited cycling performance owing to its peeling from the current collector and the volume expansion that occurs during alloying with lithium in the charging process. Significant contributors to this problem are the even distribution of silicon nanoparticles within the carbon matrix and their deep placement in the internal structure. In this study, we synthesized silicon nanoparticles and carbon materials via a bottom-up approach using a new method called plasma in solution. Silicon nanoparticles and the carbon matrix were synthesized in a structure similar to carbon black. It was confirmed that the silicon particles were evenly distributed in the carbon matrix. In addition, the evaluation of the electrochemical performance of the silicon-carbon matrix (Si-C) composite material showed that it exhibited stable cycling performance with high reversible capacity.