With the rapid growth in demand for lithium batteries in fields such as electric vehicles and large-scale energy storage systems (ESS), a research team in South Korea has developed a composite anode material made of hard carbon-tin suitable for both lithium and sodium batteries. This advancement aims to provide these batteries with advantages such as rapid charging, higher stable cycling of charge and discharge, as well as increased energy density, meeting the current global requirements for battery performance.
Currently, graphite is the most commonly used anode material in lithium-ion batteries (LIB) due to its stable structure. However, the actual capacity of a graphite electrode in batteries is lower than the theoretical value of 372mAh/g. Additionally, under harsh charging conditions such as low temperatures, the overall charging speed of graphite electrodes can significantly decrease.
Moreover, slow electrochemical reactions can lead to lithium ions being deposited on the graphite anode, causing electrode degradation and compromising battery integrity, resulting in serious safety hazards for most products currently using lithium batteries worldwide.
To overcome and improve the issues with traditional graphite anodes, a research team from the Pohang University of Science and Technology (POSTECH) and the Korea Institute of Energy Research (KIER) in South Korea collaborated to develop a novel composite anode material combining hard carbon and tin. This innovation aims to provide lithium and sodium batteries with rapid charging, increased cycling of charge and discharge, and enhanced battery energy density capabilities.
By replacing graphite with hard carbon, which is a disordered carbon material with abundant micropores and channels facilitating rapid diffusion of lithium and sodium ions, the new composite anode material aims to improve energy storage, increase mechanical strength, enhance battery lifespan, and boost charging rates.
The choice of tin metal was due to its ability to effectively alleviate the gradual expansion of the electrode material volume during battery cycling. However, researchers encountered a challenge when incorporating tin metal into the mix, as its low melting point (230°C) made it difficult to synthesize fine particles. Luckily, through the sol-gel process and thermal reduction at temperatures of 500°C, 700°C, and 900°C, tin particles of around 10 nanometers were successfully uniformly embedded in the hard carbon matrix material.
This hard carbon-tin composite anode material not only allows tin nanoparticles to become fully active but also serves as a catalyst for other metals within the hard carbon. The Sn-O bond plays a key role in promoting the oxidation-reduction reactions of tin with lithium and oxygen with lithium during the electrochemical cycling process, ultimately forming a lithium battery with high reversibility and conversion efficiency.
To test the effectiveness of this electrode in lithium batteries, researchers conducted cycling charge and discharge tests. Results showed that the hard carbon-tin electrode, heated to 700°C, exhibited optimal performance by enabling high current rapid charging of the lithium battery and maintaining stability even after 1,500 rapid charge and discharge cycles. Additionally, the volumetric energy density of this electrode was 1.5 times higher than that of traditional graphite electrodes.
Furthermore, the researchers applied this electrode to sodium batteries (SIB) for testing. The results indicated that the overall performance of sodium batteries was slightly lower than that of lithium batteries, primarily due to the electrochemical irreversibility of sodium oxide (Na2O) within sodium batteries. However, the overall performance still surpassed that of traditional sodium batteries.
This sodium battery test aimed to address and improve the issue of poor reactivity of sodium ions with traditional anode materials such as graphite and silicon.
The research results were published in the ACS Nano journal in March and received funding from the South Korean Ministry of Trade, Industry, and Energy, as well as the Ministry of Science and ICT. The researchers stated that this high-power, high-energy, durable hard carbon-tin electrode could be applied to various rechargeable battery platforms, demonstrating the potential for the next generation of lithium and sodium batteries.
Professor Soojin Park from Pohang University of Science and Technology expressed that this research represents a new milestone in the development of next-generation high-performance batteries with potential applications in electric vehicles, hybrid power systems, and large-scale energy storage systems.
Dr. Gyujin Song from the Korea Institute of Energy Research added that this type of anode achieves high power, stability, energy density, and is compatible with rechargeable sodium battery systems, bringing significant potential to the battery market.