A study from the Department of Metallurgical and Materials Engineering, Universitas Indonesia, has successfully demonstrated that the addition of zinc oxide in the form of nanorods (ZnO nanorods) into lithium-ion battery anode materials can significantly improve battery durability. The research, led by Dr. drg. Bambang Priyono, S.U., together with a team of researchers from Universitas Indonesia and the Indonesian Institute of Sciences (LIPI), was presented at the international conference i-TREC 2018. The findings are straightforward yet significant: a ZnO composition of 4 wt% was found to be the most optimal, producing a capacity of 150.8 mAh/g while maintaining performance under high charge-discharge rates of up to 20C.
A Long-Standing Problem in Modern Batteries
Lithium-ion batteries are now found everywhere. From smartphones and laptops to electric vehicles, nearly all modern devices rely on this technology. However, behind their widespread use lies a fundamental challenge that continues to concern engineers: conventional graphite-based anode materials are prone to degradation, especially when batteries are charged rapidly or operated under extreme conditions.
One promising alternative candidate is lithium titanate, or Li₄Ti₅O₁₂, commonly known as LTO. This material offers excellent stability during charging and discharging processes and has a long cycle life. The challenge is that LTO has low electronic conductivity. In other words, electrons cannot move easily through the material, limiting battery performance at high operating rates.
This is where ZnO nanorods provide a potential solution.
Synthesizing Materials in the Laboratory
The research team synthesized ZnO nanorods by mixing zinc nitrate tetrahydrate and hexamethylenetetramine (HMTA) in cold water, followed by heating at 90°C for three hours. The result was a nanoscale rod-shaped structure, significantly smaller than the width of a human hair.
These ZnO nanorods were then incorporated into the LTO synthesis process using a sol-gel solid-state method. The process involved multiple stages, beginning with TiO₂ gel formation, calcination at 300°C, and sintering at 750°C for three hours to produce the desired spinel LTO phase. Three ZnO compositions were tested: 4, 7, and 10 wt%.
Characterization using X-ray Diffraction (XRD) confirmed that ZnO successfully entered the LTO structure across all variations. SEM-EDS analysis showed that ZnO was evenly distributed throughout the material, although particle sizes were not yet completely uniform due to an incomplete grinding process.
Four Percent: The Optimal Number
Among the three tested variations, LTO/ZnO 4% demonstrated the best performance in nearly all evaluations.
Electrochemical Impedance Spectroscopy (EIS) testing showed that LTO/ZnO 4% had the lowest charge-transfer resistance (Rct), measuring 76.05 Ω, compared with LTO/ZnO 7% at 87.94 Ω and LTO/ZnO 10% at 83.85 Ω. Lower resistance means electrons can move more easily, allowing the battery to operate more efficiently.
Charge-discharge testing showed similar results. LTO/ZnO 4% was able to maintain its capacity even at a 20C rate, something that could not be achieved by the 7% and 10% variations. This finding is important for electric vehicle applications, which require rapid charging without sacrificing battery lifespan.
“ZnO nanorod content added to the sample can improve the rate charge and discharge capability but with proper amount without harming the reaction kinetics.”
In contrast, increasing ZnO content actually reduced the battery’s specific capacity. LTO/ZnO 7% produced only 134.1 mAh/g, while LTO/ZnO 10% decreased further to 118.3 mAh/g. This indicates that excessive ZnO addition disrupts chemical reactions inside the battery rather than improving performance.
Beyond Numbers in a Research Paper
This research may appear distant from everyday life. However, its impact could be highly significant. Batteries that last longer and can be recharged quickly are essential for accelerating electric vehicle adoption, which could reduce dependence on fossil fuels and help lower carbon emissions.
Indeed, the highest capacity achieved in this study, 150.8 mAh/g, remains below the theoretical capacity of pure LTO at 175 mAh/g.The addition of ZnO reduced the capacity by approximately 13.6% compared with the theoretical value. However, this trade-off was considered worthwhile because it provided improved durability and high-rate operating capability.
This research represents only one step forward. Challenges remain regarding particle size uniformity, production scalability, and further optimization.Nevertheless, the direction is clear: future anode materials do not necessarily need to achieve maximum capacity alone, as long as they are sufficiently durable to deliver long-lasting performance.
Authors: Achmad Zam Zam Aghasy, DDS, M.Kes.; Hazra Alifia Muharam
Photo: Freepik
Source DOI: https://doi.org/10.1051/e3sconf/20186703028