Imagine charging an electric vehicle in just five minutes. This is not merely a futuristic dream, but a target currently being pursued by battery material researchers worldwide. At the Department of Metallurgical and Materials Engineering, Universitas Indonesia, Dr. drg. Bambang Priyono, S.U., and his research team have published a promising discovery: a new lithium titanate-based anode material combined with tin and activated carbon that can exceed the theoretical capacity of conventional materials by 54%.\nThe research, published in the International Journal of Technology in 2019, offers a potential solution to one of the biggest obstacles to electric vehicle adoption: long charging times.<\/p>\n\n\n\n
Lithium-ion batteries are now everywhere. From mobile phones to electric vehicles, this technology has become the backbone of modern portable devices. However, one major weakness remains difficult to overcome: conventional graphite-based anode materials have limited lithiation potential, are vulnerable to solvents, and are not ideal for high-power applications.<\/p>\n\n\n\n
Lithium titanate, or Li\u2084Ti\u2085O\u2081\u2082 (LTO), is widely recognized as a promising alternative to graphite. This material has excellent safety characteristics, does not expand during charging (known as a zero-strain insertion material), and can operate under high-power conditions.\nThe challenge is that the theoretical specific capacity of LTO is only 175 mAh\/g, far below graphite\u2019s 372 mAh\/g. Its electrical conductivity is also extremely low, approximately 10\u207b\u00b9\u00b3 S\/cm. In short, LTO is safe but lacks sufficient power capability.<\/p>\n\n\n\n
The solution proposed by the research team was to combine LTO with tin (Sn) powder and activated carbon, creating new composites known as LTO\/Sn and LTO\/Sn@C.<\/p>\n\n\n\n
The synthesis process began with a sol-gel method to produce TiO\u2082 xerogel, which was then mixed with LiOH and sintered at 750\u00b0C under an argon atmosphere. The process produced pure LTO powder, which was subsequently combined with tin powder through a ball-milling process.\nFor the LTO\/Sn@C composite, activated carbon was added during the initial xerogel preparation stage to achieve a more uniform distribution.<\/p>\n\n\n\n
The researchers tested six sample variations: three tin concentrations (5, 7.5, and 12.5 wt%) without carbon, and three activated carbon concentrations (5, 15, and 25 wt%) with a fixed tin content of 7.5 wt%.<\/p>\n\n\n\n
Comprehensive characterization was conducted using X-ray diffraction (XRD) to identify phase structures, scanning electron microscopy (SEM) to analyze particle morphology, BET surface area measurements, and electrochemical tests including electrochemical impedance spectroscopy (EIS), cyclic voltammetry (CV), and charge-discharge testing.<\/p>\n\n\n\n
One interesting finding from the XRD analysis was the role of activated carbon in stabilizing the anatase phase of TiO\u2082. Without carbon, anatase TiO\u2082 transformed into rutile after sintering at 750\u00b0C. With carbon addition, the anatase phase remained stable.\nThis finding was not merely a structural observation, as phase stability directly affects the electrochemical performance of the material.<\/p>\n\n\n\n
The test results demonstrated a significant increase in capacity. The LTO\/Sn composite containing 12.5 wt% tin achieved a discharge capacity of 269.3 mAh\/g.\nMeanwhile, the LTO\/Sn@C composite containing 7.5 wt% tin and 5 wt% activated carbon (sample LSC-5) achieved the highest capacity, reaching 270.2 mAh\/g. This value exceeded the theoretical capacity of pure LTO by 54%.<\/p>\n\n\n\n
The addition of activated carbon was proven to significantly reduce particle size, from an average of 1.267 micrometers in carbon-free LTO\/Sn samples to 0.140 micrometers in samples containing 25 wt% carbon.\nSmaller particles shorten the diffusion distance for lithium ions, allowing faster charging and discharging processes.<\/p>\n\n\n\n
However, this improvement came with a trade-off. The addition of activated carbon unexpectedly increased charge-transfer resistance (Rct) rather than reducing it. The Rct value of the LSC-5 sample reached 158.72 \u03a9, significantly higher than that of the carbon-free LTO\/Sn sample.\nThe researchers suggested that this was related to the microporous structure of activated carbon, which may increase bulk resistance. Activated carbon contributes to capacity improvement through increased surface area and better particle distribution rather than through enhanced electrical conductivity.<\/p>\n\n\n\n