A rapid condensation process creates uniform porous oxides with conductive nanomaterials, boosting lithium storage performance while enabling full solvent recovery and sustainable material production.
(Nanowerk Spotlight) Advances in energy storage depend on materials that move both ions and electrons efficiently. Lithium-ion batteries rely on electrodes that can store and release charge many times without structural damage. The performance of these electrodes often comes down to how evenly different components mix on the nanometer scale.
Metal oxides can store lithium well, but they conduct electrons poorly. Carbon-based materials and two-dimensional compounds such as MXenes can move electrons quickly, but their surfaces must stay accessible for ions. Combining these materials in a uniform, mesoporous structure has been a persistent goal.
Traditional manufacturing methods struggle to control nanoscale component distribution during fabrication. When solvents evaporate slowly, particles clump, pores collapse, and the final material loses the precise internal architecture that efficient electrodes require.
Researchers have tried various self-assembly techniques to address this issue. One of the most widely used methods is evaporation-induced self-assembly, where a solution containing a structure-directing polymer and metal precursors slowly dries to form an ordered mesoporous framework. Although it can create well-defined pore structures, the process is time-consuming and prone to uneven mixing.
Additives such as carbon nanotubes or MXenes tend to separate from the metal oxide as the solvent leaves, leading to patchy electrical networks and poor reproducibility. Many of these processes also depend on toxic solvents that are difficult to recycle at scale.
These challenges have limited the path from laboratory synthesis to large-scale battery component manufacturing. At the same time, developments in block copolymer templating, metal alkoxide chemistry, and conductive nanomaterials have provided the tools to attempt a more controlled, faster route. What remained unsolved was how to make all these ingredients assemble together in solution without relying on evaporation.
The study introduces a process called condensation-induced self-assembly, or CISA. Instead of letting solvent evaporation drive organization, CISA uses the chemistry of metal alkoxides to trigger rapid self-assembly within seconds. This shift removes the slow, unstable drying step that previously caused segregation. The approach makes it possible to uniformly integrate one-dimensional and two-dimensional conductive nanomaterials into mesoporous metal oxides while maintaining structural order and porosity.
“Our approach utilizes the condensation reaction of metal alkoxides as the driving force for self-assembly, enabling the formation of uniform mesoporous metal oxides within just a few seconds,” Jin Kon Kim, a professor at Pohang University of Science and Technology (POSTECH) and Director of the National Creativity Research Initiative Program for Smart Block Copolymers in Korea, who led the study, explains to Nanowerk. “In this recent work we introduce a new block copolymer self-assembly principle (CISA) as an alternative to the conventional evaporation-induced self-assembly (EISA).”
Homogeneous integration of 1D and 2D nanomaterials having high conductivity into mesoporous metal oxides via ultrafast condensation-induced self-assembly. (Image: Courtesy of the researchers)
At the center of the process is a block copolymer known as PS-b-PEO. This molecule has two parts: polystyrene, which avoids polar environments, and polyethylene oxide, which interacts with them. When dissolved in an acidic solvent, these two segments separate on the nanoscale, forming organized domains. Metal alkoxides such as niobium ethoxide act as precursors that hydrolyze and condense into metal oxide networks.
In the procedure developed by the POSTECH team, PS-b-PEO is dissolved in acetone adjusted to pH 1 with hydrochloric acid. When niobium alkoxide is added, it bonds with the polyethylene oxide segment and begins to form oxide chains. That reaction shifts the balance of the mixture, causing micelles—tiny clusters with a polymer core and inorganic shell—to appear. Within seconds, the solution becomes cloudy as these micelles aggregate and form a soft gel that later hardens into a porous composite.
Under highly acidic conditions, this entire transition finishes in about five seconds. Without the polymer, the same chemistry would take several times longer. This speed is critical because it locks all ingredients in place before they can separate.
The researchers examined how acidity and solvent type affect the reaction. At pH 1, condensation continues rapidly, leading to precipitation. At higher pH values, the system remains clear, showing that low pH is required to sustain the reaction. Solvent choice also matters.
Solvents with strong ability to form hydrogen bonds, such as dimethylformamide, slow the reaction because they stabilize the intermediate species. Acetone and dioxane allow faster condensation, but only acetone ensures irreversible formation of the oxide network because the early-stage oxide clusters are poorly soluble in it. That low solubility prevents the reaction from reversing and fixes the structure permanently.
Infrared spectroscopy confirms that the resulting material contains both polymer and oxide before calcination, and thermal data show that the polymer’s crystallinity disappears, indicating strong coordination during assembly.
After heat treatment to remove the polymer template, the process yields mesoporous metal oxides with uniform pore distributions. The study demonstrates the approach with niobium oxide, titanium dioxide, and tungsten oxide. These oxides develop distinct crystalline grains—approximately 16 nanometers for niobium oxide, 10 for titanium dioxide, and 5 for tungsten oxide—depending on the heating temperature used. Nitrogen adsorption measurements confirm that the materials exhibit the typical characteristics of mesoporous solids, with stable, ordered pore networks that are important for fast ion movement.
An important advantage of this process is solvent reusability. Because the reaction occurs entirely in acetone and produces a solid composite directly, the leftover liquid contains little contamination. The solvent can be recovered through simple distillation and filtration, then reused to make new samples with identical performance.
Kim describes this as “a sustainable and ultrafast self-assembly platform for nanomaterial synthesis,” noting that acetone allows 100% solvent recovery and reuse. This feature directly supports greener manufacturing practices and lowers the environmental impact of advanced material production.
The real test of CISA lies in whether it can distribute conductive nanomaterials uniformly throughout the oxide matrix. The researchers evaluated this by incorporating MXene sheets, specifically Ti₃C₂Tx, and carbon nanotubes.
MXenes are two-dimensional materials composed of metal carbides or nitrides that provide high electrical conductivity. In CISA, the polymer is first mixed with a stable dispersion of MXene in acidic acetone. When the metal alkoxide is added, micelles form rapidly and the MXene sheets become trapped within the growing polymer–oxide network. The resulting gel precipitates almost instantly.
After calcination, imaging shows that the MXene is evenly distributed within the mesoporous niobium oxide framework, with no large aggregates and preserved pore structure. The rapid chemical reaction prevents the sheets from stacking, which is a common problem during slow solvent evaporation.
To confirm the benefits of this speed, the team compared samples made with the new process to those prepared using evaporation-induced self-assembly. In the traditional method, the mixture must dry slowly over several hours, allowing the MXene or carbon nanotubes to migrate. The result is uneven distribution, collapsed pores, and reduced surface area. The evaporation sample showed only 39 square meters per gram of surface area, compared to 70 for the CISA sample. Uneven structure in the slower process explains the poorer electrochemical performance observed later.
The team tested their materials as lithium-ion battery anodes. Electrodes made from the CISA-produced niobium oxide–MXene composite showed higher capacity and stability compared to either component alone or to composites made by evaporation.
At low current, all samples performed similarly, but at high rates, differences became clear. The composite achieved 163 milliampere hours per gram at a current density of 1 ampere per gram, while pure mesoporous niobium oxide reached only 86 and pure MXene about 58.
The composite also retained 115 milliampere hours per gram after 1000 cycles, with nearly perfect charge–discharge efficiency. Measurements of charge transfer resistance confirmed faster electron flow in the composite. Ion diffusion coefficients calculated from impedance data indicate that the composite maintains efficient lithium transport through the mesoporous framework.
These results demonstrate that uniform mixing at the nanoscale can produce both high conductivity and strong structural stability, key traits for durable batteries.
“This chemistry is a significant paradigm shift in self-assembly research—from evaporation-driven to condensation-driven processes,” Kim points out. “This change directly addresses three persistent challenges in nanomaterial synthesis: uniformity, toxic solvent use, and time and energy efficiency.”
“CISA induces immediate reaction within the solution, ensuring uniform dispersion and homogeneous integration of all components, while completely eliminating hazardous solvents such as tetrahydrofuran, dimethylformamide, and dioxane,” he continues. “The full assembly finishes within just a few seconds, dramatically improving both energy efficiency and productivity.”
Looking ahead, Kim notes that future research will expand the approach: “Future research will focus on extending the CISA strategy to a broader range of metals and multicomponent oxide systems.” But he also highlights remaining challenges, such as developing conditions that work beyond strongly acidic environments and scaling the process for industrial production. “Our long-term vision is for condensation-induced self-assembly to become a new paradigm for synthesizing nanostructured materials not only for energy applications but also for catalysts, adsorbents, and biomaterials.”
The outcome is a versatile, rapid, and recyclable synthesis route that combines chemical precision with processing speed. The study shows that control over reaction kinetics can replace slow physical drying as the main driver of self-assembly.
The ability to integrate conductive additives uniformly without destroying pore structure offers clear benefits for lithium-ion storage and could extend to catalytic materials, sensors, and capacitors. Because the chemistry uses a simple, recyclable solvent and avoids toxic organics, it is compatible with scale-up. Demonstrating that uniform nanocomposite electrodes can form in seconds rather than hours shows how reaction-driven self-assembly could transform porous material manufacturing.
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