Global warming is largely driven by the release of greenhouse gas emissions through the burning of fossil fuels for various human activities, such as electricity, heat, and transportation. Among these, transportation contributed up to approximately 27% of the total CO2 emissions in the United States according to the Environmental Protection Agency in 2020. As the most promising candidates to replace fossil fuel-powered transportation, electric vehicles (EVs) have been playing an increasingly important role in sustainable transportation over the past decade. Due to the blooming of the EV market, current lithium-ion batteries (LIBs) are facing great challenges as their physiochemical limits in gravimetric and volumetric capacities fall short of meeting the high energy and power demands in modern EVs.
Increasing the battery electrode thickness, and thus raising the active material (AM) ratio at the cell level, is one plausible strategy to further augment the energy density of current LIBs. However, the tortuous and prolonged charge transport distances considerably restrict the utilization of the AM within a short charging or discharging time. Furthermore, suffering from poor electrode mechanical strength, conventional electrodes prepared by the tape-casting method typically show a low critical cracking thickness (<300 μm), with an areal capacity limit of ~10mAh cm−2. The overpotential of the battery electrodes also rises with the increase of electrode thickness or charging rate, resulting in degradation of active particles and battery failure after extended cycling.
Various advanced electrode architectures have been developed to facilitate the charge transport kinetics in thick electrodes over the past few years. Among them, decreasing electrode tortuosity is considered the most promising approach as it could facilitate the lithium-ion transport kinetics via controlling the spatial pore distribution while maintaining the pore volume in the porous electrodes. However, these low-tortuosity architectures often have a high porosity due to the intrinsic limitation of the electrode preparation methods, and the practical volumetric energy/power density of the architected electrodes is even much lower than the conventional electrodes.
The technology described involves the development of densified vertically lamellar electrode architectures for lithium-ion batteries (LIBs) aimed at enhancing energy storage efficiency. This approach utilizes a combination of bidirectional freeze-casting and compression-induced densification to create thick battery electrodes with vertically aligned channels. These channels facilitate lithium-ion transport, reducing the tortuous pathways typically found in conventional electrodes. The result is a significant improvement in both energy density and power density, with the technology demonstrating high areal capacity and stable cyclability. The method is versatile, applicable to various electrochemically active materials, and shows promise for large-scale electrode fabrication.
What differentiates this technology is its ability to overcome the limitations of traditional thick electrodes, which often suffer from poor charge transport due to elongated pathways. By creating vertically aligned channels with reduced tortuosity lithium-ion flux is enhanced, enabling efficient ion transport even in low-porosity electrodes. This design ensures that the active material is utilized more effectively, leading to higher energy and power densities.
Additionally, the methodology is scalable and adaptable to different materials, making it a robust solution for next-generation high-energy storage systems. The combination of improved electrochemical properties and potential for large-scale application sets this technology apart from existing solutions.