Univ. of Illinois team develops high-power Li-ion microbatteries that can out-power supercapacitors while retaining comparable energy density
20 April 2013
Researchers at the University of Illinois at Urbana-Champaign have demonstrated a high-power and high-energy density microbattery constructed from interdigitated three-dimensional (3D) bicontinuous nanoporous electrodes. The new microbatteries out-power supercapacitors while retaining comparable energy density. The researchers published their results in Nature Communications.
The lithium-ion microbatteries show power densities up to 7.4 mW cm-2 µm-1, which equals or exceeds that of the best supercapacitors, and which is 2,000 times higher than that of other microbatteries, the researchers said. The microbatteries show energy densities of up to and energy densities up to 15 mW h cm-2 mm-1. The battery microarchitecture affords trade-offs between power and energy density that result in a high-performance power source, and which is scalable to larger areas.
The performance of power sources is typically measured by power and energy stored per unit mass or unit volume. For conventional lithium ion batteries, typical volumetric energy and power densities are around 10–60 mW h cm-2 mm-1 and 1–100 mW cm-2 mm-1. It is possible to achieve higher power density, up to 1,000 mW cm-2 mm-1, by using porous battery electrodes that reduce ion diffusion through the active anode and cathode materials, as well as designs that reduce ion diffusion time in the electrolyte and decrease electrical resistance in the electrodes. Most publications on high-power batteries focus on either anode or cathode half cells, and show improved power density at the expense of energy density. In principle, a battery architecture based on 3D integrated porous microelectrodes could achieve high-power density without sacrificing energy density by combining small ion diffusion distances, large percentage of active material and highly conductive electrodes. Such a microarchitecture could also enable miniature batteries suitable for microelectronics integration.
...It has proven difficult for batteries of any size to achieve the high power of a supercapacitor, which can be fabricated at nearly any size and have power density larger than 4.0 mW cm-2 mm-1. It is challenging to integrate 3D electrodes into a complete microbattery cell, owing to the difficulty of integrating 3D elements of anode and cathode materials, along with the need to control materials uniformity and feature sizes across a range of length scales of 10 nm–1 mm.—Pikul et al.
Building on a novel fast-charging cathode design by materials science and engineering professor Paul Braun’s group, William King’s team developed a matching anode and then developed a new way to integrate the two components at the microscale.
The electrodes are a thin layer of nickel–tin (anode) or lithiated manganese oxide (LMO) (cathode) conformally coated onto interdigitated highly porous metallic scaffolds. The microarchitecture provides short electron and ion transport lengths in the electrolytically active material and electrolyte (yielding high-power density) while maintaining a high volume of active material (yielding high-energy density). The active material thickness varies between 17 and 90 nm.
The architecture allows compact integration of the anode and cathode on a single substrate for microelectronics applications.
The batteries could be further improved by taller 3D electrodes, which would require improvements in the fabrication process. Additional research could explore the fundamentals of ion transport in this type of 3D battery, explore other battery chemistries and routes to microelectronics packaging, the authors suggested.
The National Science Foundation and the Air Force Office of Scientific Research supported this work. King also is affiliated with the Beckman Institute for Advanced Science and Technology; the Frederick Seitz Materials Research Laboratory; the Micro and Nanotechnology Laboratory; and the department of electrical and computer engineering at the University of Illinois.
James H. Pikul, Hui Gang Zhang, Jiung Cho, Paul V. Braun & William P. King (2013) High-power lithium ion microbatteries from interdigitated three-dimensional bicontinuous nanoporous electrodes. Nature Communications 4, Article number: 1732 doi: 10.1038/ncomms2747
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