Compact 3D Metal Collectors Enabled by Roll‐to‐Roll Nanoimprinting for Improving Capacitive Energy Storage

Abstract

Reducing the contact resistance between active materials and current collectors is of engineering importance for improving capacitive energy storage. 3D current collectors have shown extraordinary promise for reducing the contact resistance, however, there is a major obstacle of being bulky or inefficient fabrication before they become viable in practice. Here a roll‐to‐roll nanoimprinting method is demonstrated to deform flat aluminum foils into 3D current collectors with hierarchical microstructures by combining soft matter‐enhanced plastic deformation and template‐confined local surface nanocracks. The generated 3D current collectors are inserted by and interlocked with active electrode materials such as activated carbon, decreasing the contact resistance by at least one order of magnitude and quadrupling the specific capacitance at high current density of 30 A g–1 for commercial‐level mass loading of 5 mg cm–2. The 3D current collectors are so compact that they have a low volume percentage of 7.8% in the entire electrode film, resulting in energy and power density of 29.1 Wh L–1 and 12.8 kW L–1, respectively, for stack cells in organic electrolyte. Furthermore, roll‐to‐roll nanoimprinting of metal microstructures is low‐cost, high‐throughput, and can be extended to other systems that involve the microstructured metal interface, such as batteries and thermal management.

Bubble Up Induced Graphene Microspheres for Engineering Capacitive Energy Storage

“…However, the fabrication process of these graphene films requires the use of large amounts of chemicals, and it is thus inferior to the bubble‐based method proposed here. The energy density for at stack level device is more than tenfold higher than commercial supercapacitors (5–8 Wh L −1 ), [ 16,38 ] even approaches the value for typical lead‐acid batteries (50–90 Wh L −1 ), [ 8,16 ] although with two orders of magnitude higher power density (15.8 kW L −1 ), highlighting its great potential for practical capacitive energy storage applications. For the stack cells using electrode films with an areal mass loading of 5 mg cm −2 , their power density can be further increased up to 23.4 kW L −1 with considerable energy density of 73.5 Wh L −1 , promising the high‐energy and power‐density capacitive energy storage for a broad range of applications.…”

“…The deformation of 3D contact interfaces by microimprinting was detailed in the previous work. [ 38 ] Different graphene films were also pressed onto a nickel foam (thickness ≈500 µm, Kunshan guangjiayuan New Material Co., Ltd) as the current collector for being tested in an aqueous electrolyte. The electrode films were punched into circular pieces with a diameter of 12 mm.…”

Continuous roller nanoimprinting: next generation lithography

“…In recent years, researchers have been exploring the use of novel materials such as graphene, 63 carbon nanotubes (CNTs), 64 diamond-like carbon (DLC), 65 and amorphous carbon (a-C) for producing protective coatings for imprint rollers. 66 Graphene and CNT rollers have improved durability, wear resistance, and anti-sticking properties.…”

“…49 As PDMS is highly deformable, the feature size on the soft mold is adjustable through low-cost and straightforward shrinkage technology, significantly lowering the cost of repetitive mold production. 50 In recent years, researchers have been exploring the use of novel materials such as graphene, 63 carbon nanotubes (CNTs), 64 diamond-like carbon (DLC), 65 and amorphous carbon (a-C) for producing protective coatings for imprint rollers. 66 Graphene and CNT rollers have improved durability, wear resistance, and anti-sticking properties.…”

“…Apart from bubbles caused by incomplete filling, other factors can also affect the quality of the final structure, such as contamination, temperature and pressure fluctuations, roller deformation, and uneven surface roughness. 64,114 Thus, it is necessary to ensure a clean and temperature-controlled environment and employ a pneumatic or hydraulic system to provide consistent pressure. 115 It also is helpful to perform tests and inspections on the roller and substrate regularly, ensuring that the pressure is evenly distributed across the substrate and the surface roughness of the substrate is uniform before imprinting.…”