3D freestanding highly porous thin-graphite with hierarchical porosity for supercapacitor and Li battery

Physical Sciences : Materials and Compounds

Available for licensing

Inventors

  • Donglei Fan , Mechanical Engineering
  • Jing Ning , Mechanical Engineering
  • Xiaobin Xu , University of Texas at Austin

Background/unmet need

Carbonaceous materials with various morphologies and chemistries, such as carbon nanotubes, bucky balls, graphene, and thin graphite, have emerged as key structures for energy storage and conversion devices, such as electric double-layer supercapacitors and lithium batteries. Among them, thin graphite is advantageous as electrode supports owing to their high electric conductivity, excellent mechanical durability, and ultra-low mass density. However, it remains a grand challenge to efficiently synthesize carbonaceous materials into 3D porous nanosuperstructures, whose properties of high surface areas and high ionic mobility are directly related to energy density and charging/discharging speed of energy devices.

Intensive past research has demonstrated ultra-large specific surface area of graphene and its usage in energy devices. However, the assembly of graphene sheets is completely uncontrollable, which can drastically reduce available surface areas and thus lower the device performance. Recently, commercially available 3D nickel foams were employed as catalysts for synthesis of 3D thin graphite. Although this approach resolved the assembly problem of carbonaceous materials as electrodes for energy devices, the feature size of as-obtained graphite is at a large scale of 50 to 100 μm. Thus, an economical and robust manufacturing process achieving highly porous 3D carbonaceous nanostructures with multilevel organized porosity is highly desired for achieving performance improvements in the next generation energy devices.

Invention Description

A group in the Mechanical Engineering Department at UT Austin, led by Prof. Emma Fan, has reported an innovative approach for the synthesis of such superstructures from engineered catalysts and their applications in electrochemical supercapacitors. The 3D thin-graphite nanostructures with controlled porosity are highly porous, free-standing, and flexible. The manufacturing method is efficient, controllable, and cost-efficient, and can be readily adopted for manufacturing 3D porous graphene/graphite materials suitable for an array of energy storage and conversion devices.

The group applied the as-grown graphite as electrode support for nickel hydroxide [Ni(OH)2] supercapacitors, achieving an unprecedented specific capacitance of ∼3962 F/g and 1149 F/g at a current density of 1.5 A/g, based on the actual weight of Ni(OH)2 and total weight of the electrode, respectively. Compared to known technologies, such values are a few times higher. The supercapacitors also exhibit excellent durability with 97.5% capacitance retention after 4000 cycles.

Benefits/Advantages

  • Manufacturing method is highly efficient and controllable.
  • Overall production process is cost effective.
  • The resulting superstructure is highly porous, free-standing, and flexible.
  • When applied to actual supercapacitor electrode, the device achieves high specific capacitance and long charge/discharge cycling duration.

Features

  • The as-grown graphite superstructure is 3D, highly porous, freestanding, and flexible with multilevel pore sizes
  • The manufacturing process uses metal substrate as both template and catalyst for forming the 3D porous structure.

Market potential/applications

Energy storage and conversion devices used in personal electronics, auto, utility, and residential applications

Development Stage

Lab/bench prototype

IP Status

  • 1 U.S. patent application filed
  • 1 U.S. patent issued: 9,957,163