Skip to Content
Find More Like This
Return to Search

High Performance Binderless Electrodes for Rechargeable Lithium Batteries

National Renewable Energy Laboratory

Contact NREL About This Technology

Technology Marketing Summary

Portable electronic applications including cell phones, laptop computers, as well as electric vehicles or hybrid electric vehicles require dependable rechargeable batteries.  The lithium ion (Li-ion) battery is the preferred source for portable energy storage due to its desirable energy to weight ratio. The materials used in the development of anodes, cathodes and electrolytes are directly responsible for the performance characteristics of Li-ion batteries.  In order to meet ever-increasing demands: durability, utilization of “green” materials, cost and energy density (especially at high charge/discharge rates) etc. the materials and architectures of these batteries must be constantly upgraded through seminal research.  Perhaps most importantly, current Li-ion battery technologies are plagued by low reversible capacity and short cycle life, especially at high rates. Scientists at the National Renewable Energy Laboratory (NREL) have utilized the unique properties of highly crystalline and long carbon single-walled nanotubes (SWNTs) in a simple process to create Li-ion batteries that exhibit high reversible capacity with a simultaneously high durable rate capability.

Description

Currently, most conventional electrodes are comprised of active material (that stores Li+) that is directly mixed with carbon and polymer additives to help maintain electrical conductivity as well as mechanical integrity.  Typical loading of the active material is ~70-80 wt.%.  Unfortunately, when cycled at high rate, the inherent properties and characteristics of the active materials can lead to large volume expansion or insufficient electronic conductivity, which then results in mechanical degradation of the electrode and/or low capacity especially at high rates. Employing nanoparticles to improve rate capability is important due to a shorter diffusion path.  However, in order to achieve a high capacity and high rate battery using nanoparticles mixed with carbon materials there are three main issues that must be addressed. First, the size of the nanoparticles must be optimized such that rapid Li-ion diffusion and reaction with the nanoparticles is achieved. Second, an optimized carbon matrix must be developed that ensures both electrical conductivity and good thermal conductivity to improve heat dissipation. Finally, the conductive additive must maintain a flexible and strong matrix that accommodates large volume changes and maintains electronic conductivity.

NREL scientists have employed the unique properties of SWNTs to simultaneously address these issues as exemplified by a simple two step process to synthesize Fe3O4 nanoparticles embedded uniformly in an interconnected “SWNT net.”  One of the key advantages of this technique is that no binder material is necessary to maintain mechanical integrity, allowing for 95% active material in the electrode.  Most importantly, these binder-free electrodes have demonstrated a high reversible capacity of 1000 mAh/g at C rate (charge/discharge in one hour), as well as high rate capability and stable capacities of 800 mAh/g at 5C (charge/discharge in 12 minutes) and 600 mAh/g at 10 C (charge/discharge in 6 minutes).  The same approach has also been applied to a cathode material, LiNi0.4Mn0.4Co0.2O2, , enabling 130 mAh/g and 120mAh/g to be achieved for 5C and 10C rate, respectively. When cycled against lithium metal, after 500 cycles, the cathode only loses 8% and 9% of its initial capacity for 5C and 10C rate, respectively. The small degradation at this high rate is most likely due to degradation of the lithium metal rather than the novel cathode. Full cell devices have been fabricated (using a simple and nonoptimized graphite anode) showing the same performance characteristics as the half-cells (described above where lithium metal is the counter electrode). 

Benefits
  • Durability from flexible and conductive SWNT net
  • High reversible capacity
  • Durable high rate capability
  • Nontoxic and abundant materials
  • Has been demonstrated to improve both cathode and anode materials
Applications and Industries
  • Hybrid electric vehicles
  • Plug-in electric vehicles
  • Power tools
  • Laptop computers
  • Cellular telephones
  • Portable media
  • Pacemaker batteries
Patents and Patent Applications
ID Number
Title and Abstract
Primary Lab
Date
Application 20110070495
Application
20110070495
METHOD OF FABRICATING ELECTRODES INCLUDING HIGH-CAPACITY, BINDER-FREE ANODES FOR LITHIUM-ION BATTERIES
An electrode (110) is provided that may be used in an electrochemical device (100) such as an energy storage/discharge device, e.g., a lithium-ion battery, or an electrochromic device, e.g., a smart window. Hydrothermal techniques and vacuum filtration methods were applied to fabricate the electrode (110). The electrode (110) includes an active portion (140) that is made up of electrochemically active nanoparticles, with one embodiment utilizing 3d-transition metal oxides to provide the electrochemical capacity of the electrode (110). The active material (140) may include other electrochemical materials, such as silicon, tin, lithium manganese oxide, and lithium iron phosphate. The electrode (110) also includes a matrix or net (170) of electrically conductive nanomaterial that acts to connect and/or bind the active nanoparticles (140) such that no binder material is required in the electrode (110), which allows more active materials (140) to be included to improve energy density and other desirable characteristics of the electrode. The matrix material (170) may take the form of carbon nanotubes, such as single-wall, double-wall, and/or multi-wall nanotubes, and be provided as about 2 to 30 percent weight of the electrode (110) with the rest being the active material (140).
National Renewable Energy Laboratory 09/23/2009
Filed
Technology Status
Technology IDDevelopment StageAvailabilityPublishedLast Updated
NREL ROI 09-41DevelopmentAvailable03/31/201103/31/2011

Contact NREL About This Technology

To: Erin Beaumont<Erin.Beaumont@nrel.gov>