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Inventions for Advancing Solid Oxide Fuel Cell Commercialization

IB-2189


The five new technologies described below, developed by Lutgard DeJonghe, Steven Visco, Craig Jacobson and their team from Berkeley Lab’s Materials Sciences Division, add to Berkeley Lab's existing robust patent portfolio in solid oxide fuel cells. These new inventions offer significant advances towards lowering operating temperatures and enabling rapid thermal cycling of solid oxide fuel cells. Rapid thermal cycling enables fuel cells to be turned on and off quickly, a necessity for mobile applications. All of the inventions have patents pending and are available for licensing or collaborative research opportunities.


Braze for Robust Seals with Ceramic (IB-2066)

Fuel Cell Housing for Rapid Start-Up Auxiliary Power and Gas Separation (IB-1942, IB-2189)
Durable Joining of Dissimilar Materials (IB-2065)
Single-step Infiltration for Improved Low Temperature Cathode Performance (IB-2107, IB-2574)
Robust, Multifunctional Joint for Large Scale Power Production Stacks (IB-2064)
Other Berkeley Lab Solid Oxide Fuel Cell Technologies




Braze for Robust Seals with Ceramic
IB-2066

APPLICATIONS:

  • High temperature seals for electrochemical devices, oxygen generators, and metal/ ceramic interfaces

ADVANTAGES:

  • Enables rapid thermal cycling
  • Overcomes brazing limitations without cost increases
           
     
  a) Existing technology cracks ceramic. b, c) Berkeley Lab braze/ceramic interface survives 700°C rapid thermal cycling.
           


ABSTRACT:

Berkeley Lab scientists have developed a composite braze material that can be used to manufacture strong, gas-tight joints where one of the joining members is ceramic – typically yttrium stabilized zirconium (YSZ). The braze composition can be controlled to reduce the stress due to mismatched thermal expansion between the ceramic and the braze. Joints made using the new braze were failure-free after rapid thermal cycling up to 700°C.

Ceramics typically have a thermal expansion coefficient lower than most braze metals or alloys, which can result in weakening or cracking in the braze or ceramic. Berkeley Lab scientists add particles with low or negative expansion coefficients to the braze to attain sufficient matching to prevent this. A component that reacts with the ceramic surface can also be added, eliminating the need to metallize the ceramic prior to brazing.

Ceramic adhesives, glass, brazes, and mica have all been used as sealants in electrochemical devices, but all have limitations that prevent commercialization. This invention eliminates these barriers without increasing costs.

STATUS:

  • Issued Patent ZL200580041105.0 available at www.wipo.int. Available for licensing or collaborative research.

REFERENCE NUMBER: IB-2066



Fuel Cell Housing for Rapid Start-Up Auxiliary Power and Gas Separation
IB-1942 (SECA-funded), IB-2189

APPLICATIONS:

     
   
  In tests of the new fuel cell stack design, Berkeley Lab scientists have attained 0.85 kW/l at 0.4 W/cm2 and project volumetric power density of >2 kW/l .  
  • Assembling planar SOFCs into stacks for power generation
  • Auxiliary power for autos and RV
  • Individualized oxygen production for use in homes or hospitals


ADVANTAGES:

  • Start-up temperatures reached in 3.5 minutes for 400 thermal cycles without failure
  • Survives the most extreme thermal shocks of any fuel cell to date
  • Tolerates large thermal gradients across the stack
  • Demonstrated peak power density of 0.45W/cm2 at 720°C
  • Enables the use of conventional fuel cell materials


ABSTRACT:

Berkeley Lab scientists have designed a fuel cell housing unit that enables rapid thermal cycling of planar SOFCs made of conventional fuel cell materials. The invention makes strides towards enabling the use of SOFCs for portable applications such as auxiliary automotive power or the use of related electrochemical gas separators for single-user oxygen production for health purposes.

The open circuit voltage of SOFCs employing the design remained stable after more than 400 cycles between room temperature and 700°C, demonstrating that the seals maintained excellent quality. The fuel cells also survived instantaneous heating rates of over 1200°C per minute without failure, by far the most extreme temperature history for a planar SOFC. The new design achieves a peak power density of 0.45W/cm2 at 720°C.

The cell holder consists of a stainless steel casing with window frames to accommodate SOFC membranes comprising the anode chamber. Fuel is fed through a gas inlet and undergoes oxidation at the anodes before exhausting out the gas outlet. This design uses efficient edge current collection.

STATUS:

  • IB-1942: Issued Patent # 7816055 available at www.uspto.gov.
  • Published Patent Applications: IB-2189, US-2008-0286630-A1 available at USPTO
  • Available for licensing or collaborative research.

REFERENCE NUMBERS: IB-1942 and 2189



Durable Joining of Dissimilar Materials
IB-2065

APPLICATIONS:

  • Metal/ceramic joints in SOFCs
  • Thermal barrier coatings
  • Metal/ceramic bonding


ADVANTAGES:

  • Survives rapid thermal cycling
  • Thinner than graded joint
  • Eliminates the need to introduce a third material into the joint
  • High strength over a wide range of joint porosities
  • Unlike graded joints, preserves contrast in material properties at the interface


ABSTRACT:

One barrier to solid oxide fuel cell manufacturing is forming robust joints between materials that don’t chemically bond with each other and/or differ greatly in form or particle size, such as metals and ceramics. Berkeley Lab scientists solve this problem by decorating the surface of the more ductile material with particles of the less ductile material via milling and then sinter-bonding this composite to the less ductile materials and/or another material that will sinter with either of the first two materials.

This technique is especially useful in devices where the utility of the joint is derived from a sharp interface between the two materials or where a third bonding material might be incompatible with system requirements. Joints made using this method have proven more durable during rapid thermal cycling than bonds relying on mechanical interlocking of articles or fibers and are more compact than graded joints.

STATUS:

REFERENCE NUMBERS: IB-2065



Single-step Infiltration for Improved Low Temperature Cathode Performance
IB-2107, IB-2574 (both SECA-funded)

APPLICATIONS:

   
  Berkeley Lab scientists sinter a porous YSZ layer onto an electrolyte and then use a new method to create a continuous monolayer of nanoscale LSM particles with high surface area inside the pores.  
     
  • Optimizing cathode or anode performance in SOFCs and oxygen generators/gas separators
  • Improving catalysts for hydrocarbon formation
  • Generating protective coatings for metals, polymers, and ceramics


ADVANTAGES:

  • One step instead of ten reduces processing costs
  • Creates a connected network of nanoscale particles with minimal reduction in gas flow
  • Lower infiltration sintering temperatures enable a wider choice of materials
  • At 650°C, cathode performance exceeds 350 mW per cm2


ABSTRACT:

Scientists at Berkeley Lab have invented a one-step method for infiltrating porous structures with a continuous, electronically conducting monolayer or several continuous monolayers using only 3-5 weight percent of ceramic. The technique enables high SOFC cathode performance at lower temperatures where less expensive and more pliable metals can replace ceramics for some cells parts.

In this method the porous structure is sintered separately from the coating, allowing the firing temperatures of each material to be optimized. If the coating is fired at lower temperatures, the result is desirably small particle sizes that provide a higher surface area for electrochemical reactions, without blocking gas flow through the ceramic pores. The fine scale of the coating particles also allows the use of materials whose thermal expansions aren’t well matched with each other, without the risk of cracking.

The technique was used to prepare a LSM-YSZ composite cathode for a SOFC. Operating at 650°C, the cathode performance exceeds 350 mW per cm2. The LSM particles are between 30 and 100 nm.


STATUS:

REFERENCE NUMBERS: IB-2107, IB-2574



Robust, Multifunctional Joint for Large Scale Power Production Stacks
IB-2064

APPLICATIONS:

     
 
DIAGRAM OF BERKELEY LAB'S MULTIFUNCTIONAL JOINT
 
   
     

Sealing/joining for:

  • electrochemical devices, especially metal supported tubular SOFC cells
  • electronic devices operating at elevated temperatures


ADVANTAGES:

  • Robust, gas-tight, and compact
  • Provides electrical management over a wide range of temperature
  • Promises to be inexpensive and easy to manufacture
  • Enables rapid thermal cycling and endures thermal shock


ABSTRACT:

Berkeley Lab scientists have developed a multifunctional joint for metal supported, tubular SOFCs that divides various joint functions so that materials and methods optimizing each function can be chosen without sacrificing space. The functions of the joint include joining neighboring fuel cells in series, sealing cells so that distinct atmospheres don’t interact, providing electrical connections between neighboring cells, and insulating electrodes in the same cell.

The design takes advantage of highly conductive metal cell supports and edge current collection to ensure efficient power production. Traditionally, the various functions performed by the Berkeley Lab joint require physical separation, which complicates the manufacturing process and produces a less robust cell. The new joint demonstrates excellent structural integrity and is expected to be inexpensive and easy to manufacture. Novel Berkeley Lab brazing techniques make the innovative design possible. (See “Braze for Robust Seals with Ceramic”, IB-2066, above.)

STATUS:

REFERENCE NUMBERS: IB-2064

 

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Last updated: 05/11/2012