Dendrite preventing separator for secondary lithium batteries

• US 5,427,872 A
• Filed: 11/17/1993
• Issued: 06/27/1995
• Est. Priority Date: 11/17/1993
• Status: Expired due to Fees

• Current Assignee: Department of Health and Human Services (State of Victoria)
• Original Assignee: United States Of America As Represented By The Administrator Of The National Aeronautics And Space Administration
• Inventors: Shen, David H., Huang, Chen-Kuo, Surampudi, Subbarao, Halpert, Gerald
• Primary Examiner(s): Kalafut, Stephen
• Assistant Examiner(s): NUZZOLILLO, MARIA
• Application Number:
  US08/154,322
• Time in Patent Office: 587 Days
• Field of Search: 429/142, 429/144, 429/248, 429/249, 429/218
• US Class Current: 429/142
• CPC Class Codes: H01M 10/05 Accumulators with non-aqueous electrolyte H01M10/39 takes precedence
• CPC Class Codes: H01M 10/42 Methods or arrangements for servicing or maintenance of secondary cells or secondary half-cells H01M10/60 takes precedence
• CPC Class Codes: H01M 2200/00 Safety devices for primary or secondary batteries
• CPC Class Codes: H01M 50/40 Separators; Membranes; Diaphragms; Spacing elements inside cells
• CPC Class Codes: H01M 50/497 Ionic conductivity
• CPC Class Codes: Y02E 60/10 Energy storage using batteries

Abstract

Dendrites are prevented from shorting a secondary lithium battery by use of a first porous separator such as porous polypropylene adjacent the lithium anode that is unreactive with lithium and a second porous fluoropolymer separator between the cathode and the first separator such as polytetrafluoroethylene that is reactive with lithium. As the tip of a lithium dendrite contacts the second separator, an exothermic reaction occurs locally between the lithium dendrite and the fluoropolymer separator. This results in the prevention of the dendrite propagation to the cathode.

Claims

1. A rechargeable battery comprising in combination an outer housing containing:

an anode containing a source of lithium metal ions;

an electrolyte comprising a solution of an ionized lithium salt in a solvent polar organic solvent;

a first porous separator formed of a synthetic organic aliphatic hydrocarbon resin that is non-reactive with lithium and lithium ions positioned adjacent a surface of the anode, said first separator being imbibed with said electrolyte;

a cathode comprising a composite layer of organic resin binder containing a dispersion of transition metal oxide or chalcogenide particles disposed on a metal current collector;

a second porous separator imbibed with said electrolyte disposed between said cathode and said first separator, said second separator consisting essentially of a porous thermoplastic polytetrafluoroethylene reactive with said lithium metal whereby when the tip of a lithium dendrite growing from said surface of the anode penetrates the first separator and contacts said second separator, the dendrite tip and reactive thermoplastic polytetrafluoroethylene forming said second separator react to form a non-porous plug of polytetrafluoroethylene preventing further growth of the dendrite.

2. A battery according to claim 1 in which the first separator comprises porous polypropylene.

3. A composite separator for limiting growth of lithium dendrites in a secondary lithium battery comprising:

a first layer of a porous hydrocarbon resin unreactive with lithium or lithium ions; and

a second layer adjacent said first layer of a porous thermoplastic polytetrafluoroethylene that exothermically reacts with the tip of a lithium dendrite to form a non-porous plug of polytetrafluoroethylene.

4. A separator according to claim 3 in which the first layer is formed of a porous polypropylene.