Separator enclosures for electrodes and electrochemical cells
The disclosure provides electrochemical cells including a separator enclosure which encloses at least a portion of a positive or negative electrode. In an embodiment, the separator generates a contact force or pressure on at least a portion of the electrode which can improve the performance of the cell. The disclosure also provides methods for charging an electrochemical cell.
1. An electrochemical cell comprising:
a positive electrode;
a negative electrode;
one or more electrolytes positioned between said positive electrode and said negative electrode; wherein said one or more electrolytes are capable of conducting charge carriers; and
an electrically insulating and ionically conductive separator enclosure enclosing an entire surface of said positive electrode or said negative electrode that is not in physical contact with a current collector, wherein said separator enclosure generates a contact force, characterized by an average contact pressure selected from the range of 10 Pa to 10 MPa, on said entire surface of said positive electrode or said negative electrode during charging or discharging of said electrochemical cell; wherein said contact force is sufficient to prevent a substantial change in the electrode porosity or surface roughness of said positive electrode or said negative electrode enclosed by said separator enclosure during cycling of said electrochemical cell.
2. The electrochemical cell of claim 1 , wherein said contact force is sufficient to increase the cycle life of said electrochemical cell by a factor of at least 2.
3. The electrochemical cell of claim 1 , wherein said contact force is sufficient to prevent a substantial loss equal to or greater than 20% of active mass after each 500 full cycles or more of active material of said positive electrode or said negative electrode enclosed by said separator enclosure during cycling of said electrochemical cell.
4. The electrochemical cell of claim 1 , wherein said contact force is sufficient to limit the increase in surface roughness to less than or equal to 200% after 500 full cycles.
5. The electrochemical cell of claim 1 wherein the change in surface roughness per cycle is less than 0.2%, as averaged over 10 cycles.
6. The electrochemical cell of claim 1 , wherein said contact force is sufficient to limit the change in electrode porosity to less than or equal to 20% after each 500 full cycles or more.
7. The electrochemical cell of claim 1 , wherein said contact force is sufficient to limit the change in electrode porosity per cycle to less than 0.1%, as averaged over 10 cycles.
8. The electrochemical cell of claim 1 , wherein said contact force is generated by an elastic force of the separator enclosure provided in an expanded state, and varies as a function of the state of charge and state of health of the battery.
9. The electrochemical cell of claim 1 , wherein said separator enclosure entirely encloses said positive electrode or said negative electrode.
10. The electrochemical cell of claim 1 , wherein said enclosure separator is in physical contact with an active material of said positive electrode or said negative electrode enclosed by said separator enclosure or is in physical contact with an intermediate structure provided between an active material of positive electrode or said negative electrode and said enclosure separator.
11. The electrochemical cell of claim 1 , wherein said contact force is characterized by an average contact pressure selected from the range of 1 kPa and 100 kPa.
12. The electrochemical cell of claim 1 , wherein said enclosure separator comprises one or more perforated or porous layers each independently having a porosity greater than or equal to 30%.
13. The electrochemical cell of claim 1 , wherein said enclosure separator comprises one or more high mechanical strength layers.
14. The electrochemical cell of claim 1 wherein said enclosure separator comprises one or more low ionic resistance layers each independently having a JIS Gurley number less than or equal to 2000 seconds.
15. The electrochemical cell of claim 1 , wherein said enclosure separator comprises one or more layers independently comprising an elastomer.
16. The electrochemical cell of claim 1 , wherein said enclosure separator comprises a chemical barrier capable of preventing transport of one or more reaction products from said negative electrode or said positive electrode to said electrolyte.
17. The electrochemical cell of claim 1 , wherein said enclosure separator comprises a first high mechanical strength layer and a low ionic resistance layer.
18. The electrochemical cell of claim 1 , wherein said positive or negative electrode enclosed by said separator enclosure is a metal electrode.
19. The electrochemical cell of claim 1 , wherein said positive or negative electrode enclosed by said separator enclosure is a zinc electrode, lithium electrode, ZnO electrode, a silicon electrode, a germanium electrode, a sulfur electrode, an air electrode, a fluorinated electrode, or a carbonaceous electrode.
20. The electrochemical cell of claim 1 , wherein said positive electrode or said negative electrode enclosed by said separator enclosure is an intercalation electrode.
21. The electrochemical cell of claim 1 , wherein at least a portion of the porosity of one of the layers of the said separator enclosure of the said electrochemical cell is filled with a solid filler, wherein the solid filler comprises a polymer, ceramic or glass electrolyte.
22. An electrochemical cell comprising:
a positive electrode;
a negative electrode;
one or more electrolytes positioned between said positive electrode and said negative electrode; wherein said one or more electrolytes are capable of conducting charge carriers; and
an electrically insulating and ionically conductive separator enclosure enclosing an entire free surface of said positive electrode or said negative electrode, wherein said separator enclosure generates a contact force on the entire free surface of said positive electrode or said negative electrode; wherein said contact force is sufficient to prevent a substantial change in the electrode porosity or surface roughness of said positive electrode or said negative electrode enclosed by said separator enclosure during cycling of said electrochemical cell;
wherein said enclosure separator comprises a first layer having a plurality of apertures arranged in a first pattern and a second layer having a plurality of apertures arranged in a second pattern; wherein said second pattern has an off-set alignment relative to said first pattern such that an overlap of said apertures of said first layer and said apertures of said second layer along axes extending perpendicularly from said first layer to said second layer is less than or equal to 20%.