Protective membrane for electrochemical cells
Articles and methods involving protective membranes for electrochemical cells are generally provided. In some embodiments, a composite protective layer comprising particles and a polymeric binder may be disposed on an electroactive material. The particles may be reactive with lithium, may capable of intercalating lithium, and/or may comprise intercalated lithium. In some embodiments, the electroactive material may be in the form of a first electroactive layer, and a second electroactive layer may be disposed on the composite protective layer. Certain embodiments relate to activating a composite protective layer by intercalating lithium into particles within the layer and/or by reacting the particles with lithium metal.
1. An electrode, comprising:
a first electroactive layer comprising a first electroactive material, wherein the first electroactive material comprises lithium metal prior to charge and discharge cycles;
a composite protective layer adjacent the first electroactive layer, wherein the composite protective layer comprises a polymeric binder and particles dispersed in the polymeric binder, wherein the particles comprise boron particles, wherein the boron particles make up greater than or equal to 80 wt % of the composite protective layer, and wherein pores make up greater than or equal to 10 vol % of the composite protective layer; and
a second electroactive layer comprising a second electroactive material adjacent the composite protective layer and positioned at a side of the composite protective layer opposite the first electroactive layer, wherein the second electroactive material comprises lithium metal prior to charge and discharge cycles, and wherein the second electroactive layer has a thickness that is greater than or equal to 1% and less than or equal to 50% of the thickness of the first electroactive layer; and
an electrolyte adjacent the second electroactive layer, wherein the electrolyte is configured to permeate through at least a portion of the pores of the composite protective layer.
2. An electrode as in claim 1 , wherein the particles have an average diameter of less than or equal to 10 microns.
3. An electrode as in claim 1 , wherein the polymeric binder comprises a block copolymer or a styrene-butadiene rubber.
4. An electrochemical cell comprising the electrode as in claim 1 , wherein the polymeric binder is insoluble and/or non-swellable in the electrolyte.
5. An electrode as in claim 1 , wherein the composite protective layer comprises a thickening agent, a plasticizer, an additive, and/or silica.
6. An electrode as in claim 1 , wherein the composite protective layer comprises boehmite.
7. An electrode as in claim 1 , wherein the area specific impedance of the composite protective layer is less than or equal to 100 Ohm*cm 2 .
8. An electrode as in claim 1 , wherein the electronic conductivity of the composite protective layer is greater than or equal to 10 −6 S/cm.
9. An electrode as in claim 1 , wherein the composite protective layer is adjacent a support layer.
10. An electrode as in claim 1 , wherein the composite protective layer is adjacent a separator.
11. An electrode as in claim 1 , wherein the lithium metal in the first electroactive material and/or the second electroactive material is deposited from a vapor comprising lithium metal.
12. An electrode as in claim 1 , comprising a solid electrolyte interface formed upon exposure of the electrode to the electrolyte.
13. An electrode as in claim 1 , wherein lithium from the first electroactive layer intercalates into and/or reacts with the particles.
14. An electrode as in claim 1 , wherein lithium from the second electroactive layer intercalates into and/or reacts with the particles.
15. An electrode as in claim 1 , wherein one or more of the particles are in direct contact with the first electroactive material and/or the second electroactive material.
16. An electrode as in claim 1 , wherein at least a portion of the particles of the composite protective layer are randomly dispersed in the polymeric binder.
17. An electrode as in claim 1 , wherein the particles comprise intercalated lithium.
18. An electrode as in claim 1 , wherein the particles further comprise nanographite particles-comprising nanographite.
19. An electrode as in claim 1 , wherein the lithium from the second electroactive layer is configured to intercalate into and/or react with the particles in the composite protective layer to form an electrode structure including a single electroactive layer and a composite protective layer comprising lithium that originated from the second electroactive layer, and wherein the single electroactive layer is the first electroactive layer.
20. An electrode as in claim 1 , wherein the composite protective layer comprises pores that make up greater than or equal to 20 vol % of the composite protective layer.
21. An electrode as in claim 1 , wherein at least 50% of the pore volume is made of pores having a diameter of greater than or equal to 0.001 microns and less than or equal to 0.5 microns.
22. An electrode as in claim 1 , wherein at least 50% of the pore volume is made of pores having a diameter of greater than or equal to 0.001 microns and less than or equal to 0.1 microns.
23. An electrode as in claim 1 , wherein the lithium ion conductivity of the composite protective layer is less than or equal to 10 −7 S/cm prior to cycling.