US-12620620-B2 - Layered gel-polymer electrolytes and methods of forming thereof

Abstract

Provided are layered gel-polymer electrolytes and electrochemical cells comprising these electrolytes as well as methods of forming the electrolytes and the cells. A gel-polymer electrolyte comprises a support core and one or two interface layers on the core surface. The interface layers are relied on to conform to electrode surfaces with high surface roughness, while the support core prevents any physical penetration and electrical shorts through the gel-polymer electrolyte, e.g., by electrode protruding peaks. Specifically, the interface layer redistributes around these protruding peaks and forms a continuous interface with the electrode surface. When the stack is compressed, the gel-polymer electrolyte also releases some liquid electrolyte, which soaks the electrode and enhances ionic transfer within the electrode and through the electrolyte-electrode interface. The gel-polymer electrolyte is formed by coating interface layers on the support core and soaking this assembly in a liquid electrolyte.

Inventors

• Song Han
• Sa Zhou
• Xinghua Meng

Assignees

• GRU Energy Lab Inc.

Dates

Publication Date

20260505

Application Date

20230905

Claims (17)

1. 1 . A method of fabricating an electrochemical cell, the method comprising: dissolving one or more polymer materials in one or more solvents, thereby forming a polymer solution; coating the polymer solution onto a support core comprising a first surface and a second surface, opposite of the first surface, wherein: the polymer solution is coated on the first surface, thereby forming a first interface layer on the first surface of the support core, and the polymer solution is coated on the second surface, thereby forming a second interface layer on the second surface of the support core; introducing a liquid electrolyte into at least one of the support core, the first interface layer, and the second interface layer, thereby forming a layered gel-polymer electrolyte; and after introducing the liquid electrolyte, laminating a stack comprising a positive electrode, the layered gel-polymer electrolyte comprising the liquid electrolyte, and a negative electrode, such that the layered gel-polymer electrolyte is positioned between the positive electrode and the negative electrode, wherein, after laminating, the first interface layer conforms to the positive electrode to ensure conformal contact with the positive electrode, wherein, after laminating, the second interface layer conforms to the negative electrode to ensure conformal contact with the negative electrode, wherein the first interface layer has a first thickness selected based on a surface roughness of the positive electrode, wherein the second interface layer has a second thickness, different from the first thickness, and selected based on a surface roughness of the negative electrode, different from the surface roughness of the positive electrode, and wherein a portion of the liquid electrolyte is transferred from the layered gel-polymer electrolyte to both the positive electrode and the negative electrode, while and after laminating the stack.
2. 2 . The method of claim 1 , further comprising adding one or more fillers to the polymer solution.
3. 3 . The method of claim 2 , wherein the one or more fillers comprise one or more of titanium dioxide (TiO 2 ) particles, silicon dioxide (SiO 2 ), aluminum oxide (Al 2 O 3 ), sulfide compounds, garnet structure oxides, NASICON-type phosphate glass ceramics (LAGP), oxynitrides, and AB3-type hydrogen storage alloy.
4. 4 . The method of claim 1 , further comprising adding water to the polymer solution.
5. 5 . The method of claim 1 , wherein introducing the liquid electrolyte into at least one of the support core and the first interface layer comprises degassing the support core and the first interface layer.
6. 6 . The method of claim 1 , wherein the liquid electrolyte comprises an electrolyte solvent and an electrolyte salt.
7. 7 . The method of claim 1 , wherein the support core comprises at least one of polypropylene (PP), polyethylene (PE), poly(ethylene-co-tetrafluoroethylene (PETFE), poly(ethylenechloro-co-trifluoroethylene), polystyrene, polyvinyl chloride polypropylene, polyamide, polyimide, polyacrylic, polyacetal, polycarbonate, polyester, polyetherimide, polyimide, polyketone, polyphenylene ether, or polyphenylene sulfide.
8. 8 . The method of claim 1 , wherein the support core has a porosity of between 30% and 60%.
9. 9 . The method of claim 1 , wherein the support core comprises a surface layer, forming at least one of the first surface or the second surface of the support core, wherein the surface layer comprises one or more ceramic materials.
10. 10 . The method of claim 9 , wherein the one or more ceramic materials of the surface layer of the support core comprise at least one of Al 2 O 3 , SiO 2 , or MgO.
11. 11 . The method of claim 1 , wherein the first interface layer comprises at least one of polyvinylidene fluoride-co-hexafluoropropylene (PVDF-HFP), polyacrylonitrile (PAN), poly(methyl methacrylate) (PMMA), or polyethylene oxide (PEO).
12. 12 . The method of claim 1 , wherein the first interface layer has a porosity of between 30% and 60%.
13. 13 . The method of claim 1 , wherein the liquid electrolyte is distributed within both the support core and the first interface layer.
14. 14 . The method of claim 1 , wherein the first interface layer has a thickness of at least 20 micrometers.
15. 15 . The method of claim 1 , wherein the first interface layer has a thickness of at least 50 micrometers.
16. 16 . The method of claim 1 , wherein a thickness of the first interface layer is greater than a surface roughness of the positive electrode.
17. 17 . The method of claim 16 , wherein a thickness of the second interface layer is greater than a surface roughness of the negative-electrode.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS This application is a continuation of U.S. application Ser. No. 17/111,070, filed on 2020 Dec. 3, which claims the benefit under 35 U.S.C. § 119(e) of U.S. Provisional Patent Application No. 62/943,145, filed on 2019 Dec. 3, which is incorporated herein by reference in its entirety for all purposes. TECHNICAL FIELD The present disclosure relates generally to layered gel-polymer electrolytes, electrochemical cells comprising these layered gel-polymer electrolytes, and methods of forming these layered gel-polymer electrolytes and forming these electrochemical cells. BACKGROUND High-capacity rechargeable electrochemical cells with long cycle lives are desirable for various applications, such as electronics, electric vehicles (EVs), and power tools. Various types of electrochemical cells are being developed to meet different application needs, such as increasing the energy and power density of the cells. One approach involves incorporating new active material structures (e.g., particles) that have large surface areas or, more specifically, large electrochemically active surface areas. However, particles with large surface areas are usually used for electrodes with high surface roughness. Rough electrode surfaces, in turn, may result in poor contact and unstable interfaces between these electrodes and conventional liquid electrolytes. For example, various undesirable reactions between electrode materials, exposed on these surfaces, and electrolytes can cause decomposition, lithium-ion trapping, or other problems. In extreme examples, these problems can even cause thermal runaways of electrochemical cells. Gel-polymer electrolytes have been proposed as a solution for reducing undesirable reactions at the electrode-electrolyte interface. However, integrating gel-polymer electrolytes into electrochemical cells (e.g., lithium-ion cells) has been challenging. Various attempts have been used with limited success. One approach involves applying a polymer solution onto an electrode, followed by a solvent-plasticizer extraction. However, this process is not efficient and provides poor porosity control of the resulting electrolyte layer. Furthermore, this approach requires significant amounts of liquid electrolyte, which is not practical. Another approach involves forming a gel-polymer electrolyte by dissolving a lithium-containing electrolyte salt in a non-aqueous solvent and a polymer host/matrix. Gel-polymer electrolyte sublayers are then formed on both negative and positive electrodes, collectively forming electrode-electrolyte subassemblies. An electrochemical cell is then formed by stacking these subassemblies. The uniformity is hard to control with this approach when a gel-polymer electrolyte is applied directly onto the electrodes with active material layers often causing electrical shorts. Yet another approach involves mixing a liquid electrolyte with a polymer monomer. Cell fabrication is similar to using a conventional liquid electrolyte, which involves filling the electrolyte-polymer mixture into a partially assembled cell, followed by thermal-initiated polymerization of the monomer in the mixture. This post-assembly polymerization forms the gel-polymer electrolyte in situ between the electrodes in electrochemical cells. However, some monomers may remain unreacted. Furthermore, the thermal-initiated polymerization requires high temperatures, which may be undesirable for other components of these cells, such as a separator and insulators. What is needed are layered gel-polymer electrolytes, electrochemical cells formed using these layered gel-polymer electrolytes, and methods of forming these layered gel-polymer electrolytes and also forming these electrochemical cells. SUMMARY Provided are layered gel-polymer electrolytes and electrochemical cells comprising these electrolytes as well as methods of forming the electrolytes and the cells. A gel-polymer electrolyte comprises a support core and one or two interface layers on the core surface. The interface layers are relied on to conform to electrode surfaces with high surface roughness, while the support core prevents any physical penetration and electrical shorts through the gel-polymer electrolyte, e.g., by electrode protruding peaks. Specifically, the interface layer redistributes around these protruding peaks and forms a continuous interface with the electrode surface. When the stack is compressed, the gel-polymer electrolyte also releases some liquid electrolyte, which soaks the electrode and enhances ionic transfer within the electrode and through the electrolyte-electrode interface. The gel-polymer electrolyte is formed by coating interface layers on the support core and soaking this assembly in a liquid electrolyte. In some examples, a layered gel-polymer electrolyte for pacing between a first electrode and a second electrode of an electrochemical cell comprises a support core, comprising a first surface and a seco