Secondary aqueous battery electrodes containing vinyl acetate-ethylene

Abstract

The green secondary electrode includes a conductive substrate, an active material and a material additive in direct contact with the conductive substrate, and a combination of a vinyl acetate-ethylene based additive and a methyl cellulose based additive that binds the conductive substrate, the active material, and the material additive. The green secondary electrode can be a positive electrode or a negative electrode.

Description

[Technical field]

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS This application claims priority to U.S. patent application Ser. No. 17 / 569,338, filed Jan. 5, 2022, the disclosure of which is incorporated herein by reference in its entirety. [Background technology]

[0002] The present disclosure relates to secondary electrodes and batteries including the same.

[0003] The secondary battery may include a cathode and an anode.

[0004] The chemical reactions in a secondary battery are reversible: when the cell is being charged, the cathode becomes positive and the anode becomes negative; when the cell is being discharged, it behaves like a primary battery. Summary of the Invention

[0005] The electrochemical component has a green secondary electrode that includes a conductive substrate, an electrochemically active material and material additives in direct contact with the conductive substrate, and a combination of vinyl acetate-ethylene (VAE) and a methylcellulose-based additive, such as carboxymethylcellulose (CMC) or hydroxypropylmethylcellulose (HPMC), that binds the conductive substrate, electrochemically active material, and material additives together. Specifically, electrodes for water-based batteries, such as lithium-zinc batteries, nickel-zinc (Ni-Zn) batteries, silver-zinc batteries, zinc-air batteries, and zinc-ion batteries, made with these binders are mechanically robust and exhibit high electrochemical performance. [Brief description of the drawings]

[0006] [Figure 1] 1 is a field emission scanning electron microscope image of a negative electrode formed from a zinc-based active material, material additives, and a conductive substrate bound together by VAE and HPMC. [Diagram 2]1 is a field emission scanning electron microscope image of a positive electrode formed from a nickel hydroxide based active material, material additives, and a conductive substrate bound together by VAE and HPMC. [Diagram 3] FIG. 2 is a schematic diagram of a negative electrode formed from a zinc-based active material, material additives, and a conductive substrate bound together by VAE and HPMC. [Figure 4] FIG. 1 is a schematic diagram of a positive electrode formed from a nickel-based active material, material additives, and a conductive substrate bound together by VAE and HPMC. [Diagram 5] 1 is a utilization versus cycle life graph of Ni-Zn cells with negative electrodes including binder systems including different combinations of VAE and styrene butadiene rubber (SBR) with HPMC or hydroxyethyl cellulose (HEC) and CMC. [Figure 6] 1 is a utilization versus cycle life graph of Ni-Zn cells having positive electrodes with binder combinations of HPMC and VAE or polytetrafluoroethylene (PTFE). [Figure 7] 1 is a graph of utilization versus cycle life for Ni-Zn cells having negative electrodes containing VAE, SBR, and ethylene vinyl acetate (EVA) with HPMC, or HEC with CMC binder combinations. [Figure 8] 1 is a bar graph showing the total measured energy transferred in Ni-Zn cells having negative electrodes containing EVA, SBR and VAE with HPMC or HEC and CMC binder combinations until the cells reach 80% utilization. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0007] Various embodiments are described herein. However, the disclosed embodiments are merely exemplary, and other embodiments may take various alternative forms not explicitly shown or described. The figures are not necessarily to scale, and some features may be exaggerated or minimized to show details of specific components. Therefore, specific structural and functional details disclosed herein are not to be interpreted as limiting, but merely as representative basis for teaching those skilled in the art. Furthermore, various features illustrated and described with reference to any one figure can be combined with features illustrated in one or further other figures to produce embodiments not explicitly shown or described. The combination of illustrated features provides a representative embodiment for a typical application. Various combinations and modifications of features consistent with the teachings of the present disclosure may be desired for a particular application or implementation.

[0008] The challenge for aqueous battery systems is to select a suitable binder system that is chemically compatible with the electrolyte and can adequately bind the active materials. One solution to this problem has been to incorporate traditional binders, for example PTFE or HEC. However, PTFE is expensive and may lack binding strength without sintering or fibrillation. Furthermore, commonly used PTFE suspensions contain surfactants to aid dispersion in the solution. The surfactants and / or processing steps commonly used with PTFE binders may cause initial battery problems due to decomposition of the active material in the electrode at the high temperatures required for sintering, mechanical stress / strain during fibrillation crushing of the active material, foaming of the surfactant limiting electrolyte access in the electrode, or surfactant degradation affecting the electrode / electrolyte. Furthermore, when powdered PTFE is used as a binder system, it must be fibrillated using organic solvents. The use of organic solvents in large-scale production is costly and may cause other problems.

[0009] Alternative water-based binders that are common in other battery chemistries, such as SBR and EVA used in lithium-ion chemistries, have had some success, but these binders, even in combination with methylcellulose-based binders, lack the individual bonding qualities and must be combined with another strong binder, such as sintered PTFE.

[0010] To overcome the problems of using PTFE, SBR, and EVA binders, VAE and methylcellulose-based binders and compounds were substituted into electrodes of an alkaline Ni-Zn battery system, and unexpectedly obtained superior robustness and electrochemical results compared to PTFE, SBR, and EVA. Those skilled in the art will know that copolymers of vinyl acetate and ethylene are divided into two different and separate categories: VAE, where the copolymer is 40% or more vinyl acetate, and EVA, where the copolymer is up to 40% vinyl acetate. However, a typical VAE copolymer contains 60% or more vinyl acetate. The percentage of vinyl acetate in the copolymer has a significant effect on the material properties of the copolymer, and therefore may affect the material properties of binder combinations made with VAE or EVA. The combination of VAE and methylcellulose-based binders provides an inexpensive, surfactant-free, water-based binder system, resulting in a stable slurry and robust, homogenous electrodes. Furthermore, electrodes made with the combination of VAE and methylcellulose-based binders were robust enough that they did not require additional binders, unlike SBR and EVA. For example, FIG. 1 shows a homogeneous zinc-based negative electrode utilizing VAE and HMPC as a binder system, and FIG. 2 shows a homogeneous nickel hydroxide-based positive electrode utilizing VAE and HPMC as a binder system.

[0011] Referring to FIG. 3, the green secondary negative electrode 10 includes a conductive substrate 12 (e.g., aluminum, brass, bronze, carbon, conductive polymer, copper, stainless steel, steel, tin, titanium, zinc, or combinations thereof), which may be, for example, a foil, expanded metal, or foam with or without perforations, a negative active material 14 (e.g., aluminum or cadmium based, hydrogen absorbing alloy, intercalation material, iron based, zinc based), other material additives 16 (e.g., conductive additives, electrolyte retention additives, gas suppression additives, gelling agents, nucleation additives, plasticizers, stabilization additives, and / or combinations thereof), a binder combination of VAE 18 and methylcellulose based additive 20, and a tab 22. The conductive substrate 12 is in direct contact with the tab 22. The negative active material 14 is in direct contact with the conductive substrate 12. The combination of VAE 18 and methylcellulose based additive 20 binds the conductive substrate 12, the negative active material 14, and the other material additives 16. The electrolyte 24 fills the voids in the negative electrode 10 .

[0012] Referring to FIG. 4, the green secondary cathode 110 includes a conductive substrate 112 (e.g., aluminum, carbon, conductive polymer, nickel, stainless steel, steel, titanium, or a combination thereof), which may be, for example, a foil, expanded metal, fabric, or foam with or without perforations, a positive active material 114 (e.g., an intercalation material, manganese oxide, nickel hydroxide, a precious metal, a perovskite, Prussian blue, silver, spinel, or vanadium), other material additives 116 (e.g., a conductive additive, an electrolyte retention additive, a gas suppression additive, a gelling agent, a nucleation additive, a plasticizer, a stabilization additive, and / or a combination thereof), a binder combination of VAE 118 and a methylcellulose-based additive 120, and a tab 122. The conductive substrate 112 is in direct contact with the tab 122. The positive active material 114 is in direct contact with the conductive substrate 112. The combination of VAE 118 and methylcellulose based additive 120 binds the conductive substrate 112, the positive active material 114, and the other material additives 116. An electrolyte 124 fills the voids in the positive electrode 110.

[0013] As shown in Figures 5 and 6, electrodes using VAE and HPMC provide unexpected results of superior utilization vs. cycle life compared to commonly used binder combinations including SBR, HEC-CMC, and PTFE. These unexpected results are further supported by data comparing different binder system combinations. As shown in Figure 7, cells using VAE and HEC-CMC showed similar cycle life to cells using SBR and HEC-CMC or HPMC, but better than cells using EVA and HEC-CMC. However, when combined with HPMC, cells using VAE showed longer cycle life than cells using SBR or EVA. The high performance of the VAE and HMPC binder combination can also be seen in the delivered kilowatt-hours compared to the other binder combinations tested, as shown in Figure 8. These tests demonstrate unexpected superior performance for electrodes made with VAE and methylcellulose-based binder combinations.

[0014] The words used herein are words of description rather than limitation, and it is understood that various changes may be made without departing from the spirit and scope of the present disclosure and the claims. As previously described, features of various embodiments may be combined to form further embodiments that may not be expressly described or illustrated. Although various embodiments may have been described as offering advantages or being preferred over other or prior art embodiments with respect to one or more desired characteristics, those skilled in the art will recognize that one or more features or characteristics may be compromised to achieve desired overall system attributes that depend on the particular application and embodiment. These attributes include, but are not limited to, cost, strength, durability, life cycle cost, marketability, appearance, packaging, size, maintainability, weight, manufacturability, ease of assembly, and the like. Thus, an embodiment described as less desirable than other or prior art implementations with respect to one or more characteristics is not outside the scope of this disclosure and may be desirable for a particular application.

Claims

1. 1. An aqueous battery element comprising a green secondary negative electrode comprising a conductive substrate, an active material and a material additive in direct contact with said conductive substrate, and a combination of ethylene vinyl acetate and a methyl cellulose based additive binding said conductive substrate, said active material and said material additive.

2. 2. The water battery element of claim 1, wherein the vinyl acetate ethylene is an emulsion of copolymerized vinyl acetate and ethylene, and the vinyl acetate is 40 wt% or more of the copolymerized vinyl acetate and ethylene.

3. 10. The aqueous battery element of claim 1, wherein the combination further comprises carboxymethylcellulose or hydroxypropylmethylcellulose.

4. 10. The water battery element of claim 1, wherein the green secondary electrode further comprises a conductive additive, an electrolyte retention additive, a gas suppressing additive, a gelling agent, a nucleating additive, a plasticizer, a stabilizing additive, or a combination thereof.

5. 2. The water battery element of claim 1, wherein the active material is aluminum-based, cadmium-based, hydrogen storage alloy, intercalation material, iron-based, or zinc-based.

6. A battery comprising the water battery element of claim 1.

7. 1. An aqueous battery element comprising a green secondary positive electrode comprising a conductive substrate, an active material and a material additive in direct contact with said conductive substrate, and a combination of ethylene vinyl acetate and a methyl cellulose based additive binding said conductive substrate, said active material and said material additive.

8. 8. The water battery element of claim 7, wherein the vinyl acetate ethylene is an emulsion of copolymerized vinyl acetate and ethylene, and the vinyl acetate is 40 wt% or more of the copolymerized vinyl acetate and ethylene.

9. 8. The aqueous battery element of claim 7, wherein the combination further comprises carboxymethylcellulose or hydroxypropylmethylcellulose.

10. 8. The water battery element of claim 7, wherein the green secondary electrode further comprises a conductive additive, an electrolyte retention additive, a gas suppressing additive, a gelling agent, a nucleating additive, a plasticizer, a stabilizing additive, or a combination thereof.

11. 8. The water battery element of claim 7, wherein the active material is an intercalation material, manganese oxide, nickel hydroxide, a noble metal, a perovskite, silver, a spinel, Prussian blue, or vanadium.

12. A battery comprising the water battery element of claim 7.

13. a green zinc-based secondary negative electrode comprising a conductive substrate, an active material, and a material additive bound together by a combination of vinyl acetate-ethylene and methyl cellulose based binders; A nickel-zinc battery comprising a green nickel hydroxide based positive electrode including a conductive substrate, an active material, and a material additive bound together by a combination of a vinyl acetate-ethylene binder and a methylcellulose based binder.

14. 14. The battery of claim 13, wherein the vinyl acetate-ethylene is an emulsion of copolymerized vinyl acetate and ethylene, and the vinyl acetate is 40 wt% or more of the copolymerized vinyl acetate and ethylene.

15. 14. The battery of claim 13, wherein each of the combinations further comprises carboxymethyl cellulose or hydroxypropyl methyl cellulose.

16. 14. The battery of claim 13, wherein each of the electrodes further comprises a conductive additive, an electrolyte retention additive, a gas suppressing additive, a gelling agent, a nucleating additive, a plasticizer, a stabilizing additive, or a combination thereof.

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