Patent Application
20240291022
This application claims all benefits under 35 U.S.C. § 119 from the Chinese Patent Application No. 202310164971.9, filed on Feb. 24, 2023, in the China National Intellectual Property Administration, the disclosure of which is incorporated herein by reference.
The present disclosure relates to a battery technology, and particular to a composite electrolyte membrane, a preparation method thereof and a lithium-sulfur battery.
Lithium-sulfur battery is a lithium battery with sulfur element as the positive electrode and metallic lithium as the negative electrode. Lithium-sulfur batteries using sulfur as the cathode active material have a high electric capacity (1675 mAh/g) and a high energy density (2600 Wh/kg), making them the energy storage devices with good development prospects.
During the charge and discharge process of lithium-sulfur batteries, complex electrochemical reactions will occur and various intermediates will be produced. These intermediates can be dissolved in the electrolyte and diffuse. If these intermediates diffuse and deposit on the separator or lithium metal surface, they will cause loss of the positive electrode active material and a passivation of the lithium metal surface.
In order to illustrate the technical solutions of the embodiments of the present application more clearly, the accompanying drawings in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present application, and therefore should not be seen as limiting the scope. For one of ordinary skill in the art, other related drawings can also be obtained from these drawings without any creative work.
It will be appreciated that for simplicity and clarity of illustration, where appropriate, reference numerals have been repeated among the different figures to indicate corresponding or analogous elements. In addition, numerous specific details are set forth in order to provide a thorough understanding of the embodiments described herein. However, it will be understood by those of ordinary skill in the art that the embodiments described herein can be practiced without these specific details. In other instances, methods, procedures, and components have not been described in detail so as not to obscure the related relevant feature being described. The drawings are not necessarily to scale, and the proportions of certain parts may be exaggerated better illustrate details and features. The description is not to be considered as limiting the scope of the embodiments described herein.
The term “outside” refers to a region that is beyond the outermost confines of a physical object. The term “inside” indicates that at least a portion of a region is partially contained within a boundary formed by the object. The term “substantially” is defined to essentially conforming to the particular dimension, shape or other word that substantially modifies, such that the component need not be exact. For example, substantially cylindrical means that the object resembles a cylinder, but can have one or more deviations from a true cylinder. The term “comprising” means “including, but not necessarily limited to”; it specifically indicates open-ended inclusion or membership in a so-described combination, group, series and the like. It should be noted that references to “an” or “one” embodiment in this disclosure are not necessarily to the same embodiment, and such references mean at least one.
The composite electrolyte membrane and its preparation method as well as the lithium-sulfur battery provided by the present disclosure will be further described in detail below with reference to the accompanying drawings and specific examples.
An embodiment of the present disclosure provides a composite electrolyte membrane. The composite electrolyte membrane comprises a lithium salt compound, a polymer material, a solid electrolyte, and a plasticizer. A weight ratio between the lithium salt compound, the polymer material, the solid electrolyte and the plasticizer is 20-25:30-40:20-30:15-20.
The lithium salt compound comprises at least one of lithium fluoride (LiF), lithium bisfluorosulfonimide (LiO4NS2F2, referred to as LiFSI), lithium bistrifluoromethanesulfonimide (LiN(CF3SO2)2, referred to as LiTFSI), Lithium bis(perfluoroethylsulfonimide) (Li(C2F5SO2)2N, referred to as LiBETI), and lithium dioxalatoborate (LiB(C2O4)2), referred to as LiBOB). The lithium salt compound can belithium fluoride LiF, LiFSI, LiTFSI, LiBETI, LiBOB or combination thereof. It can be understood that, other lithium salt compounds used in conventional lithium ion batteries can also satisfy the present disclosure.
The polymer material comprises at least one of polyvinylidene fluoride (PVDF), (polyvinylidene fluoride-hexafluoropropylene) copolymer (PVDF-HFP), polyvinyl alcohol (PVA), polylactic acid (PLA), polyethylene glycol alcohol (PEG), polymethyl methacrylate (PMMA), propylene glycol methyl ether acetate (PMA) and polyacrylic acid (PAA). The polymer material can be PVDF, PVDF-HFP, PVA, PLA, PEG, PMMA, PMA,PAA or combination thereof.
The solid electrolyte can be at least one of lithium lanthanum zirconium oxide (LLZO), tantalum-doped lithium lanthanum zirconium oxide (LLZTO), and lithium aluminum titanium phosphate (LATP).
The plasticizer can be at least one of ethylene carbonate (EC), succinonitrile (succinonitrile), sulfolane (sulfolane), and tetraglyme (tetraglyme). A purpose of the plasticizer is to improve an ionic conductivity of the composite electrolyte membrane. The composite electrolyte membrane still maintains a solid appearance, and a form of the plasticizer does not affect the shape of the composite electrolyte membrane.
In the composite electrolyte membrane, the lithium salt compound is configured to increase a conductivity of lithium ions. The polymer material is configured to slow down diffusion of polysulfide. The solid electrolyte is configured to increase the conductivity of ions, slow down the diffusion of polysulfides, and avoid direct puncture by lithium dendrites. The plasticizer is configured to improve the transmission efficiency of ions. In one embodiment, the composite electrolyte membrane consists of the lithium salt compound, the polymer material, the solid electrolyte and the plasticizer. The weight ratio between the lithium salt compound, the polymer material, the solid electrolyte and the plasticizer can be 20-25:30-40:20-30:15-20.
In another embodiment, the polymer material of the composite electrolyte membrane is a mixture of PVDF and PMMA, the solid electrolyte is LLZO, the plasticizer is Tetraethylene glycol dimethyl ether (TEGDME or tetraglyme), and the lithium salt compound is LiTFSI. The weight ratio between the lithium salt compound, the polymer material, the solid electrolyte and the plasticizer is 23:36:23:18.
The embodiment of the present disclosure further comprises a polysulfide diffusion experiment on the composite electrolyte membrane. Specifically, the composite electrolyte membrane was clamped using an H-type electrolytic cell (H-Cell), and a 1M Li2S4 solution dissolved in DME (1,2-Dimethoxyethane) was injected into the composite electrolyte membrane from one side of the composite electrolyte membrane. DME was injected into the composite electrolyte membrane from the other side of the composite electrolyte membrane to observe a rate of the polysulfides diffusion. Compared with the traditional separator sample (Celgard 2320), the diffusion rate of polysulfides is reduced by 100 to 1000 times, which indicates that the composite electrolyte membrane of the present disclosure can prevent the diffusion of polysulfides and avoid passivation of the lithium metal surface.
Another embodiment of the present disclosure further provides a method for preparing the composite electrolyte membrane, which comprises the following steps:
In steps S1, S2 and S3, the mixing order of the lithium salt compound, polymer material, solid electrolyte and plasticizer is not limited. A weight ratio between the lithium salt compound, the polymer material, the solid electrolyte and the plasticizer is 20-25:30-40:20-30:15-20.
In step S4, during the drying process, the liquid plasticizer does not affect the appearance of the composite electrolyte membrane, and the appearance of the composite electrolyte membrane is solid.
In step S4, a material of the substrate is not limited and can be polytetrafluoroethylene or the like. A method of applying the third composite on the substrate surface is not limited, can be coating, spraying, pouring, or etc. The drying method is not limited, such as vacuum heating, baking, etc.
In one embodiment, the third composite is coated on a polytetrafluoroethylene substrate surface, and then is removed after baking to form a solid composite electrolyte membrane.
Referring to
The preparation process of the lithium-sulfur battery can be as follows: putting the positive electrode plate into a positive electrode shell of the button battery and dripping an electrolyte, then placing the composite electrolyte membrane on the positive electrode plate and dripping the electrolyte again, and then placing the negative electrode plate on the composite electrolyte membrane to a button lithium-sulfur battery.
The composite electrolyte membrane and its preparation method and the lithium-sulfur battery have the following advantages: first, the composite electrolyte membrane has no holes and can effectively avoid polysulfide diffusion, thereby avoiding passivation of the lithium metal surface; second, the preparation method of the composite electrolyte membrane described above has a simple process and can realize industrial large-scale production.
The embodiments shown and described above are only examples. Even though numerous characteristics and advantages of the present technology have been set forth in the foregoing description, together with details of the structure and function of the present disclosure, the disclosure is illustrative only, and changes may be made in the detail, including in matters of shape, size, and arrangement of the parts within the principles of the present disclosure, up to and including the full extent established by the broad general meaning of the terms used in the claims.
Depending on the embodiment, certain of the steps of methods described may be removed, others may be added, and the sequence of steps may be altered. The description and the claims drawn to a method may comprise some indication in reference to certain steps. However, the indication used is only to be viewed for identification purposes and not as a suggestion for ordering the steps.
| Number | Date | Country | Kind |
|---|---|---|---|
| 202310164971.9 | Feb 2023 | CN | national |
