A gel electrolyte with high ionic conductivity and high cation transference number and a construction method

Abstract

The application discloses a kind of gel electrolyte with high ionic conductivity and high cation transference number and construction method, including selecting Lewis base to be dissolved in carbonate electrolyte, and gel electrolyte is formed by standing;Lewis base includes: aluminium chloride, aluminium isopropanol and other Lewis base that can initiate ring-opening polymerization of carbonate and participate in coordination;Carbonate includes: ethylene carbonate and propylene carbonate and other cyclic carbonates that can occur ring-opening polymerization;The mass fraction ratio range of Lewis base in carbonate electrolyte is the minimum concentration that can form gel to the saturated concentration in electrolyte.The disclosed gel electrolyte with high ionic conductivity and high cation transference number of the application eliminates the concentration difference polarization existing in alkali metal interface, fundamentally solves the cause of metal dendrite generation, thereby greatly improves the stability of alkali metal battery.

Description

Technical Field

[0001] This invention belongs to the field of energy storage batteries, and more specifically, relates to a gel electrolyte with high ionic conductivity and high cation transference number and a method for constructing it. Background Technology

[0002] Alkali metals, due to their high specific capacity and low reduction potential, are considered key anode materials for next-generation energy storage devices and a crucial foundation for developing high-energy-density batteries. However, their practical application faces a critical obstacle: achieving uniform deposition of cations on the metal surface is difficult. This problem stems from electrolyte decomposition and concentration polarization at the electrode-electrolyte interface, leading to low coulombic efficiency, uneven deposition morphology, and ultimately, deterioration in cycle performance and serious safety hazards. Therefore, constructing a stable metal-electrolyte interface to mitigate concentration polarization and suppress electrolyte decomposition is central to achieving the large-scale application of alkali metal batteries.

[0003] Interfacial concentration polarization primarily stems from the mismatch between cation migration rates and interfacial reaction rates. Theoretical analysis indicates that suppressing polarization requires the electrolyte to simultaneously possess high cation transport numbers (e.g., close to 1) and high ionic conductivity (e.g., approximately 10). - ³–10 - ² S cm - ¹. In traditional liquid electrolytes, the high mobility of anions limits the cation transference number to below 0.5, leading to significant concentration polarization even with high bulk conductivity. While electrode surface modification can locally homogenize the current distribution, it fails to overcome the inherent limitations of the electrolyte itself, proving effective only at low current densities and unable to prevent dendrite growth under high current or long cycling conditions. Therefore, developing gel electrolytes that combine high ionic conductivity and high cation transference number is a key approach to overcoming these fundamental obstacles. Summary of the Invention

[0004] To address the shortcomings and improvement needs of existing technologies, this invention provides a gel electrolyte with high ionic conductivity and high cation transference number, which eliminates concentration polarization at the alkali metal interface, fundamentally solves the cause of metal dendrite formation, and thus significantly improves the stability of alkali metal batteries.

[0005] To achieve the above objectives, according to one aspect of the present invention, a gel electrolyte with high ionic conductivity and high cation transference number is provided, comprising: selecting a Lewis base, dissolving it in a carbonate electrolyte, and forming a gel electrolyte by standing.

[0006] Preferably, Lewis bases include: aluminum chloride, aluminum isopropoxide, and other Lewis bases that can initiate ring-opening polymerization of carbonates and participate in coordination.

[0007] Preferably, carbonates include ethylene carbonate and propylene carbonate, as well as other cyclic carbonates that undergo ring-opening polymerization.

[0008] Preferably, the mass fraction of Lewis bases in carbonate electrolytes ranges from the lowest concentration at which gels can be formed to the saturation concentration in the electrolyte.

[0009] Preferably, when the Lewis base is aluminum chloride and the carbonate is the XFSI electrolyte, the mass fraction of aluminum chloride in the XFSI electrolyte ranges from 1% to 20%, where X is an alkali metal ion, including Li, Na and K.

[0010] In summary, the above-described technical solutions conceived in this invention can achieve the following beneficial effects: This invention utilizes Lewis bases to initiate in-situ ring-opening polymerization of carbonates, simultaneously using anions as crosslinking agents to connect the polymerized oligomer molecules. By simultaneously anchoring anions and solvent molecules, an oligomer gel electrolyte with both high ionic conductivity and high cation transference number is formed. This fundamentally solves the problem of uneven deposition of metal ions at metal interfaces.

[0011] The method for constructing an oligomeric gel electrolyte with both high ionic conductivity and high cation transference number proposed in this invention has been verified to be applicable to all existing alkali metal ion battery systems, including lithium-ion, sodium-ion, and potassium-ion battery systems. Experimental verification shows that the gel electrolyte maintains high ionic conductivity and high cation transference number in all systems, demonstrating its universality. Attached Figure Description

[0012] Figure 1 The diagram shown is a schematic diagram of the dissolution of a Lewis base in a carbonate electrolyte according to an embodiment of the present invention.

[0013] Figure 2 The images shown are of the gel electrolyte before and after standing, according to an embodiment of the present invention.

[0014] Figure 3 The diagram shown is a schematic diagram of the cation migration number test results of gel electrolytes according to an embodiment of the present invention.

[0015] Figure 4 The diagram shown is a schematic representation of the test results of the electrolyte ionic conductivity provided in an embodiment of the present invention.

[0016] Figure 5 The diagram shows the performance of the electrolyte provided in a symmetrical battery according to an embodiment of the present invention. Detailed Implementation

[0017] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention. Furthermore, the technical features involved in the various embodiments of this invention described below can be combined with each other as long as they do not conflict with each other.

[0018] In this invention, the terms "first," "second," etc. (if present) in the invention and the accompanying drawings are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence.

[0019] Example 1: This invention discloses a gel electrolyte with high ionic conductivity and high cation transport number, comprising: dissolving a Lewis base in a carbonate electrolyte and forming a gel electrolyte by standing. Figure 1 The diagram shows the dissolution of Lewis bases in carbonate electrolytes. Figure 2 Images showing Lewis bases dissolved in carbonate electrolytes before and after standing.

[0020] In embodiments of the present invention, Lewis bases include: aluminum chloride, aluminum isopropoxide, and other Lewis bases that initiate ring-opening polymerization of carbonates and participate in coordination. Carbonates include: ethylene carbonate and propylene carbonate, and other cyclic carbonates that undergo ring-opening polymerization. The mass fraction ratio of Lewis bases in carbonate electrolytes ranges from the lowest concentration capable of forming a gel to the saturation concentration in the electrolyte.

[0021] Specifically, when the Lewis base is aluminum chloride and the carbonate is the XFSI electrolyte, the mass fraction of aluminum chloride in the XFSI electrolyte ranges from 1% to 20%, where X is an alkali metal ion, such as Li, Na, K, etc.

[0022] In one alternative embodiment, a certain mass fraction of a Lewis base, such as AlCl3 with a purity of 99.999%, is added to a commercially available potassium / sodium / lithium difluorosulfonylimide electrolyte, such as XFSI, where X is Li, Na, or K, in a carbonate (propylene carbonate (PC) or ethylene carbonate (EC) / diethyl carbonate (DEC)) electrolyte. Under the action of the strong Lewis base, the cyclic carbonate undergoes ring-opening polymerization, forming an oligomeric gel electrolyte network through bridging by the FSI anion and the Lewis base. It should be noted that XFSI electrolytes containing different mass fractions of AlCl3 (where X is Li, Na, or K) are prepared and then allowed to stand for a certain period, such as 8 to 48 hours, to form a gel electrolyte.

[0023] In this invention, the AlCl3 used has a mass fraction of 2wt%, 4wt%, 6wt%, 8wt%, and 10wt%, respectively. The XFSI electrolyte used is 1M XFSI electrolyte, and the solvent is a mixed solvent of EC / DEC or PC (X is Li, Na, or K) with a volume ratio of 1:1.

[0024] Furthermore, the above-mentioned electrolyte is used in the assembly of symmetrical or half-cell potassium-ion batteries for energy storage systems. These potassium-ion batteries are assembled from a positive electrode, a negative electrode, a separator, a spring plate, and an electrolyte. In the symmetrical battery, the positive electrode is potassium foil, the negative electrode is potassium foil, the separator is a glass fiber separator, and the electrolyte is the gel electrolyte prepared above. In the half-cell, the positive electrode is carbon-coated aluminum foil, the negative electrode is potassium foil, the separator is a glass fiber separator, and the electrolyte is the gel electrolyte prepared above.

[0025] It should be noted that the gel electrolyte of the present invention possesses high ionic conductivity and high cation transport number, meaning that the ionic conductivity of the gel electrolyte is approximately 10. - ³–10 - ² S cm - ¹, the cation transference number is close to 1.

[0026] Example 2: This invention discloses a method for constructing a gel electrolyte with high ionic conductivity and high cation transport number, comprising: Adding a Lewis base to a carbonate electrolyte initiates the ring-opening polymerization of a five-membered carbonate to form an oligomer. Then, the oligomer, bridged by anion and Lewis base, forms an oligomeric gel electrolyte network. The anion structure contains double bonds with highly electronegative atoms, including bis(fluorosulfonyl)imide (FSI-) and difluorophosphate (PO2F2-). The Lewis base and carbonate electrolyte used in the construction process are described in Example 1 and will not be repeated here for brevity.

[0027] To verify the effect of the gel electrolyte generated by the present invention, a specific example is used. For instance, 40 mg of AlCl3 is weighed and placed in a glass bottle, and then 1 M KFSI EC / DEC electrolyte is added until the mass reaches 1 g. The mixture is then stirred for 30 min until the solution becomes transparent again. After standing for 8 h, a gel is formed. At this point, the 4 wt% AlCl3-KFSI gel electrolyte is prepared.

[0028] Using potassium metal as the positive and negative electrodes, glass fiber membrane as the separator, and the prepared electrolyte as the electrolyte solution, a CR2025 symmetrical cell was assembled in an argon-filled glove box. Figure 2 The images show the prepared electrolyte and the gel electrolyte that formed after standing. Figure 3These are the cation transport number test results of the configured gel electrolyte. Figure 4 These are the test results of the ionic conductivity of the prepared gel electrolyte. Figure 5 This is a graph showing the cycling performance of a potassium metal symmetric battery in a prepared gel electrolyte.

[0029] like Figure 3 It can be seen that the cation transference number of the electrolyte was tested using the Aurbach method, and the test results showed that the prepared gel electrolyte had a cation transference number of 0.98, which is close to that of a single cation conductor. Figure 4 It can be seen that the ionic conductivity of the gel electrolyte was tested using a conductivity meter, and the data showed that the conductivity was 9.34*10-3 S cm-1; Figure 5 The battery life is significantly improved, reaching 6,000 hours, while the battery life of traditional carbonate liquid electrolytes is less than 100 hours.

[0030] In summary, the gel electrolyte disclosed in this invention possesses high ionic conductivity (9.34*10-3 S cm-1) and high cation transference number (t+=0.98), eliminating concentration polarization at the alkali metal interface and fundamentally solving the cause of metal dendrite formation, thereby significantly improving the stability of alkali metal batteries.

[0031] Those skilled in the art will readily understand that the above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A gel electrolyte possessing high ionic conductivity and high cation transport number, characterized in that, include: Lewis bases were selected and dissolved in carbonate electrolytes to form gel electrolytes by standing.

2. The gel electrolyte with high ionic conductivity and high cation transport number according to claim 1, characterized in that, Lewis bases include: Aluminum chloride, aluminum isopropoxide, and other Lewis bases that can initiate ring-opening polymerization of carbonates and participate in coordination.

3. The gel electrolyte with high ionic conductivity and high cation transport number according to claim 1, characterized in that, Carbonates include: Ethylene carbonate and propylene carbonate, as well as other cyclic carbonates that undergo ring-opening polymerization.

4. The gel electrolyte having high ionic conductivity and high cation transference number according to claim 1, characterized by, The mass fraction ratio of Lewis bases in carbonate electrolytes ranges from the lowest concentration at which gels can form to the saturation concentration in the electrolyte.

5. The gel electrolyte having high ionic conductivity and high cation transference number according to claim 4, characterized by, When the Lewis base is aluminum chloride and the carbonate is XFSI electrolyte, the mass fraction of aluminum chloride in the XFSI electrolyte ranges from 1% to 20%, where X is an alkali metal ion, including Li, Na, and K.

6. A method for constructing a gel electrolyte having high ionic conductivity and high cation transference number, characterized by, include: Adding a Lewis base to a carbonate electrolyte initiates the ring-opening polymerization of a five-membered carbonate to form an oligomer. Then, under the bridging effect of anions and Lewis bases, the oligomer forms an oligomeric gel electrolyte network.

7. The construction method of claim 6, wherein, The anionic structure contains double bonds with highly electronegative atoms, including bis(fluorosulfonyl)imide (FSI-) and difluorophosphate (PO2F2-).

8. The construction method of claim 6, wherein, Lewis bases include: Aluminum chloride, aluminum isopropoxide, and other Lewis bases that can initiate ring-opening polymerization of carbonates and participate in coordination.

9. The construction method of claim 6, wherein, Carbonates include: Ethylene carbonate and propylene carbonate, as well as other cyclic carbonates that undergo ring-opening polymerization.

10. The construction method of claim 6, wherein, The mass fraction ratio of Lewis bases in carbonate electrolytes ranges from the lowest concentration at which gels can form to the saturation concentration in the electrolyte.

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