Cross-linked PEO-based composite solid electrolyte and preparation method thereof
By introducing bis(acetylacetonyl)diisopropyl titanate crosslinking agent and inorganic filler into PEO-based solid electrolyte, a crosslinked PEO-based composite solid electrolyte is formed, which solves the problem of insufficient mechanical strength of PEO-based solid electrolyte and achieves efficient lithium dendrite suppression and electrochemical performance improvement.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- UNIV OF ELECTRONICS SCI & TECH OF CHINA
- Filing Date
- 2026-01-12
- Publication Date
- 2026-04-17
AI Technical Summary
PEO基固态电解质机械强度不足，容易在循环过程中被锂枝晶刺穿，导致电池内部短路，且电化学性能有待提升。
Bis(acetylacetonyl)diisopropyl titanate was used as a crosslinking agent to crosslink with polyethylene oxide (PEO) to form a three-dimensional network structure, which enhanced mechanical strength. Inorganic fillers such as lithium lanthanum titanium oxide (LLTO) were added to improve stability.
It significantly improves the mechanical strength and electrochemical performance of PEO-based solid electrolytes, and the lithium symmetric battery has a cycle life of over 1300h at 60℃ with an ionic conductivity of 5.6×10-4 S/cm, thus reducing production costs.
Smart Images
Figure CN121885752A_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the technical field of solid electrolytes for lithium batteries, specifically providing a cross-linked PEO-based composite solid electrolyte and its preparation method. Background Technology
[0002] With rapid economic development, non-renewable energy sources are being continuously depleted, leading to a surge in pollution problems. Therefore, developing environmentally friendly new energy sources is urgently needed. Rechargeable lithium-ion batteries, due to their high volumetric energy, high energy density, and long cycle life, have become a key alternative to fossil fuels and traditional energy sources, and are widely used in various portable electronic devices, electric vehicles, and large-scale energy storage systems. Currently, most commercial lithium-ion batteries (LIBs) use organic liquid electrolytes; however, organic liquid electrolytes pose risks of combustion, explosion, and leakage. In contrast, solid-state electrolytes (SPEs) offer higher safety, a wider electrochemical window, and a higher operating temperature range, and can effectively suppress lithium dendrite growth. Furthermore, solid-state electrolytes also boast higher energy densities than the highest energy density currently available in commercial liquid lithium-ion batteries.
[0003] Polyethylene oxide (PEO)-based polymer solid electrolytes possess excellent flexibility, good lithium salt dissociation ability, and excellent interfacial contact with electrodes (especially lithium metal anodes), while also being inexpensive, leading to their extensive research over the past few decades. The ether oxygen bond (-COC-) in the PEO backbone can react with lithium ions (Li... + Coordination occurs, and Li is realized through local movement of chain segments. + PEO-based solid electrolytes possess the intrinsic properties of solid-state ion conductors due to their ability to transport ions. However, they suffer from a fatal flaw: insufficient mechanical strength, making them susceptible to being pierced by lithium dendrites during cycling, leading to internal short circuits. Therefore, this invention provides a cross-linked PEO-based composite solid electrolyte and its preparation method to improve the mechanical strength and electrochemical performance of PEO-based solid electrolytes. Summary of the Invention
[0004] The purpose of this invention is to provide a cross-linked PEO-based composite solid electrolyte and its preparation method, which can improve the mechanical strength and electrochemical performance of PEO-based solid electrolytes. This invention creatively proposes bis(acetylacetonyl)diisopropyl titanate (TAA) as a cross-linking agent for PEO-based composite solid electrolytes. The introduction of the cross-linking agent can significantly increase the mechanical strength of PEO and increase the stability of PEO-based solid electrolytes to lithium metal, thereby improving cycle life and electrochemical performance.
[0005] To achieve the above objectives, the technical solution adopted by the present invention is as follows:
[0006] A cross-linked PEO-based composite solid electrolyte, characterized in that the cross-linked PEO-based composite solid electrolyte comprises polyethylene oxide (PEO), lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), and bis(acetylacetonyl)diisopropyl titanate, wherein the bis(acetylacetonyl)diisopropyl titanate serves as a cross-linking agent, and the content of bis(acetylacetonyl)diisopropyl titanate is 3wt%~5wt% of polyethylene oxide, based on the mass of polyethylene oxide (PEO).
[0007] Furthermore, the molar ratio of the ether oxygen atom in the polyethylene oxide to lithium bis(trifluoromethanesulfonyl)imide is EO:Li. + = 16 : 1.
[0008] Furthermore, the cross-linked PEO-based composite solid electrolyte also contains an inorganic filler, which is lithium lanthanum titanium oxide (LLTO), lithium lanthanum zirconium oxide (LLZO) or lithium aluminum titanium phosphorus (LATP). Based on the mass of polyethylene oxide (PEO), the content of the inorganic filler is 15-40 wt% of polyethylene oxide.
[0009] Meanwhile, the present invention also provides a method for preparing the cross-linked PEO-based composite solid electrolyte, characterized by comprising the following steps:
[0010] Step 1: Using acetonitrile as a solvent, add polyethylene oxide and lithium bis(trifluoromethanesulfonyl)imide in a certain proportion to acetonitrile, mix evenly to form a mixed slurry;
[0011] Step 2: Add bis(acetylacetonyl)diisopropyl titanate to the mixed slurry in a certain proportion and stir under water bath heating to complete cross-linking and form an electrolyte slurry;
[0012] Step 3: Pour the electrolyte slurry into a mold and vacuum dry it to obtain a cross-linked PEO-based solid electrolyte.
[0013] Furthermore, in step 2, the water bath heating temperature is 50~90℃, and the time is 2~6h.
[0014] Furthermore, between step 1 and step 2, the following steps are also included: adding lithium lanthanum titanium oxide, lithium lanthanum zirconium oxide, or lithium aluminum titanium phosphorus to the mixed slurry in a certain proportion and mixing them evenly.
[0015] Furthermore, between steps 2 and 3, the electrolyte slurry is placed in a vacuum chamber and subjected to multiple vacuuming processes to eliminate air bubbles.
[0016] Furthermore, the polyethylene oxide (PEO) has a molecular weight of 600,000, which is a commonly used type of PEO in PEO-based solid electrolytes.
[0017] Furthermore, in step 3, the vacuum drying temperature is 50~80℃.
[0018] Based on the above technical solution, the beneficial effects of the present invention are as follows:
[0019] This invention creatively proposes a bis(acetylacetonate)diisopropyl titanate crosslinking agent for PEO-based composite solid electrolytes. Bis(acetylacetonate)diisopropyl titanate can undergo a crosslinking reaction with polyethylene oxide (PEO) at a predetermined temperature, thereby effectively improving the mechanical strength of the PEO-based solid electrolyte and directly resulting in an increase in the cycle life of lithium-ion batteries. More specifically, the molecular structure of bis(acetylacetonate)diisopropyl titanate is as follows... Figure 1 As shown, its crosslinking mechanism with PEO can be explained as follows: bis(acetylacetonyl)diisopropyl titanate has two isopropoxy groups (-O-iPr) and two acetylacetonyl groups (acac). Titanium ions, as Lewis acid sites, can act as catalysts for the reaction. Among them, the two isopropoxy groups directly participate in the crosslinking. The isopropoxy groups (-O-iPr) undergo a condensation reaction with the terminal hydroxyl groups (-OH) on the polyethylene oxide (PEO) chain to generate stable Ti-OC covalent bonds and isopropanol (iPrOH), ultimately forming a three-dimensional network structure in the PEO matrix, thereby reducing the crystallinity of PEO and increasing its mechanical strength. Furthermore, the two acetylacetonyl groups in bis(acetylacetonyl)diisopropyl titanate act as stable chelating ligands. Their chelating effect can prevent excessive polymerization of titanium, stabilize the titanium center, and ensure that each titanium atom is connected to only two PEO chains. In addition, the byproduct isopropanol will volatilize during the subsequent vacuum drying process and will not contaminate the PEO-based solid electrolyte.
[0020] Based on the above-mentioned bis(acetylacetonyl)diisopropyl titanate crosslinking agent, the present invention provides a crosslinked PEO-based composite solid electrolyte and its preparation method, which has the following advantages:
[0021] 1) This invention uses bis(acetylacetone) diisopropyl titanate as a crosslinking agent to increase the mechanical properties of PEO-based solid electrolyte, enhance the ability of PEO-based solid electrolyte to suppress lithium dendrites, and directly manifests in the increase of cycle life of the assembled lithium symmetric battery.
[0022] 2) The cross-linked PEO-based composite solid electrolyte provided by this invention exhibits good stability to lithium metal. At an operating temperature of 60°C, the assembled lithium symmetric battery maintains a stability of 0.2 mA•cm⁻¹. -2 It can operate stably for over 1300 hours under current density.
[0023] 3) The cross-linked PEO-based composite solid electrolyte provided by this invention exhibits high ionic conductivity. At an operating temperature of 60°C, the ionic conductivity of the assembled stainless steel symmetrical battery was tested using electrochemical impedance spectroscopy, and it reached 5.6 × 10⁻⁶. -4 S / cm;
[0024] 4) The cross-linked PEO-based solid electrolyte preparation process provided by the present invention is simple. Compared with other common cross-linking methods, it only requires heating and stirring. Moreover, the amount of bis(acetylacetonyl)diisopropyl titanate cross-linking agent added is 5wt% or less, which does not require too many raw materials and can effectively reduce the production cost. Attached Figure Description
[0025] Figure 1 This is a schematic diagram of the molecular structure of bis(acetylacetonyl)diisopropyl titanate in this invention.
[0026] Figure 2 The XRD patterns are those of the PEO-based composite solid electrolyte membranes in Example 1 and Comparative Example 1 of the present invention.
[0027] Figure 3 The images show the FTIR spectra of the PEO-based composite solid electrolyte membranes in Example 1 and Comparative Example 1 of this invention.
[0028] Figure 4 The lithium symmetric batteries assembled with the PEO-based solid electrolyte in Examples 1-3 of this invention were tested at 60°C and 0.2 mA•cm. -2 Cyclic performance curves under operating conditions.
[0029] Figure 5 The lithium symmetric batteries assembled with the PEO-based solid electrolytes in Comparative Examples 1-2 of this invention were tested at 60°C and 0.2 mA•cm. -2 Cyclic performance curves under operating conditions.
[0030] Figure 6 The image shows the electrochemical impedance spectroscopy of the stainless steel symmetric battery assembled with the PEO-based solid electrolyte membrane in Example 4 of this invention at 60°C. Detailed Implementation
[0031] To make the objectives, technical solutions, and technical effects of this invention clearer and more complete, the invention will be further described in detail below with reference to the accompanying drawings and embodiments.
[0032] Example 1
[0033] This embodiment provides a cross-linked PEO-based composite solid electrolyte comprising polyethylene oxide (PEO), lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), lithium lanthanum titanium oxide (LLTO), and bis(acetylacetonyl)diisopropyl titanate (TAA). The bis(acetylacetonyl)diisopropyl titanate serves as a cross-linking agent, with its content at 5 wt% of the weight of PEO. The lithium lanthanum titanium oxide serves as an inorganic filler, with its content at 20 wt% of the weight of PEO. It should be noted that the common applications of bis(acetylacetonyl)diisopropyl titanate include coating materials, inks, organic synthesis reaction catalysts, or as a precursor for preparing titanium dioxide electron transport layers in perovskite batteries.
[0034] The cross-linked PEO-based composite solid electrolyte is prepared by the following steps:
[0035] First, using acetonitrile as solvent and lithium bis(trifluoromethanesulfonyl)imide as lithium salt, 0.5 g of PEO and 0.204 g of LiTFSI (EO : Li+ = 16 : 1) were weighed using an electronic balance with an accuracy of 0.01%, dissolved in 12 ml of acetonitrile, and magnetically stirred at 800 rpm for 24 h to obtain a transparent mixed slurry A;
[0036] Then, 0.1g of LLTO (20wt% of the mass of PEO) was weighed using an electronic balance with an accuracy of 0.01%, and added to the electrolyte slurry A above. The mixture was magnetically stirred at 1000rpm for 24h until it was fully mixed and homogeneous, resulting in a white electrolyte slurry B.
[0037] Next, 34 µl of a 75% TAA solution (5 wt% of the mass of PEO) was accurately weighed using a pipette and added to white electrolyte slurry B. The mixture was then heated and stirred in a water bath at 60°C for 3 hours to obtain electrolyte slurry C.
[0038] Finally, the electrolyte slurry C was poured into a polytetrafluoroethylene plate mold and placed in a vacuum chamber to be vacuumed twice to remove air bubbles in the electrolyte membrane and avoid residual air bubbles causing pores after subsequent drying and film formation. Further, the electrolyte slurry C was dried in a vacuum drying oven at 60°C for 12 hours to form a film, and then transferred to a glove box filled with argon atmosphere (H2O < 0.1 ppm, O2 < 0.1 ppm) and allowed to stand for 6 hours to obtain a cross-linked PEO-based solid electrolyte membrane.
[0039] Based on the above-mentioned cross-linked PEO-based solid electrolyte membrane, this embodiment provides a lithium metal symmetric battery with lithium metal on both sides and a cross-linked PEO-based solid electrolyte membrane in the middle. It is prepared by the following steps: the solid electrolyte membrane after sufficient cooling is cut into uniform circular pieces with a diameter of 16 mm and a thickness of about 100 µm. Then, the solid electrolyte membrane is assembled into a lithium symmetric battery in the following order: positive electrode shell - lithium metal - cross-linked PEO-based electrolyte membrane - lithium metal - stainless steel sheet - spring sheet - negative electrode shell.
[0040] Example 2
[0041] This embodiment provides a cross-linked PEO-based composite solid electrolyte, which differs from Example 1 in that: the content of bis(acetylacetonyl)diisopropyl titanate is 3wt% of polyethylene oxide, and the amount of TAA solution used in the preparation process is 20µl; based on the cross-linked PEO-based solid electrolyte membrane in this embodiment, a lithium metal symmetric battery is also assembled for electrochemical performance testing.
[0042] Example 3
[0043] This embodiment provides a cross-linked PEO-based composite solid electrolyte, which differs from Example 1 in that the content of bis(acetylacetonyl)diisopropyl titanate is 4wt% of polyethylene oxide, and the amount of TAA solution used in the preparation process is 27µl. Based on the cross-linked PEO-based solid electrolyte membrane in this embodiment, a lithium metal symmetric battery is also assembled and electrochemical performance is tested.
[0044] Example 4
[0045] This embodiment provides a stainless steel symmetrical battery, which is formed by assembling the cross-linked PEO-based solid electrolyte membrane prepared in Examples 1 to 3 in the following order: positive electrode shell - stainless steel sheet - cross-linked PEO-based solid electrolyte membrane - stainless steel sheet - spring sheet - negative electrode shell.
[0046] Example 5
[0047] This embodiment provides a cross-linked PEO-based composite solid electrolyte, which differs from Embodiment 1 in that the cross-linked PEO-based composite solid electrolyte does not contain lithium lanthanum titanium oxide (LLTO). Based on the cross-linked PEO-based solid electrolyte membrane in this embodiment, a lithium metal symmetric battery is also assembled for electrochemical performance testing.
[0048] The beneficial effects of the present invention will be described in detail below with reference to the test results. In order to more intuitively demonstrate the significant progress of the present invention, the present invention provides Comparative Example 1 and Comparative Example 2. The difference between Comparative Example 1 and Example 1 is that the PEO-based composite solid electrolyte does not contain bis(acetylacetonyl)diisopropyl titanate and lithium lanthanum titanium oxide (LLTO). The difference between Comparative Example 2 and Example 1 is that the PEO-based composite solid electrolyte does not contain bis(acetylacetonyl)diisopropyl titanate.
[0049] XRD and FTIR tests were performed on the PEO-based composite solid electrolytes in Example 1 and Comparative Example 1, and the results are as follows: Figure 2 and Figure 3 As shown in the figure, the introduction of the bis(acetylacetonyl)diisopropyl titanate crosslinking agent in this invention does not affect the structure of the solid electrolyte (XRD and FTIR spectra).
[0050] The electrochemical performance of the lithium-symmetric batteries assembled in Examples 1-3 was tested at 60°C and 0.2 mA•cm. -2 The cyclic performance curve under the working conditions is as follows: Figure 4 As shown, for comparison, the electrochemical performance of the lithium symmetric batteries assembled in Comparative Examples 1 and 2 was tested using the same kit, and the cycle performance curves are shown below. Figure 5 As shown in the figure, the introduction of bis(acetylacetonate) diisopropyl titanate crosslinking agents (3wt%, 4wt%, 5wt%) in this invention can effectively improve the cycle life of lithium symmetric batteries. In particular, at 5wt%, the cycle life of lithium symmetric batteries exceeds 1350h. This indicates that the TAA crosslinking agent effectively improves the stability of PEO-based composite solid electrolytes for lithium, especially enhancing their ability to suppress lithium dendrites. This can be attributed to the condensation reaction between the isopropoxy group of TAA and the -OH group at the end of the PEO chain, thereby achieving effective crosslinking and increasing the mechanical strength of the PEO-based composite solid electrolyte.
[0051] Furthermore, the stainless steel symmetric cell assembled in Example 4 was tested, and the electrochemical impedance spectroscopy at 60°C is shown below. Figure 6 As shown in the figure, the ionic conductivity of the PEO-based composite solid electrolyte reaches 5.6 × 10⁻⁶. -4 S / cm. It should also be noted that when the amount of TAA crosslinking agent added is 5wt%, the measured impedance value increases compared to the amount added is 3wt%, and the ionic conductivity also decreases. Therefore, the amount of surface crosslinking agent should not be too much.
[0052] Example 6
[0053] This embodiment provides a cross-linked PEO-based composite solid electrolyte, which differs from Embodiment 1 in that the cross-linked PEO-based composite solid electrolyte uses lithium lanthanum zirconium oxide (LLZO) as an inorganic filler. Based on the cross-linked PEO-based solid electrolyte membrane in this embodiment, a lithium metal symmetric battery was also assembled for electrochemical performance testing. After testing the lithium metal symmetric battery under identical conditions, with a bis(acetylacetonate)diisopropyl titanate cross-linking agent of 5 wt% and a lithium lanthanum zirconium oxide content of 20 wt% of polyethylene oxide, the lithium symmetric battery cycle life exceeded 1800 h; this result is superior to LLTO.
[0054] Example 7
[0055] This embodiment provides a cross-linked PEO-based composite solid electrolyte, which differs from Embodiment 1 in that the cross-linked PEO-based composite solid electrolyte uses lithium aluminum titanium phosphate (LATP) as an inorganic filler. Based on the cross-linked PEO-based solid electrolyte membrane in this embodiment, a lithium metal symmetric battery was also assembled for electrochemical performance testing. After testing the lithium metal symmetric battery, under completely identical test conditions, with a bis(acetylacetonate)diisopropyl titanate cross-linking agent of 5 wt% and a lithium aluminum titanium phosphate content of 20 wt% of polyethylene oxide, the lithium symmetric battery cycle life exceeded 1500 h; the results are similar to LLTO.
[0056] The above description is merely a specific embodiment of the present invention. Any feature disclosed in this specification may be replaced by other equivalent or similar features unless otherwise specified. All disclosed features, or steps in all methods or processes, may be combined in any way except for mutually exclusive features and / or steps.
Claims
1. A cross-linked PEO-based composite solid electrolyte, characterized in that, The cross-linked PEO-based composite solid electrolyte comprises polyethylene oxide (PEO), lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), and bis(acetylacetonyl)diisopropyl titanate, wherein the bis(acetylacetonyl)diisopropyl titanate serves as a cross-linking agent, and the content of bis(acetylacetonyl)diisopropyl titanate is 3wt% to 5wt% of polyethylene oxide, based on the mass of polyethylene oxide (PEO).
2. The cross-linked PEO-based composite solid electrolyte according to claim 1, characterized in that, The molar ratio of the ether oxygen atoms in the polyethylene oxide to lithium bis(trifluoromethanesulfonyl)imide is EO : Li. + = 16 :
1.
3. The cross-linked PEO-based composite solid electrolyte according to claim 1, characterized in that, The cross-linked PEO-based composite solid electrolyte also contains an inorganic filler, which is lithium lanthanum titanium oxide (LLTO), lithium lanthanum zirconium oxide (LLZO), or lithium aluminum titanium phosphorus (LATP). The content of the inorganic filler is 15-40 wt% of the polyethylene oxide (PEO) based on the mass of the polyethylene oxide.
4. The preparation method of the cross-linked PEO-based composite solid electrolyte according to claim 1, characterized in that, Includes the following steps: Step 1: Using acetonitrile as a solvent, add polyethylene oxide and lithium bis(trifluoromethanesulfonyl)imide in a certain proportion to acetonitrile, mix evenly to form a mixed slurry; Step 2: Add bis(acetylacetonyl)diisopropyl titanate to the mixed slurry in a certain proportion and stir under water bath heating to complete cross-linking and form an electrolyte slurry; Step 3: Pour the electrolyte slurry into a mold and vacuum dry it to obtain a cross-linked PEO-based solid electrolyte.
5. In the preparation method of the cross-linked PEO-based composite solid electrolyte according to claim 4, in step 2, the water bath heating temperature is 50~90℃ and the time is 2~6h.
6. The preparation method of the cross-linked PEO-based composite solid electrolyte according to claim 4, wherein step 2 further comprises the following step between step 1 and step 2: Add lithium lanthanum titanium oxide, lithium lanthanum zirconium oxide, or lithium aluminum titanium phosphorus to the mixed slurry in a certain proportion and mix evenly.
7. The preparation method of the cross-linked PEO-based composite solid electrolyte according to claim 4, wherein step 2 further includes the following step between step 2 and step 3: The electrolyte slurry was placed in a vacuum chamber and subjected to multiple vacuuming processes to eliminate air bubbles.
8. In the preparation method of the cross-linked PEO-based composite solid electrolyte according to claim 4, in step 2, the molecular weight of the polyethylene oxide (PEO) is 600,000, which is a commonly used PEO type for PEO-based solid electrolytes.
9. In the preparation method of the cross-linked PEO-based composite solid electrolyte according to claim 4, in step 2 and step 3, the vacuum drying temperature is 50~80℃.