Modified composite solid electrolyte membrane and preparation method thereof

Abstract

The invention relates to the technical field of solid-state batteries, in particular to a modified composite solid-state electrolyte membrane and a preparation method thereof.The modified composite solid-state electrolyte membrane comprises an electrolyte base material and a doping agent for shaping the electrolyte base material; wherein the electrolyte base material comprises modified polyethylene oxide, the modified polyethylene oxide is polyethylene oxide grafted functional resin, the functional resin is E12 epoxy resin, and the dopant comprises lithium salt and LCSZM.LATP high-entropy solid solution electrolyte. Through the technical scheme of the invention, the problem of possibility of chain degradation caused by gaps between the interfaces is avoided as far as possible, the ion transmission property and the stability of a mechanical structure are improved, and the solid-solid interface fitting degree is enhanced.

Description

Technical Field

[0001] The present invention belongs to the technical field of solid-state batteries, and in particular relates to a modified composite solid-state electrolyte membrane and a preparation method thereof. Background Art

[0002] As China vigorously develops its new energy industry, the energy density of liquid lithium batteries is approaching its limit. The flammability of liquid electrolytes also poses safety risks. Solid-state batteries, with their superior safety and energy density, are widely recognized as the next generation of battery development.

[0003] Existing solid-state lithium metal electrolytes are primarily classified into three categories: polymer solid electrolytes, inorganic solid electrolytes, and composite solid electrolytes. Polymer-based solid electrolytes offer excellent mechanical flexibility and formability and are commonly used in thin-film electrolyte materials. However, their ionic conductivity is relatively low, typically failing to achieve the conductivity levels required for lithium metal batteries at room temperature. Furthermore, polymer electrolytes exhibit poor chemical stability at the lithium metal anode interface and are prone to side reactions with lithium metal, forming an unstable interfacial layer that increases interfacial impedance and degrades battery performance. Consequently, composite solid electrolytes have become a research hotspot. Composite electrolytes improve ionic conductivity by introducing inorganic fillers (such as alumina and silica) and oxide solid electrolytes into a polymer matrix. Furthermore, surface modification or the addition of a transition layer can enhance interfacial stability with the anode. However, without liquid substances, as charging and discharging proceed, the positive and negative electrode material layers expand and contract in a rigid interface manner, resulting in the gradual appearance of gaps between the positive and negative electrode interfaces and the electrolyte layer as the cycle progresses, causing poor interface contact and increased interface resistance. When used at high power, the battery cell generates heat, loses energy, consumes active lithium, and precipitates and accumulates at the interface of the gaps to form lithium dendrites, which accelerates local degradation and ultimately leads to cell capacity decay or failure. Summary of the Invention

[0004] To address the above-mentioned issues, the present invention provides a modified composite solid electrolyte membrane and its preparation method. By modifying a polyethylene oxide (PEO) substrate and polymerizing a functional epoxy compound (E12 epoxy resin), the modified PEO material achieves multi-point adhesion to the positive or negative electrode layer under specific process conditions. This allows the electrolyte layer to maintain close contact with the positive and negative electrode layers, leveraging the PEO material's flexible electrolyte properties and forcing the PEO layer to expand and contract with the positive and negative electrodes, thereby reducing the possibility of interfacial voids and cascading degradation. The modified PEO material is then composited with a lithium salt and a modified oxide solid electrolyte filler to form a modified polymer solid electrolyte membrane. Under specific conditions, this membrane adheres to the positive and negative electrode layers, improving ion transport and mechanical structure while enhancing the solid-solid interface fit and reducing the possibility of interfacial voids.

[0005] To achieve the above technical advantages, the present invention uses E12 epoxy resin as a triggerable functional binder. The catalyst induces partial ring-opening of the epoxy resin, and pulsed heating reaction is carried out. The oxygen atom of the ether bond (-O-) in the PEO material is used as a nucleophile to attack the carbon atom after the epoxy group is ring-opened, forming a new C-O bond, and crosslinking PEO with E12 epoxy resin. The modified PEO is used as a substrate and mixed with materials such as fillers, lithium salts, and oxide electrolytes, and then cast into an electrolyte membrane.

[0006] In the first aspect, the present invention provides a modified composite solid electrolyte membrane, comprising:

[0007] An electrolyte substrate and a dopant for shaping the electrolyte substrate; wherein, the electrolyte substrate comprises modified poly(ethylene oxide), the modified poly(ethylene oxide) is poly(ethylene oxide) grafted with a functional resin, the functional resin is E12 epoxy resin, the dopant comprises a lithium salt and an LCSZM·LATP high-entropy solid-solution electrolyte; the molecular formula of the LCSZM·LATP high-entropy solid-solution electrolyte is Li ,

[0012] Al b Ti c ·(LiZrMoSrCo) x (PO4)3 (1 < a, c < 1.9, 0 < b, x < 0.6), preferably Li 1.4 Al 0.3 Co 0.1 Zr 0.1 Ti 1.3 Mo 0.1 Sr 0.1 (PO4)3.

[0008] In the second aspect, the present invention further provides a preparation method for a modified composite solid electrolyte membrane, which is used to prepare a modified composite solid electrolyte membrane, and the method comprises:

[0009] Step 1: After mixing poly(ethylene oxide) and E12 epoxy resin, carry out pulsed heating with reciprocating temperature to control the degree of the grafting reaction between the poly(ethylene oxide) and the E12 epoxy resin, and obtain modified poly(ethylene oxide);

[0010] Step 2: Add a lithium salt and an LCSZM·LATP high-entropy solid-solution electrolyte to the modified poly(ethylene oxide), stir and evaporate to dryness by an evaporator to obtain a colloid, extrude and shape the colloid, and place it in a vacuum oven at 50°C - 60°C for baking for 4h - 12h and then roll it step by step to obtain a modified composite solid electrolyte membrane.

[0011] Optionally, in Step 1, after mixing poly(ethylene oxide) and E12 epoxy resin, carrying out pulsed heating with reciprocating temperature, comprises:

[0012] Step 11: Add polyethylene oxide and E12 epoxy resin into a reactor, and control the temperature in the reactor between 25° C. and 40° C., add solvent into the reactor, and add hydroquinone after dissolving, and stir evenly;

[0013] Step 12, after raising the temperature in the reactor to a first temperature at a heating rate of 1°C / min-3°C / min, dropwise adding methylhexahydrophthalic anhydride solution into the reactor for a set time;

[0014] Step 13, lowering the temperature in the reactor to a second temperature;

[0015] Step 14: cyclically perform steps 12 and 13 until the amount of the methylhexahydrophthalic anhydride solution added dropwise to the reactor reaches a preset mass, lowering the temperature of the solution in the reactor to 25-40° C. and stirring to obtain modified polyethylene oxide.

[0016] Optionally, the mass ratio of the polyethylene oxide to the E12 epoxy resin is 100:1-8:1.

[0017] Optionally, the amount of hydroquinone added is 0.1%-0.8%, preferably 0.5%, of the total mass of the polyethylene oxide and the E12 epoxy resin.

[0018] Optionally, the mass of the methylhexahydrophthalic anhydride solution is 10%-35% of the mass of the E12 epoxy resin, preferably 22.5%.

[0019] Optionally, the lithium salt is one or more of LiTFSI, LiFSI, LiDFP, LiBOB, LiDFOB, and LiFTFSI.

[0020] Optionally, the mass of the lithium salt is 5%-20% of the mass of the modified polyethylene oxide.

[0021] The technical solution provided by the present invention has the following advantages compared with the prior art:

[0022] The present invention provides a modified composite solid-state electrolyte membrane and its preparation method. Pulse heating is used to control the ring-opening rate of the epoxy compound, and hydroquinone is used as a polymerization inhibitor to control the polymerization rate of the epoxy compound with PEO ether bonds and the self-polymerization of the epoxy compound. While ensuring the degree of polymerization between the E12 epoxy resin and PEO, some of the epoxy groups in the E12 are maintained to function as an adhesive under specific conditions in the presence of an initiator. A high-entropy solid-solution electrolyte, LCSZM·LATP, is also used as a filler to enhance the mechanical strength and ionic conductivity of the electrolyte membrane. After being formed, the solid-state electrolyte membrane, under the action of a specific coating or in-situ generated initiator, rapidly adheres to the contact interface or positive electrode surface in a specific temperature environment, preventing the formation of gaps with the expansion and contraction of the positive and negative electrodes during charging and discharging. Furthermore, the membrane inhibits lithium deposition and the formation of lithium dendrites, reduces the growth rate of interfacial contact resistance, and slows the capacity decay of the battery cell. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments consistent with the present disclosure and, together with the description, serve to explain the principles of the present disclosure.

[0024] In order to more clearly illustrate the embodiments of the present disclosure or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, for ordinary technicians in this field, other drawings can be obtained based on these drawings without any creative work.

[0025] Figure 1 A schematic flow chart of a method for preparing a modified composite solid electrolyte membrane provided by the present invention;

[0026] Figure 2 This is a SEM image of the solid electrolyte membrane provided in Example 1. DETAILED DESCRIPTION

[0027] In order to more clearly understand the above-mentioned objectives, features and advantages of the present disclosure, the scheme of the present disclosure will be further described below. It should be noted that the embodiments of the present disclosure and the features therein can be combined with each other in the absence of conflict.

[0028] In the following description, many specific details are set forth to facilitate a full understanding of the present disclosure, but the present disclosure may also be implemented in other ways different from those described herein; it is obvious that the embodiments in the specification are only part of the embodiments of the present disclosure, rather than all of the embodiments.

[0029] To address the poor electrical performance of solid-state batteries, the present invention provides a modified composite solid-state electrolyte membrane and its preparation method. Pulsed heating is used to control the ring-opening rate of the epoxy compound, and hydroquinone is used as a polymerization inhibitor to control the polymerization rate of the epoxy compound with PEO ether bonds and the self-polymerization of the epoxy compound. While ensuring the degree of polymerization between the E12 epoxy resin and PEO, the epoxy groups of the E12 resin are maintained, allowing them to function as adhesives under specific conditions in the presence of an initiator. A high-entropy solid-solution electrolyte, LCSZM·LATP, is also used as a filler to enhance the mechanical strength and ionic conductivity of the electrolyte membrane. After fabrication, the solid-state electrolyte membrane, under the action of a specific coating or in-situ generated initiator, rapidly adheres to the contact interface or positive electrode surface in a specific temperature environment, preventing the formation of gaps with the expansion and contraction of the positive and negative electrodes during charging and discharging. Furthermore, the membrane inhibits lithium deposition and the formation of lithium dendrites, reduces the growth rate of interfacial contact resistance, and slows cell capacity decay.

[0030] In order to better understand the present invention, examples and comparative examples are provided below.

[0031] Example 1: Add 22g of PEO and E12 epoxy resin in a mass ratio of 10:1 to a double-layer glass reactor. Use a hot and cold integrated mold temperature controller to control the reactor temperature at 25°C. Inject 150g of acetonitrile solvent and stir to dissolve. Then add 0.1g of hydroquinone and stir evenly. The water jacket temperature is controlled by setting the mold temperature controller. The temperature in the reactor is raised to 80°C at a rate of 1°C per minute. After reaching 80°C, MHHPA (methylhexahydrophthalic anhydride) solution is added dropwise. After 5s, switch to 10°C cold water, stop adding MHHPA solution, keep stirring, cool to the temperature in the reactor below 60°C, and then repeat the steps of heating to 80°C and adding MHHPA solution dropwise. The total amount of MHHPA solution added is 0.5g. After all the MHHPA solution has been added, the solution is cooled to room temperature and stirred for 30 minutes. 22g of Li is added to the solution. 1.4 Al 0.3 Co 0.1 Zr 0.1 Ti 1.3 Mo 0.1 Sr 0.1 The (PO4)3 material and 2g of LiTFSI were stirred and poured into a vacuum rotary evaporator to evaporate the liquid to dryness until a colloid was formed. The colloid was transferred to a mold, extruded and shaped, and then dried in a vacuum oven at 50-60°C for 4-12 hours. The modified composite solid electrolyte membrane was then rolled to 30μm in thickness, which could be cut and assembled into battery cells. The puncture strength and conductivity of the modified composite solid electrolyte membrane were tested using a universal tensile testing machine. Figure 2 Graph showing the morphology of the solid electrolyte membrane prepared in Example 1.

[0032] The positive electrode material LiNi 0.85 Co0.05 Mn 0.1 The O2 material was fabricated using a positive electrode sheet with a mass ratio of positive electrode material: conductive agent (carbon black): binder (polyvinylidene fluoride) of 94:2:4. 2-ethyl-4-methylimidazole was sprayed on the positive electrode. The negative electrode used a copper-lithium alloy also sprayed with 2-ethyl-4-methylimidazole. The positive electrode, modified composite solid electrolyte membrane, and negative electrode stack were assembled and hot-pressed at 70°C for 1 hour to achieve complete bonding between the modified composite solid electrolyte membrane and the positive and negative electrode sheets. A universal tensile testing machine was used to test interfacial peel strength, and the assembled battery was tested for capacity and cycling performance.

[0033] Example 2: The preparation steps are the same as those in Example 1, except that Li 1.4 Al 0.3 Co 0.1 Zr 0.1 Ti 1.3 Mo 0.1 Sr 0.1 The amount of (PO4)3 material added is 60g.

[0034] Example 3: The preparation steps are the same as those in Example 1, except that Li 1.4 Al 0.3 Co 0.1 Zr 0.1 Ti 1.3 Mo 0.1 Sr 0.1 The amount of (PO4)3 material added was 2 g.

[0035] The comparative example is an unmodified PEO membrane.

[0036] The physical and chemical test and electrochemical test results of the comparative example, embodiment 1, embodiment 2 and embodiment 3 are shown in Table 1.

[0037] Table 1 Performance comparison between the examples and the comparative examples

[0038] project Comparative Example Example 1 Example 2 Example 3 Puncture strength (N / um) 0.18 0.54 0.71 0.32 Room temperature conductivity (S / cm) <![CDATA[1.02×10 -5 ]]> <![CDATA[2.23×10 -4 ]]> <![CDATA[5.32×10 -4 ]]> <![CDATA[0.95×10 -4 ]]> Peeling force between electrolyte membrane and cathode (N / mm) 0.28 — — — 0.1C first week discharge capacity (mAh / g) 163.5 176.5 179.6 172.3 0.1C first week efficiency (%) 76.3 84.27 86.31 81.5 100-cycle capacity retention rate (%) 61.5 92.6 94.1 90.8

[0039] It should be noted that since the current collector peeling force is smaller than the positive electrode and electrolyte membrane peeling force, the universal tensile testing machine cannot measure the accurate peeling force between the modified composite solid electrolyte membrane and the positive and negative electrodes.

[0040] As shown in Table 1, the puncture strength and room-temperature conductivity of Examples 1, 2, and 3 are significantly improved compared to the control example. In electrochemical performance testing, the modified composite solid electrolyte prepared using the present invention has a 0.1C discharge capacity of nearly 180 mAh / g, a 0.1C first-cycle efficiency of over 81%, and a 100-cycle capacity retention rate of over 90%.

[0041] In summary, the present invention provides a modified composite solid-state electrolyte membrane and its preparation method. E12 epoxy resin is used as a triggerable functional binder. MHHPA induces partial ring opening of the epoxy resin. Through a controlled pulse heating reaction, the oxygen atom in the ether bond (-O-) of the polyethylene oxide material acts as a nucleophile to attack the carbon atom after the epoxy ring opening, forming a new CO bond. PEO and the E12 epoxy resin are then cross-linked. Hydroquinone is used as a polymerization inhibitor to control the polymerization rate of the polyethylene oxide ether bond and the self-polymerization of the epoxy compound. The modified polyethylene oxide is then mixed with a lithium salt and an LCSZM·LATP high-entropy solid-solution electrolyte to form an electrolyte membrane. The LCSZM·LATP high-entropy solid-solution electrolyte is used as a filler to enhance the mechanical strength and ionic conductivity of the electrolyte membrane. The modified composite solid electrolyte membrane prepared can adhere quickly under the action of a specific coating or in-situ generated initiator in a specific temperature environment, and is in close contact with the contact interface or the positive electrode surface. It can also give full play to the flexible electrolyte characteristics of the polyethylene oxide material, forcing the polyethylene oxide layer to expand and contract with the positive and negative electrodes, and not produce gaps with the expansion and contraction of the positive and negative electrodes during charging and discharging. At the same time, it can inhibit lithium deposition and the formation of lithium dendrites, reduce the growth rate of the interface contact resistance, and delay the capacity decay of the battery cell.

[0042] The modified PEO membrane prepared using the method provided by the present invention can achieve multi-point adhesion with the positive and negative electrode layers while improving ionic conductivity, so that the electrode sheets are in close contact, giving full play to the flexible electrolyte properties of PEO. It can expand and contract with the positive and negative electrodes during the charging and discharging process, inhibiting the generation of gaps at the rigid interface that cause poor interface contact, lithium dendrites and other problems, thereby improving the service life of the solid-state battery.

[0043] Although the present invention has been described above, the present invention is not limited to the above-mentioned specific embodiments. The above-mentioned specific embodiments are merely illustrative and not restrictive. Under the guidance of the present invention, ordinary technicians in this field can make many variations without departing from the purpose of the present invention, and these are all protected by the present invention.

Claims

1. A modified composite solid electrolyte membrane, characterized in that: include: An electrolyte substrate and a dopant for shaping the electrolyte substrate; wherein the electrolyte substrate comprises modified polyethylene oxide, the modified polyethylene oxide is a polyethylene oxide-polymerized functional resin, the functional resin is E12 epoxy resin, and the dopant comprises a lithium salt and an LCSZM·LATP high entropy solid solution electrolyte; the molecular formula of the LCSZM·LATP high entropy solid solution electrolyte is Li a Al b Ti c (LiZrMoSrCo) x (PO4)3,1 <a,c<1.9,0<b,x<0.6。 2. A method for preparing a modified composite solid electrolyte membrane, characterized in that: For preparing the modified composite solid electrolyte membrane according to claim 1, the method comprises: Step 1: After mixing polyethylene oxide and E12 epoxy resin, perform pulse heating with reciprocating temperature to control the degree of polymerization reaction between the polyethylene oxide and the E12 epoxy resin, and obtain modified polyethylene oxide; Step 2: adding lithium salt and LCSZM·LATP high entropy solid solution electrolyte to the modified polyethylene oxide, stirring and evaporating to dryness to obtain a colloid, extruding the colloid to shape, and drying it in a vacuum oven at 50°C-60°C for 4h-12h, and then rolling it step by step to obtain a modified composite solid electrolyte membrane.

3. The method for preparing a modified composite solid electrolyte membrane according to claim 2, wherein: The step 1, after mixing polyethylene oxide and E12 epoxy resin, performs pulse heating with reciprocating temperature, comprises: Step 11: Add polyethylene oxide and E12 epoxy resin into a reactor, and control the temperature in the reactor between 25° C. and 40° C., add solvent into the reactor, and add hydroquinone after dissolving, and stir evenly; Step 12, after raising the temperature in the reactor to a first temperature at a heating rate of 1°C / min-3°C / min, dropwise adding methylhexahydrophthalic anhydride solution into the reactor for a set time; Step 13, lowering the temperature in the reactor to a second temperature; Step 14: cyclically perform steps 12 and 13 until the amount of the methylhexahydrophthalic anhydride solution added dropwise to the reactor reaches a preset mass, lowering the temperature of the solution in the reactor to 25-40° C. and stirring to obtain modified polyethylene oxide.

4. The method for preparing a modified composite solid electrolyte membrane according to claim 2 or 3, characterized in that: The mass ratio of the polyethylene oxide to the E12 epoxy resin is 100:1-8:

1.

5. The method for preparing a modified composite solid electrolyte membrane according to claim 3, wherein: The amount of hydroquinone added is 0.1%-0.8% of the total mass of the polyethylene oxide and the E12 epoxy resin.

6. The method for preparing a modified composite solid electrolyte membrane according to claim 3, wherein: The mass of the methylhexahydrophthalic anhydride solution is 10%-35% of the mass of the E12 epoxy resin.

7. The method for preparing a modified composite solid electrolyte membrane according to claim 2, wherein: The lithium salt is one or more of LiTFSI, LiFSI, LiDFP, LiBOB, LiDFOB, and LiFTFSI.

8. The method for preparing a modified composite solid electrolyte membrane according to claim 2, wherein: The mass of the lithium salt is 5%-20% of the mass of the modified polyethylene oxide.

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