A modified polyethylene oxide and a method for its preparation

Abstract

The application relates to the technical field of solid-state batteries, in particular to a modified polyethylene oxide and a preparation method thereof, which comprises the following steps: mixing polyethylene oxide and E12 epoxy resin, and then carrying out temperature reciprocating pulse heating to control the degree of polycondensation reaction of the polyethylene oxide and the E12 epoxy resin, so as to obtain a modified polyethylene oxide solution; and evaporating and rinsing the polyethylene oxide solution to obtain the modified polyethylene oxide. According to the technical scheme, the possibility of chain degradation caused by the interfacial gap is avoided as much as possible, the ion transmission and the stability of the mechanical structure are improved, and the solid-solid interface adhesion 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 polyethylene oxide 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] In response to the above problems, the present invention provides a modified polyethylene oxide and a preparation method thereof. By modifying a polyethylene oxide (PEO) substrate and polymerizing functional epoxy compounds, the modified PEO material can achieve multi-point adhesion with the positive or negative electrode layer under specific process conditions, so that the electrolyte layer is in close contact with the positive and negative electrode layers, giving full play to the flexible electrolyte characteristics of the PEO material, forcing the PEO layer to expand and contract with the positive and negative electrodes, thereby reducing the possibility of chain degradation caused by gaps between the interfaces.

[0005] To achieve these technical advantages, the present invention utilizes E12 epoxy resin as a triggerable functional binder. Because this material is solid at room temperature, it can adapt to various PEO substrate processing methods. A catalyst induces partial ring opening of the epoxy resin. Through a slow reaction, the ether (-O-) oxygen atoms in the PEO material act as nucleophiles to attack the carbon atoms of the epoxy group ring-opening, forming new CO bonds. This crosslinks the PEO and E12 epoxy resin, thus avoiding problems such as excessive ring opening of the epoxy resin, which can lead to resin failure and loss of adhesion, and insufficient ring opening, which can reduce crosslinking uniformity with PEO and cause phase separation, leading to PEO modification failure.

[0006] In a first aspect, the present invention provides a method for preparing modified polyethylene oxide, comprising:

[0007] After mixing polyethylene oxide and E12 epoxy resin, performing pulse heating with reciprocating temperature to control the degree of polymerization reaction between the polyethylene oxide and the E12 epoxy resin, and obtaining a modified polyethylene oxide solution;

[0008] The polyethylene oxide solution is evaporated to dryness and rinsed to obtain modified polyethylene oxide.

[0009] Optionally, the method specifically includes:

[0010] Step 1: Add polyethylene oxide and E12 epoxy resin into a reactor, and control the temperature of the reactor between 25° C. and 40° C., add solvent into the reactor, dissolve the solvent, then add hydroquinone, and stir evenly;

[0011] Step 2, after raising the temperature in the reactor to a first temperature at a heating rate of 1°C / min-3°C / min, methylhexahydrophthalic anhydride is added dropwise to the reactor for a set time;

[0012] Step 3, lowering the temperature of the solution in the reactor to a second temperature;

[0013] Step 4, cyclically executing steps 2 and 3 until the amount of the methylhexahydrophthalic anhydride added dropwise to the reactor reaches a preset mass;

[0014] Step 5: Lower the temperature of the solution in the reactor to 25-40° C. and evaporate the solution at 30-50° C. using a vacuum rotary evaporator to remove the solvent and residual methylhexahydrophthalic anhydride and hydroquinone. Rinse the evaporated material with ethanol to obtain modified polyethylene oxide.

[0015] Optionally, the mass ratio of the polyethylene oxide to the E12 epoxy resin is 100:1-8:1.

[0016] Optionally, the amount of hydroquinone added is 0.1%-0.8% of the total mass of the polyethylene oxide and the E12 epoxy resin.

[0017] Optionally, the mass of the methylhexahydrophthalic anhydride is 10%-35% of the mass of the E12 epoxy resin.

[0018] Optionally, the first temperature is 70°C-85°C, and the second temperature is 50°C-65°C.

[0019] In a second aspect, the present invention provides a modified polyethylene oxide prepared by the method for preparing the modified polyethylene oxide provided in the first aspect.

[0020] In a third aspect, the present invention provides a solid electrolyte membrane comprising the modified polyethylene oxide provided in the second aspect.

[0021] In a fourth aspect, the present invention provides a solid-state battery comprising the solid-state electrolyte membrane provided in the third aspect.

[0022] The technical solution provided by the present invention has the following advantages compared with the prior art:

[0023] The present invention provides a modified polyethylene oxide 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 ether bond with PEO 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 epoxy resin are retained to function as an adhesive under specific conditions in the presence of an initiator.

[0024] The modified PEO material provided by the present invention can be used as a polymer solid electrolyte substrate. Modification methods such as blending with other electrolytes such as PVDF, compounding with ionic liquids, adding fillers, and using oxide solid electrolytes are no different from unmodified PEO materials and can be made into solid electrolyte membranes or positive electrode coating materials. Under the action of a specific coating or in-situ generated initiator, it can quickly adhere to the contact interface or positive electrode surface in a specific temperature environment, without generating 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 interfacial contact resistance, and delay the capacity decay of the battery cell. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] 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.

[0026] 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.

[0027] Figure 1 A schematic diagram of a specific process for preparing a modified polyethylene oxide provided in an embodiment of the present invention. DETAILED DESCRIPTION

[0028] 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.

[0029] 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.

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

[0031] Example 1:

[0032] Add 22g of polyethylene oxide and E12 epoxy resin in a 10:1 mass ratio to a double-layer glass reactor. Using a thermostat to maintain the reactor temperature at 25°C, add 150g of acetonitrile solvent and stir to dissolve. Then, add 0.1g of hydroquinone and stir evenly. The water jacket temperature is controlled by the thermostat. Raise the reactor temperature at a rate of 1°C / min to 80°C. Once the temperature reaches 80°C, add methylhexahydrophthalic anhydride (MHHPA) solution dropwise. After 5 seconds, switch to 10°C cold water and stop adding the MHHPA solution. Maintain stirring. Cool the reactor until the temperature is below 60°C, then repeat the process of raising the temperature to 80°C and adding the MHHPA solution dropwise. The total amount of MHHPA solution added is 0.5 g. After all the MHHPA solution has been added dropwise, the solution is cooled to room temperature. A vacuum rotary evaporator is used to vacuum at 50°C to evaporate and recover the solvent, residual MHHPA, and hydroquinone. After rinsing with ethanol, modified polyethylene oxide is added to obtain the modified polyethylene oxide. The modified polyethylene oxide and the unmodified polyethylene oxide are consistent in ionic conductivity and mechanical properties.

[0033] Acetonitrile is added to the modified polyethylene oxide to redissolve it, which is then cast onto a substrate and dried to produce a modified solid electrolyte membrane. 2-Ethyl-4-methylimidazole is sprayed onto the coated positive electrode sheet. The modified solid electrolyte membrane and the treated positive electrode sheet are then hot-pressed at 70°C for one hour to fully bond the polyethylene oxide-based membrane to the positive electrode sheet.

[0034] The PEO prepared in this example maintained the same ionic conductivity and mechanical properties as the unmodified PEO. 2-Ethyl-4-methylimidazole was sprayed onto the coated positive electrode sheet. The modified PEO electrolyte membrane and the treated positive electrode sheet were then hot-pressed at 70°C for 1 hour, completely bonding the PEO base film to the positive electrode sheet.

[0035] In summary, the present invention provides a modified polyethylene oxide 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 ether bond with the polyethylene oxide and the self-polymerization of the epoxy compound. While ensuring the degree of polymerization between the E12 epoxy resin and the polyethylene oxide, some of the epoxy groups in the E12 epoxy resin can function as an adhesive under specific conditions in the presence of an initiator. This prevents excessive ring-opening of the E12 epoxy resin, which can lead to resin failure and loss of adhesion, and insufficient ring-opening, which can reduce the uniformity of crosslinking with the polyethylene oxide and cause phase separation. Methylhexahydrophthalic anhydride is used as a catalyst to induce partial ring-opening of the epoxy resin. Through a slow reaction, the ether bond (-O-) oxygen atom in the polyethylene oxide material acts as a nucleophile to attack the carbon atom after the epoxy group ring-opening, forming a new CO bond, which crosslinks the polyethylene oxide with the E12 epoxy resin. Furthermore, the E12 epoxy resin is solid at room temperature, making it adaptable to various polyethylene oxide processing methods and reducing processing difficulty.

[0036] The solid electrolyte membrane prepared with modified polyethylene oxide as the base material can quickly adhere in a specific temperature environment under the action of a specific coating or in-situ generated initiator, 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 modified polyethylene oxide material, forcing the modified 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.

[0037] The modified PEO film prepared using the method provided by the present invention can achieve multi-point adhesion with the positive or negative electrode layer, allowing the electrode sheets to be in close contact, fully utilizing the flexible electrolyte properties of PEO, and can expand and contract with the positive and negative electrodes during the charging and discharging process, thereby inhibiting the generation of gaps at the rigid interface and causing problems such as poor interface contact and lithium dendrites, thereby improving the service life of the solid-state battery.

[0038] 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. These variations are all within the protection of the present invention.

Claims

1. A method for preparing modified polyethylene oxide, characterized in that: The method comprises: After mixing polyethylene oxide and E12 epoxy resin, performing pulse heating with reciprocating temperature to control the degree of polymerization reaction between the polyethylene oxide and the E12 epoxy resin, and obtaining a modified polyethylene oxide solution; evaporating the polyethylene oxide solution to dryness and rinsing to obtain modified polyethylene oxide; The method specifically includes: Step 1: Add polyethylene oxide and E12 epoxy resin into a reactor, and control the temperature of the reactor between 25° C. and 40° C., add solvent into the reactor, dissolve the solvent, then add hydroquinone, and stir evenly; Step 2, after raising the temperature in the reactor to a first temperature at a heating rate of 1°C / min-3°C / min, methylhexahydrophthalic anhydride is added dropwise to the reactor for a set time; Step 3, lowering the temperature of the solution in the reactor to a second temperature; Step 4, cyclically executing steps 2 and 3 until the amount of the methylhexahydrophthalic anhydride added dropwise to the reactor reaches a preset mass; Step 5: Lower the temperature of the solution in the reactor to 25-40° C. and evaporate the solution at 30-50° C. using a vacuum rotary evaporator to remove the solvent and residual methylhexahydrophthalic anhydride and hydroquinone. Rinse the evaporated material with ethanol to obtain modified polyethylene oxide.

2. The method for preparing modified polyethylene oxide according to claim 1, wherein The mass ratio of the polyethylene oxide to the E12 epoxy resin is 100:1-8:

1.

3. The method for preparing modified polyethylene oxide according to claim 1, wherein The amount of hydroquinone added is 0.1%-0.8% of the total mass of the polyethylene oxide and the E12 epoxy resin.

4. The method for preparing modified polyethylene oxide according to claim 1, wherein The mass of the methylhexahydrophthalic anhydride is 10%-35% of the mass of the E12 epoxy resin.

5. The method for preparing modified polyethylene oxide according to claim 1, wherein The first temperature is 70°C-85°C, and the second temperature is 50°C-65°C.

6. A modified polyethylene oxide, characterized in that The modified polyethylene oxide is prepared by the method for preparing the modified polyethylene oxide according to any one of claims 1 to 5.

7. A solid electrolyte membrane, characterized in that Comprising the modified polyethylene oxide as described in claim 6.

8. A solid-state battery, characterized in that: Comprising the solid electrolyte membrane according to claim 7.

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