Solid-state electrolyte, lithium-based energy storage device and preparation method

Abstract

This invention discloses a solid electrolyte, a lithium-based energy storage device, and a preparation method thereof. The solid electrolyte is obtained by curing an electrolyte solution with an ultraviolet lamp. The electrolyte solution includes polyethylene glycol dimethacrylate, an initiator, and a monomer. The monomer contains fluorosulfonyl groups and ester groups. The presence of fluorosulfonyl groups in the monomer side chains can reduce the crystallinity of the polymer, effectively forming a passivation layer on the surface of the lithium anode, expanding the electrochemical window of the battery, thereby improving the cycle life of the battery. The formed flexible polymer skeleton can increase the compatibility between the electrolyte and the electrode, thereby reducing the interfacial resistance. The passivation layer can uniformly shape the interfacial electric field, regulate the diffusion of lithium ions, thereby effectively suppressing dendrite growth and achieving dense and uniform deposition. The lithium-based energy storage device using the monomer-containing electrolyte of this invention can greatly improve the cycle life of lithium half-cells, significantly improve the utilization rate of lithium metal anodes, effectively reduce the polarization voltage of the battery, and significantly improve the coulombic efficiency of the battery.

Description

Technical Field

[0001] This invention relates to the field of electrolyte technology, and more specifically, to a solid electrolyte, a lithium-based energy storage device, and a method for its preparation. Background Technology

[0002] The challenges posed by traditional energy shortages and environmental pollution have spurred the rapid development of renewable energy, making the development of stable, reliable, and safe energy storage technologies an urgent priority. While traditional lithium-ion batteries dominate the energy storage market due to their superior energy density and cycle stability, their application in large-scale energy storage is limited by cost and safety concerns. Solid-state batteries, which largely avoid the safety issues of traditional batteries and reduce manufacturing costs, have garnered widespread attention. Among these, solid-state lithium-ion batteries, with their high theoretical capacity of lithium anodes, high safety of solid electrolytes, and low assembly costs, have become one of the most promising alternatives to traditional liquid lithium-ion batteries for large-scale industrialization.

[0003] Due to problems such as dendrite growth and solid-liquid incompatibility at the interface between the solid electrolyte and the positive electrode, especially under high-rate charge and discharge conditions, lithium metal anodes often result in low coulombic efficiency, rapid capacity decay, and limited cycle life. In addition, the irreversible deposition / stripping of the anode leads to low utilization of lithium anodes, which also severely limits the energy density of lithium-ion batteries.

[0004] To address the aforementioned issues, researchers have proposed numerous solutions, primarily including: designing three-dimensional current collectors, constructing artificial interface layers, developing suitable electrolyte additives, and constructing compatible electrode-electrolyte interfaces. Among these, the UV-curing electrolyte preparation technology is well-known and widely used in lithium battery manufacturing due to its simplicity, economy, speed, and reliability. Introducing suitable functionalized groups into the polymer side chains can not only preferentially adsorb at the interface, effectively balancing the ion concentration and electric field distribution at the lithium anode interface and achieving uniform lithium deposition, but also regulate the solvation structure of lithium ions in the electrolyte, significantly improving the electrochemical window voltage of the electrolyte. Currently, researchers have reported many effective functionalized groups, mainly including cationic fluorosulfonyl, carboxylic acid, and amide groups. However, the currently developed electrolytes still face the following challenges. First, while fluorosulfonyl and carboxylic acid groups can regulate the solvation structure of lithium ions, they cannot effectively regulate the oxidation potential of lithium ions. For amide groups, the abundant nucleophilic sites can effectively regulate the solvation structure of lithium ions and effectively improve the electrochemical window, but these electrolytes often have poor compatibility with the electrodes and cannot fully play their role in protecting the electrodes. Furthermore, the interface state changes continuously and dynamically during charging and discharging, especially at this rate, where the protective effect on the positive and negative electrode interfaces is highly uncertain, making it impossible to improve the utilization rate of the lithium negative electrode, thus severely limiting the energy density of lithium-ion batteries.

[0005] Therefore, there is an urgent need to develop new functional electrolytes to suppress dendrite growth and solve solid-liquid interface instability, thereby improving battery cycle life.

[0006] Chinese Patent Application 1 (Application No.: 202010381309.5, Application Date: 2020.05.08) discloses a method for preparing a polymer electrolyte and its application in an all-solid-state battery. The polymer electrolyte includes a polymer matrix and a lithium salt composite in the polymer matrix. The polymer electrolyte is formed by in-situ polymerization of materials including small molecule additives, crosslinking agents and the lithium salt in the battery through thermal initiation. The lithium ions in this electrolyte are prone to dendrite growth, the solid-liquid interface is unstable, and the battery cycle life is limited.

[0007] Chinese Patent Application 2 (Application No.: 202280023759.4, Application Date: 2022.01.25) discloses a flame-retardant electrolyte composition, a quasi-solid electrolyte, a solid electrolyte, and a lithium battery. The electrolyte comprises a polymer and a lithium salt, wherein the polymer comprises chains of a polyester of phosphoric acid, and the lithium salt is dissolved or dispersed in the polyester of phosphoric acid. The electrolyte may also contain from 0.1% to 50% by weight of a non-aqueous liquid solvent dispersed in the polyester of phosphoric acid. This battery does not significantly improve cycle life.

[0008] Chinese Patent Application 3 (Application No.: 202280034485.9, Application Date: 2022.03.10) discloses a bipolar electrode comprising a flame-retardant quasi-solid electrolyte or solid electrolyte, a bipolar lithium battery, and a manufacturing method thereof. The battery comprises a conductive material foil having two opposing main surfaces, wherein one or both main surfaces are optionally coated with a layer of graphene or expanded graphite material having a thickness from 5 nm to 50 μm; and (b) a negative electrode layer and a positive electrode layer, respectively disposed on the two main surfaces, wherein the positive electrode layer comprises particles of a cathode active material and a mixture of a quasi-solid electrolyte or solid electrolyte, and the electrolyte comprises a polymer, said polymer being a polymerized or cross-linked product of a reactive additive, wherein the reactive additive comprises (i) a polymerizable first liquid solvent, (ii) an initiator or curing agent, and (iii) a lithium salt. A bipolar battery comprising more than one bipolar electrode connected in series is also provided, wherein the graphite negative electrode of this battery lacks a passivation layer, is prone to wear, and has a short battery life. Summary of the Invention

[0009] In view of this, on the one hand, the present invention provides a solid electrolyte obtained by curing an electrolyte solution with an ultraviolet lamp. The electrolyte solution comprises: lithium salt, polyethylene glycol dimethacrylate, an initiator, and monomers. The monomers include fluorosulfonyl groups and ester groups, and the structural formula of the monomers is:

[0010]

[0011] Optionally, the lithium salt includes at least one of lithium hexafluorophosphate, lithium bis(trifluoromethanesulfonyl)imide, and lithium bis(fluorosulfonyl)imide;

[0012] And / or, the initiator includes one of lithium bis(oxalato)borate, lithium bis(trifluoromethanesulfonyl)imide, ethylene carbonate, propylene carbonate, and fluoroethylene carbonate.

[0013] Optionally, the lithium salt in the electrolyte has a mass fraction of 10%-30%;

[0014] The mass fraction of polyethylene glycol dimethacrylate in the electrolyte is 40-80%;

[0015] The mass fraction of the initiator in the electrolyte is 1%-3%;

[0016] And / or, the mass fraction of monomers in the electrolyte is 10% to 30%.

[0017] Optionally, the average molecular weight of polyethylene glycol dimethacrylate is 550 to 750.

[0018] On the other hand, the present invention provides a lithium-based energy storage device that uses any of the aforementioned solid electrolytes, including lithium-ion batteries, lithium metal batteries, and lithium-air batteries.

[0019] In another aspect, the present invention provides a method for fabricating a lithium-based energy storage device, comprising the following steps:

[0020] The synthesis of monomers includes the following steps:

[0021] Chlorosulfonyl isocyanate was mixed with antimony trifluoride to obtain the first mixture;

[0022] The first mixture is distilled in a nitrogen atmosphere; the first mixture is heated to a first temperature and stirred for a first time to obtain a fluorosulfonyl isocyanate liquid;

[0023] Fluorosulfonyl isocyanate liquid was dissolved in anhydrous dichloromethane and then added to hydroxyethyl methacrylate to obtain a second mixture;

[0024] The second mixture was placed in ice water and stirred for a second time, then placed in a second temperature environment for a third time to obtain the third mixture.

[0025] The third mixture is subjected to at least two rotary evaporations to obtain the fourth mixture;

[0026] After washing the fourth mixture with anhydrous dichloromethane, the mixture was filtered and dried to obtain the monomer.

[0027] Lithium salt, polyethylene glycol dimethacrylate, initiator and monomer are mixed and dissolved in an organic solvent to obtain an electrolyte;

[0028] Inject the electrolyte into the battery cell;

[0029] The electrolyte and battery cell are cured using ultraviolet lamps and then packaged to obtain lithium-based energy storage devices.

[0030] Optionally, the molar ratio of chlorosulfonyl isocyanate to antimony trifluoride is 3:1 to 4:1.

[0031] Optionally, the first temperature is 70℃-90℃, and the first time is 24h-50h.

[0032] Optionally, the molar ratio of fluorosulfonyl isocyanate to hydroxyethyl methacrylate is 1:1.1 to 1:1.5.

[0033] Optionally, the second time is 0.5h-2h, the second temperature is 18℃ to 25℃, and the third time is 24h-50h.

[0034] Compared with the prior art, the solid electrolyte, lithium-based energy storage device and preparation method provided by the present invention achieve at least the following beneficial effects:

[0035] This invention provides a solid electrolyte, a lithium-based energy storage device, and a preparation method thereof. The solid electrolyte is obtained by curing an electrolyte solution with an ultraviolet lamp. The electrolyte solution includes polyethylene glycol dimethacrylate, an initiator, and a monomer. The monomer contains fluorosulfonyl groups and ester groups. The presence of fluorosulfonyl groups in the monomer side chains can reduce the crystallinity of the polymer, effectively forming a passivation layer on the surface of the lithium anode, expanding the electrochemical window of the battery, thereby improving the cycle life of the battery. The formed flexible polymer skeleton can increase the compatibility between the electrolyte and the electrode, thereby reducing the interfacial resistance. The passivation layer can uniformly shape the interfacial electric field, regulate the diffusion of lithium ions, thereby effectively suppressing dendrite growth and achieving dense and uniform deposition. Compared with electrolytes without monomers, the lithium-based energy storage device using the monomer-containing electrolyte of this invention can greatly improve the cycle life of the lithium half-cell, significantly improve the utilization rate of the lithium metal anode, effectively reduce the polarization voltage of the battery, and significantly improve the coulombic efficiency of the battery.

[0036] Of course, any product implementing this invention does not necessarily need to achieve all of the technical effects described above at the same time.

[0037] Other features and advantages of the invention will become clear from the following detailed description of exemplary embodiments of the invention with reference to the accompanying drawings. Attached Figure Description

[0038] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments of the invention and, together with their description, serve to explain the principles of the invention.

[0039] Figure 1 This is a comparison chart of the linear scan curves of a solid electrolyte lithium-stainless steel pad battery provided by the present invention and batteries of the prior art;

[0040] Figure 2 This is a comparison chart of the rate cycle performance of a lithium iron phosphate / lithium metal half-cell with another solid electrolyte provided by this invention and batteries of the prior art.

[0041] Figure 3 This is a comparison chart of the rate cycle performance of a lithium iron phosphate graphite full battery with another solid electrolyte provided by this invention and batteries of the prior art.

[0042] Figure 4 This is a comparison of the surface morphology of a graphite anode battery with a solid electrolyte provided by this invention and a battery of the prior art after long-cycle testing.

[0043] Figure 5 This is a flowchart of a method for preparing a lithium-based energy storage device provided by the present invention;

[0044] Figure 6 This is a flowchart of another method for preparing a lithium-based energy storage device provided by the present invention. Detailed Implementation

[0045] Various exemplary embodiments of the present invention will now be described in detail with reference to the accompanying drawings. It should be noted that, unless otherwise specifically stated, the relative arrangement, numerical expressions, and values ​​of the components and steps set forth in these embodiments do not limit the scope of the invention.

[0046] The following description of at least one exemplary embodiment is merely illustrative and is in no way intended to limit the invention or its application or use.

[0047] Techniques, methods, and equipment known to those skilled in the art may not be discussed in detail, but where appropriate, such techniques, methods, and equipment should be considered part of the specification.

[0048] In all the examples shown and discussed herein, any specific values ​​should be interpreted as merely exemplary and not as limitations. Therefore, other examples of exemplary embodiments may have different values.

[0049] It should be noted that similar labels and letters in the following figures indicate similar items; therefore, once an item is defined in one figure, it does not need to be discussed further in subsequent figures.

[0050] The present invention provides a solid electrolyte, which is obtained by curing an electrolyte with an ultraviolet lamp. The electrolyte includes: lithium salt, polyethylene glycol dimethacrylate, initiator and monomer, and the monomer includes fluorosulfonyl group and ester group.

[0051] Optionally, the mass fraction of the monomer in the electrolyte is 10% to 30%.

[0052] The mass fraction of monomers in the electrolyte can be 10%, 11%, 11.3%, 11.6%, 12%, 12.7%, 13%, 13.6%, 14%, 14.3%, 14.6%, 15%, 15.7%, 16%, 17%, 18%, 19%, 20%, 21.7%, 22%, 22.5%, 23.4%, 24.5%, 25%, 25.6%, 26%, 26.7%, 28%, or 28%. With 3%, 29%, 29.4%, and 30%, the side chains containing fluorosulfonyl groups can reduce the crystallinity of the polymer and effectively form a passivation layer on the lithium anode surface, expanding the electrochemical window of the battery and thus improving the cycle life of the battery. The flexible polymer skeleton formed by the monomer increases the compatibility between the electrolyte and the electrode, thereby reducing the interfacial resistance. The passivation layer can uniformly shape the interfacial electric field and regulate the diffusion of lithium ions, thereby effectively suppressing dendrite growth and achieving dense and uniform deposition.

[0053] It should be noted that the solid electrolyte provided by this invention uses an ultraviolet (UV) lamp to cure the electrolyte. UV curing technology is a rapid and efficient curing method. During the electrolyte curing process, using a UV lamp can significantly shorten the curing time, thereby improving production efficiency. No chemical agents need to be added during UV curing, reducing solvent evaporation and exhaust emissions, thus reducing environmental pollution. Simultaneously, UV curing requires relatively low energy, contributing to energy conservation. UV curing ensures uniform and thorough curing of the electrolyte, thereby improving product quality and stability. The cured electrolyte exhibits better mechanical strength and chemical stability, meeting the needs of various application scenarios. The UV curing process can be precisely controlled by adjusting parameters such as the power of the UV lamp, irradiation time, and irradiation distance. This makes the curing process more flexible and controllable, helping to meet the curing requirements of different products. The combination of UV curing technology and automated equipment enables continuous production and automated control of the electrolyte, effectively reducing labor costs, improving production efficiency, and also helping to ensure the stability and consistency of product quality.

[0054] Optionally, the lithium salt includes at least one of lithium hexafluorophosphate, lithium bis(trifluoromethanesulfonyl)imide, and lithium bis(fluorosulfonyl)imide.

[0055] It should be noted that the decomposition of lithium salts in the electrolyte produces lithium ions (Li+) and other chemical substances. These lithium ions are transferred between the positive and negative electrodes of the battery, providing a continuous current output. The addition of lithium salts can significantly improve the ion transport performance of the electrolyte, reduce the internal resistance of the battery, and thus improve the overall efficiency of the battery. Ideally, lithium salts should be readily soluble or dissociable in the solvent, allowing the dissociated lithium ions to move smoothly. Lithium salts can maintain the uninterrupted redox reaction in the battery, ensuring normal battery operation. Lithium salts can effectively reduce the evaporation rate of the electrolyte, maintaining the stability and durability of the electrolyte, thereby extending the battery's lifespan. Appropriate amounts of lithium salts can, to some extent, prevent overcharging and over-discharging of the battery. When the battery is overcharged, lithium salts can play a stabilizing role, preventing battery overflow and ensuring safe battery use. The choice and concentration of lithium salts also affect the battery's electrochemical performance, such as voltage, capacity, and cycle stability. For example, lithium hexafluorophosphate (LiPF6) and lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) are the most common lithium salts in liquid electrolytes for lithium batteries, and they are widely used due to a combination of factors including price, viscosity and ionic conductivity.

[0056] Optionally, the lithium salt in the electrolyte has a mass fraction of 10%-30%.

[0057] The specific mass fraction of lithium salt can be 10%, 11%, 11.3%, 11.6%, 12%, 12.7%, 13%, 13.6%, 14%, 14.3%, 14.6%, 15%, 15.7%, 16%, 17%, 18%, 19%, 20%, 21.7%, 22%, 22.5%, 23.4%, 24.5%, 25%, 25.6%, 26%, 26.7%, 28%, 28.3%, 29%, 29.4%, and 30%. When the mass fraction of lithium salt is less than 10%, the low lithium salt content in the electrolyte will lead to a decrease in the conductivity of the electrolyte, which in turn affects the battery capacity. Capacity is the battery's ability to store electrical energy and is an important indicator for evaluating battery performance. When the lithium salt content is insufficient, the ion conduction efficiency of the electrolyte decreases. Low lithium salt content reduces the amount of electricity the battery can store and release during charging and discharging, leading to a decrease in battery capacity. Insufficient lithium salt also accelerates the imbalance of internal chemical reactions, causing faster performance degradation during cycle use. Furthermore, insufficient lithium salt reduces electrolyte stability, increasing the likelihood of thermal runaway. When the lithium salt mass fraction exceeds 30%, excessive lithium salt can destabilize the battery's internal structure, even causing internal short circuits, thus affecting battery safety. Excessive lithium salt also complicates the electrolyte system, disrupting electrolytic cell process parameters, making operation difficult, and affecting current efficiency, leading to increased power consumption. Therefore, a lithium salt mass fraction of 10%-30% in the electrolyte is considered sufficient, and an appropriate amount of lithium salt can, to some extent, prevent overcharging and over-discharging of the battery. When the battery is overcharged, lithium salt plays a stabilizing role, preventing battery overflow and ensuring safe battery use.

[0058] Optionally, the mass fraction of polyethylene glycol dimethacrylate in the electrolyte is 40-80%.

[0059] The specific mass fraction of polyethylene glycol dimethacrylate can be 40%, 41%, 42.3%, 43.6%, 44%, 45.7%, 46%, 47.6%, 48%, 49.3%, 50.6%, 52%, 53.7%, 54%, 55%, 56%, 57%, 59%, 60.7%, 62%, 64.5%, 65.4%, 67.5%, 70%, 71.6%, 72%, 73.7%, 74%, 75.3%, 77%, 78.4%, and 80%. When the mass fraction of polyethylene glycol dimethacrylate is less than 40%, the content of polyethylene glycol dimethacrylate is too low and may not be able to provide sufficient structural support for the electrolyte. This can lead to a brittle electrolyte membrane, making it prone to breakage or deformation. Insufficient polyethylene glycol dimethacrylate (PEGDMA), as a plasticizer, may not fully exert its plasticizing effect, potentially resulting in an electrolyte that is too rigid or difficult to process. Too little PEGDMA can also affect the overall performance of the electrolyte, such as ionic conductivity and electrochemical stability. This may limit the application of the electrolyte in certain specific fields. When the PEGDMA mass fraction is greater than 80%, excessive PEGDMA content can lead to a decrease in the mechanical properties of the electrolyte. For example, too much PEGDMA may make the electrolyte membrane too soft or brittle, reducing its tensile and tear strength. Excessive PEGDMA can also affect the electrical properties of the electrolyte, such as ionic conductivity and electrochemical stability. This may lead to a decline in the performance of the electrolyte, making it unable to meet the requirements of specific applications. Polyethylene glycol dimethacrylate is a flammable and irritating substance. Therefore, when the mass fraction of polyethylene glycol dimethacrylate is 40-80%, an appropriate amount of PEGDMA can optimize the ion conduction pathway of the electrolyte, improve the ion migration rate, and thus improve the electrochemical performance of the electrolyte, giving it higher energy density and power density.

[0060] Optionally, the average molecular weight of polyethylene glycol dimethacrylate is 550 to 750.

[0061] It should be noted that polyethylene glycol dimethacrylate (PEG), as a polymer, can play multiple roles in electrolytes. It can polymerize to form an electrolyte membrane, providing structural support and influencing the electrolyte's mechanical and electrical properties. Furthermore, PEG can also act as a plasticizer in electrolytes, improving their flexibility and plasticity, making them easier to process and apply.

[0062] Optionally, the average molecular weight of polyethylene glycol dimethacrylate (PEGDMA) can be 550, 560, 570, 580, 595, 600, 610, 620, 630, 640, 650, 660, 675, 680, 710, 720, 730, 745, or 750. When the average molecular weight of PEGDMA is less than 550, the average molecular weight is too small. PEGDMA with a low molecular weight may not be able to form a stable electrolyte structure, leading to easy deformation or breakage of the electrolyte during use. Structural instability may also affect the mechanical strength and durability of the electrolyte, reducing its service life. PEGDMA with a low molecular weight may form a low crosslinking density, making the electrolyte membrane too soft and easily deformable. Low crosslinking density may also affect the dimensional and chemical stability of the electrolyte, making it difficult to withstand changes in the external environment. PEGDMA with a low molecular weight may also be overly soluble in the solvent, leading to… The loss of electrolyte components and performance degradation can occur; PEGDMA with too small a molecular weight may limit certain properties of the electrolyte, such as thermal stability and chemical stability; when the average molecular weight of polyethylene glycol dimethacrylate is greater than 750, the average molecular weight is too large, and PEGDMA with an excessively large molecular weight may have reduced solubility in solvents, making it difficult to form a uniform and stable electrolyte solution; poor solubility may also cause the electrolyte components to precipitate or decompose during storage and use, affecting the performance of the electrolyte; PEGDMA with an excessively large molecular weight may form an excessively high crosslinking density, causing the electrolyte membrane to become too rigid and brittle; high crosslinking density may also affect the flexibility and plasticity of the electrolyte, making it difficult to adapt to the application requirements of different shapes and sizes; PEGDMA with an excessively large molecular weight may have lower reactivity, resulting in a reduced reaction rate with other monomers or polymers, which may prolong the electrolyte preparation cycle, increase production costs, and reduce production efficiency.

[0063] Optionally, the initiator includes one of lithium bis(oxalato)borate, lithium bis(trifluoromethanesulfonyl)imide, ethylene carbonate, propylene carbonate, and fluoroethylene carbonate.

[0064] It should be noted that initiators generate reactive intermediates (such as free radicals, anions, and cations) during electrolysis. These reactive intermediates act on monomer molecules to initiate polymerization. By adjusting the amount of initiator, the rate of polymerization can be controlled, thereby adjusting the molecular weight distribution and properties of the polymer.

[0065] Optionally, the initiator in the electrolyte has a mass fraction of 1%-3%.

[0066] The specific mass fraction of the initiator in the electrolyte can be 1%, 1.1%, 1.5%, 1.6%, 2%, 2.7%, 2.3%, and 3%. When the mass fraction of the initiator in the electrolyte is greater than 3%, the amount of active intermediates produced per unit time increases, leading to an excessively fast polymerization rate, which may cause explosive polymerization and make the reaction difficult to control. Excessive initiator also increases chain termination reactions, resulting in a lower molecular weight of the final polymer. Too much initiator may also lead to uneven polymer structure, affecting the physical and chemical properties of the product. Some initiators may decompose under high temperature or light conditions, producing toxic gases or flammable and explosive substances, increasing safety hazards. When the mass fraction of the initiator in the electrolyte is less than 1%, the insufficient initiator results in a slow polymerization rate, leading to low production efficiency. Monomers may not be fully converted into polymers, causing raw material waste. Due to insufficient initiator, chain growth reactions continue, potentially leading to an excessively high polymer molecular weight, affecting the product's processing and performance. The polymerization reaction may be incomplete, resulting in unreacted monomers or initiators remaining in the product, affecting product quality and safety. Therefore, the mass fraction of the initiator in the electrolyte should be 1%-3%, with an appropriate initiator content.

[0067] It is understood that the solid electrolyte provided by this invention comprises a lithium salt, polyethylene glycol dimethacrylate, an initiator, and a monomer. The monomer contains fluorosulfonyl groups and ester groups. The presence of fluorosulfonyl groups in the monomer side chains can reduce the crystallinity of the polymer, effectively forming a passivation layer on the surface of the lithium anode, expanding the electrochemical window of the battery, thereby improving the cycle life of the battery. The formed flexible polymer skeleton can increase the compatibility between the electrolyte and the electrode, thereby reducing the interfacial resistance. The passivation layer can uniformly shape the interfacial electric field, regulate the diffusion of lithium ions, thereby effectively suppressing dendrite growth and achieving dense and uniform deposition. Compared with electrolytes without monomers, lithium-based energy storage devices using the monomer-containing electrolyte of this invention can significantly improve the cycle life of lithium half-cells, significantly improve the utilization rate of lithium metal anodes, effectively reduce the polarization voltage of the battery, and significantly improve the coulombic efficiency of the battery.

[0068] This invention also provides a method for preparing a lithium-based energy storage device, comprising the following steps:

[0069] S1: Monomer synthesis, which includes the following steps:

[0070] S11: Chlorosulfonyl isocyanate is mixed with antimony trifluoride to obtain the first mixture;

[0071] S12: Distill the first mixture under a nitrogen atmosphere; S13: Heat the first mixture to a first temperature and stir for a first time to obtain a fluorosulfonyl isocyanate liquid;

[0072] S14: Dissolve fluorosulfonyl isocyanate liquid in anhydrous dichloromethane and add it to hydroxyethyl methacrylate to obtain a second mixture;

[0073] S15: After stirring the second mixture in ice water for a second time, place it in a second temperature environment for a third time to obtain the third mixture;

[0074] S16: The third mixture is subjected to at least two rotary evaporations to obtain the fourth mixture;

[0075] S17: After washing the fourth mixture with anhydrous dichloromethane, filter and dry to obtain the monomer;

[0076] S2: Lithium salt, polyethylene glycol dimethacrylate, initiator and monomer are mixed and dissolved in an organic solvent to obtain an electrolyte;

[0077] S3: Inject electrolyte into the battery cell;

[0078] S4: Use ultraviolet lamps to cure the electrolyte and the battery cell, and then encapsulate them to obtain a lithium-based energy storage device.

[0079] Optionally, the molar ratio of chlorosulfonyl isocyanate to antimony trifluoride is 3:1 to 4:1.

[0080] Optionally, the molar ratio of fluorosulfonyl isocyanate to hydroxyethyl methacrylate is 1:1.1 to 1:1.5.

[0081] It should be noted that a molar ratio of chlorosulfonyl isocyanate to antimony trifluoride of 3:1 to 4:1, and a molar ratio of fluorosulfonyl isocyanate to hydroxyethyl methacrylate of 1:1.1 to 1:1.5, ensures a high yield of the final 2-(1-fluorosulfonylamino)vinyl-oxy-ethyl methacrylate (monomer), allowing the reaction to proceed more completely and thus increasing the yield of the target product. Appropriate molar ratios can reduce the formation of unnecessary byproducts. Reasonable molar ratios ensure that each reactant is fully utilized, avoiding unnecessary waste. In complex reaction systems, multiple competing reaction pathways may exist. By adjusting the molar ratio, reaction conditions can be optimized, making the target product the major product and improving reaction selectivity. Appropriate molar ratios help determine optimal reaction temperature, pressure, and catalyst dosage. Optimizing these conditions can further improve reaction efficiency and product quality. Precise control of the molar ratio can optimize the reaction process and reduce unnecessary energy consumption. For example, reducing unnecessary heating or cooling steps during synthesis lowers energy consumption. Controlling the molar ratio ensures the reaction proceeds within a safe range, reducing the risk of accidents.

[0082] Optionally, the first temperature is 70℃-90℃, and the first time is 24h-50h.

[0083] For example, the first temperature can be 70℃, 71℃, 72℃, 73℃, 74℃, 75.4℃, 76.8℃, 79℃, 81.2℃, 83.6℃, ​​87.8℃, and 90℃. When the first temperature is higher than 90℃, the temperature is too high, and the reactants react violently in the high-temperature zone, causing macromolecules to continuously break down and release more heat, making the temperature even higher. This vicious cycle may lead to a runaway temperature accident. Too high a temperature can easily result in a low yield and increase production costs. When the first temperature is lower than 70℃, the temperature is too low, which can make it difficult to start the reaction or slow down the reaction rate, thus affecting product quality and yield. If the temperature is too low, the reactants cannot react fully, and the accumulated energy is difficult to release, which can easily cause an explosion accident. Therefore, the first temperature is 70℃-90℃. The appropriate temperature ensures a full reaction while maintaining a high yield and reducing production costs.

[0084] The initial reaction time can be 24h, 25h, 26h, 27h, 28h, 29h, 30h, 31h, 32h, 33h, 34h, 35h, 36h, 37h, 38h, 39h, 40h, 41h, 42h, 43h, 44h, 45h, 46h, 47h, 48h, 59h, and 50h. When the initial reaction time is less than 24h, the reaction time is too short, resulting in insufficient precipitation of the target substance, incomplete reaction, and low yield. When the initial reaction time is greater than 50h, the reaction time is too long, and the target substance may undergo side reactions due to the excessively long reaction time, which can also easily lead to a low yield. Therefore, when the initial reaction time is between 24h and 50h, the reaction time is sufficient, more target substance is precipitated, and the reaction is complete.

[0085] Optionally, the second time is 0.5h-2h, the second temperature is 18℃ to 25℃, and the third time is 24h-50h.

[0086] For example, the second reaction time can be 0.5h, 0.6h, 0.7h, 0.8h, 0.9h, 1.0h, 1.1h, 1.2h, 1.3h, 1.4h, 1.5h, 1.6h, 1.7h, 1.8h, 1.9h, and 2h. When the second reaction time is less than 0.5h, the reaction time is too short, the target substance is precipitated too little, the reaction is incomplete, and the yield is low. When the second reaction time is greater than 2h, the reaction time is too long, and the target substance may undergo side reactions due to the excessive reaction time, which can also easily lead to a low yield. Therefore, when the first reaction time of the second reaction is 0.5h-2h, the reaction time is sufficient, more target substance is precipitated, and the reaction is complete.

[0087] For example, the second temperature can be 18℃, 19℃, 20℃, 21℃, 22℃, 23℃, 24℃, and 25℃. When the second temperature is greater than 25℃, the reaction temperature exceeds room temperature. Excessive temperature causes the reactants to react violently in the high-temperature zone, leading to continuous breakage of macromolecules and the release of more heat, further increasing the temperature. This vicious cycle could result in a runaway reaction. Excessively high temperatures also lead to low yields and increased production costs. When the second temperature is less than 18℃, the temperature is below room temperature. Excessively low temperatures can make it difficult to start the reaction or slow down the reaction rate, thus affecting product quality and yield. If the temperature is too low, the reactants cannot react fully, and the accumulated energy is difficult to release, potentially causing an explosion. Therefore, the second temperature should be between 18℃ and 25℃. Appropriate temperatures ensure a sufficient reaction while maintaining a high yield and reducing production costs.

[0088] For example, the third reaction time can be 24h, 25h, 26h, 27h, 28h, 29h, 30h, 31h, 32h, 33h, 34h, 35h, 36h, 37h, 38h, 39h, 40h, 41h, 42h, 43h, 44h, 45h, 46h, 47h, 48h, 59h, and 50h. When the third reaction time is less than 24h, the reaction time is too short, the target substance is precipitated too little, the reaction is incomplete, and the yield is low. When the third reaction time is greater than 50h, the reaction time is too long, and the target substance may undergo side reactions due to the excessive reaction time, which can also easily lead to a low yield. Therefore, when the third reaction time is between 24h and 50h, the reaction time is sufficient, more target substance is precipitated, and the reaction is complete.

[0089] It should be noted that during the above reaction process, after continuous stirring for 24 hours, fluorosulfonyl isocyanate liquid begins to precipitate. If the reaction is continuously stirred for more than 50 hours, the yield will gradually decrease. Excessively high temperature can also affect the product yield and generate unnecessary byproducts.

[0090] Example 1

[0091] Lithium bis(fluorosulfonyl)imide (LiFSI) was used as the lithium salt in the electrolyte, with a mass fraction of 10%, a monomer mass fraction of 10%, an initiator mass fraction of 1.5%, and a polyethylene glycol dimethacrylate mass fraction of 78.5%. The above reagents were completely dissolved in an organic solvent, which in this example was acetone, to obtain an electrolyte solution. The electrolyte solution was then slowly poured into a mold with dimensions of 8cm × 8cm. The mold contained a lithium iron phosphate positive electrode sheet with active material. The mold was then placed in a vacuum oven at 40°C for 15 minutes and then cured under an ultraviolet lamp for 10 minutes to obtain Example 1.

[0092] Example 2

[0093] Lithium bis(fluorosulfonyl)imide (LiFSI) was used as the lithium salt in the electrolyte, with a mass fraction of 20%, a monomer mass fraction of 20%, an initiator mass fraction of 1.5%, and a polyethylene glycol dimethacrylate mass fraction of 58.5%. The above reagents were dissolved in an organic solvent, which in this example was acetone, to obtain an electrolyte solution. The electrolyte solution was then slowly poured into a mold with dimensions of 8cm × 8cm. The mold contained a lithium iron phosphate positive electrode sheet with active material. The mold was then placed in a vacuum oven at 40°C for 15 minutes, followed by curing under an ultraviolet lamp for 10 minutes to obtain Example 2.

[0094] Example 3

[0095] Lithium bis(fluorosulfonyl)imide (LiFSI) was used as the lithium salt in the electrolyte, with a mass fraction of 30%, a monomer mass fraction of 30%, an initiator mass fraction of 1.5%, and a polyethylene glycol dimethacrylate mass fraction of 38.5%. To prepare the electrolyte of Example 3, the above reagents were dissolved in an organic solvent, specifically acetone, to obtain the electrolyte. The electrolyte was then slowly introduced into a mold measuring 8cm × 8cm. The mold contained a lithium iron phosphate positive electrode sheet with active material. The mold was then placed in a 40°C vacuum oven for 15 minutes, followed by curing under ultraviolet light for 10 minutes to obtain Example 3.

[0096] As a comparative example, a solid electrolyte from the prior art is used. This electrolyte includes a lithium salt, polyethylene glycol dimethacrylate, and an initiator. Lithium bis(fluorosulfonyl)imide (LiFSI) is used as the lithium salt in the electrolyte, with a mass fraction of 30%. The initiator has a mass fraction of 1.5%, and the polyethylene glycol dimethacrylate has a mass fraction of 68.5%. The above reagents are dissolved in an organic solvent, which in this example is acetone, to obtain an electrolyte. The electrolyte is then slowly introduced into a mold with dimensions of 8cm × 8cm. The mold includes a lithium iron phosphate positive electrode containing active materials. The mold is then placed in a vacuum oven at 40°C for 15 minutes, followed by curing under an ultraviolet lamp for 10 minutes to obtain the comparative example.

[0097] Experiments on the effect of different mass fractions of monomers on the electrochemical window of lithium-ion batteries:

[0098] Using a 0.25 mm thick lithium sheet and a 1 mm thick stainless steel pad (SS) as electrodes, electrolytes from Examples 1, 2, 3, and the comparative example were taken respectively. The solutions were then slowly poured into a mold, placed in a 40°C vacuum oven for 15 minutes, and finally cured under ultraviolet light for 10 minutes to obtain an electrolyte membrane. The electrolyte membranes were then assembled into coin-type lithium / SS symmetric cells. The electrochemical window of the cells was tested at 0.1 mV / s and 25°C, yielding the following results: Figure 1 The linear scan curve shown is composed of... Figure 1 It can be seen that, under the conditions of 0.1 mv / s and 25 °C, the electrochemical window of Example 3 reached 5.24 V, which is much higher than the 4.52 V of the comparative example.

[0099] Experiments on the effect of different mass fractions of monomers on the cycle performance of lithium-ion batteries:

[0100] Using lithium iron phosphate as the positive electrode, electrolytes from Examples 1, 2, 3, and the comparative example were taken respectively. The solutions were slowly poured into a mold, then placed in a vacuum oven at 40°C for 15 minutes, and finally cured under ultraviolet light for 10 minutes to obtain a positive electrode + electrolyte composite film. A positive electrode sheet with a thickness of 14 mm and a negative electrode sheet with a thickness of 0.25 mm were used. The cycle life and coulombic efficiency of the battery were tested under the conditions of 0.2C and 25°C. The test results are as follows. Figure 2 As shown, by Figure 2 It can be seen that after 500 cycles, the battery capacity decay rate using the comparative electrolyte (i.e., the electrolyte without monomers) is significantly higher than that of the electrolyte provided by the present invention. The average coulombic efficiency of the electrolytes in Examples 1, 2, and 3 is also higher than that of the electrolyte in the comparative example.

[0101] Using lithium iron phosphate as the positive electrode, electrolytes from Examples 1, 2, 3, and the comparative example were taken respectively. The solutions were slowly poured into a mold, then placed in a vacuum oven at 40°C for 15 minutes, and finally cured under ultraviolet light for 10 minutes to obtain a positive electrode + electrolyte composite membrane. A 14mm positive electrode sheet and a graphite negative electrode sheet were taken, and the cycle life and coulombic efficiency of the battery were tested under 0.2C and 25°C conditions. The test results are as follows. Figure 3 As shown, by Figure 3 It can be seen that after 500 cycles, the full-cell capacity decay rate of the electrolyte in the same comparative example, i.e., the electrolyte without monomers, is significantly higher than that of the solid electrolyte provided by the present invention. The average coulombic efficiency of the electrolytes in Examples 1, 2, and 3 is also higher than that of the electrolyte in the comparative example.

[0102] Comparative analysis of the morphological characteristics of graphite anodes after long-term cycling:

[0103] Full cells using lithium iron phosphate as the positive electrode and graphite as the negative electrode in Examples 1, 2, 3, and the comparative example were disassembled after 500 cycles. The morphology of the corresponding graphite negative electrode was observed under a scanning electron microscope. Figure 4 It can be seen that the graphite surface smoothness of the full cells in Examples 1, 2 and 3 of the present invention is better than that of the graphite surface smoothness of the full cells in the comparative examples, indicating that the added monomer has a certain effect on protecting the graphite negative electrode.

[0104] Example 4

[0105] The present invention also provides a lithium-based energy storage device, which utilizes any of the aforementioned solid electrolytes, including lithium-ion batteries, lithium metal batteries, and lithium-air batteries.

[0106] It is understood that the solid electrolyte and lithium-based energy storage device provided by this invention include a electrolyte comprising polyethylene glycol dimethacrylate, an initiator, and a monomer. The monomer contains fluorosulfonyl groups and ester groups. The presence of fluorosulfonyl groups in the monomer side chains can reduce the crystallinity of the polymer, effectively forming a passivation layer on the surface of the lithium anode, expanding the electrochemical window of the battery, thereby improving the cycle life of the battery. The formed flexible polymer skeleton can increase the compatibility between the electrolyte and the electrode, thereby reducing the interfacial resistance. The passivation layer can uniformly shape the interfacial electric field, regulate the diffusion of lithium ions, thereby effectively suppressing dendrite growth and achieving dense and uniform deposition. Compared with electrolytes without monomers, the lithium-based energy storage device using the monomer-containing electrolyte of this invention can greatly improve the cycle life of lithium batteries, significantly improve the utilization rate of lithium metal anodes, effectively reduce the polarization voltage of the battery, and significantly improve the coulombic efficiency of the battery.

[0107] Example 5

[0108] To synthesize the monomer, 169.9 g of chlorosulfonyl isocyanate (1200 mmol) was slowly added to a two-necked round-bottom flask containing 53.63 g of antimony trifluoride (300 mmol). After stirring and mixing, a first mixture was obtained. The flask containing the first mixture was connected to a distillation reflux apparatus in a nitrogen atmosphere. The flask was then placed under a reaction condition of 90 degrees Celsius and stirred continuously for 24 hours to obtain a transparent, strongly acidic fluorosulfonyl isocyanate liquid product with a yield of over 70%.

[0109] Take the freshly obtained fluorosulfonyl isocyanate liquid (500 mmol), dissolve it in an appropriate amount of anhydrous dichloromethane, and then slowly add it in small amounts several times through a dropper to a 250 mL two-necked flask containing hydroxyethyl methacrylate (750 mmol). After thorough mixing, a second mixture is obtained. First, place the flask containing the second mixture in an ice-water environment and stir for 2 hours, then react at room temperature for 24 hours. Finally, a transparent third mixture is obtained. After three rotary evaporations, a fourth mixture is obtained. After washing with anhydrous dichloromethane, filter, and dry, a white crystalline monomer is finally obtained.

[0110] S2: Lithium salt, polyethylene glycol dimethacrylate, initiator and monomer are mixed and dissolved in an organic solvent to obtain an electrolyte;

[0111] S3: Inject electrolyte into the battery cell;

[0112] S4: Use ultraviolet lamps to cure the electrolyte and the battery cell, and then encapsulate them to obtain a lithium-based energy storage device.

[0113] Example 6

[0114] In the synthesis of the monomer, 127.4 g of 900 mmol of chlorosulfonyl isocyanate was first slowly added to a two-necked round-bottom flask containing 53.63 g of 300 mmol of antimony trifluoride. After stirring and mixing, a first mixture was obtained. The flask containing the first mixture was connected to a distillation reflux apparatus in a nitrogen environment. Then, the flask was placed under a reaction condition of 80 degrees Celsius and the reaction was continuously stirred for 48 hours to obtain a transparent, strongly acidic fluorosulfonyl isocyanate liquid product with a yield of over 90%.

[0115] Take the freshly obtained fluorosulfonyl isocyanate liquid (500 mmol), dissolve it in an appropriate amount of anhydrous dichloromethane, and then slowly add it in small amounts several times through a dropper to a 250 mL two-necked flask containing hydroxyethyl methacrylate (550 mmol). After thorough mixing, a second mixture is obtained. First, place the flask containing the second mixture in an ice-water environment and stir for 1 hour, then react at room temperature for 48 hours. Finally, a transparent third mixture is obtained. After three rotary evaporations, a fourth mixture is obtained. After washing with anhydrous dichloromethane, filter, and dry, a white crystalline monomer is finally obtained.

[0116] It should be noted that liquid fluorosulfonyl isocyanate must be stored in a sealed container under cold conditions.

[0117] Example 7

[0118] To synthesize the monomer, 148.6 g of chlorosulfonyl isocyanate (1050 mmol) was slowly added to a two-necked round-bottom flask containing 53.63 g of antimony trifluoride (300 mmol). After stirring and mixing, a first mixture was obtained. The flask containing the first mixture was connected to a distillation reflux apparatus in a nitrogen atmosphere. The flask was then placed under a reaction condition of 70 degrees Celsius and stirred continuously for 50 hours to obtain a transparent, strongly acidic fluorosulfonyl isocyanate liquid product.

[0119] Take the freshly obtained fluorosulfonyl isocyanate liquid (500 mmol), dissolve it in an appropriate amount of anhydrous dichloromethane, and then slowly add it in small amounts several times through a dropper to a 250 mL two-necked flask containing hydroxyethyl methacrylate (600 mmol). After thorough mixing, a second mixture is obtained. First, place the flask containing the second mixture in an ice-water environment and stir for 0.5 hours, then react at room temperature for 50 hours. Finally, a transparent third mixture is obtained. After three rotary evaporations, a fourth mixture is obtained. After washing with anhydrous dichloromethane, filter, and dry, a white crystalline monomer is finally obtained.

[0120] S2: Lithium salt, polyethylene glycol dimethacrylate, initiator and monomer are mixed and dissolved in an organic solvent to obtain an electrolyte;

[0121] S3: Inject electrolyte into the battery cell;

[0122] S4: Use ultraviolet lamps to cure the electrolyte and the battery cell, and then encapsulate them to obtain a lithium-based energy storage device.

[0123] As can be seen from the above embodiments, the solid electrolyte, lithium-based energy storage device, and preparation method provided by the present invention achieve at least the following beneficial effects:

[0124] This invention provides a solid electrolyte, a lithium-based energy storage device, and a preparation method thereof. The solid electrolyte is obtained by curing an electrolyte solution with an ultraviolet lamp. The electrolyte solution includes polyethylene glycol dimethacrylate, an initiator, and a monomer. The monomer contains fluorosulfonyl groups and ester groups. The presence of fluorosulfonyl groups in the monomer side chains can reduce the crystallinity of the polymer, effectively forming a passivation layer on the surface of the lithium anode, expanding the electrochemical window of the battery, thereby improving the cycle life of the battery. The formed flexible polymer skeleton can increase the compatibility between the electrolyte and the electrode, thereby reducing the interfacial resistance. The passivation layer can uniformly shape the interfacial electric field, regulate the diffusion of lithium ions, thereby effectively suppressing dendrite growth and achieving dense and uniform deposition. Compared with electrolytes without monomers, the lithium-based energy storage device using the monomer-containing electrolyte of this invention can greatly improve the cycle life of the lithium half-cell, significantly improve the utilization rate of the lithium metal anode, effectively reduce the polarization voltage of the battery, and significantly improve the coulombic efficiency of the battery.

[0125] While specific embodiments of the invention have been described in detail by way of examples, those skilled in the art should understand that the examples are for illustrative purposes only and not intended to limit the scope of the invention. Those skilled in the art should understand that modifications can be made to the above embodiments without departing from the scope and spirit of the invention. The scope of the invention is defined by the appended claims.

Claims

1. A solid state electrolyte, characterized by, It is obtained by curing an electrolyte under an ultraviolet lamp. The electrolyte includes: lithium salt, polyethylene glycol dimethacrylate, initiator, and monomer. The monomer includes fluorosulfonyl groups and ester groups. The structural formula of the monomer is: ； The mass fraction of polyethylene glycol dimethacrylate in the electrolyte is 38.5%-58.5%; The mass fraction of the monomer in the electrolyte is 20%-30%.

2. The solid-state electrolyte of claim 1, wherein, The lithium salt includes at least one of lithium hexafluorophosphate, lithium bis(trifluoromethanesulfonyl)imide, and lithium bis(fluorosulfonyl)imide. And / or, the initiator includes one of lithium bis(oxalato)borate, lithium bis(trifluoromethanesulfonyl)imide, ethylene carbonate, propylene carbonate, and fluoroethylene carbonate.

3. The solid-state electrolyte of claim 1, wherein, The lithium salt in the electrolyte has a mass fraction of 10%-30%; The initiator in the electrolyte has a mass fraction of 1%-3%.

4. The solid electrolyte according to claim 1, characterized in that, The average molecular weight of the polyethylene glycol dimethacrylate is 550 to 750.

5. A lithium-based energy storage device, using the solid electrolyte according to any one of claims 1 to 4, characterized in that, This includes lithium-ion batteries, lithium metal batteries, and lithium-air batteries.

6. A method for fabricating a lithium-based energy storage device, characterized in that, Including the following steps: The synthesis of monomers includes the following steps: Chlorosulfonyl isocyanate was mixed with antimony trifluoride to obtain the first mixture; The first mixture is distilled under a nitrogen atmosphere; The first mixture is heated to a first temperature and stirred for a first time to obtain a fluorosulfonyl isocyanate liquid. The fluorosulfonyl isocyanate liquid was dissolved in anhydrous dichloromethane and then added to hydroxyethyl methacrylate to obtain a second mixture. The second mixture is placed in ice water and stirred for a second time, then placed in a second temperature environment for a third time to obtain a third mixture. The third mixture is subjected to at least two rotary evaporations to obtain a fourth mixture; The fourth mixture was washed with anhydrous dichloromethane, filtered, and dried to obtain the monomer. Lithium salt, polyethylene glycol dimethacrylate, initiator and the monomer are mixed and dissolved in an organic solvent to obtain an electrolyte; The electrolyte is injected into the battery cell; The electrolyte and the battery cell are cured using an ultraviolet lamp and then packaged to obtain the lithium-based energy storage device.

7. The method for preparing a lithium-based energy storage device according to claim 6, characterized in that, The molar ratio of the chlorosulfonyl isocyanate to the antimony trifluoride is 3:1 to 4:

1.

8. The method for preparing a lithium-based energy storage device according to claim 6, characterized in that, The first temperature is 70℃-90℃, and the first time is 24h-50h.

9. The method for preparing a lithium-based energy storage device according to claim 6, characterized in that, The molar ratio of the fluorosulfonyl isocyanate to the hydroxyethyl methacrylate is 1:1.1 to 1:1.

5.

10. The method for preparing a lithium-based energy storage device according to claim 6, characterized in that, The second time is 0.5h-2h, the second temperature is 18℃ to 25℃, and the third time is 24h-50h.

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