In-situ solidified electrolyte precursor and preparation method thereof and solid-state lithium ion battery

Abstract

The application provides an in-situ solidified electrolyte precursor liquid, a preparation method thereof and a solid-state lithium ion battery, and relates to the technical field of lithium ion batteries.The method comprises the following steps: (A) dispersing polypropylene glycol or polyethylene glycol and isophorone diisocyanate in an organic solvent through a microfluidic device to form a uniformly dispersed microdroplet system; (B) adding an initiator to initiate a polymerization reaction to form a polymer matrix; (C) sequentially performing hydrogen bond extension treatment and hydrogen bond strengthening treatment on the polymer matrix to obtain a polymer reaction product; and (D) combining the product with an electrolyte component containing lithium salt to prepare the in-situ solidified electrolyte precursor liquid.The above-mentioned precursor liquid can be in-situ crosslinked through heating or standing aging after the completion of battery packaging, a solid-state polymer electrolyte layer in close contact with the positive and negative electrode interfaces is formed, and then the interface impedance is effectively improved, and the transmission efficiency of lithium ions between the electrode and the electrolyte interface is improved.

Description

Technical Field

[0001] This invention relates to the field of lithium-ion battery technology, and in particular to an in-situ solidified electrolyte precursor solution, its preparation method, and a solid-state lithium-ion battery. Background Technology

[0002] Traditional liquid lithium-ion batteries suffer from safety hazards such as flammability, leakage, uncontrolled lithium dendrite growth, and poor electrode / electrolyte interface stability. While solid polymer electrolytes (SPEs) can improve safety, their poor contact with the electrode interface and low room-temperature ionic conductivity make them unsuitable for industrial applications. In-situ polymerization is an ideal solution for constructing quasi-solid-state batteries, enabling seamless electrolyte wetting of the electrodes after battery assembly, improving interfacial compatibility, and enhancing ion transport capabilities.

[0003] Current mainstream in-situ thermal polymerization (THPO) technology has significant drawbacks: high-temperature heating easily damages the electrode interface structure; the polymerization process is uncontrollable, leading to uneven internal solidification; additional initiators are required, which can easily cause premature gelation and deteriorate the electrode / electrolyte interface contact; prolonged high-temperature heating not only consumes a lot of energy but also results in uneven distribution of polymerization products, causing a sharp drop in ionic conductivity. In addition, existing technologies lack in-situ real-time characterization methods to monitor the polymerization process, making it difficult to achieve precise control over the degree of reaction and structural evolution.

[0004] Solid polymer electrolytes (SPEs) offer advantages over rigid inorganic materials, including lower cost, simplified manufacturing processes, and superior electrode-electrolyte interface contact. In-situ polymerization further enhances the adaptability of SPEs for large-scale applications, achieving higher ionic conductivity, better interfacial contact, and improved interfacial compatibility. Research indicates that adjusting the solvation structure of lithium ions helps promote the formation of inorganic-rich cathode electrolyte interphase (CEI) and solid electrolyte interphase (SEI), thereby improving the cycle performance and safety of batteries under high-voltage conditions; this regulation can be achieved by modifying the polymer matrix structure. However, current in-situ solidified electrolytes generally suffer from poor consistency within battery cells. The solidification effect of in-situ solidified electrolytes varies significantly across cells with different chemical systems and capacity specifications, severely hindering mass production adoption.

[0005] Therefore, researching and developing a quasi-solid electrolyte that combines high ionic conductivity with low interfacial impedance has become a key bottleneck that urgently needs to be overcome for the industrialization of solid-state lithium batteries.

[0006] In view of this, the present invention is hereby proposed. Summary of the Invention

[0007] The primary objective of this invention is to provide a method for preparing an in-situ solidified electrolyte precursor solution. This method involves constructing a uniform microdroplet system through microfluidic dispersion, initiating polymerization to form a polymer matrix, and sequentially performing hydrogen bond extension and strengthening treatments. This achieves controllability of the precursor solution reaction process and uniformity of spatial distribution without relying on high-temperature initiation, thus providing a foundation for obtaining a quasi-solid electrolyte layer with both high ionic conductivity and low interfacial impedance.

[0008] The second objective of this invention is to provide an in-situ solidified electrolyte precursor solution.

[0009] The second objective of this invention is to provide a solid-state lithium-ion battery.

[0010] In order to achieve the above-mentioned objectives of the present invention, the following technical solution is adopted: This invention provides a method for preparing an in-situ solidified electrolyte precursor solution, comprising the following steps: (A) Provide a first monomer and a second monomer, and disperse the first monomer and the second monomer in an organic solvent through a microfluidic device to form a uniformly dispersed microdroplet system; The first monomer includes polypropylene glycol or polyethylene glycol, and the second monomer is isophorone diisocyanate. (B) An initiator is added to the microdroplet system to initiate the polymerization reaction between the first monomer and the second monomer to form a polymer matrix; (C) The polymer matrix is ​​subjected to hydrogen bond extension treatment and hydrogen bond strengthening treatment in sequence to obtain polymer reaction products; (D) The polymer reaction product is combined with the lithium salt-containing electrolyte component to form an in-situ solidified electrolyte precursor solution.

[0011] Furthermore, the microfluidic device in step (A) is a flow-focusing chip with a dispersed phase inlet width of 40~100μm, a continuous phase inlet width of 20~80μm, and an outlet width of 20~100μm; In the microfluidic device, the microdroplet size of the first monomer is 20~150μm, and the flow rate of the first monomer is 10~15μL / min; In the microfluidic device, the microdroplet size of the second monomer is 40~120μm, and the flow rate of the second monomer is 5~30μL / min.

[0012] Furthermore, in step (A), the organic solvent is acetone, and the temperature of the organic solvent in the microfluidic system is 50~100℃.

[0013] Furthermore, the initiator in step (B) is a composite initiator; Preferably, the composite initiator is composed of dibutyltin dilaurate and bismuth neodecanoate; More preferably, the mass ratio of dibutyltin dilaurate to bismuth neodecanoate in the composite initiator is 1:(0.3~0.7). Preferably, the amount of the composite initiator added is 0.5~2wt% of the microdroplet system in step (A).

[0014] Furthermore, after step (B) and before step (C), the following steps are also included: The step of adding an organic solvent to the polymer matrix obtained in step (B) to adjust the viscosity of the system to 2~15 cP; Preferably, the organic solution is acetone.

[0015] Furthermore, step (C) hydrogen bond extension treatment includes: adding a short-chain diol to the polymer matrix and reacting it at 50~120°C.

[0016] Preferably, the short-chain diol is selected from at least one of butanediol and propylene glycol.

[0017] More preferably, the amount of the short-chain diol added accounts for 5% to 15% of the total mass of the first monomer and the second monomer.

[0018] Furthermore, step (C) hydrogen bond strengthening treatment includes: after hydrogen bond extension treatment, adding a perfluoroalkyl alcohol to the reaction system and continuing the reaction at 50~120℃ for 10~90 min.

[0019] Preferably, the perfluoroalkyl alcohol is selected from at least one of perfluorohexylpropyl alcohol (TPOH-2), perfluorobutylpropyl alcohol (TPOH-4), and perfluorooctylpropyl alcohol (TPOH-8).

[0020] More preferably, the amount of the perfluoroalkyl alcohol added accounts for 0.5%-1% of the total mass of the first monomer and the second monomer.

[0021] Furthermore, in step (D), the mass ratio of the polymer reaction product to the lithium salt-containing electrolyte component is (3~10):100.

[0022] The present invention provides an in-situ solidified electrolyte precursor solution, which is prepared by the above-described method for preparing in-situ solidified electrolyte precursor solution.

[0023] The present invention provides a solid-state lithium-ion battery comprising a positive electrode, a negative electrode and a solid polymer electrolyte layer located between the two, wherein the solid polymer electrolyte layer is obtained by the above-mentioned in-situ solidified electrolyte precursor liquid through an in-situ crosslinking reaction; After the battery is encapsulated, the in-situ solidified electrolyte precursor solution undergoes an in-situ crosslinking reaction through heating or static aging to form a solid polymer electrolyte layer that is in close contact with the interfaces of the positive and negative electrodes.

[0024] Compared with the prior art, the beneficial effects of the present invention are as follows: The present invention provides a method for preparing an in-situ solidified electrolyte precursor solution. The method involves using a microfluidic device to achieve uniform dispersion of a first monomer and a second monomer in an organic solvent, combined with a polymerization reaction initiated by an initiator, and sequentially subjecting the resulting polymer matrix to hydrogen bond extension and hydrogen bond strengthening treatments. Finally, the polymer matrix is ​​combined with lithium salt electrolyte components to construct a solid polymer electrolyte layer that can be in-situ cross-linked after battery encapsulation and maintains close contact with the positive and negative electrode interfaces. The above method of the present invention ensures the uniformity of the precursor solution structure and the controllability of the reaction process, providing a foundation for obtaining a safe and reliable solid-state lithium-ion battery.

[0025] The in-situ solidified electrolyte precursor provided by the present invention is determined by the preparation method of the precursor. The in-situ solidified electrolyte precursor has good fluidity and storage stability, and after the battery is encapsulated, it can achieve in-situ crosslinking by heating treatment or static aging to form a solid polymer electrolyte layer with close contact with the positive and negative electrode interfaces and a uniform structure.

[0026] The solid-state lithium-ion battery provided by the present invention achieves close interfacial contact and structural adaptive matching between the electrolyte and the positive and negative electrodes by using a solid polymer electrolyte layer formed by in-situ crosslinking of the in-situ solidified electrolyte precursor liquid. This helps to reduce interfacial impedance and improve the transport efficiency of lithium ions between the electrode and electrolyte interface. Attached Figure Description

[0027] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0028] Figure 1 The images show the physical effects of the polymer electrolyte obtained in Example 1 of this invention before and after thermosetting; Figure 2 Solid content retention rates after thermosetting and centrifugation at different speeds for Examples 1, 2 and Comparative Example 1 provided in Experimental Example 1 of the present invention; Figure 3 EIS diagrams of the button batteries assembled in Example 1 and Comparative Example 3 provided for Experimental Example 1 of the present invention; Figure 4 The diagram shows the needle penetration results of the soft-pack battery cells assembled in Examples 1-5 provided in Experimental Example 1 of this invention; Figure 5 The diagram shows the needle penetration results of the assembled soft-pack battery cells of Comparative Examples 1 to 7 provided in Experimental Example 1 of this invention. Detailed Implementation

[0029] The technical solution of the present invention will be clearly and completely described below with reference to the embodiments. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0030] According to one aspect of the present invention, a method for preparing an in-situ solidified electrolyte precursor solution includes the following steps: (A) Provide a first monomer and a second monomer, and disperse the first monomer and the second monomer in an organic solvent through a microfluidic device to form a uniformly dispersed microdroplet system; The first monomer includes polypropylene glycol or polyethylene glycol, and the second monomer is isophorone diisocyanate. (B) An initiator is added to the microdroplet system to initiate the polymerization reaction between the first monomer and the second monomer to form a polymer matrix; (C) The polymer matrix is ​​subjected to hydrogen bond extension treatment and hydrogen bond strengthening treatment in sequence to obtain polymer reaction products; (D) The polymer reaction product is combined with the lithium salt-containing electrolyte component to form an in-situ solidified electrolyte precursor solution.

[0031] The present invention provides a method for preparing an in-situ solidified electrolyte precursor solution. The method involves using a microfluidic device to achieve uniform dispersion of a first monomer and a second monomer in an organic solvent, combined with a polymerization reaction initiated by an initiator, and sequentially subjecting the resulting polymer matrix to hydrogen bond extension and hydrogen bond strengthening treatments. Finally, the polymer matrix is ​​combined with lithium salt electrolyte components to construct a solid polymer electrolyte layer that can be in-situ crosslinked after battery encapsulation and is in close contact with the positive and negative electrode interfaces. Specifically: (1) The present invention disperses the first monomer and the second monomer in an organic solvent through a microfluidic device to form a uniformly dispersed microdroplet system, which is beneficial to improve the spatial distribution uniformity of the monomer in the solvent, thereby improving the uniformity of the subsequent polymerization reaction; wherein, the first monomer is polypropylene glycol or polyethylene glycol, and the second monomer is isophorone diisocyanate. The polymer matrix formed by the reaction of the two has suitable chain segment flexibility and reactivity, which is beneficial to constructing a network structure with both ion transport channels and mechanical support capabilities. (2) The present invention adds an initiator to the microdroplet system to initiate the polymerization reaction, which can achieve controllable crosslinking of monomers under relatively mild conditions and avoid local overheating or phase separation caused by violent reaction. (3) The present invention performs hydrogen bond extension treatment and hydrogen bond strengthening treatment on the polymer matrix in sequence, which can introduce additional hydrogen bond interaction sites on the polymer main chain and enhance the stability and order of the hydrogen bond network. The polymer reaction product obtained by hydrogen bond extension and strengthening treatment is combined with the electrolyte component containing lithium salt. The in-situ solidified electrolyte precursor liquid formed can undergo in-situ crosslinking reaction by heating treatment or static aging after the battery is encapsulated, forming a solid polymer electrolyte layer that is in close contact with the interface of the positive electrode and the negative electrode.

[0032] Specifically, in this invention, hydrogen bond extension treatment (addition of short-chain diols) introduces dense hydroxyl sites on the polymer backbone, enhancing chain flexibility and Li + Coordination ability; subsequent hydrogen bond strengthening treatment (addition of perfluoroalkyl alcohols) utilizes the strong hydrophobicity of fluorocarbon chains to induce microphase separation, forming physical cross-linking anchors and locking the loose hydrogen bond network into a gradient ordered structure. Therefore, the synergistic effect of hydrogen bond extension and hydrogen bond strengthening treatments in this application constructs a bilayer hydrogen bond network with both high ion migration channel density and thermo / mechanical stability, significantly improving electrolyte interface wettability, lithium salt dissociation, and the uniformity of in-situ cross-linking structure.

[0033] In a preferred embodiment of the present invention, the microfluidic device in step (A) is a flow-focusing chip with a dispersed phase inlet width of 40~100μm, a continuous phase inlet width of 20~80μm, and an outlet width of 20~100μm; In the microfluidic device, the microdroplet size of the first monomer is 20~150μm, and the flow rate of the first monomer is 10~15μL / min; In the microfluidic device, the microdroplet size of the second monomer is 40~120μm, and the flow rate of the second monomer is 5~30μL / min.

[0034] In a preferred embodiment of the present invention, the organic solvent in step (A) is acetone, and the temperature of the organic solvent in the microfluidic system is 50~100℃.

[0035] In a preferred embodiment, the present invention uses acetone as an organic solvent and controls the temperature of the organic solvent in the microfluidic process at 50~100℃, which is beneficial to improve the dispersion stability and flowability of the first monomer and the second monomer in the solvent, promote the uniform formation and stable existence of microdroplets, and provide a suitable thermodynamic environment for subsequent polymerization reactions.

[0036] In a preferred embodiment of the present invention, the initiator in step (B) is a composite initiator, which is composed of dibutyltin dilaurate and bismuth neodecanoate; As a preferred embodiment, the present invention employs a composite initiator composed of dibutyltin dilaurate and bismuth neodecanoate, which is beneficial for synergistically regulating the polymerization reaction kinetics between the first monomer and the second monomer, achieving slow release of the reaction rate and controllable process, reducing side reactions, and improving the uniformity and stability of the polymer matrix structure.

[0037] In the preferred embodiment described above, the mass ratio of dibutyltin dilaurate to bismuth neodecanoate in the composite initiator is 1:(0.3~0.7). In a preferred embodiment, the present invention controls the mass ratio of dibutyltin dilaurate to bismuth neodecanoate within the range of 1:(0.3 to 0.7), which is beneficial to exert the synergistic effect of the two metal components in catalytic activity and reaction selectivity, so that the polymerization reaction can proceed smoothly under mild conditions, avoid local burst polymerization or insufficient cross-linking, and thus ensure the uniformity and repeatability of the polymer matrix structure.

[0038] Preferably, the amount of the composite initiator added is 0.5~2wt% of the microdroplet system in step (A).

[0039] In a preferred embodiment of the present invention, after step (B) and before step (C), the method further includes: The step of adding an organic solvent to the polymer matrix obtained in step (B) to adjust the viscosity of the system to 2~15 cP; Preferably, the organic solution is acetone.

[0040] In a preferred embodiment, the viscosity of the system is adjusted to 2-15 cP after step (B) and before step (C), which is beneficial to improving the fluidity and dispersion stability of the polymer matrix, providing a uniform reaction medium environment for subsequent hydrogen bond extension and hydrogen bond strengthening treatments, and also helps to improve its compatibility and uniformity when mixed with lithium salt electrolyte components.

[0041] In a preferred embodiment of the present invention, step (C) hydrogen bond extension treatment includes: adding a short-chain diol to the polymer matrix and reacting it at 50~120°C.

[0042] In a preferred embodiment, the present invention adds short-chain diols to the polymer matrix and performs hydrogen bond extension treatment at 50-120°C, which is beneficial to introduce additional hydroxyl interaction sites on the polymer backbone, expand the scale and density of the hydrogen bond network, enhance the interaction between polymer chain segments, and thus improve the structural ductility and interfacial adaptability of the material.

[0043] Preferably, the short-chain diol is selected from at least one of butanediol and propylene glycol.

[0044] More preferably, the amount of the short-chain diol added accounts for 5% to 15% of the total mass of the first monomer and the second monomer.

[0045] In a preferred embodiment of the present invention, step (C) hydrogen bond strengthening treatment includes: after hydrogen bond extension treatment, adding a perfluoroalkyl alcohol to the reaction system and continuing the reaction at 50~120°C for 10~90 min.

[0046] In a preferred embodiment, the present invention adds a perfluoroalkyl alcohol after hydrogen bond extension treatment and continues the reaction at 50-120°C. This is beneficial to utilize the hydrophobic microphase separation effect of the fluorocarbon chain to construct physical crosslinking anchors in the polymer network, enhance the structural stability and thermal responsiveness of the hydrogen bond network, and thus improve the mechanical strength and structural retention ability of the material under abuse conditions.

[0047] Preferably, the perfluoroalkyl alcohol is selected from at least one of perfluorohexylpropyl alcohol (TPOH-2), perfluorobutylpropyl alcohol (TPOH-4), and perfluorooctylpropyl alcohol (TPOH-8).

[0048] More preferably, the amount of the perfluoroalkyl alcohol added accounts for 0.5% to 1% of the total mass of the first monomer and the second monomer.

[0049] In a preferred embodiment of the present invention, the mass ratio of the polymer reaction product to the lithium salt-containing electrolyte component in step (D) is (3~10):100.

[0050] According to one aspect of the present invention, an in-situ solidified electrolyte precursor solution is provided, wherein the in-situ solidified electrolyte precursor solution is prepared by the above-described method for preparing the in-situ solidified electrolyte precursor solution.

[0051] The in-situ solidified electrolyte precursor provided by the present invention is determined by the preparation method of the precursor. The in-situ solidified electrolyte precursor has good fluidity and storage stability, and after the battery is encapsulated, it can achieve in-situ crosslinking by heating treatment or static aging to form a solid polymer electrolyte layer with close contact with the positive and negative electrode interfaces and a uniform structure.

[0052] According to one aspect of the present invention, a solid-state lithium-ion battery includes a positive electrode, a negative electrode, and a solid polymer electrolyte layer located between the two, wherein the solid polymer electrolyte layer is obtained by the above-mentioned in-situ solidified electrolyte precursor solution through an in-situ crosslinking reaction; After the battery is encapsulated, the in-situ solidified electrolyte precursor solution undergoes an in-situ crosslinking reaction through heating or static aging to form a solid polymer electrolyte layer that is in close contact with the interfaces of the positive and negative electrodes.

[0053] The solid-state lithium-ion battery provided by the present invention achieves close interfacial contact and structural adaptive matching between the electrolyte and the positive and negative electrodes by using a solid polymer electrolyte layer formed by in-situ crosslinking of the in-situ solidified electrolyte precursor liquid. This helps to reduce interfacial impedance and improve the transport efficiency of lithium ions between the electrode and electrolyte interface.

[0054] The technical solution of the present invention will be further described below with reference to the embodiments.

[0055] Example 1 A method for preparing an in-situ solidified electrolyte precursor solution includes the following steps: (a) Raw material preparation:

[0056] (II) Specific preparation method: (1) Polypropylene glycol and isophorone diisocyanate were introduced into acetone at 70°C through a flow focusing microfluidic system at flow rates of 12 μL / min and 15 μL / min, respectively.

[0057] The nozzle height of the microfluidic chip is 20 μm, the inlet width of the dispersed phase is 40 μm, the inlet width of the continuous phase is 20 μm, and the outlet width is 20 μm.

[0058] The droplet size of polypropylene glycol was controlled to be 20 μm, and that of isophorone diisocyanate to be 40 μm. Droplet size was controlled by adjusting the size of the delivery tube, and the acetone temperature was maintained at 70°C, with acetone continuously added during the reaction. After the liquid addition was complete, nitrogen gas was introduced into a three-necked flask at a flow rate of 0.3 L / min, and the mixture was mixed and diffused under heating conditions for 5 hours.

[0059] (2) Add a composite initiator to the system obtained in step (1). The composite initiator is a mixture of dibutyltin dilaurate and bismuth neodecanoate in a mass ratio of 1:0.5. The total amount added is 1.2% of the total mass of the solution system obtained in step (1).

[0060] Maintain the reaction temperature at 70℃ and stir at 400 rpm for 3 hours.

[0061] (3) Add acetone to the system after the reaction in step (2) and adjust the viscosity of the system to 10 cP. Maintain the temperature at 70°C, increase the stirring speed to 1.5 times that in step (2), and continue stirring for 45 minutes.

[0062] (4) Add butanediol to the system obtained in step (3), the amount of which is 10% of the total mass of polypropylene glycol and isophorone diisocyanate. Stir the reaction at 80°C for 1 hour.

[0063] (5) Add perfluorobutylpropyl alcohol (TPOH-4) to the system obtained in step (4), the amount of which is 0.8% of the total mass of polypropylene glycol and isophorone diisocyanate. Continue stirring the reaction at 80°C for 50 minutes.

[0064] (6) Add ethylenediamine to the system obtained in step (5) to adjust the pH to 7.2, then add deionized water, stir rapidly for 10 minutes, centrifuge at 11000 r / min, filter after centrifugation, and take the lower precipitate.

[0065] (7) The precipitate obtained in step (6) is placed in a vacuum oven at 60°C and dried for 6 hours. After drying, it is ground and refined to obtain polymer electrolyte powder (sample A).

[0066] (8) Lithium hexafluorophosphate, 1,2-dimethoxyethane and 1,1,1,3,3-pentafluorobutane are mixed in a mass ratio of 12:88:8 and stirred in a glove box for 2 hours to obtain a lithium salt electrolyte (sample B).

[0067] (9) Mix the sample A obtained in step (7) and the sample B obtained in step (8) at a mass ratio of 7:100 and stir at 5°C for 90 minutes to obtain the polymer electrolyte precursor solution.

[0068] Example 2 A method for preparing an in-situ solidified electrolyte precursor solution includes the following steps: (a) Raw material preparation:

[0069] (II) Specific preparation method: (1) Polyethylene glycol and isophorone diisocyanate were introduced into acetone at 90°C through a flow focusing microfluidic system at flow rates of 10 μL / min and 5 μL / min, respectively.

[0070] The microfluidic chip has a nozzle height of 50 μm, a dispersed phase inlet width of 100 μm, a continuous phase inlet width of 80 μm, and an outlet width of 100 μm.

[0071] The droplet size of polyethylene glycol was controlled to be 100 μm, and that of isophorone diisocyanate to be 120 μm. Droplet size was controlled by adjusting the size of the delivery tube, and the acetone temperature was maintained at 90°C, with acetone continuously added during the reaction. After the liquid addition was complete, nitrogen gas was introduced into the three-necked flask at a flow rate of 0.2 L / min, and the mixture was mixed and diffused under heating conditions for 7 hours.

[0072] (2) Add a composite initiator to the system obtained in step (1). The composite initiator is a mixture of dibutyltin dilaurate and bismuth neodecanoate in a mass ratio of 1:0.3, and the total amount added is 0.8% of the total mass of the system obtained in step (1).

[0073] The reaction temperature was lowered to 65°C, and the reaction was stirred for 3 hours.

[0074] (3) Add acetone to the system after the reaction in step (2) and adjust the viscosity of the system to 15 cP. Maintain the temperature at 65°C, increase the stirring speed to 1.5 times that in step (2), and continue stirring for 60 minutes.

[0075] (4) Add propylene glycol to the system obtained in step (3) in an amount equal to 8% of the total mass of polyethylene glycol and isophorone diisocyanate. Stir the reaction at 110°C for 1 hour.

[0076] (5) Add perfluorooctylpropyl alcohol (TPOH-8) to the system obtained in step (4), the amount of which is 1.0% of the total mass of polyethylene glycol and isophorone diisocyanate. Continue stirring at 110°C for 30 minutes.

[0077] (6) Add ethylenediamine to the system obtained in step (5) to adjust the pH to 6.9, then add deionized water, stir rapidly for 10 minutes, centrifuge at 12000 r / min, filter after centrifugation, and take the lower precipitate.

[0078] (7) The precipitate obtained in step (6) is placed in a vacuum oven at 60°C and dried for 4 hours, and then ground to obtain polymer electrolyte powder (sample A).

[0079] (8) Lithium hexafluorophosphate, 1,2-dimethoxyethane and 1,1,1,3,3-pentafluorobutane are mixed in a mass ratio of 10:90:3 and stirred in a glove box for 1 hour to obtain a lithium salt electrolyte (sample B).

[0080] (9) Mix the sample A obtained in step (7) and the sample B obtained in step (8) at a mass ratio of 5:100 and stir at 3°C ​​for 180 minutes to obtain the polymer electrolyte precursor solution.

[0081] Example 3 A method for preparing an in-situ solidified electrolyte precursor solution includes the following steps: (a) Raw material preparation:

[0082] (II) Specific preparation method: (1) Polypropylene glycol and polyethylene glycol are mixed at a mass ratio of 1:1 as the first monomer, and isofolone diisocyanate (the second monomer) are introduced into acetone at 55°C through a flow focusing microfluidic system at flow rates of 15 μL / min and 28 μL / min, respectively.

[0083] The microfluidic chip has a nozzle height of 30 μm, a dispersed phase inlet width of 70 μm, a continuous phase inlet width of 60 μm, and an outlet width of 70 μm.

[0084] The droplet size of the first monomer was controlled to be 50 μm, and the droplet size of the second monomer was controlled to be 60 μm. The droplet size was controlled by adjusting the size of the delivery tube, and the acetone temperature was maintained at 55°C. Acetone was continuously added during the reaction. After the liquid addition was complete, nitrogen gas was introduced into the three-necked flask at a flow rate of 0.5 L / min, and the mixture was mixed and diffused for 3 hours under heating conditions.

[0085] (2) Add a composite initiator to the system obtained in step (1). The composite initiator is a mixture of dibutyltin dilaurate and bismuth neodecanoate in a mass ratio of 1:0.7. The total amount added is 1.8% of the total mass of the system obtained in step (1). Raise the reaction temperature to 80°C and stir the reaction for 3 hours.

[0086] (3) Add acetone to the system after the reaction in step (2) and adjust the viscosity of the system to 5 cP. Maintain the temperature at 80°C, increase the stirring speed to 1.5 times that in step (2), and continue stirring for 30 minutes.

[0087] (4) Add a hydrogen bond extension agent to the system obtained in step (3). The agent is a mixture of butanediol and propylene glycol in a mass ratio of 1:1, and the amount added is 14% of the total mass of the first monomer and the second monomer. Stir the reaction at 60°C for 1 hour.

[0088] (5) Add a hydrogen bond strengthening agent to the system obtained in step (4). The agent is a mixture of perfluorohexylpropyl alcohol (TPOH-2) and perfluorobutylpropyl alcohol (TPOH-4) in a mass ratio of 1:1. The amount added is 0.6% of the total mass of the first monomer and the second monomer. Continue stirring the reaction at 60°C for 80 minutes.

[0089] (6) Add ethylenediamine to the system obtained in step (5) to adjust the pH to 7.5, then add deionized water, stir rapidly for 10 minutes, centrifuge at 10000 r / min, filter after centrifugation, and take the lower precipitate.

[0090] (7) The precipitate obtained in step (6) was dried in a vacuum oven at 60°C for 8 hours, and then ground to obtain polymer electrolyte powder (sample A).

[0091] (8) Lithium hexafluorophosphate, 1,2-dimethoxyethane and 1,1,1,3,3-pentafluorobutane are mixed in a mass ratio of 13:87:12 and stirred in a glove box for 3 hours to obtain a lithium salt electrolyte (sample B).

[0092] (9) Mix the sample A obtained in step (7) and the sample B obtained in step (8) at a mass ratio of 10:100 and stir at 7°C for 40 minutes to obtain the polymer electrolyte precursor solution.

[0093] Example 4 A method for preparing an in-situ solidified electrolyte precursor solution differs from Example 1 only in that: "the total amount of composite initiator added in step (2) is 0.5 wt% of the total mass of the solution system obtained in step (1)," and all other operating conditions are exactly the same as in Example 1.

[0094] Example 5 A method for preparing an in-situ solidified electrolyte precursor solution differs from Example 1 only in that: "in step (3), acetone is added to the system obtained in step (2) to precisely adjust the viscosity of the system to 2 cP", and all other operating conditions are exactly the same as in Example 1.

[0095] Comparative Example 1 A method for preparing an in-situ solidified electrolyte precursor solution differs from Example 1 only in that: in step (1), a microfluidic device is not used, but polypropylene glycol and isophorone diisocyanate are added to acetone at 70°C at a speed of 500 rpm in the same mass ratio and stirred continuously for 60 minutes to disperse them in acetone; all other operating conditions are exactly the same as in Example 1.

[0096] Comparative Example 2 A method for preparing an in-situ solidified electrolyte precursor solution differs from Example 1 only in that: the total amount of composite initiator added in step (2) is 0.3 wt% of the total mass of the solution system obtained in step (1); all other operating conditions are exactly the same as in Example 1.

[0097] Comparative Example 3 A method for preparing an in-situ solidified electrolyte precursor solution differs from Example 1 only in that: in step (2), a composite initiator is not used, but dibutyltin dilaurate (DBTDL) is added alone, and the amount added is 1.2 wt% of the total mass of the solution system obtained in step (1); all other operating conditions are exactly the same as in Example 1.

[0098] Comparative Example 4 A method for preparing an in-situ solidified electrolyte precursor solution differs from Example 1 only in that step (4) (i.e., hydrogen bond extension treatment) is omitted, butanediol is not added, and all other operations are performed in accordance with Example 1.

[0099] That is, after step (3), directly proceed to step (5) to add hydrogen bond strengthening agent for treatment.

[0100] Comparative Example 5 A method for preparing an in-situ solidified electrolyte precursor solution differs from Example 1 only in that step (5) (i.e., hydrogen bond strengthening treatment) is omitted, perfluorobutylpropyl alcohol (TPOH-4) is not added, and all other operations are performed in accordance with Example 1.

[0101] That is, after step (4), proceed directly to step (6).

[0102] Comparative Example 6 A method for preparing an in-situ solidified electrolyte precursor solution differs from Example 1 only in that: in step (1), the nozzle height of the microfluidic chip is 100 μm, the inlet width of the dispersed phase is 200 μm, the inlet width of the continuous phase is 150 μm, and the outlet width is 180 μm; and the operating parameters are adjusted accordingly so that the droplet size of both polypropylene glycol and isophorone diisocyanate is controlled to be 200 μm, and all other operations are performed according to Example 1.

[0103] Comparative Example 7 A method for preparing an in-situ solidified electrolyte precursor solution, which differs from Example 1 only in that: acetone is not added to the polymer matrix obtained in step (2) to adjust the viscosity, and the viscosity of the unadjusted polymer matrix is ​​3000~8000cp. All subsequent operations are carried out in accordance with Example 1.

[0104] Experimental Example 1 This experimental example tests the performance of the in-situ solidified electrolyte precursor solutions prepared in Examples 1-5 and Comparative Examples 1-7 of the present invention. The specific testing methods are as follows: (1) Electrochemical cycling performance test: The in-situ solidified electrolyte precursor solutions prepared in Examples 1-5 and Comparative Examples 1-7 were assembled into pouch cells, wherein: The positive electrode portion has an NCM811:PVDF:SuperP ratio of 97:1:2 and an areal density of 20 mg / cm³. 2 The negative electrode composition is: graphite: silicon-carbon: PAA: CNT = 83:15:1:1, with an areal density of 10 mg / cm³. 2 The electrolyte is the polymer electrolyte precursor solution of this scheme, and the amount added is 10g per cell.

[0105] The cell cycle retention rate was obtained by cycling each of the above batteries at a cycle rate of 0.5C / 0.5C, a voltage range of 2.5V-4.2V, and at 25°C.

[0106] (2) Needle puncture safety performance test: Using a stainless steel needle with a diameter of 4 mm and a cone angle of 14°, insert the needle into the battery at a rate of 20 mm / s in an environment of 25°C until it penetrates the entire thickness of the cell. Leave the needle in the cell for 1 minute and then remove the needle. Observe for 1 hour whether fire, explosion, smoke or casing rupture occurs. If no such phenomenon occurs, it is judged as "passed".

[0107] (3) Interface charge transfer impedance (EIS) test: Button batteries that had been left to age at rest for 24 hours at 25°C were tested. The frequency range was 0.1 mHz to 5 MHz and the amplitude was 0.5 mV / s. The resulting impedance spectrum was fitted and the charge transfer impedance (Rct) value was extracted, with the unit being mΩ.

[0108] (4) Test of solid content retention rate after thermosetting by centrifugation at different speeds: Electrolyte samples (Φ10 mm discs) that had been heat-cured at 60℃ for 6 hours were placed in a centrifuge and centrifuged at 4000 r / min for 5 minutes at 25℃. After each centrifugation, the surface liquid was wiped off, the samples were weighed, and the solid content retention rate was calculated using the formula "(mass after centrifugation ÷ mass before centrifugation) × 100%". The data listed in Table 1 are the test results at 4000 r / min.

[0109] The specific test results are shown in the attached figures and Table 1 below.

[0110] Figure 1 The images show the actual effects of the polymer electrolyte before and after thermosetting provided in Example 1 for this experimental example.

[0111] in, Figure 1 (a) Actual product image of the polymer electrolyte before thermosetting; Figure 1 (b) Actual effect of the polymer electrolyte after thermosetting.

[0112] Depend on Figure 1As shown in (a), the precursor liquid of the polymer electrolyte obtained in Example 1 before thermosetting is a uniform and transparent liquid with excellent fluidity; while Figure 1 Figure (b) shows the solid polymer electrolyte layer after being heat-cured at 60°C for 6 hours. It exhibits a complete and crack-free solidified state, which directly confirms the effectiveness of the in-situ crosslinking reaction and the integrity of the product structure.

[0113] Figure 2 The solid content retention rates of Examples 1, 2, and Comparative Example 1 after thermosetting and centrifugation at different speeds are shown in this experimental example.

[0114] Depend on Figure 2 As shown in Table 1 below, the solid retention rates of the electrolytes obtained by microfluidic dispersion in Examples 1 and 2 of this application were 98.3% and 95.4%, respectively, which were significantly higher than the 67.2% of the magnetically stirred control group in Comparative Example 1. This directly verifies the decisive role of microfluidic technology in improving the density and spatial uniformity of polymer networks.

[0115] Figure 3 EIS diagrams of the button batteries assembled in Example 1 and Comparative Example 3 provided for this experimental case.

[0116] Depend on Figure 3 It can be seen that the EIS of the gel cell formed by a single initiator is significantly higher than that of the proposed method. Furthermore, impedance analysis shows that the increase in EIS is mainly due to the increase in interfacial impedance, indicating that the single initiator has a very significant impact on the compatibility of the gel electrolyte and electrode interface, with a small portion originating from the increase in bulk resistance. These results confirm that the composite initiator of this invention can construct a more uniform polymer electrode interface compared to a single initiator.

[0117] Figure 4 The diagram shows the needle penetration results of the soft-pack battery cells assembled in Examples 1-5 provided in Experimental Example 1 of this invention; Figure 5 The diagram shows the needle penetration results of the assembled soft-pack battery cells of Comparative Examples 1 to 7 provided in Experimental Example 1 of this invention.

[0118] in, Figure 4 From left to right, the images show the needle penetration results of the soft-pack battery cells assembled according to Embodiments 1-5 of the present invention. Figure 5 The images shown from left to right in the middle are the needle penetration results of the soft-pack battery cells assembled in Comparative Examples 1 to 7 of this invention.

[0119] Depend on Figure 4 , Figure 5As can be seen, none of the cells in Examples 1-5 exhibited any signs of fire, explosion, smoke, or casing rupture, and were therefore deemed "passed"; while Comparative Examples 1-7 all showed signs of severe smoke or casing bulging, and were therefore deemed "failed". This comparative result irrefutably proves that the synergistic technology system of microfluidic dispersion, recombination initiation, and hydrogen bond dual-level regulation of this invention is the core guarantee for achieving the intrinsic safety of solid-state batteries.

[0120] Table 1:

[0121] Based on the above test results, Example 1 of this application achieves optimal performance in all four performance indicators: 97.33% retention rate after 300 cycles, 26.3 mΩ interfacial charge transfer impedance, 98.3% solid content retention rate, and 100% pass rate in needle penetration. These results confirm that the complete technical chain of this application, using PPG (2000) as the first monomer, IPDI as the second monomer, combined with 70℃ microfluidic dispersion, DBTDL and bismuth neodecanoate composite initiation, butanediol extension, and TPOH-4 reinforcement, can simultaneously achieve high structural integrity, reaction controllability, low interfacial impedance, and high safety.

[0122] Example 2, while maintaining high cycling stability and needle penetration rate, showed a slightly higher EIS than Example 1, and a slightly lower solids content retention rate, but still remained within the excellent range. These results indicate that replacing the first monomer with PEG (300), increasing the microfluidic temperature to 90°C, and using TPOH-8 as a reinforcing agent can still maintain the effectiveness of the technical solution.

[0123] Example 3, using a mixture of PPG and PEG monomers, also achieved good technical results. This result demonstrates that the combination of polyethers with different chain lengths and fluorocarbon chain length auxiliaries in this application did not weaken the core performance; on the contrary, it expanded the process window.

[0124] In Example 4, when the amount of composite initiator was reduced to 0.5 wt%, the cycle retention rate and EIS were still significantly better than all comparative examples, and the needle punch passed 100% with a solid content of 94.6%. These results indicate that even at the lower limit of initiator dosage, this method can still ensure the sufficiency of polymerization reaction and network density.

[0125] In Example 5, when the viscosity was adjusted to 2 cP, the cycle retention rate and solid content decreased slightly compared to Example 1, but the needle penetration was still 100% successful and the EIS was 29.7 mΩ (still in the low impedance range). This result confirms that 2 cP is the lowest effective viscosity threshold to ensure the uniformity of additive diffusion and reaction.

[0126] In contrast, Comparative Example 1, lacking a microfluidic device and relying solely on magnetic stirring for monomer dispersion, exhibited severely uneven spatial distribution in the microdroplet system. This led to localized runaway polymerization and increased network porosity gradients, manifested as a precipitous drop in solids content retention, a significant increase in EIS, a drastic reduction in cycle life to 100 cycles, and complete failure of needle penetration. These results directly demonstrate that microfluidic dispersion is a necessary technical means to address the problem of uneven spatial structure.

[0127] In Comparative Example 2, although the total amount of the composite initiator was 0.3 wt%, its catalytic activity was insufficient, leading to incomplete polymerization and a low network crosslinking density. This manifested as a solid content retention rate of only 59.3% and complete failure of needle punching. Although its cycle retention rate showed 98.31%, this high retention rate was based on a fragile structure and could not pass safety verification. This result confirms that the initiator dosage must be in the range of 0.5–2 wt% to balance electrochemical performance and structural safety.

[0128] Comparative Example 3, due to the use of only a single initiator, DBTDL, resulted in reaction kinetic imbalance, inducing localized burst polymerization and phase separation, which in turn led to microscopic inhomogeneity of the polymer network. This manifested as a solid content retention rate of only 60.33%, complete failure of needle punching, and a cycle retention rate of 86.37%. These results demonstrate that a mass ratio of DBTDL to bismuth neodecanoate of 1:(0.3~0.7) is a key parameter for achieving sustained-release catalysis and ensuring network uniformity.

[0129] Comparative Example 4, due to the omission of hydrogen bond extension treatment (no addition of butanediol), resulted in insufficient hydroxyl site density in the polymer backbone, which weakened the chain flexibility and electrode surface spreading ability. This manifested as a significant increase in EIS to 42.1 mΩ, but the solid content retention rate still reached 94.1%, indicating that the backbone polymerization was completed and the interface contact was poor.

[0130] Comparative Example 5, due to the omission of hydrogen bond strengthening treatment (without the addition of TPOH-4), resulted in the loss of physical cross-linking anchor points in the fluorocarbon microregions, thereby reducing the network's thermal stability and mechanical strength. This manifested as complete failure of needle punching and a decrease in solid content retention to 61.3%. This result confirms that the hydrogen bond strengthening step is a decisive feature for structural integrity.

[0131] In Comparative Example 6, the microfluidic droplet size increased to 200 μm, leading to a microreactor size mismatch, which in turn caused the pore size distribution of the polymerization network to widen, resulting in a decrease in solid content retention rate to 81.1% and a cycle retention rate to 88.34%.

[0132] In Comparative Example 7, due to the lack of viscosity control, the initial viscosity of the polymer matrix was as high as 3000~8000 cP, which hindered the diffusion of hydrogen bonding agents in the high-viscosity medium and caused uneven reaction, resulting in insufficient network crosslinking. This was manifested in a sharp drop in cycle retention rate to 64.56% and an increase in EIS to 43.1 mΩ. This result confirms that controlling the viscosity to 2~15 cP is a necessary process control point to ensure the effective implementation of hydrogen bonding engineering.

[0133] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for preparing an in-situ solidified electrolyte precursor solution, characterized in that, Includes the following steps: (A) Provide a first monomer and a second monomer, and disperse the first monomer and the second monomer in an organic solvent through a microfluidic device to form a uniformly dispersed microdroplet system; Wherein, the first monomer includes polypropylene glycol and / or polyethylene glycol, and the second monomer is isophorone diisocyanate; (B) An initiator is added to the microdroplet system to initiate the polymerization reaction between the first monomer and the second monomer to form a polymer matrix; (C) The polymer matrix is ​​subjected to hydrogen bond extension treatment and hydrogen bond strengthening treatment in sequence to obtain polymer reaction products; (D) The polymer reaction product is combined with the lithium salt-containing electrolyte component to form an in-situ solidified electrolyte precursor solution.

2. The method for preparing the in-situ solidified electrolyte precursor solution according to claim 1, characterized in that, The microfluidic device in (A) is a flow-focusing chip with a dispersed phase inlet width of 40~100μm, a continuous phase inlet width of 20~80μm, and an outlet width of 20~100μm; In the microfluidic device, the microdroplet size of the first monomer is 20~150μm, and the flow rate of the first monomer is 10~15μL / min; In the microfluidic device, the microdroplet size of the second monomer is 40~120μm, and the flow rate of the second monomer is 5~30μL / min.

3. The method for preparing the in-situ solidified electrolyte precursor solution according to claim 1, characterized in that, The organic solvent in (A) is acetone, and the temperature of the organic solvent in the microfluidic system is 50~100℃.

4. The method for preparing the in-situ solidified electrolyte precursor solution according to claim 1, characterized in that, The initiator in (B) is a composite initiator.

5. The method for preparing the in-situ solidified electrolyte precursor solution according to claim 4, characterized in that, The composite initiator is composed of dibutyltin dilaurate and bismuth neodecanoate; The mass ratio of dibutyltin dilaurate to bismuth neodecanoate in the composite initiator is 1:(0.3~0.7).

6. The method for preparing the in-situ solidified electrolyte precursor solution according to claim 4, characterized in that, The amount of the composite initiator added is 0.5~2wt% of the microdroplet system in step (A).

7. The method for preparing the in-situ solidified electrolyte precursor solution according to claim 1, characterized in that, After (B) and before step (C), it also includes: The step of adding an organic solvent to the polymer matrix obtained in step (B) to adjust the viscosity of the system to 2~15 cP.

8. The method for preparing the in-situ solidified electrolyte precursor solution according to claim 7, characterized in that, The organic solvent is acetone.

9. The method for preparing the in-situ solidified electrolyte precursor solution according to claim 1, characterized in that, The hydrogen bond extension treatment in (C) includes: adding a short-chain diol to the polymer matrix and reacting it at 50~120°C.

10. The method for preparing the in-situ solidified electrolyte precursor solution according to claim 9, characterized in that, The short-chain diol is selected from at least one of butanediol and propylene glycol.

11. The method for preparing the in-situ solidified electrolyte precursor solution according to claim 9, characterized in that, The amount of the short-chain diol added accounts for 5% to 15% of the total mass of the first monomer and the second monomer.

12. The method for preparing the in-situ solidified electrolyte precursor solution according to claim 1, characterized in that, The hydrogen bond strengthening treatment in (C) includes: after hydrogen bond extension treatment, adding a perfluoroalkyl alcohol to the reaction system and continuing the reaction at 50~120℃ for 10~90 min.

13. The method for preparing the in-situ solidified electrolyte precursor solution according to claim 12, characterized in that, The perfluoroalkyl alcohol is selected from at least one of perfluorohexylpropyl alcohol, perfluorobutylpropyl alcohol, and perfluorooctylpropyl alcohol; The amount of the perfluoroalkyl alcohol added is 0.5% to 1% of the total mass of the first monomer and the second monomer.

14. The method for preparing the in-situ solidified electrolyte precursor solution according to claim 1, characterized in that, In (D), the mass ratio of the polymer reaction product to the lithium salt electrolyte component is (3~10):

100.

15. An in-situ solidified electrolyte precursor solution, characterized in that, The in-situ solidified electrolyte precursor solution is prepared by the preparation method according to any one of claims 1 to 14.

16. A solid-state lithium-ion battery, characterized in that, The device comprises a positive electrode, a negative electrode, and a solid polymer electrolyte layer located between the two, wherein the solid polymer electrolyte layer is obtained by an in-situ crosslinking reaction of the in-situ solidified electrolyte precursor liquid as described in claim 15. After the battery is encapsulated, the in-situ solidified electrolyte precursor solution undergoes an in-situ crosslinking reaction through heating or static aging to form a solid polymer electrolyte layer that is in close contact with the interfaces of the positive and negative electrodes.

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