Structural battery electrolyte with excellent impact resistance and preparation method and application thereof

Abstract

The application relates to a structural battery electrolyte with excellent impact resistance and a preparation method and application thereof, wherein the structural battery electrolyte is prepared by compounding main raw materials such as colloidal nanoparticles, shear thickening additives, lithium salts, fluoroacetonitrile (FAN), polymer precursors, initiators and the like through chemical action. The colloidal nanoparticles account for 2 wt%-30 wt% of the total amount of the electrolyte, the shear thickening additives account for 0.2 wt%-2 wt% of the total amount of the electrolyte, and the lithium salt / FAN=1.0-1.5 M. The application adds colloidal nanoparticles and polymer additives into a fluoroacetonitrile (FAN) solution containing lithium salts, realizes the shear thickening performance of the electrolyte by using the "particle cluster" theory, and further endows the battery with the ability of resisting impact and preventing thermal runaway. The shear thickening electrolyte prepared by the application has excellent impact resistance, high conductivity and excellent stability, provides a new idea for the preparation and optimization of the impact-resistant structural electrolyte, and is favorable for improving the safety of lithium metal batteries.

Description

Technical Field

[0001] This invention belongs to the field of shock-resistant structural battery research technology, specifically relating to a structural battery electrolyte with excellent shock resistance performance, its preparation method, and its application. Background Technology

[0002] Energy is the engine of social development, and developing supporting energy storage technologies is crucial for the efficient utilization of energy. Electrochemical energy storage technology has seen significant development in recent decades, with lithium-ion batteries using graphite as the anode and lithium cobalt oxide (LiCoO2), lithium iron phosphate (LiFePO4), and ternary materials as cathodes being widely applied and developed. However, the theoretical specific capacity of traditional graphite anode materials (372 mAh·g) remains a challenge. -1 The high voltage plateau prevents traditional lithium-ion batteries from further breaking through their specific energy bottleneck (350 Wh·kg⁻¹). -1 Therefore, a lithium metal battery with high theoretical specific capacity and low electrode potential was further proposed.

[0003] However, the application of lithium metal batteries still faces many problems, and related safety issues frequently occur, especially regarding dendrite-induced thermal runaway, which has become a major obstacle to the development of lithium metal batteries. Currently, lithium metal batteries mainly consist of a lithium metal oxide positive electrode, a lithium metal negative electrode, a polyethylene (PE) / polypropylene (PP) porous membrane, and an ether-based electrolyte. In this system, the electrolyte plays a role in ion transport, and the membrane is responsible for separating the positive and negative electrodes to prevent short circuits. However, practice has proven that this system has serious thermal runaway safety hazards. When lithium metal batteries are subjected to external impacts, the membrane is easily deformed and damaged, leading to direct contact between the positive and negative electrodes. Electrons and lithium ions flow rapidly at the short circuit point, causing a rapid rise in local temperature. At high temperatures, the solid electrolyte interphase (SEI) film on the surface of the negative electrode decomposes, exposing highly active metallic lithium, which undergoes a violent exothermic reaction with the electrolyte. The electrolyte decomposes and catalyzes the oxidation reaction of organic solvents, further generating heat, ultimately leading to thermal runaway.

[0004] Therefore, many emerging cutting-edge technologies have placed new demands on lithium metal battery energy storage components beyond electrochemical performance, namely, system-level performance (integration performance). Integration performance requires lithium metal batteries to possess comprehensive properties such as mechanical, thermal management, safety, and environmental adaptability to facilitate effective integration with other components. Among these, the mechanical performance of lithium metal batteries refers to their structural stability and damage resistance when subjected to external forces (such as compression, vibration, and impact). This directly affects the battery's safety, lifespan, and applications. Developing shock-resistant electrolytes is crucial for developing lithium metal batteries with excellent shock-resistant mechanical properties.

[0005] Shear-thickening electrolytes (STEs) are promising materials that can protect lithium metal batteries from impacts, preventing catastrophic consequences such as fires and explosions. STEs are non-Newtonian fluids, exhibiting a low-viscosity liquid state below a critical shear rate, but transitioning to a semi-solid or near-solid state when the applied shear rate reaches a critical value. This "strength increases with strength" characteristic allows STEs to protect batteries from external impacts. Summary of the Invention

[0006] To address the problem of thermal runaway in traditional lithium metal batteries under impact, this invention focuses on liquid electrolytes and gel electrolytes, providing a simple-to-operate, mechanically superior shear-thickened electrolyte for lithium metal batteries, along with its preparation method and applications. By adding colloidal nanoparticles and polymer additives to a lithium salt-containing fluoroacetonitrile (FAN) solution, the shear-thickening properties of the electrolyte are achieved using the "particle cluster" theory, thereby endowing the battery with the ability to resist impact and prevent thermal runaway. The electrolyte prepared by this invention exhibits good electrochemical stability, thermodynamic stability, good ionic conductivity, and excellent mechanical properties.

[0007] The objective of this invention is achieved through the following technical solution:

[0008] A structural battery electrolyte with excellent shock resistance is disclosed. The electrolyte's raw materials include lithium salt, fluoroacetonitrile (FAN), colloidal nanoparticles, and polymer additives. The lithium salt / FAN ratio is 1.0 M to 1.5 M, the colloidal nanoparticles account for 2 wt% to 30 wt%, and the polymer additives account for 0.2 wt% to 2 wt%. 1.0 M to 1.5 M refers to 1.0 mol / L to 1.5 mol / L. For example, 1.3 M lithium salt / FAN means that dissolving lithium salt in FAN yields 1 L of lithium salt / FAN solution, containing 1.3 mol of lithium salt, resulting in a lithium salt molar concentration of 1.3 mol / L.

[0009] Furthermore, the raw materials of the electrolyte also include a polymer precursor and an initiator, wherein the lithium salt / FAN is 1.0 M to 1.5 M, the colloidal nanoparticles account for 2 wt% to 30 wt%, the polymer additives account for 0.2 wt% to 2 wt%, the polymer precursor accounts for 1.6 wt% to 16 wt%, and the initiator accounts for 0.3 wt% to 3 wt%.

[0010] Further, the lithium salt is one or more of lithium hexafluorophosphate (LiPF6), lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), and lithium bis(fluorosulfonyl)imide (LiFSI); the colloidal nanoparticles are fumed silica nanoparticles; and the polymer additives are polyethylene oxide (PEO, Mv=100000~8000000, for example, Mv = 100000, 200000, 300000, 400000, 500000, 600000, 900000, 1000000, 1200000, 2000000, 4000000, 5000000, 8000000) or polyethylene glycol (PEG). One or more of the following: 200, 400), ethylene glycol (EG), polyacrylamide (PAM), polyvinylpyrrolidone (PVP), and sodium carboxymethyl cellulose (CMC).

[0011] Furthermore, the polymer precursor is pentaerythritol tetraacrylate (PETEA); the initiator is 2,2'-azobisisobutyronitrile (AIBN).

[0012] A method for preparing the above-mentioned structural battery electrolyte with excellent shock resistance, wherein the method comprises:

[0013] Step 1: Preparation of electrolyte precursor: Take dry FAN, add lithium salt evenly to it, and stir thoroughly for 4 h with the assistance of a magnetic stirrer to make the lithium salt uniformly dissolved in FAN to obtain solution A; the lithium salt / FAN ratio can be 1.0 M, 1.1 M, 1.2 M, 1.3 M, 1.4 M, or 1.5 M.

[0014] Step 2: Add the vacuum-dried polymer additive to solution A obtained in Step 1, and stir thoroughly at 200 r for 1 h with the assistance of a magnetic stirrer to make the polymer additive dissolve evenly in the solution, thus obtaining solution B;

[0015] Step 3: Add vacuum-dried colloidal nanoparticles to solution B obtained in step 2, and stir thoroughly at 200 r for 2 h with the assistance of a magnetic stirrer to make the colloidal nanoparticles dissolve uniformly in the solution, thus obtaining solution C, which is the structured battery electrolyte, also known as shear-thickening electrolyte.

[0016] Furthermore, the method specifically includes: step two further includes: adding a polymer precursor to solution B and stirring thoroughly at 200 r for 1 h with the assistance of a magnetic stirrer to make it uniformly dissolved;

[0017] Step three also includes: adding an initiator to solution C and stirring at 200 r for 3 minutes to obtain a precursor solution of shear-thickening gel electrolyte;

[0018] Step 4: In-situ thermal curing of shear-thickened gel electrolyte: Assemble LFP / electrolyte / Li coin cells using precursor solution, place them in an oven, heat at 60 ℃ for 5 hours for in-situ curing, and cool to room temperature to obtain the structured battery electrolyte, i.e., shear-thickened gel electrolyte.

[0019] Application of a structural battery electrolyte with excellent shock resistance prepared by the above preparation method in structural batteries.

[0020] Compared with the prior art, the present invention has the following advantages:

[0021] 1. This invention introduces fluoroacetonitrile (FAN) as an electrolyte solvent, which can dissolve lithium salts and effectively improve the solubility of polymer additives (such as PEO) in lithium metal battery electrolytes. This is beneficial for PEO to act as a shear-thickening additive, enhancing the shear-thickening effect of gaseous SiO2 nanoparticles and promoting the growth of Li... + Conduction increases the ionic conductivity of the electrolyte. The specific explanation is as follows:

[0022] (1) The surface of gaseous SiO2 is rich in silanol groups (Si-OH), which can form a hydrogen bond network between particles, giving the system excellent thixotropic and shear thickening behavior. PEO interacts strongly with gaseous SiO2 nanoparticles to form a polymer-bridged silica network, thereby enhancing the shear thickening effect. In addition, the adsorption of PEO on the silica surface will generate a steric hindrance effect, which can effectively prevent SiO2 particles from agglomerating and settling.

[0023] (2) Although using PEO as an additive can effectively improve the shear thickening performance of the gas-phase SiO2 system, PEO is a semi-crystalline polymer. Although the ether oxygen bond (-COC-) in its molecular chain has a certain polarity, its overall crystallinity is high, resulting in poor solubility in common lithium metal battery electrolyte solvents. In order to improve solubility, a highly polar solvent (such as acetonitrile) is usually added as a co-solvent. However, the poor reduction stability, safety issues, and compatibility barriers of acetonitrile with existing electrolyte systems prevent it from being used directly in commercial lithium metal battery electrolytes. Fluoroacetonitrile (FAN) can dissolve lithium salts for the preparation of lithium metal battery electrolytes and can also be used as a solvent to dissolve PEO. Therefore, using fluoroacetonitrile as a shear thickening electrolyte solvent for lithium metal batteries can effectively solve the solubility problem of PEO in the electrolyte. At the same time, the improvement of PEO solubility can effectively promote the shear thickening effect of gas-phase SiO2.

[0024] (3) It is known that the ether group of PEO can form a coordination complex with the charge carrier Li⁺, thereby promoting ion transport and effectively improving the ionic conductivity of shear-thickened electrolytes. By using FAN to increase the solubility of PEO, the ionic conductivity of PEO promoting Li⁺ transport can be further improved. +This increases the transmission capacity, thereby improving conductivity.

[0025] 2. Converting shear-thickening electrolytes into a gel state not only retains their inherent shear-thickening ability but also provides the advantages of gel electrolytes:

[0026] (1) When the battery is subjected to impact, the gel-state shear-thickened electrolyte can effectively avoid the leakage and volatilization problems that may occur with the liquid shear-thickened electrolyte, and reduce the risk of combustion and explosion;

[0027] (2) The mechanical strength of gel shear-thickened electrolyte is higher than that of liquid shear-thickened electrolyte. When the battery is subjected to impact, the use of gel shear-thickened electrolyte can more effectively prevent lithium dendrite puncture, further reducing the risk of short circuit and thermal runaway.

[0028] (3) Gel-state shear-thickening electrolytes can be customized in shape and are suitable for novel designs such as flexible batteries and irregularly shaped batteries. Structural batteries using gel-state shear-thickening electrolytes can be customized in shape according to actual needs to meet different requirements. Attached Figure Description

[0029] Figure 1 This is a flowchart of the preparation process of shear-thickened electrolyte for lithium metal batteries.

[0030] Figure 2 This is an optical photograph of the shear-thickened electrolyte in a lithium metal battery.

[0031] Figure 3 This is a test diagram of the shear rheological properties of a shear-thickened electrolyte in a lithium metal battery.

[0032] Figure 4 This is a charge / discharge cycle diagram of LFP (lithium metal battery) | lithium metal battery shear-thickened electrolyte | Li coin cell battery.

[0033] Figure 5 This is an optical photograph of a shear-thickened gel electrolyte in a lithium metal battery.

[0034] Figure 6 This is a charge / discharge cycle diagram of LFP (lithium metal battery) shear-thickening gel electrolyte (Li coin cell). Detailed Implementation

[0035] The technical solution of the present invention will be further described below with reference to the embodiments, but it is not limited thereto. Any modifications or equivalent substitutions to the technical solution of the present invention without departing from the spirit and scope of the technical solution of the present invention should be covered within the protection scope of the present invention.

[0036] Example 1

[0037] This embodiment provides a simple method for preparing a lithium metal battery electrolyte with shear-thickening properties, such as... Figure 1 As shown, the specific preparation steps are as follows:

[0038] (1) Polymer additives (polyethylene glycol (PEG 200, 400), ethylene glycol (EG)) were placed in a vacuum oven and dried thoroughly at 50 °C for 3 days; vapor-phase nano-SiO2 was placed in a vacuum oven and dried thoroughly at 90 °C for 7 days.

[0039] (2) Molecular sieves were fired in a muffle furnace and heated to 350 °C and held for 180 min. After cooling to a suitable temperature, the molecular sieves were removed and placed in a fluoroacetonitrile (FAN) solution in a glove box filled with argon gas. The solution was left to stand for 48 h to remove water completely.

[0040] (3) Take 4 ml of the dried FAN from (2) and add 1.5 g of lithium salt (lithium hexafluorophosphate (LiPF6), lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), lithium bis(fluorosulfonyl)imide (LiFSI), etc.) evenly to it. Stir thoroughly for 4 h with the assistance of a magnetic stirrer to make the lithium salt uniformly dissolved in the FAN to obtain a lithium salt / FAN dispersion.

[0041] (4) Add vacuum-dried polymer additive powder to the dispersion obtained in (3), and stir thoroughly at 200 r for 1 h with the assistance of a magnetic stirrer to ensure that it is uniformly dissolved in the dispersion, accounting for 0.2 wt%~2 wt% of the total electrolyte;

[0042] (5) Add vacuum-dried fumed nano-SiO2 powder to the dispersion obtained in (4), and stir thoroughly at 200 r for 2 h with the assistance of a magnetic stirrer to ensure that the fumed nano-SiO2 powder is uniformly dissolved in the dispersion, wherein the fumed nano-SiO2 powder accounts for 2 wt%~30 wt% of the total electrolyte.

[0043] (6) After the mixture obtained in (5) is left to stand for a period of time, no solid particles precipitate out in the solution, thus obtaining a stable, uniformly dispersed, and viscous shear-thickening electrolyte (e.g. Figure 2 );

[0044] The shear-thickened electrolyte obtained in (6) was subjected to shear rheological property testing, and the results are as follows: Figure 3 At low shear rates, electrolytes exhibit shear thinning. When the critical shear rate is reached, the electrolyte viscosity increases with the increase of the shear rate, exhibiting shear thickening. When the extremely high shear rate is reached, the electrolyte exhibits shear thinning again. This phenomenon of thinning at low and extremely high shear rates and thickening after the critical shear rate is the shear thickening phenomenon of non-Newtonian fluids.

[0045] A coin cell was assembled using a lithium iron phosphate (LFP) cathode, and a shear-thickened electrolyte obtained in (6) was added to it for charge-discharge testing. The results are as follows: Figure 4 As shown, its capacity is 135 mAh·g at room temperature with a capacity of 1 C. -1 After 80 cycles, it still retains nearly 99% of its capacity, a level that conventional shear-thickening electrolytes cannot achieve.

[0046] Example 2

[0047] This embodiment provides a simple method for preparing a lithium metal battery gel electrolyte with shear-thickening properties. The specific preparation steps are as follows:

[0048] (1) Polymer additives (polyacrylamide (PAM), polyvinylpyrrolidone (PVP), sodium carboxymethyl cellulose (CMC)) were placed in a vacuum oven and dried thoroughly at 50 °C for 3 days. Vaporized nano-SiO2 was placed in a vacuum oven and dried thoroughly at 90 °C for 7 days.

[0049] (2) Molecular sieves were fired in a muffle furnace and heated to 350 °C and held for 180 min. After cooling to a suitable temperature, the molecular sieves were removed and placed in a fluoroacetonitrile (FAN) solution in a glove box filled with argon gas. The solution was left to stand for 48 h to remove water completely.

[0050] (3) Take 4 ml of the dried FAN from (2) and add lithium salt (lithium hexafluorophosphate (LiPF6), lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), lithium bis(fluorosulfonyl)imide (LiFSI), etc.) evenly to it. Stir thoroughly with the help of a magnetic stirrer to dissolve the lithium salt evenly in the FAN to obtain a lithium salt / FAN dispersion.

[0051] (4) Add vacuum-dried polymer additive powder to the dispersion obtained in (3), and stir thoroughly at 200 r for 1 h with the assistance of a magnetic stirrer to ensure that it is uniformly dissolved in the dispersion, accounting for 0.2 wt% of the total electrolyte.

[0052] (5) Add pentaerythritol tetraacrylate (PETEA) to the dispersion obtained in (4), and stir thoroughly at 200 r for 1 h with the assistance of a magnetic stirrer to make PETEA uniformly dissolved, wherein PETEA accounts for 1.6 wt% of the total electrolyte;

[0053] (6) Vacuum-dried fumed nano-SiO2 powder was added to the dispersion obtained in (5), and stirred thoroughly at 200 r for 2 h with the assistance of a magnetic stirrer to ensure that the fumed nano-SiO2 powder was uniformly dissolved in the dispersion, wherein the fumed nano-SiO2 powder accounted for 4 wt% of the total electrolyte.

[0054] (7) Add 2,2'-azobisisobutyronitrile (AIBN) to the dispersion obtained in (6), and stir thoroughly at 200 r for 3 min with the assistance of a magnetic stirrer to make the AIBN uniformly dissolved, wherein the AIBN accounts for 0.3 wt% of the total electrolyte.

[0055] (8) Place the mixture obtained in (7) in an oven and heat at 60 °C for 5 h to fully solidify it. Cool to room temperature to obtain a stable and uniformly dispersed shear-thickening gel electrolyte (e.g. Figure 5 );

[0056] A coin cell was assembled using a lithium iron phosphate (LFP) cathode and the mixed solution obtained in (7) was added to it. The assembled cell was placed in an oven and cured in situ at 60 °C for 5 h, and then cooled to room temperature. Charge-discharge tests were performed on the cell, and the results are as follows. Figure 6 As shown, its capacity is 134 mAh·g at room temperature with a capacity of 1 C. -1 After 40 cycles, it still has nearly 99% capacity retention.

Claims

1. A structural battery electrolyte with excellent shock resistance, characterized in that: The electrolyte raw materials include lithium salt, fluoroacetonitrile (FAN), colloidal nanoparticles, and polymer additives. The lithium salt / fluoroacetonitrile (FAN) ratio is 1.0 M to 1.5 M, the colloidal nanoparticles account for 2 wt% to 30 wt%, and the polymer additives account for 0.2 wt% to 2 wt%. The complete meaning of lithium salt / fluoroacetonitrile (FAN) is: dissolving lithium salt in FAN to obtain 1 L of lithium salt / fluoroacetonitrile (FAN) solution, wherein the lithium salt content is 1.0 to 1.5 mol, and the lithium salt molar concentration is 1.0 M to 1.5 M. The colloidal nanoparticles are fumed silica nanoparticles. The polymer additives are one or more of polyethylene oxide (PEO), polyethylene glycol (PEG), ethylene glycol (EG), polyacrylamide (PAM), polyvinylpyrrolidone (PVP), and sodium carboxymethyl cellulose (CMC). The Mv of the polyethylene oxide (PEO) is 100,000 to 8,000,000.

2. The structural battery electrolyte with excellent shock resistance according to claim 1, characterized in that: The electrolyte raw materials also include polymer precursors and initiators, wherein the lithium salt / FAN ratio is 1.0 M to 1.5 M, the colloidal nanoparticles account for 2 wt% to 30 wt%, the polymer additives account for 0.2 wt% to 2 wt%, the polymer precursors account for 1.6 wt% to 16 wt%, and the initiator accounts for 0.3 wt% to 3 wt%.

3. The structural battery electrolyte with excellent shock resistance according to claim 1, characterized in that: The lithium salt is one or more of lithium hexafluorophosphate (LiPF6), lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), and lithium bis(fluorosulfonyl)imide (LiFSI).

4. A structural battery electrolyte with excellent shock resistance according to claim 2, characterized in that: The polymer precursor is pentaerythritol tetraacrylate (PETEA); the initiator is 2,2'-azobisisobutyronitrile (AIBN).

5. A method for preparing a structural battery electrolyte with excellent impact resistance as described in claim 1 or 3, characterized in that: The method is as follows: Step 1: Preparation of electrolyte precursor: Take dry FAN, add lithium salt evenly to it, and stir thoroughly for 4 h with the assistance of magnetic stirrer to make the lithium salt uniformly dissolved in FAN to obtain solution A; Step 2: Add the vacuum-dried polymer additive to solution A obtained in Step 1, and stir thoroughly at 200 r for 1 h with the assistance of a magnetic stirrer to make the polymer additive dissolve evenly in the solution, thus obtaining solution B; Step 3: Add vacuum-dried colloidal nanoparticles to solution B obtained in step 2, and stir thoroughly at 200 r for 2 h with the assistance of a magnetic stirrer to make the colloidal nanoparticles dissolve uniformly in the solution, thus obtaining solution C, which is the electrolyte of the structural battery.

6. The method for preparing the structural battery electrolyte with excellent shock resistance according to claim 5, characterized in that: The method specifically includes: step two further includes: adding a polymer precursor to solution B, and stirring thoroughly at 200 r for 1 h with the assistance of a magnetic stirrer to make it uniformly dissolved; Step three also includes: adding an initiator to solution C and stirring at 200 r for 3 minutes to obtain a precursor solution of shear-thickening gel electrolyte; Step 4: In-situ thermal curing of shear-thickened gel electrolyte: Assemble LFP / electrolyte / Li coin cells using precursor solution, place them in an oven, heat at 60 ℃ for 5 hours for in-situ curing, and cool to room temperature to obtain the structured battery electrolyte, i.e., shear-thickened gel electrolyte.

7. The application of a structural battery electrolyte with excellent shock resistance prepared by the preparation method of claim 5 or 6 in a structural battery.

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