Solid-state electrolyte and preparation method and application thereof
By using LiAlO2 with a particle size of less than 60 nm to prepare a solid electrolyte with polyacrylonitrile and polyethylene oxide, the problems of low ionic conductivity and poor interfacial compatibility of composite polymer electrolytes were solved, and high ionic conductivity and long-term cycle stability of battery performance were achieved.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- FOSHAN XIANHU LAB
- Filing Date
- 2022-08-23
- Publication Date
- 2026-06-30
Smart Images
Figure CN115395085B_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of battery technology, and specifically relates to a solid electrolyte, its preparation method, and its application. Background Technology
[0002] Rechargeable lithium batteries, or lithium-ion batteries, are recyclable batteries, offering greater environmental friendliness compared to traditional fossil fuels. Rechargeable lithium-ion batteries are widely used in energy storage. With technological advancements, higher performance requirements are being placed on lithium batteries, such as high specific capacity, high safety, and high cycle stability. However, traditional lithium batteries use organic liquids as electrolytes, leading to uncontrolled lithium dendrite growth, which can cause short circuits and thermal runaway. These problems hinder the development of lithium batteries. Compared to liquid electrolytes, solid-state electrolytes offer advantages such as leak resistance, non-flammability, high mechanical strength, and high electrochemical stability. Solid-state electrolytes are categorized into inorganic ceramic electrolytes, solid polymer electrolytes, and composite polymer electrolytes. Inorganic solid-state electrolytes possess excellent ionic conductivity and mechanical strength but cannot achieve tight contact with the solid electrode interface; solid polymer electrolytes are flexible and have good contact with the electrode interface, but their ionic conductivity and mechanical strength are not high; while composite polymer electrolytes combine the advantages of both types and are widely studied.
[0003] Composite polymer electrolytes are composed of inorganic ceramic fillers and high-molecular polymers. The inorganic ceramic fillers can reduce the crystallinity of the polymer, and the interfacial region formed between the inorganic ceramic filler and the polymer is conducive to lithium-ion migration. However, a key problem currently facing composite solid-state electrolytes is their generally low ionic conductivity; the interfacial compatibility between the composite polymer electrolyte and the electrode is also poor, leading to rapid capacity decay in the assembled battery.
[0004] Therefore, there is an urgent need to provide a new solid electrolyte with high ionic conductivity, which, when further assembled into a battery, results in a battery with good cycle performance. Summary of the Invention
[0005] The present invention aims to solve at least one of the technical problems existing in the prior art. To this end, the present invention proposes a solid electrolyte, its preparation method, and its application. The solid electrolyte of the present invention has high ionic conductivity, which can improve the interfacial contact performance between the solid electrolyte and the electrode, and enhance the long-term cycle stability of the battery.
[0006] The inventive concept of this invention is as follows: This invention uses LiAlO2 with a specific particle size (below 60nm) as an inorganic ceramic filler, combined with polyacrylonitrile (PAN) and polyethylene oxide (PEO), so that the prepared solid electrolyte has good ionic conductivity, improves the interfacial contact performance between the solid electrolyte and the electrode, and improves the long-term cycle stability of the battery.
[0007] A first aspect of the present invention provides a solid electrolyte.
[0008] Specifically, a solid electrolyte comprises LiAlO2, polyacrylonitrile, polyethylene oxide, and an organolithium salt; wherein the particle size of the LiAlO2 is less than 60 nm.
[0009] Preferably, the organolithium salt is lithium bis(trifluoromethanesulfonyl)imide.
[0010] Preferably, the particle size of the LiAlO2 is 20-60 nm; more preferably 30-50 nm.
[0011] Preferably, the solid electrolyte comprises, by weight, 4-15 parts LiAlO2, 10-25 parts polyacrylonitrile, 50-75 parts polyethylene oxide, and 5-35 parts organic lithium salt.
[0012] More preferably, the solid electrolyte comprises, by weight, 5-10 parts LiAlO2, 10-20 parts polyacrylonitrile, 60-70 parts polyethylene oxide, and 10-30 parts organic lithium salt.
[0013] A second aspect of the present invention provides a method for preparing a solid electrolyte.
[0014] Specifically, a method for preparing a solid electrolyte includes the following steps:
[0015] The organic lithium salt was dissolved in a solvent, and then LiAlO2, polyacrylonitrile and polyethylene oxide were added. The mixture was stirred to obtain a slurry, which was then dried to obtain the solid electrolyte.
[0016] Preferably, the preparation process of LiAlO2 is as follows: mixing lithium salt and aluminum source with dispersant, then ball milling, drying, and calcining; the rotation speed during the ball milling process is 2800-3500 rpm.
[0017] Preferably, the dispersant is an alcohol; preferably ethanol or propanol.
[0018] Preferably, the lithium salt is Li2CO3.
[0019] Preferably, the aluminum source is Al2O3.
[0020] Preferably, the molar ratio of the lithium salt to the aluminum source is 1:(0.8-1.2), more preferably 1:1.
[0021] Preferably, after the lithium salt and aluminum source are mixed with the dispersant, the total concentration of lithium salt and aluminum source in the dispersant is 2-4.8 mol / L, preferably 3-4.5 mol / L.
[0022] Preferably, the ball milling time is 10-24 hours, more preferably 18-24 hours.
[0023] Preferably, the calcination temperature is 600-850℃, more preferably 600-800℃.
[0024] Preferably, during the calcination process, the temperature is increased from room temperature (5-40℃) to 600-850℃ at a rate of 2-5℃ / min.
[0025] Preferably, the calcination time is 1-4 hours, more preferably 2-4 hours.
[0026] Preferably, the preparation process of LiAlO2 is as follows: Li2CO3 and Al2O3 are mixed with ethanol, then ball-milled at a speed of 2800-3500 rpm for 10-24 hours, dried at 60-80℃ for 8-12 hours, and calcined at 600-850℃ for 1-4 hours.
[0027] Preferably, the stirring process involves heating to 50-60°C and stirring for 8-12 hours.
[0028] Preferably, the solvent is an organic solvent, such as N,N-dimethylformamide.
[0029] Preferably, the ratio of polyethylene oxide to solvent is 1g:(2-30)mL, more preferably 1g:(2-3)mL.
[0030] Preferably, in the slurry, Li + The molar mass ratio of the polyethylene oxide unit to the polyoxyethylene unit is 1:(18-22), preferably 1:(18-20). If the amount of polyethylene oxide is too small, for example, Li + If the molar mass ratio of lithium to polyethylene oxide is 1:15, it will be unfavorable to the growth of lithium dendrites, and the mechanical properties of the solid electrolyte will decrease.
[0031] Preferably, the mass ratio of polyethylene oxide to polyacrylonitrile in the slurry is (3-6):1, more preferably (4-5):1. If the amount of polyethylene oxide is too small, for example, if the mass ratio of polyethylene oxide to polyacrylonitrile is 2:1, the solid electrolyte will be relatively brittle and have weak film-forming properties.
[0032] Preferably, during the drying process of the slurry, the drying temperature is 50-80℃, and the drying time is 36-48 hours. The purpose of drying is to evaporate and remove the solvent. Drying is preferably carried out in a vacuum drying oven.
[0033] Preferably, during the drying process of the slurry, the slurry is coated onto a substrate (e.g., a polytetrafluoroethylene plate) and then dried.
[0034] A third aspect of the present invention provides the application of the above-described solid electrolyte.
[0035] The above-mentioned applications of solid electrolytes in batteries.
[0036] A battery comprising the aforementioned solid electrolyte and a positive electrode.
[0037] Preferably, the preparation process of the positive electrode sheet is as follows: lithium iron phosphate, acetylene black, and polyvinylidene fluoride are dissolved in a solvent, stirred and mixed, coated onto aluminum foil, and placed in a vacuum drying oven to remove the solvent, thereby obtaining the positive electrode sheet.
[0038] Preferably, the weight ratio of lithium iron phosphate, acetylene black, and polyvinylidene fluoride is (5-10):(0.5-2):1.5, more preferably 7:1.5:1.5.
[0039] Preferably, the solvent is N-methylpyrrolidone (NMP).
[0040] Preferably, the ratio of the total weight of lithium iron phosphate, acetylene black, and polyvinylidene fluoride to the amount of solvent is 100 mg: (300-500) μL, more preferably 100 mg: (350-450) μL.
[0041] Preferably, the mixing time is 6-8 hours.
[0042] Preferably, the thickness of the coating on the aluminum foil is 10-120 μm, more preferably 10-100 μm.
[0043] Preferably, the temperature for removing the solvent in the vacuum drying oven is 70-80℃, and the time is 10-12 hours.
[0044] This invention uses LiAlO2 as an inorganic ceramic filler and polyacrylonitrile (PAN) as a polymer additive. The combined effect of these three (LiAlO2, PAN, and polyethylene oxide (PEO)) significantly improves the mechanical, thermodynamic, and electrochemical properties of the resulting solid-state electrolyte. The addition of LiAlO2 reduces the crystallinity of PEO, significantly increasing the ionic conductivity of the solid-state electrolyte. Furthermore, LiAlO2 effectively inhibits lithium dendrite growth, preventing short circuits and explosions, and improves the compatibility between the solid-state electrolyte and the electrodes, thus enhancing the long-term cycle stability of the battery. The solid-state electrolyte of this invention acts as both the electrolyte and the separator, simplifying the assembly process of traditional liquid batteries.
[0045] Compared with the prior art, the beneficial effects of the present invention are as follows:
[0046] (1) The present invention uses LiAlO2 with a specific particle size (below 60nm) as an inorganic ceramic filler, combined with polyacrylonitrile (PAN) and polyethylene oxide (PEO), so that the solid electrolyte has good ionic conductivity, and also improves the interfacial contact performance between the solid electrolyte and the electrode, thereby improving the long-term cycle stability of the battery.
[0047] (2) The present invention prepares LiAlO2 nanoparticles by solid-state synthesis, generating small-sized LiAlO2 as ceramic filler, which effectively increases the interfacial transport area of lithium ions.
[0048] (3) The present invention prepares solid electrolyte by solution casting, which is simple and requires no special equipment; the generated solid electrolyte has good mechanical properties, thermodynamic properties and electrochemical properties, and the solid electrolyte and electrode interface are stable, so that the battery has good cycle stability. Attached Figure Description
[0049] Figure 1 This is a SEM image of LiAlO2 obtained in Example 1 of the present invention;
[0050] Figure 2 This is a SEM image of the solid electrolyte prepared in Example 1 of the present invention;
[0051] Figure 3 The XRD patterns are of the solid electrolytes prepared in Example 1, Comparative Example 1, and Comparative Example 2 of this invention.
[0052] Figure 4 The graph shows the relationship between the ionic conductivity of the solid electrolytes prepared in Example 1, Comparative Example 1, and Comparative Example 2 of this invention and temperature at 30-70℃.
[0053] Figure 5 The solid electrolyte prepared in Comparative Example 2 was assembled into a lithium symmetric battery at 60 °C and 50 μA cm⁻¹. -2 100μA cm -2 Cyclic stability curves under current density gradient;
[0054] Figure 6 The solid electrolyte prepared in Example 1 of this invention was assembled into a lithium symmetric battery at 60°C and 50 μA cm⁻¹. -2 100μA cm -2 Cyclic stability curves under current density gradient;
[0055] Figure 7 The LSV curves (linear sweep voltammetry curves) were obtained by assembling the solid electrolytes of Comparative Example 1, Comparative Example 2 and Example 1 with steel sheets and lithium sheets into batteries.
[0056] Figure 8The performance curve of the battery in Application Example 1 is shown in the cycling curve at 60°C and a current density of 0.5C. Detailed Implementation
[0057] To enable those skilled in the art to more clearly understand the technical solutions described in this invention, the following embodiments are provided for illustration. It should be noted that the following embodiments do not constitute a limitation on the scope of protection claimed by this invention.
[0058] Unless otherwise specified, the raw materials, reagents or devices used in the following examples are available from conventional commercial sources or can be obtained by existing known methods.
[0059] Example 1: Preparation of solid electrolyte
[0060] A solid electrolyte comprising 40 mg LiAlO2, 0.125 g polyacrylonitrile, 0.5 g polyethylene oxide, and 0.16 g organic lithium salt.
[0061] The preparation process of LiAlO2 is as follows: 15 mmol each of Li2CO3 and Al2O3 are mixed with 8 mL of ethanol, and then ball-milled at a speed of 3000 rpm for 24 hours. The mixture is then dried at 70°C for 10 hours to remove the ethanol solvent. Finally, the mixture is calcined in a muffle furnace at a temperature of 650°C for 2 hours, starting from room temperature of 25°C and increasing the temperature at a rate of 5°C / min.
[0062] A method for preparing a solid electrolyte includes the following steps:
[0063] 0.16 g of organolithium salt (lithium bis(trifluoromethanesulfonyl)imide) was dissolved in 15 mL of N,N-dimethylformamide (DMF). Then, 40 mg of LiAlO2 prepared by the above method was added and ultrasonically dispersed. 0.125 g of polyacrylonitrile and 0.5 g of polyethylene oxide were added, and the mixture was stirred at 60 °C for 24 hours to obtain a slurry. The slurry was poured onto a polytetrafluoroethylene plate and scraped to a uniform thickness (2 mm) with a scraper. Then, it was heated at 60 °C for 48 hours in a vacuum drying oven to remove the solvent, thus obtaining a solid electrolyte, which was stored in a glove box.
[0064] Example 2: Preparation of solid electrolytes
[0065] A solid electrolyte comprising 40 mg LiAlO2, 0.125 g polyacrylonitrile, 0.5 g polyethylene oxide, and 0.16 g organic lithium salt.
[0066] The preparation process of LiAlO2 is as follows: 15 mmol each of Li2CO3 and Al2O3 are mixed with 8 mL of ethanol, and then ball-milled at a speed of 3000 rpm for 24 hours. The mixture is then dried at 70°C for 10 hours to remove the ethanol solvent. Finally, the mixture is calcined in a muffle furnace at a temperature of 5°C / min, starting from room temperature of 25°C, to 800°C for 2 hours.
[0067] A method for preparing a solid electrolyte includes the following steps:
[0068] 0.16 g of organolithium salt (lithium bis(trifluoromethanesulfonyl)imide) was dissolved in 15 mL of N,N-dimethylformamide (DMF). Then, 40 mg of LiAlO2 prepared by the above method was added and ultrasonically dispersed. 0.125 g of polyacrylonitrile and 0.5 g of polyethylene oxide were added, and the mixture was stirred at 60 °C for 24 hours to obtain a slurry. The slurry was poured onto a polytetrafluoroethylene plate and scraped to a uniform thickness (2 mm) with a scraper. Then, it was heated at 60 °C for 48 hours in a vacuum drying oven to remove the solvent, thus obtaining a solid electrolyte, which was stored in a glove box.
[0069] Example 3: Preparation of solid electrolyte
[0070] A solid electrolyte comprising 40 mg LiAlO2, 0.1 g polyacrylonitrile, 0.5 g polyethylene oxide, and 0.16 g organic lithium salt.
[0071] The preparation process of LiAlO2 is as follows: 15 mmol each of Li2CO3 and Al2O3 are mixed with 8 mL of ethanol, and then ball-milled at a speed of 3000 rpm for 24 hours. The mixture is then dried at 70°C for 10 hours to remove the ethanol solvent. Finally, the mixture is calcined in a muffle furnace at a temperature of 650°C for 2 hours, starting from room temperature of 25°C and increasing the temperature at a rate of 5°C / min.
[0072] A method for preparing a solid electrolyte includes the following steps:
[0073] 0.16 g of organolithium salt (lithium bis(trifluoromethanesulfonyl)imide) was dissolved in 15 mL of N,N-dimethylformamide (DMF). Then, 40 mg of LiAlO2 prepared by the above method was added and ultrasonically dispersed. 0.1 g of polyacrylonitrile and 0.5 g of polyethylene oxide were added, and the mixture was stirred at 60 °C for 24 hours to obtain a slurry. The slurry was poured onto a polytetrafluoroethylene plate and scraped to a uniform thickness (2 mm) with a scraper. Then, it was heated at 60 °C for 48 hours in a vacuum drying oven to remove the solvent, thus obtaining a solid electrolyte, which was stored in a glove box.
[0074] Example 4: Preparation of solid electrolytes
[0075] A solid electrolyte comprising 40 mg LiAlO2, 0.125 g polyacrylonitrile, 0.5 g polyethylene oxide, and 0.21 g organic lithium salt.
[0076] The preparation process of LiAlO2 is as follows: 15 mmol each of Li2CO3 and Al2O3 are mixed with 8 mL of ethanol, and then ball-milled at a speed of 3000 rpm for 24 hours. The mixture is then dried at 70°C for 10 hours to remove the ethanol solvent. Finally, the mixture is calcined in a muffle furnace at a temperature of 650°C for 2 hours, starting from room temperature of 25°C and increasing the temperature at a rate of 5°C / min.
[0077] A method for preparing a solid electrolyte includes the following steps:
[0078] 0.21 g of organolithium salt (lithium bis(trifluoromethanesulfonyl)imide) was dissolved in 15 mL of N,N-dimethylformamide (DMF). Then, 40 mg of LiAlO2 prepared by the above method was added and ultrasonically dispersed. 0.125 g of polyacrylonitrile and 0.5 g of polyethylene oxide were added, and the mixture was stirred at 60 °C for 24 hours to obtain a slurry. The slurry was poured onto a polytetrafluoroethylene plate and scraped to a uniform thickness (2 mm) with a scraper. Then, the solvent was removed by heating at 60 °C for 48 hours in a vacuum drying oven to obtain a solid electrolyte, which was stored in a glove box.
[0079] Example 5: Preparation of solid electrolyte
[0080] Compared with Example 1, the only difference in Example 5 is that the amount of LiAlO2 used is changed to 80mg, and the rest of the process is the same as in Example 1.
[0081] Comparative Example 1
[0082] Compared with Example 1, the only difference in Comparative Example 1 is that LiAlO2 and polyacrylonitrile are not added; the rest of the process is the same as in Example 1.
[0083] Comparative Example 2
[0084] Compared with Example 1, the only difference in Comparative Example 2 is that LiAlO2 is not added; the rest of the process is the same as in Example 1.
[0085] Comparative Example 3
[0086] Compared with Example 1, the only difference in Comparative Example 3 is that an equal amount of polyvinylidene fluoride is used instead of polyethylene oxide in Example 1, and the rest of the process is the same as in Example 1.
[0087] Comparative Example 4
[0088] Compared with Example 1, the only difference in Comparative Example 4 is that an equal amount of commercially available LiAlO2 (the particle size range of commercially available LiAlO2 is 2-3 μm) is used instead of the LiAlO2 in Example 1, and the rest of the process is the same as in Example 1.
[0089] Application Example 1
[0090] A battery comprising a lithium iron phosphate positive electrode, a lithium negative electrode, and a solid electrolyte prepared in Example 1;
[0091] The preparation process of the positive electrode is as follows: Lithium iron phosphate, acetylene black, and polyvinylidene fluoride are dissolved in a solvent, stirred and mixed, coated onto aluminum foil, and placed in a vacuum drying oven to remove the solvent, thus obtaining the positive electrode.
[0092] The weight ratio of lithium iron phosphate, acetylene black, and polyvinylidene fluoride is 7:1.5:1.5;
[0093] The solvent is N-methylpyrrolidone (NMP);
[0094] The ratio of the total weight of lithium iron phosphate, acetylene black, and polyvinylidene fluoride (70 mg, 15 mg, and 15 mg respectively) to the amount of solvent is 100 mg: 400 μL.
[0095] The mixing time is 8 hours;
[0096] The thickness of the coating on the aluminum foil is 60μm;
[0097] The solvent was removed in the vacuum drying oven at a temperature of 80°C for 12 hours.
[0098] Product effectiveness test
[0099] 1. Solid electrolyte structure testing
[0100] Figure 1 This is a SEM image of LiAlO2 obtained in Example 1 of the present invention; from Figure 1 It can be seen that the size of the prepared LiAlO2 nanoparticles is between 40-50 nm.
[0101] Figure 2 This is a SEM image of the solid electrolyte prepared in Example 1 of the present invention; Figure 2 This indicates that the LiAlO2 nanoparticles are uniformly dispersed in the polymer matrix.
[0102] Figure 3 The XRD patterns are of the solid electrolytes prepared in Example 1, Comparative Example 1, and Comparative Example 2 of this invention; from Figure 3It can be seen that the XRD characteristic peaks of the solid electrolyte are enhanced to a certain extent after the addition of polyacrylonitrile, which is due to the high crystallinity of polyacrylonitrile; after the addition of LiAlO2, the characteristic peaks of the solid electrolyte are weaker than those of Comparative Example 1 and Comparative Example 2, indicating that the addition of LiAlO2 significantly reduces the crystallinity of polyethylene oxide.
[0103] 2. Electrical performance testing
[0104] Figure 4 This is a graph showing the relationship between the ionic conductivity and temperature of the solid electrolytes prepared in Examples 1, 1, and 2 of this invention at 30-70℃. Figure 4 ( Figure 4 The vertical axis represents the logarithm of ionic conductivity to the base 10, and the horizontal axis represents 1000 / Kelvin (where Kelvin = Celsius + 273.15). It can be seen that the ionic conductivity of the three solid electrolytes prepared in Example 1, Comparative Example 1, and Comparative Example 2 all increased with increasing temperature. The addition of polyacrylonitrile and LiAlO2 significantly reduced the crystallinity of polyethylene oxide, thereby significantly increasing the ionic conductivity of the solid electrolyte.
[0105] Figure 5 The solid electrolyte prepared in Comparative Example 2 was assembled into a lithium symmetric battery at 60 °C and 50 μA cm⁻¹. -2 100μA cm -2 Cyclic stability curves under current density gradient; Figure 5 This demonstrates that the solid electrolyte prepared in Comparative Example 2 was assembled into a lithium-ion symmetric battery (using two lithium sheets as the positive and negative electrodes respectively, and assembling the battery into a lithium-ion symmetric battery using a solid electrolyte). The stability of the solid electrolyte was tested at a current density of 50 μA cm⁻¹. -2 The battery can cycle stably for 200 hours at a current density of 100 μA cm⁻¹. -2 It was damaged after only 100 hours of operation.
[0106] Figure 6 The solid electrolyte prepared in Example 1 of this invention was assembled into a lithium symmetric battery at 60°C and 50 μA cm⁻¹. -2 100μA cm -2 Cyclic stability curves under current density gradient; Figure 6 This indicates that the solid electrolyte prepared in Example 1 was assembled into a lithium symmetric battery, and the stability of the solid electrolyte was tested. The symmetric battery was stable at 50 μA cm⁻¹. -2 and 100μA cm -2The solid electrolyte prepared in Example 1 of this invention exhibits good electrochemical cycling stability, demonstrating stable cycling performance under both high current and low current densities. The addition of LiAlO2 further enhances the cycling stability of the solid electrolyte at high currents.
[0107] Figure 7 The LSV curves were obtained by assembling solid electrolytes from Comparative Examples 1, 2, and 1 with steel sheets and lithium sheets into batteries; from Figure 7 It can be seen that the electrochemical window corresponding to Comparative Example 1 is 3.8V, the electrochemical window corresponding to Comparative Example 2 is 4.1V, and the electrochemical window corresponding to Example 1 can reach 4.8V, indicating that the presence of LiAlO2 and polyacrylonitrile can increase the oxidation resistance potential of the solid electrolyte.
[0108] Figure 8 The performance curves of the battery in Application Example 1 are shown in the cycling performance curves at 60°C and a current density of 0.5C. From... Figure 8 It can be seen that the battery's first discharge specific capacity is 159.3 mAh g. -1 After 200 cycles, the specific capacity still reached 137.2 mAh g. -1 The capacity retention rate is 86.1%, and the battery's cycle stability is excellent.
[0109] 3. The ionic conductivity of the solid electrolytes in Examples 1 and 5, and Comparative Examples 3 and 4 at 30°C and 60°C is shown in Table 1.
[0110] Table 1
[0111] <![CDATA[Ionic conductivity at 30 °C (S cm -1 )]]> <![CDATA[Ionic conductivity at 60 °C (S cm -1 )]]> Example 1 <![CDATA[8.35×10 -5 ]]> <![CDATA[3.6×10 -4 ]]> Example 5 <![CDATA[7.84×10 -5 ]]> <![CDATA[5.4×10 -4 ]]> Comparative Example 3 <![CDATA[5.16×10 -5 ]]> <![CDATA[1.83×10 -4 <!-- 6 -->]]> Comparative Example 4 <![CDATA[1.36×10 -5 ]]> <![CDATA[2.85×10 -4 ]]>
[0112] As shown in Table 1, at 30°C, the solid electrolyte of Example 1 (with 40 mg of LiAlO2) has a higher ionic conductivity, while at 60°C, the solid electrolyte of Example 5 (with 80 mg of LiAlO2) has a higher ionic conductivity. Considering that nanoparticles may agglomerate when the content is high, the preferred amount of LiAlO2 in this invention is 40 mg.
[0113] As can be seen from the comparison of Example 1, in Comparative Example 3, when polyvinylidene fluoride was used instead of polyethylene oxide, the ionic conductivity of the solid electrolyte was significantly reduced at different temperatures.
[0114] Compared with Example 1, the ionic conductivity of the electrolyte in Comparative Example 4 is significantly reduced. This is because commercially available LiAlO2 particles are large, hindering the movement of lithium ions in the solid electrolyte. Furthermore, the large particle size results in a smaller overall specific surface area, reducing the interfacial transport region and thus lowering the ionic conductivity of the solid electrolyte.
[0115] This invention prepares nano-sized LiAlO2 through solid-state synthesis, which reduces the crystallinity of the electrolyte, increases the ion transport region at the interface between LiAlO2 and the polymer, and improves the ionic conductivity of the solid electrolyte. The solid electrolyte is prepared by a solvothermal method, which is simple and low in cost. Polyacrylonitrile and lithium foil can form a stable interface, which increases the stability of battery cycling. The synergistic effect of LiAlO2, polyacrylonitrile, and polyethylene oxide improves the mechanical, thermodynamic, and electrochemical properties of the solid electrolyte.
[0116] Furthermore, it should be noted that the solid electrolytes obtained in Examples 2-4 of this invention have similar effects to those in Example 1, and within the scope of protection of the claims of this invention, the electrical properties of the obtained solid electrolytes are similar to those in Example 1. The specific embodiments of this invention described above do not constitute a limitation on the scope of protection of this invention. Any other corresponding changes and modifications made according to the technical concept of this invention should be included within the scope of protection of the claims of this invention.
Claims
1. A solid state electrolyte, characterized by, It includes LiAlO2, polyacrylonitrile, polyethylene oxide, and lithium bis(trifluoromethanesulfonyl)imide; the particle size of LiAlO2 is 20-60 nm; by weight, it includes 4-15 parts of LiAlO2, 10-25 parts of polyacrylonitrile, 50-75 parts of polyethylene oxide, and 5-35 parts of lithium bis(trifluoromethanesulfonyl)imide.
2. The method of producing a solid-state electrolyte according to claim 1, characterized by, Includes the following steps: Lithium bis(trifluoromethanesulfonyl)imide was dissolved in a solvent, and then LiAlO2, polyacrylonitrile, and polyethylene oxide were added. The mixture was stirred to obtain a slurry, which was then dried to obtain the solid electrolyte. The preparation process of LiAlO2 was as follows: Li2CO3 and Al2O3 were mixed with ethanol, and then ball-milled at a speed of 2800-3500 rpm for 10-24 hours. The mixture was then dried at 60-80℃ for 8-12 hours and calcined at 600-850℃ for 1-4 hours.
3. The preparation method according to claim 2, characterized in that, Li + molar mass ratio of 1 : (18-22); and a mass ratio of polyethylene oxide to polyacrylonitrile in the slurry of (3-6) :
1.
4. The application of the solid electrolyte as described in claim 1 in a battery.
5. A battery, characterized in that, It includes the solid electrolyte and positive electrode sheet as described in claim 1.
6. The battery according to claim 5, characterized in that, The preparation process of the positive electrode sheet is as follows: lithium iron phosphate, acetylene black, and polyvinylidene fluoride are dissolved in a solvent, stirred and mixed, coated onto aluminum foil, and placed in a vacuum drying oven to remove the solvent, thereby obtaining the positive electrode sheet.