Solid-state electrolyte, method for preparing the same, and solid-state battery

Abstract

The application belongs to the technical field of lithium ion batteries, and relates to a solid-state electrolyte, a preparation method thereof and a solid battery. The preparation method of the solid-state electrolyte comprises the following steps: under the condition that no external solvent is added, uniformly mixing lithium salt, polyethylene oxide (PEO) and an additive, stirring, and heat pressing to obtain a full solid-state electrolyte; the additive comprises one or both of a compound containing a sulfone group and a compound containing an amide group. The surface of the solid-state electrolyte is smooth and free of holes. The application further discloses a solid battery based on the solid-state electrolyte, and the solid battery has good cycle stability.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of lithium ion batteries, and relates to a solid-state electrolyte and a preparation method thereof and a solid-state battery. BACKGROUND

[0002] The upper limit of the theoretical energy density of the current commercial lithium ion battery is about 350 Wh kg -1 Moreover, uncontrollable lithium dendrite growth behavior in the liquid electrolyte system leads to a sharp decrease in the cycle life of the battery, and violent side reactions of metallic lithium and organic electrolyte easily cause heat runaway and other safety hazards. With the increasing demand for driving range of new energy vehicles, the safety of the battery is becoming more and more prominent, and safety is still a key factor restricting the application of lithium ion batteries in the field of high power / high energy.

[0003] The solid-state electrolyte has the advantages of non-flammability, high mechanical strength, strong ability to inhibit lithium dendrites, and the like, and can effectively improve the safety and cycle stability of the battery. Among various types of solid-state electrolytes, the polymer solid-state electrolyte has excellent processing performance and is expected to become the most promising next-generation solid-state electrolyte. However, although the traditional polyethylene oxide (PEO) based electrolyte is widely used, it has low room temperature ionic conductivity and insufficient mechanical strength, and is difficult to inhibit the growth of lithium dendrites, resulting in poor cycle stability; moreover, a large amount of volatile organic solvent is used in the preparation process, which increases the cost and environmental pressure. SUMMARY

[0004] The purpose of the present application is to solve the problem of using solvent in the preparation process of the polymer-based electrolyte in the prior art, and to provide a method for preparing a solid-state electrolyte by a solvent-free dry method. The preparation method is simpler, the room temperature ionic conductivity of the obtained solid-state electrolyte is high, the generation of lithium dendrites can be effectively inhibited, and the electrical performance and safety performance of the solid-state battery are improved.

[0005] One purpose of the present application is achieved by the following technical solutions:

[0006] A preparation method of a solid-state electrolyte comprises the following steps: under no external solvent, uniformly mixing lithium salt, polyethylene oxide (PEO) and an additive, stirring at 60-90 DEG C for 1-12 hours, and then performing hot pressing treatment at 40-90 DEG C to obtain a full solid-state electrolyte.

[0007] The additive comprises one or more of a sulfone group-containing compound and an amide group-containing compound.

[0008] The molar ratio of the sulfone group in the sulfone group-containing compound and / or the amide group in the amide group-containing compound, the ethylene oxide group in the polyethylene oxide, and the lithium ion in the lithium salt is (0.1-5):(3-20):1.

[0009] As preferred, the solid-state electrolyte surface is smooth and free of holes.

[0010] As preferred, the molar ratio of ethylene oxide in the polyethylene oxide, lithium ion in the lithium salt, and sulfone group in the sulfone group-containing compound is (0.5-2):(13-20):1.

[0011] As preferred, when the additive is a sulfone group-containing compound, the molar ratio of ethylene oxide in the polyethylene oxide, lithium ion in the lithium salt, and sulfone group in the sulfone group-containing compound is 16:1:(0.5-2).

[0012] Further preferred, the molar ratio of ethylene oxide in the polyethylene oxide, lithium ion in the lithium salt, and sulfone group in the sulfone group-containing compound is 16:1:(0.8-1.2).

[0013] Further preferred, the molar ratio of ethylene oxide in the polyethylene oxide, lithium ion in the lithium salt, and sulfone group in the sulfone group-containing compound is 16:1:1.2.

[0014] As preferred, the sulfone group-containing compound includes one or more of methyl ethyl sulfone, dimethyl sulfone, tetramethylene sulfone, 3,4-dibromotetramethylene sulfone, fluorophenyl methyl sulfone, 3-methyltetramethylene sulfone, di-n-octyl sulfone, ethyl butylene sulfone, chlorobenzyl sulfone, and 2-chlorophenyl methyl sulfone.

[0015] As preferred, the amide group-containing compound includes one or more of urea, benzamide, acetamide, toluenesulfonamide, γ-butyrolactam, methyl urea, dimethyl urea, and hydroxymethyl urea.

[0016] As preferred, the lithium salt includes an organic lithium salt and / or an inorganic lithium salt.

[0017] Further preferred, the organic lithium salt includes one or more of lithium bisfluorosulfonylimide (LiFSI), lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), lithium difluoro(oxalato)borate (LiDFOB), and lithium difluoro(oxalato)phosphate (LiDFOP).

[0018] Further preferred, the inorganic lithium salt includes one or more of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium fluorosulfonate, and lithium perchlorate.

[0019] As preferred, the all-solid-state electrolyte further includes a ceramic material.

[0020] Further preferred, the ceramic material includes one or more of lithium lanthanum zirconium oxide (LLZO), tantalum-doped lithium lanthanum zirconium oxide (LLZTO), and lithium-germanate (LISICON).

[0021] Further preferred, the ceramic material accounts for 0.1-30wt% of the all-solid-state electrolyte.

[0022] Further preferably, the ceramic material accounts for 5-15wt% in the all-solid-state electrolyte.

[0023] Preferably, the hot-pressing treatment is performed at a temperature of 50-70℃, for a time of 10-240s, and at a pressure of 1-30Mpa.

[0024] Preferably, the solid-state electrolyte has an ion conductivity of >8.0×10 -5 S / cm at room temperature (25℃).

[0025] Preferably, the solid-state electrolyte has an ion conductivity of >2.0×10 -4 S / cm at 45℃.

[0026] The second object of the present application is achieved by the following technical solutions.

[0027] A solid-state electrolyte prepared by the above method.

[0028] Preferably, the raw materials of the solid-state electrolyte include a lithium salt, polyethylene oxide (PEO), and an additive; the additive includes one or more of a sulfone-containing compound and an amide-containing compound.

[0029] Further preferably, the sulfone-containing compound includes one or more of methyl ethyl sulfone, dimethyl sulfone, tetramethylene sulfone, 3,4-dibromotetramethylene sulfone, fluorophenyl methyl sulfone, 3-methyltetramethylene sulfone, di-n-octyl sulfone, ethyl butylene sulfone, chlorophenyl methyl sulfone, and 2-chlorophenyl methyl sulfone.

[0030] Further preferably, the amide-containing compound includes one or more of urea, benzamide, acetamide, toluenesulfonamide, γ-butyrolactam, methyl urea, dimethyl urea, and hydroxymethyl urea.

[0031] Preferably, the raw materials of the solid-state electrolyte further include a ceramic material.

[0032] Further preferably, the ceramic material accounts for 0.1-30wt% in the raw materials of the solid-state electrolyte.

[0033] The third object of the present application is achieved by the following technical solutions.

[0034] A solid-state battery including the above solid-state electrolyte.

[0035] Preferably, the solid-state battery has a metal lithium as the negative electrode.

[0036] Preferably, the solid-state battery has one or more of lithium iron phosphate (LFP), ternary material NCM, ternary material NCA, lithium cobalt oxide (LCO), lithium manganese oxide (LMO), and lithium vanadium phosphate (LVP) as the positive electrode.

[0037] As preferred, the voltage range of the solid-state battery is 2.5-3.8V.

[0038] As preferred, the solid-state battery has a capacity retention rate >70% and a coulombic efficiency >99% after 0.2C rate cycling for 600 times at room temperature.

[0039] As preferred, the solid-state battery has a capacity retention rate >75% and a coulombic efficiency >99% after 0.5C rate cycling for 500 times at 45℃.

[0040] Compared with the prior art, the present application has the following beneficial effects:

[0041] 1. No other solvent is added in the solid-state electrolyte of the present application, the surface of the solid-state electrolyte is smooth and has no holes, the contact impedance of the electrolyte and the positive and negative electrodes is effectively reduced, the long cycle performance and rate performance of the lithium ion battery are improved, and the dense structure effectively blocks the internal micro-short circuit channel caused by voltage drop, when the battery voltage changes sharply, the electrode material and the electrolyte will not produce conductive lithium dendrites or metal lithium deposition due to the existence of pores, so as to avoid the direct contact short circuit of the positive and negative electrodes caused by the penetration of the electrolyte;

[0042] 2. No other solvent is added in the solid-state electrolyte of the present application, which avoids the erosion of the organic solvent residue to the internal structure of the battery, and significantly improves the safety of the battery in the whole life cycle;

[0043] 3. The solid-state electrolyte of the present application has good room temperature ionic conductivity, effectively reduces the interface impedance, significantly optimizes the dynamic performance of the battery, and greatly shortens the charge and discharge relaxation time;

[0044] 4. The present application successfully expands the electrochemical window of the solid-state battery, improves the electrode reaction kinetics of the battery at high and low voltages, reduces the occurrence of side reactions, inhibits the structural change and capacity attenuation of the electrode material, thereby significantly improving the cycle stability of the battery and prolonging the service life. BRIEF DESCRIPTION OF DRAWINGS

[0045] Figure 1 It is a schematic diagram of the solid-state electrolyte in the present application.

[0046] Figure 2 It is a scanning electron microscope graph of the cross section of the solid-state electrolyte in Example 1 of the present application.

[0047] Figure 3 It is a scanning electron microscope comparison graph of the surface morphology of the solid-state electrolyte in Example 1 and Comparative Example 1 of the present application.

[0048] Figure 4 It is an EIS comparison graph of the solid-state battery in Example 1 and Comparative Example 1 of the present application.

[0049] Figure 5 Charge-discharge curves of the solid-state battery in Example 1 of the present application after different cycle numbers.

[0050] Figure 6 Stability comparison chart of the symmetric battery in Example 1 and Comparative Example 1 of the present application.

[0051] Figure 7 Cycle performance chart of the solid-state battery in Example 5 of the present application at 45℃ and 1.0C.

[0052] Figure 8 Cycle performance chart of the solid-state battery in Example 5 of the present application at 45℃ and 2.0C. DETAILED DESCRIPTION

[0053] The technical solutions of the present application will be further described and explained by specific examples. It should be understood that the specific examples described herein are only used to help understand the present application, and are not used to limit the specific application of the present application.

[0054] If not otherwise specified, the raw materials used in the examples of the present application are all commonly used raw materials in the art, and the methods used in the examples are all conventional methods in the art.

[0055] In this text, the molecular weight of polyethylene oxide used in the examples and comparative examples of the present application is 60000.

[0056] In this text, if the amount of additive in the raw materials of the solid-state electrolyte of the present application is too much or too little, a homogeneous solid-state electrolyte cannot be formed, and crystals (lithium salt or additive) are precipitated, which significantly reduces the comprehensive performance of the all-solid-state electrolyte film. First, the crystal precipitation area (defect) will destroy the continuous ion transmission path, increase the ion migration resistance, and cause the bulk ion conductivity of the electrolyte film to decrease, thereby affecting the rate performance and energy efficiency of the battery. Second, the mechanical strength of the film is weakened, which easily causes local stress concentration during battery cycling, accelerates the rupture of the film structure, and shortens the battery life. In addition, it causes poor contact between the electrode and the electrolyte, aggravates the interface impedance, and induces lithium dendrite growth, which brings safety hazards. The crystal precipitation area may also form local electric field distortion and aggravate the interface side reaction.

[0057] In this text, when the additive is a small molecule symmetric sulfone additive, the molar ratio of ethylene oxide in polyethylene oxide to lithium ions in lithium salt is (3-13): 1 (not including 13:1), and the electrolyte is gel-like; when the molar ratio of ethylene oxide in polyethylene oxide to lithium ions in lithium salt is less than 3:1, a solid-state electrolyte cannot be formed, which affects the cycle performance of the battery. In this text, the performance of the solid-state battery is tested on a LAND tester.

[0058] Example 1

[0059] The solid-state electrolyte raw materials were weighed, 2.45 g of polyethylene oxide (PEO), 1 g of lithium salt LiTFSI, and 0.39 g of additive dimethyl sulfone. The molar ratio of ethylene oxide groups (-C2H4-O-) in polyethylene oxide, lithium ions (Li + ) in lithium salt, and sulfone groups in dimethyl sulfone was 16:1:1.2.

[0060] After mixing the solid-state electrolyte raw materials, stirring at 80°C for 2h, then reducing to room temperature, hot pressing at 65°C and 10Mpa for 90s, reducing to room temperature, and cutting the piece, the all-solid-state electrolyte was obtained.

[0061] Figures 1-3 The all-solid-state electrolyte of the present embodiment is shown in the physical diagram, cross-section, and surface scanning electron microscope images. It can be seen that the all-solid-state electrolyte prepared in the present embodiment has a smooth surface and a uniform interior.

[0062] The room temperature ionic conductivity of the solid-state electrolyte in the present embodiment was 8.9×10 -5 S / cm; the ionic conductivity at 45°C was 2.0×10 -4 S / cm, and the ionic conductivity at 60°C was 7.6×10 -4 S / cm.

[0063] The above all-solid-state electrolyte was assembled with a metal lithium negative electrode and a lithium iron phosphate positive electrode to form a solid-state battery.

[0064] The performance of the solid-state battery was tested, and the details are shown in Table 1.

[0065] The charge-discharge voltage range of the solid-state battery in the present embodiment was 2.5V~3.8V.

[0066] At room temperature, the charge-discharge was carried out at 0.2C, and the capacity retention rate was 72.02% after 600 cycles, and the coulombic efficiency was 99.9%.

[0067] At a temperature of 45°C, the charge-discharge was carried out at 0.5C, the initial cycle capacity was 154.7mAh / g, the coulombic efficiency was 99.5% after 500 cycles, and the capacity retention rate was 79.1%; the charge-discharge was carried out at 1C, the initial cycle capacity was 108.3mAh / g, the coulombic efficiency was 99.8% after 500 cycles, and the capacity retention rate was 80.4%.

[0068] At a temperature of 60°C, the charge-discharge was carried out at 2.0C, the initial cycle capacity was 139.5mAh / g, the coulombic efficiency was 99.9% after 300 cycles, and the capacity retention rate was 67.8%.

[0069] According to Figure 4 It can be seen that the solid-state battery of the present embodiment has small impedance and low charge transport resistance in the battery. Figure 5It can be seen that the solid-state battery has good cycle performance.

[0070] The above full solid-state electrolyte and metal lithium are assembled into a symmetrical battery.

[0071] According to Figure 6 It can be seen that the symmetrical battery of the embodiment has good stability and can maintain long-time operation.

[0072] Example 2

[0073] The solid-state electrolyte raw materials, polyethylene oxide PEO, lithium salt LiTFSI, and additive dimethyl sulfone were weighed. The molar ratio of ethylene oxide groups (-C2H4-O-) in polyethylene oxide, lithium ions (Li + ) in lithium salt, and sulfone groups in dimethyl sulfone was 8:1:0.8.

[0074] After the solid-state electrolyte raw materials were mixed and stirred at 80°C for 2h, the temperature was lowered to room temperature to obtain a gel-like solid-state electrolyte.

[0075] The room temperature ionic conductivity of the solid-state electrolyte in this embodiment was 8.1×10 -5 S / cm.

[0076] The solid-state battery was assembled according to the steps in Example 1. In this embodiment, the mass of the solid-state electrolyte of the solid-state battery was the same as that of the full solid-state electrolyte of the solid-state battery in Example 1.

[0077] The performance of the solid-state battery was tested. The charge and discharge voltage range of the solid-state battery in this embodiment was 2.5V~3.8V. The specific performance of the solid-state battery is shown in Table 1.

[0078] Example 3

[0079] The solid-state electrolyte raw materials, polyethylene oxide PEO, lithium salt LiTFSI, and additive dimethyl sulfone were weighed. The molar ratio of ethylene oxide groups (-C2H4-O-) in polyethylene oxide, lithium ions (Li + ) in lithium salt, and sulfone groups in dimethyl sulfone was 16:1:1.

[0080] After the solid-state electrolyte raw materials were mixed and stirred at 80°C for 2h, the temperature was lowered to room temperature, and the full solid-state electrolyte was obtained after hot pressing at 65°C and 10Mpa for 90s and lowering the temperature to room temperature, and cutting.

[0081] The full solid-state electrolyte prepared in this embodiment has a smooth surface and uniform interior.

[0082] The room temperature ionic conductivity of the full solid-state electrolyte in this embodiment was 7.9×10 -5 S / cm.

[0083] A solid-state battery was assembled according to the procedure in Example 1. In this example, the mass of the all-solid-state electrolyte of the solid-state battery was the same as that of the all-solid-state electrolyte of the solid-state battery in Example 1.

[0084] The solid-state battery was subjected to performance testing. The charge-discharge voltage range of the solid-state battery in this example was 2.5 V to 3.8 V. The specific performance of the solid-state battery is shown in Table 1.

[0085] Example 4

[0086] The solid-state electrolyte raw materials, polyethylene oxide PEO, lithium salt LiTFSI, and additive dimethyl sulfone, were weighed. The molar ratio of ethylene oxide groups (-C2H4-O-) in polyethylene oxide, lithium ions (Li + ) in lithium salt, and sulfone groups in dimethyl sulfone was 16:1:0.5.

[0087] After the solid-state electrolyte raw materials were mixed and stirred at 80°C for 2 h, the temperature was lowered to room temperature. The mixture was hot-pressed at 65°C and 10 MPa for 90 s, and then the temperature was lowered to room temperature. After the sample was cut, the all-solid-state electrolyte was obtained.

[0088] The all-solid-state electrolyte prepared in this example had a smooth surface and a uniform interior.

[0089] The room-temperature ionic conductivity of the all-solid-state electrolyte in this example was 3.6 x 10 -5 S / cm.

[0090] A solid-state battery was assembled according to the procedure in Example 1. In this example, the mass of the all-solid-state electrolyte of the solid-state battery was the same as that of the all-solid-state electrolyte of the solid-state battery in Example 1.

[0091] The solid-state battery was subjected to performance testing. The charge-discharge voltage range of the solid-state battery in this example was 2.5 V to 3.8 V. The specific performance of the solid-state battery is shown in Table 1.

[0092] Example 5

[0093] The solid-state electrolyte raw materials, polyethylene oxide PEO, lithium salt LiTFSI, and additive dimethyl sulfone, were weighed. The molar ratio of ethylene oxide groups (-C2H4-O-) in polyethylene oxide, lithium ions (Li + ) in lithium salt, and sulfone groups in dimethyl sulfone was 16:1:0.8.

[0094] After the solid-state electrolyte raw materials were mixed and stirred at 80°C for 2 h, the temperature was lowered to room temperature. The mixture was hot-pressed at 65°C and 10 MPa for 90 s, and then the temperature was lowered to room temperature. After the sample was cut, the all-solid-state electrolyte was obtained.

[0095] The all-solid-state electrolyte prepared in this example had a smooth surface and a uniform interior.

[0096] The room temperature ionic conductivity of the all-solid-state electrolyte in this embodiment is 7.4 x 10 -5 S / cm.

[0097] A solid-state battery was assembled according to the steps in Embodiment 1. Among them, the mass of the all-solid-state electrolyte of the solid-state battery in this embodiment is the same as that of the all-solid-state electrolyte of the solid-state battery in Embodiment 1.

[0098] The solid-state battery was tested for performance, and the charge-discharge voltage range of the solid-state battery in this embodiment was 2.5 V to 3.8 V. The specific performance of the solid-state battery is shown in Table 1.

[0099] Figure 7 、 8 The cycle performance diagram of the solid-state battery in this embodiment at 45°C, 1.0C and 2.0C is shown in FIG. 2.

[0100] Embodiment 6

[0101] The solid-state electrolyte raw materials, polyethylene oxide PEO, lithium salt LiTFSI, additive dimethyl sulfone, and ceramic material LLZTO were weighed. The molar ratio of ethylene oxide groups (-C2H4-O-) in polyethylene oxide, lithium ions (Li + ) in lithium salt, and sulfone groups in dimethyl sulfone was 16:1:0.8.

[0102] The solid-state electrolyte raw materials were mixed, and the amount of ceramic material LLZTO added was 5 wt%; then stirred at 80°C for 2h, and then reduced to room temperature, hot pressed at 65°C, 10Mpa for 90s, and then reduced to room temperature. After cutting, the all-solid-state composite electrolyte was obtained.

[0103] The all-solid-state composite electrolyte prepared in this embodiment has a smooth surface and uniform interior.

[0104] The room temperature ionic conductivity of the all-solid-state composite electrolyte in this embodiment is 8.3 x 10 -5 S / cm.

[0105] A solid-state battery was assembled according to the steps in Embodiment 1. Among them, the mass of the all-solid-state composite electrolyte of the solid-state battery in this embodiment is the same as that of the all-solid-state electrolyte of the solid-state battery in Embodiment 1.

[0106] The solid-state battery was tested for performance, and the charge-discharge voltage range of the solid-state battery in this embodiment was 2.5 V to 3.8 V. The specific performance of the solid-state battery is shown in Table 1.

[0107] Embodiment 7

[0108] The solid-state electrolyte raw materials, polyethylene oxide PEO, lithium salt LiTFSI, additive dimethyl sulfone, and ceramic material LLZTO were weighed. The molar ratio of ethylene oxide groups (-C2H4-O-) in polyethylene oxide, lithium ions (Li+ The molar ratio of ethylene oxide groups in the polyethylene oxide (PEO), lithium ions (Li

[0109] The solid-state electrolyte raw materials were mixed and stirred at 80°C for 2h, then cooled to room temperature, hot-pressed at 65°C and 10Mpa for 90s, cooled to room temperature, and then cut to obtain the all-solid-state composite electrolyte.

[0110] The all-solid-state composite electrolyte prepared in this embodiment has a smooth surface and uniform interior.

[0111] The room-temperature ionic conductivity of the all-solid-state composite electrolyte in this embodiment was 8.7x10 -5 S / cm.

[0112] A solid-state battery was assembled according to the steps in Example 1. In this embodiment, the mass of the all-solid-state composite electrolyte of the solid-state battery was the same as that of the all-solid-state electrolyte of the solid-state battery in Example 1.

[0113] The performance of the solid-state battery was tested, and the charge-discharge voltage range of the solid-state battery in this embodiment was 2.5V-3.8V. The specific performance of the solid-state battery is shown in Table 1.

[0114] Example 8

[0115] The solid-state electrolyte raw materials, polyethylene oxide (PEO), lithium salt (LiTFSI), and additive dimethyl sulfone were weighed. The molar ratio of ethylene oxide groups in the polyethylene oxide (PEO), lithium ions (Li + ), and sulfone groups in the cyclic sulfone was 16:1:0.8.

[0116] The solid-state electrolyte raw materials were mixed and stirred at 80°C for 2h, then cooled to room temperature, hot-pressed at 65°C and 10Mpa for 90s, cooled to room temperature, and then cut to obtain the all-solid-state electrolyte.

[0117] The all-solid-state electrolyte prepared in this embodiment has a smooth surface and uniform interior.

[0118] The room-temperature ionic conductivity of the all-solid-state electrolyte in this embodiment was 6.2x10 -5 S / cm.

[0119] A solid-state battery was assembled according to the steps in Example 1. In this embodiment, the mass of the all-solid-state composite electrolyte of the solid-state battery was the same as that of the all-solid-state electrolyte of the solid-state battery in Example 1.

[0120] The performance of the solid-state battery was tested, and the charge-discharge voltage range of the solid-state battery in this embodiment was 2.5V-3.8V. The specific performance of the solid-state battery is shown in Table 1.

[0121] Example 9

[0122] The solid-state electrolyte raw materials, polyethylene oxide PEO, lithium salt LiTFSI, and additive dimethyl sulfone were weighed. The molar ratio of ethylene oxide groups (-C2H4-O-) in polyethylene oxide, lithium ions (Li + ) in lithium salt, and sulfone groups in cyclobutane sulfone was 16:1:1.1.

[0123] After the solid-state electrolyte raw materials were mixed and stirred at 80°C for 2h, the temperature was lowered to room temperature. The mixture was hot-pressed at 65°C and 10Mpa for 90s, and then the temperature was lowered to room temperature. After the piece was cut, the all-solid-state electrolyte was obtained.

[0124] The all-solid-state electrolyte prepared in this embodiment had a smooth surface and uniform interior.

[0125] The room temperature ionic conductivity of the all-solid-state electrolyte in this embodiment was 6.4×10 -5 S / cm.

[0126] A solid-state battery was assembled according to the steps in Example 1. In this embodiment, the mass of the all-solid-state electrolyte of the solid-state battery was the same as that of the solid-state battery in Example 1.

[0127] The performance of the solid-state battery was tested. The charge-discharge voltage range of the solid-state battery in this embodiment was 2.5V-3.8V. The specific performance of the solid-state battery is shown in Table 1.

[0128] Example 10

[0129] The solid-state electrolyte raw materials, polyethylene oxide PEO, lithium salt LiTFSI, and additive urea were weighed. The molar ratio of ethylene oxide groups (-C2H4-O-) in polyethylene oxide, lithium ions (Li + ) in lithium salt, and amide groups in urea was 16:1:0.8.

[0130] After the solid-state electrolyte raw materials were mixed and stirred at 80°C for 2h, the temperature was lowered to room temperature. The mixture was hot-pressed at 65°C and 10Mpa for 90s, and then the temperature was lowered to room temperature. After the piece was cut, the all-solid-state electrolyte was obtained.

[0131] The all-solid-state electrolyte prepared in this embodiment had a smooth surface and uniform interior.

[0132] A solid-state battery was assembled according to the steps in Example 1. In this embodiment, the mass of the all-solid-state electrolyte of the solid-state battery was the same as that of the solid-state battery in Example 1.

[0133] The performance of the solid-state battery was tested. The charge-discharge voltage range of the solid-state battery in this embodiment was 2.5V-3.8V. At a temperature of 45°C, the battery was charged and discharged at 0.5C, and the first cycle capacity was 123.3mAh / g.

[0134] Example 11

[0135] The solid-state electrolyte raw materials, 2.45 g of polyethylene oxide PEO, 1 g of lithium salt LiTFSI, and 1.31 g of additive dimethyl sulfone were weighed. The molar ratio of ethylene oxide groups (-C2H4-O-) in polyethylene oxide, lithium ions (Li + ) in lithium salt, and sulfone groups in dimethyl sulfone was 16:1:4.

[0136] After the solid-state electrolyte raw materials were mixed and stirred at 80°C for 2h, they were cooled to room temperature, hot-pressed at 65°C and 10Mpa for 90s, cooled to room temperature, and then cut into pieces to obtain the all-solid-state electrolyte. However, there were dimethyl sulfone crystals precipitated.

[0137] The solid-state battery was assembled according to the procedure in Example 1. In this example, the mass of the all-solid-state electrolyte of the solid-state battery was the same as that of the all-solid-state electrolyte of the solid-state battery in Example 1.

[0138] The performance of the solid-state battery was tested. The charge-discharge voltage range of the solid-state battery in this example was 2.5V-3.8V. At a temperature of 45°C, the battery was charged and discharged at 0.5C, and the initial cycle capacity was 108.4mAh / g.

[0139] Comparative Example 1

[0140] The solid-state electrolyte raw materials, 2.45 g of polyethylene oxide PEO, 1.0 g of lithium salt LiTFSI, and 0.39 g of dimethyl sulfone were dissolved in 20 ml of acetonitrile. The molar ratio of ethylene oxide groups (-C2H4-O-) in polyethylene oxide, lithium ions (Li + ) in lithium salt, and sulfone groups in dimethyl sulfone was 16:1:1.2.

[0141] After the above solid-state electrolyte raw materials were mixed and stirred at 80°C for 2h, they were cooled to room temperature, then hot-pressed at 65°C and 10Mpa for 90s, cooled to room temperature, and then cut into pieces to obtain the all-solid-state electrolyte.

[0142] According to the formula: Figure 3 It can be seen that the all-solid-state electrolyte of this comparative example has a hole defect.

[0143] The solid-state battery was assembled according to the procedure in Example 1. In this example, the mass of the all-solid-state electrolyte of the solid-state battery was the same as that of the all-solid-state electrolyte of the solid-state battery in Example 1.

[0144] According to the formula: Figure 4 It can be seen that the impedance of the solid-state battery of this comparative example is significantly greater than that of the solid-state battery in Example 1.

[0145] The solid-state battery was tested for performance, and the charge-discharge voltage range of the solid-state battery in the present comparative example was 2.5 V to 3.8 V. The specific performance of the solid-state battery is shown in Table 1.

[0146] The above-mentioned all-solid-state electrolyte was assembled with lithium metal to form a symmetrical battery. According to the Figure 6 It can be seen that the symmetrical battery in the present comparative example appeared short circuit during operation, and the stability was poor.

[0147] Comparative Example 2

[0148] The solid-state electrolyte raw materials were weighed, 2.45 g of polyethylene oxide PEO, 1 g of lithium salt LiTFSI, and 1.96 g of additive dimethyl sulfone; the molar ratio of ethylene oxide group (-C2H4-O-) in polyethylene oxide, lithium ion (Li + ) in lithium salt, and sulfone group in dimethyl sulfone was 16:1:6.

[0149] After the solid-state electrolyte raw materials were mixed and stirred at 80 DEG C for 2 h, the temperature was lowered to room temperature, and the mixture was hot-pressed at 65 DEG C and 10 Mpa for 90 s, and then the temperature was lowered to room temperature. After the piece was cut, the all-solid-state electrolyte was obtained.

[0150] The all-solid-state electrolyte of the present comparative example had dimethyl sulfone precipitated, and the performance of the solid-state battery was poor.

[0151] Table 1, solid-state battery performance test table

[0152]

[0153] In summary, the solid-state electrolyte of the present application does not add other solvents, the surface of the solid-state electrolyte is smooth and has no holes, which effectively reduces the contact impedance between the electrolyte and the positive and negative electrodes, improves the long cycle performance and rate performance of the lithium ion battery; and the dense structure effectively blocks the internal micro-short circuit channel caused by voltage drop. When the battery voltage changes sharply, the electrode material and the electrolyte will not produce conductive lithium dendrites or metal lithium deposition due to the existence of pores, thereby avoiding the direct contact short circuit of the positive and negative electrodes caused by the electrolyte being pierced.

[0154] Aspects, embodiments, features of the present application should be considered illustrative in all aspects and do not limit the present application, and the scope of the present application is only defined by the claims. Other embodiments, modifications and uses will be apparent to those skilled in the art without departing from the spirit and scope of the claimed application.

[0155] In the preparation method of the present application, the order of each step is not limited to the order listed, and for those skilled in the art, the change of the order of each step without creative labor is also within the protection scope of the present application. In addition, two or more steps or actions can be carried out simultaneously.

[0156] Finally, it should be noted that the embodiments described herein are merely illustrative of the present application and should not be considered limiting in the scope of use of the application. Those skilled in the art will be able to make modifications and / or additions or employ alternatives to the embodiments described herein without departing from the spirit and scope of the present application. The disclosure of the present application is not intended to be limited to the described embodiments thereof. It is, therefore, expressly intended that all such modifications and / or additions or alternatives to the described embodiments as fall within the spirit and broad scope of the application as found in the appended claims be fully embraced by the present application.

Claims

1. A method for preparing a solid electrolyte, characterized in that, The preparation method includes: mixing lithium salt, polyethylene oxide and additives without adding external solvent, stirring at 60~90℃ for 1~12h, and then hot pressing at 40~90℃ to obtain solid electrolyte; The additives include one or more of sulfone-containing compounds and amide-containing compounds; The molar ratio of ethylene oxide in the polyethylene oxide, lithium ions in the lithium salt, and sulfone groups in the sulfone-containing compound is 16:1:(0.8~1.2). The molar ratio of ethylene oxide in the polyethylene oxide, lithium ions in the lithium salt, and amide groups in the amide-containing compound is 16:1:0.

8. The solid electrolyte has a smooth, non-porous surface.

2. The method for preparing a solid electrolyte according to claim 1, characterized in that, The molar ratio of ethylene oxide in the polyethylene oxide, lithium ions in the lithium salt, and sulfone groups in the sulfone-containing compound is 16:1:1.

2.

3. The method for preparing a solid electrolyte according to claim 2, characterized in that, The solid electrolyte has a room temperature ionic conductivity > 8.0 × 10⁻⁶. -5 S / cm.

4. The method for preparing a solid electrolyte according to claim 1, characterized in that, The sulfone-containing compounds include one or more of methyl ethyl sulfone, dimethyl sulfone, sulfolane, 3,4-dibromosulfolane, fluorophenyl methyl sulfone, 3-methyl sulfolane, di-n-octyl sulfone, ethylbutyrate, chlorophenyl sulfone, and 2-chlorophenyl methyl sulfone. The amide-containing compound includes one or more of urea, benzamide, acetamide, toluenesulfonamide, γ-butyrolactam, methylurea, dimethylurea, and hydroxymethylurea; The lithium salt includes organic lithium salts and / or inorganic lithium salts.

5. The method for preparing a solid electrolyte according to claim 4, characterized in that, The solid electrolyte also includes ceramic materials, which account for 0.1 to 30 wt%.

6. The method for preparing a solid electrolyte according to claim 1, characterized in that, The hot pressing process is performed at a temperature of 50~70℃ for 10~240s and a pressure of 1~30MPa.

7. A solid electrolyte, characterized in that, It is prepared by the method for preparing solid electrolyte as described in any one of claims 1 to 6.

8. A solid-state battery, characterized in that, It includes solid electrolytes prepared by the method of preparing solid electrolytes as described in any one of claims 1 to 6, or solid electrolytes as described in claim 7.

9. The solid-state battery according to claim 8, characterized in that, The negative electrode of the solid-state battery is metallic lithium; the positive electrode of the solid-state battery includes one or more of lithium iron phosphate (LFP), ternary material NCM, ternary material NCA, lithium cobalt oxide (LCO), lithium manganese oxide (LMO), and lithium vanadium phosphate (LVP).

10. The solid-state battery according to claim 8, characterized in that, The voltage range of the solid-state battery is 2.5~3.8V.

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