Method for improving electrochemical performance and mechanical performance of semi-solid energy storage cell

Abstract

The invention provides a method for improving electrochemical performance and mechanical performance of a semi-solid energy storage cell. The research method comprises the following steps: (1) respectively testing a positive pole piece, a negative pole piece, an electrolyte and a diaphragm of the semi-solid energy storage cell; (2) respectively improving the positive pole piece, the negative pole piece, the electrolyte and the diaphragm according to a result obtained by testing in the step (1) to obtain an improved positive pole piece, an improved negative pole piece, an improved electrolyte and an improved diaphragm; and carrying out battery assembly on the improved positive pole piece, the improved negative pole piece, the improved electrolyte and the improved diaphragm to obtain the semi-solid energy storage cell with improved performance. The microstructure, the chemical stability and the electrochemical performance of the key material in the semi-solid energy storage cell are obtained, and the positive pole piece, the negative pole piece, the electrolyte and the diaphragm are improved according to the test result, so that the electrochemical performance and the mechanical performance of the semi-solid energy storage cell are improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of battery cells, and particularly relates to a method for improving the electrochemical performance and mechanical performance of semi-solid energy storage battery cells. Background Art

[0002] Safety problems (such as thermal runaway, fire, etc.) brought about by the application of flammable liquid electrolytes pose huge challenges to traditional lithium-ion batteries. To solve these problems, replacing traditional liquid electrolytes with safe and reliable solid electrolytes is a feasible strategy. In a broader context, the development of solid electrolytes is in harmony with the overall goal of promoting the progress of energy storage technologies, thus contributing to a more sustainable and efficient energy application prospect.

[0003] Researchers and practitioners have been continuously working hard to overcome challenges and unlock the full potential of solid-state rechargeable batteries. In recent years, researchers have made significant progress in understanding the basic and special properties of these electrolytes and the materials thereof. Inorganic solid electrolytes (oxides and sulfides), polymer solid electrolytes are currently the solid electrolyte systems that have been studied more. The applications of ceramic, polymer, and composite solid electrolytes in rechargeable lithium-ion batteries have also been reported in many cases.

[0004] Semi-solid energy storage battery cells belong to a type of solid-state battery and are products of the transition from liquid batteries to all-solid-state batteries, occupying an important position in the development process of solid-state batteries; however, the research on semi-solid batteries in the prior art is still insufficient, and it is impossible to deeply understand the influence of key materials in semi-solid batteries on the performance of semi-solid energy storage battery cells, and it is even more difficult to effectively improve the performance of semi-solid energy storage battery cells.

[0005] CN117543071A discloses a semi-solid battery and its manufacturing method and detection method. Among them, a semi-solid battery includes: a filler for storing electrical energy; a cladding for at least accommodating at least a part of the filler; wherein the filler is set in a gel state; the raw materials for preparing the filler are injected into the cladding at least twice with different component combinations so that the unit pyrolysis gas production of the semi-solid battery is less than or equal to 0.1 mL / Ah. The detection method of the semi-solid battery in this document can effectively improve and measure the defects of the semi-solid battery due to reduced gas production. However, the detection method of this semi-solid battery does not conduct in-depth research on the key materials of the semi-solid battery.

[0006] CN114883751A discloses a semi-solid battery, comprising a high-safety ion membrane, a negative electrode sheet, a positive electrode sheet, and an electrolyte; the high-safety ion membrane is located between the negative electrode sheet and the positive electrode sheet; the electrolyte is located between the high-safety ion membrane and the negative electrode sheet, and between the high-safety ion membrane and the positive electrode sheet; the high-safety ion membrane includes a separator, a first coating, and a second coating, the first coating is fixed on one side of the separator close to the negative electrode sheet, and the second coating is fixed on one side of the separator close to the positive electrode sheet; the first coating includes a first functional material, and the first functional material is made of a material capable of in-situ consuming the electrolyte to generate a stable layer; the second coating includes a second functional material, and the second functional material is made of a material capable of reacting with active oxygen molecules. However, this document only studies the influence of the first functional material in the first coating on the performance of the separator and the influence of the second functional material in the second coating on the gas generation of the battery, and does not conduct a comprehensive study on the key materials of the semi-solid battery.

[0007] There is still great room for improvement in the performance of the semi-solid batteries disclosed in the prior art; however, the methods disclosed in the prior art are still not sufficient for the research on semi-solid batteries, and there is no effective method to improve the performance of semi-solid batteries. Therefore, it is crucial to develop and design a method to improve the electrochemical performance and mechanical performance of semi-solid energy storage battery cores. Summary of the Invention

[0008] Aiming at the deficiencies of the prior art, the purpose of the present invention is to provide a method for improving the electrochemical performance and mechanical performance of semi-solid energy storage battery cores. Through multi-angle and multi-level testing methods, the present invention obtains the microstructures, chemical stabilities, and electrochemical performances of the key materials (positive electrode sheets, negative electrode sheets, electrolytes, and separators) in semi-solid energy storage battery cores, and improves the positive electrode sheets, negative electrode sheets, electrolytes, and separators according to the test results, thereby improving the electrochemical performance and mechanical performance of semi-solid energy storage battery cores.

[0009] To achieve this purpose, the present invention adopts the following technical solutions:

[0010] In the first aspect, the present invention provides a method for improving the electrochemical performance and mechanical performance of semi-solid energy storage battery cores, the method comprising:

[0011] (1) Testing the positive electrode sheet, negative electrode sheet, electrolyte, and separator of the semi-solid energy storage battery core respectively;

[0012] After the testing, the surface morphology, surface element distribution, cross-sectional morphology, cross-sectional element distribution, surface composition, element distribution change with the depth of the electrode sheet, XRD composition, differential thermal performance, areal density, tap density, gram capacity, and electrochemical impedance of the positive electrode sheet are obtained;

[0013] After the tests, the surface morphology, surface element distribution, cross-sectional morphology, cross-sectional element distribution, surface composition, the change of element distribution with the depth of the electrode, the crystal structure of the negative electrode material, and the interfacial morphology of the negative electrode are obtained;

[0014] After the tests, the element composition of the inorganic salts, the types of inorganic salts, and the types of organic solvents in the electrolyte are obtained;

[0015] After the tests, the chemical structure, molecular composition, surface morphology, surface element distribution, surface composition, puncture strength, tensile strength, closure temperature, and breakdown temperature of the separator are obtained;

[0016] (2) According to the results obtained from the tests in step (1), the positive electrode, negative electrode, electrolyte, and separator are respectively improved to obtain an improved positive electrode, an improved negative electrode, an improved electrolyte, and an improved separator; then the obtained improved positive electrode, improved negative electrode, improved electrolyte, and improved separator are assembled into a battery to obtain a semi-solid energy storage cell with improved performance;

[0017] The improvement methods include:

[0018] When the electrochemical impedance of the positive electrode obtained in step (1) is greater than 50 Ω·cm 2 and / or the specific capacity is lower than 140 mAh / g, the preparation process of the positive electrode is designed according to the surface morphology, surface element distribution, cross-sectional morphology, cross-sectional element distribution, surface composition, and the change of element distribution with the depth of the electrode of the positive electrode;

[0019] When the SEI film is less than 5 nm in the interfacial morphology diagram of the negative electrode obtained in step (1), the preparation process of the negative electrode is designed according to the surface morphology, surface element distribution, cross-sectional morphology, cross-sectional element distribution, surface composition, the change of element distribution with the depth of the electrode, and the crystal structure of the negative electrode material of the negative electrode;

[0020] When the separator in step (1) meets any one or at least two of the conditions that the average puncture resistance is less than 0.4 kN / mm, the average tensile strength is less than 180 MPa, the closure temperature is less than 110 °C, or the breakdown temperature is less than 130 °C, the preparation process of the separator is designed according to the chemical structure, molecular composition, surface morphology, surface element distribution, and surface composition of the separator.

[0021] In the present invention, the electrochemical impedance of the positive electrode obtained in step (1) is greater than 50 Ω·cm 2 , for example, it can be 55 Ω·cm 2 , 60 Ω·cm 2 , 65 Ω·cm 2 , 70 Ω·cm 2, 75 Ω·cm 2 , 80 Ω·cm 2 , 85 Ω·cm 2 , 90 Ω·cm 2 , 95 Ω·cm 2 or 100 Ω·cm 2 , but not limited to the listed values, and other unlisted values within this range are equally applicable.

[0022] In the present invention, the specific capacity of the positive electrode plate obtained in step (1) is less than 140 mAh / g. For example, it can be 130 mAh / g, 132 mAh / g, 134 mAh / g, 136 mAh / g, or 138 mAh / g, but not limited to the listed values, and other unlisted values within this range are equally applicable.

[0023] In the interface morphology diagram of the negative electrode plate obtained in step (1) of the present invention, the SEI film is less than 5 nm. For example, it can be 1 nm, 2 nm, 3 nm, or 4 nm, but not limited to the listed values, and other unlisted values within this range are equally applicable.

[0024] In step (1) of the present invention, the separator satisfies that the average puncture resistance is less than 0.4 kN / mm. For example, it can be 0.30 kN / mm, 0.32 kN / mm, 0.34 kN / mm, 0.36 kN / mm, or 0.38 kN / mm, but not limited to the listed values, and other unlisted values within this range are equally applicable.

[0025] In step (1) of the present invention, the separator satisfies that the average tensile strength is less than 180 MPa. For example, it can be 160 MPa, 165 MPa, 170 MPa, or 175 MPa, but not limited to the listed values, and other unlisted values within this range are equally applicable.

[0026] In step (1) of the present invention, the separator satisfies that the closed pore temperature is less than 110 °C. For example, it can be 100 °C, 102 °C, 104 °C, 106 °C, 108 °C, or 110 °C, but not limited to the listed values, and other unlisted values within this range are equally applicable.

[0027] In step (1) of the present invention, the separator satisfies that the puncture temperature is less than 130 °C. For example, it can be 120 °C, 122 °C, 124 °C, 126 °C, or 128 °C, but not limited to the listed values, and other unlisted values within this range are equally applicable.

[0028] Through multi-angle and multi-level testing methods, the present invention obtains the microstructures, chemical stabilities, and electrochemical performances of the key materials (positive electrode sheet, negative electrode sheet, electrolyte, and separator) in the semi-solid energy storage battery cell, and improves the positive electrode sheet, negative electrode sheet, electrolyte, and separator according to the test results, thereby enhancing the electrochemical performance and mechanical performance of the semi-solid energy storage battery cell.

[0029] Preferably, during the testing process, the testing method for the positive electrode sheet includes:

[0030] Using a scanning electron microscope to test the surface morphology, surface element distribution, cross-sectional morphology, and cross-sectional element distribution of the positive electrode sheet;

[0031] Using X-ray photoelectron spectroscopy to test the surface composition of the positive electrode sheet;

[0032] Using time-of-flight secondary ion mass spectrometry to test the surface element distribution of the positive electrode sheet and the change of element distribution with the depth of the electrode sheet;

[0033] Using an X-ray diffractometer to test the XRD composition of the positive electrode sheet;

[0034] Using a differential scanning calorimeter to test the differential thermal performance of the positive electrode sheet;

[0035] Using a precision electronic balance and a vernier caliper to test the areal density and tap density of the positive electrode sheet;

[0036] Testing the specific capacity of the positive electrode sheet through charge-discharge testing;

[0037] Testing the electrochemical impedance of the positive electrode sheet through electrochemical impedance spectroscopy.

[0038] Preferably, when using a scanning electron microscope to test the positive electrode sheet, set the acceleration voltage of the scanning electron microscope to 5 - 20 kV and the vacuum degree ≤ 1×10 -3 Pa;

[0039] When using X-ray photoelectron spectroscopy to test the positive electrode sheet, set the energy resolution of the X-ray photoelectron spectroscopy ≤ 0.5 eV;

[0040] When using time-of-flight secondary ion mass spectrometry to test the positive electrode sheet, set the vacuum degree of the time-of-flight secondary ion mass spectrometry ≤ 5×10 -7 Pa;

[0041] When using an X-ray diffractometer to test the positive electrode sheet, set the scanning range of the X-ray diffractometer to 10 - 90°;

[0042] When testing the positive electrode sheet using a differential scanning calorimeter, set the temperature range of the differential scanning calorimeter to 25 - 400 °C and the heating rate to 1 - 20 °C / min;

[0043] When performing charge-discharge tests on the positive electrode sheet, use a BlueTEC battery test system with a voltage range of 3.0 - 4.3 V and a current density of 0.1 - 0.5 C;

[0044] When performing electrochemical impedance spectroscopy tests on the positive electrode sheet, set the frequency range to 100 kHz - 10 mHz and the amplitude to 5 mV.

[0045] When testing the positive electrode sheet using a scanning electron microscope in the present invention, set the acceleration voltage of the scanning electron microscope to 5 - 20 kV. For example, it can be 5 kV, 6 kV, 7 kV, 8 kV, 9 kV, 10 kV, 12 kV, 15 kV, 18 kV or 20 kV, but it is not limited to the listed values, and other unlisted values within this numerical range are equally applicable.

[0046] When testing the positive electrode sheet using a scanning electron microscope in the present invention, set the vacuum degree of the scanning electron microscope ≤ 1×10 -3 Pa. For example, it can be 1×10 -3 Pa, 5×10 -4 Pa, 1×10 -4 Pa, 5×10 -5 Pa or 1×10 -5 Pa, but it is not limited to the listed values, and other unlisted values within this numerical range are equally applicable.

[0047] When testing the positive electrode sheet using X-ray photoelectron spectroscopy in the present invention, set the energy resolution of the X-ray photoelectron spectroscopy ≤ 0.5 eV. For example, it can be 0.5 eV, 0.4 eV, 0.3 eV, 0.2 eV or 0.1 eV, but it is not limited to the listed values, and other unlisted values within this numerical range are equally applicable.

[0048] When testing the positive electrode sheet using time-of-flight secondary ion mass spectrometry in the present invention, set the vacuum degree of the time-of-flight secondary ion mass spectrometry ≤ 5×10 -7 Pa. For example, it can be 5×10 -7 Pa, 1×10 -7 Pa, 5×10 -8 Pa, 1×10 -8 Pa or 5×10 -9 Pa, but it is not limited to the listed values, and other unlisted values within this numerical range are equally applicable.

[0049] When using an X-ray powder diffractometer to test the positive electrode sheet in the present invention, the scanning range of the X-ray powder diffractometer is set to 10-90°, for example, it can be 10°, 20°, 30°, 40°, 50°, 60°, 70°, 80° or 90°, but it is not limited to the listed values, and other unlisted values within this value range are equally applicable.

[0050] When using a differential scanning calorimeter to test the positive electrode sheet in the present invention, the heating rate of the differential scanning calorimeter is set to 1-20 °C / min, for example, it can be 1 °C / min, 2 °C / min, 5 °C / min, 10 °C / min, 15 °C / min or 20 °C / min, but it is not limited to the listed values, and other unlisted values within this value range are equally applicable.

[0051] Preferably, during the testing process, the testing method for the negative electrode sheet includes:

[0052] Using a scanning electron microscope to test the surface morphology, surface element distribution, cross-sectional morphology, and cross-sectional element distribution of the negative electrode sheet;

[0053] Using X-ray photoelectron spectroscopy to test the surface composition of the negative electrode sheet;

[0054] Using time-of-flight secondary ion mass spectrometry to test the surface element distribution of the negative electrode sheet and the change of element distribution with the depth of the electrode sheet;

[0055] Using a transmission electron microscope to test the crystal structure and interface morphology of the negative electrode material on the negative electrode sheet.

[0056] Preferably, when using a scanning electron microscope to test the negative electrode sheet, the acceleration voltage of the scanning electron microscope is set to 5-20 kV and the vacuum degree ≤ 1×10 -3 Pa;

[0057] When using X-ray photoelectron spectroscopy to test the negative electrode sheet, the energy resolution of the X-ray photoelectron spectroscopy is set to ≤ 0.5 eV;

[0058] When using time-of-flight secondary ion mass spectrometry to test the negative electrode sheet, the vacuum degree of the time-of-flight secondary ion mass spectrometry is set to ≤ 5×10 -7 Pa;

[0059] When using a transmission electron microscope to test the negative electrode sheet, the acceleration voltage of the transmission electron microscope is set to 80-300 kV and the vacuum degree ≤ 5×10 -5 Pa.

[0060] When testing the negative electrode plate using a scanning electron microscope in the present invention, the acceleration voltage of the scanning electron microscope is set to 5 - 20 kV. For example, it can be 5 kV, 6 kV, 7 kV, 8 kV, 9 kV, 10 kV, 12 kV, 15 kV, 18 kV or 20 kV, but it is not limited to the listed values, and other unlisted values within this range are equally applicable.

[0061] When testing the negative electrode plate using a scanning electron microscope in the present invention, the vacuum degree of the scanning electron microscope is set to ≤ 1×10 -3 Pa. For example, it can be 1×10 -3 Pa, 5×10 -4 Pa, 1×10 -4 Pa, 5×10 -5 Pa or 1×10 -5 Pa, but it is not limited to the listed values, and other unlisted values within this range are equally applicable.

[0062] When testing the negative electrode plate using X-ray photoelectron spectroscopy in the present invention, the energy resolution of the X-ray photoelectron spectroscopy is set to ≤ 0.5 eV. For example, it can be 0.5 eV, 0.4 eV, 0.3 eV, 0.2 eV or 0.1 eV, but it is not limited to the listed values, and other unlisted values within this range are equally applicable.

[0063] When testing the negative electrode plate using time-of-flight secondary ion mass spectrometry in the present invention, the vacuum degree of the time-of-flight secondary ion mass spectrometry is set to ≤ 5×10 -7 Pa. For example, it can be 5×10 -7 Pa, 1×10 -7 Pa, 5×10 -8 Pa, 1×10 -8 Pa or 5×10 -9 Pa, but it is not limited to the listed values, and other unlisted values within this range are equally applicable.

[0064] When testing the negative electrode plate using a transmission electron microscope in the present invention, the acceleration voltage of the transmission electron microscope is set to 80 - 300 kV. For example, it can be 80 kV, 100 kV, 120 kV, 150 kV, 180 kV, 200 kV, 220 kV, 250 kV, 280 kV or 300 kV, but it is not limited to the listed values, and other unlisted values within this range are equally applicable.

[0065] When testing the negative electrode plate using a transmission electron microscope in the present invention, the vacuum degree of the transmission electron microscope is set to ≤ 5×10 -5 Pa. For example, it can be 5×10 -5 Pa, 1×10-5 Pa, 5×10 -6 Pa, 1×10 -6 Pa or 5×10 -7 Pa, but not limited to the listed values, and other unlisted values within this range are equally applicable.

[0066] Preferably, during the testing process, the testing method for the electrolyte includes:

[0067] Using inductively coupled plasma spectroscopy to test the elemental composition of inorganic salts in the electrolyte;

[0068] Using an ion chromatograph to test the types of inorganic salts in the electrolyte;

[0069] Using a gas chromatography - mass spectrometer to test the types of organic solvents in the electrolyte.

[0070] Preferably, when using inductively coupled plasma spectroscopy to test the electrolyte, set the radio frequency power of the inductively coupled plasma spectroscopy to 1150 - 1500 W and the nebulizer gas flow rate to 0.5 - 0.8 L / min.

[0071] When using inductively coupled plasma spectroscopy to test the electrolyte in the present invention, set the radio frequency power of the inductively coupled plasma spectroscopy to 1150 - 1500 W. For example, it can be 1150 W, 1200 W, 1250 W, 1300 W, 1350 W, 1400 W, 1450 W or 1500 W, but not limited to the listed values, and other unlisted values within this range are equally applicable.

[0072] When using inductively coupled plasma spectroscopy to test the electrolyte in the present invention, set the nebulizer gas flow rate of the inductively coupled plasma spectroscopy to 0.5 - 0.8 L / min. For example, it can be 0.5 L / min, 0.55 L / min, 0.6 L / min, 0.65 L / min, 0.7 L / min, 0.75 L / min or 0.8 L / min, but not limited to the listed values, and other unlisted values within this range are equally applicable.

[0073] Preferably, during the testing process, the testing method for the separator includes:

[0074] Using infrared spectroscopy to test the chemical structure and molecular composition of the separator;

[0075] Using a scanning electron microscope to test the surface morphology and surface element distribution of the separator;

[0076] Using X - ray photoelectron spectroscopy to test the surface composition of the separator.

[0077] Preferably, during the testing process, the testing method of the separator further includes:

[0078] Testing the puncture strength of the separator by using a puncture test;

[0079] Testing the tensile strength of the separator by using a tensile tester;

[0080] Testing the closure temperature and the breakdown temperature of the separator by using a mechanical analyzer.

[0081] Preferably, when testing the separator by using a scanning electron microscope, set the acceleration voltage of the scanning electron microscope to be 5 - 20 kV and the vacuum degree ≤ 1×10 -3 Pa;

[0082] When testing the separator by using X-ray photoelectron spectroscopy, set the energy resolution of the X-ray photoelectron spectroscopy to be ≤ 0.5 eV.

[0083] In the present invention, when testing the separator by using a scanning electron microscope, set the acceleration voltage of the scanning electron microscope to be 5 - 20 kV. For example, it can be 5 kV, 6 kV, 7 kV, 8 kV, 9 kV, 10 kV, 12 kV, 15 kV, 18 kV or 20 kV, but it is not limited to the listed values, and other unlisted values within this value range are equally applicable.

[0084] In the present invention, when testing the separator by using a scanning electron microscope, set the vacuum degree of the scanning electron microscope to be ≤ 1×10 -3 Pa, for example, it can be 1×10 -3 Pa, 5×10 -4 Pa, 1×10 -4 Pa, 5×10 -5 Pa or 1×10 -5 Pa, but it is not limited to the listed values, and other unlisted values within this value range are equally applicable.

[0085] In the present invention, when testing the separator by using X-ray photoelectron spectroscopy, set the energy resolution of the X-ray photoelectron spectroscopy to be ≤ 0.5 eV. For example, it can be 0.5 eV, 0.4 eV, 0.3 eV, 0.2 eV or 0.1 eV, but it is not limited to the listed values, and other unlisted values within this value range are equally applicable.

[0086] Compared with the prior art, the present invention has the following beneficial effects:

[0087] Through multi - angle and multi - level testing methods, the present invention obtains the microstructures, chemical stabilities, and electrochemical performances of the key materials (positive electrode sheet, negative electrode sheet, electrolyte, and separator) in the semi - solid energy storage battery cell, and improves the positive electrode sheet, negative electrode sheet, electrolyte, and separator according to the test results, thereby enhancing the electrochemical performance and mechanical performance of the semi - solid energy storage battery cell. Description of the Drawings

[0088] Figure 1 It is the SEM image of different positions on the surface of the positive electrode sheet.

[0089] Figure 2 It is the SEM image, elemental distribution map, and elemental content table of the first position on the surface of the positive electrode sheet.

[0090] Figure 3 It is the SEM image, elemental distribution map, and elemental content table of the second position on the surface of the positive electrode sheet.

[0091] Figure 4 It is the SEM image of different cross - section positions of the positive electrode sheet.

[0092] Figure 5 It is the SEM image and elemental distribution map corresponding to the first cross - section position of the cross - section of the positive electrode sheet.

[0093] Figure 6 It is the SEM image, elemental distribution map, and elemental content table corresponding to the second cross - section position of the cross - section of the positive electrode sheet.

[0094] Figure 7 It is the XPS full - spectrum diagram of a certain position on the positive electrode surface.

[0095] Figure 8 It is the tof - sims positive and negative ion spectra of the first position of the positive electrode dressing.

[0096] Figure 9 It is the first tof - sims 3D positive and negative ion spectra of the second position of the positive electrode dressing.

[0097] Figure 10 It is the second tof - sims 3D positive and negative ion spectra of the second position of the positive electrode dressing.

[0098] Figure 11 It is the comparison diagram of X - ray diffraction scans of the positive electrode material on the surface of the positive electrode sheet.

[0099] Figure 12 It is the differential scanning calorimetry spectrum of the mixture of the positive electrode material and the electrolyte on the surface of the positive electrode sheet.

[0100] Figure 13 It is the EIS diagram of the battery assembled from six positive electrode sheet samples assembled from the positive electrode sheet.

[0101] Figure 14 These are SEM images of different positions on the surface of the negative electrode plate.

[0102] Figure 15 These are the SEM image, elemental distribution map, and elemental content table of one of the surface positions on the surface of the negative electrode plate.

[0103] Figure 16 These are SEM images of different positions on the cross-section of the negative electrode plate.

[0104] Figure 17 These are the SEM image and elemental distribution map of the first cross-sectional position on the cross-section of the negative electrode plate.

[0105] Figure 18 These are the SEM image, elemental distribution map, and elemental content table of the second cross-sectional position on the cross-section of the negative electrode plate.

[0106] Figure 19 These are the X-ray photoelectron spectra of the negative electrode plate.

[0107] Figure 20 These are the TOF-SIMS surface ion images of the negative electrode plate.

[0108] Figure 21 These are the first TOF-SIMS depth profiling three-dimensional simulation images of the negative electrode plate.

[0109] Figure 22 These are the second TOF-SIMS depth profiling three-dimensional simulation images of the negative electrode plate.

[0110] Figure 23 These are the high-resolution TEM images of the negative electrode material on the negative electrode plate.

[0111] Figure 24 These are the ion chromatograms of the electrolyte.

[0112] Figure 25 These are the gas chromatography-mass spectrometry chromatograms of the electrolyte.

[0113] Figure 26 These are the infrared spectra of the non-coated surface of the separator.

[0114] Figure 27 These are the SEM images of the cross-section of the separator.

[0115] Figure 28 These are the SEM image, elemental distribution map, and elemental content table of the cross-section of the elemental analysis region of the separator.

[0116] Figure 29 These are the XPS images of the non-coated surface of the separator.

[0117] Figure 30 These are the XPS images of the coated surface of the separator.

[0118] Figure 31 It is the TMA test curve graph of the separator. Specific implementation manners

[0119] The technical solution of the present invention will be further described below through specific implementation manners. Those skilled in the art should understand that the embodiments are only for helping to understand the present invention and should not be regarded as specific limitations on the present invention.

[0120] Embodiment

[0121] This embodiment provides a method for improving the electrochemical performance and mechanical performance of a semi-solid energy storage cell, and the method includes:

[0122] (1) Testing the positive electrode sheet, negative electrode sheet, electrolyte and separator of the semi-solid energy storage cell respectively;

[0123] Testing of the positive electrode sheet:

[0124] First, analysis of the composition and morphology of the surface and cross-section:

[0125] To characterize the microscopic morphology and composition of the surface material of the positive electrode sheet, the sample to be tested is cut in a glove box and pasted on the sample stage with conductive glue, and then sealed and transferred to the SEM electron microscope; a scanning electron microscope (SEM) and an energy dispersive spectrometer (EDS) are used to observe the microscopic morphology and analyze the composition of the surface of the positive electrode sheet. When using the scanning electron microscope to test the positive electrode sheet, the acceleration voltage of the scanning electron microscope is set to 5 kV and the vacuum degree is 0.5×10 -3 Pa, and the SEM images of different positions on the surface of the positive electrode sheet are obtained as Figure 1 shown; the SEM image of the first position on the surface of the positive electrode sheet is obtained as Figure 2 shown, the element distribution map corresponding to the first position is as Figure 2 shown, and the element content table corresponding to the first position is as Figure 2 shown; the SEM image of the second position on the surface of the positive electrode sheet is obtained as Figure 3 shown, the element distribution map corresponding to the second position is as Figure 3 shown, and the element content table corresponding to the second position is as Figure 3 shown;

[0126] It can be seen from Figures 1 - 3 that the main elements on the surface of the positive electrode sheet are several elements such as C, O, F, P and Fe; as shown by the energy spectrum data, in addition to the common C, O, P, Fe elements in the positive electrode of the lithium iron phosphate system, there are also a small amount of Al and Ti elements;

[0127] To obtain the composition and thickness information of the current collector and its auxiliary materials of the positive electrode plate, an ion milling instrument (CP) was used to cut the positive electrode plate to prepare a smooth cross-section for analysis. A scanning electron microscope (SEM) was used to observe the microtopography and accurately measure the size, and at the same time, an energy-dispersive spectrometer (EDS) was used for composition analysis. The SEM images at different cross-section positions are as follows Figure 4 shown; the SEM image corresponding to the first cross-section position of the positive electrode plate cross-section is as follows Figure 5 shown, and the element distribution map corresponding to the first cross-section position is as follows Figure 5 shown; the SEM image corresponding to the second cross-section position of the positive electrode plate cross-section is as follows Figure 6 shown, the element distribution map corresponding to the second cross-section position is as follows Figure 6 shown, and the element content table corresponding to the second position is as follows Figure 6 shown; from Figures 4 - 6 it can be obtained that the positive electrode current collector uses aluminum foil, the thickness of the aluminum foil is about 12 μm, the main components of the positive electrode dressing are several elements such as C, O, P, and Fe. Combining with the analysis results of the surface composition of the electrode plate, the main active material of the positive electrode is lithium iron phosphate; combining with the surface composition analysis results, carbon nanotube conductive agents are added to the positive electrode dressing; in addition, in addition to C, O, P, and Fe elements, there are also a small amount of Al and Ti elements in the bulk phase;

[0128] Second, X-ray photoelectron spectroscopy surface composition analysis:

[0129] To characterize the surface material composition of the positive electrode plate, X-ray photoelectron spectroscopy (XPS) was used for surface composition analysis. When using X-ray photoelectron spectroscopy to test the positive electrode plate, the energy resolution of the X-ray photoelectron spectroscopy was set to 0.2 eV, and the XPS full-spectrum diagram at a certain position on the positive electrode surface is as follows Figure 7 shown; from Figure 7 it can be obtained that the surface of the positive electrode plate mainly contains elements such as Li, C, O, P, and Fe, which is consistent with the analysis results of the EDS Mapping image in the surface and cross-section composition and morphology analysis;

[0130] Third, time-of-flight secondary ion mass spectrometry surface and depth composition analysis:

[0131] To characterize the dressing composition of the positive electrode plate, time-of-flight secondary ion mass spectrometry (tof-sims) was used for surface and depth analysis. The vacuum degree of the time-of-flight secondary ion mass spectrometry was set to 1×10 -7 Pa, and the tof-sims positive and negative ion spectra at the first position of the positive electrode dressing as shown in Figure 8 were obtained, the first tof-sims 3D positive ion spectrum at the second position of the positive electrode dressing as shown in Figure 9 was obtained, and Figure 10The second TOF-SIMS 3D negative ion spectrogram of the second position of the positive electrode dressing shown;

[0132] It can be seen from Figure 8 that the positive electrode dressing contains molecular fragments composed of elements such as H, Li, C, O, N, P, Fe, Ti, and Al. By comparing the mass spectrograms at different depths, the trend of element distribution with depth can be observed; from Figure 9 and Figure 10 it can be seen that as the depth increases, the signal intensity of some elements gradually weakens, indicating that these elements are enriched on the surface; in addition, by analyzing the mass spectrograms at different depths, a deeper understanding of the chemical structure and element distribution of the positive electrode material can be obtained;

[0133] In Figure 9 and Figure 10 it is particularly noted that the signal intensity of the Li element is relatively high near the surface, while it significantly decreases inside the material, indicating that the Li element has a high enrichment degree on the surface of the positive electrode material, which may be closely related to the electrochemical performance of the material. At the same time, the C element shows a stable signal intensity throughout the depth range, suggesting that it plays a role of uniform distribution in the positive electrode material. The distribution of the O element shows a certain degree of volatility, which may be related to the oxidation state or surface treatment of the material. Through these analyses, a scientific basis can be provided for optimizing the preparation process of the positive electrode material and improving the battery performance;

[0134] Furthermore, Figure 9 and Figure 10 the change in the signal intensity of the P element reveals its non-uniform distribution in the positive electrode material; on the surface layer of the material, the signal intensity of the P element is relatively high, while it decreases in the deep layer, which may be related to the chemical bonding state of the P element in the positive electrode material. The signal intensity of the Fe element changes little at different depths, indicating that it is relatively uniformly distributed throughout the positive electrode material. The signal intensities of Ti and Al elements are relatively low, but their presence in the material can still be observed, which may be related to impurities or additives introduced during the synthesis process of the positive electrode material. By synthesizing the distribution characteristics of these elements, the microstructure of the positive electrode material and its influence on the battery performance can be speculated, providing a direction for subsequent material modification and battery performance optimization;

[0135] In Figure 9 and Figure 10Among them, the change in the signal intensity of the Mn element also shows a certain regularity. It reaches a peak in the middle layer region of the material and is relatively low in the surface and deep layers. This distribution pattern may be related to the specific role of the Mn element in the cathode material, such as participating in the electrochemical reaction or affecting the thermal stability of the material. In addition, the signal intensity of the Ni element is relatively stable throughout the depth range, but compared with the Fe element, its signal intensity is lower, which may reflect that the content of the Ni element in the cathode material is less, or its distribution in the material is more uniform. Through these observations, the mechanism of action of each element in the cathode material can be further understood, as well as how they jointly affect the overall performance of the battery. These findings have important guiding significance for the design and preparation of cathode materials with better electrochemical performance;

[0136] Fourth, X-ray powder diffraction composition analysis:

[0137] To characterize the composition of the cathode material on the surface of the cathode electrode, X-ray powder diffraction (XRD) was used for phase structure analysis. The scanning range of the X-ray powder diffractometer was set to 10-90°, and the X-ray diffraction scanning pattern comparison map of the cathode material was obtained as Figure 11 shown. From Figure 11 it can be seen that the main active substance of the cathode electrode is lithium iron phosphate;

[0138] Fifth, differential scanning calorimetry analysis:

[0139] To characterize the thermal safety of the cathode material and the electrolyte on the surface of the cathode electrode, a high-pressure crucible was used for sample preparation, and differential scanning calorimetry (DSC) was used for thermal analysis. The temperature range of the differential scanning calorimeter was set to 25-400°C and the heating rate was 5°C / min, and the differential scanning calorimetry map of the mixture of the cathode material and the electrolyte was obtained as Figure 12 shown. From Figure 12 it can be seen that a strong exothermic reaction occurs in the mixture of the cathode dressing and the electrolyte at 220°C;

[0140] Sixth, surface density and tap density analysis:

[0141] To characterize the surface density and tap density of the cathode electrode, a precision electronic balance and a vernier caliper were used to measure the mass and volume of the cathode electrode, and its density was calculated accordingly. The test data obtained are shown in Table 1 and Table 2; from Table 1 and Table 2, it can be seen that the average surface density of the double-sided coating of the cathode electrode is 35.8 mg / cm 2 , and the average tap density is 2.12 g / cm 3 ;

[0142] Table 1

[0143]

[0144] Table 2

[0145]

[0146] Seventh, specific capacity and EIS analysis:

[0147] To characterize the specific capacity of the positive electrode sheet, the positive electrode sheet was assembled into a coin cell, and charge-discharge tests were carried out using a battery tester. The BlueTEC battery test system was used with a voltage range of 3.0 - 4.3 V and a current density of 0.1 C. The specific capacity data of the positive electrode sheet obtained from the tests are shown in Table 3. From Table 3, it can be seen that under standard charge-discharge conditions, the average charge specific capacity of the positive electrode sheet reaches 155 mAh / g, the average discharge specific capacity reaches more than 165 mAh / g, and the initial Coulombic efficiency is greater than 100%. In addition, through electrochemical impedance spectroscopy (EIS) tests, with the frequency range set at 100 kHz - 10 mHz and the amplitude at 5 mV, the EIS spectra of the batteries assembled from six positive electrode sheet samples are as shown Figure 13 and are similar to the charge transfer resistance of conventional lithium iron phosphate materials;

[0148] Table 3

[0149]

[0150]

[0151] Testing of the negative electrode sheet:

[0152] First, analysis of the composition and morphology of the surface and cross-section:

[0153] To characterize the microscopic morphology and composition of the surface material of the negative electrode sheet, a scanning electron microscope (SEM) and an energy dispersive spectrometer (EDS) were used for microscopic morphology observation and composition analysis. The acceleration voltage of the scanning electron microscope was set at 5 kV and the vacuum degree at 0.5×10 -3 Pa, and the SEM images of different positions on the surface of the negative electrode sheet were obtained as shown Figure 14 ; the SEM image of one surface position on the surface of the negative electrode sheet was obtained as shown Figure 15 , the corresponding element distribution map of this position is as shown Figure 15 , and the corresponding element content table of this position is as shown Figure 15 ; from Figure 14 it can be seen that the negative electrode active material used in the battery is artificial graphite, and conductive carbon black is used as the conductive agent; from Figure 15 it can be seen that the surface of the negative electrode sheet mainly contains elements such as C, O, F, and P;

[0154] To understand the composition and thickness information of the negative electrode sheet, an ion milling instrument (CP) was used to cut the negative electrode sheet to prepare a smooth cross-section; SEM was used for microscopic morphology observation and size measurement, and EDS was used for composition analysis. The SEM images of different positions on the cross-section of the negative electrode sheet are as follows Figure 16 shown; the SEM image of the first cross-section position on the cross-section of the negative electrode sheet is as follows Figure 17 shown, and the corresponding elemental distribution map at this position is as follows Figure 17 shown; the SEM image of the second cross-section position on the cross-section of the negative electrode sheet is as follows Figure 18 shown, and the corresponding elemental distribution map at this position is as follows Figure 18 shown, and the corresponding elemental content table at this position is as follows Figure 18 shown; from Figure 16 it can be obtained that the negative electrode current collector uses copper foil, the thickness of the aluminum foil is about 6 μm, and the thickness of the negative electrode coating is about 70 μm; from Figure 17 and Figure 18 it can be obtained that the main components of the negative electrode dressing are several elements such as C, O, F, and P;

[0155] Second, X-ray photoelectron spectroscopy surface composition analysis:

[0156] To characterize the surface material composition of the negative electrode sheet, X-ray photoelectron spectroscopy (XPS) was used for surface composition analysis. The energy resolution of the X-ray photoelectron spectroscopy was set to 0.2 eV, and the X-ray photoelectron spectrum of the negative electrode sheet was obtained as follows Figure 19 shown. From Figure 16 it can be obtained that the surface of the negative electrode sheet mainly contains elements such as C, O, F, Li, and P, which is consistent with the composition analysis results of the surface and cross-section;

[0157] Third, time-of-flight secondary ion mass spectrometry surface and depth composition analysis:

[0158] To characterize the composition of the negative electrode sheet dressing, time-of-flight secondary ion mass spectrometry (TOF-SIMS) technology was used for surface and depth analysis. The vacuum degree of the time-of-flight secondary ion mass spectrometry was set to 1×10 -7 Pa, and the TOF-SIMS surface ion image of the negative electrode sheet was obtained as follows Figure 20 shown, and the TOF-SIMS depth profiling three-dimensional simulation image of the negative electrode sheet was obtained as follows Figure 21 and 22 shown; from Figure 21 and 22 it can be obtained that the surface of the negative electrode sheet mainly contains elements such as C, O, F, Li, and P, which is consistent with the analysis results of the EDS Mapping image;

[0159] Fourth, crystal structure and interface analysis:

[0160] To deeply understand the microstructure of the negative electrode material on the negative electrode plate, the crystal structure and interface were analyzed in detail using a transmission electron microscope (TEM). The acceleration voltage of the transmission electron microscope was set to 100 kV and the vacuum degree was 1×10 -5 Pa, and the high-resolution TEM image of the negative electrode material on the negative electrode plate as shown in Figure 23 was obtained. The lattice fringes inside the negative electrode material were clearly revealed. It can be seen that there is an amorphous region of about 5 - 10 nm on the surface of the negative electrode material, which is the SEI film;

[0161] In summary, through a series of analyses of the microstructure and electrochemical properties, a more comprehensive understanding of the characteristics of the negative electrode plate was obtained. These research results not only help to understand the internal working mechanism of the negative electrode plate, but also provide a scientific basis for further improving and optimizing the negative electrode plate;

[0162] Testing of the electrolyte:

[0163] First, inductively coupled plasma spectroscopy was used to test the elemental composition of the electrolyte:

[0164] The elemental composition of the electrolyte was tested using inductively coupled plasma spectroscopy. The radio frequency power of the inductively coupled plasma spectroscopy was set to 1400 W and the atomizing gas flow rate was 0.6 L / min. The test results showed that the Li element content was about 5600 mg / kg and the P element content was about 25000 mg / kg.

[0165] Second, ion chromatography was used to test the inorganic salts in the electrolyte:

[0166] The inorganic salt components of the electrolyte were tested using an ion chromatograph. The ion chromatogram of the electrolyte is as shown in Figure 24 ; It can be obtained from Figure 24 that the inorganic salt in the electrolyte is lithium hexafluorophosphate;

[0167] Third, gas chromatography - mass spectrometry was used to test the organic solvents in the electrolyte:

[0168] The organic solvents in the electrolyte were tested using gas chromatography - mass spectrometry. The gas chromatography - mass spectrum of the electrolyte is as shown in Figure 25 ; It can be obtained from Figure 25 that the organic solvents in the electrolyte include DMC, EMC, VC, DEC, FEC, and EC;

[0169] Based on the above results, it can be known that a mixed organic solvent system was selected in the tested electrolyte. Among them, DMC (dimethyl carbonate), EC (ethylene carbonate), and VC (vinyl carbonate) are the main solvents, DEC (diethyl carbonate) and FEC (fluoroethylene carbonate) are the auxiliary solvents, and the inorganic electrolyte salt is lithium hexafluorophosphate;

[0170] Testing of the separator:

[0171] First, infrared spectroscopy test:

[0172] The infrared spectroscopy test of the separator is to determine its chemical structure and molecular composition by analyzing the absorption characteristics of the material to infrared light. Through the infrared attenuated total reflection (ATR) technique, the separator was tested, and the infrared spectrogram of the non-coated surface of the separator is as shown in Figure 26 ; It can be seen from Figure 26 that the main material of the separator is polyethylene (PE);

[0173] Second, cross-section composition and morphology analysis:

[0174] To characterize the microscopic morphology and composition of the cross-section material of the separator, a cryogenic grinder was used for cross-section sample preparation, and a scanning electron microscope (SEM) and an energy dispersive spectrometer (EDS) were used for microscopic morphology observation and composition analysis. The acceleration voltage of the scanning electron microscope was set to 5 kV and the vacuum degree was 0.5×10 -3 Pa, and the SEM image of the cross-section of the separator is as shown in Figure 27 ; The SEM image of the cross-section of the element analysis area of the separator is as shown in Figure 28 ; The corresponding element distribution map at this position is as shown in Figure 28 ; The corresponding element content table at this position is as shown in Figure 28 ;

[0175] It can be seen from Figure 27 and Figure 28 that the separator is a single-layer porous structure, there is a coating layer on the surface of the separator, the thickness of the separator body is about 8.65 μm, the thickness of the coating layer is about 3.19 μm, the overall thickness of the separator is about 12 μm, the main body of the separator is polyethylene (PE), and the composition of the coating layer is aluminum oxide (Al2O3);

[0176] Third, X-ray photoelectron spectroscopy surface composition analysis:

[0177] To characterize the surface material composition of the separator, X-ray photoelectron spectroscopy (XPS) was used for surface composition analysis. The energy resolution of the X-ray photoelectron spectroscopy was set to 0.2 eV, and the XPS spectra of the non-coated surface of the separator are as shown in Figure 29 ; The XPS spectra of the coated surface of the separator are as shown in Figure 30 . It can be known from Figure 29 and Figure 30 that the surface of the separator mainly contains C element, and the coating layer of the separator mainly contains C, O, Al, and F elements. In addition to the conventional binder and electrolyte components, the main component of the coating layer is aluminum oxide (Al2O3);

[0178] Fourth, separator puncture strength analysis:

[0179] To characterize the puncture strength of the separator, the standard of "GB / T 37841-2019 Test Method for Puncture Resistance of Plastic Films and Sheets - Puncture Test Method" was adopted. By applying a pressure perpendicular to the surface on the separator until it was penetrated, the test results of the puncture strength of the separator were obtained as shown in Table 4. The test results showed that the puncture strength of the separator was 0.47 kN / mm;

[0180] Table 4

[0181]

[0182]

[0183] Fifth, analysis of the tensile strength of the separator:

[0184] To characterize the tensile strength of the separator, the standard of "GB / T 1040.3-2006 Determination of Tensile Properties of Plastics - Part 3: Test Conditions for Films and Sheets" was adopted. By applying a tensile force parallel to the surface of the separator until it broke, the tensile strength of the separator was measured. The test results of the tensile strength of the separator were obtained as shown in Table 5. The test results showed that the tensile strength of the separator was 194 MPa;

[0185] Table 5

[0186]

[0187] Sixth, analysis of the closure temperature and rupture temperature of the separator:

[0188] To characterize the closure temperature and rupture temperature of the separator, a thermomechanical analyzer was used to heat the separator and observe the changes in its physical state at different temperatures; by setting the heating rate and constant temperature time, the temperature range from the initial closed state to the fully closed state of the separator was recorded, and the temperature interval from the closed state to the rupture state was recorded. The TMA test curve graph of the separator obtained from the test was as shown in Figure 31 shown; from Figure 31 it could be obtained that the closure temperature of the separator was 126.46 °C and the rupture temperature was 145.38 °C;

[0189] (2) According to the results obtained from the test in step (1), the positive electrode sheet, negative electrode sheet, electrolyte, and separator were respectively improved to obtain the improved positive electrode sheet, improved negative electrode sheet, improved electrolyte, and improved separator; then the obtained improved positive electrode sheet, improved negative electrode sheet, improved electrolyte, and improved separator were assembled into a battery to obtain a semi-solid energy storage cell with improved performance;

[0190] The improvement method is as follows:

[0191] When the electrochemical impedance of the positive electrode sheet obtained in step (1) is greater than 50 Ω·cm 2When the specific capacity is lower than 140 mAh / g and / or the gram capacity is lower than 140 mAh / g, the preparation process of the positive electrode sheet is designed according to the surface morphology, surface element distribution, cross-sectional morphology, cross-sectional element distribution, surface composition, and the change of element distribution with the depth of the electrode sheet of the positive electrode sheet.

[0192] When the SEI film is lower than 5 nm in the interface morphology diagram of the negative electrode sheet obtained in step (1), the preparation process of the negative electrode sheet is designed according to the surface morphology, surface element distribution, cross-sectional morphology, cross-sectional element distribution, surface composition, the change of element distribution with the depth of the electrode sheet, and the crystal structure of the negative electrode material of the negative electrode sheet.

[0193] When the separator in step (1) meets any one or at least two of the following conditions: the average puncture resistance is lower than 0.4 kN / mm, the average tensile strength is lower than 180 MPa, the closed pore temperature is lower than 110 °C, or the breakdown temperature is lower than 130 °C, the preparation process of the separator is designed according to the chemical structure, molecular composition, surface morphology, surface element distribution, and surface composition of the separator.

[0194] During the test process described in this embodiment, the instruments used include:

[0195] Scanning Electron Microscopy (SEM): Secondary electrons are generated by the interaction of high-energy electron beams with the sample, and the secondary electrons reflect the microscopic morphology information of the sample.

[0196] Energy Dispersive Spectrometer: By using the phenomenon that different characteristic photon energies are generated when X-rays act on different elements, the element content and distribution of the sample points, lines, and surfaces are measured.

[0197] Transmission Electron Microscope (TEM): It is a microscopic technique that uses an electron beam to penetrate the sample and form an image. It passes the electron beam through an extremely thin sample and uses the scattering and absorption of the electron beam by the sample to form an image, so that the internal structure of the sample can be observed, and the resolution is much higher than that of an optical microscope.

[0198] X-ray Photoelectron Spectroscopy (XPS): When high-energy X-ray photons act on the sample surface, photoelectrons are excited on the sample surface. Electrons of different elements have specific binding energies. By measuring the binding energies of these photoelectrons, the element composition and chemical state of the sample surface can be analyzed.

[0199] X-ray Photoelectron Spectroscopy (XPS) is a technique that, when high-energy X-ray photons act on the surface of a sample, excites photoelectrons on the sample surface. Electrons of different elements have specific binding energies. By measuring the binding energies of these photoelectrons, the elemental composition and chemical state of the sample surface can be analyzed. The XPS used in this project research is the 5000VersaProbe4 model produced by PHI Company of Japan.

[0200] Time-of-Flight Secondary Ion Mass Spectrometry (TOF-SIMS): When the primary ions generated by the equipment bombard the sample surface, secondary ions are produced. Secondary ions with different mass-to-charge ratios have different flight speeds, and the mass spectrometry data collected by the detector can reflect the sample composition information; TOF-SIMS is very sensitive to elements and can detect from element 1 (H) in the periodic table. Moreover, it has extremely high resolution for the molecular structure and chemical state of the sample surface, can detect elements at the ppm level, and at the same time it can provide depth profiling and surface analysis, and is suitable for analyzing the micro-area composition and chemical state of solid materials.

[0201] X-ray diffraction (XRD): It is a testing tool based on Bragg's diffraction law to characterize the phase structure of materials.

[0202] Raman spectra (RAMAN): It is a testing tool used to analyze the vibration and rotation information of molecules in a substance.

[0203] Fourier Transform Infrared Spectroscopy (FTIR): It is a testing tool that analyzes the molecular structure and chemical bonds of a substance by measuring its absorption, transmission, or reflection of infrared light.

[0204] Inductively Coupled Plasma Optical Emission Spectrometry (ICP-OES): It is an elemental quantitative analysis tool based on spectral technology and can quantitatively measure most metal elements and some non-metal elements.

[0205] Ion Chromatography (IC): It is an analytical instrument used to separate and detect ions in a solution. It uses the principle of ion exchange and separates cations or anions in the sample through specific ion exchange resins.

[0206] Gas Chromatography-Mass Spectrometry (GC-MS): An analytical instrument that combines a gas chromatograph (GC) and a mass spectrometer (MS). It can separate, identify, and quantitatively analyze compounds in complex mixtures.

[0207] Atomic Force Microscope (AFM): A microscopic technique that uses the intermolecular forces between atoms to obtain information about the surface topography, mechanical properties, magnetism, etc. of a sample.

[0208] Ion Mill (Cross Section Polisher, CP): A new type of sample processing equipment that uses ion beam technology to finely cut and polish samples to obtain high-quality sample cross-sections. The ion mill is particularly suitable for materials science and electron microscopy research that requires high-precision surface analysis. CP can reduce damage during sample preparation, maintain the original structure of the sample, and thus provide more accurate analysis results.

[0209] Differential Scanning Calorimeter (DSC): An instrument that measures the heat absorbed or released by a substance during heating or cooling. Through DSC analysis, thermodynamic properties such as the melting point, crystallinity, and thermal stability of materials can be obtained. In the present invention, a high-pressure crucible is used to mix the active material and the electrolyte to simulate the heat absorption and release of the battery under actual use conditions.

[0210] Thermomechanical Analyzer (TMA): Used to measure the dimensional changes of materials during heating or cooling to evaluate their thermal expansion coefficients and thermal stabilities. By precisely measuring the changes in the length, thickness, or width of the sample, TMA can provide information on the physical properties of materials at different temperatures.

[0211] Universal Testing Machine: Used to test the mechanical properties of materials, including tension, compression, bending, and shear, etc. By precisely controlling the loading speed and measuring the deformation of the sample, the stress-strain curve of the material can be obtained, thereby analyzing its mechanical parameters such as elastic modulus, yield strength, and tensile strength.

[0212] Battery Tester: A device specifically used to evaluate the performance of batteries. It can simulate the charging and discharging process of batteries under actual use conditions and measure key parameters such as the voltage, current, capacity, and internal resistance of the batteries.

[0213] Electrochemical workstation: It is a precision instrument used for electrochemical research and testing. It can provide stable potential and current for controlling and measuring the electrochemical reaction process. Through the electrochemical workstation, various electrochemical tests such as cyclic voltammetry, potential step, and electrochemical impedance spectroscopy can be carried out to obtain the electrochemical performance parameters of materials, such as electrochemical stability, reaction kinetic constants, etc.

[0214] Electronic balance: It is a high-precision weighing device widely used in laboratories and industrial fields. It can accurately measure extremely small mass changes, which is crucial for occasions with strict quality requirements in the research and production processes.

[0215] Vernier caliper: It is a precision measuring tool used to measure dimensions such as length, internal and external diameters, depth, and step height. It consists of a main scale and a slidable vernier. The precise measurement value is obtained by reading the scale difference between the main scale and the vernier. The accuracy of the vernier caliper can usually reach 0.02 mm, which is very useful for occasions that require precise dimension measurement.

[0216] The above are only the specific embodiments of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily thought of by those skilled in the art within the technical scope disclosed by the present invention fall within the protection scope and the disclosure scope of the present invention.

Claims

1. A method for improving the electrochemical and mechanical properties of a semi-solid energy storage cell, characterized in that: The method comprises: (1) Test the positive electrode, negative electrode, electrolyte and diaphragm of the semi-solid energy storage cell respectively; After the test, the surface morphology, surface element distribution, cross-sectional morphology, cross-sectional element distribution, surface component composition, change of element distribution with the depth of the electrode, XRD composition, differential thermal performance, surface density, compacted density, gram capacity and electrochemical impedance of the positive electrode are obtained; After the test, the surface morphology, surface element distribution, cross-sectional morphology, cross-sectional element distribution, surface component composition, change of element distribution with the depth of the electrode, crystal structure and interface morphology of the negative electrode material are obtained; After the test, the element composition of the inorganic salt, the type of the inorganic salt and the type of the organic solvent in the electrolyte are obtained; After the test, the chemical structure, molecular composition, surface morphology, surface element distribution, surface component composition, puncture strength, tensile strength, closed-cell temperature and rupture temperature of the diaphragm are obtained; (2) According to the test results obtained in step (1), the positive electrode sheet, the negative electrode sheet, the electrolyte and the separator are improved respectively to obtain an improved positive electrode sheet, an improved negative electrode sheet, an improved electrolyte and an improved separator; and the obtained improved positive electrode sheet, improved negative electrode sheet, improved electrolyte and improved separator are assembled into a battery to obtain a semi-solid energy storage cell with improved performance; The improved method comprises: When the electrochemical impedance of the positive electrode obtained in step (1) is greater than 50Ω·cm 2 When the gram capacity is lower than 140 mAh / g, the positive electrode sheet preparation process is designed according to the surface morphology, surface element distribution, cross-sectional morphology, cross-sectional element distribution, surface component composition, and the variation of element distribution with the depth of the positive electrode sheet; When the SEI film is less than 5 nm in the interface morphology of the negative electrode obtained in step (1), the preparation process of the negative electrode is designed according to the surface morphology, surface element distribution, cross-sectional morphology, cross-sectional element distribution, surface component composition, change of element distribution with the depth of the electrode and the crystal structure of the negative electrode material; When the diaphragm in step (1) meets any one or at least two of the following conditions: an average puncture resistance strength lower than 0.4 kN / mm, an average tensile strength lower than 180 MPa, a closed-cell temperature lower than 110°C, or a rupture temperature lower than 130°C, the preparation process of the diaphragm is designed according to the chemical structure, molecular composition, surface morphology, surface element distribution, and surface component composition of the diaphragm.

2. The method according to claim 1, characterized in that During the test, the test method of the positive electrode plate includes: The surface morphology, surface element distribution, cross-sectional morphology and cross-sectional element distribution of the positive electrode were tested using a scanning electron microscope; X-ray photoelectron spectroscopy was used to test the surface composition of the positive electrode. Time-of-flight secondary ion mass spectrometry was used to test the surface element distribution of the positive electrode and the change of element distribution with the depth of the electrode; The XRD composition of the positive electrode piece was tested using an X-ray powder diffractometer; The differential thermal performance of the positive electrode was tested using a differential thermal scanner; Use precision electronic balance and vernier caliper to test the surface density and compaction density of the positive electrode; The gram capacity of the positive electrode sheet is tested by charge and discharge test; The electrochemical impedance of the positive electrode was tested by electrochemical impedance spectroscopy.

3. The method according to claim 2, characterized in that When using a scanning electron microscope to test the positive electrode, set the acceleration voltage of the scanning electron microscope to 5-20 kV and the vacuum degree ≤ 1×10 -3 Pa; When using X-ray photoelectron spectroscopy to test the positive electrode, set the energy resolution of the X-ray photoelectron spectroscopy to ≤ 0.5 eV; When using time-of-flight secondary ion mass spectrometry to test the positive electrode, set the vacuum degree of the time-of-flight secondary ion mass spectrometry to ≤5×10 -7 Pa; When the positive electrode sheet is tested by an X-ray powder diffractometer, the scanning range of the X-ray powder diffractometer is set to 10-90°; When the positive electrode is tested by a differential calorimeter, the temperature range of the differential calorimeter is set to 25-400°C and the heating rate is set to 1-20°C / min; When charging and discharging the positive electrode, the blue battery test system is used, with a voltage range of 3.0 to 4.3V and a current density of 0.1 to 0.5C; When performing electrochemical impedance spectroscopy testing on the positive electrode, the frequency range is set to 100kHz~10mHz and the amplitude is 5mV.

4. The method according to claim 1, characterized in that: During the test, the negative electrode plate test method includes: The surface morphology, surface element distribution, cross-sectional morphology, and cross-sectional element distribution of the negative electrode were tested using a scanning electron microscope; X-ray photoelectron spectroscopy was used to test the surface composition of the negative electrode; Time-of-flight secondary ion mass spectrometry was used to test the surface element distribution of the negative electrode and the change of element distribution with the depth of the electrode; Transmission electron microscopy was used to test the crystal structure and interface morphology of the negative electrode material on the negative electrode sheet.

5. The method according to claim 4, characterized in that When the negative electrode is tested by a scanning electron microscope, the acceleration voltage of the scanning electron microscope is set to 5-20 kV and the vacuum degree is ≤1×10-3Pa; When using X-ray photoelectron spectroscopy to test the negative electrode, set the energy resolution of the X-ray photoelectron spectroscopy to ≤ 0.5 eV; When the negative electrode is tested by time-of-flight secondary ion mass spectrometry, the vacuum degree of the time-of-flight secondary ion mass spectrometry is set to ≤5×10 -7 Pa; When the negative electrode is tested by transmission electron microscopy, the acceleration voltage of the transmission electron microscope is set to 80-300 kV and the vacuum degree is ≤5×10 -5 Pa.

6. The method according to claim 1, characterized in that During the test, the electrolyte test method includes: Inductively coupled plasma spectroscopy was used to test the elemental composition of inorganic salts in the electrolyte; The types of inorganic salts in the electrolyte are tested using an ion chromatograph; Gas chromatography-mass spectrometry was used to test the types of organic solvents in the electrolyte.

7. The method according to claim 6, characterized in that When the electrolyte is tested by inductively coupled plasma spectroscopy, the radio frequency power of the inductively coupled plasma spectroscopy is set to 1150-1500 W and the atomizing gas flow rate is set to 0.5-0.8 L / min.

8. The method according to claim 1, characterized in that During the test, the diaphragm test method includes: The chemical structure and molecular composition of the diaphragm were tested using infrared spectroscopy; The surface morphology and surface element distribution of the diaphragm were tested using a scanning electron microscope; X-ray photoelectron spectroscopy was used to test the surface composition of the diaphragm.

9. The method according to claim 8, characterized in that During the test, the diaphragm test method also includes: The puncture strength of the diaphragm is tested using a puncture test; The tensile strength of the diaphragm was tested using a tensile tester; The closed-cell temperature and rupture temperature of the diaphragm were tested using a mechanical analyzer.

10. The method according to claim 8, characterized in that When the diaphragm is tested by a scanning electron microscope, the acceleration voltage of the scanning electron microscope is set to 5-20 kV and the vacuum degree is ≤1×10-3Pa; When the diaphragm is tested by X-ray photoelectron spectroscopy, the energy resolution of the X-ray photoelectron spectroscopy is set to ≤ 0.5 eV.

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