Interface modification layer for solid-state lithium battery and preparation method thereof

Abstract

An interface modification layer for solid-state lithium batteries and its preparation method are disclosed. The interface modification layer comprises a rigid side enriched with lithium-ion conductive particles and a flexible side enriched with an organic matrix. The rigid side is used for contact with the negative electrode of the lithium battery, and the flexible side is used for contact with the positive electrode of the lithium battery. The components of the interface modification layer include: a carbonate-based liquid electrolyte, an organic polymer monomer, a crosslinking agent, an initiator, and lithium-ion conductive particles. This invention provides an interface modification layer that can be applied to solid-state lithium batteries, significantly improving the interfacial compatibility of the electrolyte / electrode, enhancing the ionic conductivity of the electrode itself, suppressing lithium dendrite growth, and has a simple preparation process, making it easy to apply on a large scale.

Description

Technical Field

[0001] This invention belongs to the field of solid-state lithium battery technology, specifically relating to an interface modification layer for solid-state lithium batteries and its preparation method. Background Technology

[0002] Lithium-ion batteries, characterized by high energy density and long lifespan, have garnered significant attention since their market introduction in 1991, finding widespread application in small and medium-sized batteries for mobile devices, emergency power systems, and hybrid electric vehicles. However, commercially available lithium-ion batteries using liquid electrolytes suffer from drawbacks such as leakage, flammability, and incompatibility with lithium metal. High-capacity solid-state lithium batteries, employing solid electrolytes, particularly inorganic ceramic materials, to replace liquid electrolytes, offer the potential to address the key issues of low energy density and short lifespan in traditional lithium-ion batteries, while also potentially resolving battery safety concerns. This makes them an ideal chemical power source for future electric vehicles and large-scale energy storage. In recent years, the numerous outstanding advantages exhibited by solid-state lithium batteries have attracted increasing international research and development efforts.

[0003] Unlike the unobstructed solid-liquid interface between liquid electrolytes and electrodes, the interface between solid electrolytes and electrodes is poor due to solid-solid contact and the lack of liquid wetting, resulting in higher interfacial resistance. On the negative electrode side, the limited electrochemically active "real" contact area between the solid electrolyte and the negative electrode leads to concentrated current density and large overpotentials during repeated lithium deposition / stripping. Uneven lithium deposition induces lithium dendrite growth that penetrates the solid electrolyte, causing premature failures such as battery short circuits and solid electrolyte cracking. On the positive electrode side, poor interfacial contact affects lithium-ion transport between the positive electrode and the solid electrolyte. Furthermore, the lack of liquid electrolyte wetting in the positive electrode sheet results in numerous gaps between internal particles, hindering its own lithium-ion conduction. Therefore, the problems to be solved on the negative electrode side are high interfacial resistance and lithium dendrite growth, while the problems to be solved on the positive electrode side are high interfacial resistance and insufficient ionic conductivity of the electrode sheet itself.

[0004] Introducing an interface modification layer is an effective solution. Based on mechanical properties, interface modification layers can be categorized into rigid and flexible layers. Rigid layers, including inorganic layers such as oxides, fluorides, and nitrides, as well as metal and alloy layers, can address the problems faced on the negative electrode side but struggle to solve the insufficient ionic conductivity of the positive electrode itself. Conversely, flexible layers, represented by polymer layers, can address the problems faced on the positive electrode side but cannot resist the growth of lithium dendrites on the negative electrode side. Furthermore, the overall fabrication process for these interface modification layers is complex and costly, employing methods such as physical vapor deposition or chemical vapor deposition, making them unsuitable for large-scale industrial applications. Therefore, a simple fabrication process is needed to obtain an interface modification layer that can simultaneously address the problems on both the positive and negative electrode sides. Summary of the Invention

[0005] To address the aforementioned problems, the present invention aims to provide an interface modification layer and its preparation method that can solve both the problems of high interface resistance and lithium dendrite growth on the negative electrode side, as well as the problems of poor interface contact and insufficient ionic conductivity of the electrode sheet itself on the positive electrode side. The preparation method is simple and easy to operate, and then it can be applied to solid-state lithium batteries.

[0006] On one hand, the present invention provides an interface modification layer for solid-state lithium batteries, comprising a rigid side and a flexible side. The rigid side is enriched with lithium-ion conductive particles and contacts the negative electrode of the lithium battery; the flexible side is enriched with an organic matrix and contacts the positive electrode of the lithium battery. The surface Young's modulus of the prepared interface modification layer is measured, and the average Young's modulus of the rigid side of the interface modification layer is 10-15 GPa, and the average Young's modulus of the flexible side is 0.1-5 GPa.

[0007] The interface modification layer is prepared from carbonate-based liquid electrolyte, organic polymer monomer, crosslinking agent, initiator and lithium-ion conductive particles;

[0008] The mass ratio of the carbonate-based liquid electrolyte, organic polymer monomer, crosslinking agent, initiator, and lithium-ion conductive particles is (90-100):(5-15):(1-5):(0.1-1):(1-100);

[0009] Preferably, the carbonate-based liquid electrolyte is selected from any one of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethanesulfonyl)imide, and lithium bis(oxalateborate), and is dissolved in ethylene carbonate EC, diethyl carbonate DEC, and dimethyl carbonate DMC in a volume ratio of 1:1:1 to form a solution with a concentration of 1 mol / L.

[0010] The organic polymer monomer is selected from any one of methyl methacrylate, ethyl methacrylate, isopropyl methacrylate, butyl methacrylate, and benzyl methacrylate, with a mass concentration of 98.0%-99.9%.

[0011] The crosslinking agent is selected from any one of ethylene glycol dimethacrylate, trimethylolpropane triacrylate, trimethylolpropane trimethacrylate, and ethylene glycol dimethacrylate, with a mass concentration of 98.0%-99.9%.

[0012] The initiator is selected from any one of azobisisobutyronitrile, azobisisoheptanenitrile, 4,4'-azobis(4-cyanopentanoic acid) and 2,2'-azobis(4-methoxy-2,4-dimethylpentanonitrile), with a mass concentration of 98.0%-99.9%.

[0013] Preferably, the lithium-ion conductive particles are selected from any one of garnet-type solid electrolytes, NASICON-type solid electrolytes, and perovskite-type solid electrolytes, and the particle size of the solid particles is 400-600 nm.

[0014] On the other hand, the present invention also provides a method for preparing an interface modification layer for solid-state lithium batteries, characterized by comprising the following steps:

[0015] (1) Mix carbonate-based liquid electrolyte, organic polymer monomer, crosslinking agent, initiator and lithium-ion conductive particles in proportion to obtain precursor solution;

[0016] (2) Coat the precursor solution obtained in step (1) onto the surface of the solid electrolyte in contact with the two electrodes, and then let it stand so that the conductive particles settle naturally due to gravity.

[0017] The solid electrolyte is a disc with a thickness of 1-2 mm and a diameter of 8-12 mm, selected from any one of garnet-type solid electrolyte, NASICON-type solid electrolyte, and perovskite-type solid electrolyte;

[0018] Preferably, the surface loading of the precursor solution is 5-15 μL / cm². 2 The settling time is 6-12 hours.

[0019] (3) Heat the solid electrolyte after step (2) to obtain the interface modification layer;

[0020] Preferably, the parameters for the heat treatment include: a heating temperature of 50-100℃ and a heating time of 1-12h.

[0021] Furthermore, based on the aforementioned interface modification layer, the present invention also provides a solid-state lithium battery, comprising a positive electrode shell, a negative electrode shell, a positive electrode sheet, a negative electrode sheet, nickel foam, a solid electrolyte, and the aforementioned interface modification layer. An interface modification layer is respectively disposed between the solid electrolyte and the positive and negative electrode sheets. The rigid side contacts the negative electrode sheet of the lithium battery, and the flexible side contacts the positive electrode sheet of the lithium battery. The assembly sequence from bottom to top is as follows: negative electrode shell - negative electrode sheet - interface modification layer - solid electrolyte - interface modification layer - positive electrode sheet - nickel foam - positive electrode shell.

[0022] Preferably, the positive electrode is any one of oxides, sulfur and its complexes, sulfides, and fluorides; the negative electrode is any one of metallic lithium, lithium alloys, graphite, silicon, and silicon-carbon; and the solid electrolyte is a garnet-type solid electrolyte (e.g., Li). 7-x La3Zr 2-x Ta x O 12 (0≤x≤2), NASICON-type solid electrolytes (e.g., Li1+y Al y Ge 2- y P3O 12 ,0≤y≤2), perovskite-type solid electrolytes (e.g., Li 3z La 2 / 3-z Any one of TiO3, 0≤z≤2 / 3).

[0023] The present invention also provides another solid-state lithium battery, the preparation method of which is as follows: after coating the precursor solution prepared in step (1) above onto the surface of the solid electrolyte in contact with the two electrodes, the battery is assembled in the following order from bottom to top: negative electrode shell - negative electrode sheet - precursor solution - solid electrolyte - precursor solution - positive electrode sheet - nickel foam - positive electrode shell. After standing, the battery is subjected to heat treatment to obtain a solid-state lithium battery modified with an interface modification layer; the standing time is 6-12h; the parameters of the heat treatment include: heating temperature of 50-100℃ and heating time of 1-12h.

[0024] Compared with existing technologies, this invention has significant advantages and beneficial effects. Through the above technical solution, the solid-state lithium battery interface modification layer, its preparation method, and its application achieve considerable technological advancement and practicality, and have broad application value. It possesses at least the following advantages:

[0025] (1) The precursor solution of the rigid-flexible interface modification layer of the present invention has good ionic conductivity. Before polymerization, it penetrates into the electrode sheet to build an ionic conductivity pathway on the surface of the active material particles. After polymerization, the positive / negative electrode sheet and the solid electrolyte are adhered together to form an integrated structure, which effectively improves the compatibility between the positive / negative electrode sheet and the solid electrolyte and reduces the interface impedance.

[0026] (2) The rigid-flexible interface modification layer of the present invention includes a rigid side enriched with lithium-ion conductive particles and a flexible side enriched with organic matrix. The rigid side is in contact with the negative electrode of the lithium battery, and the flexible side is in contact with the positive electrode of the lithium battery. The rigid side plays the role of inhibiting the growth of lithium dendrites and improving interface stability; the flexible side plays the role of conformal contact and improving interface contact characteristics.

[0027] (3) The rigid-flexible interface modification layer of the present invention has poor electronic conductivity, which can physically isolate the electron leakage at the interface between the electrode material and the solid electrolyte, avoid adverse electrochemical reactions between the two and the growth of lithium dendrites inside the solid electrolyte, improve the cycle stability of solid lithium battery, and provide more possibilities for its commercial application.

[0028] (4) The preparation process of the rigid-flexible interface modification layer of the present invention is simple, has low equipment requirements, is easy to apply on a large scale, is environmentally friendly, and has low cost.

[0029] The above description is merely an overview of the technical solution of the present invention. In order to better understand the technical means of the present invention and to implement it in accordance with the contents of the specification, and to make the above and other objects, features and advantages of the present invention more apparent and understandable, preferred embodiments are described in detail below with reference to the accompanying drawings. Attached Figure Description

[0030] Figure 1 This is a graph showing the Young's modulus measurement of the rigid side surface of the interface modification layer in Example 1;

[0031] Figure 2 This is a graph showing the Young's modulus measurement of the flexible side surface of the interface modification layer in Example 1;

[0032] Figure 3 The AC impedance spectrum of the solid-state lithium battery in Example 1;

[0033] Figure 4 The diagram shows the charge-discharge cycle of the solid-state lithium battery in Example 1 at 0.2C.

[0034] Figure 5 This is a charge-discharge cycle diagram of the solid-state lithium battery at 1C in Example 1;

[0035] Figure 6 The AC impedance spectrum of the solid-state lithium battery in Example 2;

[0036] Figure 7 The diagram shows the charge-discharge cycle of the solid-state lithium battery at 0.1C in Example 2.

[0037] Figure 8 The solid-state lithium battery in Example 3 is shown in the AC impedance spectrum.

[0038] Figure 9 The diagram shows the charge-discharge cycle of the solid-state lithium battery in Example 3 at 0.2C.

[0039] Figure 10 The AC impedance spectrum of the solid-state lithium battery in Example 4;

[0040] Figure 11 The diagram shows the charge-discharge cycle of the solid-state lithium battery at 0.2C in Example 4.

[0041] Figure 12 The AC impedance spectrum of the solid-state lithium battery in Example 5;

[0042] Figure 13 The diagram shows the charge-discharge cycle of the solid-state lithium battery in Example 5 at 0.2C.

[0043] Figure 14 The solid-state lithium battery in Example 7 is shown in the AC impedance spectrum.

[0044] Figure 15 The diagram shows the charge-discharge cycle of the solid-state lithium battery in Example 7 at 0.2C.

[0045] Figure 16 The AC impedance spectrum of the solid-state lithium battery in Example 8;

[0046] Figure 17 This is a charge-discharge cycle diagram of the solid-state lithium battery in Example 8 at 0.1C. Detailed Implementation

[0047] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the present invention will be clearly and completely described below in conjunction with specific embodiments and accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, not all of them. The embodiments described and shown in the accompanying drawings can generally be implemented through various different configurations. Therefore, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the claims, but merely to illustrate selected embodiments of the present invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

[0048] This invention does not impose any special restrictions on the source of any of the raw materials used; they can be commercially available or homemade. There are no special restrictions on their purity; the conventional purity required for preparing lithium batteries is sufficient.

[0049] The following detailed description uses specific examples:

[0050] Example 1

[0051] A method for preparing an interface modification layer for solid-state lithium batteries includes the following steps:

[0052] (1) Carbonate-based liquid electrolyte, methyl methacrylate, ethylene glycol dimethacrylate, azobisisobutyronitrile and Li 6.4 La3Zr 1.4 Ta 0.6 O 12 Lithium-ion conductive particles were mixed in a mass ratio of 100:10:3:0.3:50 to obtain a precursor solution;

[0053] The carbonate-based liquid electrolyte is a 1 mol / L solution formed by dissolving lithium hexafluorophosphate in ethylene carbonate EC, diethyl carbonate DEC and dimethyl carbonate DMC in a volume ratio of 1:1:1.

[0054] The methyl methacrylate has a mass concentration of 99.0%; the ethylene glycol dimethacrylate has a mass concentration of 98.0%; the azobisisobutyronitrile (AIBN) has a mass concentration of 99.0%; and Li 6.4 La3Zr 1.4 Ta 0.6 O 12 The solid particles of lithium-ion conductive particles have a particle size of 500 nm.

[0055] (2) Garnet-type solid electrolyte Li was prepared by solid-state sintering. 6.4 La3Zr 1.4 Ta 0.6 O 12 Ceramic sheet, the ceramic sheet is a round piece with a thickness of 1.0mm and a diameter of 1.0cm;

[0056] (3) The obtained precursor solution was coated on Li 6.4 La3Zr 1.4 Ta 0.6 O 12 The surface loading of the ceramic disc in contact with the two electrodes is 13 μL / cm. 2 Then let it stand for 8 hours, allowing the conductive particles to settle naturally due to gravity.

[0057] (4) The ceramic disc processed in step (3) is heated at 60°C for 6 hours to obtain the interface modification layer.

[0058] The Young's modulus of the prepared interface-modified layer was measured using atomic force microscopy, and the results are shown in the attached figure. Figure 1 and appendix Figure 2 As shown, the average Young's modulus of the rigid side of the interface modification layer is 12.7 GPa; the average Young's modulus of the flexible side is 2.6 GPa.

[0059] A solid-state lithium battery, the preparation method includes the following steps:

[0060] The precursor solution prepared in step (1) is coated onto the surface of the ceramic disc obtained in step (2) that is in contact with the two electrodes, with a surface loading of 13 μL / cm². 2 The order from bottom to top is: negative electrode shell - lithium metal foil - 10 μL precursor solution - Li 6.4 La3Zr 1.4 Ta 0.6 O 12A 2025-type coin cell was assembled in the following order: ceramic sheet - 10 μL precursor solution - LiFePO4 electrode sheet - nickel foam - positive electrode shell. The cells were then left to stand for 8 hours to allow the conductive particles to settle naturally under gravity. After standing, the cells were heated at 60°C for 6 hours to obtain a solid-state lithium battery modified with an interface modification layer based on in-situ polymerization. The lithium foil and the LiFePO4 electrode sheet were both 0.8 cm in diameter.

[0061] Battery performance evaluation: Electrochemical impedance spectroscopy (EIS) tests were performed on the assembled solid-state lithium battery at 25°C. The results are shown in the attached figure. Figure 3 As shown, the total impedance of the entire battery is 550Ω. A constant current charge-discharge test was performed on the battery at 25℃, with a charge-discharge cutoff voltage of 2.5-4.0V. The results are attached. Figure 4 As shown, after 150 cycles at 0.2C, the battery retains 97% of its discharge specific capacity and has a coulombic efficiency greater than 99%. (See attached diagram.) Figure 5 As shown, after 400 cycles at 1C, the battery retains approximately 90% of its discharge capacity and has a coulombic efficiency greater than 99%.

[0062] Example 2

[0063] A method for preparing an interface modification layer for solid-state lithium batteries includes the following steps:

[0064] (1) Carbonate-based liquid electrolyte, methyl methacrylate, ethylene glycol dimethacrylate, azobisisobutyronitrile and Li 6.4 La3Zr 1.4 Ta 0.6 O 12 Lithium-ion conductive particles were mixed in a mass ratio of 100:15:5:1:80 to obtain a precursor solution.

[0065] The carbonate-based liquid electrolyte is a 1 mol / L solution formed by dissolving lithium hexafluorophosphate in ethylene carbonate EC, diethyl carbonate DEC and dimethyl carbonate DMC in a volume ratio of 1:1:1.

[0066] The methyl methacrylate has a mass concentration of 99.0%; the ethylene glycol dimethacrylate has a mass concentration of 98.0%; the azobisisobutyronitrile (AIBN) has a mass concentration of 99.0%; and Li 6.4 La3Zr 1.4 Ta 0.6 O 12 The solid particles of lithium-ion conductive particles have a particle size of 500 nm.

[0067] (2) Garnet-type solid electrolyte Li was prepared by solid-state sintering. 6.4 La3Zr 1.4 Ta0.6 O 12 Ceramic sheet, the ceramic sheet is a round piece with a thickness of 1.2mm and a diameter of 1.1cm;

[0068] (3) The obtained precursor solution was coated on Li 6.4 La3Zr 1.4 Ta 0.6 O 12 The surface loading of the ceramic disc in contact with the two electrodes is 12.5 μL / cm. 2 Then let it stand for 12 hours, allowing the conductive particles to settle naturally due to gravity.

[0069] (4) The solid electrolyte after step (3) is heated at 50°C for 12 hours to obtain the interface modification layer.

[0070] A solid-state lithium battery, the preparation method includes the following steps:

[0071] The precursor solution prepared in step (1) is coated onto the surface of the ceramic disc obtained in step (2) that is in contact with the two electrodes, with an areal loading of 12.5 μL / cm². 2 The order from bottom to top is: negative electrode shell - lithium metal foil - 12μL precursor solution - Li 6.4 La3Zr 1.4 Ta 0.6 O 12 Ceramic sheet - 12μL precursor solution - LiNi 0.5 Co 0.2 Mn 0.3 The O2 electrode sheet, nickel foam, and positive electrode shell are assembled sequentially into a 2025-type coin cell, and then left to stand for 12 hours to allow the conductive particles to settle naturally due to gravity. After standing, it is heated at 50°C for 12 hours to obtain a solid-state lithium battery modified with an interface modification layer based on in-situ polymerization. The lithium foil is a 0.8 cm diameter disc, and the LiNi... 0.5 Co 0.2 Mn 0.3 The O2 electrode is a circular piece with a diameter of 0.8 cm.

[0072] Battery performance evaluation:

[0073] Electrochemical impedance spectroscopy (EIS) was performed on the assembled solid-state lithium battery at 25°C. The results are shown in the attached figure. Figure 6 As shown, the total impedance of the entire battery is 750Ω. A constant current charge-discharge test was performed on the battery at 25℃, with a charge-discharge cutoff voltage of 2.7-4.3V. The results are attached. Figure 7 As shown, after 100 cycles at 0.1C, the battery retains 86% of its discharge specific capacity and has a coulombic efficiency greater than 99%.

[0074] Example 3

[0075] A method for preparing an interface modification layer for solid-state lithium batteries includes the following steps:

[0076] (1) Carbonate-based liquid electrolyte, ethyl methacrylate, trimethylolpropane triacrylate, azobisisobutyronitrile and Li 6.4 La3Zr 1.4 Ta 0.6 O 12 Lithium-ion conductive particles were mixed in a mass ratio of 90:5:1:0.1:1 to obtain a precursor solution;

[0077] The carbonate-based liquid electrolyte is a 1 mol / L solution formed by dissolving lithium tetrafluoroborate in ethylene carbonate EC, diethyl carbonate DEC and dimethyl carbonate DMC in a volume ratio of 1:1:1.

[0078] The mass concentration of ethyl methacrylate is 99.0%; the mass concentration of trimethylolpropane triacrylate is 99.0%; the mass concentration of azobisisobutyronitrile is 98.0%; Li 6.4 La3Zr 1.4 Ta 0.6 O 12 The solid particles of lithium-ion conductive particles have a particle size of 400 nm.

[0079] (2) Garnet-type solid electrolyte Li was prepared by solid-state sintering. 6.4 La3Zr 1.4 Ta 0.6 O 12 Ceramic sheet, the ceramic sheet is a round piece with a thickness of 2mm and a diameter of 0.8cm;

[0080] (3) The obtained precursor solution was coated on Li 6.4 La3Zr 1.4 Ta 0.6 O 12 The surface loading of the ceramic disc in contact with the two electrodes is 15 μL / cm. 2 Then let it stand for 10 hours, allowing the conductive particles to settle naturally due to gravity.

[0081] (4) The solid electrolyte after step (3) is heated at 70°C for 8 hours to obtain the interface modification layer.

[0082] A solid-state lithium battery, the preparation method includes the following steps:

[0083] The precursor solution prepared in step (1) is coated onto the surface of the ceramic disc obtained in step (2) that is in contact with the two electrodes, with a surface loading of 15 μL / cm².2 The order from bottom to top is: negative electrode shell - lithium metal foil - 8μL precursor solution - Li 6.4 La3Zr 1.4 Ta 0.6 O 12 A 2025-type coin cell was assembled in the following order: ceramic sheet - 8 μL precursor solution - LiFePO4 electrode sheet - nickel foam - positive electrode shell. The cells were then left to stand for 10 hours to allow the conductive particles to settle naturally due to gravity. After standing, the cells were heated at 70°C for 8 hours to obtain a solid-state lithium battery modified with an interface modification layer based on in-situ polymerization. The lithium foil and the LiFePO4 electrode sheet were both 0.8 cm in diameter.

[0084] Battery performance evaluation:

[0085] Electrochemical impedance spectroscopy (EIS) was performed on the assembled solid-state lithium battery at 25°C. The results are shown in the attached figure. Figure 8 As shown, the total impedance of the entire battery is 575Ω. A constant current charge-discharge test was performed on the battery at 25℃, with a charge-discharge cutoff voltage of 2.5-4.0V. The results are attached. Figure 9 As shown, after 50 cycles at 0.2C, the battery retains 98% of its discharge specific capacity and has a coulombic efficiency greater than 99%.

[0086] Example 4

[0087] A method for preparing an interface modification layer for solid-state lithium batteries includes the following steps:

[0088] (1) A carbonate-based liquid electrolyte, butyl methacrylate, trimethylolpropane trimethacrylate, 4,4'-azobis(4-cyanopentanoic acid) and Li 6.4 La3Zr 1.4 Ta 0.6 O 12 Lithium-ion conductive particles were mixed in a mass ratio of 100:12:4:0.5:30 to obtain a precursor solution;

[0089] The carbonate-based liquid electrolyte is a 1 mol / L solution formed by dissolving lithium perchlorate in ethylene carbonate EC, diethyl carbonate DEC and dimethyl carbonate DMC in a volume ratio of 1:1:1.

[0090] The butyl methacrylate has a mass concentration of 99.0%; the trimethylolpropane trimethacrylate has a mass concentration of 98.0%; the 4,4'-azobis(4-cyanopentanoic acid) has a mass concentration of 98.5%; Li 6.4 La3Zr 1.4 Ta 0.6 O 12The solid particles of lithium-ion conductive particles have a particle size of 400 nm.

[0091] (2) Garnet-type solid electrolyte Li was prepared by solid-state sintering. 6.4 La3Zr 1.4 Ta 0.6 O 12 Ceramic sheet, the ceramic sheet is a round piece with a thickness of 1.5mm and a diameter of 1.2cm;

[0092] (3) The obtained precursor solution was coated on Li 6.4 La3Zr 1.4 Ta 0.6 O 12 The surface loading of the ceramic disc in contact with the two electrodes is 7 μL / cm. 2 Then let it stand for 9 hours, allowing the conductive particles to settle naturally due to gravity.

[0093] (4) The solid electrolyte after step (3) is heated at 80°C for 10 hours to obtain the interface modification layer.

[0094] A solid-state lithium battery, the preparation method includes the following steps:

[0095] The precursor solution prepared in step (1) is coated onto the surface of the ceramic disc obtained in step (2) that is in contact with the two electrodes, with a surface loading of 7 μL / cm². 2 The order from bottom to top is: negative electrode shell - lithium metal foil - 8μL precursor solution - Li 6.4 La3Zr 1.4 Ta 0.6 O 12 A 2025-type coin cell was assembled in the following order: ceramic sheet - 8 μL precursor solution - LiFePO4 electrode sheet - nickel foam - positive electrode shell. The cell was then left to stand for 9 hours to allow the conductive particles to settle naturally due to gravity. After standing, the cell was heated at 80°C for 10 hours to obtain a solid-state lithium battery modified with an interface modification layer based on in-situ polymerization. The lithium foil and the LiFePO4 electrode sheet are both 0.8 cm in diameter.

[0096] Battery performance evaluation:

[0097] Electrochemical impedance spectroscopy (EIS) was performed on the assembled solid-state lithium battery at 25°C. The results are shown in the attached figure. Figure 10 As shown, the total impedance of the entire battery is 500Ω; constant current charge-discharge tests were performed on the battery at 25℃, and the charge-discharge cutoff voltage was 2.5-4.0V. The results are attached. Figure 11 As shown, after 50 cycles at 0.2C, the battery retains 97% of its discharge specific capacity and has a coulombic efficiency greater than 99%.

[0098] Example 5

[0099] A method for preparing an interface modification layer for solid-state lithium batteries includes the following steps:

[0100] (1) A carbonate-based liquid electrolyte, benzoyl methacrylate, ethylene glycol diacrylate, 2,2'-azobis(4-methoxy-2,4-dimethylpentanonitrile) and Li 1.5 Al 0.5 Ge 1.5 (PO4)3 lithium-ion conductive particles were mixed in a mass ratio of 90:8:2:0.2:60 to obtain a precursor solution;

[0101] The carbonate-based liquid electrolyte is a 1 mol / L solution formed by dissolving lithium bis(oxalato)borate in ethylene carbonate EC, diethyl carbonate DEC, and dimethyl carbonate DMC in a volume ratio of 1:1:1.

[0102] The mass concentration of benzyl methacrylate is 98.0%; the mass concentration of ethylene glycol diacrylate is 99.0%; the mass concentration of 2,2'-azobis(4-methoxy-2,4-dimethylpentanonitrile) is 98.0%; Li 1.5 Al 0.5 Ge 1.5 The solid particle size of (PO4)3 lithium-ion conductive particles is 600 nm.

[0103] (2) Preparation of NASICON-type solid electrolyte Li using solid-state sintering 1.5 Al 0.5 Ge 1.5 (PO4)3 ceramic sheet, the ceramic sheet is a round sheet with a thickness of 1.8mm and a diameter of 0.9cm;

[0104] (3) The obtained precursor solution was coated on Li 1.5 Al 0.5 Ge 1.5 The surface loading of the (PO4)3 ceramic disc in contact with the two electrodes is 6 μL / cm². 2 Then it was left to stand for 11 hours, allowing the conductive particles to settle naturally due to gravity.

[0105] (4) The solid electrolyte after step (3) is heated at 90°C for 9 hours to obtain the interface modification layer.

[0106] A solid-state lithium battery, the preparation method includes the following steps:

[0107] The precursor solution prepared in step (1) is coated onto the surface of the ceramic disc obtained in step (2) that is in contact with the two electrodes, with a surface loading of 6 μL / cm. 2 The order from bottom to top is: negative electrode shell - lithium-indium alloy foil - 4μL precursor solution - Li 1.5 Al 0.5 Ge 1.5 A 2025-type coin cell was assembled in the following order: (PO4)3 ceramic sheet - 4 μL precursor solution - LiFePO4 electrode sheet - nickel foam - positive electrode shell. The battery was then left to stand for 11 hours to allow the conductive particles to settle naturally due to gravity. After standing, the battery was heated at 90°C for 9 hours to obtain a solid-state lithium battery modified with an interface modification layer based on in-situ polymerization. The lithium indium alloy foil and the LiFePO4 electrode sheet are both 0.8 cm in diameter.

[0108] Battery performance evaluation:

[0109] Electrochemical impedance spectroscopy (EIS) was performed on the assembled solid-state lithium battery at 25°C. The results are shown in the attached figure. Figure 12 As shown, the total impedance of the entire battery is 600Ω; constant current charge-discharge tests were performed on the battery at 25℃, and the charge-discharge cutoff voltage was 2.5-4.0V. The results are attached. Figure 13 As shown, after 50 cycles at 0.2C, the battery retains 95% of its discharge specific capacity and has a coulombic efficiency greater than 99%. The batteries assembled in Examples 3-5 all exhibit low total impedance and good cycle performance, highlighting the compositional diversity of the interface modification layer for solid-state lithium batteries in this invention.

[0110] Example 6

[0111] Garnet-type solid electrolyte Li was prepared by solid-state sintering. 6.4 La3Zr 1.4 Ta 0.6 O 12 Ceramic sheet, the ceramic sheet is a round piece with a thickness of 1.0mm and a diameter of 1.0cm;

[0112] A solid-state lithium battery, the preparation method includes the following steps:

[0113] From bottom to top, the order is: negative electrode shell - lithium metal foil - Li. 6.4 La3Zr 1.4 Ta 0.6 O 12 A 2025-type coin cell is assembled in the following order: ceramic sheet - LiFePO4 electrode sheet - nickel foam - positive electrode shell; wherein the lithium foil is a circular sheet with a diameter of 0.8 cm and the LiFePO4 electrode sheet is a circular sheet with a diameter of 0.8 cm.

[0114] Battery performance evaluation:

[0115] Electrochemical impedance spectroscopy (EIS) was performed on the assembled solid-state lithium battery at 25°C. The total impedance of the entire battery was enormous, reaching the megaohm level. Due to the excessive impedance, the battery could not undergo normal charge-discharge cycles. In Example 6, no treatment was performed on the solid electrolyte and electrode interfaces, resulting in a battery with extremely high interface resistance. This was intended to highlight the reduced impedance achieved by the modified impedance obtained in the previous examples.

[0116] Example 7

[0117] A method for preparing an interface modification layer for solid-state lithium batteries includes the following steps:

[0118] (1) A precursor solution was obtained by mixing carbonate-based liquid electrolyte, methyl methacrylate, ethylene glycol dimethacrylate and azobisisobutyronitrile in a mass ratio of 100:10:3:0.3.

[0119] The carbonate-based liquid electrolyte is a 1 mol / L solution formed by dissolving lithium hexafluorophosphate in ethylene carbonate EC, diethyl carbonate DEC and dimethyl carbonate DMC in a volume ratio of 1:1:1.

[0120] The methyl methacrylate has a mass concentration of 99.0%; the ethylene glycol dimethacrylate has a mass concentration of 98.0%; and the azobisisobutyronitrile has a mass concentration of 99.0%.

[0121] (2) Garnet-type solid electrolyte Li was prepared by solid-state sintering. 6.4 La3Zr 1.4 Ta 0.6 O 12 Ceramic sheet, the ceramic sheet is a round piece with a thickness of 1.3mm and a diameter of 1.0cm;

[0122] (3) The obtained precursor solution was coated on Li 6.4 La3Zr 1.4 Ta 0.6 O 12 The surface loading of the ceramic disc in contact with the two electrodes is 13 μL / cm. 2 Then let it stand for 8 hours, allowing the conductive particles to settle naturally due to gravity.

[0123] (4) The ceramic disc processed in step (3) is heated at 60°C for 6 hours to obtain an interface modification layer.

[0124] A solid-state lithium battery, the preparation method includes the following steps:

[0125] The precursor solution prepared in step (1) is coated onto the surface of the ceramic disc obtained in step (2) that is in contact with the two electrodes, with a surface loading of 13 μL / cm². 2 The order from bottom to top is: negative electrode shell - lithium metal foil - 10 μL precursor solution - Li 6.4 La3Zr 1.4 Ta 0.6 O 12 A 2025-type coin cell was assembled in the following order: ceramic sheet - 10 μL precursor solution - LiFePO4 electrode sheet - nickel foam - positive electrode shell. The cells were then left to stand for 8 hours to allow the conductive particles to settle naturally under gravity. After standing, the cells were heated at 60°C for 6 hours to obtain a solid-state lithium battery modified with an interface modification layer based on in-situ polymerization. The lithium foil and the LiFePO4 electrode sheet were both 0.8 cm in diameter.

[0126] Battery performance evaluation:

[0127] Electrochemical impedance spectroscopy (EIS) was performed on the assembled solid-state lithium battery at 25°C. The results are shown in the attached figure. Figure 14 As shown, the total impedance of the entire battery is 1625Ω. A constant current charge-discharge test was performed on the battery at 25℃, with a charge-discharge cutoff voltage of 2.5-4.0V. The results are attached. Figure 15 As shown, after 100 cycles at 0.2C, the battery's discharge specific capacity is only 13.1 mAh / g.

[0128] Example 8

[0129] A method for preparing an interface modification layer for solid-state lithium batteries includes the following steps:

[0130] (1) Mix carbonate-based liquid electrolyte, methyl methacrylate, ethylene glycol dimethacrylate and azobisisobutyronitrile in a mass ratio of 100:15:5:1 to obtain a precursor solution;

[0131] The carbonate-based liquid electrolyte is a 1 mol / L solution formed by dissolving lithium hexafluorophosphate in ethylene carbonate EC, diethyl carbonate DEC and dimethyl carbonate DMC in a volume ratio of 1:1:1.

[0132] The methyl methacrylate has a mass concentration of 99.0%; the ethylene glycol dimethacrylate has a mass concentration of 98.0%; the azobisisobutyronitrile (AIBN) has a mass concentration of 99.0%; and Li 6.4 La3Zr 1.4 Ta 0.6 O 12 The solid particles of lithium-ion conductive particles have a particle size of 500 nm.

[0133] (2) Garnet-type solid electrolyte Li was prepared by solid-state sintering. 6.4 La3Zr 1.4 Ta 0.6 O 12 Ceramic sheet, the ceramic sheet is a round piece with a thickness of 1.2mm and a diameter of 1.1cm;

[0134] (3) The obtained precursor solution was coated on Li 6.4 La3Zr 1.4 Ta 0.6 O 12 The surface loading of the ceramic disc in contact with the two electrodes is 12.5 μL / cm. 2 Then let it stand for 12 hours, allowing the conductive particles to settle naturally due to gravity.

[0135] (4) The solid electrolyte after step (3) is heated at 50°C for 12 hours to obtain the interface modification layer.

[0136] A solid-state lithium battery, the preparation method includes the following steps:

[0137] The precursor solution prepared in step (1) is coated onto the surface of the ceramic disc obtained in step (2) that is in contact with the two electrodes, with an areal loading of 12.5 μL / cm². 2 The order from bottom to top is: negative electrode shell - lithium metal foil - 12μL precursor solution - Li 6.4 La3Zr 1.4 Ta 0.6 O 12 Ceramic sheet - 12μL precursor solution - LiNi 0.5 Co 0.2 Mn 0.3 The O2 electrode sheet, nickel foam, and positive electrode shell are assembled sequentially into a 2025-type coin cell, and then left to stand for 12 hours to allow the conductive particles to settle naturally due to gravity. After standing, it is heated at 50°C for 12 hours to obtain a solid-state lithium battery modified with an interface modification layer based on in-situ polymerization. The lithium foil is a 0.8 cm diameter disc, and the LiNi... 0.5 Co 0.2 Mn 0.3 The O2 electrode is a circular piece with a diameter of 0.8 cm.

[0138] Battery performance evaluation:

[0139] Electrochemical impedance spectroscopy (EIS) was performed on the assembled solid-state lithium battery at 25°C. The results are shown in the attached figure. Figure 16 As shown, the total impedance of the entire battery is 5000Ω. A constant current charge-discharge test was performed on the battery at 25℃, with a charge-discharge cutoff voltage of 2.7-4.3V. The results are attached. Figure 17As shown, after 100 cycles at 0.1C, the battery's discharge specific capacity is only 7.3 mAh / g.

[0140] In Examples 7 and 8, the interface modification layer described above was not formed at the solid electrolyte / electrode interface, and the assembled batteries had high total impedance and poor cycle performance. The purpose is to highlight that the modified impedance obtained in the above examples of the present invention has indeed achieved a reduction and the cycle performance has indeed been improved.

[0141] Example 9

[0142] A method for preparing an interface modification layer for solid-state lithium batteries includes the following steps:

[0143] (1) Carbonate-based liquid electrolyte, methyl methacrylate, ethylene glycol dimethacrylate, azobisisobutyronitrile and Li 6.4 La3Zr 1.4 Ta 0.6 O 12 Lithium-ion conductive particles were mixed in a mass ratio of 100:10:3:0.3:50 to obtain a precursor solution;

[0144] The carbonate-based liquid electrolyte is a 1 mol / L solution formed by dissolving lithium hexafluorophosphate in ethylene carbonate EC, diethyl carbonate DEC and dimethyl carbonate DMC in a volume ratio of 1:1:1.

[0145] The methyl methacrylate has a mass concentration of 99.0%; the ethylene glycol dimethacrylate has a mass concentration of 98.0%; the azobisisobutyronitrile (AIBN) has a mass concentration of 99.0%; and Li 6.4 La3Zr 1.4 Ta 0.6 O 12 The solid particles of lithium-ion conductive particles have a particle size of 500 nm.

[0146] (2) Garnet-type solid electrolyte Li was prepared by solid-state sintering. 6.4 La3Zr 1.4 Ta 0.6 O 12 Ceramic sheet, the ceramic sheet is a round piece with a thickness of 1.0mm and a diameter of 1.0cm;

[0147] (3) The obtained precursor solution was coated on Li 6.4 La3Zr 1.4 Ta 0.6 O 12 The surface loading of the ceramic disc in contact with the two electrodes is 13 μL / cm. 2 Then let it stand for 8 hours, allowing the conductive particles to settle naturally due to gravity.

[0148] (4) The ceramic disc processed in step (3) is heated at 60°C for 6 hours to obtain the interface modification layer.

[0149] Based on the aforementioned interface modification layer, a solid-state lithium battery is provided, comprising a positive electrode shell, a negative electrode shell, a LiFePO4 electrode sheet, lithium metal foil, nickel foam, and Li 6.4 La3Zr 1.4 Ta 0.6 O 12 The ceramic sheet and the aforementioned interface modification layer constitute a structure in Li 6.4 La3Zr 1.4 Ta 0.6 O 12 An interface modification layer is set between the ceramic sheet, the LiFePO4 electrode sheet, and the lithium metal foil. The rigid side contacts the lithium metal foil of the lithium battery, and the flexible side contacts the LiFePO4 electrode sheet of the lithium battery. The assembly sequence from bottom to top is: negative electrode shell - lithium metal foil - interface modification layer - Li 6.4 La3Zr 1.4 Ta 0.6 O 12 Ceramic sheet - interface modification layer - LiFePO4 electrode sheet - nickel foam - positive electrode shell.

[0150] Example 10

[0151] A method for preparing an interface modification layer for solid-state lithium batteries includes the following steps:

[0152] (1) Carbonate-based liquid electrolyte, ethyl methacrylate, trimethylolpropane triacrylate, azobisisobutyronitrile and Li 6.4 La3Zr 1.4 Ta 0.6 O 12 Lithium-ion conductive particles were mixed in a mass ratio of 90:5:1:0.1:1 to obtain a precursor solution;

[0153] The carbonate-based liquid electrolyte is a 1 mol / L solution formed by dissolving lithium tetrafluoroborate in ethylene carbonate EC, diethyl carbonate DEC and dimethyl carbonate DMC in a volume ratio of 1:1:1.

[0154] The mass concentration of ethyl methacrylate is 99.0%; the mass concentration of trimethylolpropane triacrylate is 99.0%; the mass concentration of azobisisobutyronitrile is 98.0%; Li 6.4 La3Zr 1.4 Ta 0.6 O 12 The solid particles of lithium-ion conductive particles have a particle size of 400 nm.

[0155] (2) Garnet-type solid electrolyte Li was prepared by solid-state sintering. 6.4 La3Zr 1.4 Ta 0.6 O 12 Ceramic sheet, the ceramic sheet is a round piece with a thickness of 1.5mm and a diameter of 0.8cm;

[0156] (3) The obtained precursor solution was coated on Li 6.4 La3Zr 1.4 Ta 0.6 O 12 The surface loading of the ceramic disc in contact with the two electrodes is 15 μL / cm. 2 Then let it stand for 10 hours, allowing the conductive particles to settle naturally due to gravity.

[0157] (4) The ceramic disc processed in step (3) is heated at 70°C for 8 hours to obtain the interface modification layer.

[0158] Based on the aforementioned interface modification layer, a solid-state lithium battery is provided, comprising a positive electrode shell, a negative electrode shell, and a LiNi alloy. 0.5 Co 0.2 Mn 0.3 O2 electrode sheet, lithium metal foil, nickel foam, Li 6.4 La3Zr 1.4 Ta 0.6 O 12 The ceramic sheet and the aforementioned interface modification layer constitute a structure in Li 6.4 La3Zr 1.4 Ta 0.6 O 12 Ceramic sheets and LiNi 0.5 Co 0.2 Mn 0.3 An interface modification layer is disposed between the O2 electrode sheet and the lithium metal foil, with the rigid side in contact with the lithium metal foil of the lithium battery and the flexible side in contact with the LiNi alloy of the lithium battery. 0.5 Co 0.2 Mn 0.3 O2 electrode contact, assembly sequence from bottom to top: negative electrode shell - lithium metal foil - interface modification layer - Li 6.4 La3Zr 1.4 Ta 0.6 O 12 Ceramic sheet - interface modification layer - LiNi 0.5 Co 0.2 Mn 0.3 O2 electrode sheet - nickel foam - positive electrode shell.

[0159] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for preparing an interface modification layer for solid-state lithium batteries, characterized in that, The battery consists of a positive electrode shell, a negative electrode shell, a positive electrode sheet, a negative electrode sheet, nickel foam, a solid electrolyte, and an interface modification layer. An interface modification layer is provided between the solid electrolyte and the positive and negative electrode sheets. The interface modification layer includes a rigid side and a flexible side. The rigid side is enriched with lithium-ion conductive particles and contacts the negative electrode of the lithium battery. The flexible side is enriched with organic matrix and contacts the positive electrode of the lithium battery. The assembly sequence from bottom to top is as follows: negative electrode shell - negative electrode sheet - interface modification layer - solid electrolyte - interface modification layer - positive electrode sheet - nickel foam - positive electrode shell. The method for preparing the interface modification layer includes the following steps: (1) A precursor solution is obtained by mixing carbonate-based liquid electrolyte, organic polymer monomer, crosslinking agent, initiator and lithium-ion conductive particles in a certain proportion; (2) The obtained precursor solution is coated on the surface of the solid electrolyte in contact with the two electrodes, and then left to stand, so that the conductive particles settle naturally due to gravity. (3) Heat the solid electrolyte after step (2) to obtain the interface modification layer.

2. The method for preparing an interface modification layer for solid-state lithium batteries according to claim 1, characterized in that, In step (1): the electrolyte component in the carbonate-based liquid electrolyte is selected from any one of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethanesulfonyl)imide, and lithium bis(oxalateborate). The organic polymer monomer is selected from any one of methyl methacrylate, ethyl methacrylate, isopropyl methacrylate, butyl methacrylate, and paraben methacrylate; The crosslinking agent is selected from any one of ethylene glycol dimethacrylate, trimethylolpropane triacrylate, trimethylolpropane trimethacrylate, and ethylene glycol dimethacrylate. The initiator is selected from any one of azobisisobutyronitrile, azobisisoheptanenitrile, 4,4'-azobis(4-cyanopentanoic acid) and 2,2'-azobis(4-methoxy-2,4-dimethylpentanonitrile); The lithium-ion conductive particles are selected from any one of garnet-type solid electrolytes, NASICON-type solid electrolytes, and perovskite-type solid electrolytes.

3. The method for preparing an interface modification layer for solid-state lithium batteries according to claim 1, characterized in that, In step (1), the mass ratio of the carbonate-based liquid electrolyte, organic polymer monomer, crosslinking agent, initiator and lithium-ion conductive particles is (90-100): (5-15): (1-5): (0.1-1): (1-100).

4. The method for preparing an interface modification layer for solid-state lithium batteries according to claim 1, characterized in that, In step (1), the electrolyte components in the carbonate-based liquid electrolyte are dissolved in ethylene carbonate EC, diethyl carbonate DEC and dimethyl carbonate DMC in a volume ratio of 1:1:1 to form a solution with a concentration of 1 mol / L, thereby obtaining the carbonate-based liquid electrolyte. The organic polymer monomer has a mass concentration of 98.0%-99.9%; the crosslinking agent has a mass concentration of 98.0%-99.9%; the initiator has a mass concentration of 98.0%-99.9%; and the lithium-ion conductive particles have a particle size of 400-600 nm.

5. The method for preparing an interface modification layer for solid-state lithium batteries according to claim 1, characterized in that, In step (2), the solid electrolyte is a round sheet with a thickness of 1-2 mm and a diameter of 8-12 mm, and is selected from any one of a garnet-type solid electrolyte, a NASICON-type solid electrolyte, and a perovskite-type solid electrolyte; the surface loading of the precursor solution is 5-15 μL / cm 2 , and the standing time is 6-12 h; in step (3), the heating treatment parameters include a heating temperature of 50-100 ℃ and a heating time of 1-12 h.

6. An interface modification layer for solid-state lithium batteries obtained by the preparation method according to claim 1, characterized in that, The average Young's modulus of the rigid side is 10-15 GPa, and the average Young's modulus of the flexible side is 0.1-5 GPa.

7. A solid-state lithium battery, characterized in that, The battery is prepared by: preparing an interface modification layer using the preparation method described in claim 1; coating the precursor solution prepared in step (1) onto the surface of the solid electrolyte in contact with the two electrodes; assembling the battery in the following order from bottom to top: negative electrode shell - negative electrode sheet - precursor solution - solid electrolyte - precursor solution - positive electrode sheet - nickel foam - positive electrode shell; and then heating the battery after standing to obtain a solid lithium battery modified with the interface modification layer.

8. A solid-state lithium battery according to claim 7, characterized in that, The positive electrode is one of oxides, sulfur and its complexes, sulfides and fluorides; the negative electrode is one of lithium metal, lithium alloy, graphite, silicon and silicon-carbon; the solid electrolyte is one of garnet-type solid electrolyte, NASICON-type solid electrolyte, and perovskite-type solid electrolyte.

9. The method for preparing a solid-state lithium battery according to claim 7, characterized in that, The settling time is 6-12 hours; the parameters of the heating treatment include: heating temperature of 50-100℃ and heating time of 1-12 hours.

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