Negative electrode interface modification material and battery using the same

Abstract

To provide a negative electrode interface modifying material for a battery.SOLUTION: The negative electrode interface modification material comprises succinonitrile, a polymer, a lithium salt, and an additive. A lithium ion solid-state battery comprising the negative electrode interface modification material is further provided.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention provides a negative electrode interface modifier material for a battery, particularly a negative electrode interface modifier material comprising succinonitrile, a polymer, a lithium salt, and an additive. [Background technology]

[0002] In response to global warming and climate change, energy conservation and carbon reduction have become major goals at present. Increasing energy storage efficiency is a key challenge in energy conservation. Lithium-ion batteries are one of the most widely used energy storage systems. However, conventional lithium-ion batteries use liquid electrolytes, which pose safety issues due to their flammability. Therefore, recent research on lithium-ion batteries has focused on flame-retardant inorganic solid electrolytes, and lithium-aluminum-germanium-phosphate-based electrolytes are particularly promising.

[0003] A specific example of a lithium aluminum germanium phosphate electrolyte is Li 1.5 Al 0.5 Ge 1.5 The (PO4)3 (LAGP) electrolyte has the advantage of being stable in air and has a -4 It has an ionic conductivity of 1000 S / cm. However, there is a potential mismatch between the LAGP electrolyte and lithium metal (commonly used as an electrode material in lithium-ion batteries), which leads to an unstable relationship between LAGP and lithium (Li). The germanium ions (Ge 4+ ) is converted by lithium to the lower valence ion Ge 2+ and Ge, which hinders the migration of lithium ions. This problem limits the application of LAGP electrolytes to lithium-ion batteries. By forming an amorphous germanium (Ge) thin film on the surface of LAGP, germanium ions (Ge 4+It is known that the reduction reaction of lithium (Li) with amorphous germanium (Ge) can be suppressed, creating a close contact between the lithium metal and the LAGP electrolyte, thereby reducing the interfacial impedance. However, the ionic conductivity of the LAGP electrolyte using amorphous germanium (Ge) thin film is low, which limits the voltage of the cathode material.

[0004] In addition, succinonitrile-based plastic crystal electrolytes (PCEs) have a melting point of approximately 10 -3 The ionic conductivity can reach 1000 S / cm, providing a wide potential window. However, the use of succinonitrile-based electrolytes can lead to poor mechanical performance and can also deteriorate the cycling stability of batteries due to lithium metal catalyzing the side reaction of nitrile polymerization. Summary of the Invention

[0005] In consideration of the above-mentioned technical problems, the present invention provides an anode interface modification material that can address the contact and side reaction issues between lithium metal and a lithium-aluminum-germanium-phosphate-based electrolyte. This modification material aims to provide a lithium-ion battery with high chemical stability, low impedance, high electrochemical stability, and excellent cycling stability. Furthermore, the resulting lithium-ion battery can have good mechanical performance while maintaining high ionic conductivity.

[0006] Therefore, an object of the present invention is to provide a negative electrode interface modifying material comprising sucrinonitrile, a polymer, a lithium salt, and an additive.

[0007] In one embodiment of the present invention, the polymer is selected from the group consisting of poly(ethylene oxide) (PEO), polyacrylonitrile (PAN), poly(vinylidene fluoride) (PVDF), poly(propylene carbonate) (PPC), poly(methyl methacrylate) (PMMA), and combinations thereof.

[0008] In one embodiment of the invention, the polymer has a weight average molecular weight ranging from 20,000 to 4,000,000.

[0009] In one embodiment of the present invention, the lithium salt is selected from the group consisting of lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), LiPF6, LiBF4, LiClO4, LiAsF6, LiCF3SO3, and combinations thereof.

[0010] In one embodiment of the present invention, the additive is selected from the group consisting of fluoroethylene carbonate (FEC), ethylene carbonate (EC), vinylene carbonate (VC), and combinations thereof.

[0011] In one embodiment of the present invention, the amount of the polymer based on the total weight of the sucrinenitrile, the polymer, the lithium salt, and the additive is in the range of greater than 0 wt % to 20 wt %, and the amount of the additive is in the range of greater than 0 wt % to 15 wt %.

[0012] In one embodiment of the invention, the amount of the lithium salt, based on the total weight of the succinonitrile, the polymer, the lithium salt, and the additive, ranges from 5 wt % to 15 wt %, and the amount of the succinonitrile ranges from 60 wt % to 90 wt %.

[0013] Another object of the present invention is to provide a lithium ion solid state battery including a positive electrode, a negative electrode, a solid electrolyte, and the aforementioned negative electrode interface modifier, wherein the negative electrode interface modifier is disposed between the negative electrode and the solid electrolyte.

[0014] In one embodiment of the present invention, the negative electrode is made of a material selected from the group consisting of lithium metal, lithium-indium alloy, lithium-aluminum alloy, silicon-lithium alloy, and combinations thereof.

[0015] In one embodiment of the present invention, the solid electrolyte is a lithium aluminum germanium phosphate-based electrolyte. 1.5 Al 0.5 Ge 1.5 It may have the general formula (PO4)3(LAGP).

[0016] In one embodiment of the present invention, the positive electrode is made of a material selected from the group consisting of lithium iron phosphate (LiFePO4, LFP), lithium cobalt oxide (LiCoO2, LCO), lithium nickel cobalt aluminum oxide (NCA), and lithium nickel cobalt manganese oxide (NCM).

[0017] In one embodiment of the present invention, the positive electrode of a lithium ion solid state battery has an interfacial layer formed from an ionic liquid.

[0018] To more clearly express the above objectives, technical features and advantages of the present invention, the present invention will be described in detail with reference to several embodiments below. [Brief explanation of the drawings]

[0019] [Figure 1] FIG. 1 is a schematic diagram of the structure of a lithium ion solid state battery of the present invention. [Figure 2] FIG. 2 is a curve showing the ionic conductivity of the negative electrode interface modifier material at room temperature. [Figure 3] FIG. 3 is a voltage-time curve diagram for a symmetric cell. [Figure 4] FIG. 4 shows the results of an impedance analysis of a symmetric cell. [Figure 5] FIG. 5 is a voltage-time curve diagram for a symmetric cell. [Figure 6] FIG. 6 is a diagram showing the charge-discharge curve of the lithium ion solid state battery of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0020] DETAILED DESCRIPTION OF THE INVENTION Several embodiments of the present invention will be described in detail below. However, the present invention may be embodied in various different embodiments and should not be limited to the embodiments set forth herein.

[0021] In the accompanying drawings, like elements are represented by like reference numerals, and for clarity, layers and regions may not be drawn to scale.

[0022] Unless otherwise stated, the terms "a," "the," "the," and the like used in the specification and claims are intended to include both the singular and the plural.

[0023] Unless otherwise stated, in this specification and claims, the term "positive electrode" refers to the cathode in a battery during discharging, and the term "negative electrode" refers to the anode in a battery during discharging.

[0024] Unless otherwise stated, in this specification and claims, the term "ionic liquid" refers to an ionic compound in a liquid state, particularly an ionic compound that enhances the mobility of lithium ions and has the properties of a soluble lithium salt.

[0025] Unless otherwise stated, in this specification and claims, the units of weight average molecular weight (Mw) are "Daltons."

[0026] The advantages of the present invention over the prior art lie in the combination of a polymer, an additive, and a lithium salt in a succinonitrile-based plastic crystalline electrolyte, thereby providing an anode interface modification material that can address the contact and side reaction issues between the lithium aluminum germanium phosphate-based electrolyte and lithium metal. This enables the provision of a lithium-ion battery with high chemical stability, low impedance, high electrochemical stability, and excellent cycling stability. Furthermore, the resulting lithium-ion battery can have good mechanical performance while maintaining high ionic conductivity.

[0027] 1.Negative electrode interface modification material

[0028] The negative electrode interface modifier material of the present invention comprises succinonitrile, a polymer, a lithium salt, and an additive. In one embodiment of the present invention, the negative electrode interface modifier material of the present invention consists essentially of succinonitrile, a polymer, a lithium salt, and an additive, or consists essentially of succinonitrile, a polymer, a lithium salt, and an additive.

[0029] [Succinonitrile]

[0030] Succinonitrile can form plastic crystals at room temperature. These plastic crystals are interlayers formed by quasi-spherical or discotic molecules that exhibit long-range translational order while exhibiting rotational and / or orientational disorder. This results in high diffusivity and plasticity, making them suitable for use as a substrate for electrolytes. In addition, succinonitrile can effectively promote the dissolution of lithium salts and increase ionic conductivity.

[0031] In the negative electrode interface modifier material of the present invention, the amount of scurinonitrile based on the total weight of the scurinonitrile, polymer, lithium salt, and additives is preferably in the range of 60 to 90% by weight. For example, the amount of scurinonitrile based on the total weight of the scurinonitrile, polymer, lithium salt, and additives may be any of 60%, 61%, 62%, 63%, 64%, 65%, 66%, 67%, 68%, 69%, 70%, 71%, 72%, 73%, 74%, 75%, 76%, 77%, 78%, 79%, 80%, 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90% by weight, or any range between any two of the aforementioned values. When the amount of sucrinonitrile falls within the specified range, the negative electrode interface modifier material of the present invention can effectively improve the mechanical properties of a lithium ion battery while maintaining good ionic conductivity of the battery.

[0032] [polymer]

[0033] In the negative electrode interface modifier material of the present invention, a polymer is used to improve mechanical performance, thereby increasing the cycling stability of the battery. Examples of polymers include, but are not limited to, PEO, PAN, PVDF, PPC, and PMMA. The aforementioned polymers can be used individually or in any combination. Considering the compatibility of the negative electrode interface modifier material with other materials and the suitability of the composition of lithium-ion batteries, the polymer is preferably PEO.

[0034] In the negative electrode interface modifier material of the present invention, the weight average molecular weight of the polymer can be in the range of 20,000 to 4,000,000. For example, the weight average molecular weight of the polymer can be any of 20,000, 30,000, 40,000, 50,000, 60,000, 70,000, 80,000, 90,000, 100,000, 200,000, 300,000, 400,000, 500,000, 600,000, 700,000, 800,000, 900,000, 1,000,000, 1,500,000, 2,000,000, 2,500,000, 3,000,000, 3,500,000, and 4,000,000, or within a range between any two of the aforementioned values.

[0035] In the negative electrode interface modifier material of the present invention, the amount of polymer based on the total weight of the sucrinenitrile, polymer, lithium salt, and additives is preferably in the range of more than 0% by weight to 20% by weight. For example, the amount of polymer based on the total weight of the sucrinenitrile, polymer, lithium salt, and additives can be any of 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14%, 15%, 16%, 17%, 18%, 19%, and 20% by weight, or within a range between any two of the aforementioned values. When the amount of polymer falls within the specified range, the negative electrode interface modifying material of the present invention can effectively enhance the mechanical performance of a lithium ion battery while maintaining good ionic conductivity of the battery.

[0036] [Lithium salt]

[0037] In the negative electrode interface modifier material of the present invention, the lithium salt can provide a path for lithium ion migration between the negative electrode and the solid electrolyte, similar to the function of the electrolyte. Examples of lithium salts include, but are not limited to, LiTFSI, LiPF, LiBF, LiClO, LiAsF, and LiCFSO. The above-mentioned lithium salts can be used individually or in any combination. In the accompanying example, the lithium salt is LiTFSI.

[0038] In the negative electrode interface modifier material of the present invention, the amount of lithium salt based on the total weight of the sucrinenitrile, polymer, lithium salt, and additives is preferably in the range of 5 to 15% by weight, for example, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, or 15% by weight, or within a range between any two of the aforementioned values.

[0039] [Additives]

[0040] In the negative electrode interface modifier material of the present invention, the additive refers to an electrolyte additive that can address the problem of lithium metal catalyzing the nitrile polymerization reaction, thereby improving the cycling stability of the battery. Examples of additives include, but are not limited to, FEC, EC, and VC. The aforementioned additives can be used individually or in any combination. Considering compatibility with other components of the negative electrode interface modifier material and suitability for the composition of lithium-ion batteries, the additive is preferably FEC.

[0041] In the negative electrode interface modifier material of the present invention, the amount of additive based on the total weight of the sucrinenitrile, polymer, lithium salt, and additive is preferably in the range of more than 0 wt% to 15 wt%. For example, the amount of additive based on the total weight of the sucrinenitrile, polymer, lithium salt, and additive can be any of 0.1 wt%, 0.2 wt%, 0.3 wt%, 0.4 wt%, 0.5 wt%, 0.6 wt%, 0.7 wt%, 0.8 wt%, 0.9 wt%, 1 wt%, 2 wt%, 3 wt%, 4 wt%, 5 wt%, 6 wt%, 7 wt%, 8 wt%, 9 wt%, 10 wt%, 11 wt%, 12 wt%, 13 wt%, 14 wt%, and 15 wt%, or a range between any two of the aforementioned values.

[0042] 2. Lithium-ion solid-state battery

[0043] The negative electrode interface modifier material can be used in a lithium ion solid-state battery. Thus, the present invention further provides a lithium ion solid-state battery comprising a positive electrode, a negative electrode, a solid electrolyte, and the aforementioned negative electrode interface modifier material, the negative electrode interface modifier material being disposed between the negative electrode and the solid electrolyte. FIG. 1 illustrates an embodiment of the lithium ion solid-state battery of the present invention, which comprises a current collector 10, a positive electrode 30, a solid electrolyte 40, a negative electrode interface modifier material 50, and a negative electrode 20. The negative electrode interface modifier material 50 is disposed between the negative electrode 20 and the solid electrolyte 40, and the solid electrolyte 40 is disposed between the negative electrode interface modifier material 50 and the positive electrode 30. The current collector 10 is disposed on the other side of the positive electrode 30, opposite the solid electrolyte 40. The current collector 10 can be made of any suitable material, such as aluminum.

[0044] The lithium-ion solid-state battery of the present invention can use known negative electrode materials. Examples of such known negative electrode materials include, but are not limited to, lithium metal, lithium-indium alloy, lithium-aluminum alloy, and silicon-lithium alloy. The aforementioned negative electrode materials can be used individually or in any combination. In the accompanying example, the negative electrode material is lithium, such as a lithium metal sheet.

[0045] The anode interface modifier material of the present invention is used to modify the interface between anode and solid electrolyte to address interfacial issues between a solid electrolyte and anode (typically lithium metal), particularly between a solid electrolyte containing a NASICON (sodium superconductor) structure and lithium metal. Thus, in one embodiment of the present invention, the electrolyte is a solid electrolyte having a NASICON structure, such as a lithium aluminum germanium phosphate-based electrolyte or a lithium aluminum titanium phosphate-based electrolyte. Examples of lithium aluminum germanium phosphate-based electrolytes include Li 1.5 Al 0.5 Ge 1.5 (PO4)3(LAGP). An example of a lithium aluminum titanium phosphate electrolyte is Li 1.4 Al 0.4 Ti 1.6 (PO4)3(LATP). In the accompanying example, the solid electrolyte is LAGP.

[0046] The lithium-ion solid-state battery of the present invention can use known positive electrode materials. Positive electrode materials compatible with lithium-ion batteries can generally be classified into LFP, primary lithium cathode materials, binary lithium cathode materials, and ternary lithium cathode materials. Examples of primary lithium cathode materials include, but are not limited to, LCO, lithium nickel oxide, and lithium manganese oxide. Examples of binary lithium cathode materials include, but are not limited to, lithium nickel cobalt oxide, LNMO (lithium nickel manganese oxide), and lithium manganese cobalt oxide. Examples of ternary lithium cathode materials include, but are not limited to, NCA and NCM. In one embodiment of the present invention, the positive electrode is made of a material selected from the group consisting of LFP, LCO, NCA, and NCM. Examples of NCA include, but are not limited to, LiNi 0.8 Co 0.15 Al 0.05 O2, LiNi 0.8 Co 0.18 Al 0.02 O2 and LiNi 0.9 Co 0.05 Al 0.05Examples of NCMs include, but are not limited to, LiNi 0.33 Co 0.33 Mn 0.33 O2(NCM111), LiNi 0.5 Co 0.2 Mn 0.3 O2(NCM523), LiNi 0.6 Co 0.2 Mn 0.2 O2(NCM622), LiNi 0.8 Co 0.1 Mn 0.1 O2 (NCM811). In the accompanying example, the cathode material is LFP.

[0047] Furthermore, in the lithium ion solid state battery of the present invention, the positive electrode may optionally be subjected to an appropriate surface treatment or coated with other materials to further improve the interfacial stability between the positive electrode and the solid electrolyte, thereby reducing the interfacial impedance. In a preferred embodiment of the present invention, the surface of the positive electrode has an interfacial layer formed of an ionic liquid. The ionic liquid can increase the mobility of lithium ions, thereby increasing the ionic conductivity. A preferred example of the ionic liquid is 1-butyl-1-methylpyrrolidinium bis(trifluoromethylsulfonyl)imide (Pyr). 14 TFSI). Pyr 14 TFSI not only enhances ionic conductivity, but also has good chemical stability, electrochemical stability, hydrophobicity, flame retardancy, and low vapor pressure. 14 Without being bound by theory, it is possible that the Pyr 14 + It is believed that the cations can form a stable lithium ion transfer interface to reduce interfacial impedance. Additionally, the interfacial layer can enhance the performance of the cathode by helping to mitigate deleterious side reactions, thereby preventing the cathode from losing its effectiveness prematurely.

[0048] 3. Working Example

[0049] 3.1. Preparation and Testing of Negative Electrode Interface Modifiers

[0050] First, succinonitrile, LiTFSI, and FEC were mixed uniformly at 60°C, and then PEO was added and stirred at 60°C for 1 hour to obtain a mixture for preparing various negative electrode interface modifiers. The component ratios of each negative electrode interface modifier are shown in Table 1 below, and each negative electrode interface modifier is designated PCE57, PCE107, PCE157, and PCE07, respectively.

[0051] Table 1: Composition of negative electrode interface modifier materials [Table 1]

[0052] The ionic conductivities of PCE57, PCE107, PCE157, and PCE07 were measured at room temperature using a modular potentiostat / galvanostat (Autolab PGSTAT302N), and the results are shown in Figure 2. As can be seen from Figure 2, the ionic conductivities decreased with increasing PEO content, resulting in PCE07 having a conductivity of 1.35 × 10 -3 The results showed that the ionic conductivity of the PET film was 2.5 S / cm, the highest in the PET film. Without being bound by theory, the decrease in ionic conductivity with increasing PEO is thought to be due to the low ionic conductivity of PEO itself.

[0053] In addition, a lithium metal sheet with a diameter of 0.8 mm and a thickness of 0.025 mm was prepared as an electrode sheet. The aforementioned PCE57, PCE107, PCE157, and PCE07 were each pressed onto an electrolyte sheet with a thickness of 0.025 mm and a diameter of 1.2 cm. Then, housings for the button cells were prepared, and the stacking process was carried out in a glove box where both moisture and oxygen levels were below 1 ppm. First, the bottom cover of the button cell was placed, followed by a lithium metal sheet (electrode sheet), an electrolyte sheet, and another lithium metal sheet (electrode sheet), and then the top cover of the button cell was placed on top. Symmetrical cells of PCE57, PCE107, PCE157, and PCE07 were then produced by pressing them at a pressure of 2 MPa using a button cell tablet press.

[0054] The symmetric cell was charged to 0.05 mAh / cm at room temperature. 2 The results are shown in Figure 3. As can be seen from Figure 3, the overpotential increases with increasing PEO content. Furthermore, PCE57, PCE107, and PCE157 all have the stability of lithium metal, indicating that the anode interface modifier can improve chemical stability. Considering the mechanical performance and ionic conductivity, PCE57 was selected as the anode interface modifier for the lithium-ion solid-state battery described below.

[0055] 3.2 Preparation and Testing of Lithium-Ion Solid-State Batteries

[0056] [Preparation of solid electrolyte]

[0057] First, 2.63 g of lithium carbonate (Li2CO3), 6.16 g of germanium dioxide (GeO2), 1 g of aluminum oxide (Al2O3), and 13.54 g of ammonium dihydrogen phosphate (NH4H2PO4) were weighed and mixed uniformly to obtain a mixture. The mixture was placed in a zirconium oxide-lined ball mill, and 5.0 mL of isopropanol was added as a solvent. After mixing, an appropriate amount of zirconium oxide beads was added to the ball mill, and the mixture was ball milled at 300 rpm for 5 hours. The ball-milled mixture was then transferred to an aluminum oxide crucible and held at 80 °C for 12 hours to evaporate the solvent, resulting in a dry powder. The dry powder was then crushed and placed in a box furnace, where the temperature was raised to 380 °C at a heating rate of 3 °C / min, and then sintered for 2 hours. The sintered powder was then crushed again using an agate mortar and pestle. The crushed powder was transferred to a platinum crucible and heated to 1350°C at a heating rate of 3°C / min to obtain a melt, which was then held at the melt temperature for 2 hours. The melt was then poured onto a stainless steel plate preheated to 500°C and pressed with another stainless steel plate to obtain a ceramic sheet. To release thermal stress, the ceramic sheet was annealed at 500°C for 2 hours and then cooled to room temperature. The annealed ceramic sheet was then crystallized at 950°C for 12 hours to obtain a crystalline LAGP solid electrolyte sheet. The LAGP solid electrolyte sheet was then cut and polished with sandpaper to obtain a LAGP solid electrolyte sheet with a thickness of 0.025 cm and a diameter of 1.2 cm.

[0058] [Preparing the electrodes]

[0059] First, LFP as the positive electrode active material, conductive carbon black KS6 as the carbon source, and PVDF as the binder were placed in a mortar in a weight ratio of 75:20:5 and ground for 20 minutes. Then, 2.0 mL of N-methyl-2-pyrrolidone (NMP) as a solvent was added to the mortar, and the mixture was uniformly mixed to obtain a slurry. The slurry was then coated onto aluminum foil to form a layer approximately 150 μm thick. The coated aluminum foil was dried in a vacuum oven at 100 °C for 12 hours to remove the solvent. Next, the dried thin film formed from the slurry was peeled off from the aluminum foil and cut into a circular positive electrode sheet with a diameter of 8 mm and a thickness of 0.1 mm. Finally, 10 μL of Pyrrolidone was added to the mortar. 14 TFSI was added to the positive electrode sheet to wet the sheet, and the Pyr 14 A positive electrode sheet having an interface layer formed from TFSI (hereinafter referred to as "interface layer-containing positive electrode sheet") was prepared.

[0060] In addition, a lithium metal sheet having a diameter of 8 mm and a thickness of 0.2 mm was prepared as a negative electrode sheet.

[0061] [Preparation of symmetric cells]

[0062] First, PCE57 was liquefied at 60°C, and 100 μL of PCE57 was coated on both sides of a LAGP solid electrolyte sheet preheated to 60°C. After the PCE57 was slightly solidified at room temperature, negative electrode sheets were attached and fixed on both sides of the PCE57-coated LAGP solid electrolyte. The PCE57 was then completely solidified, resulting in a composite structure of negative electrode sheet | PCE57 | LAGP solid electrolyte sheet | PCE57 | negative electrode sheet. Next, a housing for the button cell was prepared, and assembly was carried out in a glove box with both moisture and oxygen levels below 1 ppm. The bottom cover of the button cell was placed first, followed by the composite structure of negative electrode sheet | PCE57 | LAGP solid electrolyte sheet | PCE57 | negative electrode sheet, and then the top cover of the button cell was placed on top. The button cells were then pressed at a pressure of 2 MPa using a button cell tablet press to form a symmetric cell containing PCE57.

[0063] Similarly, a control cell was prepared that did not contain PCE57. In this control cell, no PCE57 was used between the negative electrode sheet and the LAGP solid electrolyte sheet. Thus, the structure of the control cell, from bottom to top, was as follows: bottom cover of the button cell, negative electrode sheet, LAGP solid electrolyte sheet, negative electrode sheet, and top cover of the button cell.

[0064] [Preparation of Lithium-ion Solid-State Battery]

[0065] First, PCE57 was liquefied at 60°C, and 100 μL of PCE57 was coated on one side of a LAGP solid electrolyte sheet preheated to 60°C. After the PCE57 was slightly solidified at room temperature, a negative electrode sheet was attached and fixed to the PCE57-coated LAGP solid electrolyte sheet. The PCE57 was then fully solidified to form a composite structure of LAGP solid electrolyte sheet | PCE57 | negative electrode sheet. The housing for the button cell was then prepared, and assembly was carried out in a glove box where both moisture and oxygen levels were below 1 ppm. The bottom cover of the button cell was placed first, followed by the positive electrode sheet, the LAGP solid electrolyte sheet | PCE57 | negative electrode sheet composite (negative electrode sheet facing up), the spring, and finally the top cover of the button cell. The button cell was then pressed at 40 MPa using a button cell tablet press to form a lithium-ion solid-state battery.

[0066] All of the following electrochemical tests were performed at room temperature in a glove box with both moisture and oxygen levels below 1 ppm. The impedance of the symmetric cells with and without PCE57 was measured at room temperature using a modular potentiostat / galvanostat (Autolab PGSTAT302N), and the results are shown in Figure 4. As can be seen from Figure 4, the impedance of the symmetric cell without PCE57 reached 1680 Ω, while the impedance of the symmetric cell with PCE57 decreased to 762 Ω. Without being bound by theory, this is believed to be due to the occurrence of side reactions when the LAGP solid electrolyte is in direct contact with lithium metal, causing the high impedance.

[0067] 0.05mAh / cm 2 The symmetric cell containing PCE57 and the symmetric cell not containing PCE57 were cycled at room temperature under a current density of 0.05 mAh / cm. The results are shown in Figure 5. As can be seen from Figure 5, the symmetric cell containing PCE57 had a current density of 0.05 mAh / cm. 2 The results show that the anode maintains stability for over 100 hours at a current density of 1000 kJ / s. Without being bound by theory, the results are believed to be due to the use of an anode interface modifier (i.e., PCE57) that prevents or reduces side reactions induced by direct contact between the lithium metal and the LAGP solid electrolyte.

[0068] In addition, the lithium-ion solid-state battery was cycled at room temperature at a charge / discharge rate of 0.05C. The results are shown in Figure 6. As can be seen from Figure 6, the charge and discharge capacities during the first cycle were 123.7 mAh / g and 118.6 mAh / g, respectively, with a Coulombic efficiency of 95.8% and an irreversible capacity of 4.2%. After the 15th cycle, the discharge capacity was 121.9 mAh / g and a Coulombic efficiency of 96.8%, indicating good cycling stability. Without being bound by theory, it is believed that the anode interfacial modifier (i.e., PCE57) effectively avoids direct contact between the lithium metal and the LAGP solid electrolyte, thereby reducing side reactions and improving cycling stability.

[0069] The above-described embodiments are used to explain the principle and effectiveness of the present invention and to demonstrate its unique features, but are not intended to limit the scope of the present invention. Those skilled in the art may make various modifications or replacements based on the disclosure and suggestions of the described invention. Therefore, the protection scope of the present invention is as defined in the appended claims. [Explanation of symbols]

[0070] 10 Current collector 20 negative electrode 30 positive electrode 40 Solid electrolyte 50 Negative electrode interface modification material

Claims

1. A negative electrode interface modifying material comprising succinonitrile, a polymer, a lithium salt, and an additive.

2. 2. The negative electrode interface modification material of claim 1, wherein the polymer is selected from the group consisting of poly(ethylene oxide) (PEO), polyacrylonitrile (PAN), poly(vinylidene fluoride) (PVDF), poly(propylene carbonate) (PPC), poly(methyl methacrylate) (PMMA), and combinations thereof.

3. The lithium salt is lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), LiPF 6 , LiBF 4 , LiClO 4 , LiAsF 6 , LiCF 3 SO 3 and combinations thereof.

4. 10. The negative electrode interface modifier material of claim 1, wherein the additive is selected from the group consisting of fluoroethylene carbonate (FEC), ethylene carbonate (EC), vinylene carbonate (VC), and combinations thereof.

5. 5. The negative electrode interface modifier material according to claim 1, wherein the amount of the polymer based on the total weight of the succinonitrile, the polymer, the lithium salt, and the additive is in the range of more than 0 wt % to 20 wt %, and the amount of the additive is in the range of more than 0 wt % to 15 wt %.

6. A lithium ion solid state battery comprising a positive electrode, a negative electrode, a solid electrolyte, and the negative electrode interface modifier material according to any one of claims 1 to 5, The negative electrode interface modifier is disposed between the negative electrode and the solid electrolyte.

7. 7. The lithium-ion solid state battery of claim 6, wherein said negative electrode is made of a material selected from the group consisting of lithium metal, lithium-indium alloy, lithium-aluminum alloy, silicon-lithium alloy, and combinations thereof.

8. 8. The lithium ion solid state battery according to claim 6, wherein the solid electrolyte is a lithium aluminum germanium phosphate-based electrolyte.

9. The lithium aluminum germanium phosphate electrolyte is Li 1.5 Al 0.5 Ge 1.5 (PO 4 ) 3 9. The lithium ion solid state battery of claim 8 having a general formula of (LAGP).

10. The positive electrode is made of lithium iron phosphate (LiFePO 4 , LFP), lithium cobalt oxide (LiCoO 2 10. The lithium ion solid state battery of claim 8, made of a material selected from the group consisting of lithium nickel cobalt aluminum oxide (LCO), lithium nickel cobalt aluminum oxide (NCA), and lithium nickel cobalt manganese oxide (NCM).

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