Solid-state electrolyte thin film and solid-state battery

Abstract

A solid-state electrolyte film includes a first lithium salt, a first polymer, a second polymer, and a solid electrolyte. The first polymer has a molecular weight between 60,000 g / mol and 1,800,000 g / mol. The second polymer is particulate. The solid electrolyte is particulate, and its D50 is between 50 nanometers and 2 micrometers. With this configuration, the solid-state electrolyte film can exhibit high ionic conductivity at room temperature, thereby improving the overall performance of the solid-state battery. Furthermore, the configuration of the solid-state electrolyte film can significantly improve the manufacturing convenience of solid-state batteries.

Description

Technical Field

[0001] This disclosure relates to a solid electrolyte film and a solid-state battery including the solid electrolyte film. Background Technology

[0002] With the rapid advancement of technology, various portable batteries have emerged, and people's demands for high performance and lightweight portable batteries are increasing. As these demands grow stronger, lithium-ion batteries have gained significant attention and widespread use due to their high energy density and rapid charging capabilities. Lithium-ion batteries typically use liquid electrolytes as the conductive material; however, liquid electrolytes have drawbacks such as the risk of leakage, lack of long-term stability, susceptibility to corrosion and flammability, poor safety, and low reliability, failing to meet safety requirements.

[0003] In light of this, solid-state electrolytes are gradually replacing the more dangerous liquid electrolytes. However, solid-state electrolytes still have many problems, such as low ionic conductivity at room temperature and high interface impedance between the solid-state electrolyte and the positive and negative electrodes. Therefore, effectively improving these shortcomings of solid-state electrolytes is currently a key focus of industry research and development. Summary of the Invention

[0004] According to some embodiments disclosed herein, a solid electrolyte film includes a first lithium salt, a first polymer, a second polymer, and a solid electrolyte. The first polymer has a weight-average molecular weight between 60,000 g / mol and 1,800,000 g / mol. The second polymer is particulate. The solid electrolyte is particulate, and the particle size D50 of the solid electrolyte is between 50 nanometers and 2 micrometers.

[0005] In some embodiments disclosed herein, the weight ratio of the first lithium salt, the first polymer, the second polymer, and the solid electrolyte is 16 to 25 : 26 to 34 : 5 to 20 : 10 to 40.

[0006] In some embodiments disclosed herein, the first polymer is a fluorine-containing polymer.

[0007] In some embodiments disclosed herein, the melting point of the first polymer is between 160°C and 175°C, and the thermal stability temperature of the first polymer is between 300°C and 400°C.

[0008] In some embodiments disclosed herein, the first lithium salt includes lithium fluoride, lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethanesulfonyl)imide, lithium bis(perfluoroethylsulfonyl)imide, lithium dioxaborate, or combinations thereof.

[0009] In some embodiments disclosed herein, the first polymer comprises polyvinylidene fluoride, polyvinylidene fluoride-hexafluoropropylene copolymer or a combination thereof, and the second polymer comprises polyacrylic acid, polymethyl methacrylate, polyethylene glycol, polyethylene glycol diglycidyl ether or a combination thereof.

[0010] In some embodiments disclosed herein, the solid electrolyte includes lithium lanthanum zirconium oxide, lithium lanthanum zirconium tantalum oxide, lithium lanthanum titanium oxide, lithium lanthanum tantalum oxide, lithium titanium aluminum phosphate, or combinations thereof.

[0011] In some embodiments disclosed herein, the first polymer has a first weight average molecular weight, a second weight average molecular weight, and a third weight average molecular weight, wherein the first weight average molecular weight is between 800,000 g / mol and 1,000,000 g / mol, the second weight average molecular weight is between 1,300,000 g / mol and 1,500,000 g / mol, and the third weight average molecular weight is between 60,000 g / mol and 200,000 g / mol.

[0012] In some embodiments disclosed herein, the weight ratio of the first polymer having a first weight average molecular weight, the first polymer having a second weight average molecular weight, and the first polymer having a third weight average molecular weight is 6~10: 1.5~3: 1.

[0013] In some embodiments disclosed herein, the solid electrolyte has a first particle size D50, a second particle size D50, and a third particle size D50, wherein the first particle size D50 is between 0.8 micrometers and 1.4 micrometers, the second particle size D50 is between 0.25 micrometers and 0.5 micrometers, and the third particle size D50 is between 80 nanometers and 150 nanometers.

[0014] In some embodiments disclosed herein, the weight ratio of the solid electrolyte having a first particle size D50, the solid electrolyte having a second particle size D50, and the solid electrolyte having a third particle size D50 is 10~20 : 30~45 : 35~50.

[0015] According to some embodiments disclosed herein, a solid-state battery includes the aforementioned solid electrolyte film, a positive electrode, and a negative electrode. The thickness of the solid electrolyte film is between 20 micrometers and 70 micrometers. The positive electrode and the negative electrode are respectively disposed on opposite surfaces of the solid electrolyte film.

[0016] In some embodiments disclosed herein, the solid-state battery further includes a gel structure and a buffer structure. The gel structure is disposed between the positive electrode and the solid electrolyte film, and includes a second lithium salt, a first polymer, and a crystallization-inhibiting additive. The buffer structure is disposed between the negative electrode and the solid electrolyte film, wherein the buffer structure is a gel structure or an ionic liquid.

[0017] In some embodiments disclosed herein, the thickness of the gel structure is between 1 micrometer and 10 micrometers, and the volume of the ionic liquid on a 1 square centimeter solid electrolyte film is between 10 microliters and 40 microliters.

[0018] According to the embodiments disclosed above, since the solid electrolyte film disclosed includes a first lithium salt, a first polymer, a second polymer, and a solid electrolyte with a specific particle size, the solid electrolyte film can have a high ionic conductivity at room temperature, thereby improving the overall performance of the solid-state battery. On the other hand, since the present disclosure directly integrates the first lithium salt, the first polymer, the second polymer, and the solid electrolyte into a single film to form a solid electrolyte film, the convenience of the process can be greatly improved. Attached Figure Description

[0019] To make the above and other objects, features, advantages and embodiments disclosed herein more apparent and understandable, the accompanying drawings are described below:

[0020] Figure 1 A cross-sectional schematic diagram of a solid-state battery according to some embodiments of this disclosure is shown. Detailed Implementation

[0021] The following describes several embodiments of this disclosure with reference to the accompanying drawings. For clarity, many practical details will be described in the following description. However, it should be understood that these practical details should not be used to limit this disclosure. That is, in some embodiments of this disclosure, these practical details are not essential and therefore should not be used to limit this disclosure. In addition, for the sake of simplicity, some conventional structures and components will be shown in the drawings in a simple schematic manner. Furthermore, for the reader's convenience, the dimensions of the components in the drawings are not drawn to scale.

[0022] It should be understood that relative terms such as “down” or “bottom” and “up” or “top” may be used herein to describe the relationship of one element to another, as illustrated in the accompanying drawings. It should be understood that relative terms are intended to include different orientations of the device beyond those shown in the figures. For example, if a device in one of the figures is flipped, an element described as being “down” to other elements will be oriented “up” to other elements. Thus, the exemplary term “down” can include both “down” and “up” orientations, depending on the specific orientation of the figure. Similarly, if a device in one of the figures is flipped, an element described as being “down” or “below” to other elements will be oriented “above” to other elements. Thus, the exemplary term “down” or “below” can include both “up” and “down” orientations.

[0023] This disclosure provides a solid electrolyte film and a solid-state battery including the solid electrolyte film. Because the solid electrolyte film of this disclosure comprises a lithium salt, two types of polymers, and a solid electrolyte with a specific particle size, it can exhibit high ionic conductivity. Furthermore, by using a gel structure with ionic conductivity similar to that of the solid electrolyte film to tightly bond the electrodes (positive / negative electrodes) to the solid electrolyte film, a low interface impedance between the solid electrolyte film and the electrodes can be achieved, which is beneficial for ion conduction at the interface. As a result, the solid electrolyte can still exhibit good performance even at room temperature (e.g., in the temperature range between 20°C and 60°C).

[0024] Please see Figure 1 The diagram illustrates a cross-sectional schematic of a solid-state battery 100 according to some embodiments of the present disclosure. The solid-state battery 100 of the present disclosure includes a negative electrode, a positive electrode, and a solid electrolyte film 130, wherein the negative electrode may, for example, include a negative electrode material layer 110 and a negative electrode current collector 140, and the positive electrode may, for example, include a positive electrode material layer 120 and a positive electrode current collector 150. In some embodiments, the negative electrode may include, for example, a negative electrode material layer 110 of a negative electrode material S1, which is graphite, mesophase carbon microspheres, silicon-carbon, silicon-oxygen-carbon, lithium metal, lithium alloy, lithium titanate (LTO) or a combination thereof, and a negative electrode current collector 140, for example, copper foil, while the positive electrode may include, for example, a positive electrode material layer 120 of a positive electrode material S2, which is a positive electrode material S2, which is a positive electrode material layer 120 of a positive electrode material S2, which is a positive electrode material layer 120, for example, aluminum foil, and a combination thereof. In some embodiments, the negative electrode and the positive electrode are respectively disposed on opposite surfaces of the solid electrolyte film 130 (e.g., the first surface 131 and the second surface 133). More specifically, the negative electrode material layer 110 and the positive electrode material layer 120 sandwich the solid electrolyte film 130 therebetween, and the negative electrode current collector 140 and the positive electrode current collector 150 sandwich the negative electrode material layer 110, the positive electrode material layer 120 and the solid electrolyte film 130 therebetween.

[0025] In some embodiments, the solid-state battery 100 may further include a gel structure 160 and a buffer structure 170. The gel structure 160 may be disposed between the positive electrode material layer 120 and the solid electrolyte film 130, and the buffer structure 170 may be disposed between the negative electrode material layer 110 and the solid electrolyte film 130. In some embodiments, the buffer structure 170 is equivalent to the gel structure 160; that is, the gel structure 160 may be disposed not only between the positive electrode material layer 120 and the solid electrolyte film 130, but also between the negative electrode material layer 110 and the solid electrolyte film 130. In other embodiments, the buffer structure 170 is an ionic liquid (which will be further described below). The general structure of the solid-state battery 100 disclosed herein is as described above and... Figure 1 As shown, the following description will provide a more detailed explanation of the solid electrolyte film 130, gel structure 160, and buffer structure 170 in the solid-state battery 100. It should be noted that, for clarity, Figure 1 In the illustration of the solid-state battery 100, some components are shown as separate from each other, but in the actual structure of the solid-state battery 100, the components are tightly integrated with each other.

[0026] In some embodiments, the solid electrolyte film 130 includes a first lithium salt, a first polymer, a second polymer, and a solid electrolyte, wherein the first lithium salt, the first polymer, the second polymer, and the solid electrolyte are uniformly mixed with each other. Specifically, the first lithium salt may be, for example, lithium fluoride (LiF), lithium bis(fluorosulfonyl)imide (LiO4NS2F2, abbreviated as LiFSI), lithium bis(trifluoromethanesulfonyl)imide (LiN(CF3SO2)2, abbreviated as LiTFSI), lithium bis(perfluoroethylsulfonyl)imide (Li(C2F5SO2)2N, abbreviated as LiBETI), lithium bis(oxalate borate) (LiB(C2O4)2, abbreviated as LiBOB), or combinations thereof; the first polymer may be, for example, polyvinylidene fluoride (PVDF), polyvinylidene fluoride-hexafluoropropylene copolymer (PVDF-HFP), or combinations thereof; the second polymer may be, for example, poly(acrylic acid), poly(PAA), polymethyl methacrylate (PMMA), etc. The electrolyte may be methacrylate (PMMA), polyethylene glycol diglycidyl ether (DIEPEG), polyethylene glycol (PEG), or a combination thereof; while the solid electrolyte may be, for example, lithium lanthanum zirconium oxide (Li7La3Zr2O). 12(LLZO for short), lithium lanthanum zirconium tantalum oxide (e.g., Li) 5.5 La3Zr 1.75 Ta 0.25 O 12 (LLZTO for short), lithium lanthanum titanium oxide (e.g., La) 0.57 Li 0.29 TiO3, abbreviated as LLTO, lithium lanthanum tantalum oxide (e.g., Li) 0.35 La 0.57 Ta 0.8 O3, abbreviated as LLTAO), lithium aluminum titanium phosphate (e.g., Li) 1.3 Al 0.3 Ti 1.7 (PO4)3, abbreviated as LATP) or combinations thereof.

[0027] In some embodiments, the solid electrolyte film 130 can have better toughness and mechanical resistance by controlling the weight-average molecular weight of the first polymer within a certain range. Specifically, since the negative electrode material layer 110 and the positive electrode material layer 120 continuously compress the solid electrolyte film 130 during the operation of the solid-state battery 100, controlling the weight-average molecular weight of the first polymer can give the solid electrolyte film 130 good toughness and mechanical resistance, thereby avoiding the impact on the cycle life of the solid-state battery 100 and the short circuit caused by the expansion and compression of the negative electrode material layer 110 and the positive electrode material layer 120. In some embodiments, the weight-average molecular weight of the first polymer is between 60,000 g / mole and 1,800,000 g / mole. Specifically, if the weight-average molecular weight of the first polymer is less than 60,000 g / mole, the poor chain bonding of the first polymer results in its inability to provide the solid electrolyte film 130 with good toughness and mechanical resistance; if the weight-average molecular weight of the first polymer is greater than 1,800,000 g / mole, the viscosity of the first polymer is too high, which is not conducive to the coating of the colloid (which can be regarded as a precursor of the solid electrolyte film 130) during the process, thereby affecting the yield of the solid electrolyte film 130. In a preferred embodiment, the weight-average molecular weight of the first polymer can be between 80,000 g / mole and 1,300,000 g / mole to better achieve the above-mentioned effects.

[0028] In some embodiments, the first polymer comprises three polymers with different molecular weights. Specifically, the first polymer has a first weight-average molecular weight, a second weight-average molecular weight, and a third weight-average molecular weight, wherein the first weight-average molecular weight is between 800,000 g / mol and 1,000,000 g / mol, the second weight-average molecular weight is between 1,300,000 g / mol and 1,500,000 g / mol, and the third weight-average molecular weight is between 60,000 g / mol and 200,000 g / mol. The first polymer having the first weight-average molecular weight can be used as the main agent for film formation, and after molding, it can become the main structure of the solid electrolyte film 130. Its viscosity in the colloidal state is suitable for coating processes, which is beneficial for the molding of the solid electrolyte film 130. The first polymer having the second weight-average molecular weight can help improve the mechanical strength (e.g., elongation and stress) of the solid electrolyte film 130. The first polymer having the third weight-average molecular weight can act as a dispersant and protectant for the solid electrolyte, ensuring that the solid electrolyte is completely and uniformly dispersed in the solid electrolyte film 130. To improve the mechanical strength of the solid electrolyte film 130, using a first polymer with a second weight average molecular weight is preferable to using only a polymer with a weight average molecular weight of 1,000,000 g / mol or less as the first polymer. Using only a polymer with a weight average molecular weight of 1,300,000 to 1,500,000 g / mol as the first polymer makes colloidal coating more difficult, and the film thickness and condition are harder to control. Overall, by including three polymers with different molecular weights as the first polymer, the solid electrolyte film 130 can be facilitated to form a film and possess a stable main structure, while also exhibiting excellent mechanical strength and ensuring complete and uniform dispersion of the solid electrolyte within the film. In some specific examples, the weight ratio of the first polymer with a first weight average molecular weight range, the first polymer with a second weight average molecular weight range, and the first polymer with a third weight average molecular weight range is 6–10 : 1.5–3 : 1 to achieve the aforementioned benefits.

[0029] In some embodiments, the solid electrolyte film 130 can have better performance by controlling the melting point of the first polymer within a certain range. Specifically, during the molding of the solid electrolyte film 130, the solvent (which may be, for example, 4-dimethylaminopyridine, dimethylformamide, dimethylformamide or a combination thereof, and may be doped with a small amount of toluene to increase volatility if necessary) can be removed from the colloid through a baking process, allowing the colloid to gradually form a film. To avoid the adverse effects of micropores or defects formed after solvent evaporation on the performance of the solid electrolyte film 130 (e.g., creating longitudinally penetrating pores or defects in the solid electrolyte film 130, causing micro-short circuits in the solid battery 100), the solvent on the surface of the colloid can be completely removed during the baking process (this step is the first stage), and then the temperature can be gradually increased so that the polymer in the colloid (e.g., the first polymer) approaches its glass transition temperature (Tg) and reaches a partially molten state (this step is the second stage), thereby starting to flow to fill the pores or defects caused by solvent evaporation. Based on the above, by controlling the melting point of the first polymer, the first polymer can remain solid in the first stage and reach a partially molten state in the second stage, thereby avoiding electrical problems such as micro-short circuits in the solid electrolyte film 130 after film formation, and thus improving the electrical performance of the solid electrolyte film 130. In some embodiments, the melting point of the first polymer can be between 160°C and 175°C. Specifically, if the melting point of the first polymer is less than 160°C, the first polymer may reach a molten state in the first stage, thus interfering with solvent removal; while if the melting point of the first polymer is greater than 175°C, the first polymer may not be able to reach a molten state smoothly in the second stage, resulting in too many pores or defects in the solid electrolyte film 130, thus affecting the electrical performance of the solid-state battery 100. In a preferred embodiment, the melting point of the first polymer can be between 160°C and 165°C to better achieve the above-mentioned effects. On the other hand, since a certain amount of heat is generated during the operation of the solid-state battery 100, controlling the melting point of the first polymer within the aforementioned range can prevent the first polymer from melting and causing a short circuit during the operation of the solid-state battery 100. In some embodiments, the thermal stability temperature of the first polymer (e.g., the thermal decomposition temperature obtained by thermogravimetric analysis of the first polymer) may be between 300°C and 400°C to have good stability, thereby enabling the solid-state battery 100 to have good thermal stability during operation. In some embodiments, the crystallizing point of the first polymer is between 120°C and 140°C (preferably between 120°C and 130°C) to have good film-forming properties.

[0030] In some embodiments, the second polymer is particulate to moderately disrupt the continuous extension of the film formed by the first polymer. Specifically, since the first polymer is a small, non-particulate material with good film-forming properties, it easily forms a continuously extending film when it exists alone. When the second polymer is doped into the first polymer, the particulate nature of the second polymer can moderately disrupt (adjust) the bonds between the first polymers, causing the solid electrolyte film 130 to produce an appropriate amount of porosity, thereby improving ion permeability and increasing ion conductivity. In some embodiments, the above-mentioned effects can be further achieved through the ratio of the first polymer to the second polymer. Specifically, the weight ratio of the first polymer to the second polymer can be controlled within the range of 16-25: 26-34.

[0031] In some embodiments, the solid electrolyte is particulate, and the particle size D50 of the solid electrolyte is between 50 nanometers and 2 micrometers to improve the electrical properties of the solid electrolyte film 130. More specifically, when the particle size of the solid electrolyte falls within the above range, its particle size is small and uniform, thus avoiding the unevenness of the surface of the solid electrolyte film 130 caused by large-sized solid electrolytes. This allows the solid electrolyte film 130 to be tightly and fully bonded to its adjacent layers (e.g., gel structure 160 and buffer structure 170), preventing air from existing between the solid electrolyte film 130 and adjacent layers, thereby preventing short circuits or performance degradation. Furthermore, the small and uniform particle size of the solid electrolyte also promotes uniform dispersion of the solid electrolyte in the solid electrolyte film 130, preventing the unevenness of the surface of the solid electrolyte film 130. Based on the above, since the unevenness of the surface of the solid electrolyte film 130 is not caused, the poor performance of the solid electrolyte film 130 due to uneven stress can be avoided. On the other hand, since the total number of small solid electrolyte particles is greater than the total number of large solid electrolyte particles for the same mass, the shuttle channels formed by small solid electrolyte particles are more numerous than those formed by large solid electrolyte particles. Therefore, small solid electrolyte particles can provide superior conductivity, thereby improving the ionic conductivity of the solid-state battery 100. It is worth noting that, generally speaking, the smaller the particle size of the solid electrolyte, the larger the grain boundary surface area and contact area it can generate. However, small solid electrolyte particles are also prone to excessively vigorous reactions during coating, leading to unnecessary side reactions. Therefore, in a preferred embodiment, the particle size of the solid electrolyte can be less than 500 nanometers (e.g., between 50 nanometers and 300 nanometers) to better balance the requirements of homogenization during coating and conductivity after coating.

[0032] In some embodiments, the solid electrolyte includes three different particle size ranges (D50). Specifically, the solid electrolyte has a first particle size (D50), a second particle size (D50), and a third particle size (D50), wherein the first particle size is between 0.8 μm and 1.4 μm, the second particle size is between 0.25 μm and 0.5 μm, and the third particle size is between 80 nm and 150 nm. Specifically, as mentioned earlier, a higher number of small-particle-size solid electrolytes indicates a greater number of shuttle channels per unit volume. However, small-particle-size solid electrolytes are also prone to excessively vigorous reactions and lithium fluorination during coating, making it difficult to coat the colloid into a film, thus affecting the thickness of the solid electrolyte film 130. Therefore, considering the above-mentioned reactivity issues, a solid electrolyte with a larger particle size (i.e., having the first and second particle sizes) can be selected to replace some of the smaller-particle-size (i.e., having the third particle size) solid electrolytes to facilitate film formation of the solid electrolyte film 130. Furthermore, by mixing solid electrolytes with different particle sizes, the final solid electrolyte film 130 can have stronger structural strength. Overall, by configuring the solid electrolytes with the above three different particle sizes, the solid electrolyte film 130 can have better film-forming properties and stronger structural strength. In some embodiments, the weight ratio of the solid electrolyte with the first particle size, the solid electrolyte with the second particle size, and the solid electrolyte with the third particle size is 10~20 : 30~45 : 35~50 to facilitate the achievement of the above-mentioned effects.

[0033] Based on the above, the solid electrolyte film 130 disclosed herein may include a first lithium salt, a first polymer, a second polymer, and a solid electrolyte, wherein the weight ratio of the first lithium salt, the first polymer, the second polymer, and the solid electrolyte is 16-25 : 26-34 : 5-20 : 10-40, so that the solid electrolyte film 130 has better uniformity, and thus better ion penetration and conductivity. In some embodiments, the thickness H1 of the solid electrolyte film 130 may be between 10 micrometers and 100 micrometers to combine good durability and toughness with suitable energy density. Specifically, when the thickness H1 of the solid electrolyte film 130 is less than 10 micrometers, the solid electrolyte film 130 is prone to tearing or puncture; when the thickness H1 of the solid electrolyte film 130 is greater than 100 micrometers, the energy density of the solid electrolyte film 130 is prone to be insufficient. In a preferred embodiment, the thickness H1 of the solid electrolyte film 130 may be between 20 micrometers and 70 micrometers to better achieve the above-mentioned effects.

[0034] In some embodiments, the gel structure 160 may include a second lithium salt, the first polymer described above, and a crystallization-inhibiting additive. Specifically, the second lithium salt may be, for example, lithium bis(fluorosulfonyl)imide (LiO4NS2F2, abbreviated as LiFSI), lithium bis(trifluoromethanesulfonyl)imide (LiN(CF3SO2)2, abbreviated as LiTFSI), lithium (fluorosulfonyl)((3-(1-methyl-1H-imidazol-3-ium-3-yl)propyl)sulfonyl)imide (abbreviated as LiFSMIPTFSI), N,N-bis(trifluoromethanesulfonyl)aniline (N,N-Bis(trifluoromethylsulfonyl)aniline) The first polymer can be, for example, polyvinylidene fluoride, polyvinylidene fluoride-hexafluoropropylene copolymer, or a combination thereof, as described above; suitable crystallization inhibitors can be, for example, acrylate polymers such as polybutyl acrylate, polyethylhexyl acrylate, or polymethyl methacrylate; alumina; silica, or a combination thereof. The presence of crystallization inhibitors in the gel structure 160 can adjust the crystallization state of the first polymer and improve ionic conductivity. Since the gel structure 160 can be disposed between the electrode (positive / negative electrode) and the solid electrolyte film 130, the presence of air between the electrode and the solid electrolyte film 130 can be avoided from affecting the ionic conductivity of the solid-state battery 100, and the interface impedance between the electrode and the solid electrolyte film 130 can be reduced. Furthermore, when the solid electrolyte film 130 still has a small number of bumps, the gel structure 160 can also be configured to tightly engage with the solid electrolyte film 130 having an uneven surface, so that the solid electrolyte film 130 can be tightly bonded to the electrode through the gel structure 160. On the other hand, since the formulation of gel structure 160 is similar to that of solid electrolyte film 130 (e.g., both gel structure 160 and solid electrolyte film 130 include lithium salt and a first polymer), gel structure 160 and solid electrolyte film 130 have high compatibility, which helps to improve the electrical performance of solid-state battery 100. In some embodiments, the weight ratio of second lithium salt, first polymer, and crystallization inhibitor falls within the range of 15~30 : 30~40 : 5~15, thereby ensuring that the solid content of gel structure 160 is lower than that of solid electrolyte film 130. In some embodiments, the thickness H2 of gel structure 160 is between 1 micrometer and 10 micrometers to combine good tolerance and toughness with suitable energy density.Specifically, when the thickness H2 of the gel structure 160 is less than 1 micrometer, the gel structure 160 is prone to tearing or puncture; when the thickness H2 of the gel structure 160 is greater than 10 micrometers, the energy density of the gel structure 160 is prone to be insufficient. In a preferred embodiment, the thickness H2 of the gel structure 160 can be between 3 micrometers and 5 micrometers to better achieve the above-mentioned effects.

[0035] In some embodiments, when the buffer structure 170 is an ionic liquid, the ionic liquid may be, for example, N-methyl-N-propylpyrrolidiniumbis(trifluoromethanesulfonyl)imide, abbreviated as [pyrrolidinium bis(trifluoromethanesulfonyl)imide]. 13 [Ntf2]), lithium bis(fluorosulfonyl)imide (LiO4NS2F2 dissolved in diethylpyrrolidinium bis(fluorosulfonyl)imide, abbreviated as Li[FSI] in [C2epyr][FSI]), lithium difluorooxalate borate (C2BF2LiO4, abbreviated as LiDFOB), lithium bis(fluorosulfonyl)imide / N-methyl-N-propylpyrrolidinium bis(fluorosulfonyl)imide (LiO4NS2F2 / C8H) 18 F2N2O4S2, abbreviated as LiFSI / PMPFSI), lithium bis(trifluoromethanesulfonylimide) / N-methyl-N-propylpyrrolidone bis(fluorosulfonylimide) salt (LiN(CF3SO2)2 / C8H 18 F2N2O4S2 (LiTFSI / PMPFSI) or any combination thereof. Ionic liquids can effectively improve ionic conductivity, and only a small amount of ionic liquid is needed to achieve good ion conduction efficiency, and can reduce the interface impedance between the negative electrode material layer 110 and the solid electrolyte film 130. In some embodiments, the volume of ionic liquid on a 1 square centimeter solid electrolyte film 130 is between 10 μL and 40 μL. Specifically, if the volume of ionic liquid is less than 10 μL, it may lead to low ion transfer efficiency or low-temperature performance degradation; if the volume of ionic liquid is greater than 40 μL, it may lead to low energy density. On the other hand, since ionic liquids are resistant to low / high temperatures (e.g., can withstand temperatures from -95°C to 400°C), the safety of the solid-state battery 100 during operation can be maintained.

[0036] It should be understood that the component connections and functions already described will not be repeated, but will be stated separately. The following description will briefly explain the fabrication method of the solid-state battery 100.

[0037] First, a solvent (such as 4-dimethylaminopyridine, dimethylformamide, or a combination thereof, with a small amount of toluene added if necessary), a first polymer, a second polymer, a first lithium salt, and a solid electrolyte are sequentially placed into a planetary stirrer and mixed to form a mixture. The viscosity change of the mixture during stirring is monitored using a viscometer to control the viscosity between 3000 cps and 5000 cps, thereby ensuring that the subsequently formed colloid is suitable for coating. Specifically, when the viscosity of the mixture is less than 3000 cps, the colloid is prone to excessive fluidity, making coating difficult; when the viscosity of the mixture is greater than 5000 cps, the colloid is prone to insufficient fluidity, making it difficult to disperse into a film. In some embodiments, the revolution speed can be, for example, 60 rpm ± 50%, the rotation speed can be, for example, 3500 rpm ± 10%, and the stirring time can be between 2 hours and 5 hours. After thorough stirring and mixing, a colloid is obtained, in which the first polymer, the second polymer, the first lithium salt, and the solid electrolyte solvent are uniformly distributed.

[0038] Subsequently, the colloid is degassed and then introduced into an intermittent coating apparatus for coating. In some embodiments, the doctor blade used during coating is a gap-type doctor blade. In some embodiments, the coating apparatus first coats at a speed of 0.4 m / min to 0.8 m / min for 30 to 90 seconds to confirm that excess colloid has overflowed back onto the inside of the doctor blade, and then coats at a speed of 0.2 m / min to 0.4 m / min until the colloid is exhausted. Next, the coated colloid is surface-dried at a baking distance of 5 to 15 meters and a temperature of 100°C to 130°C in an apparatus such as an oven, followed by a deep-drying treatment at a temperature of 125°C to 135°C in a baking apparatus with unidirectional heating, such as a heating plate, for 0.5 to 1 hour. After performing the above steps, the first baking process is completed.

[0039] Subsequently, the membrane after the first baking process is placed in a device such as an oven for a second baking process. In some embodiments, the second baking process may include a first stage and a second stage, wherein the baking temperature of the first stage is between 80°C and 100°C, and the baking time is between 0.5 hours and 1 hour, while the baking temperature of the second stage is between 160°C and 180°C, and the baking time is between 0.5 hours and 1 hour. As mentioned above, the first stage of baking can completely remove the solvent on the surface of the membrane, while the second stage of baking can bring the polymer in the membrane close to its glass transition temperature and reach a partially molten state, thereby initiating flow to fill the pores or defects caused by solvent evaporation, thereby improving the structural integrity of the solid electrolyte film 130. After performing the above steps, the solid electrolyte film 130 disclosed herein is obtained.

[0040] Next, a gel structure 160 is formed on the surface of the positive electrode material layer 120 opposite to the positive electrode current collector 150 by coating. Then, a solid electrolyte film 130 is adhered to the surface of the gel structure 160 opposite to the positive electrode material layer 120. After standing at room temperature for 0.5 to 1.5 hours, it is placed in a vacuum drying oven for drying to obtain a half-electrode (the half-electrode includes the positive electrode material layer 120, the positive electrode current collector 150, and the solid electrolyte film 130). Subsequently, a buffer structure 170 is formed on the surface of the solid electrolyte film 130 opposite to the gel structure 160. In detail, if the buffer structure 170 is a gel structure 160, it is formed by coating; if the buffer structure 170 is an ionic liquid, it is formed by dripping. After the ionic liquid has fully penetrated into the solid electrolyte film 130, the negative electrode material layer 110 already disposed on the negative electrode current collector 140 is pressed onto the solid electrolyte film 130 through the buffer structure 170 (gel structure 160 or ionic liquid), and then placed in a vacuum drying oven for drying, thereby obtaining the solid-state battery 100 disclosed herein.

[0041] According to the embodiments disclosed above, since the solid electrolyte film disclosed herein includes a first lithium salt, a first polymer, a second polymer, and a solid electrolyte with a specific particle size, the solid electrolyte film can exhibit high ionic conductivity at room temperature, thereby improving the overall performance of the solid-state battery. Furthermore, the configuration of the buffer structure and gel structure can help reduce the interface impedance between the solid electrolyte film and the positive and negative electrode material layers and improve ionic conductivity, thereby improving the overall performance of the solid-state battery. On the other hand, since the first polymer can further include three polymers with different molecular weights, and the solid electrolyte can further have three different particle sizes (D50), it is beneficial for the solid electrolyte film to form a stable main structure, and the solid electrolyte film can have excellent mechanical strength, while allowing the solid electrolyte to be completely and uniformly dispersed in the solid electrolyte film. Moreover, since this disclosure directly integrates the first lithium salt, the first polymer, the second polymer, and the solid electrolyte into a single film to form a solid electrolyte film, the convenience of the process can be greatly improved.

[0042] Although the present disclosure has been described above with reference to embodiments, it is not intended to limit the present disclosure. Those skilled in the art can make various modifications and refinements without departing from the spirit and scope of the present disclosure. Therefore, the scope of protection of the present disclosure shall be determined by the appended claims.

[0043] [Symbol Explanation]

[0044] 100: Solid-state battery

[0045] 110: Negative electrode material layer

[0046] 111: Surface

[0047] 120: Positive electrode material layer

[0048] 121: Surface

[0049] 130: Solid electrolyte film

[0050] 131: First Surface

[0051] 133: Second Surface

[0052] 140: Negative current collector

[0053] 150: Positive current collector

[0054] 160: Gel structure

[0055] 170: Buffer Structure

[0056] H1, H2: Thickness

[0057] S1, S2: Salts.

Claims

1. A solid electrolyte thin film, characterized in that, include: First lithium salt; A first polymer, wherein the first polymer has a first weight average molecular weight, a second weight average molecular weight and a third weight average molecular weight, wherein the first weight average molecular weight is between 800,000 g / mol and 1,000,000 g / mol, the second weight average molecular weight is between 1,300,000 g / mol and 1,500,000 g / mol, and the third weight average molecular weight is between 60,000 g / mol and 200,000 g / mol; The second polymer, wherein the second polymer is particulate; as well as A solid electrolyte, wherein the solid electrolyte is particulate and the particle size D50 of the solid electrolyte is between 50 nanometers and 2 micrometers.

2. The solid electrolyte film according to claim 1, wherein the weight ratio of the first lithium salt, the first polymer, the second polymer and the solid electrolyte is 16~25 : 26~34 : 5~20 : 10~40.

3. The solid electrolyte film according to claim 1 or 2, wherein the first polymer is a fluorine-containing polymer.

4. The solid electrolyte film according to claim 1 or 2, wherein the melting point of the first polymer is between 160°C and 175°C, and the thermal decomposition temperature of the first polymer is between 300°C and 400°C.

5. The solid electrolyte film according to claim 1 or 2, wherein the first lithium salt comprises lithium fluoride, lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethanesulfonyl)imide, lithium bis(perfluoroethylsulfonyl)imide, lithium dioxaborate, or a combination thereof.

6. The solid electrolyte film according to claim 1 or 2, wherein the first polymer comprises polyvinylidene fluoride, polyvinylidene fluoride-hexafluoropropylene copolymer or a combination thereof, and the second polymer comprises polyacrylic acid, polymethyl methacrylate, polyethylene glycol, polyethylene glycol diglycidyl ether or a combination thereof.

7. The solid electrolyte film according to claim 1 or 2, wherein the solid electrolyte comprises lithium lanthanum zirconium oxide, lithium lanthanum zirconium tantalum oxide, lithium lanthanum titanium oxide, lithium lanthanum tantalum oxide, lithium titanium aluminum phosphate, or a combination thereof.

8. The solid electrolyte film according to claim 1, wherein the weight ratio of the first polymer having the first weight average molecular weight, the first polymer having the second weight average molecular weight, and the first polymer having the third weight average molecular weight is 6~10 : 1.5~3 :

1.

9. The solid electrolyte film according to claim 1 or 2, wherein the solid electrolyte has a first particle size D50, a second particle size D50 and a third particle size D50, the first particle size D50 being between 0.8 micrometers and 1.4 micrometers, the second particle size D50 being between 0.25 micrometers and 0.5 micrometers, and the third particle size D50 being between 80 nanometers and 150 nanometers.

10. The solid electrolyte film according to claim 9, wherein the weight ratio of the solid electrolyte having the first particle size D50, the solid electrolyte having the second particle size D50, and the solid electrolyte having the third particle size D50 is 10~20 : 30~45 : 35~50.

11. A solid-state battery, characterized in that, include: The solid electrolyte film according to any one of claims 1 to 10, wherein the thickness of the solid electrolyte film is between 20 micrometers and 70 micrometers; and The positive and negative electrodes are respectively disposed on opposite surfaces of the solid electrolyte film.

12. The solid-state battery according to claim 11, wherein, Also includes: A gel structure is disposed between the positive electrode and the solid electrolyte film, wherein the gel structure comprises: Second lithium salt; The first polymer; and Crystallization inhibitors; and A buffer structure is disposed between the negative electrode and the solid electrolyte film, wherein the buffer structure is a gel structure or an ionic liquid.

13. The solid-state battery of claim 12, wherein the thickness of the gel structure is between 1 micrometer and 10 micrometers, and the volume of the ionic liquid on the solid electrolyte film of 1 square centimeter is between 10 microliters and 40 microliters.

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