Composite solid-state electrolyte and all-solid-state lithium-ion battery

Abstract

This application relates to a composite solid-state electrolyte and an all-solid-state lithium-ion battery. The composite solid-state electrolyte comprises a polymer matrix, a sulfide inorganic filler, a lithium salt, and an interface modifier in a mass ratio of (40~50):(30~40):(15~20):(1~3). The solution provided in this application can simultaneously solve the technical problems of limited energy density, low ionic conductivity, high interfacial impedance between the positive and negative electrodes and the electrolyte, and short cycle life.

Description

Technical Field

[0001] This application relates to the field of battery technology, and in particular to composite solid electrolytes and all-solid-state lithium-ion batteries. Background Technology

[0002] Traditional liquid lithium-ion batteries, using flammable organic liquid electrolytes, pose safety hazards such as leakage, thermal runaway, and even high-temperature explosions. Furthermore, their reliance on polyolefin separators to physically isolate the positive and negative electrodes limits the compactness of the battery structure and the improvement of energy density. All-solid-state lithium batteries, by introducing solid electrolytes, can fundamentally eliminate the safety risks associated with liquid electrolytes. Theoretically, they can increase energy density by more than 40%, and are considered the core development direction for next-generation high-safety, high-energy-density energy storage devices.

[0003] In related technologies, all-solid-state lithium batteries mainly use a single type of solid electrolyte such as polymer or sulfide to improve battery safety and energy density.

[0004] However, these single-type polymer electrolytes face three major bottlenecks that directly restrict the practical application of all-solid-state lithium batteries: First, the low room-temperature ionic conductivity of solid electrolytes limits the rate performance of the batteries; second, poor solid-solid contact and side reactions between the positive and negative electrode active materials and the solid electrolyte result in high interfacial impedance, significantly reducing charge and discharge efficiency and capacity retention; and third, the volume expansion of the electrodes and the dendrite growth of the lithium metal negative electrode during cycling can easily cause the solid electrolyte to crack, resulting in poor cycle stability.

[0005] Therefore, there is an urgent need to provide a technical solution that can simultaneously address the issues of limited energy density, low ionic conductivity, high impedance at the positive and negative electrode-electrolyte interface, and short cycle life. Summary of the Invention

[0006] To address or partially address the problems existing in related technologies, this application provides a composite solid electrolyte and an all-solid-state lithium-ion battery, which can simultaneously solve the technical problems of limited energy density, low ionic conductivity, high impedance at the positive and negative electrode-electrolyte interface, and short cycle life.

[0007] The first aspect of this application provides a composite solid electrolyte comprising a polymer matrix, a sulfide inorganic filler, a lithium salt, and an interface modifier in a mass ratio of (40~50):(30~40):(15~20):(1~3).

[0008] In some embodiments of the present invention, the polymer matrix includes at least one of polyethylene oxide, polypropylene oxide, polyoxyethylene-polyoxypropylene block copolymer, and polypropylene carbonate.

[0009] In some embodiments of the present invention, the sulfide inorganic filler includes Li7P3S. 11 Li 10 GeP2S 12 At least one of Li3PS4.

[0010] In some embodiments of the present invention, the lithium salt includes at least one of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium hexafluoroarsenate, lithium perchlorate, lithium bis(trifluoromethanesulfonyl)imide, lithium difluoroborate, lithium bis(oxalateborate), lithium difluorooxalateborate, lithium difluorophosphate, and lithium oxalate phosphate.

[0011] In some embodiments of the present invention, the interface modifier includes at least one selected from lithium phosphate, lithium silicate, and lithium hexafluorotitanate; and / or, the number-average molecular weight of the polymer matrix is ​​5 × 10⁻⁶. 5 ~1×10 6 .

[0012] In some embodiments of the present invention, the particle size of the sulfide inorganic filler is 50 nm to 100 nm.

[0013] In some embodiments of the present invention, the particle size of the interface modifier is 10 nm to 20 nm.

[0014] In some embodiments of the present invention, the mass percentage of the interface modifier in the composite solid electrolyte is 1.5% to 2.5%.

[0015] A second aspect of this application provides an all-solid-state lithium-ion battery, comprising a positive electrode, a composite solid electrolyte layer, and a negative electrode stacked sequentially, wherein the composite solid electrolyte layer is the aforementioned composite solid electrolyte.

[0016] In some embodiments of the present invention, the positive electrode sheet comprises a positive electrode active material, a composite solid electrolyte powder, a conductive agent and a binder in a mass ratio of (75~85):(8~15):(3~6):(2~4), wherein the composite solid electrolyte powder is the aforementioned composite solid electrolyte.

[0017] In some embodiments of the present invention, the positive electrode active material is LiNi. 0.8 Co 0.1 Mn 0.1 O2 or LiNi 0.9 Co 0.05 Mn 0.05 O2.

[0018] In some embodiments of the present invention, the composite solid electrolyte powder in the positive electrode sheet has a mass percentage of 10% to 12%.

[0019] In some embodiments of the present invention, the negative electrode includes a lithium metal substrate and a surface modification layer coated on at least one side of the lithium metal substrate.

[0020] In some embodiments of the present invention, the surface modification layer is a Li3PO4-Li2CO3 composite coating.

[0021] In some embodiments of the present invention, the mass ratio of Li3PO4 to Li2CO3 in the Li3PO4-Li2CO3 composite coating is 2:1 to 4:1.

[0022] In some embodiments of the present invention, the thickness of the Li3PO4-Li2CO3 composite coating is 5nm~10nm.

[0023] In some embodiments of the present invention, the lithium metal substrate is a lithium metal foil with a purity of ≥99.9%; and / or, the thickness of the lithium metal substrate is 50μm~100μm.

[0024] In some embodiments of the present invention, the surface modification layer is prepared by radio frequency magnetron sputtering; and / or, the interfacial impedance between the surface modification layer and the composite solid electrolyte layer is ≤50Ω. cm 2 .

[0025] In some embodiments of the present invention, the all-solid-state lithium-ion battery further includes a packaging shell, wherein the water vapor permeability of the packaging shell is <0.05 g / (m²). 2 24h).

[0026] In some embodiments of the present invention, the interfacial gap between the positive electrode, the composite solid electrolyte layer and the negative electrode is <1 μm.

[0027] The technical solution provided in this application may include the following beneficial results: This application combines a polymer matrix, a sulfide inorganic filler, a lithium salt, and an interface modifier in a mass ratio of (40~50):(30~40):(15~20):(1~3). This allows the sulfide inorganic filler to form a continuous ionic conductive channel, the lithium salt to provide sufficient charge carriers, the interface modifier to stabilize the interface, and the polymer matrix to ensure electronic insulation. Therefore, the resulting solid electrolyte exhibits high ionic conductivity (≥1.2×10⁻⁶) at room temperature. -3 (S / cm) and high electronic insulation (electronic volume resistivity ≥1×10⁻⁶) 12 Ω The system effectively solves the problem of low ionic conductivity by using a polymer-inorganic composite structure that buffers the volume change of the electrode during charging and discharging, inhibits interface peeling and electrolyte rupture, and significantly improves cycle life. At the same time, the introduced interface modifier can passivate the contact interface between the positive and negative electrodes and the electrolyte in situ, greatly reducing the interface impedance between the positive and negative electrodes and the electrolyte. On this basis, the electrolyte system can stably match the high-nickel positive electrode and the lithium metal negative electrode, give full play to the potential of high specific capacity active materials, break through the limitations of traditional systems on the proportion of active material and working voltage, and fundamentally alleviate the bottleneck of limited energy density.

[0028] It should be understood that the above general description and the following detailed description are exemplary and explanatory only, and do not limit this application. Detailed Implementation

[0029] The embodiments of this application will now be described in more detail. It should be understood that this application may be implemented in various forms and should not be limited to the embodiments set forth herein. Rather, these embodiments are provided to make this application more thorough and complete, and to fully convey the scope of this application to those skilled in the art.

[0030] The terminology used in this application is for the purpose of describing particular embodiments only and is not intended to be limiting of the application. The singular forms “a,” “the,” and “the” used in this application and the appended claims are also intended to include the plural forms unless the context clearly indicates otherwise. It should also be understood that the term “and / or” as used herein refers to and includes any or all possible combinations of one or more of the associated listed items.

[0031] It should be understood that although the terms "first," "second," "third," etc., may be used in this application to describe various information, this information should not be limited to these terms. These terms are only used to distinguish information of the same type from one another. For example, without departing from the scope of this application, first information may also be referred to as second information, and similarly, second information may also be referred to as first information. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this application, "multiple" means two or more, unless otherwise explicitly specified.

[0032] In related technologies, all-solid-state lithium batteries mainly use a single type of solid electrolyte, such as polymer or sulfide, to improve battery safety and energy density. However, these single-type polymer electrolytes face three major bottlenecks that directly restrict the practical application of all-solid-state lithium batteries: First, the low room-temperature ionic conductivity of solid electrolytes limits the rate performance of the battery; second, poor solid-solid contact and side reactions between the positive and negative electrode active materials and the solid electrolyte lead to high interfacial impedance, significantly reducing charge-discharge efficiency and capacity retention; third, the volume expansion of the electrodes and the dendrite growth of the lithium metal anode during cycling can easily cause the solid electrolyte to crack, resulting in poor cycle stability. Therefore, there is an urgent need for a technical solution that can simultaneously address the limitations in energy density, low ionic conductivity, high interfacial impedance between the positive and negative electrodes and the electrolyte, and short cycle life.

[0033] To address the aforementioned issues, this application provides a composite solid electrolyte that can simultaneously solve the technical problems of limited energy density, low ionic conductivity, high impedance at the positive and negative electrode-electrolyte interface, and short cycle life.

[0034] This application provides a composite solid electrolyte comprising a polymer matrix, a sulfide inorganic filler, a lithium salt, and an interface modifier in a mass ratio of (40~50):(30~40):(15~20):(1~3).

[0035] In the composite solid electrolyte formulation system of this application embodiment, the polymer matrix provides a flexible framework, the sulfide inorganic filler constructs a high-speed ion channel, the lithium salt provides charge carriers, and the interface modifier suppresses side reactions.

[0036] In the embodiments of this application, the polymer matrix accounts for 40% to 50% of the mass of the composite solid electrolyte, the sulfide inorganic filler accounts for 30% to 40% of the mass of the composite solid electrolyte, the lithium salt accounts for 15% to 20% of the mass of the composite solid electrolyte, and the interface modifier accounts for 1% to 3% of the mass of the composite solid electrolyte.

[0037] If the polymer matrix content is less than 40%, it will result in insufficient mechanical strength and difficulty in suppressing lithium dendrites; the upper limit is 50%; if the polymer matrix content exceeds 50%, it will result in a decrease in sulfide content and a decrease in ionic conductivity.

[0038] If the content of sulfide inorganic filler is less than 30%, it will be difficult to form continuous ion pathways and reduce electrical conductivity; if the content of sulfide inorganic filler is more than 40%, it will lead to increased brittleness and poor processability and interfacial adhesion.

[0039] If the lithium salt content is less than 15%, it will lead to insufficient carrier concentration and limited conductivity; if the lithium salt content is higher than 20%, it will easily precipitate crystals, destroying uniformity.

[0040] If the content of the interface modifier is less than 1%, it is insufficient to effectively passivate the interface; if the content of the interface modifier is higher than 3%, it will dilute the conductive phase and reduce the ion migration efficiency.

[0041] This application embodiment combines a polymer matrix, a sulfide inorganic filler, a lithium salt, and an interface modifier in a mass ratio of (40~50):(30~40):(15~20):(1~3). This allows the sulfide inorganic filler to form a continuous ionic conductive channel, the lithium salt to provide sufficient charge carriers, the interface modifier to stabilize the interface, and the polymer matrix to ensure electronic insulation. Therefore, the resulting solid electrolyte exhibits high ionic conductivity (≥1.2×10⁻⁶) at room temperature. -3 (S / cm) and high electronic insulation (electronic volume resistivity ≥1×10⁻⁶) 12 Ω The system effectively solves the problem of low ionic conductivity by using a polymer-inorganic composite structure that buffers the volume change of the electrode during charging and discharging, inhibits interface peeling and electrolyte rupture, and significantly improves cycle life. At the same time, the introduced interface modifier can passivate the contact interface between the positive and negative electrodes and the electrolyte in situ, greatly reducing the interface impedance between the positive and negative electrodes and the electrolyte. On this basis, the electrolyte system can stably match the high-nickel positive electrode and the lithium metal negative electrode, give full play to the potential of high specific capacity active materials, break through the limitations of traditional systems on the proportion of active material and working voltage, and fundamentally alleviate the bottleneck of limited energy density.

[0042] In some embodiments of the present invention, the polymer matrix includes at least one of polyethylene oxide, polypropylene oxide, polyoxyethylene-polyoxypropylene block copolymer, and polypropylene carbonate.

[0043] The polymer matrices used in the embodiments of this application all have ether bonds or carbonate groups, which can solubilize lithium salts and promote Li... + Migration. A diverse selection of polymers can optimize mechanical properties while maintaining high ionic conductivity, adapt to different electrode systems, improve interfacial contact, and extend cycle life.

[0044] In some embodiments of the present invention, the sulfide inorganic filler includes Li7P3S. 11 Li 10 GeP2S 12 At least one of Li3PS4.

[0045] The sulfide inorganic fillers selected in this application are all high-ionic-conductivity sulfides, which can form continuous inorganic ion channels. Introducing high-conductivity sulfide inorganic fillers achieves an overall electrolyte ionic conductivity ≥1.2×10⁻⁶. -3The key to S / cm is to directly solve the problem of "low ionic conductivity" and support the high-rate operation of high-energy-density batteries.

[0046] In some embodiments of the present invention, the lithium salt includes at least one of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium hexafluoroarsenate, lithium perchlorate, lithium bis(trifluoromethanesulfonyl)imide, lithium difluoroborate, lithium bis(oxalateborate), lithium difluorooxalateborate, lithium difluorophosphate, and lithium oxalate phosphate.

[0047] The lithium salt selected in this application embodiment can enhance the free Li + Concentration enhances ionic conductivity; some anions (such as TFSI) - It can also participate in the formation of a stable SEI, improving interfacial impedance and cycle life. Among them, lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) has high dissociation degree, thermal stability and good compatibility with polymers.

[0048] In some embodiments of the present invention, the interface modifier includes at least one of lithium phosphate, lithium silicate, and lithium hexafluorotitanate.

[0049] In this embodiment, the interface modifier directly reduces the interfacial impedance of the positive and negative electrodes / electrolyte, solving the problem of high interfacial impedance and improving cycle stability. Among them, lithium phosphate (Li3PO4) is chemically stable, ion-conducting, and electronically insulating, effectively passivating the electrolyte-electrode interface.

[0050] In some embodiments of the present invention, the number-average molecular weight of the polymer matrix is ​​5 × 10⁻⁶. 5 ~1×10 6 .

[0051] In the embodiments of this application, if the number-average molecular weight of the polymer matrix is ​​less than 5 × 10⁻⁶ 5 This can lead to poor mechanical strength and weak film-forming properties; if the number average molecular weight of the polymer matrix is ​​higher than 1×10⁻⁶, it will result in poor mechanical strength and weak film-forming properties. 6 If the solution viscosity is high, processing becomes difficult, and increased crystallinity hinders ion migration.

[0052] Therefore, in this embodiment, the number-average molecular weight of the polymer matrix is ​​set to 5 × 10⁻⁶. 5 ~1×10 6 It can balance film-forming properties, flexibility and ion conductivity, which helps maintain the integrity of the electrolyte layer, adapt to changes in electrode volume during cycling, and extend lifespan.

[0053] In some embodiments of the present invention, the particle size of the sulfide inorganic filler is 50 nm to 100 nm.

[0054] In the embodiments of this application, if the particle size of the sulfide inorganic filler is less than 50 nm, it will easily agglomerate due to being too fine and unevenly dispersed; if the particle size of the sulfide inorganic filler is greater than 100 nm, the specific surface area will be small, the bonding with the polymer interface will be weak, and it will easily cause film defects.

[0055] Therefore, in this embodiment, the particle size of the sulfide inorganic filler is set to 50nm~100nm, which is conducive to uniform dispersion, forming dense and continuous ion channels and improving conductivity; at the same time, the small size buffers stress, reduces cracks, and improves cycle stability.

[0056] In some embodiments of the present invention, the particle size of the interface modifier is 10 nm to 20 nm.

[0057] In the embodiments of this application, if the particle size of the interface modifier is less than 10 nm, it will be easily oxidized or deactivated; if the particle size of the interface modifier is greater than 20 nm, it will be difficult to form a uniform coating layer at the interface.

[0058] Therefore, in this embodiment of the application, the particle size of the interface modifier is set to 10nm~20nm, which can ensure that the interface modifier can effectively cover the surface of the active particles, suppress side reactions to the maximum extent, and reduce interface impedance.

[0059] In some embodiments of the present invention, the mass percentage of the interface modifier in the composite solid electrolyte is 1.5% to 2.5%.

[0060] In this embodiment, the mass percentage of the interface modifier is further set to 1.5%~2.5%, which can achieve a better balance between effective interface passivation and maintaining high ionic conductivity, significantly reduce interface impedance, and improve cycle life.

[0061] To further understand the present invention, the following embodiments are provided to illustrate the present application. These embodiments are for illustrative purposes only and are not intended to limit the scope of the present application.

[0062] This application also provides an all-solid-state lithium-ion battery, including a positive electrode, a composite solid electrolyte layer and a negative electrode stacked sequentially, wherein the composite solid electrolyte layer is the aforementioned composite solid electrolyte.

[0063] The embodiments of this application completely eliminate the need for liquid electrolyte and membrane by adopting a sandwich structure of positive electrode-solid electrolyte-negative electrode.

[0064] The all-solid-state lithium-ion battery of this application has a simplified structure and high safety; when combined with a high-conductivity composite electrolyte, it can achieve a synergistic improvement in high energy density, high ionic conductivity, low impedance at the positive and negative electrode-electrolyte interface, and long cycle life.

[0065] In some embodiments of the present invention, the positive electrode sheet includes a positive electrode active material, a composite solid electrolyte powder, a conductive agent and a binder in a mass ratio of (75~85):(8~15):(3~6):(2~4), and the composite solid electrolyte powder is the aforementioned composite solid electrolyte.

[0066] In this embodiment, the content of the positive electrode active material is not higher than 85% to prevent insufficient ion pathways due to excessive content; the content of the positive electrode active material is not lower than 75% to prevent energy density reduction due to excessive content.

[0067] The content of composite solid electrolyte powder should not exceed 15% to prevent excessive dilution of active substances; the content of composite solid electrolyte powder should not be less than 8% to prevent insufficient ion network construction.

[0068] By setting this ratio, the embodiments of this application can ensure a dual continuous ion / electron network within the positive electrode, reduce polarization, improve capacity utilization at high voltage, and solve the problems of limited energy density and high interface impedance.

[0069] In some embodiments of the present invention, the positive electrode active material is LiNi. 0.8 Co 0.1 Mn 0.1 O2 or LiNi 0.9 Co 0.05 Mn 0.05 O2.

[0070] The positive electrode active material selected in this application embodiment is a high-nickel ternary material, which has high specific capacity and is the key to improving energy density.

[0071] In some embodiments of the present invention, the mass percentage of the composite solid electrolyte powder in the positive electrode sheet is 10% to 12%.

[0072] In this embodiment, the mass percentage of the composite solid electrolyte powder is set to 10%~12%, which can effectively reduce the impedance of the cathode / electrolyte interface, improve rate performance and cycle stability, and maintain high energy density.

[0073] In some embodiments of the present invention, the negative electrode includes a lithium metal substrate and a surface modification layer coated on at least one side of the lithium metal substrate.

[0074] In this embodiment, the lithium metal substrate of the negative electrode is the core for achieving high energy density; the surface modification layer can suppress dendrites and side reactions, and extend cycle life.

[0075] In some embodiments of the present invention, the surface modification layer is a Li3PO4-Li2CO3 composite coating.

[0076] In this embodiment, Li3PO4 has high ionic conductivity; Li2CO3 can regulate interfacial wettability. The two work together to form a stable SEI film, reduce lithium / electrolyte interface impedance, suppress dendrite penetration, and solve the problems of high interface impedance and short cycle life.

[0077] In addition, the interface modifiers in this application include lithium phosphate, etc., to improve the interfacial compatibility of the electrolyte; the surface modification layer adopts a Li3PO4-Li2CO3 composite coating, which forms a homologous matching interface with lithium phosphate, reduces interfacial impedance, and improves battery stability and ion transport efficiency.

[0078] In some embodiments of the present invention, the mass ratio of Li3PO4 to Li2CO3 in the Li3PO4-Li2CO3 composite coating is 2:1 to 4:1.

[0079] In the embodiments of this application, if the proportion of Li3PO4 is too low (e.g., <2:1), it will lead to insufficient ion conductivity; if the proportion of Li3PO4 is too high (e.g., >4:1), it will lead to poor interfacial wettability and poor contact.

[0080] Therefore, in this embodiment of the application, the mass ratio of Li3PO4 to Li2CO3 in the Li3PO4-Li2CO3 composite coating is set to 2:1 to 4:1, which can optimize interfacial ion transport and physical contact, reduce interfacial impedance, and improve cycle stability.

[0081] In some embodiments of the present invention, the thickness of the Li3PO4-Li2CO3 composite coating is 5nm~10nm.

[0082] In this embodiment, if the coating thickness is less than 5 nm, it is difficult to form a continuous and dense coating layer, which cannot effectively isolate the direct contact between lithium metal and the solid electrolyte, leading to continuous occurrence of side effects, a rapid increase in interfacial impedance, and a significant decrease in cycle stability. If the coating thickness exceeds 10 nm, the excessively thick coating will introduce additional ion transport resistance, which will increase the interfacial impedance and reduce rate performance.

[0083] Therefore, in this embodiment, the thickness of the Li3PO4-Li2CO3 composite coating is set to 5nm~10nm. The Li3PO4-Li2CO3 composite coating can form a complete and uniform solid electrolyte interface (SEI) layer, effectively suppressing side reactions and lithium dendrite penetration, without significantly hindering Li + Cross-interface migration.

[0084] In some embodiments of the present invention, the lithium metal substrate is a lithium metal foil with a purity of ≥99.9%.

[0085] The embodiments of this application use high-purity lithium metal substrate, which can reduce side reactions and dendrite nucleation sites caused by impurities and provide cycle life.

[0086] In some embodiments of the present invention, the thickness of the lithium metal substrate is 50 μm to 100 μm.

[0087] In this embodiment, the thickness of the lithium metal substrate is not less than 50 μm to prevent it from being too thin and easily breaking during pressing or cycling; the thickness of the lithium metal substrate is not more than 100 μm to prevent excessive thickness from increasing inactive mass and reducing battery-grade energy density.

[0088] In some embodiments of the present invention, the surface modification layer is prepared by radio frequency magnetron sputtering.

[0089] This application embodiment utilizes a radio frequency magnetron sputtering process to coat a lithium metal substrate onto its surface. This process can prepare a dense, uniform, and ultra-thin coating that bonds firmly to the lithium substrate. This ensures the integrity of the modified layer, effectively passivates the interface, reduces impedance, and extends lifespan.

[0090] In some embodiments of the present invention, the interfacial impedance between the surface-modified layer and the composite solid electrolyte layer is ≤50Ω. cm 2 .

[0091] In the embodiments of this application, the interfacial impedance between the surface-modified layer and the composite solid electrolyte layer is much lower than that of traditional solid-state batteries (>1000Ω). cm 2 This solves the problem of high interface impedance, enabling high-rate charge / discharge and excellent cycle performance.

[0092] In some embodiments of the present invention, the all-solid-state lithium-ion battery further includes a packaging shell, wherein the water vapor permeability of the packaging shell is <0.05 g / (m²). 2 24h).

[0093] Because sulfide electrolytes are sensitive to H2O, they require high-barrier encapsulation (such as a stainless steel hard shell or a high-barrier aluminum-plastic film). This prevents electrolyte hydrolysis and ensures long-term cycling stability.

[0094] In some embodiments of the present invention, the interfacial gap between the positive electrode, the composite solid electrolyte layer and the negative electrode is <1 μm.

[0095] This application's embodiments achieve tight contact through hot pressing at 10MPa~15MPa, eliminating micron-level voids. This significantly reduces interfacial contact impedance, ensuring efficient ion transport, solving the problem of high interfacial impedance, and supporting stable cycling of high energy density systems.

[0096] In some embodiments, the positive electrode includes a positive current collector and a positive active material coated on at least one side of the positive current collector.

[0097] In some embodiments, the type of positive electrode current collector is not particularly limited, and it can be any known material suitable for use as a positive electrode current collector. In one embodiment, the positive electrode current collector includes metallic materials such as aluminum, stainless steel, nickel plating, titanium, and tantalum, as well as carbon materials such as carbon cloth and carbon paper. In one embodiment, the positive electrode current collector is a metallic material.

[0098] In some embodiments, the positive electrode active material layer comprises a positive electrode active material, a composite solid electrolyte powder, a conductive agent, and a binder.

[0099] In some embodiments, the type of positive conductive agent mentioned in the present application is not limited, and any known conductive agent can be used.

[0100] In some embodiments, the positive electrode conductive agent mentioned in the embodiments of this application includes at least one of carbon materials such as natural graphite, artificial graphite, acetylene black, needle coke, carbon nanotubes, and graphene.

[0101] In one embodiment, there is no limitation on the type of positive electrode binder mentioned in the embodiments of this application, and any known positive electrode binder can be used.

[0102] In some embodiments, the positive electrode binder includes at least one of polyvinylidene fluoride, sodium carboxymethyl cellulose, styrene-butadiene rubber, polyethylene, polypropylene, polyethylene terephthalate, polymethyl methacrylate, polyimide, aromatic polyamide, cellulose, and nitrocellulose.

[0103] On the other hand, one embodiment of this application provides an electrical device including the battery described above.

[0104] For example, the aforementioned electrical devices may include mobile devices (such as mobile phones, laptops, etc.), electric vehicles (such as pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks, etc.), electric trains, ships and satellites, energy storage systems, etc., but are not limited thereto.

[0105] To further understand the present invention, the following embodiments are provided to illustrate the present application. These embodiments are for illustrative purposes only and are not intended to limit the scope of the present application.

[0106] I. Preparation of all-solid-state lithium-ion batteries Example 1 1. Preparation of composite solid electrolyte: Weigh PEO (molecular weight 8×10⁻⁶) according to a mass ratio of 45:35:18:2. 5), Li7P3S 11 LiTFSI and Li3PO4 (particle size 15 nm) were dissolved in acetonitrile and stirred until completely dissolved to form an electrolyte slurry with a solid content of 30%. The slurry was coated onto a PTFE substrate film and dried under vacuum at 60 °C for 8 h. The PTFE substrate film was then peeled off to obtain a 15 μm thick composite solid electrolyte layer (50 mm × 50 mm). Its room temperature ionic conductivity was measured to be 1.5 × 10⁻⁶. -3 S / cm, electronic volume resistivity 2×10 12 Ω cm. The methods for testing ionic conductivity and electronic volume resistivity are as follows.

[0107] 2. Positive electrode sheet: The positive electrode sheet includes positive electrode active material, conductive agent and binder in a mass ratio of (90~93):(3~6):(2~4).

[0108] 3. Negative electrode sheet: The negative electrode sheet includes copper foil and negative electrode active material coated on it. The negative electrode active material includes silicon-based materials.

[0109] 4. Preparation of all-solid-state lithium-ion batteries In an argon glove box (water and oxygen content <0.1ppm), the cathode sheet, composite solid electrolyte layer, and modified lithium metal anode are stacked in that order and pressed with 12MPa pressure for 10min to ensure tight contact at the interface. The 503040 type all-solid-state lithium battery (capacity 3.5Ah) is produced by encapsulating it with a 0.25mm thick stainless steel hard shell.

[0110] 3. Examples 2-27 and Comparative Examples 1-11 The basic preparation methods of Examples 2-27 and Comparative Examples 1-11 are the same as those of Example 1, with the differences shown in Table 1.

[0111] Table 1 Formulation table of composite solid electrolytes

[0112] II. Performance Testing The performance of Examples 2-27 and Comparative Examples 1-11 was characterized as follows, and the test results are shown in Table 2.

[0113] 1. Ionic conductivity testing method: 1) The 15μm thick, 50mm×50mm composite solid electrolyte layer obtained by peeling was placed in a vacuum drying oven at 60℃ and dried for 2h. After cooling to room temperature (25±1℃), it was quickly transferred to an argon glove box.

[0114] 2) Using a micrometer with an accuracy of 0.001 mm, the thickness of the electrolyte layer was measured at 5 different uniform positions, and the average value was taken as the test thickness d; using a vernier caliper with an accuracy of 0.01 mm, the effective area S of the electrolyte layer was measured.

[0115] 3) Turn on the electrochemical workstation and preheat for 30 minutes, calibrate the AC impedance and DC polarization test modules; prepare two stainless steel blocking electrodes with a size of 55mm×55mm and a thickness of 0.2mm, and put them in an argon glove box for later use.

[0116] 4) Inside an argon glove box, the pretreated composite solid electrolyte layer is sandwiched between two stainless steel blocking electrodes to assemble a symmetrical blocking battery consisting of "stainless steel electrode - composite solid electrolyte layer - stainless steel electrode". A slight pressure of 0.5 MPa is applied to ensure that the electrodes and electrolyte layer are in close contact without bubbles or gaps.

[0117] 5) Fix the assembled symmetrical blocking battery onto the test fixture, connect it to the electrode interface of the electrochemical workstation, and ensure that the circuit contacts are good and there is no looseness.

[0118] 6) The test mode is AC impedance spectroscopy, with a frequency range of 1Hz~1MHz and an AC signal amplitude of 10mV (to avoid damaging the electrolyte structure). The test temperature is controlled at 25±1℃. After the system is stabilized by being kept at a constant temperature for 10 minutes, the test is started.

[0119] 7) The electrochemical workstation automatically scans the impedance values ​​at different frequencies to generate Nyquist impedance spectra and saves the data after the test is completed. The workstation's built-in fitting software is used to fit the intersection of the semicircle in the high-frequency region of the Nyquist graph with the real axis and read the bulk impedance R.

[0120] 8) Calculate ionic conductivity: use the formula σ=d / (R×S).

[0121] 2. Electronic resistivity testing method 1) The 15μm thick, 50mm×50mm composite solid electrolyte layer obtained by peeling was placed in a vacuum drying oven at 60℃ and dried for 2h. After cooling to room temperature (25±1℃), it was quickly transferred to an argon glove box.

[0122] 2) Using a micrometer with an accuracy of 0.001 mm, the thickness of the electrolyte layer was measured at 5 different uniform positions, and the average value was taken as the test thickness d; using a vernier caliper with an accuracy of 0.01 mm, the effective area S of the electrolyte layer was measured.

[0123] 3) Turn on the electrochemical workstation and preheat for 30 minutes, calibrate the AC impedance and DC polarization test modules; prepare two stainless steel blocking electrodes with a size of 55mm×55mm and a thickness of 0.2mm, and put them in an argon glove box for later use.

[0124] 4) Inside an argon glove box, the pretreated composite solid electrolyte layer is sandwiched between two stainless steel blocking electrodes to assemble a symmetrical blocking battery consisting of "stainless steel electrode - composite solid electrolyte layer - stainless steel electrode". A slight pressure of 0.5 MPa is applied to ensure that the electrodes and electrolyte layer are in close contact without bubbles or gaps.

[0125] 5) Fix the assembled symmetrical blocking battery onto the test fixture, connect it to the electrode interface of the electrochemical workstation, and ensure that the circuit contacts are good and there is no looseness.

[0126] 6) Keep the connection between the symmetrical blocking battery and the electrochemical workstation unchanged, and switch the test mode to DC polarization mode.

[0127] 7) Set test parameters: Apply a constant DC voltage V=0.1V, test for 300s, record the current value every 10s until the current tends to stabilize (steady-state current fluctuation ≤±5%).

[0128] 8) Read steady-state current: After the current stabilizes, read the steady-state current I.

[0129] 9) Calculate electronic volume resistivity: use the formula ρ=(V×S) / (I×d).

[0130] 3. Energy density 1) In a constant temperature chamber at (25±2)℃, charge the lithium-ion battery at a constant current and constant voltage of 0.2C to 4.3V, charge at a constant voltage to 0.05C, let it stand for 5 minutes, and then discharge it at 0.2C to 3.0V. The capacity obtained by this step is the initial capacity.

[0131] 2) Calculate the volumetric energy density (Wh / Kg) = initial capacity Platform voltage / cell quality.

[0132] 3) Take the average value of 3 parallel samples as the energy density of the system.

[0133] 4. Interface impedance 1) Assemble a symmetric cell in an argon glove box: Li|composite solid electrolyte|Li symmetric cell.

[0134] 2) Use an electrochemical workstation to test AC impedance spectroscopy (EIS): frequency: 1Hz~1MHz, AC amplitude: 5~10mV, temperature: room temperature (25±1℃).

[0135] 3) The mid-frequency semicircle in the impedance spectrum corresponds to the interfacial charge transfer impedance R_ between the lithium metal anode and the solid electrolyte.

[0136] 5. Cyclic capacity retention 1) In a constant temperature chamber at (25±2)℃, the lithium-ion battery was charged to 4.3V at a constant current and constant voltage of 0.2C, then charged to 0.05C at a constant voltage. After standing for 5 minutes, it was discharged to 3.0V at 0.2C. The capacity obtained in this step was taken as the initial capacity. Cyclic tests were performed using 1C charge / 1C discharge, and the capacity retention rate of the battery after 500 cycles was calculated.

[0137] Cycle capacity retention (%) = Discharge capacity at 100th cycle (mAh) / Discharge capacity at first cycle (mAh) × 100%.

[0138] Table 2 Test Results

[0139] Referring to Tables 1 and 2, and through Examples 1, 17, and 18, as well as Comparative Examples 1 to 11, it can be seen that when the composite solid electrolyte comprises a polymer matrix, sulfide inorganic filler, lithium salt, and interface modifier in a mass ratio of (40~50):(30~40):(15~20):(1~3), the room temperature ionic conductivity of the composite solid electrolyte can be ≥1.2×10⁻⁶. -3 S / cm, electronic volume resistivity ≥1×10 12 Ω cm can improve ionic conductivity while also increasing energy density, reducing the impedance of the positive and negative electrode-electrolyte interface, and improving cycle life.

[0140] As can be seen from Examples 1 to 4 and Example 25, when the polymer matrix is ​​selected from polyethylene oxide, polypropylene oxide, polyethylene oxide-polypropylene block copolymer, and polypropylene carbonate, the battery performance can be further improved.

[0141] As can be seen from Examples 1, 5, and 6, as well as Example 26, when Li7P3S is selected as the sulfide inorganic filler... 11 Li 10 GeP2S 12 When Li3PS4 is used, battery performance can be further improved.

[0142] As can be seen from Examples 1, 7 and 8, and Examples 21 and 22, when the particle size of the sulfide inorganic filler is 50nm~100nm, the battery performance can be further improved.

[0143] As can be seen from Examples 1, 9 to 12, when lithium salts such as lithium hexafluorophosphate, lithium tetrafluoroborate, lithium hexafluoroarsenate, lithium perchlorate, lithium bis(trifluoromethanesulfonyl)imide, lithium difluoroborate, lithium bis(oxalateborate), lithium difluorooxalateborate, lithium difluorophosphate, and lithium oxalate phosphate are selected, battery performance can be further improved.

[0144] As can be seen from Examples 1, 13, 14, and 27, when lithium phosphate, lithium silicate, or lithium hexafluorotitanate are selected as interface modifiers, battery performance can be further improved.

[0145] As can be seen from Examples 1, 15, and 16, as well as Examples 23 and 24, when the particle size of the interface modifier is 10 nm to 20 nm, the battery performance can be further improved.

[0146] As can be seen from Examples 1, 19, and 20, when the number-average molecular weight of the polymer matrix is ​​5 × 10⁻⁶… 5 ~1×10 6 At that time, battery performance can be further improved.

[0147] III. Preparation of All-Solid-State Lithium-ion Batteries Example 27 1. Composite solid electrolyte layer: Same as the composite solid electrolyte in Example 1.

[0148] 2. Positive Electrode: Weigh out NCM811 negative electrode, composite solid electrolyte powder (consistent with the composite solid electrolyte composition in Example 1), CNT, and PVDF-HFP according to a mass ratio of 80:12:5:3. Add N-methylpyrrolidone (NMP) to prepare a positive electrode slurry with a solid content of 65%. Coat the slurry onto a 12μm thick aluminum foil, dry the negative electrode at 80℃ for 4 hours, vacuum dry the negative electrode at 120℃ for 12 hours, and roll press (compacted density of negative electrode 3.7 g / cm³). 3 ) to make negative electrode sheets 50mm×50mm, negative electrode sheets and positive electrode sheets (area density of negative electrode 22mg / cm²) 2 ).

[0149] 3. Negative Electrode: A lithium metal foil with a purity of 99.95% (80μm thick) was used as the negative electrode. An 8nm thick Li3PO4-Li2CO3 composite modification layer (Li3PO4 to Li2CO3 mass ratio 3:1) was prepared on its surface using radio frequency magnetron sputtering to form a modified lithium metal negative electrode (size 50mm×50mm). The interfacial impedance between the negative electrode and the composite solid electrolyte was measured to be 45Ω. cm 2 .

[0150] 4. Battery Assembly: In an argon glove box (water and oxygen content < 0.1 ppm), negative electrode sheets are stacked in the following order: "positive electrode negative electrode - negative electrode composite solid electrolyte layer negative electrode - negative electrode modified lithium metal negative electrode". A negative electrode sheet pressure of 12 MPa is applied to press the negative electrode sheets for 10 minutes to ensure tight contact at the interface. A 0.25 mm thick stainless steel hard shell is used to encapsulate the negative electrode sheets, forming a 503040 type all-solid-state lithium battery (capacity 3.5 Ah).

[0151] 5. Examples 28-50 and Comparative Examples 12-22 The basic preparation methods of Examples 28-50 and Comparative Examples 12-22 are the same as those of Example 27, with the differences shown in Table 3.

[0152] Table 3 Formulation of all-solid-state lithium-ion batteries

[0153] IV. Performance Testing Energy density, interfacial impedance and cycling performance were tested for Examples 28-50 and Comparative Examples 12-22. The test results are shown in Table 4.

[0154] Table 4 Test Results

[0155] Table 1 shows the formulation of a composite solid electrolyte + conventional positive and negative electrodes, while Table 3 shows the formulation of a composite solid electrolyte + the improved positive and negative electrodes of this application. Combining Tables 3 and 4, and through Examples 28, 37 to 39, and Comparative Examples 12 to 22, it can be seen that when the all-solid-state lithium-ion battery uses a positive electrode, a composite solid electrolyte layer, and a negative electrode stacked sequentially, and the composite solid electrolyte layer uses the composite solid electrolyte provided in this application, it can ensure a dual continuous ion / electron network in the positive electrode, reduce polarization, improve capacity performance under high voltage, and solve the problems of limited energy density and high interface impedance.

[0156] As can be seen from Examples 28 and 29, and Example 36, when the positive electrode active material is LiNi 0.8 Co 0.1 Mn 0.1 O2 or LiNi 0.9 Co 0.05 Mn 0.05 O2 can increase energy density.

[0157] As can be seen from Examples 28, 30 and 31, and Examples 40 and 41, when the positive electrode sheet includes a positive electrode active material, a composite solid electrolyte powder, a conductive agent and a binder in a mass ratio of (75~85):(8~15):(3~6):(2~4), the battery performance can be further improved.

[0158] As can be seen from Examples 28 and 42, when a lithium metal substrate is used as the negative electrode, the battery performance can be further improved.

[0159] As demonstrated in Examples 28, 43, and 44, battery performance can be further improved when the thickness of the lithium metal substrate is 50 μm to 100 μm.

[0160] As can be seen from Examples 28, 45 and 46, when the surface modification layer of the negative electrode is a Li3PO4-Li2CO3 composite coating, the battery performance can be further improved.

[0161] As can be seen from Examples 28, 34 and 35, and Examples 49 and 50, when the mass ratio of Li3PO4-Li2CO3 in the Li3PO4-Li2CO3 composite coating is 2:1 to 4:1, the battery performance can be further improved.

[0162] As can be seen from Examples 28, 32 and 33, and Examples 47 and 48, when the thickness of the Li3PO4-Li2CO3 composite coating is 5nm~10nm, the battery performance can be further improved.

[0163] Although this application has been described with reference to preferred embodiments, those skilled in the art will understand that various changes can be made and equivalents can be substituted for the elements, as long as they do not depart from the scope of this application. Furthermore, many modifications can be made to adapt particular situations or materials to the teachings of this application, as long as they do not depart from the essential scope of this application. Therefore, this application is not intended to be limited to the specific embodiments disclosed as the best mode of carrying out this application as conceived, but rather this application will include all embodiments falling within the scope of the appended claims.

[0164] All scopes disclosed in this application include endpoints, and endpoints can be combined with each other.

[0165] The various embodiments of this application have been described above. These descriptions are exemplary and not exhaustive, nor are they limited to the disclosed embodiments. Many modifications and variations will be apparent to those skilled in the art without departing from the scope and spirit of the described embodiments. The terminology used herein is chosen to best explain the principles, practical application, or improvement of the technology in the market, or to enable others skilled in the art to understand the embodiments disclosed herein.

Claims

1. A composite solid electrolyte, characterized in that, The composite solid electrolyte comprises a polymer matrix in a mass ratio of (40~50):(30~40):(15~20):(1~3), a sulfide inorganic filler, a lithium salt, and an interface modifier.

2. The composite solid electrolyte according to claim 1, characterized in that, The polymer matrix includes at least one of polyethylene oxide, polypropylene oxide, polyoxyethylene-polyoxypropylene block copolymer, and polypropylene carbonate; and / or The sulfide inorganic filler includes Li7P3S. 11 Li 10 GeP2S 12 At least one of Li3PS4; and / or, The lithium salt comprises at least one of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium hexafluoroarsenate, lithium perchlorate, lithium bis(trifluoromethanesulfonyl)imide, lithium difluoroborate, lithium bis(oxalate-borate), lithium difluorooxalate-borate, lithium difluorophosphate, and lithium oxalate-phosphate; and / or, The interface modifier includes at least one of lithium phosphate, lithium silicate, and lithium hexafluorotitanate; and / or, the number-average molecular weight of the polymer matrix is ​​5 × 10⁻⁶. 5 ~1×10 6 ; and / or, The particle size of the sulfide inorganic filler is 50 nm to 100 nm; and / or, The particle size of the interface modifier is 10 nm to 20 nm; and / or, In the composite solid electrolyte, the mass percentage of the interface modifier is 1.5% to 2.5%.

3. A fully solid-state lithium-ion battery, characterized in that, It includes a positive electrode, a composite solid electrolyte layer and a negative electrode stacked in sequence, wherein the composite solid electrolyte layer is the composite solid electrolyte as described in claim 1 or 2.

4. The all-solid-state lithium-ion battery according to claim 3, characterized in that, The positive electrode sheet comprises a positive electrode active material, a composite solid electrolyte powder, a conductive agent, and a binder in a mass ratio of (75~85):(8~15):(3~6):(2~4), wherein the composite solid electrolyte powder is the composite solid electrolyte as described in claim 1 or 2.

5. The all-solid-state lithium-ion battery according to claim 4, characterized in that, The positive electrode active material is LiNi. 0.8 Co 0.1 Mn 0.1 O2 or LiNi 0.9 Co 0.05 Mn 0.05 O2; and / or, in the positive electrode sheet, the mass percentage of the composite solid electrolyte powder is 10%~12%.

6. The all-solid-state lithium-ion battery according to claim 3, characterized in that, The negative electrode includes a lithium metal substrate and a surface modification layer coated on at least one side of the lithium metal substrate.

7. The all-solid-state lithium-ion battery according to claim 6, characterized in that, The surface modification layer is a Li3PO4-Li2CO3 composite coating.

8. The all-solid-state lithium-ion battery according to claim 7, characterized in that, The mass ratio of Li3PO4 to Li2CO3 in the Li3PO4-Li2CO3 composite coating is 2:1 to 4:1; and / or the thickness of the Li3PO4-Li2CO3 composite coating is 5nm to 10nm.

9. The all-solid-state lithium-ion battery according to claim 6, characterized in that, The lithium metal substrate is a lithium metal foil with a purity ≥ 99.9%; and / or, the thickness of the lithium metal substrate is 50 μm to 100 μm; and / or, the surface modification layer is prepared by radio frequency magnetron sputtering; and / or, the interfacial impedance between the surface modification layer and the composite solid electrolyte layer is ≤ 50 Ω. cm 2 .

10. The all-solid-state lithium-ion battery according to claim 3, characterized in that, The all-solid-state lithium-ion battery also includes a packaging shell, wherein the water vapor permeability of the packaging shell is <0.05 g / (m²). 2 24h); and / or, the interfacial gap between the positive electrode, the composite solid electrolyte layer and the negative electrode is <1μm.

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