All-solid-state battery pole piece and preparation method thereof, battery cell and all-solid-state battery

Abstract

The invention relates to the technical field of all-solid-state batteries, in particular to an all-solid-state battery pole piece, a preparation method of the all-solid-state battery pole piece, a battery cell and an all-solid-state battery. The all-solid-state battery pole piece contains fibrous solid electrolyte. The all-solid-state battery pole piece provided by the invention contains the fibrous solid electrolyte, so that the processing pressure of the pole piece and the battery is effectively reduced, and the ionic conductivity is improved; meanwhile, the battery containing the all-solid-state battery pole piece also has relatively high energy density, structural stability and cycle performance.

Description

Technical Field

[0001] This invention relates to the field of all-solid-state battery technology, specifically to an all-solid-state battery electrode, a method for preparing an all-solid-state battery electrode, a battery cell, and an all-solid-state battery. Background Technology

[0002] Compared to traditional liquid batteries, all-solid-state batteries have great potential in balancing high safety and high energy density, making them a research hotspot. Current all-solid-state battery manufacturing methods involve solid-solid contacts, requiring extremely high pressing pressures on the electrodes to ensure sufficient contact between solid electrolyte particles, active material particles, and conductive agents, thereby improving the transport capacity of lithium ions and electrons between particles. For example, in sulfide all-solid-state systems, the positive electrode needs to be pressed at ≥200MPa to achieve good density, sometimes even requiring isostatic pressing devices (applying 400-550MPa), resulting in high cost and low efficiency. Furthermore, a large amount of conductive carbon and active particles are separated / encapsulated by the solid electrolyte particles, preventing many conductive carbon particles from simultaneously contacting two or more active material particles, thus affecting electron transport between active materials. In addition, stress exists during charging and discharging, and the dense, non-porous electrode sheets cannot release this stress, making them prone to cracking. The solid electrolyte particles used in all-solid-state batteries are relatively large, making it difficult to increase the proportion of active material to a high level. For example, the proportion of active material in sulfide all-solid-state electrode sheets (especially positive electrode sheets) reported in the industry is generally low (generally ≤85%). In addition, sulfide electrolytes have a high density. Therefore, when choosing the same positive and negative electrode material system, the energy density of sulfide all-solid-state batteries is much lower than that of liquid batteries.

[0003] CN111276690A discloses a low-porosity positive electrode sheet, which consists of an active material particle, a conductive agent, a coating composed of a binder with lithium-ion conductivity, and a current collector. The binder is composed of a polymer, lithium salt, ionic liquid, and inorganic lithium-ion conductor. This positive electrode sheet uses a specific binder and conductive agent to form ion and electron transport channels, improving the electrode sheet's conductivity. However, this method contains liquid components such as ionic liquids, which can undergo side reactions with solid electrolytes such as sulfides and halides with high ionic conductivity. Therefore, the electrode sheet prepared by this method has relatively low overall ionic conductivity and performance. Summary of the Invention

[0004] The purpose of this invention is to solve the above-mentioned problems and provide an all-solid-state battery electrode, a method for preparing an all-solid-state battery electrode, a battery cell, and an all-solid-state battery. The all-solid-state battery electrode contains a fibrous solid electrolyte, which effectively improves the ionic conductivity. At the same time, the battery containing the all-solid-state battery electrode also has high energy density, structural stability, and cycle performance.

[0005] To achieve the above objectives, the first aspect of the present invention provides an all-solid-state battery electrode, wherein the all-solid-state battery electrode contains a fibrous solid electrolyte.

[0006] Preferably, the fibrous solid electrolyte has a Push's ratio ≥ 1.6, more preferably 1.7-6.5. The Push's ratio, used to evaluate the ductility and brittleness of a material, is the ratio of bulk modulus (B) to shear modulus (G), B / G.

[0007] Preferably, the shear modulus of the fibrous solid electrolyte is ≤30 GPa, and more preferably 0.5-20 GPa.

[0008] Preferably, the fibrous solid electrolyte has a room temperature ionic conductivity ≥10. -4 S / cm, preferably ≥5×10 -4 S / cm, more preferably ≥10 -3 S / cm. In this invention, room temperature refers to 25±2℃.

[0009] Preferably, the average length of the fibrous solid electrolyte is 1-5000 μm, more preferably 2-2000 μm.

[0010] Preferably, the average diameter of the fibrous solid electrolyte is ≤1μm, and more preferably 5-500nm.

[0011] Preferably, based on the total weight of the effective components in the all-solid-state battery electrode, the content of the fibrous solid electrolyte is 0.1-20 wt%, more preferably 3-15 wt%.

[0012] Preferably, based on the total weight of the effective components in the all-solid-state battery electrode, the content of the active material is ≥70wt%, preferably 85-95wt%.

[0013] A second aspect of the present invention provides a method for preparing an all-solid-state battery electrode, the method comprising:

[0014] A slurry containing a fibrous solid electrolyte and a solvent is coated onto a current collector and then dried and pressed; alternatively, a solvent-free mixture containing a fibrous solid electrolyte is coated onto a current collector and then pressed.

[0015] All-solid-state battery electrodes were obtained.

[0016] A third aspect of the present invention provides a battery cell comprising: a positive electrode, a negative electrode, and an electrolyte layer; wherein the positive electrode and / or the negative electrode are each independently selected from the all-solid-state battery electrode provided in the first aspect, or from the all-solid-state battery electrode prepared by the preparation method provided in the second aspect.

[0017] A fourth aspect of the present invention provides an all-solid-state battery, the all-solid-state battery comprising at least one cell provided in a third aspect, which is arranged in a stacked or wound configuration.

[0018] Compared with the prior art, the present invention has the following advantages:

[0019] (1) The all-solid-state battery electrode provided by the present invention adopts a fibrous solid electrolyte, which not only achieves full contact between the conductive agent and the active material, but also, by controlling the physical properties of the fibrous solid electrolyte, especially the average length, average diameter and ionic conductivity, the conductive agent can simultaneously and fully contact multiple active material particles. Furthermore, a three-dimensional conductive network structure of "active material-conductive agent-fibrous solid electrolyte" is constructed to promote electron / ion transport within the electrode and ensure high ionic conductivity and high electronic conductivity.

[0020] (2) The all-solid-state battery electrode provided by the present invention has a specific pore structure, which effectively releases stress and reduces the electrode expansion rate during the electrode processing stage or during battery charging and discharging, avoids cracks in the electrode, and thus improves structural stability.

[0021] (3) The all-solid-state battery electrode provided by the present invention further optimizes the ionic conductivity and pore structure of the all-solid-state battery electrode by adjusting the compounding of fibrous solid electrolyte and particulate solid electrolyte; at the same time, by adjusting the content ratio of active material and coating modification, the ionic conductivity and energy density of the all-solid-state battery electrode are further optimized.

[0022] (4) The preparation method provided by the present invention uses wet coating or dry coating to ensure that the porosity and pore size of the all-solid-state battery electrode are controlled under the premise of high ionic conductivity; at the same time, the preparation method requires less pressing pressure, has a wide range of equipment selection, simplifies the process flow, and is convenient for industrial production.

[0023] (5) When the all-solid-state battery electrode provided by the present invention is used in an all-solid-state battery, the electrode stress is released in time during processing and cycling, thereby reducing electrode cracking, electrode and battery expansion, especially reducing the amount of electrolyte used in the electrode, and improving energy density, structural stability and electrochemical performance (such as cycle performance). Detailed Implementation

[0024] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0025] The first aspect of the present invention provides an all-solid-state battery electrode, wherein the all-solid-state battery electrode contains a fibrous solid electrolyte.

[0026] In this invention, unless otherwise specified, the all-solid-state battery electrode includes not only the all-solid-state battery positive electrode but also the all-solid-state battery negative electrode, which mainly depends on the type of active material.

[0027] In this invention, unless otherwise specified, fibrous solid electrolyte refers to an electrolyte that not only satisfies the solid form but also has a fibrous structure.

[0028] The push ratio is used to evaluate the ductility and brittleness of a material. It is the ratio of bulk modulus (B) to shear modulus (G), B / G.

[0029] In some embodiments of the present invention, preferably, the Push's ratio of the fibrous solid electrolyte is ≥1.6, for example, 1.6, 1.65, 1.7, 1.75, 2, 2.5, 3, 3.5, 4, 4.5, 5, 5.5, 6, 6.5, and any value within the range of any two values, preferably 1.7-6.5.

[0030] In some embodiments of the present invention, preferably, the shear modulus of the fibrous solid electrolyte is ≤30 GPa, more preferably 0.5-20 GPa, for example, 0.5 GPa, 0.8 GPa, 1 GPa, 2 GPa, 3 GPa, 4 GPa, 5 GPa, 6 GPa, 7 GPa, 8 GPa, 9 GPa, 10 GPa, 11 GPa, 12 GPa, 15 GPa, 20 GPa, 25 GPa, and any value within any range of any two values.

[0031] In this invention, unless otherwise specified, Push's specificity and shear modulus parameters are obtained using GB / T7962.6-2010. Although GB / T 7962.6-2010 is a test method for colorless glass, colorless glass is actually a rigid inorganic non-metallic material, similar to ceramic materials. Sulfide nanofibers can only be observed at the microscopic level; their macroscopic morphology is still that of ceramic powder. Furthermore, due to their good plasticity, they can be pressed into the block shape required by national standards for testing.

[0032] The specific test conditions include: applying a pressure of 360 MPa through a square mold to press the fibrous solid electrolyte into a block with dimensions of 22 mm × 22 mm × 120 mm, finely grinding both ends with a parallelism difference of no more than 0.02 mm and a roughness Ra = 0.1, and then testing the Push's specific parameter and shear modulus parameter of the above-mentioned fibrous solid electrolyte according to GB / T 7962.6-2010.

[0033] During electrode pressing, the fibrous solid electrolyte exhibits certain plastic or elastic deformation. Using relatively low pressing pressure, it can easily form good three-dimensional ion transport channels between the active material particles. When the electrode expands and contracts, it more readily adapts to volume changes, maintaining good contact with the active particles even after long-term cycling. Therefore, it is preferable to have a Push's ratio and shear modulus within the aforementioned range. The fibrous solid electrolyte is flexible, easily bent without breaking, and more easily allows for contact between the fibrous solid electrolyte and more active material particles.

[0034] In some embodiments of the present invention, preferably, the fibrous solid electrolyte has a room temperature ionic conductivity ≥10. -4 S / cm, for example, 1×10 -4 S / cm, 2×10 -4 S / cm, 3×10 -4 S / cm, 4×10 -4 S / cm, 5×10 -4 S / cm, 6×10 -4 S / cm, 7×10 -4 S / cm, 8×10 -4 S / cm, 9×10 -4 S / cm, 1×10 -3 S / cm, 2×10 -3 S / cm, 3×10 -4 S / cm, 4×10 -4 S / cm, 5×10 -3 S / cm, 6×10 -3 S / cm, 7×10 -4 S / cm, 8×10 -3 S / cm, 9×10 -4 S / cm, 10×10 -3 S / cm, and any value within a range of any two values, preferably ≥5×10 -4 S / cm, more preferably ≥10 -3 S / cm. Meeting the above-mentioned preferred range conditions is more conducive to improving the ionic conductivity of the all-solid-state battery electrode.

[0035] In this invention, unless otherwise specified, the ionic conductivity parameter is measured using the AC impedance method. The specific test includes: clamping the sample between two stainless steel disc electrodes (SS), measuring the ionic conductivity (σ) using electrochemical impedance spectroscopy (EIS) within a frequency range of 1 Hz to 7 MHz with an AC amplitude of 10 mV, and applying the formula σ = L / (R). b The calculation is performed using ×S); where R b The volume resistivity (R) of the sample to be tested b (Determined by impedance spectroscopy), where L and S are the thickness and area of ​​the sample to be tested.

[0036] In some embodiments of the present invention, preferably, the average length of the fibrous solid electrolyte is 1-5000 μm, for example, 1 μm, 2 μm, 3 μm, 4 μm, 5 μm, 10 μm, 20 μm, 30 μm, 40 μm, 50 μm, 60 μm, 70 μm, 80 μm, 90 μm, 100 μm, 150 μm, 200 μm, 250 μm, 300 μm, 350 μm, 400 μm, 450 μm, 500 μm, 600 μm, 1000 μm, 1500 μm, 2000 μm, 3000 μm, 4000 μm, 5000 μm, and any value within any range of any two values, preferably 2-2000 μm, more preferably 10-500 μm.

[0037] In some embodiments of the present invention, more preferably, the average diameter of the fibrous solid electrolyzer is ≤1μm, for example, 1nm, 5nm, 10nm, 20nm, 50nm, 80nm, 100nm, 150nm, 200nm, 250nm, 300nm, 350nm, 400nm, 450nm, 500nm, 600nm, 800nm, 1μm, and any value within the range of any two values, preferably 5-500nm.

[0038] In some embodiments of the present invention, more preferably, the aspect ratio of the fibrous solid electrolyte is ≥5, for example, 5, 10, 20, 50, 80, 100, 150, 200, 500, 800, 1000, 1500, 2000, 3000, 4000, 5000, 8000, 10000, 15000, 20000, 25000, 30000, 35000, 40000, 50000, 60000, and any value within any range of two such values, preferably 5-50000, more preferably 5-5000. In the present invention, the aspect ratio refers to the ratio of the average length to the average diameter of the fibrous solid electrolyte.

[0039] In this invention, the advantageous fiber shape can promote the formation of a three-dimensional ion transport network and a three-dimensional electron transport network between the fibrous solid electrolyte and the conductive agent, respectively, which is more conducive to improving the ion conduction and electron conduction of the all-solid-state battery electrode.

[0040] In this invention, unless otherwise specified, the average length parameter, average diameter parameter, and particle size parameters (D50, D90) are all measured using a scanning electron microscope (SEM). Twenty fibers or twenty particles are randomly selected at 5k magnification, and their average length, diameter, and particle size are taken.

[0041] In some embodiments of the present invention, preferably, based on the total weight of the effective components in the all-solid-state battery electrode, the content of the fibrous solid electrolyte is 0.1-20 wt%, for example, 0.1 wt%, 0.5 wt%, 1 wt%, 2 wt%, 3 wt%, 5 wt%, 8 wt%, 10 wt%, 12 wt%, 15 wt%, 18 wt%, 20 wt%, and any value within any range of any two values, preferably 3-15 wt%.

[0042] In this invention, unless otherwise specified, the total weight of the effective components in the all-solid-state battery electrode refers to the sum of the weights of the fibrous solid electrolyte, conductive agent, active material, binder, and optionally particulate solid electrolyte in the all-solid-state battery electrode.

[0043] In this invention, a wide range of types of fibrous solid electrolytes can be selected, as long as the above-mentioned parameters are met. Preferably, the electrolyte material of the fibrous solid electrolyte is selected from at least one of sulfide electrolytes, sulfur oxide electrolytes, halide electrolytes, halide oxide electrolytes, oxide electrolytes, and polymer electrolytes; more preferably, it is selected from at least one of sulfide electrolytes, sulfur oxide electrolytes, halide electrolytes, and halide oxide electrolytes.

[0044] In some specific embodiments of the present invention, the sulfide solid electrolyte includes, but is not limited to, xLi₂S·(100-x)P₂S₅ (0≤x≤100), Li₃PS₄, and Li₇P₃S. 11 , Li6PS5X (X=Cl, Br, I), Li 10 MP2S 12 (M = Ge, Sn, Si), Li 3.25 Ge 0.25 P 0.75 S4, Li 10 GeP2S 12 Li 9.54 Si 1.74 P 1.44 S11.7 Cl 0.3 Li4GeS4, Li 11 Sn2PS 12 And mixtures, coatings, derivatives, etc. of the aforementioned substances.

[0045] In some specific embodiments of the present invention, the oxide solid electrolyte includes, but is not limited to, lithium lanthanum titanate (LLTO), lithium lanthanum zirconate (LLZO), lithium titanium aluminum phosphate (LATP), lithium germanium aluminum phosphate (LAGP), and lithium zirconium silicon phosphorus oxide (Li3Zr2Si2PO4). 12 Lithium lanthanum phosphate (LiLaPO4), etc.

[0046] In some specific embodiments of the present invention, the polymer electrolyte includes, but is not limited to, polyethylene oxide electrolyte (PEO / LiTFSI, wherein the weight-average molecular weight of PEO is Mw = 100,000) and polyethylene glycol diacrylate electrolyte (PEGDA / LiTFSI, wherein the weight-average molecular weight of PEGDA is Mw = 500,000). In the present invention, the polymer electrolyte cannot be used alone and needs to be used in combination with lithium salt.

[0047] In this invention, the source of the fibrous solid electrolyte has a wide range of options; it can be obtained commercially or prepared. Preferably, the fibrous solid electrolyte is prepared from finished electrolyte products or electrolyte raw materials through methods such as air-jet spinning, electrospinning, and phase separation.

[0048] In some embodiments of the present invention, preferably, the all-solid-state battery electrode also contains a particulate solid electrolyte. This configuration, through the combined effect of the fibrous solid electrolyte and the particulate solid electrolyte, optimizes the three-dimensional ion network of the electrode, enhances the ion transport path of the electrode, and optimizes the electrical performance of the battery (such as cycle performance and rate performance).

[0049] In this invention, unless otherwise specified, the fibrous solid electrolyte and the particulate solid electrolyte define the morphology / structure of the solid electrolyte, but do not limit the type of electrolyte material; the electrolyte materials of the fibrous solid electrolyte and the particulate solid electrolyte can be the same or different, but are preferably the same.

[0050] In some embodiments of the present invention, preferably, the D50 particle size of the particulate solid electrolyte is ≤ the average diameter of the fibrous solid electrolyte.

[0051] In some embodiments of the present invention, more preferably, the D50 particle size of the particulate solid electrolyte is 200nm-10μm, for example, 200nm, 300nm, 500nm, 800nm, 1μm, 1.5μm, 2μm, 5μm, 8μm, 10μm, and any value in the range of any two values, preferably 200nm-5μm.

[0052] In some embodiments of the present invention, preferably, the mass ratio of the fibrous solid electrolyte to the particulate solid electrolyte is 0.1-10:1, for example, 0.1:1, 0.3:1, 0.5:1, 0.8:1, 1:1, 2:1, 3:1, 4:1, 5:1, 6:1, 7:1, 8:1, 9:1, 10:1, and any value within any range of two such values, preferably 1-5:1. A mass ratio satisfying the above range optimizes the contact points between the solid electrolyte and the active material particles, as well as the expansion and contraction rate of the solid electrolyte, thereby reducing the pressing pressure on the electrode and improving the structural stability of the electrode.

[0053] In some embodiments of the present invention, preferably, the all-solid-state battery electrode further contains an active material, which is selected from positive electrode active materials or negative electrode active materials. In the present invention, when the active material is selected from positive electrode active materials, the all-solid-state battery electrode is a positive electrode; or, when the active material is selected from negative electrode active materials, the all-solid-state battery electrode is a negative electrode.

[0054] In this invention, a fibrous solid electrolyte is used, which can effectively increase the content of active materials, thereby increasing the energy density of the battery. Preferably, based on the total weight of the effective components in the all-solid-state battery electrode, the content of the active material is ≥70wt%, for example, 70wt%, 80wt%, 81wt%, 82wt%, 83wt%, 84wt%, 85wt%, 86wt%, 87wt%, 88wt%, 89wt%, 90wt%, 91wt%, 92wt%, 93wt%, 94wt%, 95wt%, and any value within any range of any two values, preferably 85-95wt%.

[0055] In some embodiments of the present invention, preferably, when the active material is a positive electrode active material, the positive electrode active material is selected from lithium-ion positive electrode materials, sodium-ion positive electrode materials, and more preferably from at least one of lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminum oxide, lithium cobalt oxide, lithium nickel oxide, lithium lithium-rich manganese, lithium manganese oxide, lithium iron phosphate, lithium iron manganese phosphate, iron sulfide, copper sulfide, titanium sulfide, sodium manganate, sodium cobalt oxide, sodium nickel oxide, sodium iron phosphate, sodium iron manganese phosphate, Prussian blue, and derivatives of the above materials after doping.

[0056] In some embodiments of the present invention, preferably, when the active material is a negative electrode active material, the negative electrode active material is selected from graphite, elemental silicon, and SiO2. x (0<x≤2), at least one of Si / C, Sn, P, lithium titanate / sodium, and titanium niobate.

[0057] In this invention, to accelerate fast ion transport on the surface, preferably, the surface of the active material is provided with a coating layer, the coating layer being selected from fast ion conductors and / or electronic conductors. In this invention, the surface of the active material in the positive electrode and / or negative electrode is provided with a coating layer, the coating layer being selected from fast ion conductors and / or electronic conductors;

[0058] In this invention, compared to coating a fast ion conductor or coating an electronic conductor alone, coating both a fast ion conductor and an electronic conductor simultaneously is more beneficial for improving the conductivity of the electrode.

[0059] In some embodiments of the present invention, preferably, the fast ion conductor is selected from at least one of sulfide electrolytes, sulfur oxide electrolytes, halide electrolytes, halide oxide electrolytes, and oxide electrolytes.

[0060] In this invention, the fast ion conductor and the solid electrolyte can be made of the same or different materials. The fast ion conductor is generally a particle, but with a small particle size, or it may be dissolved in a solvent during the coating process.

[0061] In some embodiments of the present invention, preferably, the electronic conductor is selected from at least one of conductive carbon black (Super P), acetylene black, Ketjen black, carbon nanofiber (VGCF), carbon nanotubes, carbon nanowires, carbon nanosheets, and graphene. In the present invention, the types of electronic conductors and conductive agents can be the same or different.

[0062] In some embodiments of the present invention, preferably, the thickness of the coating layer is 1 nm-5 μm, for example, 1 nm, 5 nm, 10 nm, 50 nm, 100 nm, 200 nm, 500 nm, 800 nm, 1 μm, 1.5 μm, 2 μm, 5 μm, and any value within the range of any two values, preferably 5-500 nm. In the present invention, the thickness parameter is measured using a scanning electron microscope (SEM).

[0063] In some embodiments of the present invention, the all-solid-state battery electrode further contains a conductive agent; more preferably, based on the total weight of the effective components in the all-solid-state battery electrode, the content of the conductive agent is ≤5wt%, for example, 0.1wt%, 0.5wt%, 1wt%, 2wt%, 3wt%, 5wt%, and any value in any range of any two values, preferably 0.5-3wt%.

[0064] In some embodiments of the present invention, preferably, the conductive agent is selected from at least one of conductive carbon black, carbon fiber, carbon nanotubes, acetylene black, Ketjen black, graphite and graphene.

[0065] In some embodiments of the present invention, the all-solid-state battery electrode further contains a binder; more preferably, based on the total weight of the effective components in the all-solid-state battery electrode, the content of the binder is ≤10wt%, for example, 0.1wt%, 0.5wt%, 1wt%, 2wt%, 3wt%, 5wt%, 8wt%, 10wt%, and any value within any range of any two values, preferably 0.5-5wt%.

[0066] In some embodiments of the present invention, preferably, the adhesive is selected from at least one of polyvinylidene fluoride (PVDF), styrene-butadiene rubber (SBR), carboxymethyl cellulose (CMC), polytetrafluoroethylene (PTFE), nitrile rubber (NBR), polyacrylonitrile (PAN), polyacrylic acid (PAA), and polyacrylate. In the present invention, polyacrylate includes, but is not limited to, polymethyl acrylate, polyethyl acrylate, and polypropyl acrylate.

[0067] In this invention, unless otherwise specified, the effective components of the all-solid-state battery electrode include fibrous solid electrolyte, particulate solid electrolyte, active material, conductive agent, and binder, as well as other components. Preferably, the effective components of the all-solid-state battery electrode consist of fibrous solid electrolyte, optional particulate solid electrolyte, active material, conductive agent, and binder.

[0068] In this invention, unless otherwise specified, the all-solid-state battery electrode also contains a current collector, which includes, but is not limited to, copper foil, aluminum foil, etc.

[0069] In a first embodiment of the present invention, the positive electrode sheet of the all-solid-state battery includes an aluminum foil and a positive electrode coating disposed on the aluminum foil, wherein the positive electrode coating contains a fibrous solid electrolyte, a positive electrode active material, a conductive agent, a binder, and optionally a particulate solid electrolyte.

[0070] In a second embodiment of the present invention, the all-solid-state battery negative electrode sheet includes a copper foil and a negative electrode coating disposed on the copper foil, wherein the negative electrode coating contains a fibrous solid electrolyte, a negative electrode active material, a conductive agent, a binder, and optionally a particulate solid electrolyte.

[0071] In some embodiments of the present invention, preferably, the porosity of the all-solid-state battery electrode is 0-30%, for example, 0%, 0.1%, 0.5%, 1%, 2%, 5%, 8%, 10%, 15%, 20%, 25%, 30%, and any value within the range of any two values, preferably 2-20%, more preferably 2-10%.

[0072] In this invention, a porosity within the above-mentioned range not only allows for the use of lower pressure to press the electrode sheet, ensuring electrical connection without requiring excessive pressure during cycling, but also provides space for stress release during processing and cycling, reduces electrode sheet cracking, reduces electrode sheet and battery expansion, and reduces electrolyte usage, thereby increasing energy density.

[0073] In this invention, unless otherwise specified, the porosity of the all-solid-state battery electrode is defined as (true density of the mixture - compacted density of the electrode) / true density of the mixture × 100%, where the true density of the mixture = true density of each component × mass fraction. For example, the electrode contains 95 wt% ternary material, 3 wt% conductive agent, and 2 wt% binder, and the true density of the ternary material is 4.8 g / cm³. 3 The true density of the conductive agent is 1.9 g / cm³. 3 The true density of the PVDF adhesive is 1.78 g / cm³. 3 Therefore, the true density of the mixture = 4.8 × 95% + 1.9 × 3% + 1.78 × 2 = 4.65 g / cm³ 3 Electrode compaction density = weight of the compacted electrode (g) / volume of the electrode (cm³) 3 ).

[0074] In some embodiments of the present invention, preferably, the median pore size of the all-solid-state battery electrode is 10nm-10μm, for example, 10nm, 20nm, 50nm, 100nm, 200nm, 500nm, 800nm, 1μm, 1.5μm, 2μm, 5μm, 8μm, 10μm, and any value within the range of any two values, preferably 10nm-2μm.

[0075] In this invention, the pore size of the all-solid-state battery electrode refers to the average diameter of the pores on the surface and / or inside the electrode; the median pore size parameter is measured using the nitrogen adsorption method (BET).

[0076] In some embodiments of the present invention, preferably, the ionic conductivity of the all-solid-state battery electrode is ≥1×10⁻⁶. -7 S / cm, for example, 1×10 -7 S / cm, 2×10 -7 S / cm, 5×10 -7 S / cm, 1×10-6 S / cm, 2×10 -6 S / cm, 5×10 - 6 S / cm, 1×10 -5 S / cm, 2×10 -5 S / cm, 5×10 -5 S / cm, 8×10 -5 S / cm, 1×10 -4 S / cm, 2×10 -4 S / cm, 5×10 -4 S / cm, 8×10 -4 S / cm, 1×10 -3 S / cm, and any value within a range of any two values, preferably ≥1×10 -6 S / cm.

[0077] A second aspect of the present invention provides a method for preparing an all-solid-state battery electrode, the method comprising:

[0078] A slurry containing a fibrous solid electrolyte and a solvent is coated onto a current collector and then dried and pressed; alternatively, a solvent-free mixture containing a fibrous solid electrolyte is coated onto a current collector and then pressed.

[0079] All-solid-state battery electrodes were obtained.

[0080] The inventors of this invention have discovered that by applying a fibrous solid electrolyte to a current collector using a wet or dry method and then pressing it, the fibrous solid electrolyte effectively and fully covers the surface of multiple active material particles and / or fills the spaces between them, promoting ion / electron transport within the electrode and thus improving the ionic conductivity of the electrode. Simultaneously, by controlling the pressing pressure range, the pore structure of the electrode can be controlled, thereby optimizing the structural stability and expansion rate of the electrode.

[0081] In some embodiments of the present invention, the pressing pressure is 0.1-200 MPa, for example, 200 MPa, 150 MPa, 100 MPa, 80 MPa, 60 MPa, 50 MPa, 40 MPa, 30 MPa, 20 MPa, 18 MPa, 15 MPa, 10 MPa, 5 MPa, 2 MPa, 1 MPa, 0.1 MPa, and any value within the range of any two values, preferably 0.1-100 MPa, more preferably ≤80 MPa, more preferably 10-80 MPa, and most preferably 15-50 MPa.

[0082] In this invention, the pressing method has a wide range of options, as long as the pressing pressure meets the above-mentioned limitations. Preferably, the pressing method includes, but is not limited to, isostatic pressing, roller pressing, flat pressing, etc.

[0083] In some embodiments of the present invention, preferably, the solvent in the mixed slurry is selected from NMP, tetrahydrofuran, benzene, toluene, xylene, dichloromethane, pentane, hexane, heptane, octane, ethyl acetate, ethyl butyrate, butyl butyrate, acetone, N,N-dimethylbutylamine, isopropyl ether, dibutyl ether, propylene oxide, acetonitrile, anhydrous ethanol, isopropanol, 1,2-ethylenediamine (EDA), 1,2-ethylenedithiol (EDT), etc.

[0084] In some embodiments of the present invention, preferably, the mixed slurry and the mixture each independently contain an active substance, a conductive agent and a binder; more preferably, the mixed slurry and the mixture each independently contain a particulate solid electrolyte.

[0085] In this invention, unless otherwise specified, the physical properties and types of the fibrous solid electrolyte, particulate solid electrolyte, active material, conductive agent, and binder are all as defined above, and will not be elaborated further in this invention.

[0086] In one specific embodiment of the present invention, the preparation method includes: (1) mixing fibrous solid electrolyte, active material, conductive agent, binder, optional particulate solid electrolyte and solvent to obtain a mixed slurry; (2) wet coating the mixed slurry onto a current collector and drying and pressing it to obtain the all-solid-state battery electrode.

[0087] In another specific embodiment of the present invention, the preparation method includes: (1') mixing fibrous solid electrolyte, active material, conductive agent, binder and optional particulate solid electrolyte to obtain a mixture; (2') dry coating the mixture onto a current collector and pressing it to obtain the all-solid-state battery electrode.

[0088] In this invention, there is no limitation on wet coating and dry coating, as long as the mixed slurry and the mixture are uniformly coated on the current collector.

[0089] In this invention, the drying process aims to remove solvent from the mixed slurry. Preferably, the drying conditions are: a temperature of 80-150°C and a time of 0.1-20 hours.

[0090] A third aspect of the present invention provides a battery cell comprising: a positive electrode, a negative electrode, and an electrolyte layer; wherein the positive electrode and / or the negative electrode are each independently selected from the all-solid-state battery electrode provided in the first aspect, or from the all-solid-state battery electrode prepared by the preparation method provided in the second aspect.

[0091] In this invention, preferably, the electrolyte layer is selected from at least one of sulfide electrolytes, sulfur oxide electrolytes, halide electrolytes, halide oxide electrolytes, oxide electrolytes, and polymer electrolytes. In this invention, the type of electrolyte layer may be the same as or different from the type of fibrous solid electrolyte particles in the all-solid-state battery electrode.

[0092] In some embodiments of the present invention, preferably, the restraint pressure of the all-solid-state battery is 0.1-100 MPa, for example, 0.1 MPa, 0.5 MPa, 0.8 MPa, 1 MPa, 2 MPa, 3 MPa, 4 MPa, 5 MPa, 10 MPa, 15 MPa, 20 MPa, 25 MPa, 30 MPa, 50 MPa, 80 MPa, 100 MPa, and any value within any range of any two values, preferably 0.5-20 MPa.

[0093] A fourth aspect of the present invention provides an all-solid-state battery, the all-solid-state battery comprising at least one cell provided in a third aspect, which is arranged in a stacked or wound configuration.

[0094] The present invention will be described in detail below through embodiments.

[0095] Preparation Example 1

[0096] (1) Dissolve 0.1g of ethylene-vinyl acetate copolymer (EVA, vinyl acetate content 40wt%, weight average molecular weight 20000g / mol) in 10mL of organic solvent THF. After complete dissolution, add 1g of solid electrolyte raw material (Li2S:LiCl:P2S5=2.5:1:0.5, molar ratio) to obtain a precursor solution with a viscosity of 400cp.

[0097] (2) Use a pipette to transfer the above precursor solution to the syringe pump, install the needle, connect the needle to the positive electrode, connect the receiving plate to the negative electrode, the positive and negative electrode voltages are 12kV and -1kV respectively, the distance between the needle and the receiving plate is 15cm, the injection speed is 1mL / h, after setting the corresponding program, start electrospinning to obtain the nanofiber precursor.

[0098] (3) The above nanofiber precursor was introduced into a ceramic boat and then transferred to a tube furnace for heat treatment under an argon atmosphere. The tube furnace was heated from 25°C to 550°C at a heating rate of 10°C / min. After holding at the temperature for 2 hours, it was naturally cooled down to obtain fibrous solid electrolyte P1.

[0099] Preparation Example 2

[0100] The method used in Preparation Example 1 is different,

[0101] In step (1), the raw material is Li7P3S 7.5 O 3.5 The ratio of Li₂O to P₂S₅ is 3.5 to 1.5, in molar ratio.

[0102] Under the same conditions, fibrous solid electrolyte P2 was obtained.

[0103] Preparation Example 3

[0104] The method used in Preparation Example 1 is different,

[0105] In step (1), the raw material is 1g of mixed polymer electrolyte + lithium salt raw material PEGDA:LiTFSI = 2:1 (mass ratio), dissolved in 10mL of NMP and mixed thoroughly; wherein, the weight average molecular weight of PEGDA Mw = 500,000;

[0106] In step (3), no heat treatment was performed; the above nanofiber precursor was directly placed in a drying device and dried at 80°C for 4 hours.

[0107] Under the same conditions, fibrous solid electrolyte fiber P3 was obtained.

[0108] Preparation Example 4

[0109] The method used in Preparation Example 1 is different,

[0110] In step (2), the conditions for electrospinning are replaced with a liquid injection rate of 4 mL / h and a positive electrode voltage of 30 kV;

[0111] Under the same conditions, fibrous solid electrolyte P4 was obtained.

[0112] Preparation Example 5

[0113] The method used in Preparation Example 1 is different,

[0114] In step (1), the amount of EVA was replaced with 0.5g, resulting in a precursor solution with a viscosity of 2000cp;

[0115] Under the same conditions, fibrous solid electrolyte P5 was obtained.

[0116] Example 1

[0117] (1) The modified positive electrode active material, fibrous solid electrolyte P1, conductive agent (conductive carbon black), binder (PVDF) and solvent (xylene) are mixed to obtain a mixed slurry with a solid content of 70wt%.

[0118] The modified positive electrode active material includes a positive electrode active material (NCM(Ni90), with an average particle size of 7 μm) and a coating layer (LPSC, with a thickness of 20 nm).

[0119] The fibrous solid electrolyte P1 has the composition Li6PS5Cl, a Push's ratio of 1.75, a shear modulus of 8 GPa, and an ionic conductivity of 1 × 10⁻⁶ at 25 °C. -2 S / cm, average length is 62μm, average diameter is 290nm;

[0120] The mass ratio of the modified positive electrode active material, the fibrous solid electrolyte P1, the conductive agent and the binder is 85:10:2:3.

[0121] (2) The above mixed slurry is coated on aluminum foil and dried at 100°C for 5 hours. Then it is pressed at a pressure of 30 MPa to obtain the positive electrode sheet S1 of the all-solid-state battery.

[0122] Example 2

[0123] The method is the same as in Example 1, except that...

[0124] In step (1), the fibrous solid electrolyte P1 is replaced with fibrous solid electrolyte P2, the composition of which is Li7P3S. 7.5 O 3.5 The Push's ratio is 1.65, the shear modulus is 12 GPa, and the ionic conductivity at 25℃ is 5 × 10⁻⁶. -4 S / cm, with a length of 60μm and a diameter of 297nm.

[0125] Under the same conditions, the positive electrode of the all-solid-state battery, S2, is obtained.

[0126] Example 3

[0127] The method is the same as in Example 1, except that...

[0128] In step (1), the fibrous solid electrolyte P1 is replaced with fibrous solid electrolyte P3. The fibrous solid electrolyte P3 has the composition of PEGDA / LiTFSI, a Push's ratio of 5.5, a shear modulus of 0.8 GPa, and an ionic conductivity of 1×10 at 25°C. -4S / cm, length 61μm, diameter 300nm.

[0129] Under the same conditions, the positive electrode of the all-solid-state battery, S3, was obtained.

[0130] Example 4

[0131] The method is the same as in Example 1, except that...

[0132] In step (1), the fibrous solid electrolyte P1 is replaced with fibrous solid electrolyte P4. The fibrous solid electrolyte P4 has the composition Li6PS5Cl, a Push's ratio of 1.75, a shear modulus of 8 GPa, and an ionic conductivity of 1×10⁻⁶ at 25 °C. - 2 The S / cm value has an average length of 5μm and an average diameter of 288nm.

[0133] Under the same conditions, the positive electrode of the all-solid-state battery, S4, was obtained.

[0134] Example 5

[0135] The method is the same as in Example 1, except that...

[0136] In step (1), the fibrous solid electrolyte P1 is replaced with fibrous solid electrolyte P5. The fibrous solid electrolyte P5 has the composition Li6PS5Cl, a Push's ratio of 1.75, a shear modulus of 8 GPa, and an ionic conductivity of 1×10⁻⁶ at 25°C. - 2 The S / cm has an average length of 620μm and an average diameter of 290nm.

[0137] Under the same conditions, the positive electrode of the all-solid-state battery, S5, was obtained.

[0138] Example 6

[0139] The method is the same as in Example 1, except that...

[0140] In step (1), a particulate solid electrolyte (LPSC, with a particle size of 2 μm) is also added, and the weight ratio of the fibrous solid electrolyte to the particulate solid electrolyte is 3:1.

[0141] The mass ratio of the modified positive electrode active material, fibrous solid electrolyte, particulate solid electrolyte, conductive agent and binder is 85:7.5:2.5:2:3.

[0142] In step (2), the pressing pressure is replaced with 18 MPa;

[0143] Under the same conditions, the positive electrode of the all-solid-state battery, S6, was obtained.

[0144] Example 7

[0145] The method is the same as in Example 1, except that...

[0146] In step (1), the positive electrode active material does not contain a coating layer, that is, the mass ratio of the above positive electrode active material, fibrous solid electrolyte P1, conductive agent and binder is 85:10:2:3;

[0147] Under the same conditions, the positive electrode of the all-solid-state battery, S7, was obtained.

[0148] Example 8

[0149] (1) The modified negative electrode active material, fibrous solid electrolyte P1, conductive agent (conductive carbon black) and binder (PVDF) are mixed to obtain a mixture.

[0150] The modified negative electrode active material includes a negative electrode active material (graphite with an average particle size of 20 μm) and a coating layer (LPSC with a thickness of 20 nm).

[0151] The mass ratio of the modified negative electrode active material, fibrous solid electrolyte, conductive agent and binder is 85:10:2:3.

[0152] (2) The above mixture is coated on copper foil and pressed at a pressure of 30MPa to obtain the all-solid-state battery negative electrode S8.

[0153] Comparative Example 1

[0154] The method is the same as in Example 1, except that...

[0155] In step (1), the positive electrode active material (NCM(Ni90), particulate solid electrolyte (LPSC, with an average particle size of 7 μm and a particle size of 2 μm), conductive agent (conductive carbon black), binder (PVDF) and solvent (xylene) are mixed.

[0156] The mass ratio of the above-mentioned positive electrode active material, particulate solid electrolyte, conductive agent and binder is 85:10:2:3.

[0157] In step (2), the pressing pressure is replaced with 120 MPa;

[0158] Under the same conditions, the positive electrode of the all-solid-state battery, DS1, was obtained.

[0159] Comparative Example 2

[0160] The method is the same as in Example 1, except that...

[0161] In step (1), the positive electrode active material (NCM(Ni90), with an average particle size of 7 μm), particulate solid electrolyte (LPSC, with a particle size of 2 μm), conductive agent (conductive carbon black), binder (PVDF) and solvent (xylene) are mixed.

[0162] The mass ratio of the above-mentioned positive electrode active material, particulate solid electrolyte, conductive agent and binder is 75:20:2:3.

[0163] In step (2), the pressing pressure is replaced with 300 MPa;

[0164] Under the same conditions, the all-solid-state battery cathode DS2 was obtained.

[0165] Table 1

[0166]

[0167]

[0168] Note: * - The sum of the contents of fibrous solid electrolytes and particulate solid electrolytes.

[0169] As can be seen from the results in Table 1, compared with Comparative Examples 1-2, Examples 1-8 use the fibrous solid electrolyte provided by the present invention to construct electrodes with a three-dimensional fast ion conductor network, which has the effects of low solid electrolyte content, low pressing pressure and high electrode ion conductivity.

[0170] Test case

[0171] The electrodes prepared in the above examples and comparative examples were used to assemble half-cells, and their electrochemical performance was tested.

[0172] Assemble the half-cell: Combine the sleeve (10mm in diameter) with the lower mold, and weigh 100mg of normal sulfide electrolyte powder (e.g., Li6PS5Cl, spherical particles, 20μm in diameter, with an ionic conductivity of 3.5×10⁻⁶). -3 S / cm) is poured into the sleeve, and a pressure of 8MPa is applied using a hydraulic press and held for 5 minutes to obtain a compacted electrolyte layer;

[0173] Punch out 10mm diameter positive or negative electrode sheets using a punch, place them into a sleeve, with the side containing the active material in contact with the electrolyte layer; on the other side, sequentially attach an 8mm diameter × 60μm thick indium sheet and a 10mm diameter × 30μm thick lithium sheet, then close the mold, apply pressure to 8MPa with a hydraulic press, hold the pressure for 1 minute, and then remove. Install the screws and nuts, and use a 5N×m torque wrench to press the mold, completing the assembly of the all-solid-state battery;

[0174] Electrode specific capacity test conditions: 8 hours of rest; constant current charging at 0.1C, cutoff voltage 2.8-4.4V vs. Li / Li + Constant current discharge at 0.1C, cutoff voltage 2.8-4.4V vs. Li / Li + ;

[0175] Cyclic performance test conditions: constant current charging at 0.5C, cutoff voltage 2.8-4.4V vs. Li / Li + Constant current discharge at 0.5C, cutoff voltage 2.8-4.4V vs. Li / Li + Repeat 500 times.

[0176] Table 2

[0177]

[0178] As can be seen from the results in Table 2, compared with Comparative Examples 1-2, Examples 1-8, which use the fibrous solid electrolyte provided by the present invention to construct a three-dimensional fast ion conductor network in the electrode, have significantly better effects, such as higher specific capacity and better cycle performance under lower confinement pressure.

[0179] The preferred embodiments of the present invention have been described in detail above; however, the present invention is not limited thereto. Within the scope of the inventive concept, various simple modifications can be made to the technical solutions of the present invention, including combinations of various technical features in any other suitable manner. These simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within the protection scope of the present invention.

Claims

1. A solid-state battery electrode, characterized in that, The all-solid-state battery electrode contains a fibrous solid electrolyte.

2. The all-solid-state battery electrode according to claim 1, wherein, The fibrous solid electrolyte has a Push's ratio ≥ 1.6, preferably 1.7-6.5; Preferably, the shear modulus of the fibrous solid electrolyte is ≤30 GPa, and more preferably 0.5-20 GPa.

3. The all-solid-state battery electrode according to claim 1 or 2, wherein, The fibrous solid electrolyte has a room temperature ionic conductivity ≥10. -4 S / cm, preferably ≥5×10 -4 S / cm, more preferably ≥10 -3 S / cm.

4. The all-solid-state battery electrode according to any one of claims 1-3, wherein, The average length of the fibrous solid electrolyte is 1-5000 μm, preferably 2-2000 μm; Preferably, the average diameter of the fibrous solid electrolyte is ≤1μm, and more preferably 5-500nm; Preferably, based on the total weight of the effective components in the all-solid-state battery electrode, the content of the fibrous solid electrolyte is 0.1-20 wt%, more preferably 3-15 wt%.

5. The all-solid-state battery electrode according to any one of claims 1-4, wherein, The electrolyte material of the fibrous solid electrolyte is selected from at least one of sulfide electrolytes, sulfur oxide electrolytes, halide electrolytes, halide oxide electrolytes, oxide electrolytes, and polymer electrolytes. Preferably, the fibrous solid electrolyte is obtained from finished electrolyte products or electrolyte raw materials through air-jet spinning, electrospinning, and phase separation.

6. The all-solid-state battery electrode according to any one of claims 1-5, wherein, The all-solid-state battery electrode also contains granular solid electrolyte; Preferably, the D50 particle size of the particulate solid electrolyte is 200 nm-10 μm, and more preferably 200 nm-5 μm; Preferably, the mass ratio of the fibrous solid electrolyte to the particulate solid electrolyte is 0.1-10:1, more preferably 1-5:

1.

7. The all-solid-state battery electrode according to any one of claims 1-6, wherein, The all-solid-state battery electrode also contains active material, which is selected from positive electrode active material or negative electrode active material; Preferably, based on the total weight of the effective components in the all-solid-state battery electrode, the content of the active material is ≥70wt%, preferably 85-95wt%.

8. The all-solid-state battery electrode according to claim 7, wherein, The surface of the active material is provided with a coating layer, which is selected from fast ion conductors and / or electronic conductors; Preferably, the fast ion conductor is selected from at least one of sulfide electrolytes, sulfur oxide electrolytes, halide electrolytes, halide oxide electrolytes, and oxide electrolytes; Preferably, the electronic conductor is selected from at least one of conductive carbon black, acetylene black, Ketjen black, carbon nanofibers, carbon nanotubes, carbon nanowires, carbon nanosheets, and graphene. Preferably, the thickness of the coating layer is 1 nm-5 μm, and more preferably 5-500 nm.

9. The all-solid-state battery electrode according to any one of claims 1-8, wherein, The porosity of the all-solid-state battery electrode is 0-30%, preferably 2-20%; Preferably, the median pore size of the all-solid-state battery electrode is 10nm-10μm, and more preferably 10nm-2μm.

10. A method for preparing an all-solid-state battery electrode, characterized in that, The preparation method includes: A slurry containing a fibrous solid electrolyte and a solvent is coated onto a current collector and then dried and pressed; alternatively, a solvent-free mixture containing a fibrous solid electrolyte is coated onto a current collector and then pressed. All-solid-state battery electrodes were obtained.

11. The preparation method according to claim 10, wherein, The pressing pressure is 0.1-200 MPa, preferably 0.1-100 MPa, and more preferably ≤80 MPa; Preferably, the mixed slurry and the mixed materials also independently contain active substances, conductive agents and binders; Preferably, the mixed slurry and the mixed materials also independently contain particulate solid electrolytes.

12. A battery cell, characterized in that, The cell includes a positive electrode, a negative electrode, and an electrolyte layer; wherein the positive electrode and / or the negative electrode are each independently selected from the all-solid-state battery electrode according to any one of claims 1-9, or the all-solid-state battery electrode prepared by the preparation method according to claim 10 or 11. Preferably, the confinement pressure of the all-solid-state battery is 0.1-100 MPa, and more preferably 0.5-20 MPa.

13. An all-solid-state battery, characterized in that, The all-solid-state battery includes at least one cell as described in claim 12, which is either stacked or wound.

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