Solid-state battery positive electrode, solid-state battery negative electrode, preparation method thereof and battery with solid-state battery positive electrode and solid-state battery negative electrode

Abstract

The invention relates to the technical field of batteries, in particular to a solid-state battery positive electrode, a solid-state battery negative electrode, a preparation method thereof and a battery with the solid-state battery positive electrode and the solid-state battery negative electrode. The solid-state battery positive electrode comprises a positive electrode material, the positive electrode material comprises nickel-based particles, an inner layer and an outer layer, the nickel-based particles are covered with the inner layer and the outer layer, the ionic conductivity of the inner layer is larger than that of the outer layer, the electron blocking rate of the inner layer is smaller than that of the outer layer, and in the solid-state battery positive electrode, the thickness of the outer layer is thinned in a gradient mode; the conductive additive comprises a three-dimensional composite network structure formed by compounding a vertical layer and a transverse layer, the vertical layer is used for ion transmission in the vertical direction, and the transverse layer is used for transverse conduction; and the nickel-based particles contain a conductive additive. The solid-state battery positive electrode has relatively low impedance.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of batteries, in particular to a solid-state battery positive electrode, a solid-state battery negative electrode, a preparation method thereof and a battery with the same. BACKGROUND

[0002] In the field of batteries, the electrode system formed by a nickel positive electrode and a silicon-based negative electrode has many advantages, such as high conductivity of the silicon-based negative electrode, low cost of the silicon-based negative electrode, etc. Among these advantages, the theoretical energy density of the electrode system is larger than that of the traditional battery, and the highest theoretical energy density is close to 400 Wh / kg. However, the electrode system has defects such as volume expansion of the silicon-based negative electrode and interface side reaction of the nickel positive electrode.

[0003] In order to solve the defects of the electrode system formed by the nickel positive electrode and the silicon-based negative electrode, an interface layer of a specific material can be used on the surface of the nickel positive electrode and the silicon-based negative electrode at present. However, the interface layer covering the positive electrode is difficult to dynamically adjust the impedance during the running stage of the battery, and also increases the impedance of the interface layer, which affects the normal function of the battery. SUMMARY

[0004] The present application provides a solid-state battery positive electrode, a solid-state battery negative electrode, a preparation method thereof and a battery with the same, to solve the technical problem of how to reduce the impedance of the interface layer.

[0005] In a first aspect, an embodiment of the present application provides a solid-state battery positive electrode, characterized in that the solid-state battery positive electrode comprises:

[0006] a positive electrode material, the positive electrode material comprising: nickel-based particles, and an inner layer and an outer layer covering the nickel-based particles, the ion conductivity of the inner layer being greater than the ion conductivity of the outer layer, and the electron blocking rate of the inner layer being less than the electron blocking rate of the outer layer, wherein, in the solid-state battery positive electrode, the side of the solid-state battery positive electrode farthest from the solid-state battery negative electrode to the side of the solid-state battery positive electrode closest to the solid-state battery negative electrode is a first positive direction, and the thickness of the outer layer is gradiently thinned; and,

[0007] a conductive additive, the conductive additive comprising a three-dimensional composite network structure composed of vertical layers and horizontal layers, the vertical layers being used for vertical ion transmission, and the horizontal layers being used for horizontal conduction, and

[0008] The nickel-based particles contain the conductive additive.

[0009] Optionally, the mass of the conductive additive is 3.5% to 4.5% of the mass of the positive electrode material.

[0010] Optionally, the thickness of the inner layer is 0.1-0.3 μm, and the thickness of the outer layer is tapered from 50 nm to 10 nm along the first positive direction.

[0011] Optionally, the material of the inner layer comprises one or a combination of at least two of lithium strontium titanate, lithium lanthanum zirconium oxide, tantalum-doped lithium lanthanum zirconium oxide, lithium zirconium phosphate, and lithium polyethylene oxide-bis-trifluoromethanesulfonimide composite system; and / or

[0012] The material of the outer layer comprises one or a combination of at least two of lithium phosphorus oxynitride, lithium phosphate, lithium aluminum oxide, and lithium titanate; and / or

[0013] The material of the vertical layer comprises one or a combination of at least two of carbon nanotubes, graphene, and Ketjen black; and / or

[0014] The material of the horizontal layer comprises one or a combination of at least two of graphene, carbon nanofiber, Ti3C2T x .

[0015] Optionally, the mass m1 of the material of the inner layer and the mass m2 of the material of the outer layer satisfy: m1:m2=(6.5-7.5):(2.5-3.5); and / or

[0016] The mass m3 of the material of the vertical layer and the mass m4 of the material of the horizontal layer satisfy: m3:m4=(2-4):(6-8).

[0017] Optionally, the particle size of the material of the inner layer is 100-350 nm; and / or

[0018] The particle size of the material of the outer layer is 20-50 nm; and / or

[0019] The pore size of the vertical layer is 50-5000 nm;

[0020] The porosity of the three-dimensional composite network structure is 62-68%.

[0021] Optionally, the ionic conductivity of the inner layer at 25°C is >1.2 mS / cm; and / or

[0022] The resistivity of the outer layer is >10 8 Ω·cm; and / or

[0023] The conductivity of the horizontal layer is >1000 S / cm.

[0024] Optionally, the positive electrode of the solid-state battery further comprises a positive electrode substrate, and the positive electrode material is coated on the positive electrode substrate.

[0025] Optionally, the positive electrode material contains the conductive additive.

[0026] In a second aspect, the embodiments of the present application provide a preparation method of the positive electrode material of the first aspect, and the preparation method comprises:

[0027] Under the action of a magnetic field, the material of the vertical layer and the material of the horizontal layer are compounded to construct a three-dimensional composite network structure to obtain a conductive additive;

[0028] The nickel-based particles and the conductive additive are sequentially mixed and dried to obtain a mixed dry material;

[0029] The material of the inner layer is deposited on the surface of the mixed dry material by atomic layer deposition to obtain first composite particles containing nickel-based particles and the inner layer;

[0030] The material of the outer layer is deposited on the surface of the first composite particles by atomic layer deposition to obtain the positive electrode material;

[0031] The positive electrode material is prepared into a positive electrode slurry;

[0032] The positive electrode slurry is coated on a positive electrode base material to obtain the positive electrode material;

[0033] In the solid-state battery positive electrode, a first positive direction is from a side of the solid-state battery positive electrode far away from a solid-state battery negative electrode to a side of the solid-state battery positive electrode close to the solid-state battery negative electrode, and the thickness of the outer layer is gradiently reduced along the first positive direction.

[0034] In a third aspect, the embodiments of the present application provide a solid-state battery negative electrode, which comprises a silicon-based negative electrode base and a negative electrode interface layer covering the silicon-based negative electrode base, wherein a second positive direction is from a side of the solid-state battery negative electrode far away from a solid-state battery positive electrode to a side of the solid-state battery negative electrode close to the solid-state battery positive electrode, the negative electrode interface layer comprises a support layer, a heat-conducting layer and a buffer layer distributed along the second positive direction, the material density of the heat-conducting layer decreases along the second positive direction, and the material density of the buffer layer increases along the second positive direction.

[0035] The heat-conducting layer contains a conductive additive, the conductive additive is a three-dimensional composite network structure compounded by a vertical layer and a horizontal layer, the vertical layer is used for ion transmission in the vertical direction, and the horizontal layer is used for lateral conduction.

[0036] Optionally, the mass of the conductive additive is 4.5% to 5.5% of the total mass of the negative electrode interface layer.

[0037] Optionally, the total thickness of the negative electrode interface layer is 9 μm to 11 μm, and the density of the heat-conducting layer decreases from 2.0 g / cm 3 to 0.8 g / cm3 the thickness of the buffer layer is 0.6 g / cm 3 increasing to 1.2 g / cm 3 .

[0038] Optionally, the material of the support layer comprises one or a combination of at least two of polyimide, polybenzimidazole, polyether ether ketone, silicon carbide reinforced composite; and / or

[0039] The material of the heat-conducting layer comprises one or a combination of at least two of boron nitride, graphene nanosheet, silicon carbide nanowire; and / or

[0040] The material of the buffer layer comprises one or a combination of at least two of polyurethane acrylate, silicone modified polyurethane, hydrogenated nitrile rubber; and / or

[0041] The material of the vertical layer comprises one or a combination of at least two of carbon nanotube, graphene, Ketjen black; and / or

[0042] The material of the horizontal layer comprises one or a combination of at least two of graphene, carbon nanofiber, Ti3C2T x .

[0043] Optionally, the mass m5 of the material of the support layer, the mass m6 of the material of the heat-conducting layer, and the mass m7 of the material of the buffer layer satisfy: m5:m6:m7=(5 to 7):(2 to 4):1; and / or

[0044] The mass m8 of the material of the vertical layer and the mass m9 of the material of the horizontal layer satisfy: m8:m9=(2 to 4):(6 to 8).

[0045] Optionally, the shear strength of the support layer is >2.5 GPa, the thermal conductivity of the heat-conducting layer is >400 W / m·K, and the elongation at break of the buffer layer is >150%; and / or

[0046] The electrical conductivity of the horizontal layer is >1000 S / cm.

[0047] In a fourth aspect, the embodiments of the present application provide a preparation method of the solid-state battery negative electrode of the first aspect, and the preparation method comprises:

[0048] Under the action of a magnetic field, the material of the vertical layer and the material of the horizontal layer are compounded to construct a three-dimensional composite network structure, and an electrically conductive additive is obtained;

[0049] The material of the heat-conducting layer and the electrically conductive additive are mixed to obtain a negative electrode active paste;

[0050] A support layer is prepared on a silicon-based negative electrode substrate;

[0051] gradient coating on the surface of the support layer to obtain a first composite layer containing a support layer and a thermal conductive layer; wherein the gradient coating comprises increasing extrusion pressure;

[0052] coating a material of the buffer layer on the surface of the first composite layer containing a support layer and a thermal conductive layer to obtain a second composite layer containing a buffer layer, a thermal conductive layer and a support layer;

[0053] gradient photocuring the second composite layer containing a buffer layer, a thermal conductive layer and a support layer using increasing light intensity to obtain a negative electrode material containing a negative electrode interface layer.

[0054] In a fifth aspect, the embodiments of the present application provide a battery containing a solid-state electrolyte, a solid-state battery cathode as described in the first aspect, and a solid-state battery anode as described in the second aspect, the solid-state battery cathode and the solid-state battery anode being distributed on two sides of the solid-state electrolyte.

[0055] The above technical solutions provided by the embodiments of the present application have the following advantages compared with the prior art:

[0056] The solid-state battery cathode provided by the embodiments of the present application adopts a design strategy of a composite interface between an inner layer and an outer layer. The inner layer material has a relatively high ionic conductivity, which helps to significantly reduce the migration potential barrier of lithium ions in the cathode material, thereby reducing the internal resistance. The outer layer adopts a gradient thickness design that gradually thins from the inside to the outside to adapt to the curvature change of the surface of the cathode material, effectively reducing the surface stress of the negative electrode interface layer and enhancing the stability of the cathode interface layer. In addition, this gradient distribution can also promote the outer layer with a higher resistivity to form a gradient electron blocking layer, which limits the flow of electrons in different regions, thereby effectively inhibiting the cathode side reaction and interface phase change and improving the chemical stability of the inner layer. Conductive additives are added to the nickel-based particles, and these conductive additives form a three-dimensional composite network structure combining vertical layers and horizontal layers. The vertical layers provide nanoscale ion transmission channels, further accelerating the migration speed of lithium ions in the cathode material; the horizontal layers build a horizontal conductive network, reducing the interface impedance between the nickel-based particles. The three-dimensional composite network structure of the conductive additives significantly improves the uniformity of the current density distribution of the nickel-based particles during the charging and discharging process, eliminates the dynamic adjustment impedance inside the particles, and thus effectively reduces the impedance of the cathode material. BRIEF DESCRIPTION OF DRAWINGS

[0057] The accompanying drawings, which are incorporated into and form part of the specification, illustrate embodiments consistent with the present application and, together with the description, serve to explain the principles of the application.

[0058] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the following will briefly introduce the drawings needed to be used in the embodiments or prior art description. Obviously, for those of ordinary skill in the art, other drawings can also be obtained based on these drawings without any creative effort.

[0059] Figure 1 A structural schematic diagram of a solid-state battery positive electrode and a solid-state battery negative electrode provided by the embodiments of the present application is shown in the figure.

[0060] Figure 2 A preparation method flowchart of a solid-state battery positive electrode provided by the embodiments of the present application is shown in the figure.

[0061] Figure 3 A preparation method flowchart of a solid-state battery negative electrode provided by the embodiments of the present application is shown in the figure. DETAILED DESCRIPTION

[0062] In order to make the objects, technical solutions and advantages of the embodiments of the present application clearer, the following will combine the drawings in the embodiments of the present application to clearly and completely describe the technical solutions in the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without any creative effort fall within the scope of protection of the present application.

[0063] Various embodiments of the present application can exist in the form of a range; it should be understood that the description in the form of a range is only for the convenience and brevity, and should not be understood as a hard limit on the scope of the present application; therefore, it should be considered that the described range has specifically disclosed all possible sub-ranges and single values in the range; for example, it should be considered that the range description from 1 to 6 has specifically disclosed sub-ranges, such as from 1 to 3, from 1 to 4, from 1 to 5, from 2 to 4, from 2 to 6, from 3 to 6, etc., as well as single numbers in the range, such as 1, 2, 3, 4, 5 and 6, which applies to any range; in addition, whenever a numerical range is indicated in this document, it refers to any cited number (fraction or integer) in the indicated range.

[0064] In this document, the terms "comprise" and "comprising" and the like refer to a "consisting of", or "consisting essentially of", and the like, unless otherwise stated. Conjunctive terms such as "first" and "second" and the like can simply serve to distinguish one entity or action from another, without necessarily requiring or implying any actual such relationship or order between entities or actions. The term "and / or" between a conjunctive entity refers to a conjunctive relationship, indicating that there are three possible relationships, for example, A and / or B, which can mean: A alone, A and B together, B alone; wherein A, B can be singular or plural. "At least one" means one or more, "a plurality" means two or more; "at least one of" or "one or more of" or the like refers to any combination of the items, including single items or plural items, for example, "at least one of a, b, or c" or "at least one of a, b, and c" can mean: a, b, c, a-b (i.e., a and b), a-c, b-c, or a-b-c, wherein a, b, c can be singular or plural. "Parts" such as weight parts, mass parts, etc. represent the proportional relationship between components. In the proportional relationship described herein, the parameters that need to be described by the proportion should be understood as the front item of the proportional formula in the order of description, and the proportional number should be understood as the back item of the proportional formula, for example, the material mass ratio of substance A, substance B and substance C is 1:2:3, then substance A, substance B and substance C should be one-to-one corresponding in the proportional formula according to the description order, that is, the mass of substance A: the mass of substance B: the mass of substance C = 1:2:3.

[0065] Unless otherwise specified, the various raw materials, reagents, instruments and equipment used in this document can be purchased on the market or can be prepared by existing methods.

[0066] It should be noted that the electrode system formed by the nickel positive electrode and the silicon-based negative electrode at the present stage faces two core problems: (1) volume expansion of silicon-based negative electrode: the volume expansion rate of silicon-based negative electrode during lithium intercalation reaction is as high as 300%, which causes shear stress between the rigid interface layer and the silicon-based negative electrode, and the existence of shear stress will cause interface peeling of the silicon-based negative electrode and fracture of the electron and ion transmission path, so that the increase of direct current resistance of the silicon-based negative electrode after multiple cycles is more than 50%; (2) interface side reaction of nickel positive electrode: the nickel positive electrode will release oxygen-containing substances (such as oxygen or carbonate ions) during use, and these oxygen-containing substances will have a chemical corrosion reaction with the solid-state electrolyte of the solid-state battery, forming an interface reaction layer with high impedance, which will reduce the lithium ion diffusion coefficient of the solid-state battery, and will significantly increase the polarization voltage of the solid-state battery.

[0067] Although the interface layer of a specific material can be used at present, these interface layers have the following defects: (1) rigidity mismatch of a single material: the interface layer generally uses a single material, although these single material interface layers have high ionic conductivity, but the Young's modulus of the single material interface layer does not match the expansion stress of the silicon-based negative electrode, which increases the crack density of the interface layer under the condition of multiple cycles of the solid-state battery; (2) dynamic absence of the static interface layer: the traditional interface layer cannot adjust the impedance of the solid-state battery according to the operating state of the battery cell, resulting in uneven distribution of local current density under the condition of high-rate charging and discharging of the solid-state battery, which aggravates the gas generation of the solid-state battery. These gases will participate in the interface side reaction and increase the degree of the interface side reaction, forming chemical corrosive substances with high impedance, which will increase the impedance of the interface layer; (3) limitations of single component interface layer: the single material interface layer functions as either an ionic conductor or an electron barrier. Although such interface layers can block electron leakage, the single material interface layer has low fracture toughness and cannot effectively inhibit the expansion of interface cracks.

[0068] In view of the above defects of the interface layer, a single metal oxide interface layer and a polymer composite interface layer can be used, wherein the preparation process of the single metal oxide interface layer is: using a single material of lithium lanthanum zirconium oxide or lithium phosphorus oxygen nitrogen to coat the surface of the electrode, and then hot pressing to obtain a single metal oxide interface layer. The preparation process of the polymer composite interface layer is: taking polyethylene oxide or polyvinylidene fluoride-trifluoroethylene-2-propenoyl polycaprolactone as a solution, mixing the solution with ceramic particles to form a mixture, and then pouring the mixture into a film by solution casting to obtain a polymer composite interface layer. Although the single metal oxide interface layer has good ionic conductivity, the single metal oxide interface layer can only function as an ionic conductor or an electron barrier, and it is difficult to achieve both. Although the polymer composite interface layer can realize the dual function of ionic conductor and electron barrier through multiple functional materials, the polymer in the polymer composite interface layer will reduce its ionic conductivity, and the polymer will soften at a higher use temperature, reducing the stability of the polymer composite interface layer, thereby causing the polymer composite interface layer to collapse. These collapsed polymer composite interface layers will significantly increase the impedance of the composite interface layer.

[0069] Therefore, based on the above-mentioned defects of the interface impedance of the interface layer, the present application provides the following content:

[0070] Figure 1 An exemplary structure diagram of a solid-state battery positive electrode and a solid-state battery negative electrode provided by the embodiments of the present application is shown;

[0071] As Figure 1As shown, the embodiment of the present application provides a solid-state battery positive electrode, which comprises:

[0072] The positive electrode material comprises: nickel-based particles, and an inner layer and an outer layer covering the nickel-based particles, the ion conductivity of the inner layer is greater than that of the outer layer, and the electron blocking rate of the inner layer is less than that of the outer layer, wherein, in the solid-state battery positive electrode, the side of the solid-state battery positive electrode away from the solid-state battery negative electrode is the first positive direction to the side of the solid-state battery positive electrode close to the solid-state battery negative electrode, and the thickness of the outer layer is gradiently thinned along the first positive direction; and,

[0073] The conductive additive comprises a three-dimensional composite network structure composed of vertical layers and horizontal layers, the vertical layers are used for ion transmission in the vertical direction, and the horizontal layers are used for lateral conduction.

[0074] The conductive additive is contained in the nickel-based particles.

[0075] It should be noted that the nickel-based particles can be high-nickel-content nickel-based active materials.

[0076] It should be noted that the ion conductivity of the inner layer is measured by the Gamry standard Electrochemical Impedance Spectroscopy (EIS). The thermal conductivity of the N layer is measured by the ISO22007 standard laser flash method.

[0077] It should be noted that the ion conductivity of the outer layer at 25°C can be greater than 5×10 -7 S / cm; and the electron conductivity of the inner layer and the outer layer can be greater than 1×10 -8 S / cm.

[0078] It should be noted that the inner layer and the outer layer are combined by chemical bonding or physical coating, which can promote the close combination between the inner layer and the outer layer, so as to form a dense film between the inner layer and the outer layer.

[0079] It should be noted that the material of the inner layer can be combined with the surface oxygen atoms of the nickel-based particles by covalent bonding, so as to form a stable inner layer film. In addition, the material of the outer layer can be connected to the material of the inner layer by sharing oxygen atoms, so as to form a stable outer layer film, and finally form a continuous ion transmission channel through the outer layer.

[0080] It should be noted that the vertical layer and the horizontal layer are bridged by the conductive polymer, so that a uniform and stable three-dimensional composite network structure can be formed between the vertical layer and the horizontal layer, which can reduce the impedance of the two interface layers and avoid the interface polarization phenomenon of the two interface layers, thereby improving the stability of the two interface layers.

[0081] It should be noted that the solid-state battery positive electrode provided by the embodiment of the present application has the structure optimization of the inner layer and the outer layer on the nickel-based particles, and the structure optimization of the conductive additive, which significantly reduces the impedance of the interface layer of the positive electrode material and improves the chemical and mechanical stability of the solid-state battery positive electrode. The specific mechanism is as follows:

[0082] 1. Design advantage of positive electrode interface layer

[0083] (1) Inner layer function optimization

[0084] The inner layer with high ionic conductivity serves as a fast ion channel, which can reduce the migration barrier of lithium ions, and the material of the inner layer can have chemical inertness, reducing the probability of side reactions between the inner layer and the nickel-based particles.

[0085] Similar to the coating mechanism of sulfide solid-state electrolyte, the inner layer can form a stable Li + conductive network, reducing the interface impedance of the positive electrode interface layer.

[0086] (2) Outer layer electron blocking mechanism

[0087] The outer layer with high resistivity inhibits the penetration of electrons into the positive electrode material through physical isolation, avoids the oxidation and decomposition of the positive electrode material, plays an electron insulation effect, and improves the stability of the positive electrode material.

[0088] 2. Three-dimensional conductive network synergistic effect

[0089] (1) Synergistic transmission of vertical layer and horizontal layer

[0090] The vertical ion channel of the vertical layer can realize a nanoscale ion path;

[0091] The horizontal conductive network of the horizontal layer can significantly reduce the interface impedance of the positive electrode material.

[0092] (2) Interface polarization suppression

[0093] The three-dimensional network formed by the vertical layer and the horizontal layer can improve the uniformity of current density distribution, effectively eliminating the local charge accumulation of the inner layer and the outer layer of the positive electrode material.

[0094] 3. Comprehensive performance improvement

[0095] The design of the solid-state battery positive electrode can improve the interface thermal runaway temperature of the positive electrode material, maintain the stability of the interface impedance of the solid-state battery positive electrode, and reduce the growth of the interface impedance of the solid-state battery positive electrode after multiple cycles through the isolation of the inner layer and the outer layer of the positive electrode material and the three-dimensional conductive synergy of the conductive additive.

[0096] In some optional embodiments, the mass of the conductive additive is 3.5% to 4.5% of the mass of the positive electrode material.

[0097] In these embodiments, the conductive additive with a mass of 3.5% to 4.5% of the mass of the positive electrode material can introduce sufficient three-dimensional composite network structures to the positive electrode interface layer, which can effectively reduce the impedance of the positive electrode interface layer to improve the stability of the positive electrode interface layer.

[0098] The mass of the conductive additive is 3.5%, 3.6%, 3.7%, 3.8%, 3.9%, 4.0%, 4.1%, 4.2%, 4.3%, 4.4%, or 4.5% of the mass of the positive electrode material.

[0099] In some optional embodiments, the thickness of the inner layer is 0.1 μm to 0.3 μm, and the thickness of the outer layer is tapered from 50 nm to 10 nm along the first positive direction.

[0100] In these embodiments, the inner layer with a thickness of 0.1 μm to 0.3 μm can ensure the stability of the fast ion channel of the conductive additive, effectively reduce the migration barrier of lithium ions, and reduce the internal resistance of the inner layer. In addition, the outer layer with a thickness tapered from 50 nm to 10 nm along the first positive direction can act as a gradient electron blocking layer without affecting the migration of lithium ions, effectively block electrons at a lower thickness, inhibit the occurrence of positive electrode side reactions and the interface phase transition of the positive electrode material caused by electron movement, and avoid the increase of the impedance of the solid-state battery positive electrode during the charging and discharging process.

[0101] The thickness of the inner layer can be 0.1 μm, 0.15 μm, 0.2 μm, 0.25 μm, or 0.30 μm.

[0102] In some optional embodiments, the material of the inner layer includes one or a combination of at least two of lithium strontium titanate, lithium lanthanum zirconium oxide, tantalum-doped lithium lanthanum zirconium oxide, lithium zirconium phosphate, and a polyethylene oxide-bistrifluoromethanesulfonimide lithium composite system; and / or

[0103] The material of the outer layer includes one or a combination of at least two of lithium phosphorus oxynitride, lithium phosphate, lithium aluminum oxide, and lithium titanate; and / or

[0104] The material of the vertical layer includes one or a combination of at least two of carbon nanotubes, graphene, and Ketjen black; and / or

[0105] The material of the horizontal layer includes one or a combination of at least two of graphene, carbon nanofiber, Ti3C2T x

[0106] In these embodiments, the inner layer is formed using one or a combination of at least two of lithium strontium titanate, lithium lanthanum zirconium oxide, tantalum-doped lithium lanthanum zirconium oxide, lithium zirconium phosphate, and polyethylene oxide-bis-trifluoromethanesulfonimide lithium composite system, on the one hand, these oxide solid electrolytes and polymer solid electrolytes have good ionic conductivity and a wide electrochemical window, which can improve the conductivity and electrochemical activity of the positive electrode material to effectively reduce the impedance of the positive electrode interface layer; on the other hand, these oxide solid electrolytes and polymer solid electrolytes also have good chemical stability, which can be well compatible with the nickel-based particles and the electrolyte of the battery. In addition, the outer layer formed using one or a combination of at least two of lithium phosphorus oxynitride, lithium phosphate, lithium aluminum oxide, and lithium titanate not only has good electron blocking ability, but also has good interface passivation ability, which can effectively coat the nickel-based particles to further reduce the risk of positive electrode side reactions of the nickel-based particles and avoid the increase of the impedance of the interface layer by the substances formed by the positive electrode side reactions.

[0107] The vertical layer formed using one or a combination of at least two of carbon nanotubes, graphene, and Ketjen black can form vertical ion channels in the positive electrode interface layer and the negative electrode interface layer to reduce the impedance of the two interface layers and avoid the occurrence of interface polarization in the positive electrode interface layer, thereby improving the stability of the two interface layers. In addition, the horizontal layer formed using one or a combination of at least two of graphene, carbon nanofiber, Ti3C2T x

[0108] It should be noted that the nickel-based metal material can use micron-sized nickel-based metal materials, so that the inner layer and the outer layer have sufficient specific surface area. The inner layer with sufficient specific surface area can provide sufficient ion paths to reduce the impedance of the positive electrode interface layer, while the outer layer with sufficient specific surface area can effectively block the movement of electrons to inhibit the positive electrode side reactions and interface phase change of the positive electrode interface layer, thereby improving the stability of the positive electrode interface layer and the stability of the impedance of the solid-state battery positive electrode during the operation of the battery.

[0109] It should be noted that the vertical layer and the horizontal layer need to have good chemical inertness to avoid damage to the two interface layers due to the reaction between the vertical layer and the horizontal layer and the electrolyte, thereby affecting the stability of the interface layer. In addition, the density of the C layer is preferably 2 g / cm​​3 The following makes the vertical layer have a lighter mass, which can promote the uniform distribution of the vertical layer in the positive electrode interface layer, control the distribution range of the vertical ion channel, further reduce the impedance of the positive electrode interface layer, and thus improve the stability of the two interface layers. In addition, the lateral layer also needs good dispersibility, which can form a three-dimensional composite network structure between the lateral layer and the vertical layer, which is uniformly distributed and stably exists, so as to effectively reduce the impedance of the positive electrode interface layer.

[0110] In some optional embodiments, the mass of the material of the inner layer m1 and the mass of the material of the outer layer m2 satisfy: m1:m2=(6.5 to 7.5):(2.5 to 3.5); and / or

[0111] The mass of the material of the vertical layer m3 and the mass of the material of the lateral layer m4 satisfy: m3:m4=(2 to 4):(6 to 8).

[0112] In these embodiments, the inner layer and the outer layer with a mass ratio of (6.5 to 7.5):(2.5 to 3.5) can form a multi-layer distributed nickel-based particle, and the inner layer wrapped nickel-based particle can improve the conductivity stability of the positive electrode interface layer through the inner layer, so as to reduce the internal resistance of the positive electrode material, thereby reducing the impedance of the solid-state battery positive electrode; in addition, the outer layer wrapped inner layer can avoid the migration of nickel-based particle electrons through the electron blocking effect of the outer layer, so as to inhibit the occurrence of positive electrode side reactions and interface phase changes of the positive electrode interface layer, and avoid the increase of the impedance of the interface layer caused by the positive electrode side reaction. In addition, the vertical layer and the lateral layer with a mass ratio of (2 to 4):(6 to 8) can form a three-dimensional composite network structure with sufficient pores, so as to improve the current density distribution uniformity of the positive electrode material, thereby effectively eliminating the local charge accumulation of the nickel-based particle and reducing the impedance of the solid-state battery positive electrode.

[0113] The mass m1 of the material of the inner layer can be 6.5, 6.6, 6.7, 6.8, 6.9, 7.0, 7.1, 7.2, 7.3, 7.4, or 7.5.

[0114] The mass m2 of the material of the outer layer can be 2.5, 2.6, 2.7, 2.8, 2.9, 3.0, 3.1, 3.2, 3.3, 3.4, or 3.5.

[0115] The mass m3 of the vertical layer can be 2, 3, or 4.

[0116] The mass m4 of the lateral layer can be 6, 7, or 8.

[0117] In some optional embodiments, the particle size of the material of the inner layer is 100 nm to 350 nm; and / or

[0118] the material of the outer layer has a particle size of 20nm to 50nm; and / or

[0119] the vertical layer has a pore size of 50nm to 5000nm;

[0120] the three-dimensional composite network structure has a porosity of 62% to 68%.

[0121] In these embodiments, the material of the inner layer with a particle size of 100nm to 350nm can be tightly filled in the gaps of the nickel-based particles, so that a uniform inner layer can be formed on the nickel-based particles. In addition, the material of the outer layer with a particle size of 20nm to 50nm can be sufficiently filled in the gaps of the inner layer to form a dense outer layer. In addition, the vertical layer with a pore size of 50nm to 5000nm can effectively accommodate the particle distribution of the horizontal layer to form a uniform three-dimensional composite network structure, which can effectively reduce the impedance of the positive electrode interface layer, avoid the interface polarization phenomenon of the two interface layers, and improve the stability of the positive electrode interface layer. Furthermore, the three-dimensional composite network structure with a porosity of 62% to 68% has good supportability, which can ensure the stability of the ion channel; in addition, the three-dimensional composite network structure has good dispersibility, which can effectively reduce the impedance of the positive electrode material.

[0122] The particle size of the material of the inner layer can be 100nm, 150nm, 200nm, 250nm, 300nm or 350nm.

[0123] The particle size of the material of the outer layer can be 20nm, 30nm, 40nm or 50nm.

[0124] The pore size of the vertical layer can be 50nm, 100nm, 150nm, 200nm, 250nm, 300nm, 350nm, 400nm, 450nm, 500nm, 600nm, 700nm, 800nm, 900nm, 1000nm, 2000nm, 3000nm, 4000nm or 5000nm.

[0125] The porosity of the conductive additive can be 62%, 63%, 64%, 65%, 66%, 67% or 68%.

[0126] It should be noted that when the particle size of the second nanoparticles is greater than 50nm, the second nanoparticles are prone to agglomeration, so that the outer layer formed by the second nanoparticles cannot be continuous, which causes the inner layer to be easily exposed, so that the outer layer cannot effectively protect the inner layer.

[0127] It should be noted that the vertical layer with a pore size of 50 nm (matching the Stokes radius) can ensure that the lithium ions are not affected by the steric hindrance of the interface layer when passing through; and the vertical layer with a pore size of 5000 nm can avoid the local enrichment of the electrolyte to cause the lithium dendrite phenomenon.

[0128] In some optional embodiments, the inner layer has an ion conductivity of > 1.2 mS / cm at 25°C; and / or

[0129] The outer layer has a resistivity of > 10 8 Ω·cm; and / or

[0130] The transverse layer has a conductivity of > 1000 S / cm.

[0131] In these embodiments, the inner layer with an ion conductivity of > 1.2 mS / cm at 25°C can serve as an efficient ion transmission channel, which can significantly reduce the impedance of ion migration in the nickel-based positive electrode material, while the inner layer has good chemical stability, which can improve the overall stability of the positive electrode material under low impedance conditions. The outer layer with a resistivity of > 10 8 Ω·cm can serve as an electron blocking layer, effectively inhibiting the occurrence of positive electrode side reactions and the interface phase transition of the positive electrode material, further improving the chemical stability of the inner layer to avoid the increase of the impedance of the solid-state battery positive electrode during charging and discharging. In addition, the transverse layer with a conductivity of > 1000 S / cm can significantly improve the transverse conductivity of the positive material and reduce the internal resistance of the solid-state battery positive electrode.

[0132] In some optional embodiments, the positive electrode material further comprises a positive electrode base material, and the nickel-based particles are covered on the surface of the positive electrode base material.

[0133] In these embodiments, the nickel-based particles with a double-layer structure comprising an inner layer and an outer layer are laminated on the surface of the positive electrode base material, which can form a positive electrode material with uniform distribution of particles, further improving the arrangement tightness of the nickel-based particles and the stability of the solid-state battery positive electrode.

[0134] It should be noted that the positive electrode base can be a base formed by a active metal, such as aluminum foil, copper foil, titanium foil, nickel foil.

[0135] In some optional embodiments, the positive electrode material contains the conductive additive.

[0136] In these embodiments, the conductive additive is arranged between the positive electrode materials, and the conductive three-dimensional network of the conductive additive can enhance the conductivity between the positive electrode materials to improve the conductivity within the positive electrode material.

[0137] Figure 2 An example of a method for preparing a solid-state battery positive electrode provided by the embodiments of the present application is shown in the flow chart.

[0138] Based on a general inventive concept, as shown in the embodiments of the present application, a preparation method of the solid-state battery cathode is provided, and the preparation method comprises the following steps: Figure 2

[0139] S1. Under the action of a magnetic field, the material of the vertical layer and the material of the horizontal layer are compounded to construct a three-dimensional composite network structure, and a conductive additive is obtained;

[0140] S2. The nickel-based particles and the conductive additive are sequentially mixed and dried to obtain a mixed dry material;

[0141] S3. The material of the inner layer is deposited on the surface of the mixed dry material by atomic layer deposition to obtain first composite particles containing nickel-based particles and the inner layer;

[0142] S4. The material of the outer layer is deposited on the surface of the first composite particles by atomic layer deposition to obtain a cathode material;

[0143] S5. The cathode material is prepared into a cathode slurry;

[0144] S6. The cathode slurry is coated on a cathode base material to obtain a solid-state battery cathode.

[0145] The preparation method is for the preparation method of the above-mentioned solid-state battery cathode. The specific composition of the solid-state battery cathode can refer to the above-mentioned embodiments. Since the preparation method adopts part or all of the technical solutions of the above-mentioned embodiments, it at least has all the beneficial effects brought by the technical solutions of the above-mentioned embodiments, which will not be repeated here.

[0146] It should be noted that the material of the vertical layer and the material of the horizontal layer are compounded under the action of a magnetic field. The specific principle is that: based on the fact that the materials used in the vertical layer and the horizontal layer contain a large amount of carbon components, these carbon components have certain magnetic resistance. Under the action of an external magnetic field, these carbon components with magnetic resistance will be directionally arranged due to the anisotropy of magnetic susceptibility. With the directional arrangement of the materials of the vertical layer and the horizontal layer, a three-dimensional composite network structure with uniform arrangement is formed between these materials. This three-dimensional composite network structure can superimpose the different functions of the vertical layer and the horizontal layer, and finally form a three-dimensional composite network structure with continuous electron-ion. This three-dimensional composite network structure can effectively reduce the impedance of the cathode interface layer and the anode interface layer, and improve the stability of the two interface layers. Then the conductive additive, the nickel-based particles, the material of the inner layer and the material of the outer layer are directly subjected to atomic layer deposition treatment, the inner layer and the outer layer are sequentially deposited on the surface of the nickel-based particles, and the conductive additive is fixed in the particles of the prepared cathode active slurry. Subsequently, the cathode active slurry is coated on the surface of the cathode base material to form a cathode interface layer on the cathode base material.​

[0147] It should be noted that the strength of the magnetic field can be 0.4T-0.6T, and in this strength range, the magnetic field can make the three-dimensional composite network structure formed by the vertical layer and the horizontal layer fully directional arrangement, and the directional arrangement of the three-dimensional composite network structure can enhance the composite channel function of the electrons and ions, to improve the conductivity of the two interface layers, further reduce the impedance of the positive electrode interface layer, and further improve the stability of the positive electrode interface layer.

[0148] The strength of the magnetic field can be 0.4T, 0.41T, 0.42T, 0.43T, 0.44T, 0.45T, 0.46T, 0.47T, 0.48T, 0.49T, 0.5T, 0.51T, 0.52T, 0.53T, 0.54T, 0.55T, 0.56T, 0.57T, 0.58T, 0.59T or 0.6T.

[0149] It should be noted that the direction of the magnetic field should be perpendicular to the directional arrangement direction of the three-dimensional composite network structure to facilitate full directional arrangement.

[0150] It should be noted that the atomic layer deposition temperature can be 170℃-190℃, and in this temperature range, atomic layer deposition can promote the material of the inner layer to be fully deposited on the surface of the nickel-based material to form an inner layer with sufficient thickness; at the same time, the atomic deposition can also promote the material of the outer layer to be fully deposited on the surface of the inner layer to finally obtain an outer layer that is gradually thinned from 50nm to 10nm from the inside out.

[0151] The atomic layer deposition temperature can be 170℃, 175℃, 180℃, 185℃ or 190℃.

[0152] It should be noted that the atomic layer deposition is carried out in sequence, the nickel-based particles, conductive additives and inner layer materials are dry mixed to obtain a mixed dry powder; then the mixed dry powder and N-methyl pyrrolidone solvent are mixed, and then dried to remove the solvent components to obtain a mixed dry material; then the inner layer material is used for atomic layer deposition on the fluidized bed to form a dense inner layer film on the surface of the nickel-based particles to obtain first composite particles; then the outer layer material is added to the first composite particles for atomic layer deposition to form a dense outer layer on the surface of the inner layer film.

[0153] It should be noted that the atomic layer deposition is performed on the fluidized bed, specifically, the inner layer is formed by using the material in the inner layer as a precursor, by means of gas phase adsorption of the precursor and mixed dry powder and surface chemical reaction in multiple cycles. Based on the same principle, an outer layer with uniform thickness can be deposited on the inner layer, and then based on the control effect of the fluidized bed, atomic or molecular level deposition can be realized in the atomic deposition process (for example, the thickness increase amount of each atomic layer deposition cycle can be controlled to be 0.1 nm), so that the outer layer can present a gradient change on the surface of the inner layer. Finally, an outer layer with a thickness of 50 nm gradually thinned to 10 nm from the inside to the outside can be obtained.

[0154] It should be noted that before the atomic layer deposition, the nickel-based particles can be cleaned by washing and the like, and then dried to remove the solvent used in the washing; the solvent used in the general washing process can be N-methyl pyrrolidone; the drying process is performed in a vacuum environment.

[0155] It should be noted that during the preparation of the positive electrode material into the positive electrode slurry, adhesives, dispersants and other additives can be added to form a positive electrode slurry with uniform dispersion of the positive electrode material. In addition, the prepared conductive additive can also be added to enhance the conductivity between the particles of the positive electrode material.

[0156] It should be noted that the coating method of the positive electrode slurry can be coating, and then the positive electrode slurry can be dried and formed after coating, so that a positive electrode interface layer with sufficient thickness is formed on the surface of the positive electrode base material, and then the positive electrode slurry is tightly attached to the surface of the positive electrode base material by rolling to form a positive electrode, and finally the positive electrode can be cut into shape to obtain a solid-state battery positive electrode.

[0157] It should be noted that for the prior art described in the background art, the inventors have also found that the Young's modulus of the interface layer formed by using a single metal oxide is difficult to match the silicon-based negative electrode substrate, and after the solid-state battery is used for multiple cycles, the peeling rate of the interface layer and the silicon-based negative electrode substrate is more than 50%, which is prone to peeling of the interface layer and the silicon-based negative electrode, which destroys the stability of the overall interface layer, and the peeled interface layer will accumulate to increase the interface impedance of the silicon-based negative electrode substrate.

[0158] Based on one overall inventive concept, as Figure 1As shown, the embodiment of the present application provides a solid-state battery negative electrode, which comprises a silicon-based negative electrode base and a negative electrode interface layer covering the silicon-based negative electrode base, wherein a side of the solid-state battery negative electrode away from a solid-state battery positive electrode is a second positive direction, and the negative electrode interface layer comprises a support layer, a thermal conductive layer and a buffer layer distributed along the second positive direction, the material density of the thermal conductive layer decreases along the second positive direction, and the material density of the buffer layer increases along the second positive direction.

[0159] The thermal conductive layer contains an electrically conductive additive, and the electrically conductive additive is a three-dimensional composite network structure composed of vertical layers and horizontal layers, the vertical layers are used for ion transmission in the vertical direction, and the horizontal layers are used for transverse conduction.

[0160] The negative electrode material provided by the embodiment of the present application adopts a negative electrode interface layer design comprising a support layer, a thermal conductive layer and a buffer layer. The support layer gives the negative electrode interface layer a higher mechanical strength, significantly enhancing the mechanical stability thereof. The density of the thermal conductive layer decreases from the inside to the outside, forming an efficient gradient thermal conductive interface, which helps to quickly homogenize the heat and prevent thermal decomposition and peeling of the negative electrode interface layer caused by uneven heat distribution, thereby reducing the impedance increase caused by the peeling of the interface layer. At the same time, the density of the buffer layer increases from the inside to the outside, matching the expansion coefficient of the silicon-based negative electrode base, improving the stress buffering of the negative electrode interface layer and avoiding the interface peeling between the negative electrode interface layer and the silicon-based negative electrode base. In addition, the electrically conductive additive is added to the thermal conductive layer, forming a three-dimensional composite network structure composed of vertical layers and horizontal layers. The vertical layers provide nanoscale ion transmission channels, further improving the migration rate of lithium ions in the negative electrode material; the horizontal layers construct a transverse conduction network, reducing the interface impedance of the negative electrode interface layer. The electrically conductive additive with such a three-dimensional composite network structure significantly improves the uniformity of the current density distribution of the silicon-based negative electrode base during the charging and discharging process, avoids the heat accumulation caused by the uneven distribution of local current, and thereby reduces the risk of decomposition and peeling of the negative electrode interface layer.

[0161] It should be noted that the electronic conductivity of the three-layer gradient composite negative electrode interface layer after the combination of the support layer, the thermal conductive layer and the buffer layer can be greater than 1x10 -6 S / cm.

[0162] It should be noted that the tensile strength of the support layer in the three-layer gradient composite negative electrode interface layer structure can be greater than 120MPa. The tensile strength can be measured according to the ASTM D638 standard.

[0163] It should be noted that the solid-state battery negative electrode provided by the embodiment of the application significantly reduces the impedance of the negative electrode interface and improves the chemical and mechanical stability of the negative electrode interface layer through the structural synergistic optimization of the negative electrode interface layer of the support layer, the heat conduction layer and the buffer layer from the inside to the outside, and the conductive additive. The specific mechanism is as follows:

[0164] 1. Negative electrode interface layer structure innovation:

[0165] (1) Gradient composite film mechanical synergy:

[0166] Supporting layer: The supporting layer with high shear strength makes the performance of the supporting layer close to the performance of silicon carbide ceramic, so that the supporting layer can block the penetration of lithium dendrites;

[0167] Thermal conductivity layer: The thermal conductivity layer with high thermal conductivity has good thermal conductivity performance, which can realize the rapid homogenization of heat of the negative electrode interface layer and avoid the decomposition of the negative electrode interface layer caused by uneven heat distribution;

[0168] Buffer layer: The buffer layer with high elongation at break can match the expansion coefficient of the silicon-based negative electrode matrix and has high stress buffering, thereby improving the mechanical properties of the negative electrode.

[0169] The supporting layer and the thermal conductivity layer are synergistically controlled by mechanics-thermodynamics between the buffer layer, so as to ensure the performance stability and thermal conductivity performance of the negative electrode interface layer.

[0170] (2) Dynamic stability guarantee:

[0171] The three-layer gradient structure negative electrode interface layer can still maintain complete interface contact after multiple cycles, has a low volume change rate, and can avoid the increase of interface impedance caused by interface contact fluctuation.

[0172] 2. Three-dimensional conductive network enhancement:

[0173] (1) Synergistic transmission of vertical layer and horizontal layer:

[0174] The vertical ion channel of the vertical layer can realize a nanoscale ion path;

[0175] The horizontal conductive network of the horizontal layer can greatly reduce the interface impedance of the negative electrode interface layer.

[0176] (2) Interface polarization suppression:

[0177] The three-dimensional network formed by the vertical layer and the horizontal layer can improve the uniformity of current density distribution, so as to effectively eliminate the local charge accumulation of the silicon-based negative electrode matrix.

[0178] 3. Comprehensive performance improvement:

[0179] The structural design of this solid-state battery anode, through the gradient structure of the anode interface layer and multi-scale optimization of conductivity synergy, can improve the interface thermal runaway temperature of the battery, maintain the stability of the interface impedance of the solid-state battery anode, and the interface impedance of the cathode material grows relatively little after multiple cycles.

[0180] In some alternative embodiments, the conductive additive accounts for 4.5% to 5.5% of the total mass of the negative electrode interface layer.

[0181] In these embodiments, a conductive additive comprising 4.5% to 5.5% of the mass of the negative electrode interface layer can introduce a sufficiently continuous three-dimensional composite network structure of electrons and ions into the negative electrode interface layer. Through these three-dimensional composite network structures, the impedance of the negative electrode interface layer can be effectively reduced, thereby improving the stability of the positive electrode interface layer.

[0182] The conductive additive is present in an amount of 4.5%, 4.6%, 4.7%, 4.8%, 4.9%, 5.0%, 5.1%, 5.2%, 5.3%, 5.4%, or 5.5% of the mass of the negative electrode interface layer.

[0183] In some optional embodiments, the total thickness of the negative electrode interface layer is 9 μm to 11 μm, and the density of the thermally conductive layer along the second positive direction is from 2.0 g / cm³. 3 It decreases in a gradient to 0.8 g / cm³. 3 The thickness of the buffer layer along the second positive direction starts from 0.6 g / cm³. 3 The concentration gradually increased to 1.2 g / cm³. 3 .

[0184] In these embodiments, the negative electrode interface layer with a total thickness of 9μm to 11μm can accommodate a sufficient number of three-layer gradient composite negative electrode interface layer structures. These gradient composite film structures can comprehensively improve the stability of the negative electrode interface layer. Furthermore, the buffer layer with a density decreasing gradient from the inside to the outside can form a gradient thermally conductive interface in the negative electrode interface layer, allowing for rapid heat homogenization and preventing heat accumulation that could lead to decomposition of the negative electrode interface layer, thus improving its stability. In addition, the buffer layer with a thickness increasing gradient from the inside to the outside can act as a buffer layer, buffering the expansion deformation of the silicon-based negative electrode substrate, thereby improving the mechanical stability of the negative electrode interface layer. Additionally, the density increases from 2.0 g / cm³ from the inside to the outside. 3 It decreases in a gradient to 0.8 g / cm³. 3 The thermally conductive layer can act as a gradient-distributed thermal interface to quickly dissipate heat from the negative electrode interface layer, preventing heat accumulation and subsequent decomposition. Additionally, the density decreases from 0.6 g / cm³ to the outside. 3 The concentration gradually increased to 1.2 g / cm³. 3The P layer can form a gradient distribution buffer layer, and the layered characteristics can promote the uniform distribution of the buffer property of the buffer layer, can adapt to the expansion deformation trend of the silicon-based negative electrode substrate, and can improve the mechanical property of the negative electrode interface layer.

[0185] The total thickness of the negative electrode interface layer can be 9 μm, 9.5 μm, 10 μm, 10.5 μm, or 11 μm.

[0186] In some optional embodiments, the material of the support layer comprises one or a combination of at least two of polyimide, polybenzimidazole, polyether ether ketone, and silicon carbide reinforced composite; and / or

[0187] The material of the heat conduction layer comprises one or a combination of at least two of boron nitride, graphene nanosheet, and silicon carbide nanowire; and / or

[0188] The material of the buffer layer comprises one or a combination of at least two of polyurethane acrylate, silicone modified polyurethane, and hydrogenated nitrile rubber; and / or

[0189] The material of the vertical layer comprises one or a combination of at least two of carbon nanotube, graphene, and Ketjen black; and / or

[0190] The material of the horizontal layer comprises one or a combination of at least two of graphene, carbon nanofiber, and Ti3C2T x .

[0191] In these embodiments, the support layer formed by one or a combination of at least two of polyimide, polybenzimidazole, polyether ether ketone, and silicon carbide reinforced composite has a high Young's modulus, and the high Young's modulus support layer can act as a support skeleton to improve the mechanical stability of the negative electrode interface layer. In addition, the heat-conducting layer formed by one or a combination of at least two of boron nitride, graphene nanosheet, and silicon carbide nanowire has good thermal conductivity, which can promote the rapid homogenization of heat in the negative electrode interface layer to avoid the decomposition of the negative electrode interface layer, thereby ensuring the stability of the negative electrode interface layer. In addition, the heat-conducting layer also has good chemical inertness, which can avoid the decomposition of the heat-conducting layer at the negative electrode interface to improve the stability of the negative electrode interface layer. In addition, the buffer layer formed by one or a combination of at least two of polyurethane acrylate, silicone-modified polyurethane, and hydrogenated nitrile rubber has high ductility, which can match the expansion deformation of the silicon-based negative electrode matrix to avoid the expansion deformation of the negative electrode material causing damage to the negative electrode interface layer, thereby improving the stability of the negative electrode interface layer. In addition, the buffer layer also has good electrochemical stability, which can resist the corrosion of the electrolyte to improve the stability of the negative electrode interface layer. Furthermore, the buffer layer also has good interface adhesion, which can improve the interface peeling strength to more than 50 N / m to improve the surface stability of the three-layer gradient composite negative electrode interface layer structure on the silicon-based negative electrode matrix. In addition, the vertical layer formed by one or a combination of at least two of carbon nanotubes, graphene, and Ketjenblack can form vertical ion channels in the positive electrode interface layer and the negative electrode interface layer to reduce the impedance of the negative electrode interface layer, avoid the interface polarization phenomenon of the negative electrode interface layer, and improve the stability of the negative electrode interface layer. In addition, the horizontal layer formed by one or a combination of at least two of graphene, carbon nanofiber, and Ti3C2T x xene can provide a good horizontal conductive network for the negative electrode interface layer and form a stable electron-ion double-continuous three-dimensional composite network structure with the vertical layer to further reduce the impedance of the negative electrode interface layer and further improve the stability of the negative electrode interface layer.

[0192] It should be noted that, since the material of the buffer layer involves a non-insulator, in order to avoid the introduction of the buffer layer causing the impedance of the negative electrode interface layer to increase, the support layer and the heat-conducting layer need to have certain electrical conductivity to reduce the impedance of the three-layer gradient composite negative electrode interface layer structure and improve the electrical conductivity of the negative electrode interface layer.

[0193] It should be noted that the electrical conductivity of the support layer and the heat-conducting layer can be greater than 1 x 10 -6 S / cm.

[0194] It should be noted that both the vertical layer and the horizontal layer need to have good chemical inertness to avoid the reaction between the vertical layer and the horizontal layer and the electrolyte causing damage to the negative electrode interface layer and affecting the stability of the interface layer. In addition, the density of the vertical layer is preferably 2 g / cm 3The following makes the vertical layer have a lighter mass, which can promote the uniform distribution of the vertical layer in the negative electrode interface layer, control the distribution range of the vertical ion channel, and further reduce the impedance of the negative electrode interface layer. In addition, the lateral layer also needs good dispersibility, which can form a uniform and stable three-dimensional composite network structure between the lateral layer and the vertical layer, so as to effectively reduce the impedance of the negative electrode interface layer.

[0195] It should be noted that the Ti3C2T x is a two-dimensional transition metal carbide (MXene), which is often used to prepare nanocomposites or as an electrode material, etc. Among them, Ti represents a titanium element, 3 represents that there are 3 titanium atoms in the chemical composition of Ti3C2T x , C represents a carbon element, and T x represents the presence of surface functional groups, which can be hydrogen, oxygen or other functional groups.

[0196] In some optional embodiments, the mass m5 of the material of the support layer, the mass m6 of the material of the heat-conducting layer, and the mass m7 of the material of the buffer layer satisfy: m5:m6:m7=(5-7):(2-4):1; and / or

[0197] The mass m8 of the material of the vertical layer and the mass m9 of the material of the lateral layer satisfy: m8:m9=(2-4):(6-8).

[0198] In these embodiments, the support layer, the heat-conducting layer and the buffer layer with a mass ratio of (5-7):(2-4):1 can promote the negative electrode interface layer to have a support layer with sufficient thickness, a heat-conducting layer with uniform density distribution, and a buffer layer with uniform density distribution. The support layer with sufficient thickness can act as a support skeleton to improve the mechanical properties of the three-layer gradient composite negative electrode interface layer structure. The heat-conducting layer with uniform density distribution can improve the heat-conducting properties of the negative electrode interface layer to maintain the stability of the negative electrode interface layer during use. The buffer layer with uniform density distribution can act as a buffer layer, which can adapt to the swelling deformation trend of the silicon-based negative electrode matrix to improve the mechanical properties of the negative electrode interface layer. In addition, the vertical layer and the lateral layer with a mass ratio of (2-4):(6-8) can form a three-dimensional network with sufficient pores to improve the uniformity of the current density distribution of the negative electrode interface layer, thereby effectively eliminating the local charge accumulation of each interface layer and reducing the impedance of the negative electrode interface layer.

[0199] In some optional embodiments, the shear strength of the support layer is >2.5 GPa, the thermal conductivity of the heat-conducting layer is >400 W / m·K, and the elongation at break of the buffer layer is >150%; and / or

[0200] The conductive property of the transverse layer is > 1000 S / cm.

[0201] In these embodiments, the support layer with a shear strength greater than 2.5 GPa can serve as a support framework, significantly improving the mechanical stability of the negative electrode interface layer. The thermal conductivity of the thermal conductivity layer is greater than 400 W / m·K, which can quickly conduct the heat generated by the silicon-based negative electrode matrix, avoiding the decomposition of the negative electrode interface layer due to heating, thereby improving the thermal stability of the negative electrode interface layer. In addition, the buffer layer with an elongation at break greater than 150% can effectively buffer the expansion deformation of the silicon-based negative electrode matrix during the charging and discharging process, further enhancing the mechanical stability of the negative electrode interface layer. Through the synergistic effect between the support layer, the thermal conductivity layer and the buffer layer, the stability of the negative electrode interface layer is significantly improved.

[0202] Figure 3 An exemplary flow chart of a method for preparing the negative electrode material provided by the embodiments of the present application is shown;

[0203] Based on a general inventive concept, as Figure 3 shown, the embodiments of the present application provide a preparation method of the solid-state battery negative electrode, which comprises:

[0204] S1. Under the action of a magnetic field, the material of the vertical layer and the material of the transverse layer are compounded to construct a three-dimensional composite network structure, to obtain a conductive additive;

[0205] S2. The material of the thermal conductivity layer is mixed with the conductive additive to obtain a negative electrode active paste;

[0206] S3. A support layer is prepared on the silicon-based negative electrode matrix;

[0207] S4. On the surface of the support layer, the negative electrode active paste is gradient coated to obtain a first composite layer containing a support layer and a thermal conductivity layer; wherein the gradient coating comprises increasing extrusion pressure;

[0208] S5. On the surface of the first composite layer containing a support layer and a thermal conductivity layer, the material of the buffer layer is coated to obtain a second composite layer containing a buffer layer, a thermal conductivity layer and a support layer;

[0209] S6. The second composite layer containing a buffer layer, a thermal conductivity layer and a support layer is gradient photocured using increasing light intensity to obtain a solid-state battery negative electrode containing a negative electrode interface layer.

[0210] The preparation method is for the preparation method of the above-mentioned solid-state battery negative electrode. The specific structure of the solid-state battery negative electrode can refer to the above-mentioned embodiments. Since the preparation method adopts part or all of the technical solutions of the above-mentioned embodiments, it at least has all the beneficial effects brought by the technical solutions of the above-mentioned embodiments, which will not be repeated here.

[0211] It should be noted that the preparation method of the support layer can be electrospinning, the voltage of the electrospinning can be 14kV-16kV, the receiving distance of the electrospinning can be 13cm-17cm, and the speed of the electrospinning can be 0.8mL / h-1.2mL / h. The electrospinning at a voltage of 14kV-16kV and a receiving distance of 13cm-17cm can promote the material of the support layer to form a uniform film layer, facilitating the subsequent coating and molding of the negative electrode slurry. In addition, the material of the support layer can be dissolved in an N,N-dimethylformamide solution before electrospinning to form a 10% mass concentration of the material solution of the support layer.

[0212] It should be noted that during the mixing of the material of the heat-conducting layer and the conductive additive, an organic solvent such as ethanol can be added for dispersion, so that the mass concentration of the material of the heat-conducting layer and the conductive additive is maintained at about 5%, and a negative electrode active slurry with uniform dispersion of the material of the heat-conducting layer can be formed.

[0213] It should be noted that the gradient coating method can use micro-embossing printing, which is a reverse reverse intaglio printing technology mainly applied to thin coating (1-80μm) and low viscosity glue (1-1000cps) scenes. Its principle is to use a micro-embossing roller opposite to the movement direction of the substrate to be coated, and to reduce the discontinuous coverage of the coating slurry by the shear force of this reverse movement to improve the uniformity of the formed coating. In order to coat uniformly, the gap of the micro-embossing printing micro-embossing roller can be controlled at about 10μm, and the pressure of the micro-embossing roller can be controlled at about 0.3MPa.

[0214] It should be noted that during the gradient coating of the heat-conducting layer, the pressure variation step of the micro-embossing printing can be adjusted by 0.1MPa (corresponding to the pressure of the next stage of coating being 0.1MPa higher than that of the previous stage of coating), and the corresponding heat-conducting layer has a gradient density variation of 0.03g / cm 3 -0.05g / cm 3 , so that the density of the heat-conducting layer decreases from 2.0g / cm 3 to 0.8g / cm 3 from the inside to the outside.

[0215] It should be noted that after gradient coating, drying at 60°C for 30min is required to stabilize the final heat-conducting layer and ensure that the density of the heat-conducting layer decreases from 2.0g / cm 3 to 0.8g / cm 3 from the inside to the outside.

[0216] It should be noted that the material of the buffer layer is one of polyurethane acrylate, silicone modified polyurethane, hydrogenated butyl nitrile rubber or a combination of at least two of them. In addition to the above materials, the material of the buffer layer can also add a photoinitiator into the prepolymer (generally liquid) of the buffer layer to form a mixed solution with a mass concentration of 2% of the photoinitiator.

[0217] It should be noted that the wavelength of the gradient photocuring can be 360nm-370nm, the intensity of the gradient photocuring

[0218] ≥50mW / cm 2 The time of the gradient photocuring can be 25s-35s. Under the condition of sufficient gradient photocuring intensity, the initiation of the photoinitiator in the prepolymer of the buffer layer containing the photoinitiator can be activated by a specific gradient photocuring wavelength and time, so that the prepolymer of the buffer layer occurs polymerization reaction to form a buffer layer with a specific gradient density distribution, and finally a buffer layer with a density of 0.6g / cm 3 gradually increasing to 1.2g / cm 3 from inside to outside is obtained.

[0219] It should be noted that the illumination intensity of the gradient photocuring can be adjusted in a manner of changing amount step 5mW / cm 2 (corresponding to the illumination intensity of the next stage photocuring being 5mW / cm 2 higher than that of the last stage photocuring), and the gradient density change amount of the buffer layer is 0.08g / cm 3 to 0.12g / cm 3 , so that the density of the buffer layer gradually increases from 0.6g / cm 3 to 1.2g / cm 3 from inside to outside.

[0220] Based on a general inventive concept, the embodiments of the present application provide a battery containing a solid-state electrolyte, a solid-state battery positive electrode, and a solid-state battery negative electrode, the solid-state battery positive electrode and the solid-state battery negative electrode being distributed on both sides of the solid-state electrolyte.

[0221] The battery is realized based on the above-mentioned solid-state battery positive electrode and solid-state battery negative electrode. The specific structure of the solid-state battery positive electrode or solid-state battery negative electrode can refer to the above-mentioned embodiments. Since the battery adopts part or all of the technical solutions of the above-mentioned embodiments, it at least has all the beneficial effects brought by the technical solutions of the above-mentioned embodiments, which will not be repeated here.

[0222] It should be noted that the battery is designed to reduce the interface impedance of the solid-state battery positive electrode and the solid-state battery negative electrode, and effectively improve the overall performance of the battery. Specifically, the positive electrode material of the solid-state battery positive electrode includes nickel-based particles, an inner layer and an outer layer. The nickel-based particles of the positive electrode material are covered with the inner layer and the outer layer. The inner layer has an ionic conductivity greater than 1.2 mS / cm at 25°C. As an efficient ion transmission channel, the inner layer can significantly reduce the impedance of ion migration in the positive electrode material, while having good chemical stability, which can improve the overall stability of the positive electrode material under low impedance conditions. The outer layer has a resistivity greater than 10 8 Ω·cm. The outer layer can effectively suppress the occurrence of positive electrode side reactions and the interface phase transition of the positive electrode material, further improve the chemical stability of the inner layer, and significantly enhance the comprehensive performance of the positive electrode interface layer.

[0223] The solid-state battery negative electrode includes a silicon-based negative electrode matrix and a three-layer gradient composite negative electrode interface layer formed by a support layer, a thermal conductive layer and a buffer layer. The support layer has a shear strength greater than 2.5 GPa and serves as a support skeleton to significantly improve the mechanical stability of the negative electrode interface layer. The thermal conductive layer has a thermal conductivity greater than 400 W / m·K and serves as a thermal conductive layer to quickly conduct the heat generated by the negative electrode material, thereby avoiding decomposition of the interface layer due to heating and improving the thermal stability of the negative electrode interface layer. The buffer layer has an elongation at break greater than 150%, which can effectively buffer the expansion deformation of the silicon-based negative electrode matrix during charging and discharging, further enhancing the mechanical stability of the negative electrode interface layer. Through the synergistic effect of the support layer, the thermal conductive layer and the buffer layer, the impedance of the negative electrode interface layer is significantly reduced, and the stability of the negative electrode interface layer is significantly improved.

[0224] The conductive additive is arranged in the nickel-based particles and the thermal conductive layer, respectively, and uses a three-dimensional composite network structure composed of vertical layers and horizontal layers. The vertical layer is used to ensure ion transmission in the vertical direction of the interface layer and ensure efficient conduction of ions in the interface layer. The horizontal layer is used to provide a horizontal conductive path with a conductivity greater than 1000 S / cm, which can significantly improve the horizontal conductive performance of the positive electrode or negative electrode interface layer. Through the synergistic effect of the vertical layer and the horizontal layer, a complete three-dimensional conductive network is formed, which optimizes the charge transmission path between the electrode material and each interface layer, effectively avoids the occurrence of interface polarization phenomenon, further reduces the impedance of each electrode material, and further improves the stability of the positive electrode interface layer and the negative electrode interface layer.

[0225] It should be noted that the battery can be a lithium ion battery or a sodium ion battery in addition to the solid-state battery.

[0226] The present application is further described below in conjunction with specific examples. The experimental methods in the following examples are generally determined according to the national standard / industry standard unless otherwise specified; if there is no corresponding national standard / industry standard, the general international standard, the conventional condition or the condition suggested by the manufacturer is used.

[0227] Example 1

[0228] As shown in the drawings, a solid-state battery positive electrode comprises: Figure 1

[0229] A positive electrode material, the positive electrode material comprising: nickel-based particles, and an inner layer and an outer layer covering the nickel-based particles, the ion conductivity of the inner layer being greater than the ion conductivity of the outer layer, the electron blocking rate of the inner layer being less than the electron blocking rate of the outer layer, wherein, in the solid-state battery positive electrode, the side of the solid-state battery positive electrode away from the solid-state battery negative electrode is the first positive direction to the side of the solid-state battery positive electrode close to the solid-state battery negative electrode, the thickness of the outer layer is gradiently thinned along the first positive direction; and,

[0230] A conductive additive, the conductive additive comprising a three-dimensional composite network structure composed of vertical layers and horizontal layers, the vertical layers being used for vertical ion transmission, and the horizontal layers being used for horizontal conduction; and,

[0231] The conductive additive is contained in the nickel-based particles.

[0232] The nickel-based particles are nickel-based metal material NCM9;

[0233] The mass of the conductive additive is 4.0% of the mass of the positive electrode material.

[0234] The thickness of the inner layer is 0.2 μm, and the thickness of the outer layer is gradiently thinned from 50 nm to 10 nm along the first positive direction. Specifically, the thickness of the outer layer is 50 nm, 40 nm, 30 nm, 20 nm, and 10 nm in turn from inside to outside.

[0235] The material of the inner layer is tantalum-doped lithium lanthanum zirconium oxide LLZTO;

[0236] The material of the outer layer is lithium phosphorus oxynitride;

[0237] The material of the vertical layer is multi-walled carbon nanotube MWCNT;

[0238] The material of the horizontal layer is graphene.

[0239] The mass m1 of the material of the inner layer and the mass m2 of the material of the outer layer satisfy: m1:m2=7:3;

[0240] The mass m3 of the material of the vertical layer and the mass m4 of the material of the horizontal layer satisfy: m3:m4=3:7.

[0241] ​The material particle size of the inner layer is 100 nm to 350 nm;

[0242] The material particle size of the outer layer is 20 nm to 50 nm;

[0243] The pore size of the vertical layer is 50 nm to 100 nm (at this time, the multi-walled carbon nanotubes of the C layer are vertically arranged);

[0244] The porosity of the three-dimensional composite network structure is 62% to 68%.

[0245] The porosity of the outer layer is < 2%.

[0246] The 25°C ionic conductivity of the inner layer is > 1.2 mS / cm;

[0247] The resistivity of the outer layer is > 10 8 Ω·cm;

[0248] The electrical conductivity of the horizontal layer is > 1000 S / cm.

[0249] The positive electrode material contains a conductive additive.

[0250] As Figure 2 shown, a preparation method of the solid-state battery positive electrode includes:

[0251] S1. Under the action of a magnetic field, the material of the vertical layer and the material of the horizontal layer are compounded to construct a three-dimensional composite network structure, and a conductive additive is obtained;

[0252] S2. The nickel-based particles and the conductive additive are sequentially mixed and dried to obtain a mixed dry material;

[0253] S3. The material of the inner layer is deposited on the surface of the mixed dry material by atomic layer deposition to obtain first composite particles containing nickel-based particles and the inner layer;

[0254] S4. The material of the outer layer is deposited on the surface of the first composite particles by atomic layer deposition to obtain a positive electrode material;

[0255] S5. The positive electrode material, the conductive additive, and a fluorine-containing binder are mixed to prepare a positive electrode slurry; the mass ratio of the positive electrode material, the conductive additive, and the binder is 94:4:2;

[0256] S6. The positive electrode slurry is coated on a positive electrode base material to obtain a solid-state battery positive electrode.

[0257] As Figure 1As shown, a solid-state battery negative electrode comprises: a silicon-based negative electrode base body, and a negative electrode interface layer covering the silicon-based negative electrode base body, so that the side of the solid-state battery negative electrode away from the solid-state battery positive electrode is the second positive direction, and the side of the solid-state battery negative electrode close to the solid-state battery positive electrode is the second positive direction; the negative electrode interface layer comprises a support layer, a heat conduction layer and a buffer layer distributed along the second positive direction; the material density of the heat conduction layer decreases along the second positive direction; and the material density of the buffer layer increases along the second positive direction.

[0258] The heat conduction layer contains an electrically conductive additive, and the electrically conductive additive is a three-dimensional composite network structure composed of vertical layers and horizontal layers; the vertical layers are used for vertical ion transmission; and the horizontal layers are used for horizontal electrical conduction.

[0259] The mass of the electrically conductive additive is 5.0% of the total mass of the negative electrode interface layer.

[0260] The total thickness of the negative electrode interface layer is 10 μm, the thickness of the support layer is 2 μm, the thickness of the heat conduction layer is 3 μm at most, and the density of the heat conduction layer decreases from 2.0 g / cm 3 to 0.8 g / cm 3 along the second positive direction; the thickness of the buffer layer is 5 μm at most, and the density of the buffer layer increases from 0.6 g / cm 3 to 1.2 g / cm 3 along the second positive direction.

[0261] The material of the support layer is polyimide;

[0262] The material of the heat conduction layer is boron nitride;

[0263] The material of the buffer layer is polyurethane acrylate;

[0264] The material of the vertical layer is multi-walled carbon nanotube MWCNT;

[0265] The material of the horizontal layer is graphene.

[0266] The mass m5 of the material of the support layer, the mass m6 of the material of the heat conduction layer and the mass m7 of the material of the buffer layer satisfy: m5:m6:m7=6:3:1;

[0267] The mass m8 of the material of the vertical layer and the mass m9 of the material of the horizontal layer satisfy: m8:m9=3:7.

[0268] The shear strength of the support layer is >2.5 GPa, the thermal conductivity of the heat conduction layer is >400 W / m·K, and the elongation at break of the buffer layer is >150%;

[0269] The electrical conductivity of the horizontal layer is >1000 S / cm.

[0270] As Figure 3As shown, the embodiment of the present application provides a preparation method of a solid-state battery negative electrode, comprising:

[0271] S1. Under the action of a magnetic field, the material of the vertical layer and the material of the horizontal layer are compounded to construct a three-dimensional composite network structure, and a conductive additive is obtained;

[0272] S2. The material of the heat-conducting layer and the conductive additive are mixed to obtain a negative electrode active paste;

[0273] S3. A support layer is prepared on a silicon-based negative electrode substrate;

[0274] S4. On the surface of the support layer, the negative electrode active paste is gradient coated to obtain a first composite layer containing a support layer and a heat-conducting layer; wherein the gradient coating includes increasing extrusion pressure;

[0275] S5. On the surface of the first composite layer containing the support layer and the heat-conducting layer, the material of the buffer layer is coated to obtain a second composite layer containing the buffer layer, the heat-conducting layer and the support layer;

[0276] S6. The second composite layer containing the buffer layer, the heat-conducting layer and the support layer is gradient photocured using increasing light intensity to obtain a solid-state battery negative electrode containing a negative electrode interface layer.

[0277] The preparation of the support layer is carried out in the form of electrospinning, the voltage of electrospinning is 15kV, the receiving distance of electrospinning is 15cm, and the speed of electrospinning is 1.0mL / h.

[0278] The gradient coating is carried out by micro-concave coating printing, the down pressure of the micro-concave roller is initially 0.3MPa, and the gradient pressure coating is carried out according to the pressure change step of 0.1MPa.

[0279] The wavelength of the gradient photocuring is 365nm, the initial light intensity of the gradient photocuring is 50mW / cm 2 , which is increased in the form of change step of 5mW / cm 2 , and the time of the gradient photocuring is 30s.

[0280] The temperature of atomic layer deposition is 180℃; the strength of the magnetic field is 0.5T.

[0281] Example 2

[0282] Compared with Example 1, the differences of the present embodiment are as follows, and the rest are the same:

[0283] The thickness of the inner layer is 0.1μm, and the thickness of the outer layer is gradiently thinned from 50nm to 10nm along the first positive direction. Specifically, the thickness of the outer layer is 50nm, 40nm, 30nm, 20nm and 10nm in turn from inside to outside.

[0284] The mass m1 of the material of the inner layer and the mass m2 of the material of the outer layer satisfy: m1:m2 = 7.5:2.5;

[0285] The mass m3 of the material of the vertical layer and the mass m4 of the material of the horizontal layer satisfy: m3:m4 = 2:8.

[0286] The particle size of the material of the inner layer is 100 nm to 350 nm;

[0287] The particle size of the material of the outer layer is 20 nm to 50 nm;

[0288] The pore size of the vertical layer is 1000 nm to 5000 nm (at this time, the multi-walled carbon nanotubes of the C layer are arranged horizontally, preventing lithium from winding dendrites).

[0289] The total thickness of the negative electrode interface layer is 10 μm, the thickness of the support layer is 2 μm, and the thickness of the heat-conducting layer is at most 3 μm; and the density of the heat-conducting layer is gradually increased from 2.0 g / cm 3 to 0.8 g / cm 3 in the second positive direction; the thickness of the buffer layer is at most 5 μm, and in the buffer layer, the density of the buffer layer is gradually increased from 0.6 g / cm 3 to 1.2 g / cm 3 in the second positive direction.

[0290] The mass m5 of the material of the support layer, the mass m6 of the material of the heat-conducting layer, and the mass m7 of the material of the buffer layer satisfy: m5:m6:m7 = 5:4:1;

[0291] The mass m8 of the material of the vertical layer and the mass m9 of the material of the horizontal layer satisfy: m8:m9 = 2:8.

[0292] Example 3

[0293] Compared with Example 1, the differences of the present embodiment are as follows, and the rest are the same:

[0294] The mass of the conductive additive is 3.5% to 4.5% of the mass of the positive electrode material.

[0295] The thickness of the inner layer is 0.3 μm, and the thickness of the outer layer is gradually reduced from 50 nm to 10 nm in the first positive direction. Specifically, the thickness of the outer layer is 50 nm, 40 nm, 30 nm, 20 nm, and 10 nm in turn from the inside to the outside.

[0296] The material of the inner layer includes one or a combination of at least two of lithium strontium titanate, lithium lanthanum zirconium oxide, tantalum-doped lithium lanthanum zirconium oxide, lithium zirconium phosphate, and a polyethylene oxide-bistrifluoromethanesulfonimide lithium composite system;

[0297] The material of the outer layer comprises one or a combination of at least two of lithium phosphorus oxynitride, lithium phosphate, lithium aluminum oxide, lithium titanate;

[0298] The material of the vertical layer comprises one or a combination of at least two of carbon nanotubes, graphene, Ketjen black;

[0299] The material of the horizontal layer comprises one or a combination of at least two of graphene, carbon nanofiber, Ti3C2T x .

[0300] The mass m1 of the material of the inner layer and the mass m2 of the material of the outer layer satisfy: m1:m2 = 6.5:3.5;

[0301] The mass m3 of the material of the vertical layer and the mass m4 of the material of the horizontal layer satisfy: m3:m4 = 4:6.

[0302] The pore size of the vertical layer is 50nm to 100nm (at this time, the multi-walled carbon nanotubes of the C layer are vertically arranged).

[0303] The total thickness of the negative electrode interface layer is 11μm, the thickness of the support layer is 2μm, and the thickness of the heat conduction layer is at most 4μm; and the density of the heat conduction layer decreases along the second positive direction from 2.0g / cm 3 to 0.8g / cm 3 ; the thickness of the buffer layer is at most 5μm, and in the buffer layer, the density of the buffer layer increases along the second positive direction from 0.6g / cm 3 to 1.2g / cm 3 .

[0304] The mass m5 of the material of the support layer, the mass m6 of the material of the heat conduction layer, and the mass m7 of the material of the buffer layer satisfy: m5:m6:m7 = 7:2:1;

[0305] The mass m8 of the material of the vertical layer and the mass m9 of the material of the horizontal layer satisfy: m8:m9 = 4:6.

[0306] Example 4

[0307] Compared with Example 1, the differences of the present embodiment are as follows, and the rest are the same:

[0308] The material of the inner layer is a mixture of lithium strontium titanate and LLZTO with a mass ratio of 7:3;

[0309] The material of the outer layer is a mixture of lithium phosphate and lithium titanate with a mass ratio of 1:1.

[0310] The material of the support layer is silicon carbide reinforced polyimide (SiC 20wt%);

[0311] The material of the heat-conducting layer is a mixture of boron nitride and silicon carbide nanowires in a mass ratio of 9:1; the material of the P layer is organic silicon modified polyurethane.

[0312] The material of the vertical layer is a mixture of carbon nanotubes MWCNT and Ketjen black in a mass ratio of 1:1;

[0313] The material of the horizontal layer is a mixture of graphene and carbon nanofibers in a mass ratio of 8:2.

[0314] The mass of the conductive additive is 3.5% of the mass of the positive electrode material;

[0315] The mass of the conductive additive is 4.5% of the mass of the negative electrode interface layer.

[0316] Example 5

[0317] Compared with Example 1, the differences of the present embodiment are as follows, and the rest are the same:

[0318] The material of the inner layer is polyethylene oxide-bistrifluoromethanesulfonimide lithium;

[0319] The material of the outer layer is lithium aluminum oxide.

[0320] The material of the support layer is polyether ether ketone;

[0321] The material of the heat-conducting layer is graphene nanosheet; the material of the P layer is hydrogenated nitrile rubber.

[0322] The material of the vertical layer is graphene;

[0323] The material of the horizontal layer is Ti3C2T x .

[0324] The mass of the conductive additive is 4.5% of the mass of the positive electrode material;

[0325] The mass of the conductive additive is 5.5% of the mass of the negative electrode interface layer.

[0326] Example 6

[0327] Compared with Example 1, the differences of the present embodiment are as follows, and the rest are the same:

[0328] The voltage of electrospinning is 14kV, the receiving distance of electrospinning is 13cm, and the speed of electrospinning is 0.7mL / h.

[0329] The wavelength of gradient photocuring is 360nm, and the time of gradient photocuring is 25s.

[0330] The temperature of atomic layer deposition is 170℃; the intensity of the magnetic field is 0.4T.

[0331] Example 7

[0332] Compared with Example 1, the differences of the present example are as follows, and the rest are the same as those of Example 1:

[0333] The electrospinning voltage is 16 kV, the electrospinning receiving distance is 17 cm, and the electrospinning speed is 1.3 mL / h.

[0334] The gradient photocuring wavelength is 370 nm, and the gradient photocuring time is 35 s.

[0335] The atomic layer deposition temperature is 190℃, and the magnetic field strength is 0.6T.

[0336] Comparative Example 1

[0337] Compared with Example 1, the differences of the present example are as follows, and the rest are the same as those of Example 1:

[0338] A single metal oxide interface layer is used as the negative electrode interface layer; the specific process is as follows:

[0339] Lithium lanthanum zirconium oxide (LLZO) with a mass concentration of 12% is coated on the surface of the negative electrode material to obtain a negative electrode material; then the lithium lanthanum zirconium oxide and nickel-based particles are mixed to obtain a mixed slurry; the mixed slurry is coated on the surface of the positive electrode base material to obtain a positive electrode material; finally, the positive electrode material and the negative electrode material are hot-pressed to obtain a composite interface layer.

[0340] Comparative Example 2

[0341] Compared with Example 1, the differences of the present example are as follows, and the rest are the same as those of Example 1:

[0342] A polymer composite interface layer is used as the inner layer and the outer layer of the nickel-based particles, and the polymer composite interface layer is used as the interface layer of the negative electrode material; the specific process is as follows: polyethylene oxide is used as a solution, the solution and ceramic particles are mixed together according to a volume-mass ratio of 3:7 to form a mixture, and then the mixture is cast into a film by a solution casting method to obtain a polymer composite interface layer.

[0343] Comparative Example 3

[0344] Compared with Example 1, the differences of the present example are as follows, and the rest are the same as those of Example 1:

[0345] Only the inner layer and the outer layer structure of the positive electrode material are used, and no negative electrode interface layer is used.

[0346] Comparative Example 4

[0347] Compared with Example 1, the differences of the present example are as follows, and the rest are the same as those of Example 1:

[0348] Only the negative electrode interface layer is used, and no inner layer and outer layer are used in the positive electrode material.

[0349] Comparative Example 5

[0350] Compared with example 1, the differences of the present example are as follows, and the rest are the same as example 1:

[0351] The outer layer does not present gradient change, and the outer layer with uniform thickness is directly used.

[0352] Comparative example 6

[0353] Compared with example 1, the differences of the present example are as follows, and the rest are the same as example 1:

[0354] The thickness of the heat-conducting layer and the buffer layer does not present gradient change, and the heat-conducting layer and the buffer layer with uniform and consistent thickness are directly used.

[0355] Comparative example 7

[0356] Compared with example 1, the differences of the present example are as follows, and the rest are the same as example 1:

[0357] The mass ratio of the positive electrode material, the inner layer and the outer layer is 300:6:4.

[0358] Comparative example 8

[0359] Compared with example 1, the differences of the present example are as follows, and the rest are the same as example 1:

[0360] The mass ratio of the positive electrode material, the inner layer and the outer layer is 400:8:2.

[0361] Comparative example 9

[0362] Compared with example 1, the differences of the present example are as follows, and the rest are the same as example 1:

[0363] The mass m5 of the material of the support layer, the mass m6 of the material of the heat-conducting layer and the mass m7 of the material of the buffer layer satisfy: m5:m6:m7=4:1:1.

[0364] Comparative example 10

[0365] Compared with example 1, the differences of the present example are as follows, and the rest are the same as example 1:

[0366] The mass m5 of the material of the support layer, the mass m6 of the material of the heat-conducting layer and the mass m7 of the material of the buffer layer satisfy: m5:m6:m7=15:5:1.

[0367] Comparative example 11

[0368] Compared with example 1, the differences of the present example are as follows, and the rest are the same as example 1:

[0369] The mass m8 of the material of the vertical layer and the mass m9 of the material of the horizontal layer satisfy: m8:m9=1:10.

[0370] Comparative example 12

[0371] The difference between this embodiment and Example 1 is as follows, and the rest is the same as Example 1:

[0372] The mass m8 of the material of the vertical layer and the mass m9 of the material of the horizontal layer satisfy: m8:m9 = 5:5.

[0373] Comparative Example 13

[0374] The difference between this embodiment and Example 1 is as follows, and the rest is the same as Example 1:

[0375] The mass of the conductive additive is 3.0% of the mass of the positive electrode material.

[0376] Comparative Example 14

[0377] The difference between this embodiment and Example 1 is as follows, and the rest is the same as Example 1:

[0378] The mass of the conductive additive is 5.0% of the mass of the positive electrode material.

[0379] Comparative Example 15

[0380] The difference between this embodiment and Example 1 is as follows, and the rest is the same as Example 1:

[0381] The mass of the conductive additive is 4.0% of the mass of the negative electrode interface layer.

[0382] Comparative Example 16

[0383] The difference between this embodiment and Example 1 is as follows, and the rest is the same as Example 1:

[0384] The mass of the conductive additive is 6.0% of the mass of the negative electrode interface layer.

[0385] Related experiments and effect data:

[0386] I. Related experiments:

[0387] 1. The positive electrode of the solid-state battery and the negative electrode of the solid-state battery obtained in each embodiment and comparative example were collected respectively, and the direct current resistance DCR was measured according to the standard of GB / T31467.3, then the crack density of the positive electrode of the solid-state battery and the negative electrode of the solid-state battery after 500 cycles was recorded and measured in a scanning electron microscope according to the standard of GB / T 27788, then the amount of Li2CO3 generated during the cycle was measured according to the standard of ISO 15472, and the thermal runaway trigger temperature was measured according to the standard of GB 38031-2020, and the final results are shown in Table 1. The results are shown in Table 1.

[0388] Table 1 Interface impedance and crack density of the positive electrode of the solid-state battery and the negative electrode of the solid-state battery in each embodiment and comparative example

[0389]

[0390]

[0391] 2. The solid-state battery positive electrode of Example 1, Comparative Example 7 and Comparative Example 8 were collected respectively, and the ion conductivity was measured according to Gamry standard and EIS method, and the interface impedance was detected at the same time, and the results are shown in Table 2.

[0392] Table 2 Ion conductivity and interface impedance of the solid-state battery positive electrode of Example 1, Comparative Example 7 and Comparative Example 8

[0393]

[0394] 3. Based on the solid-state battery positive electrode and the solid-state battery negative electrode prepared in Example 1, the SiOx / C negative electrode material was used, and the oxide electrolyte or the polymer electrolyte was used, and the results are shown in Table 3.

[0395] Table 3 Material compatibility results table

[0396]

[0397] II. Data analysis:

[0398] As shown in Table 1, the solid-state battery positive electrode provided by the present application has a stable interface layer, and the crack density is controlled to be less than 100 / mm 2 below, and the thermal runaway trigger temperature is increased to above 200℃, and the amount of byproduct Li2CO3 is effectively reduced to less than 1%, and the direct current internal resistance is reduced to less than 2.0mΩ.

[0399] In addition, the solid-state battery negative electrode provided by the present application uses the negative electrode interface layer formed by the support layer, the heat conduction layer and the buffer layer, and the negative electrode interface layer has high stability, and the crack density is controlled to be less than 100 / mm 2 below after multiple cycles, and in addition, the negative electrode interface layer can increase the thermal runaway trigger temperature of the solid-state battery negative electrode to above 200℃, and effectively reduce the amount of byproduct Li2CO3 to less than 1%, and reduce the direct current internal resistance to less than 2.0mΩ.

[0400] As can be seen from Table 2, the mass ratio of the inner layer and the outer layer is maintained in the range of (6.5 to 7.5):(3.5 to 2.5) to ensure that the solid-state battery positive electrode has sufficient ion conductivity (1.2 mS / cm) and sufficiently low interface impedance, and if the mass ratio is less than 6.5:3.5, it will cause the ion transport of the solid-state battery positive electrode to be limited, affecting the ion conductivity. If the mass ratio is higher than 7.5:2.5, it will cause the interface impedance of the solid-state battery positive electrode to increase, ultimately affecting the performance of the battery.

[0401] As can be seen from Table 3, the battery provided by the embodiment of the present application uses a specific inner layer and outer layer to form a positive electrode interface layer in the solid-state battery positive electrode, which can effectively inhibit the Ni dissolution of the nickel-based positive electrode material, and the capacity retention rate of the battery is stable at more than 95% after 500 cycles, compared with the retention rate (82%) of the traditional positive electrode material. In addition, the battery uses a specific support layer, heat-conducting layer and buffer layer to form a negative electrode interface layer in the solid-state battery negative electrode, which can buffer the expansion of the silicon-based negative electrode matrix, and can effectively reduce the negative electrode volume expansion rate to less than 15%, compared with the expansion rate (>40%) of the traditional silicon-based negative electrode matrix. In addition, the solid-state battery positive electrode and the solid-state battery negative electrode in the battery have good compatibility with the electrolyte, which can ensure that the interface impedance fluctuation in the entire battery is less than 5%.

[0402] In summary, the solid-state battery positive electrode provided by the embodiment of the present application has a structure optimization of the inner layer and the outer layer on the nickel-based particles, supplemented by the structure optimization of the conductive additive, which significantly reduces the impedance of the interface layer of the positive electrode material and improves the chemical and mechanical stability of the solid-state battery positive electrode. The average direct current internal resistance of the solid-state battery positive electrode is less than 2.0 mΩ, and the crack density can be controlled to be less than 100 / mm 2 In the following, the thermal runaway trigger temperature is increased to more than 200°C, and the interface stability is good.

[0403] The solid-state battery negative electrode provided by the embodiment of the present application has a structure synergistic optimization of the support layer, heat-conducting layer and buffer layer of the negative electrode interface layer from the inside to the outside, and the conductive additive, which significantly reduces the impedance of the negative electrode interface and improves the chemical and mechanical stability of the negative electrode interface layer. The average direct current internal resistance of the solid-state battery negative electrode is less than 2.0 mΩ, and the crack density can be controlled to be less than 100 / mm 2 In the following, the thermal runaway trigger temperature is increased to more than 200°C, and the interface stability is good.

[0404] In addition, the battery provided by the embodiment of the present application can reduce the generation amount of the byproduct Li2CO3 to less than 1%, so that the interface layer of the solid-state battery positive electrode and the interface layer of the solid-state battery negative electrode in the battery have a lower interface side reaction.

[0405] In addition, the battery provided by the embodiment of the present application can include a plurality of battery products, such as lithium ion batteries, sodium ion batteries and solid-state batteries, based on the characteristics of the above-mentioned solid-state battery positive electrode and solid-state battery negative electrode. These battery products can be widely used in the new energy industry.

[0406] The above description is merely a detailed implementation of the present application, which enables those skilled in the art to understand or implement the present application. Various modifications to these embodiments will be apparent to those skilled in the art, and the general principles defined in the present application can be implemented in other embodiments without departing from the spirit or scope of the present application. Therefore, the present application will not be limited to these embodiments shown in the present application, but will conform to the widest scope consistent with the principles and novel features of the present application.

Claims

1. A solid-state battery positive electrode, characterized in that, The solid-state battery cathode includes: A positive electrode material, comprising: nickel-based particles, and an inner layer and an outer layer covering the nickel-based particles, wherein the ionic conductivity of the inner layer is greater than that of the outer layer, and the electron blocking rate of the inner layer is less than that of the outer layer, wherein, in the solid-state battery positive electrode, a first positive direction is defined as the direction from the side of the solid-state battery positive electrode away from the solid-state battery negative electrode towards the side of the solid-state battery positive electrode closer to the solid-state battery negative electrode, and the thickness of the outer layer decreases gradually along the first positive direction; and, A conductive additive comprising a three-dimensional composite network structure consisting of vertical and horizontal layers, wherein the vertical layers are used for vertical ion transport and the horizontal layers are used for lateral conductivity; and, The nickel-based particles contain the conductive additive.

2. The solid-state battery positive electrode according to claim 1, characterized in that, The mass of the conductive additive is 3.5% to 4.5% of the mass of the positive electrode material.

3. The solid-state battery positive electrode according to claim 1, characterized in that, The thickness of the inner layer is 0.1 μm to 0.3 μm, and the thickness of the outer layer gradually decreases from 50 nm to 10 nm along the first positive direction.

4. The cathode material according to claim 1, characterized in that, The inner layer material comprises one or a combination of at least two of the following: lithium strontium titanate, lithium lanthanum zirconium oxide, tantalum-doped lithium lanthanum zirconium oxide, lithium zirconium phosphate, and lithium ethylene oxide-bis(trifluoromethanesulfonyl)imide composite system; and / or The outer layer material comprises one or a combination of at least two of lithium phosphorus oxynitride, lithium phosphate, lithium aluminum oxide, and lithium titanate; and / or The material of the vertical layer includes one or a combination of at least two of carbon nanotubes, graphene, and Ketjen Black; and / or The materials of the transverse layer include graphene, carbon nanofibers, and Ti3C2T. x One or at least two of them.

5. The solid-state battery positive electrode according to claim 1, characterized in that, The mass m1 of the inner layer material and the mass m2 of the outer layer material satisfy: m1:m2 = (6.5 to 7.5):(2.5 to 3.5); and / or The mass m3 of the material in the vertical layer and the mass m4 of the material in the horizontal layer satisfy the following: m3:m4 = (2 to 4):(6 to 8).

6. The solid-state battery cathode according to claim 1, characterized in that, The inner layer material has a particle size of 100 nm to 350 nm; and / or The outer layer material has a particle size of 20 nm to 50 nm.

7. The solid-state battery positive electrode according to claim 1, characterized in that, The aperture of the vertical layer is 50 nm to 5000 nm; The porosity of the three-dimensional composite network structure is 62% to 68%.

8. The solid-state battery positive electrode according to claim 1, characterized in that, The inner layer has an ionic conductivity of >1.2 mS / cm at 25°C; and / or The resistivity of the outer layer is >10. 8 Ω·cm; and / or The conductivity of the lateral layer is >1000 S / cm.

9. The solid-state battery positive electrode according to claim 1, characterized in that, The positive electrode of the solid-state battery also includes a positive electrode substrate, and the positive electrode material covers the positive electrode substrate material.

10. The solid-state battery cathode according to claim 1, characterized in that, The positive electrode material contains the conductive additive.

11. A method for preparing a solid-state battery cathode as described in any one of claims 1 to 10, characterized in that, The preparation method includes: Under the influence of a magnetic field, the materials of the vertical layer and the horizontal layer are combined to construct a three-dimensional composite network structure, thereby obtaining a conductive additive. The nickel-based particles and the conductive additive are mixed and dried sequentially to obtain a mixed dry material; An inner layer material is deposited on the surface of the mixed dry material using atomic layer deposition to obtain a first composite particle containing nickel-based particles and an inner layer. The outer layer material is deposited on the surface of the first composite particle using atomic layer deposition to obtain the cathode material; The cathode material is prepared into a cathode slurry; The positive electrode slurry is coated onto the positive electrode substrate material to obtain a solid-state battery positive electrode; In the solid-state battery positive electrode, the first positive direction is defined as the side of the solid-state battery positive electrode away from the solid-state battery negative electrode and the side of the solid-state battery positive electrode closer to the solid-state battery negative electrode. The thickness of the outer layer decreases in a gradient along the first positive direction.

12. A solid-state battery negative electrode, comprising: A silicon-based negative electrode substrate and a negative electrode interface layer covering the silicon-based negative electrode substrate, with the side of the solid-state battery negative electrode away from the solid-state battery positive electrode and the side of the solid-state battery negative electrode closer to the solid-state battery positive electrode as the second positive direction, the negative electrode interface layer includes a support layer, a thermally conductive layer and a buffer layer distributed along the second positive direction, the material density of the thermally conductive layer decreases along the second positive direction, and the material density of the buffer layer increases along the second positive direction; The thermally conductive layer contains a conductive additive, which is a three-dimensional composite network structure composed of vertical and horizontal layers. The vertical layer is used for ion transport in the vertical direction, and the horizontal layer is used for lateral conductivity.

13. The solid-state battery negative electrode according to claim 12, characterized in that, The mass of the conductive additive is 4.5% to 5.5% of the total mass of the negative electrode interface layer.

14. The solid-state battery negative electrode according to claim 12, characterized in that, The total thickness of the negative electrode interface layer is 9 μm to 11 μm, and the density of the thermally conductive layer along the second positive direction is from 2.0 g / cm³. 3 The gradient was reduced to 0.8 g / cm³. 3 The density of the buffer layer along the second positive direction is 0.6 g / cm³. 3 It increased to 1.2 g / cm³. 3 .

15. The solid-state battery negative electrode according to claim 12, characterized in that, The material of the support layer includes one or a combination of at least two of polyimide, polybenzimidazole, polyetheretherketone, and silicon carbide reinforced composite materials; and / or The thermally conductive layer is made of one or a combination of at least two of boron nitride, graphene nanosheets, and silicon carbide nanowires; and / or The material of the buffer layer includes one or a combination of at least two of polyurethane acrylate, silicone-modified polyurethane, and hydrogenated nitrile rubber; and / or The material of the vertical layer includes one or a combination of at least two of carbon nanotubes, graphene, and Ketjen Black; and / or The materials of the transverse layer include graphene, carbon nanofibers, and Ti3C2T. x One or at least two of them.

16. The solid-state battery negative electrode according to claim 12, characterized in that, The mass m5 of the material of the support layer, the mass m6 of the material of the thermally conductive layer, and the mass m7 of the material of the buffer layer satisfy: m5:m6:m7 = (5 to 7):(2 to 4):1; and / or The mass m8 of the material in the vertical layer and the mass m9 of the material in the horizontal layer satisfy the following: m8:m9 = (2 to 4):(6 to 8).

17. The solid-state battery negative electrode according to claim 12, characterized in that, The shear strength of the supporting layer is >2.5 GPa, the thermal conductivity of the thermally conductive layer is >400 W / m·K, and the elongation at break of the buffer layer is >150%; and / or The conductivity of the lateral layer is >1000 S / cm.

18. A method for preparing a solid-state battery negative electrode as described in any one of claims 12 to 17, the method comprising: Under the influence of a magnetic field, the materials of the vertical layer and the horizontal layer are combined to construct a three-dimensional composite network structure, thereby obtaining a conductive additive. The thermally conductive layer material and the conductive additive are mixed to obtain the negative electrode active slurry; A support layer is prepared on a silicon-based anode substrate; On the surface of the support layer, the negative electrode active slurry is gradient coated to obtain a first composite layer containing a support layer and a thermally conductive layer; wherein, the gradient coating is performed with increasing extrusion pressure; On the surface of the first composite layer containing the support layer and the thermally conductive layer, the material of the buffer layer is coated to obtain a second composite layer containing the buffer layer, the thermally conductive layer and the support layer. The second composite layer, containing a buffer layer, a thermally conductive layer, and a support layer, is subjected to gradient photocuring using increasing light intensity to obtain a negative electrode material containing a negative electrode interface layer.

19. A battery comprising a solid electrolyte, a solid battery positive electrode as claimed in any one of claims 1 to 10, and a solid battery negative electrode as claimed in any one of claims 12 to 17, wherein the solid battery positive electrode and the solid battery negative electrode are distributed on both sides of the solid electrolyte.

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