Composite solid electrolyte, preparation method thereof and solid-state battery

Abstract

The invention relates to the technical field of batteries, in particular to a composite solid electrolyte, a preparation method thereof and a solid-state battery. The provided composite solid electrolyte comprises a polyanionic compound and a sulfide electrolyte, and the polyanionic compound is arranged between sulfide electrolyte particles and is used for filling gaps; the polyanionic compound comprises a compound containing phosphate radical, lithium and halogen. A solid state battery includes the provided composite solid electrolyte. The lithium dendrite problem can be relieved, the short circuit risk of the battery can be reduced, the solid-state battery such as an all-solid-state lithium metal battery can achieve long circulation without short circuit, and the circulation stability of the solid-state battery is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of batteries, and in particular, to a composite solid electrolyte, a preparation method thereof, and a solid-state battery. Background Art

[0002] In batteries such as lithium-ion batteries, the liquid electrolyte is inherently highly flammable, and the insufficient battery safety caused by the risk of ignition and combustion, that is, the volatile, flammable and explosive organic electrolyte is the main factor causing the safety problems of lithium-ion batteries; in addition, the energy density of currently commercially available liquid lithium batteries is difficult to exceed 300 Wh / kg. As the next-generation lithium battery technology, solid-state batteries have outstanding advantages such as good safety and high energy density on the basis of inheriting the advantages of traditional lithium batteries. All-solid-state batteries use solid electrolytes to replace the organic electrolytes in traditional secondary lithium-ion batteries, fundamentally solving the long-standing safety problems of lithium-ion batteries. In addition, by matching a lithium metal anode with a high theoretical specific capacity (3860 mAh·g -1 ) and a low reduction potential (-3.04 V vs. standard hydrogen electrode), and based on the structural characteristics of the battery pack with an in-series connection, all-solid-state lithium metal batteries can theoretically break through the energy density limit of existing secondary energy storage devices, and thus can meet the endurance requirements of next-generation electronic devices.

[0003] Currently, the electrolytes of all-solid-state lithium metal batteries include oxides, sulfides, halides, nitrides, hydrides, and polymers. Among them, sulfide solid electrolytes have attracted much attention in the industry and academia due to their ultra-high ionic conductivity (10 -3 ~10 -2 S·cm -1 ) and the characteristics of being soft and easy to process. However, the compatibility between sulfide solid electrolytes and lithium metal anodes is not ideal, and there will be problems with lithium dendrites. The existence of lithium dendrites is likely to cause short-circuit problems.

[0004] Therefore, developing a solution to prevent the formation of lithium dendrites in sulfide solid electrolytes is of great significance for the development and application of all-solid-state lithium metal batteries. Summary of the Invention

[0005] In view of this, the present invention aims to at least partly solve one of the technical problems in the related art. For this reason, the present invention provides a composite solid electrolyte, a preparation method thereof, and a solid-state battery, which can alleviate the problem of lithium dendrites and help reduce the risk of battery short circuits.

[0006] To solve the above technical problems, the present application is implemented as follows:

[0007] According to one aspect of the present application, embodiments of the present application provide a composite solid electrolyte, which includes: a polyanion compound and a sulfide electrolyte, and the polyanion compound is disposed between the sulfide electrolyte particles for interstitial filling;

[0008] The polyanion compound includes a compound containing phosphate, lithium, and halogen.

[0009] In addition, the composite solid electrolyte according to the present application may further have the following additional technical features:

[0010] In some embodiments, the chemical general formula of the polyanion compound is xLi3PO4-MX4;

[0011] Wherein, x satisfies: 0.2 ≤ x ≤ 3; M includes transition metal elements; X includes halogen.

[0012] In some embodiments, x satisfies: 0.5 ≤ x ≤ 2.

[0013] In some embodiments, M includes at least one of Zr, Hf, or Ti. Preferably, M is selected from any one or a combination of at least two of Zr and Hf.

[0014] In some embodiments, X includes at least one of Cl, Br, or I. Preferably, X is selected from any one or a combination of at least two of Cl and Br.

[0015] In some embodiments, the chemical general formula of the sulfide electrolyte is Li 6-y PS 5-y Cl 1+y ;

[0016] Wherein, y satisfies: 0 ≤ y ≤ 1. Preferably, y satisfies: 0.2 ≤ y ≤ 0.7.

[0017] In some embodiments, the mass percentage of the polyanion compound in the composite solid electrolyte is 1% - 30%. Preferably, the mass percentage of the polyanion compound in the composite solid electrolyte is 5% - 20%.

[0018] In some embodiments, the mass percentage of the sulfide electrolyte in the composite solid electrolyte is 70% - 99%. Preferably, the mass percentage of the sulfide electrolyte in the composite solid electrolyte is 80% - 95%

[0019] In some of these embodiments, the median particle size of the polyanion compound is 100 nm to 800 nm. Preferably, the median particle size of the polyanion compound is 200 nm to 600 nm.

[0020] In some of these embodiments, the median particle size of the sulfide electrolyte is 3 μm to 10 μm.

[0021] According to another aspect of the present application, embodiments of the present application provide a method for preparing a composite solid electrolyte, the method comprising: mixing a polyanion compound and a sulfide electrolyte to obtain a first material; wherein the polyanion compound comprises a compound containing phosphate, lithium, and a halogen;

[0022] Performing ball milling on the first material to obtain the composite solid electrolyte.

[0023] In some of these embodiments, the preparation method satisfies at least one of the following characteristics:

[0024] (1) The mass ratio of the polyanion compound to the sulfide electrolyte is (1 to 30):(70 to 99);

[0025] (2) The mixing is performed by ball milling using a planetary ball mill;

[0026] (3) The rotation speed of the ball milling is 50 to 500 rpm, preferably 100 to 450 rpm;

[0027] (4) The time of the ball milling is 10 min to 180 min, preferably 15 min to 60 min.

[0028] According to still another aspect of the present application, embodiments of the present application provide a solid-state battery, the solid-state battery comprising a positive electrode sheet, a solid electrolyte layer, and a negative electrode sheet, wherein at least one of the positive electrode sheet, the solid electrolyte layer, and the negative electrode sheet contains the aforementioned composite solid electrolyte, and / or contains the composite solid electrolyte prepared by the aforementioned preparation method.

[0029] In some of these embodiments, the solid-state battery satisfies at least one of the following characteristics:

[0030] (1) The solid-state battery includes a lithium metal solid-state battery;

[0031] (2) The negative electrode sheet includes metallic lithium;

[0032] (3) The positive electrode sheet includes a positive electrode material, and the positive electrode material includes at least one of a ternary material, lithium cobaltate, sulfur, or a sulfur-containing compound;

[0033] (4) The positive electrode sheet includes the composite solid electrolyte described above;

[0034] (5) The solid electrolyte layer includes the composite solid electrolyte described above;

[0035] (6) The solid electrolyte layer includes the composite solid electrolyte and a binder, and the mass ratio of the composite solid electrolyte to the binder is (95 - 99):(1 - 5).

[0036] Implementing the technical solution of the present invention has at least the following beneficial effects:

[0037] In this application, the provided composite solid electrolyte includes a polyanion compound and a sulfide electrolyte, and the polyanion compound is disposed between the sulfide electrolyte particles for interstitial filling. The present invention utilizes the characteristics that the polyanion compound has no grain boundaries, high cold pressing density, good mechanical properties, and it is difficult for lithium dendrites to form a complete path in the polyanion compound during cycling. The polyanion compound is used as a filler to fill the native cracks in the sulfide electrolyte. Furthermore, the obtained composite solid electrolyte containing the polyanion compound and the sulfide electrolyte has excellent mechanical strength, has good compatibility with the lithium metal anode while ensuring its ionic conductivity, effectively inhibits the growth of lithium dendrites in the solid electrolyte layer, thereby alleviating the problem of lithium dendrites, enabling solid-state batteries such as all-solid-state lithium metal batteries to achieve long cycling without short circuit, and making the performance of solid-state batteries more stable during cycling.

[0038] The additional aspects and advantages of this application will be partially given in the following description, partially become apparent from the following description, or be understood through the practice of the present invention. Detailed Embodiments

[0039] The following further elaborates on this application in conjunction with specific embodiments. It should be understood that these embodiments of this application are only used to illustrate this application and not to limit the scope of this application.

[0040] In the ranges disclosed herein, the endpoints and any values are not limited to the exact ranges or values. These ranges or values should be understood to include values close to these ranges or values. For numerical ranges, between the endpoint values of each range, between the endpoint values or individual point values of each range, and between individual point values, they can be combined with each other to obtain one or more new numerical ranges, and these numerical ranges should be regarded as specifically disclosed herein.

[0041] If not specifically stated, "including" and "comprising" mentioned in this application mean open-ended, and can also be closed-ended. For example, "including" and "comprising" can mean that other components not listed can also be included or comprised, or it can only include or comprise the listed components.

[0042] As described in the background art, although sulfide solid electrolytes have ultra-high ionic conductivity (10 -3 ~10 -2 S.cm -1 ), and are soft and easy to process, sulfide solid electrolytes still have the problem of unsatisfactory compatibility with lithium metal anodes, mainly including: (1) During the deposition of lithium metal, due to reasons such as the electrochemical stability of the sulfide solid electrolyte or the action of external pressure, it will grow along the grain boundaries and gaps in the sulfide solid electrolyte layer. (2) The soft texture of sulfide and its decomposition products is not conducive to preventing the formation and growth of dendrites. When the grown lithium dendrites form a path in the electrolyte layer, it will cause a sudden drop in the working voltage of the battery and the battery will fail. Therefore, developing a solution to prevent the generation of lithium dendrites in sulfide solid electrolytes is of great significance for the development and application of all-solid-state lithium metal batteries.

[0043] In view of this, based on the above problems existing in the existing sulfide solid electrolytes in the all-solid-state battery system. The inventors of this application have provided a solid electrolyte material obtained by compounding a polyanion electrolyte (polyanion compound) with a sulfide electrolyte, its preparation method and application. The provided solid electrolyte material obtained by compounding a polyanion electrolyte with a sulfide electrolyte has excellent comprehensive performance, which helps to improve the limiting current density of the lithium metal solid battery and reduce the probability of short circuit, thereby realizing the commercial application value of all-solid-state secondary batteries. The description of the specific technical solution is as follows.

[0044] In a first aspect, in some embodiments, a composite solid electrolyte is provided. The provided composite solid electrolyte includes: a polyanion compound and a sulfide electrolyte, and the polyanion compound is disposed between the sulfide electrolyte particles for interstitial filling;

[0045] The polyanion compound includes a compound containing a phosphate group, lithium, and a halogen.

[0046] In this application, the composite solid electrolyte is mainly composed of a polyanion compound and a sulfide electrolyte, so that the composite solid electrolyte combines the excellent properties of both the sulfide electrolyte and the polyanion electrolyte, enabling the composite solid electrolyte to have both excellent ionic conductivity and mechanical strength, and having good compatibility with the lithium metal anode while ensuring its ionic conductivity. Among them, the polyanion compound can also be referred to as a polyanion electrolyte.

[0047] Preferably, the polyanion compound is a nanoscale polyanion compound.

[0048] The above polyanion compound preferably contains a phosphate group, and may further contain lithium and a halogen, and may further contain a non-lithium metal element, such as a transition metal element, etc.

[0049] The above-mentioned halogen can be, for example, one or more of fluorine, chlorine, bromine, and iodine.

[0050] The above-mentioned polyanion compound is provided between the sulfide electrolyte particles for interstice filling, which means that the polyanion compound can fill or be filled at the solid-solid particle interface of the sulfide electrolyte. The interstice filling here can be filling voids or gaps.

[0051] It should be understood that there are certain voids between traditional sulfide electrolyte particles. That is to say, when sulfide electrolyte particles contact each other, it is equivalent to multiple relatively large spherical substances (micrometer-scale substances) contacting each other, leaving voids (pores), and the polyanion compound filled with nanoparticles can reduce the pores.

[0052] In order to alleviate the chemical instability of the existing sulfide solid electrolyte to the lithium metal anode, the high-valence cations (P 5+ , Ge 4+ , Sn 4+ etc.) in the sulfide solid electrolyte are easily reduced by lithium metal, generating interfacial by-products with low ionic conductivity, resulting in an increase in the internal resistance of the battery and a decrease in the Coulomb efficiency of lithium metal. And in order to alleviate the problem of battery failure caused by the growth of lithium dendrites. For example, during the deposition of lithium metal, due to reasons such as the intrinsic electronic conductivity of the sulfide solid electrolyte or the action of external pressure, etc., it will grow along the grain boundaries, defects, and cracks in the sulfide solid electrolyte layer. When the grown lithium dendrites form a path in the electrolyte layer, it will cause a sudden drop in the working voltage of the battery and battery failure. The present invention provides a composite solid electrolyte material composed of a polyanion electrolyte and a sulfide electrolyte. The nano-scale, soft and highly conductive polyanion electrolyte is filled at the solid-solid particle interface of the sulfide electrolyte to improve the contact between the solid-solid particles of the electrolyte, achieve fast ion transport and high density, and because of the phosphate group of the polyanion electrolyte-containing, Li3PO4 formed in situ by reacting with lithium metal has relatively high mechanical strength to prevent the growth of lithium metal. Therefore, the composite solid electrolyte material provided by the present invention has excellent comprehensive performance, which helps to increase the limiting current density of the lithium metal solid battery, reduce the short-circuit probability, and thus realize the commercial application value of the all-solid-state secondary battery.

[0053] Thus, the provided composite solid electrolyte material has excellent mechanical strength, has good compatibility with the lithium metal anode while ensuring its ionic conductivity, and effectively inhibits the growth of lithium dendrites in the solid electrolyte layer.

[0054] In some embodiments, the chemical general formula of the polyanion compound is xLi3PO4-MX4; wherein, x satisfies: 0.2≤x≤3; M includes transition metal elements; X includes halogens.

[0055] The polyanion compound containing phosphate groups, lithium, halogens and transition metal elements used in the present invention has the advantage of high electrolyte conductivity, and the side reaction product Li3PO4 of the polyanion compound has strong rigidity, which can play a role in inhibiting lithium dendrites.

[0056] Compared with conventional polymer electrolytes, the present invention creatively proposes to use the xLi3PO4-MX4 polyanion compound; by virtue of the characteristics that the polyanion compound has no grain boundaries, high cold pressing density, good mechanical properties, and it is difficult for lithium dendrites to form a complete path in the polyanion solid electrolyte during cycling, the polyanion solid electrolyte is used as a filler to fill the original cracks in the sulfide electrolyte layer. Furthermore, the composite solid electrolyte has excellent mechanical strength, and while ensuring its ionic conductivity, it has good compatibility with the lithium metal anode, effectively inhibiting the growth of lithium dendrites in the solid electrolyte layer.

[0057] In the above polyanion compound xLi3PO4-MX4, x is 0.2 to 3, for example, it can be 0.2, 0.3, 0.5, 0.6, 0.8, 1, 1.2, 1.5, 2, 2.5, 3 or within the range composed of any two of the above values.

[0058] Preferably, x satisfies: 0.5≤x≤2. By controlling the range of x within the above preferred range, it helps the polyanion compound to have characteristics such as high conductivity and good mechanical properties.

[0059] In the above polyanion compound xLi3PO4-MX4, M includes transition metal elements; in some embodiments, M includes but is not limited to at least one of zirconium (Zr), hafnium (Hf) or titanium (Ti); as an example, M can be Zr, can be Hf, can be Ti, can be Zr and Hf, can be Zr and Ti, can be Hf and Ti, or can be Zr, Hf and Ti.

[0060] Preferably, M is selected from any one or a combination of at least two of Zr or Hf.

[0061] The inventors of the present application found through screening a large number of metal elements that halides composed of any several elements among Zr, Hf and Ti can react with Li3PO4 to form an electrolyte with high conductivity and soft texture, thereby enabling the polyanion compound to have characteristics such as high conductivity and soft texture.

[0062] In the above polyanion compound xLi3PO4-MX4, X includes halogens; in some embodiments, X includes but is not limited to at least one of Cl, Br, or I. As an example, X can be Cl, can be Br, can be I, can be Cl and Br, can be Cl and I, can be Br and I, or can be Cl, Br, and I.

[0063] Preferably, X is selected from any one or a combination of at least two of Cl and Br.

[0064] By selecting the above several halogens, the prepared polyanion compound can have extremely high conductivity and moderate hardness.

[0065] In some embodiments, the chemical general formula of the sulfide electrolyte is Li 6-y PS 5-y Cl 1+y ; where y satisfies: 0 ≤ y ≤ 1.

[0066] The chemical general formula adopted in the present invention is Li 6-y PS 5-y Cl 1+y The sulfide electrolyte is the system with the highest conductivity among current sulfide electrolytes, and has high elemental abundance and is easy to obtain.

[0067] In addition, this application is not limited to the sulfide electrolyte of the above chemical formula, and other known sulfide electrolyte materials that can be used as solid electrolytes for solid-state batteries can also be used in this application.

[0068] In the above Li 6-y PS 5-y Cl 1+y In the sulfide electrolyte, y ranges from 0 to 1, for example, it can be 0, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1 or within the range composed of any two of the above values.

[0069] Preferably, y satisfies: 0.2 ≤ y ≤ 0.7. By controlling the range of y within the above preferred range, it helps the sulfide electrolyte to have characteristics such as high conductivity and good mechanical properties.

[0070] In some embodiments, the mass ratio of the polyanion compound in the composite solid electrolyte is 1% - 30%. As an example, the mass ratio of the polyanion compound in the composite solid electrolyte is any one of 1%, 2%, 5%, 10%, 15%, 20%, 25%, 30% or the range value between any two of them.

[0071] Preferably, the mass ratio of the polyanion compound in the composite solid electrolyte is 5% - 20%.

[0072] In some embodiments, the mass percentage of the sulfide electrolyte in the composite solid electrolyte is 70% to 99%. As an example, the mass percentage of the sulfide electrolyte in the composite solid electrolyte is any one of the point values of 70%, 75%, 80%, 85%, 90%, 92%, 95%, 96%, 98%, 99% or the range value between any two of them.

[0073] Preferably, the mass percentage of the sulfide electrolyte in the composite solid electrolyte is 80% to 95%.

[0074] By controlling the content ranges of the polyanion compound and the sulfide electrolyte within the above suitable ranges, the excellent properties of both the polyanion compound and the sulfide electrolyte can be fully combined, enabling the composite solid electrolyte to simultaneously have excellent ionic conductivity, which not only improves the ion migration and diffusion rate but also enhances the mechanical strength of the electrolyte, and has good compatibility with the lithium metal anode while ensuring its ionic conductivity, effectively inhibiting the growth of lithium dendrites in the solid electrolyte layer.

[0075] In some embodiments, the median particle size of the polyanion compound is 100 nm to 800 nm. As an example, the median particle size of the polyanion compound is any one of the point values of 100 nm, 200 nm, 300 nm, 400 nm, 500 nm, 600 nm, 700 nm, 800 nm or the range value between any two of them.

[0076] Preferably, the median particle size of the polyanion compound is 200 nm to 600 nm.

[0077] In the present application, the polyanion compound used is preferably a nanoscale material, and more preferably within the above suitable particle size range, which can ensure the conductivity of the polyanion compound and can effectively fill the voids of the sulfide electrolyte. If the median particle size of the polyanion compound is too small, the conductivity of the polyanion compound is low, increasing the interface; if the median particle size of the polyanion compound is too large, the voids of the sulfide electrolyte cannot be effectively filled.

[0078] In some embodiments, the median particle size of the sulfide electrolyte is 3 μm to 10 μm. As an example, the median particle size of the sulfide electrolyte is any one of the point values of 3 μm, 4 μm, 5 μm, 6 μm, 7 μm, 8 μm, 9 μm, 10 μm or the range value between any two of them.

[0079] Preferably, the median particle size of the sulfide electrolyte is 4 μm to 9 μm.

[0080] In the present application, the sulfide electrolyte employed is preferably micron-sized particles. By controlling the particle size of the sulfide electrolyte within the above-mentioned suitable range, the ionic conductivity of the sulfide electrolyte can be ensured, as well as the film-forming performance. If the particle size of the sulfide electrolyte is too small, the ionic conductivity of the sulfide electrolyte will be low. If the particle size of the sulfide electrolyte is too large, the film-forming performance will be affected and the film-forming performance will be poor.

[0081] Thus, based on the above settings, the design of the composite solid electrolyte material of the present invention can fill the native cracks in the high ionic conductivity sulfide electrolyte layer with the high ionic conductivity and low rigidity component xLi3PO4-MX4. Moreover, the provided composite solid electrolyte material has excellent mechanical strength, has good compatibility with the lithium metal anode while ensuring its ionic conductivity, effectively inhibits the growth of lithium dendrites in the solid electrolyte layer, thereby significantly reducing the risk of battery short circuit; furthermore, it helps to improve the safety and reliability of all-solid-state batteries and promotes their wide application in the new energy field. The composite solid electrolyte material provided by the present invention is expected to match the lithium metal anode and form good mechanical contact to achieve excellent cycle performance and rate performance.

[0082] In a second aspect, in some embodiments, a method for preparing the composite solid electrolyte according to the first aspect is provided. The method includes:

[0083] Mixing a polyanion compound and a sulfide electrolyte to obtain a first material; wherein, the polyanion compound includes a compound containing phosphate groups, lithium, and halogens;

[0084] Performing ball milling on the first material to obtain the composite solid electrolyte.

[0085] The preparation method of the present invention mechanically mixes and uniformly disperses a polyanion solid electrolyte and a sulfide electrolyte. The obtained polyanion-sulfide composite solid electrolyte material has excellent mechanical strength, has good compatibility with the lithium metal anode while ensuring its ionic conductivity, and effectively inhibits the growth of lithium dendrites in the solid electrolyte layer.

[0086] The method of the present invention has the characteristics of short process time, high efficiency, and low preparation cost.

[0087] The method of the present invention realizes the composite of electrolyte materials by simple mechanical mixing, and fills the electrolyte component of xLi3PO4-MX4 of the polyanion compound at the interface of sulfide electrolyte particles under relatively mild synthesis conditions. The reaction conditions of the method of the present invention are relatively mild, the process flow is simplified, it is easy to prepare in large quantities, and it is suitable for industrial production.

[0088] It should be understood that the "method for preparing a composite solid electrolyte" and the aforementioned "composite solid electrolyte" are based on the same inventive concept. All the features and advantages described for the "composite solid electrolyte" in the previous text also apply to the "method for preparing a composite solid electrolyte", and will not be elaborated one by one here.

[0089] In some specific embodiments, the method for preparing the composite solid electrolyte includes the following steps (a) and (b):

[0090] Step (a): Prepare the first material.

[0091] In step (a), the following raw materials are weighed according to a certain mass ratio: a polyanion compound and a sulfide electrolyte, and they are mixed to obtain the first material.

[0092] Optionally, the mixing in step (a) can be carried out by ball milling with a planetary ball mill.

[0093] Exemplarily, the following raw materials are weighed according to a certain mass ratio: a polyanion compound and a sulfide electrolyte, added to a ball milling tank for sealing treatment, and ball milled with a planetary ball mill to obtain the first material.

[0094] Optionally, in step (a), the mass ratio of the polyanion compound to the sulfide electrolyte is (1 - 30):(70 - 99).

[0095] Step (b): Prepare the composite solid electrolyte.

[0096] In step (b), the above first material is ball milled to obtain the composite solid electrolyte.

[0097] Exemplarily, the first material is mechanically ball milled at a certain rotation speed to obtain a uniformly mixed polyanion-sulfide composite solid electrolyte.

[0098] Optionally, in step (b), the rotation speed of the ball milling treatment is 50 - 500 rpm; preferably, the rotation speed of the ball milling treatment is 100 - 450 rpm. As an example, the rotation speed of the ball milling treatment is any one of the point values of 50 rpm, 100 rpm, 200 rpm, 300 rpm, 350 rpm, 400 rpm, 450 rpm, 500 rpm or the range value between any two of them.

[0099] Optionally, in step (b), the ball milling time is 10 min to 180 min; preferably, the ball milling time is 15 min to 60 min. As an example, the ball milling time is any one of the point values of 10 min, 15 min, 20 min, 25 min, 30 min, 40 min, 50 min, 60 min, 100 min, 120 min, 180 min or the range value between any two of them.

[0100] Therefore, based on the above settings, the inventors of the present application creatively proposed a composite solid electrolyte and its preparation method. The prepared composite solid electrolyte material has excellent mechanical strength, has good compatibility with the lithium metal anode while ensuring its ionic conductivity, effectively inhibits the growth of lithium dendrites in the solid electrolyte layer, and the all-solid-state lithium metal battery assembled with this new composite solid electrolyte can operate stably under high current and large capacity working conditions.

[0101] In a third aspect, in some embodiments, a solid-state battery is provided. The solid-state battery includes a positive electrode sheet, a solid electrolyte layer, and a negative electrode sheet, and the solid electrolyte layer is located between the positive electrode sheet and the negative electrode sheet; at least one of the positive electrode sheet, the solid electrolyte layer, and the negative electrode sheet contains the aforementioned composite solid electrolyte, and / or contains the composite solid electrolyte prepared by the aforementioned preparation method.

[0102] Optionally, the solid-state battery can be an all-solid-state lithium metal battery.

[0103] The composite solid electrolyte provided by the embodiments of the present invention can be applied in solid-state batteries, further can be applied in all-solid-state batteries, and further can be applied in all-solid-state lithium metal batteries.

[0104] In this solid-state battery, the solid electrolyte layer can contain the composite solid electrolyte provided in any of the above embodiments of the present application to alleviate the lithium dendrite problem and improve the safety of the solid-state battery.

[0105] In this solid-state battery, at least one of the positive electrode sheet or the negative electrode sheet can also contain the composite solid electrolyte provided in any of the above embodiments of the present application. As an example, the positive electrode sheet includes a positive electrode film layer, and the positive electrode film layer contains the above composite solid electrolyte. By adding the composite solid electrolyte material to the positive electrode film layer, the lithium ion transport in the electrode such as the positive electrode can be improved by the addition of the composite solid electrolyte material.

[0106] In this solid-state battery, the negative electrode sheet includes metallic lithium;

[0107] The negative electrode sheet of the present application can be a lithium metal negative electrode. As an example, in some instances, a copper-lithium composite tape can be used as the negative electrode sheet.

[0108] In some embodiments, in a solid-state battery, the positive electrode sheet includes a positive electrode current collector and a positive electrode film layer disposed on at least one surface of the positive electrode current collector. As an example, the positive electrode current collector has two surfaces opposite to each other in its own thickness direction, and the positive electrode film layer is disposed on the two opposite surfaces of the positive electrode current collector. It can be understood that the positive electrode film layer can also be stacked on any one of the two surfaces of the positive electrode current collector.

[0109] The present application does not particularly limit the material of the positive electrode current collector, as long as the purpose of the present application can be achieved, and it can be selected according to actual needs. For example, in some embodiments, the positive electrode current collector can be aluminum, nickel, stainless steel, iron, titanium or carbon, and the shape is foil-like or mesh-like. Of course, in other embodiments, a composite current collector (such as an aluminum-carbon composite current collector or a current collector composite of a polymer and a metal) can also be used.

[0110] In some embodiments, the positive electrode material in the positive electrode film layer of the positive electrode sheet includes any one or at least two combinations of a ternary material (such as an NCM ternary material), lithium cobaltate, sulfur element or a sulfur-containing compound.

[0111] Preferably, the positive electrode material is selected from NCM ternary materials.

[0112] In some embodiments, in the positive electrode sheet, the positive electrode film layer includes a positive electrode material, an electrolyte material, a conductive agent and a binder; wherein, the electrolyte material is the composite solid electrolyte provided in any one of the above embodiments of the present application. By adding the electrolyte material to the positive electrode film layer, the present application can improve the lithium ion transport in the electrode such as the positive electrode through the addition of the electrolyte material.

[0113] It should be noted that in this embodiment, the specific materials, structures, etc. of the positive electrode current collector and the positive electrode film layer in the positive electrode sheet are not limited, and the positive electrode structures and components known to those skilled in the art that can be used in solid-state batteries can be selected.

[0114] In some embodiments, in a solid-state battery, the solid electrolyte layer includes the composite solid electrolyte provided in any one of the above embodiments of the present application.

[0115] Based on different types of solid-state batteries, in some cases, when applied in a film-based solid battery, the solid electrolyte layer can be made only of the above composite solid electrolyte, such as by applying a certain pressure to the composite solid electrolyte to form a solid electrolyte layer by pressure molding.

[0116] Or, in some other cases, when applied in a soft-pack solid-state battery, the solid electrolyte layer can include the above composite solid electrolyte and a binder.

[0117] Optionally, when the solid electrolyte layer comprises a composite solid electrolyte and a binder, the mass ratio of the composite solid electrolyte to the binder is (95-99):(1-5). Preferably, the mass ratio of the composite solid electrolyte to the binder is (97-98):(2-3).

[0118] Since the solid-state battery provided by the embodiment of the present invention adopts all the technical solutions of the above embodiment, it has at least all the beneficial effects brought by the technical solutions of the above embodiment, which will not be elaborated one by one here.

[0119] For a better understanding of the present invention, the following will elaborate on the specific implementation process of the present invention in detail with specific implementation manners. The implementation manners described below are exemplary and are only used to explain the present application and should not be construed as a limitation to the present application. For those without specific technologies or conditions indicated in the implementation manners, they shall be carried out according to the technologies or conditions described in the literature in the art or according to the product specifications.

[0120] Example 1

[0121] Preparation of the composite solid electrolyte, including the following steps:

[0122] (a) In a glove box protected by an inert atmosphere, weigh a polyanion compound and a sulfide electrolyte according to a mass ratio of 9:91, and mix to obtain a first material;

[0123] (b) Perform ball milling and mixing on the first material by mechanical ball milling. The rotation speed of the ball milling is 350 rpm, and the ball milling time is 20 minutes to obtain a uniformly mixed polyanion-sulfide composite solid electrolyte.

[0124] The prepared composite solid electrolyte, the polyanion-sulfide composite solid electrolyte, contains a polyanion compound and a sulfide electrolyte. The chemical formula of the polyanion compound is 1.2Li3PO4-HfCl4; the chemical formula of the sulfide electrolyte is Li 5.5 PS 4.5 Cl 1.5 .

[0125] Example 2

[0126] The difference between Example 2 and Example 1 is that:

[0127] The chemical formula of the polyanion compound is 1.2Li3PO4-ZrCl4;

[0128] The rest are the same as in Example 1.

[0129] Example 3

[0130] The difference between Example 3 and Example 2 is that:

[0131] The chemical formula of the sulfide electrolyte is Li 5.2 PS 4.8 Cl 1.2 .

[0132] The rest are the same as in Example 2.

[0133] Example 4

[0134] The difference between Example 4 and Example 2 is that:

[0135] The chemical formula of the sulfide electrolyte is Li 5.3 PS 4.3 Cl 1.7 .

[0136] The rest are the same as in Example 2.

[0137] Example 5

[0138] The difference between Example 5 and Example 2 is that:

[0139] The chemical formula of the polyanion compound is 0.5Li3PO4-ZrCl4;

[0140] The rest are the same as in Example 2.

[0141] Example 6

[0142] The difference between Example 6 and Example 2 is that:

[0143] The chemical formula of the polyanion compound is 2Li3PO4-ZrCl4;

[0144] The rest are the same as in Example 2.

[0145] Example 7

[0146] The difference between Example 7 and Example 2 is that:

[0147] The chemical formula of the polyanion compound is 1.2Li3PO4-Hf 0.5 Zr 0.5 Cl4; The rest are the same as in Example 2.

[0148] Example 8

[0149] The difference between Example 8 and Example 2 is that:

[0150] The chemical formula of the polyanion compound is 1.2Li3PO4-HfBr4;

[0151] The rest are the same as in Example 2.

[0152] Example 9

[0153] Example 9 is different from Example 2 in that:

[0154] The chemical formula of the polyanion compound is 1.2Li3PO4-ZrCl3Br;

[0155] The rest are the same as in Example 2.

[0156] Example 10

[0157] Example 10 is different from Example 2 in that:

[0158] The mass ratio of the polyanion compound to the sulfide electrolyte is 5:95. The rest are the same as in Example 2.

[0159] Example 11

[0160] Example 11 is different from Example 2 in that:

[0161] The mass ratio of the polyanion compound to the sulfide electrolyte is 20:80.

[0162] The rest are the same as in Example 2.

[0163] Comparative Example 1

[0164] Comparative Example 1 is different from Example 2 in that:

[0165] This comparative example provides a solid electrolyte, which is a single type (a single sulfide electrolyte), and the components of the solid electrolyte are Li 5.8 PS 4.8 Cl 1.2 .

[0166] Comparative Example 2

[0167] Comparative Example 2 is different from Example 2 in that:

[0168] This comparative example provides a solid electrolyte, which is a single type (a single sulfide electrolyte), and the components of the solid electrolyte are Li 5.5 PS 4.5 Cl 1.5 .

[0169] Performance Test

[0170] 1. The solid electrolytes obtained in the above examples and comparative examples were tested for ionic conductivity and density.

[0171] The solid electrolytes prepared in Examples 1 to 11 and Comparative Examples 1 to 2 above were respectively tested for ionic conductivity and density, specifically including:

[0172] Weigh 100 mg of polyanion-sulfide composite solid electrolyte (or the solid electrolyte of the comparative example) powder and place it inside the mold for pressing. Apply a pressure of 300 MPa to the electrolyte powder for pressing. Under the pressure application state, use an electrochemical workstation (Solarton1260) and adopt the electrochemical impedance measurement method to measure the impedance value of the electrolyte material at room temperature (25 °C). Take the real value of the impedance at the measurement point with the smallest absolute value of the phase of multiple impedances as the resistance value R of the electrolyte material with respect to ion conduction. SE Using this resistance value, based on the formula σ = (R SE × S / t) -1 , calculate the ionic conductivity. Where σ is the ionic conductivity, RSE is the resistance value of the measured electrolyte material, S is the surface area of the electrolyte material under pressure, and t is the thickness of the electrolyte material under pressure.

[0173] Measure the thickness of the electrolyte sheet using a micrometer, calculate the actual density of the electrolyte sheet, and compare it with its theoretical density to obtain its relative density.

[0174] The test results are shown in Table 1 below.

[0175] 2. Conduct performance tests on the negative electrode stability and lithium dendrite inhibition ability of the solid electrolytes obtained in the above examples and comparative examples.

[0176] Conduct critical current density and cut-off capacity tests on the solid electrolytes prepared in Examples 1-11 and Comparative Examples 1-2 above, respectively, specifically including:

[0177] Through a tablet press, press the obtained polyanion-sulfide composite solid electrolyte powder (or the solid electrolyte of the comparative example) into a thin sheet under a pressure of 300 MPa. Fix lithium copper composite tapes with a lithium thickness of 50 μm on both sides of the thin sheet to form a sandwich structure. Conduct constant current charge and discharge cycle tests and critical current density tests to verify the negative electrode stability and lithium dendrite inhibition ability of the obtained composite solid electrolyte.

[0178] The test results are shown in Table 2.

[0179] 3. Assemble the solid electrolytes obtained in the above examples and comparative examples into solid-state batteries and conduct cycle performance tests.

[0180] (1) Assemble the solid electrolytes prepared in Examples 1-11 and Comparative Examples 1-2 above into solid-state batteries, including:

[0181] Under an argon atmosphere, the solid electrolyte and NCM811 cathode material prepared in the examples or comparative examples were weighed in a ratio of 25:75, and they were uniformly mixed to obtain a composite cathode material. In an insulating test sleeve with a diameter of 10 mm, 100 mg of the composite solid electrolyte prepared in the above examples or comparative examples was added, a pressure of 300 MPa was applied and held for 2 min, and the solid electrolyte layer was formed. 20 mg of the obtained composite cathode material was poured onto one side of the pressed electrolyte layer, a pressure of 360 MPa was applied and held for 5 min to form, and carbon-coated aluminum foil was added as the positive current collector. A lithium-copper composite tape with a lithium thickness of 50 μm was installed on the other side of the electrolyte layer, and a pressure of 80 MPa was applied to form. The positive composite layer, solid electrolyte layer, lithium-copper composite tape and stainless steel columns on both sides form a test all-solid-state battery.

[0182] The assembled all-solid-state battery pack was placed in an incubator at 25 °C, and the cycle performance of the battery was tested. The test conditions were a current density of 0.8 mA cm -2 The cycle charge and discharge performance of the solid-state battery was tested. The voltage range was set to 2.7 - 4.3 V (Li + / Li) during the test process.

[0183] The test results are shown in Table 3.

[0184] Table 1 Test results of the solid electrolytes in each example and comparative example

[0185]

[0186]

[0187] Table 2 Test results of the solid electrolytes in each example and comparative example

[0188]

[0189]

[0190] Table 3 Test results of the all-solid-state batteries containing the solid electrolytes in each example and comparative example

[0191]

[0192] As can be seen from Tables 1 to 3, compared with Comparative Examples 1 to 2, the composite solid electrolytes prepared in Examples 1 to 11 of the present invention have higher ionic conductivity and density, and have higher critical current density and cut-off capacity, indicating that the prepared composite solid electrolytes have higher negative electrode stability and more excellent lithium dendrite inhibition ability. This shows that the composite solid electrolyte material provided by the present invention has excellent mechanical strength, has good compatibility with the lithium negative electrode while ensuring its ionic conductivity, and can effectively inhibit the growth of lithium dendrites in the solid electrolyte layer.

[0193] In addition, compared with Comparative Examples 1 to 2, the solid-state batteries containing the composite solid electrolytes prepared in Examples 1 to 11 of the present invention have better rate performance and capacity retention rate during charge and discharge, improving the performance such as the cycle performance and rate performance of the battery. This shows that the composite solid electrolyte material provided by the present invention can match the lithium metal negative electrode, form good mechanical contact, and achieve excellent cycle performance and rate performance.

[0194] The parts not described in detail in the present invention are well-known technologies to those skilled in the art.

[0195] The basic principles of the present invention have been described above in conjunction with specific embodiments. However, it should be noted that the advantages, advantages, effects, etc. mentioned in the present invention are only examples and not limitations, and it cannot be considered that these advantages, advantages, effects, etc. are essential for each embodiment of the present invention. In addition, the above-disclosed specific details are only for the purpose of illustration and easy understanding, rather than limitations. The above details do not limit the present invention to necessarily adopt the above specific details to implement.

[0196] It should be noted that the term "and / or" or " / " used herein is only a description of the association relationship of the associated objects, indicating that there can be three relationships. For example, A and / or B can represent: A exists alone, A and B exist simultaneously, and B exists alone. The singular forms of "a", "the" and "said" used in the embodiments of the present invention and the appended claims are also intended to include the plural forms unless the context clearly indicates otherwise.

[0197] In the specific embodiments and claims, a list of items connected by the terms "at least one of", "at least one in", "at least one kind in" or other similar terms may mean any combination of the listed items. For example, if items A and B are listed, then the phrase "at least one of A, B" means only A; only B; or A and B. In another example, if items A, B, and C are listed, then the phrase "at least one of A, B, C" means only A; or only B; only C; A and B (excluding C); A and C (excluding B); B and C (excluding A); or all of A, B, and C. Item A may include a single element or multiple elements. Item B may include a single element or multiple elements. Item C may include a single element or multiple elements.

[0198] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that they can still modify the technical solutions described in the foregoing embodiments, or perform equivalent replacements on some of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the various embodiments of the present invention.

Claims

1. A composite solid electrolyte, characterized in that, The composite solid electrolyte includes: a polyanion compound and a sulfide electrolyte, and the polyanion compound is disposed between the sulfide electrolyte particles for interstitial filling; The polyanion compound includes a compound containing phosphate, lithium, and a halogen.

2. The composite solid electrolyte according to claim 1, wherein, The chemical general formula of the polyanion compound is xLi3PO4-MX4; Wherein, x satisfies: 0.2 ≤ x ≤ 3; M includes transition metal elements; X includes halogens.

3. The composite solid electrolyte according to claim 2, characterized in that, x satisfies: 0.5 ≤ x ≤ 2; And / or, M includes at least one of Zr, Hf, or Ti; And / or, X includes at least one of Cl, Br, or I.

4. The composite solid electrolyte according to claim 1, characterized in that, The chemical general formula of the sulfide electrolyte is Li 6-y PS 5-y Cl 1+y ; Wherein, y satisfies: 0 ≤ y ≤ 1.

5. The composite solid electrolyte according to any one of claims 1 to 4, characterized in that, The mass ratio of the polyanion compound in the composite solid electrolyte is 1% to 30%; And / or, the mass ratio of the sulfide electrolyte in the composite solid electrolyte is 70% to 99%.

6. The composite solid electrolyte according to any one of claims 1 to 4, characterized in that, The median particle size of the polyanion compound is 100 nm to 800 nm; And / or, the median particle size of the sulfide electrolyte is 3 μm to 10 μm.

7. A method for preparing a composite solid electrolyte, characterized in that, The method includes: Mixing a polyanion compound and a sulfide electrolyte to obtain a first material; wherein, the polyanion compound includes a compound containing phosphate, lithium, and a halogen; Performing ball milling on the first material to obtain the composite solid electrolyte.

8. The preparation method of the composite solid electrolyte according to claim 7, wherein, The preparation method satisfies at least one of the following characteristics: (1) The mass ratio of the polyanion compound to the sulfide electrolyte is (1 to 30):(70 to 99); (2) The mixing is performed by ball milling with a planetary ball mill; (3) The rotation speed of the ball milling is 50 to 500 rpm; (4) The time of the ball milling is 10 min to 180 min.

9. A solid-state battery, characterized in that, The solid-state battery includes a positive electrode sheet, a solid electrolyte layer, and a negative electrode sheet. At least one of the positive electrode sheet, the solid electrolyte layer, and the negative electrode sheet contains the composite solid electrolyte according to any one of claims 1 to 6, and / or contains the composite solid electrolyte prepared by the preparation method according to any one of claims 7 to 8.

10. The solid-state battery according to claim 9, characterized in that, The solid-state battery satisfies at least one of the following characteristics: (1) The solid-state battery includes a lithium metal solid-state battery; (2) The negative electrode sheet includes metallic lithium; (3) The positive electrode sheet includes a positive electrode material, and the positive electrode material includes at least one of a ternary material, lithium cobaltate, sulfur, or a sulfur-containing compound; (4) The positive electrode sheet includes the composite solid electrolyte; (5) The solid electrolyte layer includes the composite solid electrolyte; (6) The solid electrolyte layer includes the composite solid electrolyte and a binder, and the mass ratio of the composite solid electrolyte to the binder is (95 to 99):(1 to 5).

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