WO2021008360A1

WO2021008360A1 - Sulfide solid-state electrolyte sheet and preparation method therefor, battery containing solid-state electrolyte sheet, and device

Info

Publication number: WO2021008360A1
Application number: PCT/CN2020/099496
Authority: WO
Inventors: 梁成都; 刘成勇; 胡波兵; 郭永胜; 李谦; 付佳玮; 程萌
Original assignee: 宁德时代新能源科技股份有限公司
Priority date: 2019-07-16
Filing date: 2020-06-30
Publication date: 2021-01-21
Also published as: CN112242555A; CN112242555B

Abstract

The present application relates to a sulfide solid-state electrolyte sheet and a preparation method therefor, a battery containing the solid-state electrolyte sheet, and a device. Specifically, the sulfide solid-state electrolyte sheet provided by the present application comprises a sulfide electrolyte material and boron element with which the sulfide electrolyte material is doped; the relative deviation (B ₀-B ₁₀₀)/B ₀ between the boron element mass concentration B ₀ at any position on the surface of the electrolyte sheet and the boron element mass concentration B ₁₀₀ at a distance of 100 μm from said position does not exceed 20%. In the present application, the boron element introduced to the sulfide solid-state electrolyte can effectively reduce the binding effect of anions on lithium ions, and improve the transmission capacity of lithium ions; the boron element is uniformly distributed in the sulfide solid-state electrolyte, the doping uniformity and conductivity of the solid-state electrolyte are both improved, and the surface roughness of the solid-state electrolyte sheet is significantly ameliorated, thereby facilitating diffusion of lithium ions in the sulfide solid-state electrolyte sheet and lithium metal anode interface, reducing the interfacial resistance, and improving the battery cycle performance.

Description

Sulfide solid electrolyte sheet and preparation method thereof, battery and device containing the solid electrolyte sheet

This application claims the priority of the Chinese patent application CN 201910641267.1 entitled "A sulfide solid electrolyte sheet and its preparation method" filed on July 16, 2019, the entire content of which is incorporated herein by reference.

Technical field

This application relates to the field of batteries, in particular to a sulfide solid electrolyte sheet and a preparation method thereof, and also to a battery and a device containing the sulfide solid electrolyte sheet.

Background technique

In recent years, with the rapid development of consumer electronic equipment and electric vehicle industries, lithium-ion batteries have become the most widely used secondary battery technology in social life. However, with the rapid growth in the number of lithium battery products, negative news about the smoke, fire and even explosion of lithium batteries is endless. The safety and energy density of lithium ion batteries need to be improved.

Traditional liquid lithium batteries are difficult to avoid battery safety accidents due to the volatile and flammable characteristics of the liquid electrolyte itself. Therefore, solid electrolytes have attracted attention as an electrolyte replacement product with higher safety performance. The existing solid electrolytes can be divided into three categories according to the material system: sulfide solid electrolytes, oxide solid electrolytes and polymer solid electrolytes. Among them, the sulfide solid electrolyte is also one of the most promising solid electrolyte systems because of its ionic conductivity comparable to that of liquid electrolytes and the processing characteristics of easier shaping and densification at room temperature. However, the existing sulfide solid electrolytes still have problems such as low ion conductivity, and the sulfide solid state batteries also need to improve the energy density and cycle performance.

Summary of the invention

In view of the problems existing in the prior art, the purpose of this application is to provide a sulfide solid electrolyte sheet and a preparation method thereof to improve the conductivity of the solid electrolyte sheet and the energy density and cycle performance of the battery, and contain the sulfide Batteries and devices with solid electrolyte sheets.

In order to achieve the above objective, the first aspect of the present application provides a sulfide solid electrolyte sheet, which comprises a sulfide electrolyte material and a boron element doped in the sulfide electrolyte material, and the surface of the solid electrolyte sheet is arbitrary The relative deviation (B ₀ -B ₁₀₀ )/B ₀ of the boron element mass concentration at the position B ₀ and the boron element mass concentration B ₁₀₀ at a distance of 100 μm from the surface of the solid electrolyte sheet to the position is not more than 20%, preferably (B ₀ -B ₁₀₀ )/B ₀ does not exceed 10%.

The second aspect of the application provides a method for preparing the sulfide solid electrolyte sheet according to the first aspect of the application, including:

Obtain an initial reaction mixture containing sulfide electrolyte raw materials and organic solvents;

Obtain a modified solution containing borate and organic solvent;

Mixing the initial reaction mixture with the modification solution and drying to obtain an initial product;

The initial product is subjected to more than one post-treatment, and each post-treatment sequentially includes the steps of grinding, cold pressing and sintering.

The third aspect of the application provides an all-solid-state lithium ion battery, which is prepared by the sulfide solid electrolyte sheet according to the first aspect of the application or the sulfide solid electrolyte sheet prepared according to the preparation method according to the second aspect of the application Prepared.

The fourth aspect of the present application provides a laminated all-solid-state lithium ion battery, including a positive pole piece, a solid electrolyte sheet and a negative pole piece; wherein the solid electrolyte sheet is the sulfide described in the first aspect of the application A solid electrolyte sheet or a sulfide solid electrolyte sheet prepared according to the preparation method described in the second aspect of the application.

A fifth aspect of the present application provides a device, including the all-solid-state lithium ion battery described in the third aspect of the present application or the laminated all-solid-state lithium ion battery described in the fourth aspect of the present application.

Compared with the prior art, this application includes at least the following beneficial effects:

In the embodiment of the application, borate is used as the doping raw material to modify the sulfide solid electrolyte. The doping of B element can reduce the binding effect of anions on lithium ions and improve the transmission capacity of lithium ions; O element is partially doped Substitution of S element can not only produce mixed anion effect to improve lithium ion conductivity, but also inhibit the formation of space charge layer at the interface between oxide cathode and sulfide electrolyte, and reduce the interface impedance; and the borate introduced in the doping process acts as Lewis Acid, with 2P empty orbital, can form a complex with the electron donor of the sulfide electrolyte material, promote the full reaction of the sulfide electrolyte material and the doping material, and improve the doping uniformity and conductivity of the reaction product.

The inventor believes that in the doping modification process of the solid electrolyte, if the raw material of the sulfide electrolyte is directly mixed with the cation or anion inorganic compound (such as boron sulfide) that needs to be doped, the heat treatment is caused due to the solid state between the inorganic particles. For contact problems, this mixing method is difficult to achieve a uniform dispersion effect, and it is easy to cause the formation of impurity phases during raw material mixing and heat treatment. However, the present application utilizes the property of borate to form a uniformly dispersed solution in the solvent to realize the full mixing of the electrolyte raw materials and the borate to be doped. In addition, the borate can be completely decomposed at the phase forming temperature of the sulfide electrolyte, thereby reducing the introduction of impurities or residual reactants, so that the ionic conductivity of the prepared sulfide solid electrolyte is significantly improved, which is beneficial to the complete The energy density of solid-state lithium-ion batteries is exerted.

Further, the inventor also believes that during the heat treatment process for preparing the sulfide solid electrolyte, the volatilization of the solvent and the decomposition of the organic borate will cause damage to the structure of the electrolyte sheet and poor contact between particles, thereby affecting doping. The diffusion process of elements in the solid electrolyte. Therefore, the present application achieves sufficient diffusion and uniform distribution of the modified element in the electrolyte material through repeated grinding, cold pressing and sintering processes, and finally uniform doping of boron element Sulfide electrolyte sheet.

Therefore, in the solid electrolyte sheet of the embodiment of the present application, on the one hand, due to the introduction of boron element, the binding effect of anions on lithium ions is effectively reduced, and the transmission capacity of lithium ions is improved; on the other hand, due to the boron element in the solid electrolyte sheet It not only improves the doping uniformity and conductivity of the solid electrolyte sheet, but also significantly improves the surface roughness of the solid electrolyte sheet, which is beneficial to the diffusion process of lithium ions at the interface between the electrolyte sheet and the lithium metal anode. Reduce interface impedance and improve battery cycle performance.

Description of the drawings

Fig. 1 is an XRD test pattern of a solid electrolyte according to an embodiment of the present application;

2 is a graph of Raman test results of a solid electrolyte according to an embodiment of the present application;

FIG. 3 is a graph of element distribution test results of a solid electrolyte according to an embodiment of the present application;

4 is an optical microscope diagram of the surface roughness test of a solid electrolyte sheet according to an embodiment of the present application;

Fig. 5 is a schematic diagram of a device according to an embodiment of the present application.

Detailed ways

The sulfide solid electrolyte sheet provided by the embodiment of the present application includes a sulfide electrolyte material and a boron element doped in the sulfide electrolyte material, and the mass concentration of boron element at any position on the surface of the sulfide electrolyte sheet is B ₀ with a surface concentration of sulfide electrolyte plate B ₁₀₀ relative deviation from the mass of boron element 100μm at the location _{_{(B 0 -B 100) / B}} 0 not exceed 20%.

According to some embodiments of the present application, the relative deviation (B ₀ -B ₁₀₀ )/B ₀ does not exceed 10%, for example, does not exceed 9%, 8%, 7%, 6%, 5%, and any value in between , Preferably not more than 8%.

In the embodiment of the present application, boron is introduced into the sulfide electrolyte, which can effectively reduce the binding effect of anions on lithium ions and improve the transmission capacity of lithium ions; and, boron is present on the surface of the sulfide solid electrolyte sheet. Uniform distribution not only improves the doping uniformity and conductivity of the solid electrolyte sheet, but also significantly improves the surface roughness of the solid electrolyte sheet, which facilitates the diffusion process of lithium ions between the solid electrolyte sheet and the lithium metal anode interface, thereby reducing Interface impedance and improve battery cycle performance.

According to some embodiments of the application, the surface roughness of the solid electrolyte sheet is 3 μm to 15 μm, for example, 3 μm, 4 μm, 5 μm, 6 μm, 7 μm, 8 μm, 9 μm, 10 μm, 11 μm, 12 μm, 13 μm, 14 μm, and some of them. The arbitrary value between is preferably 3 μm to 10 μm.

According to a preferred embodiment of the present application, the surface roughness of the sulfide solid electrolyte sheet is 3 μm to 6 μm.

In the embodiment of the application, the surface roughness of the electrolyte sheet refers to: placing the electrolyte sheet under a high-precision optical microscope for observation, and obtaining the surface height distribution information of the electrolyte sheet in an area of 200*300μm ² in 3D imaging mode. The surface roughness can be obtained by counting the difference in the maximum surface height of the electrolyte sheet.

The improvement of the surface roughness of the electrolyte sheet facilitates the diffusion process of lithium ions at the interface between the electrolyte sheet and the lithium metal anode, thereby reducing the interface impedance and improving the cycle performance of the battery. When the surface roughness of the electrolyte sheet is too large, its surface morphology is uneven, while the surface of the lithium metal anode is smooth, so the interface contact between the electrolyte and the lithium metal is very insufficient, which makes the interface migration of lithium ions more difficult. Improving the surface roughness of the electrolyte helps increase its contact points with lithium metal, thereby promoting the transport of lithium ions at the interface and reducing the interface polarization. However, under certain process conditions, the composition and morphology of the electrolyte material have a limit to the surface roughness. To further reduce the surface roughness, it is necessary to improve the press process and the mold. Therefore, under the current process conditions, The surface roughness ranges from 3 μm to 15 μm, preferably 3 μm to 10 μm.

According to some embodiments of the present application, the electrical conductivity of the solid electrolyte sheet is 1.6 mS/cm to 2.9 mS/cm, for example 1.6 mS/cm, 1.7 mS/cm, 1.9 mS/cm, 2.1 mS/cm, 2.3 mS/cm, 2.4mS/cm, 2.5mS/cm, 2.6mS/cm, 2.7mS/cm, 2.8mS/cm, 2.9mS/cm and any value between them, preferably 2.1mS/cm～2.8mS /cm.

Electrolyte conductivity is affected by the content and uniformity of distribution of doped boron in the electrolyte sheet. When the content is constant, improving the uniformity of boron doping is beneficial to increase the conductivity. If the distribution of boron is uneven, there must be some areas Too low doping amount of boron element and too high doping amount in some areas, on the one hand, can not achieve the ideal structure modification effect, on the other hand, it will also affect the local distribution and migration of lithium ions, and the improvement effect of conductivity is not good. In addition, the influence of doping a small amount of elements and improving the uniformity of element distribution on the electrolyte body structure is limited, and the conductivity improvement effect that can be achieved has a certain range. The conductivity range under the improved condition is 1.7mS/ cm～2.8mS/cm, the preferred range is 2.1mS/cm～2.8mS/cm.

According to some embodiments of the present application, the mass percentage of the boron element in the electrolyte sheet is 0.5%-10%, for example, 1%, 2%, 3%, 4%, 5%, 6%, 7% , 8%, 9%, 10% and any value between them, preferably 3% to 7%.

When the content of boron in the electrolyte sheet is too low, the doping of boron has little effect on the electrolyte structure. Although it can also improve the conductivity to a certain extent, the effect of this improvement is not significant, and the boron is too low The content will cause the concentration test error to increase, so the measured concentration deviation will be larger. When the content of boron in the electrolyte sheet is too high, the problem of local element enrichment is likely to occur, which is not conducive to achieving uniform modification results, and too high doping of boron element will reduce the relative content of lithium ions in the electrolyte sheet. The content is not conducive to improving the conductivity of the electrolyte sheet and battery performance.

According to some embodiments of the present application, the sulfide electrolyte material includes Li ₂ S·P ₂ S ₅ , Li ₂ S·GeS ₂ , Li ₂ S·SiS ₂ , Li ₆ PS ₅ X, and Li ₇ P ₃ S ₁₁ One or more of them, wherein X is selected from at least one of Cl, Br, and I, preferably Cl.

The use of different sulfide electrolyte materials can achieve the effect of improving the conductivity and surface uniformity of the doped solid electrolyte through the doping of boron and the improvement of the uniformity of the distribution of boron on the surface of the electrolyte sheet. Therefore, this application is implemented In the sulfide solid electrolyte sheet of the method, the type of sulfide electrolyte material contained is not limited.

In the second aspect of the present application, the embodiments of the present application also provide a method for preparing the above-mentioned sulfide solid electrolyte sheet, including:

Obtain an initial reaction mixture containing sulfide sulfide electrolyte raw material and organic solvent;

Obtain a modified solution containing borate and organic solvent;

In the preparation method provided by the embodiment of the present application, borate is used as the doping material to obtain a solid electrolyte co-doped with boron and oxygen, wherein the doping of boron element can reduce the binding effect of anions on lithium ions, and improve lithium ions. Partial doping of oxygen element to replace sulfur element can not only produce mixed anion effect to improve lithium ion conductivity, but also inhibit the formation of space charge layer at the interface between oxide cathode and sulfide electrolyte, and reduce interface impedance; and the doping process As a Lewis acid, the borate ester introduced in the sulfide has a 2P empty orbital, which can form a complex with the sulfide solid electrolyte electron donor to promote the full reaction of the sulfide solid electrolyte with the doping material, thereby improving the doping uniformity of the reaction product And conductivity.

The above method utilizes the property that the borate can form a uniformly dispersed solution in a suitable solvent. During the doping modification process of the solid electrolyte, the electrolyte raw material and the borate to be doped are fully mixed. In addition, the DSC-TG test showed that the borate has an endothermic decomposition peak and a weight loss curve in the range below the sulfide phase formation temperature, that is to say, the borate can be completely decomposed at the phase formation temperature of the sulfide electrolyte, thereby reducing The introduction of impurities or residual reactants makes the final sulfide electrolyte ionic conductivity significantly improved.

In addition, the above method also solves the problem that the electrolyte sheet structure is damaged due to the volatilization of the solvent and the decomposition of the organic borate during the heat treatment, and the poor contact between the particles and the particles, thereby affecting the diffusion process of the doping elements in the solid electrolyte. Through multiple grinding, cold pressing and sintering, the boron element is uniformly distributed in the electrolyte, so that the doping uniformity and conductivity of the solid electrolyte are improved, and the surface roughness of the solid electrolyte sheet is significantly improved. The solid electrolyte sheet with uniform surface morphology promotes the diffusion process of lithium ions at the interface between the solid electrolyte sheet and the lithium metal anode, reduces the interface impedance and improves the cycle performance of the battery.

According to a preferred embodiment of the present application, the sulfide electrolyte raw material is dispersed in an organic solvent to form an initial reaction mixture.

According to a preferred embodiment of the present application, the borate is dispersed in an organic solvent to form a modified solution.

According to some embodiments of the present application, the borate has a structure represented by formula (I):

Wherein, R is selected from C1-C4 alkyl.

It is worth noting that if the number of substituted alkyl carbon atoms in the borate structure increases, it will only slightly affect the solubility of the borate in organic solvents, but compared to the solid-solid contact preparation method, the obtained The conductivity performance of the solid electrolyte still maintains a greater advantage.

According to some preferred modes of this application, the borate is selected from one or more of the structures (I-1) to (I-4):

According to some embodiments of the present application, the initial reaction mixture is mixed with the modified solution and then fully dispersed, and the time for the fully dispersed is 5-20 hours.

According to some embodiments of the present application, the organic solvent used to disperse the sulfide electrolyte material and the organic solvent used to disperse the borate may be independently selected from tetrahydrofuran, acetonitrile, pyridine, methanol, ethanol, propanol, isopropanol, butane One or more of alcohol, propyl propionate, butyl propionate, and butyl butyrate.

According to some embodiments of the present application, when the sulfide electrolyte raw material is dispersed in an organic solvent and the borate is dispersed in an organic solvent, the volume ratio of the sulfide electrolyte raw material and the organic solvent can be 1:1 to 1: 10. The volume ratio of borate and organic solvent blending can be 1:1 to 1:10.

According to some embodiments of the present application, when mixing the initial reaction mixture with the modifying solution, the blending method used may be a ball milling method.

According to some embodiments of the present application, the drying process needs to be performed in a vacuum environment with a vacuum degree of less than -90 kPa, and the drying temperature is 100°C to 120°C.

According to a preferred embodiment of the present application, the number of post-treatments is 2 to 3 times.

With the increase of the number of post-treatments, the doped electrolyte material undergoes multiple grinding, tableting and sintering, the distribution of various elements in the bulk material tends to be uniform, and the surface roughness and interface impedance are reduced. However, too many high-temperature sintering may also cause structural phase changes in the electrolyte, which affects the increase in conductivity.

According to some embodiments of the present application, the sintering temperature is 200°C to 700°C, such as 200°C, 300°C, 400°C, 500°C, 550°C, 600°C and any value in between, preferably 200°C. ℃～600℃.

According to a preferred embodiment of the present application, the sintering temperature is 200°C to 400°C.

The sintering temperature can affect the performance of the prepared solid electrolyte and battery. Specifically, the sintering temperature should match the phase formation temperature of the sulfide and the decomposition temperature of the borate. If the heat treatment temperature is too low, the specific electrolyte crystal structure cannot be obtained and the borate is not completely decomposed, although the electrolyte conductivity However, the effective amount of B doping is extremely low, resulting in a small increase in conductivity; if the sintering temperature is too high, the electrolyte itself is prone to phase change and impurity generation, and the increase in conductivity and capacity will also decrease. small.

According to a preferred embodiment of the present application, the sintering temperature in each post-treatment increases as the number of post-treatments increases.

The following takes three post-treatments as an example to illustrate the technical effect of the sintering temperature gradient increase.

In the sintering step of the first post-treatment, the sintering temperature should not be too high. If the first sintering temperature is too high, the volatilization of the solvent, the decomposition of the borate and the phase formation of the sulfide electrolyte are concentrated in this sintering step, and the two processes of volatilization of the solvent and the decomposition of the borate The constant volume change in the electrolyte causes the compacted electrolyte block to become a porous and loose structure, and the particle-to-particle contact is not good, which is not conducive to the diffusion process of the boron element in the electrolyte phase, which makes the difference and uniformity of the electrolyte surface composition increase. In addition, long-term high-temperature sintering will also lead to the formation of electrolyte impurities and the decrease of conductivity, which will further affect the interface impedance and cycle performance of the battery.

According to a preferred embodiment of the present application, the sintering temperature of the first post-treatment is 200°C to 700°C, for example, 200°C, 300°C, 400°C, 500°C, 550°C, 600°C and any value in between, Preferably it is 200 to 400 degreeC.

In the sintering step of the second post-treatment, a moderate sintering temperature needs to be selected, preferably higher than the first sintering temperature. If the second sintering temperature is too low, the borate cannot be decomposed, the phase formation process of the electrolyte and the boron element modification process are not complete, or they can only be assembled in the third post-treatment process. As a result, the electrolyte sheet still cannot maintain good interface contact, which is not conducive to the uniform distribution of boron and the improvement of surface properties. If the second sintering temperature is too high, the phase formation process of the electrolyte and the boron element modification process will be concentrated in the second post-treatment, which is not conducive to the uniform modification effect, and the too high heat treatment temperature has an effect on the conductivity of the electrolyte. There are also adverse effects.

According to a preferred embodiment of the present application, the sintering temperature of the first post-treatment is 200°C to 700°C, for example, 200°C, 300°C, 400°C, 500°C, 550°C, 600°C and any value in between, Preferably it is 300 to 500 degreeC.

According to a preferred embodiment of the present application, the sintering temperature of the second post-treatment is higher than the sintering temperature of the first post-treatment by 0-400°C, preferably 100-200°C.

To sum up, in the three post-treatment processes, the sintering temperature of three temperature zones, low, medium and high temperature is adopted in sequence, which is beneficial to distinguish the different reactions in the electrolyte modification process, so as to prepare an electrolyte sheet with uniform boron element distribution. , Due to the high uniformity of the surface composition and morphology of the electrolyte sheet, its surface roughness and ionic conductivity are significantly improved, thereby improving the interface performance and cycle performance of the solid-state battery.

According to some embodiments of the present application, the cold pressing refers to cold pressing under a cold pressure of 50 MPa to 200 MPa.

According to some embodiments of the present application, the time for each sintering is 0.5-5 hours.

According to some embodiments of the present application, the heat treatment atmosphere may be an inert atmosphere such as argon and nitrogen.

In the third aspect of the present application, the embodiments of the present application also provide an all-solid-state lithium-ion battery prepared by the solid-state electrolyte sheet of the embodiments of the present application. The all-solid-state lithium-ion battery can be all-solid-state in various forms. Lithium Ion Battery.

In the fourth aspect of the present application, the embodiments of the present application also provide a laminated all-solid-state lithium-ion battery, including a positive pole piece, a solid electrolyte sheet, and a negative pole piece; wherein, the solid electrolyte sheet is an application implementation Way of solid electrolyte sheet.

According to some embodiments of the present application, the positive pole piece is prepared from raw materials comprising a solid electrolyte sheet, a positive electrode active material, and a conductive agent; wherein, the solid electrolyte sheet is the solid electrolyte sheet according to the application embodiment.

According to some embodiments of the present application, the preparation method of the laminated all-solid-state lithium ion battery includes the following steps:

S1. Preparation of positive pole pieces;

S2. Prepare a sulfide solid electrolyte sheet according to the preparation method described in the second aspect of this application;

S3. Preparation of negative pole piece;

S4. Laminating the positive pole piece, the solid electrolyte sheet and the negative pole piece in sequence, and pressing to obtain the all-solid lithium ion battery.

According to a preferred embodiment of the present application, the step S1 includes:

Preparing a sulfide solid electrolyte sheet according to the preparation method described in the second aspect of the present application;

Mixing and grinding the sulfide solid electrolyte sheet with a positive electrode active material and a conductive agent to obtain a positive electrode powder;

The positive electrode powder is dispersed on the surface of the positive electrode current collector aluminum foil and cold pressed to obtain the positive electrode pole piece.

The positive pole piece, solid electrolyte sheet, and negative pole piece are respectively sliced according to the required size, and the sliced positive pole piece, solid electrolyte sheet, and negative pole piece are aligned in the center and sequentially stacked into a sandwich layer unit, and the sandwich layer unit Press and compound together at a certain temperature to obtain the battery cell of the all-solid-state lithium-ion battery; cold-press the battery cell and place it in an outer package to form an all-solid-state lithium-ion battery, which includes a positive pole piece and a negative pole Sheet and solid electrolyte sheet spaced between the positive pole piece and the negative pole piece.

In the fifth aspect of the present application, the embodiments of the present application also provide a device, including the all-solid-state lithium ion battery described in the third aspect of the present application or the laminated type described in the fourth aspect of the present application. All solid-state lithium-ion battery.

According to a preferred embodiment of the present application, the all-solid-state lithium-ion battery or laminated all-solid-state lithium-ion battery can be used as the power source of the device, and can also be used as the energy storage unit of the device. The device of the present application adopts the all-solid-state lithium-ion battery or laminated all-solid-state lithium-ion battery provided in this application, and therefore has at least the same advantages as the all-solid-state lithium-ion battery or the laminated all-solid-state lithium-ion battery.

The device can be, but is not limited to, mobile devices (such as mobile phones, laptop computers, etc.), electric vehicles (such as pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf Vehicles, electric trucks, etc.), electric trains, ships and satellites, energy storage systems, etc.

Figure 5 is a device as an example. The device is a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle. In order to meet the requirements of the device for high power and high energy density of the battery, a battery pack or battery module can be used.

According to specific embodiments of the present application, the device may also be a mobile phone, a tablet computer, a notebook computer, etc. The device is generally required to be light and thin, and the battery of the embodiment of the present application can be used as a power source.

The application will be further explained below in conjunction with specific embodiments. It should be understood that these embodiments are only used to illustrate the application and not to limit the scope of the application.

Preparation of solid electrolyte sheet

Disperse the sulfide electrolyte raw materials in pyridine to form an initial reaction mixture; disperse the boric acid ester represented by formula (I-1) in pyridine to form a modified solution; after mixing the initial reaction mixture and the modified solution, pass Disperse sufficiently to form a uniform mixture; heat and dry the uniform mixture to remove the solvent. The drying process must be maintained in a vacuum environment with a vacuum degree of less than -90kPa, and the drying temperature should be maintained at 100°C to obtain the initial product; Several post-treatments, each post-treatment includes: grinding, cold pressing and sintering steps, among which, cold pressing forms a compact disc sample; sintering is to sinter the disc sample in an argon atmosphere; multiple post-treatments Then a doped modified solid electrolyte sheet is obtained. The specific preparation parameters of the solid electrolyte sheets in Examples 1-14 and Comparative Examples 1-4 are shown in Table 1.

Preparation of all solid-state lithium ion batteries

(1) Preparation of positive pole piece

The solid electrolyte sheet was prepared according to the method of Example 1-14 or Comparative Example 1-4, ground into a powder, and combined with the positive electrode active material LiNi _1/3 Co _1/3 Mn _1/3 O ₂ and the conductive agent Super-P The mass ratio of 70:27:3 is mixed and ground to obtain a uniformly dispersed positive electrode powder; the positive electrode powder is uniformly dispersed on the surface of the positive electrode current collector aluminum foil, and then the positive pole piece is obtained by cold pressing of 50MPa.

(2) Preparation of solid electrolyte sheet

The solid electrolyte sheet was prepared according to the method of Examples 1-14 or Comparative Examples 1-4.

(3) Preparation of lithium metal negative pole piece

The lithium foil is attached to the surface of the negative electrode current collector copper foil by rolling, and then the negative electrode piece is obtained by slitting.

(4) Preparation of all solid-state lithium-ion batteries

The above-mentioned positive pole piece, solid electrolyte sheet, and lithium metal negative electrode are sequentially stacked, and pressurized at 300 MPa to prepare an all-solid lithium ion battery.

Perform the following performance tests on the solid electrolyte sheet and all-solid-state lithium ion battery prepared above:

(1) Conductivity test: Use Chenhua electrochemical workstation to measure the ohmic impedance of the electrolyte sheet. The test temperature is 25℃, the frequency range is 1Hz-1MHz, and the perturbation signal is 5mV. It can be calculated based on the impedance, thickness and area of the electrolyte layer Ionic conductivity.

(2) Surface roughness test: Place the electrolyte sheet under a high-precision optical microscope for observation. In 3D imaging mode, the surface height distribution information of the electrolyte sheet within 200*300μm ² can be obtained, and the maximum surface height difference of the electrolyte sheet can be counted Value to get the surface roughness.

(3) Surface element concentration distribution test: place the electrolyte sheet under a scanning electron microscope for observation, and collect the element content information on the surface of the electrolyte sheet through EDS (energy spectrum analysis) test. The sampling area is a square area of 1μm*1μm, and the adjustment is different. The sampling area is 100μm apart, and the content distribution results of boron in different areas on the surface of the electrolyte sheet can be obtained.

(4) Element content test: The electrolyte sheet is dissolved in methanol solvent to form a uniform solution, and then the concentration of each element in the solution is quantitatively characterized by ICP (Inductively Coupled Plasma Emission Spectroscopy) test to obtain the boron element in the electrolyte sheet. content.

(5) Interface impedance test: Use Chenhua electrochemical workstation to conduct electrochemical impedance test on all solid-state lithium-ion batteries, the frequency range is 0.01Hz-1MHz, and the perturbation signal is 5mV.

(6) Cycle performance test: At 25℃, charge the all-solid-state lithium-ion battery at a constant current of 0.1C to a voltage of 4.2V, then discharge at a constant current of 0.1C until the final voltage is 2.8V, and record the discharge of the first cycle capacity. Then carry out charging and discharging cycles according to the above operation. When the cycle reaches 100 cycles, stop charging and discharging. The ratio of the discharge capacity at this time to the first cycle discharge capacity is the cycle capacity retention rate of the battery.

Figures 1 to 4 and Table 1 specifically show the results of the above test:

Figure 1 is an XRD test spectrum of a solid electrolyte according to an embodiment of the present application. It can be seen from the figure that the main lattice diffraction peaks of the solid electrolyte doped with borate are the same as the control sample, which proves that a small amount of borate The introduction will not affect the structure of the sulfide electrolyte; and the diffraction peak of borate itself does not appear in the doped sample, indicating that the borate has been completely decomposed.

Figure 2 is a graph of the Raman test results of the solid electrolyte according to the embodiment of the present application. It can be seen from the figure that the solid electrolyte doped with borate only has the same peak position as the control sample, which represents the solid state of sulfide. The PS ⁴ -group in the electrolyte also shows that the main structure of the solid electrolyte has not changed before and after doping.

Figure 3 is a graph of the element distribution test results of the solid electrolyte according to the embodiment of the present application. It can be clearly seen from the figure that the distribution area of the B and O elements and the distribution area of the S element basically overlap, which proves that the B and O elements are evenly doped The impurities enter the sulfide electrolyte.

Fig. 4 is an optical microscope diagram of a surface roughness test of a solid electrolyte sheet according to an embodiment of the present application. The electrolyte sheets of Comparative Example 1, Comparative Example 2 and Example 12 were placed under a high-precision optical microscope for observation. Among them, 4-A is an optical microscope image of the solid electrolyte sheet of Comparative Example 1, which did not incorporate boric acid. The surface morphology of the electrolyte sheet is very uneven. The figure shows that the maximum surface height difference is 24.36μm; 4-B is the optical microscope image of the solid electrolyte sheet of Comparative Example 2, which is doped with borate, but only through After one post-treatment, the surface roughness of the electrolyte sheet has been reduced. The figure shows that the maximum surface height difference is 18.11μm, but the morphology difference is still obvious; 4-C is an optical microscope image of the solid electrolyte sheet of Example 12, and its Incorporating boric acid ester and after many post-treatments, the surface of the electrolyte sheet is uniform and the roughness is significantly reduced. The figure shows that the maximum surface height difference is only 3.23 μm.

Table 1 below shows the specific parameters and test results of Examples 1-14 and Comparative Examples 1-4:

Table 1 Specific parameters and test results of Examples and Comparative Examples

The data shown in Table 1 shows the influence of various parameters in the embodiments of the present application on the performance of the solid electrolyte and lithium ion battery prepared.

The data of Examples 1 to 5 show the influence of the content change of the boron element in the electrolyte sheet on the performance of the electrolyte sheet. When the content of boron in the electrolyte sheet is too low (as in Example 1), the introduction of boron has little effect on the electrolyte structure. Although it can also improve the conductivity of the electrolyte sheet to a certain extent, the improvement effect is not significant , And too low boron content will increase the concentration test error, so the measured concentration deviation is also larger. When the content of boron in the electrolyte sheet is too high, the problem of local element enrichment is likely to occur, which is not conducive to achieving uniform modification results, and too high doping of boron element will reduce the relative content of lithium ions in the electrolyte sheet. The content is therefore not conducive to improving the conductivity of the electrolyte sheet and battery performance. Therefore, in the embodiment of the present application, the mass concentration of the boron element in the electrolyte sheet is 0.5% to 10%, preferably 3% to 7%.

The data of Examples 3 and 6 show the effect of changes in the number of post-treatments on the performance of the electrolyte sheet. It can be seen from Table 1 that Example 6 achieves better performance than Example 3. This is because as the number of post-treatments increases, the doped electrolyte material undergoes multiple grinding, briquetting and sintering. The distribution of multiple elements in the bulk material tends to be uniform, and the surface roughness and interface impedance are reduced. However, too many high-temperature sintering may also cause structural phase changes in the electrolyte, which affects the increase in conductivity. Therefore, in the embodiment of the present application, the number of post-processing should be more than once, preferably 2 to 3 times.

Examples 6-12 take three post-treatments as an example to illustrate the technical effect of the gradual increase in the sintering temperature as the number of post-treatments increases.

First of all, for the sintering step in the first post-treatment, the sintering temperature should not be too high. It can be seen from Table 1 that among Examples 6-9, Example 7 achieved the best performance improvement, followed by Examples 8, 9, and 6. This is because the first sintering temperature of Example 6 is too high. The volatilization of the solvent, the decomposition of boric acid ester and the phase formation of the sulfide electrolyte are concentrated in the first sintering step, and the volume is continuously generated during the first two processes. The change causes the compacted electrolyte block to become a porous and loose structure, and the poor contact between particles will affect the diffusion process of boron in the electrolyte bulk, resulting in increased differences in electrolyte surface composition and reduced uniformity; and High temperature sintering over time will also lead to the formation of electrolyte miscellaneous phases and the decrease of conductivity, which will further affect the interface impedance and cycle performance of the battery. Therefore, in the embodiment of the present application, the performance is best when the sintering temperature in the first post-treatment is 200°C.

Secondly, for the sintering step in the second post-treatment, a moderate sintering temperature needs to be selected, preferably higher than the first sintering temperature. The data of Examples 7 and 10 to 12 illustrate the effect of changing the second sintering temperature on the electrolyte sheet and battery performance. Example 12 has the best performance, followed by Examples 11 and 7, and Example 10 has improved performance Slightly smaller. This is because, if the second sintering temperature is too low (as in Example 10), the borate cannot be decomposed, the electrolyte phase formation process and the boron element modification process are not complete, or they can only be aggregated to the third post-treatment During the completion of the process, due to the influence of the decomposition of borate, the electrolyte sheet still cannot maintain good interface contact, which is not conducive to the uniform distribution of boron element and the improvement of surface properties. If the second sintering temperature is too high (Example 7), the electrolyte phase formation process and the boron element modification process are concentrated in the second post-treatment, which is not conducive to the uniform modification effect, and the heat treatment temperature is too high It also has an adverse effect on the conductivity of the electrolyte.

To sum up, taking the three post-treatments as an example, the sintering temperature in three temperature zones of low, medium and high temperature is adopted in sequence, which is beneficial to distinguish the different reactions in the electrolyte modification process, so as to prepare an electrolyte sheet with uniform boron element distribution. , The surface composition and morphology of the electrolyte sheet are highly uniform, and its surface roughness and ionic conductivity are significantly improved, thereby improving the interface performance and cycle performance of the solid-state battery.

Examples 13 and 14 show the effect of changing the electrolyte type on the electrolyte sheet and battery performance. Using sulfide electrolyte materials of different compositions, electrolyte sheets with uniformly modified boron elements can be obtained. Compared with the comparative example, the surface element distribution, surface morphology and ion conductivity are significantly improved. Therefore, In the sulfide solid electrolyte sheet of the embodiment of the present application, the type of the sulfide electrolyte material contained is not limited.

Based on the disclosure and teaching of the foregoing specification, those skilled in the art can also make changes and modifications to the foregoing embodiments. Therefore, this application is not limited to the specific implementations disclosed and described above, and some modifications and changes to this application should also fall within the protection scope of the claims of this application. In addition, although some specific terms are used in this specification, these terms are only for convenience of description and do not constitute any limitation to the application.

Claims

A sulfide solid electrolyte sheet, the electrolyte material comprising a sulfide and boron is doped in the sulfide electrolyte material, and the boron concentration of the electrolyte sheet B 0 from the surface of the electrolyte sheet surface position of an arbitrary position The relative deviation (B 0 -B 100 )/B 0 of the boron element mass concentration B 100 at 100 μm does not exceed 20%.
The sulfide solid electrolyte sheet according to claim 1, wherein the relative deviation (B 0 -B 100 )/B 0 does not exceed 10%.
The sulfide solid electrolyte sheet according to claim 1 or 2, wherein the relative deviation (B 0 -B 100 )/B 0 does not exceed 8%.
The sulfide solid electrolyte sheet according to any one of claims 1 to 3, wherein the surface roughness of the sulfide solid electrolyte sheet is 3 μm to 15 μm.
The sulfide solid electrolyte sheet according to any one of claims 1 to 4, wherein the surface roughness of the sulfide solid electrolyte sheet is 3 μm to 10 μm.
The sulfide solid electrolyte sheet according to any one of claims 1 to 5, wherein the surface roughness of the sulfide solid electrolyte sheet is 3 μm to 6 μm.
The sulfide solid electrolyte sheet according to any one of claims 1 to 6, wherein the electrical conductivity of the sulfide solid electrolyte sheet is 1.6 mS/cm to 2.9 mS/cm.
The sulfide solid electrolyte sheet according to any one of claims 1-7, wherein the conductivity of the sulfide solid electrolyte sheet is 2.1 mS/cm to 2.8 mS/cm.
The sulfide solid electrolyte sheet according to any one of claims 1-8, wherein the mass concentration of boron element in the sulfide solid electrolyte sheet is 0.5%-10%.
The sulfide solid electrolyte sheet according to any one of claims 1-9, wherein the mass concentration of boron element in the sulfide solid electrolyte sheet is 3% to 7%.
The sulfide solid electrolyte sheet according to any one of claims 1-10, wherein the sulfide electrolyte material comprises Li 2 S·P 2 S 5 , Li 2 S·GeS 2 , Li 2 S·SiS 2 One or more of Li 6 PS 5 X and Li 7 P 3 S 11 , wherein X is selected from at least one of Cl, Br, and I.
A method for preparing the sulfide solid electrolyte sheet according to any one of claims 1-11, comprising:

Obtain an initial reaction mixture containing sulfide electrolyte raw materials and organic solvents;

Obtain a modified solution containing borate and organic solvent;

Mixing the initial reaction mixture with the modification solution and drying to obtain an initial product;

The initial product is subjected to more than one post-treatment, and each post-treatment sequentially includes the steps of grinding, cold pressing and sintering.
The method for preparing a sulfide solid electrolyte sheet according to claim 12, wherein the number of post-treatments is 2 to 3 times.
The method for preparing a sulfide solid electrolyte sheet according to claim 12 or 13, wherein the sintering temperature is 200°C to 700°C.
The method for preparing a sulfide solid electrolyte sheet according to any one of claims 12-14, wherein the sintering temperature is 200°C to 600°C.
The method for preparing a sulfide solid electrolyte sheet according to any one of claims 12-15, wherein the sintering temperature in each post-treatment increases as the number of post-treatments increases.
The method for preparing a sulfide solid electrolyte sheet according to any one of claims 12-16, wherein the borate has a structure represented by formula (I):

Wherein, R is selected from C1-C4 alkyl.
An all-solid-state lithium ion battery, which is prepared by the sulfide solid electrolyte sheet according to any one of claims 1-11 or the preparation method according to any one of claims 12-17 Prepared.
A laminated all-solid-state lithium ion battery, comprising a positive pole piece, a solid electrolyte sheet and a negative pole piece; wherein the solid electrolyte sheet is the sulfide solid electrolyte sheet according to any one of claims 1-11 or A sulfide solid electrolyte sheet prepared according to the preparation method of any one of claims 12-17.
The laminated all-solid-state lithium-ion battery according to claim 19, wherein the positive pole piece is prepared from a raw material comprising a solid electrolyte sheet, a positive electrode active material and a conductive agent; wherein, the solid electrolyte sheet is according to claim 1- The sulfide solid electrolyte sheet according to any one of 11 or the sulfide solid electrolyte sheet prepared according to the preparation method according to any one of claims 12-17.
A device comprising the all solid state lithium ion battery according to claim 18 or the laminated all solid state lithium ion battery according to claim 19 or 20.