WO2020220945A1 - Positive plate of sulfide solid-state battery, sulfide solid-state battery and device - Google Patents

Abstract

Provided by the present invention are a positive plate of a sulfide solid-state battery, a sulfide solid-state battery and a device. The positive plate of the sulfide solid-state battery comprises a positive current collector and a positive active material layer disposed on at least one surface of the positive current collector. The positive active material layer comprises a positive active material, a solid electrolyte and added salt, the added salt experiencing endothermic phase change at 40-150°C. Also provided by the present invention is a sulfide solid-state battery comprising the described positive plate. The added salt that undergoes endothermic phase change at 40-150°C is added to the positive plate of the sulfide solid-battery according to the present invention, and during the charging and discharging of the battery, the phase change endothermic effect of the added salt may be used to absorb heat generated by exothermic processes, such as self-decomposition and side reactions of a sulfide solid-state electrolyte in the positive plate, thereby reducing the risk of thermal runaway caused by a sharp rise in battery temperature and improving the thermal safety and cycle stability of a sulfide solid-state battery system.

Description

Positive pole piece of sulfide solid state battery, sulfide solid state battery and device

This application claims the priority of a Chinese patent application filed with the Chinese Patent Office on April 29, 2019, the application number is 201910353583.9, and the application name is "sulfide solid-state battery positive pole piece and sulfide solid-state battery", the entire content of which is incorporated by reference Incorporated in this application.

Technical field

This application relates to the field of batteries, in particular to a sulfide solid-state battery positive pole piece, a sulfide solid-state battery and a device.

Background technique

With the continuous improvement of people's energy density requirements, traditional lithium-ion batteries have been difficult to meet the increasing demand for specific energy, and metal lithium electrodes with high specific capacity advantages have become a research hotspot. The specific capacity of metallic lithium is 3860mAh/g, the electrochemical potential is -3.04V (vs standard hydrogen electrode), and the weight energy density of lithium metal batteries such as lithium-sulfur batteries and lithium-air batteries with lithium as the negative electrode can reach 400Wh/ Above kg.

The early development of lithium metal batteries mainly used liquid electrolyte materials, which contained a large amount of organic solvents, resulting in outstanding safety hazards for liquid lithium metal batteries. The use of a solid electrolyte layer instead of a liquid electrolyte is expected to eliminate potential safety hazards during use, and is more in line with the future development needs of electric vehicles and large-scale energy storage. Therefore, all solid-state lithium metal batteries are being vigorously developed in this field. At present, there are many types of solid electrolytes, which can be divided into organic polymers, inorganic oxides, and inorganic sulfides. Among them, the sulfide solid electrolyte material has an ion conductivity of 10 ^-2 S/cm at room temperature and a wide electrochemical window, which has excellent application prospects. However, in actual use, the thermal safety of sulfide solid-state batteries needs to be improved.

Summary of the invention

In view of the problems in the background art, the purpose of this application is to provide a sulfide solid-state battery positive pole piece and a sulfide solid-state battery to improve the thermal safety of the sulfide solid-state battery.

In order to achieve the above object, the first aspect of the present application provides a positive electrode sheet for a sulfide solid state battery, which includes a positive electrode current collector and a positive electrode active material layer disposed on at least one surface of the positive electrode current collector, the positive electrode active material layer It includes a positive electrode active material and a solid electrolyte, and the positive electrode active material layer further includes an added salt, and the added salt undergoes an endothermic phase change at 40-150°C.

The second aspect of the present application provides a sulfide solid state battery, which includes a positive pole piece, a negative pole piece, and a solid electrolyte membrane interposed between the positive pole piece and the negative pole piece. The positive pole piece is the positive pole piece of the sulfide solid state battery provided in the first aspect of the application.

In the third aspect of the present application, a device is provided, and the device includes the sulfide solid-state battery of the second aspect of the present application.

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

The positive pole piece of the sulfide solid-state battery provided in this application contains added salt that undergoes endothermic phase change at 40-150°C. During the charging and discharging process of the battery, the endothermic effect of the added salt during the phase change can be used to absorb The heat generated by the positive pole piece (such as the side reaction between the positive electrode and the sulfide solid electrolyte caused by the positive electrode active material, and the heat generated by the exothermic process such as the self-decomposition of the sulfide solid electrolyte), thereby reducing the sharp rise in battery temperature The risk of thermal runaway caused by the battery will improve the thermal safety of the sulfide solid-state battery.

Description of the drawings

In order to explain the technical solutions of the embodiments of the present application more clearly, the following will briefly introduce the drawings that need to be used in the embodiments of the present application. Obviously, the drawings described below are only some embodiments of the present application. A person of ordinary skill in the art can obtain other drawings based on the drawings without creative work.

FIG. 1 is a schematic diagram of an embodiment of a sulfide solid-state battery;

Fig. 2 is a schematic diagram of an embodiment of a battery module;

3 is a schematic diagram of an embodiment of the battery pack;

Figure 4 is an exploded view of Figure 3;

Figure 5 is a schematic diagram of an embodiment of a device in which a sulfide solid-state battery is used as a power source;

The reference signs are described as follows: 1-battery pack, 2-upper case, 3-lower case, 4-battery module, 5 sulfide solid state battery.

Detailed ways

In order to make the purpose, technical solutions and advantages of the embodiments of the present application clearer, the following will clearly and completely describe the technical solutions in the embodiments of the present application with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments It is a part of the embodiments of this application, not all of the embodiments. Based on the embodiments in this application, all other embodiments obtained by those of ordinary skill in the art without creative work shall fall within the protection scope of this application.

The sulfide solid-state battery positive pole piece and the sulfide solid-state battery according to the present application will be described in detail below.

The positive pole piece of the sulfide solid state battery of the first aspect of the present application includes a positive electrode current collector and a positive electrode active material layer provided on at least one surface of the positive electrode current collector. The positive electrode active material layer includes a positive electrode active material, a solid electrolyte and an added salt, The added salt undergoes an endothermic phase change at 40-150°C.

The "endothermic phase change caused by the addition of salt" in the present application refers to the fact that the addition of salt absorbs heat and causes a solid-liquid phase transition or a solid phase transition (a change in the phase structure inside the solid phase). The temperature range in which the salt undergoes endothermic phase transition can be measured by differential scanning calorimetry (DSC).

The sulfide solid state battery positive pole piece of the present application is added with an added salt that undergoes an endothermic phase change at 40 to 150°C. During the charging and discharging process of the battery, the phase change endothermic effect of the added salt can be used to absorb the heat generated by the positive pole piece. Heat (such as the side reaction between the positive electrode and the sulfide solid electrolyte caused by the positive electrode active material, the self-decomposition of the sulfide solid electrolyte and other reactions), thereby reducing the risk of battery thermal runaway caused by the rapid increase in battery temperature , Improve the thermal safety and cycle stability of the sulfide solid-state battery system.

Preferably, the added salt undergoes an endothermic phase change at 60-110°C.

Preferably, the decomposition temperature of the added salt is higher than 200°C, so as to avoid the decomposition side reaction of the added salt in the low temperature zone and the adverse effect of such side reaction on the performance of the sulfide solid state battery.

Preferably, the added salt is selected from at least one of inorganic salts of alkali metals, organic salts of alkali metals, and organic-inorganic composite salts of alkali metals.

Further preferably, the added salt is selected from M-imide, where M is a cation selected from at least one of Li, Na, K, Rb, and Cs, and imide is a sulfonimide anion represented by formula (I) ,

In formula (I): n is selected from an integer of 0 to 4; X and Y are each independently selected from one of F, Cl, Br, I, and a fluorinated alkyl group having 1 to 4 carbon atoms.

More preferably, the added salt is selected from Li[(FSO ₂ ) ₂ N] (abbreviated LiFSI), Na[(FSO ₂ ) ₂ N] (abbreviated NaFSI), K[(FSO ₂ ) ₂ N] (abbreviated KFSI), Rb[(FSO ₂ ) ₂ N] (abbreviated RbFSI), Cs[(FSO ₂ ) ₂ N] (abbreviated CsFSI), Li[(FSO ₂ )(CF ₃ SO ₂ )N] (abbreviated LiFTFSI), Na[(FSO ₂ )(CF ₃ SO ₂ )N] (abbreviated NaFTFSI), K[(FSO ₂ )(CF ₃ SO ₂ )N] (abbreviated KFTFSI), Rb[(FSO ₂ )(CF ₃ SO ₂ ) N] (abbreviated RbFTFSI), Cs[(FSO ₂ )(CF ₃ SO ₂ )N] (abbreviated CsFTFSI), Li _0.4 K _0.6 [(FSO ₂ ) ₂ N] (abbreviated Li _0.4 K _0.6 FSI), Li _0.4 Cs _0.6 [(FSO ₂ )(CF ₃ SO ₂ )N] (abbreviated Li _0.4 Cs _0.6 FTFSI), Li _0.8 Cs _0.2 [(FSO ₂ )(CF ₃ SO ₂ )N] (abbreviated Li _0.8 Cs _0.2 FTFSI) At least one.

Preferably, the mass percentage content of the added salt in the positive electrode active material layer is 0.1-20%, preferably 1-10%. In the sulfide solid-state battery positive pole piece of this application, controlling the content of added salt is very important for this application. The higher the content of added salt, the better the effect of improving safety performance. However, if the amount of added salt cannot be controlled In a reasonable range, even if the addition of salt can improve the safety performance, it is very likely to cause the performance of other aspects of the battery to decrease. Therefore, for the comprehensive performance of the battery, the content of the added salt is 0.1-20%, preferably 1~ 10%.

In the positive electrode sheet of the sulfide solid-state battery of the present application, the type of the positive electrode current collector is not specifically limited, and can be selected according to actual needs. The positive electrode current collector is usually a structure or part that can collect current, usually a layered body; the positive electrode current collector can be various materials in the field suitable for use as a positive electrode current collector of an electrochemical energy storage device, for example, it can include It is not limited to metal foil, and more specifically can be materials including but not limited to nickel foil, aluminum foil, carbon-coated aluminum foil or stainless steel.

In the positive electrode sheet of the sulfide solid state battery of the present application, the positive electrode active material layer may be provided on one surface of the positive electrode current collector, or may be provided on both surfaces of the positive electrode current collector.

In the positive electrode sheet of the sulfide solid state battery of the present application, the specific type of the positive electrode active material is not particularly limited, as long as it can accept and extract lithium ions. For example, it may be selected from at least one of olivine structure lithium metal oxide, layered structure lithium metal oxide, spinel structure lithium metal oxide, sulfur powder, and materials modified from the above materials.

Specifically, the olivine structured lithium metal oxide can be selected from lithium iron phosphate (LiFePO ₄ ), lithium cobalt phosphate (LiCoPO ₄ ), lithium manganese phosphate (LiMnPO ₄ ), lithium nickel phosphate (LiNiPO ₄ ), iron phosphate ( FePO ₄ ) and other lithium metal oxides. The layered structure lithium metal oxide can be selected from lithium cobalt oxide (LiCoO ₂ ), lithium nickel oxide (LiNiO ₂ ), ternary material LiNi _s B _t C( _1-st )O ₂ (wherein B and C are independent Ground is selected from at least one of Co, Al, and Mn, and B and C are not the same, at least one of lithium metal oxides such as 0<s<1, 0<t<1). The spinel structure lithium metal oxide may be selected from at least one of lithium metal oxides such as lithium manganate (LiMn ₂ O ₄ ) and lithium nickel manganate (LiNi _0.5 Mn _1.5 O ₄ ). The modified material can be selected from at least one of the above-mentioned materials after doping and coating treatment, and the doping and coating element can be selected from metal elements and non-metal elements, such as Li , N, F, Cl, S, B, P, Al, Si, Zr, Ti, Ge, Sn, Mg, Zn, Ce, W, V, etc.

In the positive pole piece of the sulfide solid state battery of the present application, the solid electrolyte may be selected from sulfide solid electrolyte. The sulfide solid electrolyte may include lithium and sulfur, and may further include other elements. For example, it may include but not limited to at least one of P, Si, Ge, Sn, Al and other elements.

Specifically, the general structural formula of the sulfide solid electrolyte can be expressed as yLi ₂ S-(100-y)LS, where 0<y<100, and the LS can be but not limited to P ₂ S ₅ , SiS ₂ , One or more of GeS ₂ , SnS ₂ , Al ₂ S ₃ and other substances, and the solid electrolyte system it constitutes may include but not limited to Li ₂ SP ₂ S ₅ system, Li ₂ S-SiS ₂ system, Li ₂ S-GeS ₂ system, Li ₂ S-SnS ₂ system, Li ₂ S-Al ₂ S ₃ system, one or more. The state of the sulfide solid electrolyte may be a crystalline state, an amorphous state, or a crystalline-amorphous complex state.

Further, the sulfide solid electrolyte may further include a doping material, and the doping material is preferably a lithium-containing compound LiQ. Specifically, the general formula of the doped sulfide electrolyte structure can be expressed as z(Li ₂ S-LS)-(100-z)LiQ, where 90≤z≤100, and the doping material LiQ may include but not It is limited to a combination of one or more of lithium halide, lithium oxide, lithium nitride, lithium oxyacid salt, and the like. Among them, LiQ may include but not limited to LiF, LiCl, LiBr, LiI, Li ₂ O, Li ₃ N, LiAlO ₂ , Li ₃ PO ₄ , Li ₂ SO ₄ , Li ₃ BO ₃ , Li ₄ SiO ₄ , LiN ( SO ₂ F) ₂ , LiN(SO ₂ R _F ) ₂ , LiN(SO ₂ F)(SO ₂ R _F ) (substituent R _F ＝C _n F _2n+1 , is a saturated perfluoroalkyl group, n is 1 ～2) and one or more of them.

In the positive electrode sheet of the sulfide solid-state battery of the present application, the positive active material layer may also include a conductive agent and a binder. The type and content of the conductive agent and the binder are not specifically limited, and can be based on actual needs. Make a selection. Specifically, the binder may be selected from at least one of SBS, SEBS, PVDF, PTFE, PAALi, styrene-butadiene rubber, nitrile rubber, butylene rubber, styrene rubber, and polyurethane; the conductive agent may be selected from conductive carbon At least one of black (super-P), acetylene black, Vapor-grown carbon fiber (VGCF), carbon nanotubes, and graphene.

The second aspect of the application provides a sulfide solid-state battery. The shape of the sulfide solid-state battery is not particularly limited in the application, and it can be cylindrical, square, or any other shape. Fig. 1 shows a sulfide solid-state battery 5 with a square structure as an example.

In some embodiments, the sulfide solid-state battery can be assembled into a battery module, and the number of the sulfide solid-state battery contained in the battery module can be multiple, and the specific number can be adjusted according to the application and capacity of the battery module.

Fig. 2 is a battery module 4 as an example. Referring to FIG. 2, in the battery module 4, a plurality of sulfide solid state batteries 5 may be arranged in sequence along the length direction of the battery module 4. Of course, it can also be arranged in any other manner. Furthermore, the plurality of sulfide solid-state batteries 5 can be fixed by fasteners.

Optionally, the battery module 4 may further include a housing having an accommodation space, and a plurality of sulfide solid-state batteries 5 are accommodated in the accommodation space.

In some embodiments, the above-mentioned battery modules can also be assembled into a battery pack, and the number of battery modules contained in the battery pack can be adjusted according to the application and capacity of the battery pack.

Figures 3 and 4 show the battery pack 1 as an example. 3 and 4, the battery pack 1 may include a battery box and a plurality of battery modules 4 provided in the battery box. The battery box includes an upper box body 2 and a lower box body 3. The upper box body 2 can be covered on the lower box body 3 and forms a closed space for accommodating the battery module 4. Multiple battery modules 4 can be arranged in the battery box in any manner.

In the third aspect of the present application, a device is provided, and the device includes the sulfide solid-state battery of the second aspect of the present application. The sulfide solid-state battery provides power to the device. 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.

The device can select a sulfide solid-state battery (Cell), a battery module (Module) or a battery pack (pack) according to its usage requirements.

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 sulfide solid-state batteries, battery packs or battery modules can be used.

As another example, the device may be a mobile phone, a tablet computer, a notebook computer, etc. The device is usually thin and light, and can use sulfide solid-state batteries as a power source.

Those skilled in the art can choose a suitable method to prepare the positive electrode of the sulfide solid-state battery of the present application, for example, it can be prepared by dry pressing or wet coating. The following is an example of its preparation process.

The positive pole piece of the sulfide solid-state battery of the present invention can be prepared according to the following dry pressing method:

(1) Disperse and mix the positive electrode active material, solid electrolyte, added salt, and conductive agent in proportion to form a solid mixed material. The dispersion process can be manual or mechanical ball milling. Wherein, based on the total mass of the raw materials for forming the positive electrode active material layer, the mass percentages of the positive electrode active material, solid electrolyte, added salt, and conductive agent may be 50-95% (for example, 70-85%), 4.9, respectively. ~49.9% (for example, 10 to 29%), 0.1 to 20% (for example, 1 to 19%), 0 to 5% (for example, 0 to 2%). The content of the positive electrode active material will affect the construction of the electronic and lithium ion conduction network in the positive pole piece: if the mass percentage of the positive electrode active material in the positive electrode active material layer is higher than 95%, it will cause the solid electrolyte and conductive additives If the content is too low, it is not conducive to the transfer of electrons and lithium ions; if the mass percentage of the positive electrode active material in the positive electrode active material layer is less than 50%, the capacity of the battery will be reduced and the energy density of the battery will be affected.

(2) Disperse the above-mentioned solid mixed material on the surface of the positive electrode current collector, place it in a mold for hot pressing, and press to form a film to obtain a sulfide solid-state battery positive pole piece. Among them, the hot pressing method may be one-step pressing or stepwise pressing. The hot pressing pressure may be 0.1-500 MPa, preferably 100-400 MPa; the hot pressing temperature may be 25-160°C, preferably 60-120°C. If the hot pressing pressure is too low and the temperature is too low, the density of the diaphragm will be low. If the hot pressing pressure is too high, the equipment requirements will be high; if the hot pressing temperature is too high, the electrolyte will easily decompose. The thickness of the positive electrode piece obtained by pressing is 10-200 μm. If the positive pole piece is too thin, the energy density of the battery will decrease; if the positive pole piece is too thick, it will increase the lithium ion transmission impedance in the positive pole piece and polarize the battery.

The positive pole piece of the sulfide solid-state battery of the present invention can also be prepared according to the following wet coating method:

(1) The positive electrode active material, solid electrolyte, added salt, conductive agent, and binder are mixed in an organic solvent and dispersed to form a slurry. Wherein, based on the total mass of the raw materials for forming the positive electrode active material layer, the mass percentages of the positive electrode active material, solid electrolyte, added salt, conductive agent, and binder may be 50-95% (e.g. 70-80%), respectively. %), 4.7 to 39.9% (for example, 10 to 27%), 0.1 to 20% (for example, 1 to 10%), 0.1 to 5% (for example, 1 to 2%), 0.1 to 5% (for example, 1 to 2%) . If the content of the binder is too low, the strength and toughness of the electrolyte membrane will be poor; if the content of the binder is too high, it will affect the transfer of lithium ions and cause polarization of the battery.

In addition, the organic solvent used in the wet coating method needs not to react with the solid electrolyte, and can be selected from ether organic solvents, hydrocarbon organic solvents, ester organic solvents, nitrile organic solvents, amide organic solvents, and alcohols. At least one of quasi organic solvents and halogenated organic solvents. Specifically, the ether organic solvent is selected from at least one of diethyl ether, tetrahydrofuran, and ethylene glycol dimethyl ether; the hydrocarbon organic solvent is selected from n-pentane, n-hexane, cyclohexane, toluene, xylene, and trimethylbenzene At least one of; the ester organic solvent is selected from at least one of ethyl acetate, methyl formate and dimethyl phthalate, the nitrile organic solvent is selected from acetonitrile, and the amide organic solvent is selected from N-methyl Pyrrolidone (NMP) and/or N,N-dimethylformamide (DMF), alcoholic organic solvent is selected from ethanol; halogenated organic solvent is selected from dichloromethane and/or 1,2-dichloroethane. The viscosity of the slurry is controlled by an organic solvent, and the viscosity of the slurry is controlled to be 5000 to 200000 mPa·s, preferably 10000 to 50000 mPa·s. If the viscosity of the slurry is too high, it will increase the difficulty of making the electrolyte membrane; while the viscosity of the slurry is too low, it will easily lead to holes in the electrolyte membrane, which will increase the risk of short circuits in the battery to a certain extent.

(2) The dispersed slurry is uniformly coated on the surface of the aluminum foil, dried and then hot-pressed to obtain the positive electrode of the sulfide solid battery. Among them, the hot pressing method may be one-step pressing or stepwise pressing. The hot pressing pressure may be 1 to 500 MPa, preferably 100 to 300 MPa; the hot pressing temperature may be 25 to 160°C, preferably 60 to 120°C. If the pressure is too small and the temperature is too low, the density of the diaphragm will be low. If the pressure is too high, the equipment requirements will be high. If the temperature is too high, the electrolyte and binder will be decomposed.

The sulfide solid state battery of the second aspect of the present invention includes a positive pole piece, a negative pole piece, and a solid electrolyte membrane spaced between the positive pole piece and the negative pole piece, wherein the positive pole piece is The positive pole piece of the sulfide solid state battery of the first aspect of the present invention.

The sulfide solid state battery of the present invention may be a laminated solid state battery.

In the sulfide solid-state battery of the present invention, the negative pole piece may include a negative current collector and a metal lithium or lithium alloy layer provided on the negative current collector. The negative current collector may be selected from copper foil, carbon-coated copper foil and stainless steel foil. At least one of them. Among them, the thickness of the metallic lithium or lithium alloy layer may be 1 to 200 μm, preferably 5 to 100 μm. The preparation method of the negative pole piece may be: attaching metallic lithium or a lithium alloy to the surface of the negative electrode current collector to form a negative pole piece.

In the sulfide solid-state battery of the present invention, the solid electrolyte membrane can be prepared from a solid electrolyte through a dry membrane method or a wet membrane method. The solid electrolyte may also be selected from sulfide solid electrolytes, and the optional range of the sulfide solid electrolytes is the same as the solid electrolyte in the first aspect of the present invention. The following is an example of the preparation process of the solid electrolyte membrane.

The dry film forming method is as follows: the solid electrolyte is placed in a mold and pressed to form a film. Among them, the pressing method can be cold pressing or hot pressing. The suppression method can be one-step suppression or stepwise suppression. The hot pressing pressure is 0.1 to 500 MPa, preferably 100 to 400 MPa; the hot pressing temperature is 25 to 160°C, preferably 60 to 120°C. If the hot pressing pressure is too low and the temperature is too low, the resulting solid electrolyte membrane will have low density; however, if the hot pressing pressure is too high, the equipment requirements are high, and the hot pressing temperature is too high to easily cause the solid electrolyte to decompose.

The wet membrane production method is as follows: solid electrolyte and binder are mixed in an organic solvent and dispersed into a slurry; the slurry is coated on a glass substrate, dried and pressed to obtain a sulfide electrolyte membrane. Among them, the optional range of the binder and the organic solvent may be the same as the binder and the organic solvent used in the preparation of the positive pole piece by the wet coating method in the first aspect of the present invention. In the mixture of solid electrolyte and binder, the mass percentage of solid electrolyte and binder can be 50%～99%, 1%～50%, and preferably 80%～98%, 2%～20% respectively . If the content of the binder is too low, the strength and toughness of the electrolyte membrane will be poor; if the content of the binder is too high, it will affect the transfer of lithium ions and cause polarization of the battery. In addition, the pressing method may be cold pressing or hot pressing; it may be one-step pressing or stepwise pressing. The hot pressing pressure is 1 to 500 MPa, preferably 100 to 300 MPa; the hot pressing temperature is 25 to 160°C, preferably 60 to 120°C. If the pressure is too low and the temperature is too low, the density of the diaphragm will be low; if the pressure is too high, the equipment requirements are high, and the temperature is too high, which will easily cause the solid electrolyte and binder to decompose.

The sulfide solid-state battery of the second aspect of the present invention can be prepared by the following method:

The positive pole piece, solid electrolyte membrane, and negative pole piece are respectively sliced according to the required size, and the sliced positive pole piece, solid electrolyte membrane, and negative pole piece are aligned in the center and sequentially stacked into a sandwich layer unit. The layer units are pressurized and compounded together at a certain temperature to obtain the cell of the sulfide solid-state battery. The cell is cold-pressed and placed in an outer package for encapsulation to form the sulfide solid-state battery. Among them, the pressing pressure can be 1 to 500 MPa, preferably 100 to 300 MPa; the compaction temperature can be 20 to 160°C, preferably 60 to 120°C.

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

Example 1

(1) Dry preparation of positive pole pieces

In the glove box, the positive electrode active material LiNi _0.8 Co _0.1 Mn _0.1 O ₂ , the sulfide solid electrolyte Li ₃ PS ₄ , the added salt Li[(FSO ₂ )(CF ₃ SO ₂ )N], the conductive agent VGCF are 70% by weight. :24:5:1 After fully stirring and mixing uniformly, disperse it on the surface of aluminum foil and press at 100℃ and 250MPa for 2min to obtain a positive pole piece with a thickness of 50μm.

(2) Preparation of solid electrolyte membrane

In the glove box, the sulfide solid electrolyte Li ₃ PS ₄ was pressed at 100° C. and 250 MPa for 2 min to obtain a solid electrolyte membrane with a thickness of 50 μm.

(3) Preparation of negative pole piece

Put 25μm lithium metal on the surface of copper foil and slice it.

(4) Preparation of sulfide solid-state batteries

Align the centers of the above positive electrode sheet, solid electrolyte membrane sheet, and negative electrode sheet and stack them in sequence. Cold press at room temperature and 250 MPa for 2 minutes to obtain a battery cell unit. After cold pressing, the 10-layer battery cell unit is placed in an outer package for encapsulation. , That is, a solid lithium metal battery.

Example 2

It is basically the same as Example 1, except that the weight ratio of LiNi _0.8 Co _0.1 Mn _0.1 O ₂ , Li ₃ PS ₄ , Li[(FSO ₂ )(CF ₃ SO ₂ )N] and VGCF is changed from 70:24: 5:1 is adjusted to 70:29:0.1:0.9.

Example 3

It is basically the same as Example 1, except that the weight ratio of LiNi _0.8 Co _0.1 Mn _0.1 O ₂ , Li ₃ PS ₄ , Li[(FSO ₂ )(CF ₃ SO ₂ )N] and VGCF is changed from 70:24: 5:1 is adjusted to 70:28:1:1.

Example 4

It is basically the same as Example 1, except that the weight ratio of LiNi _0.8 Co _0.1 Mn _0.1 O ₂ , Li ₃ PS ₄ , Li[(FSO ₂ )(CF ₃ SO ₂ )N] and VGCF is changed from 70:24: 5:1 is adjusted to 70:19:10:1.

Example 5

It is basically the same as Example 1, except that the weight ratio of LiNi _0.8 Co _0.1 Mn _0.1 O ₂ , Li ₃ PS ₄ , Li[(FSO ₂ )(CF ₃ SO ₂ )N] and VGCF is changed from 70:24: 5:1 is adjusted to 70:9:20:1.

Example 6

It is basically the same as Example 1, except that the solid electrolyte in the positive pole piece is replaced by Li ₃ PS ₄ with Li ₆ PS ₅ Cl.

Example 7

It is basically the same as Example 1, except that the weight ratio of LiNi _0.8 Co _0.1 Mn _0.1 O ₂ , Li ₃ PS ₄ , Li[(FSO ₂ )(CF ₃ SO ₂ )N] and VGCF is changed from 70:24: 5:1 is adjusted to 70:20:5:5.

Example 8

It is basically the same as Example 1, except that the positive electrode active material is replaced by LiNi _0.8 Co _0.1 Mn _0.1 O ₂ with LiNi _0.6 Co _0.2 Mn _0.2 O ₂ .

Example 9

Basically the same as Example 8, the difference is: the added salt is replaced from Li[(FSO ₂ )(CF ₃ SO ₂ )N] to Rb[(FSO ₂ )(CF ₃ SO ₂ )N], and the hot pressing conditions Replaced from 100°C and 250MPa to 120°C and 250MPa.

Example 10

It is basically the same as Example 8, but the difference is that the added salt is replaced by Li[(FSO ₂ )(CF ₃ SO ₂ )N] with Cs[(CF ₃ SO ₂ )(CF ₃ SO ₂ )N], and hot The pressure conditions were replaced from 100°C and 250MPa to 130°C and 250MPa.

Example 11

(1) Wet preparation of positive pole pieces

In the glove box, the positive electrode active material LiNi _0.8 Co _0.1 Mn _0.1 O ₂ , the sulfide solid electrolyte Li ₃ PS ₄ , the added salt Li[(FSO ₂ )(CF ₃ SO ₂ )N], the conductive agent VGCF, the binder Styrene butadiene rubber (number-average molecular weight is about 500,000) is mixed in THF solvent at a weight ratio of 70:22:5:1:2, fully stirred and mixed evenly, and then coated on the surface of aluminum foil, and dried naturally at 60°C After drying, cold pressing, and slicing, they were pressed at 100°C and 250 MPa for 2 minutes to obtain a positive electrode piece with a thickness of 50 μm.

(2) Preparation of solid electrolyte membrane

The sulfide solid electrolyte Li ₃ PS ₄ and the binder styrene-butadiene rubber are mixed in a THF solvent at a weight ratio of 98:2 to prepare an electrolyte slurry, which is coated on the glass surface and dried at 60°C, at 50°C, 250MPa Press down for 2 min to obtain a solid electrolyte membrane with a thickness of 50 μm.

(3) Preparation of negative pole piece

Put 25μm lithium metal on the surface of copper foil and slice it.

(4) Preparation of sulfide solid-state batteries

Align the centers of the above-mentioned positive electrode sheet, solid electrolyte membrane sheet, and negative electrode sheet, and stack them in sequence, and cold press at room temperature and 250 MPa for 2 minutes to obtain the battery cell unit. After cold pressing, the 10-layer battery cell unit is placed in the outer package for encapsulation. , That is, a sulfide solid-state battery.

Example 12

It is basically the same as Example 11, but the difference is that the positive electrode active material is replaced by LiNi _0.8 Co _0.1 Mn _0.1 O ₂ with LiNi _0.6 Co _0.2 Mn _0.2 O ₂ .

Example 13

Basically the same as Example 11, the difference is that the added salt Li[(FSO ₂ )(CF ₃ SO ₂ )N] in the positive pole piece is replaced with Li _0.8 Cs _0.2 [(FSO ₂ )(CF ₃ SO ₂ ) N], and the hot pressing conditions are adjusted from 100°C and 250MPa to 50°C and 250MPa.

Example 14

It is basically the same as Example 11, but the difference is that the added salt Li[(FSO ₂ )(CF ₃ SO ₂ )N] in the positive pole piece is replaced with Li[(FSO ₂ ) ₂ N] _0.5 [(FSO ₂ ) (CF ₃ SO ₂ )N] _0.5 ; At the same time, the LiNi _0.8 Co _0.1 Mn _0.1 O ₂ , Li ₃ PS ₄ , Li[(FSO ₂ ) ₂ N] _0.5 [(FSO ₂ )(CF The weight ratio of ₃ SO ₂ )N] _0.5 , VGCF and styrene butadiene rubber is 50:39.9:0.1:5:5, and the hot pressing conditions are replaced from 100°C and 250MPa to 50°C and 250MPa.

Example 15

It is basically the same as Example 11, but the difference is that the added salt Li[(FSO ₂ )(CF ₃ SO ₂ )N] in the positive pole piece is replaced with Li[(FSO ₂ ) ₂ N]. At the same time, LiNi _0.8 Co The weight ratio of _0.1 Mn _0.1 O ₂ , Li ₃ PS ₄ , Li[(FSO ₂ ) ₂ N], VGCF, and styrene butadiene rubber is adjusted to 95:4.7:0.1:0.1:0.1, and the hot pressing conditions are adjusted from 100°C, 250MPa Replace with 150℃, 250MPa.

Comparative example 1

It is basically the same as Example 1, but the difference is that the positive pole piece does not contain added salt, and the weight ratio of LiNi _0.8 Co _0.1 Mn _0.1 O ₂ , Li ₃ PS ₄ , and VGCF is 70:29:1.

Comparative example 2

Basically the same as Example 1, the difference is: the positive pole piece does not contain added salt, and the solid electrolyte in the positive pole piece is replaced by Li ₃ PS ₄ with Li ₆ PS ₅ Cl, and LiNi _0.8 Co _0.1 Mn _0.1 O ₂ The weight ratio of Li ₆ PS ₅ Cl and VGCF is 70:29:1.

Comparative example 3

Basically the same as Example 11, the difference is: the positive pole piece does not contain added salt, and the weight ratio of LiNi _0.8 Co _0.1 Mn _0.1 O ₂ , Li ₃ PS ₄ , VGCF and styrene butadiene rubber is 70:27:1: 2.

Table 1 below shows the specific parameters of Examples 1 to 15 and Comparative Examples 1 to 3:

(Note: The phase transition temperature of the added salt in Table 1 refers to the starting temperature of the phase change of the added salt.)

The performance test of the positive pole piece of the sulfide solid-state battery and the sulfide solid-state battery of the present invention is as follows:

1. Detection of the cumulative thermal effect of the positive pole piece

The sulfide solid-state battery is charged for the first time and charged to 4.2V. After disassembling the test battery, a fully charged positive pole piece is obtained. A differential scanning calorimetry (DSC) test was performed on the positive pole piece in the fully charged state to detect the cumulative heating effect of the positive pole piece during the 25-300 ℃ process.

2. Performance test of sulfide solid-state battery

Set the charging and discharging working voltage range of the sulfide solid-state battery to 2.8V～4.2V, and use the constant current charging and discharging method to carry out the cycle test. The test current is 0.1C (the current density is about 0.13mA/cm ² ). The temperature is 25°C.

(1) First week specific capacity: Test the first week specific discharge capacity of the battery under 0.1C charge and discharge current.

(2) First week Coulomb efficiency; Test the first week Coulomb efficiency of the battery at 0.1C charge and discharge current; First week Coulomb efficiency of the battery = First week specific discharge capacity/First week specific charge capacity×100%.

(3) Cycle test: After the battery is cycled for 50 and 200 weeks, respectively, the capacity retention rate of the battery is tested. Capacity retention rate=50 weeks or 200 weeks discharge specific capacity/first week discharge specific capacity×100%.

Table 2 below shows the performance test results of Examples 1 to 15 and Comparative Examples 1 to 3:

According to Table 1 and Table 2, Examples 1, 6, and 11 are compared with Comparative Examples 1, 2, and 3 respectively. The difference is that the positive pole pieces of Examples 1, 6, and 11 are mixed with added salt, and The positive pole pieces of Comparative Examples 1, 2, and 3 do not contain added salt. It can be seen from Table 2 that, compared with Comparative Examples 1, 2, and 3, the positive pole pieces of Examples 1, 6, and 11 have a significant reduction in the cumulative heat release under high voltage. The reason is that after the introduction of added salt into the positive pole piece of the present invention, the heat absorption effect during the phase change of the added salt is used to absorb the heat generated by the positive pole piece (such as the positive electrode and sulfide promoted by the positive electrode active material). The side reactions between solid electrolytes and the heat generated by exothermic processes such as the self-decomposition of sulfide solid electrolytes), thereby realizing the effective improvement of the thermal safety and cycle stability of the sulfide solid battery system.

Regarding the content of the added salt: Examples 1 to 5 adopt dry pressing process to prepare positive pole pieces, and the materials of the positive pole pieces, solid electrolyte and negative pole pieces are the same. The difference between embodiments 1 to 5 is only the addition of salt The content is different. It can be seen from Table 1 and Table 2 that increasing the content of added salt can reduce the heat release of the system; but when the added salt content is too high (for example, reaching 20% in Example 5), due to the poor ionic conductivity of the added salt, It is not conducive to the rapid transfer of lithium ions in the positive electrode layer, which will cause a slight decrease in battery performance such as the first week specific capacity and first week efficiency of the battery.

Regarding the types of added salts: Although the various added salts provided by the present invention can absorb the heat generated by the positive pole pieces and effectively improve the thermal safety and cycle stability of the sulfide solid-state battery system, when the salt material is added In the case of non-lithium materials (such as the Rb salt and Cs salt in Examples 9 and 10), the lithium content in the battery system is slightly lower than that of the battery system where the added salt is a lithium material, resulting in a faster degradation of battery performance.

In addition, it can be seen from Examples 5-15 that using a sulfide solid electrolyte material with high stability (for example, Example 6) and a positive electrode active material with better compatibility with the sulfide solid electrolyte (for example, Example 8) can be used. Further reduce the heat generated by the battery. If the content of conductive carbon in the battery system is too high, excessive conductive carbon will hinder the transfer of lithium ions in the solid-state battery and degrade the performance of the catalytic electrolyte, resulting in lower battery performance (for example, Example 7). Too high content of conductive agent and binder will also be detrimental to battery safety and battery performance (for example, Example 14).

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, the present invention is not limited to the specific embodiments disclosed and described above, and some modifications and changes to the present invention should also fall within the protection scope of the claims of the present invention. 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 present invention.

Claims (15)

1. A sulfide solid-state battery positive pole piece, in which,

   Comprising a positive electrode current collector and a positive electrode active material layer provided on at least one surface of the positive electrode current collector, the positive electrode active material layer comprising a positive electrode active material and a solid electrolyte;

   The positive active material layer further includes an added salt, and the added salt undergoes an endothermic phase change at 40-150°C.
2. The positive electrode piece of the sulfide solid state battery according to claim 1, wherein the added salt undergoes an endothermic phase change at 60-110°C.
3. The positive pole piece of the sulfide solid state battery according to claim 1 or 2, wherein the decomposition temperature of the added salt is higher than 200°C.
4. The sulfide solid-state battery positive pole piece according to any one of claims 1 to 3, wherein the added salt is selected from the group consisting of inorganic salts of alkali metals, organic salts of alkali metals, and organic-inorganic composite salts of alkali metals. At least one.
5. The positive electrode piece of the sulfide solid state battery according to claim 4, wherein the added salt is selected from M-imide; wherein, M is a cation selected from at least one of Li, Na, K, Rb, and Cs, imide Is the sulfonimide anion represented by the following formula (I),

   

   In formula (I):

   n is selected from an integer from 0 to 4;

   X and Y are each independently selected from F, Cl, Br, I or a fluorinated alkyl group having 1 to 4 carbon atoms.
6. The positive pole piece of the sulfide solid state battery according to claim 4 or 5, wherein the added salt is selected from Li[(FSO ₂ ) ₂ N], Na[(FSO ₂ ) ₂ N], K[(FSO ₂ ) ₂ N], Rb[(FSO ₂ ) ₂ N], Cs[(FSO ₂ ) ₂ N], Li[(FSO ₂ )(CF ₃ SO ₂ )N], Na[(FSO ₂ )(CF ₃ SO ₂ )N], K[(FSO ₂ )(CF ₃ SO ₂ )N], Rb[(FSO ₂ )(CF ₃ SO ₂ )N], Cs[(FSO ₂ )(CF ₃ SO ₂ )N], Li _0.4 K _0.6 [(FSO ₂ ) ₂ N], Li _0.4 Cs _0.6 [(FSO ₂ )(CF ₃ SO ₂ )N] or Li _0.8 Cs _0.2 [(FSO ₂ )(CF ₃ SO ₂ )N] At least one.
7. The positive pole piece of the sulfide solid state battery according to any one of claims 1 to 6, wherein the mass percentage of the added salt in the positive active material layer is 0.1%-20%.
8. 8. The positive electrode piece of the sulfide solid state battery according to claim 7, wherein the mass percentage of the added salt in the positive electrode active material layer is 1%-10%.
9. The sulfide solid-state battery positive pole piece according to any one of claims 1-8, wherein the positive electrode active material is selected from the group consisting of olivine structure lithium metal oxide, layered structure lithium metal oxide, spinel structure lithium At least one of metal oxides, sulfur powder, or modified materials of the foregoing materials.
10. The sulfide solid state battery positive pole piece according to any one of claims 1-9, wherein the solid electrolyte is selected from sulfide solid electrolyte.
11. The positive pole piece of a sulfide solid-state battery according to claim 10, wherein the general structural formula of the sulfide solid electrolyte is yLi ₂ S-(100-y)LS, where 0<y<100, and the LS is One or more of P ₂ S ₅ , SiS ₂ , GeS ₂ , SnS ₂ and Al ₂ S ₃ .
12. The positive pole piece of a sulfide solid-state battery according to claim 10 or 11, wherein the sulfide solid electrolyte further includes a doping material, and the general formula of the doped sulfide electrolyte is z(Li ₂ S-LS )-(100-z)LiQ, where 90≤z≤100, and the doping material LiQ is one or more of lithium halide, lithium oxide, lithium nitride, and lithium oxyacid salt.
13. The positive pole piece of a sulfide solid-state battery according to any one of claims 12, wherein, in the general formula z(Li ₂ S-LS)-(100-z)LiQ, the doping material LiQ is LiF, LiCl, LiBr, LiI, Li ₂ O, Li ₃ N, LiAlO ₂ , Li ₃ PO ₄ , Li ₂ SO ₄ , Li ₃ BO ₃ , Li ₄ SiO ₄ , LiN(SO ₂ F) ₂ , LiN(SO ₂ R _F ) ₂ and one or more of LiN(SO ₂ F)(SO ₂ R _F ), wherein the substituent R _F is a saturated perfluoroalkyl group, and its general formula is C _n F _2n+1 , and n is An integer of 1 to 2.
14. A sulfide solid-state battery, comprising: a positive pole piece, a negative pole piece, and a solid electrolyte membrane spaced between the positive pole piece and the negative pole piece, wherein the positive pole piece is claimed The sulfide solid-state battery positive pole piece described in any one of 1 to 13.
15. A device, wherein the device comprises the sulfide solid-state battery of claim 14.

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