Solid-state soft package battery and preparation method thereof

Abstract

The invention belongs to the field of solid-state batteries, and relates to a solid-state soft package battery and a preparation method thereof.The solid-state soft package battery comprises a rate type solid-state battery pole piece and a polymer-based sulfide electrolyte layer, and the rate type solid-state battery pole piece comprises a positive electrode material layer, a negative electrode material layer and a porous composite current collector; the porous composite current collector comprises a positive current collector and a negative current collector, and the positive current collector and the negative current collector are provided with through holes. The electrolyte material is filled into the through holes in the positive current collector and the negative current collector to play a role in conducting lithium ions, and Li < + > of the positive and negative material layers can be transmitted through the electrolyte in the holes of the positive and negative current collectors due to the composite porous design, so that the effective Li < + > transmission distance is shortened, the diffusion limitation of the solid-state battery is reduced, and the service life of the solid-state battery is prolonged. The rate capability of the solid-state battery is improved, and the problem of poor rate capability caused by slow lithium ion diffusion between the positive plate and the negative plate of the existing sulfide all-solid-state battery is solved.

Description

Technical Field

[0001] The present invention belongs to the field of solid-state batteries and relates to a solid-state soft-pack battery and a preparation method thereof. Background Art

[0002] The electrodes of solid-state lithium batteries often contain positive and negative electrode materials, conductive agents, and electrolytes, and are connected to form pole pieces by polymer binders. Sulfide solid electrolytes have the advantages of high ion conductivity and good flexibility, and are currently one of the best solid electrolyte materials.

[0003] However, the contact interfaces of the positive electrode powder, carbon conductive agent and electrolyte in the electrode are often point-to-point contacts, and then coated on the current collector. The force between the powder particles in the positive electrode coating needs to be maintained by an adhesive, which leads to excessive internal resistance of the electrode and the subsequent overall battery. Compared with liquid batteries, all components inside solid-state batteries are in solid-solid contact, resulting in slower lithium ion transmission than in liquid batteries, especially for thick electrodes with high energy density. Lithium ion diffusion limitation leads to poor battery rate performance and long charging time, which limits the practicality of solid-state batteries. Diffusion limitation in solid-state batteries is a key factor hindering battery rate performance. Reducing the thickness of the electrode can improve the rate performance to a certain extent, but it reduces the energy density of the battery and increases the mileage anxiety of car owners.

[0004] Therefore, a new battery electrode is needed to solve the problem of poor lithium ion transmission in existing solid-state batteries. Summary of the invention

[0005] The present invention aims to provide a solid-state soft-pack battery and a preparation method thereof, wherein the electrolyte material is filled into the holes penetrating the positive electrode current collector and the negative electrode current collector to conduct lithium ions, and the composite porous design makes the Li + It can pass through the positive and negative current collectors at the same time, thus transferring the effective Li + The transmission distance is shortened, the diffusion limitation of the solid-state battery is reduced, the rate performance of the solid-state battery is improved, and the problem of poor rate performance caused by slow diffusion of lithium ions between the positive and negative electrodes of the existing sulfide all-solid-state batteries is solved.

[0006] In a first aspect, the present invention provides a solid-state soft-pack battery, comprising a rate-type solid-state battery pole piece and a polymer-based sulfide electrolyte layer, wherein the rate-type solid-state battery pole piece comprises:

[0007] A positive electrode material layer;

[0008] Anode material layer;

[0009] A porous composite current collector, the porous composite current collector comprising an overlapping positive current collector and a negative current collector, the positive current collector and the negative current collector having through holes; the positive electrode material layer is arranged on the side of the positive electrode current collector away from the negative electrode current collector, and the negative electrode material layer is arranged on the side of the negative electrode current collector away from the positive electrode current collector.

[0010] In this embodiment, the electrolyte material is filled into the holes through the positive electrode current collector and the negative electrode current collector to conduct lithium ions. This composite porous design makes Li + It can pass through the positive and negative current collectors at the same time, thus transferring the effective Li + The shortened transmission distance reduces the diffusion limitation of solid-state batteries and improves the rate performance of solid-state batteries.

[0011] In some embodiments, the diameter of the pores on the positive electrode current collector and the negative electrode current collector is 1-500 um, and the pore gap is 750-800 um;

[0012] Preferably, the positive electrode current collector is stainless steel foil, aluminum foil or carbon-coated aluminum foil, and the negative electrode current collector is carbon-coated copper foil or stainless steel foil.

[0013] The diameter of the holes on the positive current collector and the negative current collector is 1-500um, and the pore gap is 750-800um, which can maximize the lithium ion conduction effect and reduce the transmission distance, while ensuring the mechanical strength of the positive current collector and the negative current collector.

[0014] In some embodiments, the positive electrode material layer is obtained by drying a positive electrode slurry layer, wherein the positive electrode slurry includes a positive electrode active material, a sulfide electrolyte, a binder and a conductive agent;

[0015] Preferably, the positive electrode slurry has a solid content of 50-65%;

[0016] Preferably, the weight ratio of the positive electrode active material, the sulfide electrolyte, the binder, and the conductive agent in the positive electrode slurry layer is (75-85): (12-20): (2-4): (1-2);

[0017] Preferably, the positive electrode active material is one or more of lithium cobalt oxide, lithium nickel oxide, lithium manganese oxide, lithium manganese oxide, lithium nickel manganese oxide, lithium-rich manganese-based, lithium iron manganese phosphate, lithium nickel cobalt aluminum oxide, lithium nickel cobalt manganese oxide, lithium iron phosphate, and lithium vanadium phosphate coated with lithium niobate or alumina;

[0018] Preferably, the conductive agent is one or more of vapor-grown carbon fibers, carbon nanotubes, and multi-walled carbon nanotubes;

[0019] Preferably, the negative electrode material layer is obtained by drying a negative electrode slurry, wherein the negative electrode slurry comprises a negative electrode active material, a sulfide electrolyte, a binder and a conductive agent;

[0020] Preferably, the solid content of the negative electrode slurry is 45-60%;

[0021] Preferably, the weight ratio of the negative electrode active material, the sulfide electrolyte, the binder, and the conductive agent in the negative electrode slurry layer is 70-90): (7-25): (2-4): (1-2);

[0022] Preferably, the negative electrode active material is at least one of micron silicon, nano silicon, silicon oxide, and homogeneous silicon carbon;

[0023] Preferably, the binder includes at least one of fluororubber, styrene butadiene styrene triblock copolymer, hydrogenated styrene butadiene styrene triblock copolymer, hydrogenated nitrile rubber, nitrile rubber, SEBS, polymethyl methacrylate, and polyethylene oxide;

[0024] Preferably, the sulfide electrolyte is one or more of LGPS, LPS, Li6PS5X, and LiSiPSX; wherein, in the Li6PS5X and LiSiPSX, the X is selected from at least one of F, Cl, Br, and I.

[0025] The positive electrode material layer and the negative electrode material layer composed of the materials in the above ratio have higher capacity and better electrode state.

[0026] In some embodiments, the porous composite current collector further comprises a polymer-based sulfide electrolyte layer, the polymer-based sulfide electrolyte layer comprises a porous insulating polymer substrate and an electrolyte layer coated on the surface thereof, the porous insulating polymer substrate is provided with through holes;

[0027] Preferably, the pore diameter of the porous insulating polymer substrate is 1-1000 um;

[0028] Preferably, the porous insulating polymer substrate is at least one of PET, PVDF and PTFE;

[0029] Preferably, the electrolyte layer comprises a binder and a sulfide electrolyte;

[0030] Preferably, the binder includes at least one of fluororubber, styrene butadiene styrene triblock copolymer, hydrogenated styrene butadiene styrene triblock copolymer, hydrogenated nitrile rubber, nitrile rubber, SEBS, polymethyl methacrylate, and polyethylene oxide;

[0031] Preferably, the sulfide electrolyte is one or more of LGPS, LPS, Li6PS5X, and LiSiPSX; wherein, in the Li6PS5X and LiSiPSX, X is selected from at least one of F, Cl, Br, and I.

[0032] Through composite porous design, Li + It can simultaneously pass through the positive and negative current collectors and the sulfide solid electrolyte membrane, thereby transferring the effective Li + The transmission distance is shortened by half, further reducing diffusion limitations and improving the rate performance of solid-state batteries.

[0033] In some embodiments, the rate-type solid-state battery pole pieces are arranged in n+1 layers, and the polymer-based sulfide electrolyte layers are arranged in n layers. The n+1 layers of the rate-type solid-state battery pole pieces and the n layers of the polymer-based sulfide electrolyte layers are stacked alternately, and the polymer-based sulfide electrolyte layers are arranged between the gaps formed by adjacent stacks of the rate-type solid-state battery pole pieces, and n is greater than or equal to 1.

[0034] In some embodiments, the surface capacity of the positive electrode material layer located at the outermost side of the solid-state soft-pack battery is 0.4-0.6 times the surface capacity of the positive electrode material layer located in the middle; the surface capacity of the negative electrode material layer located at the outermost side of the solid-state soft-pack battery is 0.4-0.6 times the surface capacity of the negative electrode material layer located in the middle;

[0035] Preferably, the surface capacity of the positive electrode material layer located in the middle of the solid-state soft-pack battery is 3-5 mAh / cm 2 The surface capacity of the positive electrode material layer located on the outermost side of the solid-state soft-pack battery is 1.5-2.5 mAh / cm 2 The surface capacity of the negative electrode material layer located in the middle of the solid-state soft-pack battery is 3.3-5.5 mAh / cm 2 The surface capacity of the negative electrode material layer located on the outermost side of the solid-state soft-pack battery is 1.65-2.75 mAh / cm 2 .

[0036] In this implementation, the battery capacities are more matched and overcharging and over-discharging are less likely to occur.

[0037] In a second aspect of the present invention, a method for preparing a solid-state soft-pack battery is provided, comprising the following steps:

[0038] (1) Die-cutting the rate-type solid-state battery electrode and the polymer-based sulfide electrolyte layer respectively;

[0039] (2) Alternately stacking three layers of rate-type solid-state battery pole pieces and two layers of polymer-based sulfide electrolyte layers, wherein the two layers of polymer-based sulfide electrolyte layers are respectively arranged between the gaps formed by stacking the three layers of rate-type solid-state battery pole pieces, to obtain a rate-type solid-state soft-pack battery.

[0040] In some embodiments, the method for preparing the rate-type solid-state battery electrode is:

[0041] Applying positive electrode slurry on the side of the porous composite current collector away from the negative electrode current collector to form the positive electrode material layer, and applying negative electrode slurry on the side of the negative electrode current collector away from the positive electrode current collector to form the negative electrode material layer, and drying to obtain a rate-type solid-state battery electrode sheet;

[0042] Preferably, the preparation method of the porous composite current collector is as follows: the preparation method of the porous composite current collector is as follows: after punching holes in the positive electrode current collector and the negative electrode current collector, they are respectively arranged on both sides of the polymer-based sulfide solid electrolyte layer and statically pressed.

[0043] In the prepared rate-type solid electrolyte electrode, lithium ions have two transmission directions. Both the porous composite current collector and the polymer-based sulfide electrolyte layer can conduct lithium ions, which is equivalent to shortening the transmission path of lithium ions and weakening the diffusion limitation of lithium ions in the electrode, thereby improving the battery rate performance.

[0044] The positive electrode current collector and the negative electrode current collector arranged on both sides of the polymer-based sulfide solid electrolyte layer are statically pressed at a pressure of 200-400MPa so that the three become a whole, and part of the electrolyte material in the polymer-based sulfide solid electrolyte layer is filled into the pores of the positive electrode current collector and the negative electrode current collector on both sides to form an ion path.

[0045] In some embodiments, the preparation method of the polymer-based sulfide electrolyte layer is:

[0046] The binder is dissolved in an organic solvent to obtain a glue solution; a sulfide electrolyte is added to the glue solution and mixed to obtain an electrolyte slurry; and the electrolyte slurry is coated on a porous insulating polymer substrate to obtain a polymer-based sulfide electrolyte layer.

[0047] In some embodiments, the positive electrode slurry preparation method is:

[0048] The binder is dissolved in a solvent to obtain a glue solution, and the positive electrode active material, the conductive agent, and the sulfide electrolyte are added to the glue solution and mixed to obtain a positive electrode slurry;

[0049] Preferably, the negative electrode slurry preparation method is: adding negative electrode active material and sulfide electrolyte to glue solution, mixing, and obtaining negative electrode slurry.

[0050] In summary, the present application includes at least one of the following beneficial technical effects:

[0051] The electrolyte material is filled into the holes on the positive and negative current collectors to conduct lithium ions. The composite porous design makes Li + It can pass through the positive and negative current collectors at the same time, thus transferring the effective Li + The shortened transmission distance reduces the diffusion limitation of solid-state batteries and improves the rate performance of solid-state batteries. BRIEF DESCRIPTION OF THE DRAWINGS

[0052] Figure 1 It is a schematic structural diagram of the solid-state soft-pack battery in the present invention.

[0053] Figure numerals: 1. rate-type solid-state battery electrode; 2. polymer-based sulfide electrolyte layer; 11. porous composite current collector; 111. positive electrode current collector; 112. negative electrode current collector; 113. second polymer-based sulfide solid electrolyte layer; 12. positive electrode slurry layer; 13. negative electrode slurry layer. DETAILED DESCRIPTION

[0054] The technical solution of the present invention is further described below by specific embodiments, which do not limit the protection scope of the present invention. Some non-essential modifications and adjustments made by others based on the concept of the present invention still fall within the protection scope of the present invention.

[0055] Example 1

[0056] A method for preparing a solid-state soft-pack battery comprises the following steps:

[0057] 1. Preparation of polymer-based sulfide electrolyte layer

[0058] (1) dissolving a binder fluororubber EY in an organic solvent isobutyl isobutyrate to obtain a glue solution;

[0059] In other embodiments, the binder fluororubber EY can also be replaced by other adhesives such as styrene butadiene styrene triblock copolymer, hydrogenated styrene butadiene styrene triblock copolymer, hydrogenated nitrile rubber, nitrile rubber, SEBS, polymethyl methacrylate, polyethylene oxide, nitrile rubber, hydrogenated nitrile rubber, styrene-butadiene-styrene block copolymer or a mixture of at least two thereof, which can increase the overall mechanical strength of the polymer-based sulfide electrolyte layer;

[0060] The organic solvent polymer isobutyl isobutyrate can also be replaced by other organic solvents such as toluene, xylene, anisole, isobutyl isobutyrate, butyl butyrate, hexyl butyrate, n-heptane, or a mixture of at least two of them, so as to evenly disperse the adhesive and the sulfide electrolyte.

[0061] (2) adding the sulfide electrolyte Li6PS5Cl into the gel solution and ball milling at 300 rpm for 30 min to obtain an electrolyte slurry;

[0062] In this embodiment, the solid content of the obtained electrolyte slurry is 55%, wherein the mass ratio of the sulfide electrolyte Li6PS5Cl to the adhesive fluororubber EY is m(Li6PS5Cl):m(EY)=97:3, and the solid content of the slurry is 53%.

[0063] In other embodiments, the sulfide electrolyte Li6PS5Cl can also be replaced by at least one of LGPS, LPS, Li6PS5X, LiSiPSX, or Li2SP2S5, Li 10 GeP2S 12 , Li 10 SnP2S 12 At least one of the common sulfide electrolytes or a mixture of at least two of them, wherein X is selected from at least one of F, Cl, Br or I; the ball milling time and speed can also be adjusted according to demand, and the ball milling speed is within the range of 100-350r / min, such as 350rpm ball milling for 20min, 250rpm ball milling for 35min, etc., and other mixing methods such as grinding can also be used, as long as the sulfide electrolyte and the glue can be mixed; in other embodiments, the solid content of the obtained electrolyte slurry can also be adjusted according to needs, such as 50%, 52%, 55%, 58%, 60%, etc., and the mass ratio of the sulfide electrolyte Li6PS5Cl and the adhesive fluororubber EY can also be adjusted to a suitable ratio of 95:5, 96:4, 98:2, etc.

[0064] (3) The electrolyte slurry was coated onto a porous insulating polymer substrate PET (polyethylene terephthalate) film with a pore size of 100 μm, and dried at 70° C. to obtain a polymer-based sulfide electrolyte layer.

[0065] In other embodiments, the PET film may also be a porous insulating polymer substrate made of PVDF (polyvinylidene fluoride) or PTFE (Teflon), and the pore size of the porous insulating polymer substrate may also be any size of 100-1000um, such as 110um, 120um, 125um, 134um, 156um, 570um, 600um, 700um, 750um, 800um, 900um, 1000um, etc. It can not only maximize the lithium ion conduction function, but also ensure the flexibility and mechanical strength of the electrolyte membrane.

[0066] 2. Preparation of porous composite current collector

[0067] (1) punching holes in the positive electrode current collector aluminum foil and the negative electrode current collector stainless steel foil, with a hole diameter of 100 μm and a hole spacing of 800 μm to obtain porous aluminum foil and porous stainless steel foil;

[0068] In other embodiments, the positive electrode current collector may also be a metal current collector such as stainless steel foil, aluminum foil, carbon-coated aluminum foil, and the negative electrode current collector may also be a metal current collector such as carbon-coated copper foil, stainless steel foil, etc.; the diameter of the hole may also be any size in the range of 100-500um, such as 110um, 120um, 125um, 134um, 356um, 470um, 500um, etc., and the hole spacing may also be 750um, 780um, 800um, 830um, 850um, etc.

[0069] (2) laminating a porous aluminum foil and a porous stainless steel foil on both sides of the polymer-based sulfide solid electrolyte layer, respectively, and integrating the three under a static pressure of 300 MPa to obtain a porous composite current collector;

[0070] In this embodiment, under the action of pressure, part of the electrolyte material is filled into the apertures of the foils on both sides to form an ion path;

[0071] In other embodiments, the static pressure may also be other values ​​greater than or less than 300 MPa, such as 200 MPa, 250 MPa, 380 MPa, 400 MPa, etc., as long as the porous aluminum foil, porous stainless steel foil, and polymer-based sulfide solid electrolyte layer can be made into a whole, and the electrolyte material is filled into the pores of the foils on both sides to form an ion path.

[0072] 3. Rate-type solid-state battery pole piece

[0073] (1) The binder fluororubber EY was dissolved in the solvent isobutyl isobutyrate to obtain a glue solution, and the positive electrode active material NCM83, the conductive agent VGCF, and the sulfide electrolyte Li6PS5Cl were added to the glue solution, and the positive electrode slurry was obtained by ball milling at 300 rpm for 60 min.

[0074] In this embodiment, m(NCM83):m(Li6PS5Cl):m(EY):m(VGCF)=85:15:2.5:1.5, and the solid content of the slurry is 55%.

[0075] In other embodiments, the positive electrode active material can also be replaced by one or more of lithium niobate, alumina-coated lithium cobalt oxide, lithium nickel oxide, lithium manganese oxide, lithium manganese oxide, lithium nickel manganese oxide, lithium iron manganese phosphate, lithium nickel cobalt aluminum oxide, lithium nickel cobalt manganese oxide, lithium iron phosphate, and lithium vanadium phosphate; the conductive agent can also be replaced by one or more of vapor-grown carbon fibers, carbon nanotubes, and multi-walled carbon nanotubes; the solid content of the positive electrode slurry can also be adjusted as needed, such as 50%, 55%, 56%, 57%, 58%, and 60%, and the mass ratio of the positive electrode active material, sulfide electrolyte, binder, and conductive agent can also be adjusted to any ratio within the range of (75-85): (12-20): (2-4): (1-2), such as 80:16:3:1 and other suitable ratios.

[0076] (2) The binder fluororubber EY was dissolved in isobutyl isobutyrate to obtain a glue solution, and the negative electrode active material homogeneous silicon carbon and sulfide electrolyte Li6PS5Cl were added to the glue solution, and ball milling was performed at 300 rpm for 60 min to obtain a negative electrode slurry.

[0077] In this embodiment, m(homogeneous silicon carbon):m(Li6PS5Cl):m(EY):m(VGCF)=77:20:2:1, and the solid content of the slurry is 50%.

[0078] In other embodiments of the present invention, the homogeneous silicon carbon of the negative electrode active material can also be replaced by silicon materials such as micron silicon, nano silicon, silicon oxide, etc. with equivalent functions. The solid content of the negative electrode slurry can also be adjusted as needed, such as 50%, 58%, 60%, etc. The mass ratio of the negative electrode active material to the sulfide electrolyte, binder, and conductive agent can also be adjusted to any ratio within the range of (70-90): (7-25): (2-4): (1-2).

[0079] (3) coating the positive electrode slurry on the porous aluminum foil side of the porous composite current collector and drying it at 80°C to form a positive electrode material layer; coating the negative electrode slurry on the porous stainless steel foil side of the porous composite current collector and drying it at 80°C to form a negative electrode material layer, thereby obtaining a rate-type solid-state battery electrode sheet.

[0080] In other embodiments of the present invention, all drying temperatures can be any temperature within the range of 60-90°C, such as 65°C, 73°C, 85°C, 90°C, etc.; similarly, in other embodiments of the present invention, the time and speed of ball milling of the rubber in each step can also be adjusted according to demand, and the ball milling speed is within the range of 100-350r / min, such as 350rpm ball milling for 20min, 250rpm ball milling for 35min, 150rpm ball milling for 60min, etc., and other mixing methods such as grinding can also be used, as long as the different components can be mixed.

[0081] Similarly, in other embodiments, all the binders involved in the present invention, fluororubber EY, can be replaced by styrene butadiene styrene triblock copolymer, hydrogenated styrene butadiene styrene triblock copolymer, hydrogenated nitrile rubber, nitrile rubber, SEBS, polymethyl methacrylate, polyethylene oxide, nitrile rubber, hydrogenated nitrile rubber, styrene-butadiene-styrene block copolymer or a mixture of at least two thereof, and other adhesives; the organic solvent polymer isobutyl isobutyrate can also be replaced by toluene, xylene, anisole, isobutyl isobutyrate, butyl butyrate, hexyl butyrate, n-heptane, at least one or a mixture of at least two thereof, and other organic solvents; the sulfide electrolyte can be replaced by at least one of LGPS, LPS, Li6PS5X, LiSiPSX, or Li2SP2S5, Li 10 GeP2S 12 , Li 10 SnP2S 12 At least one of the common sulfide electrolytes such as sulfide electrolytes or a mixture of at least two of them, wherein X is selected from at least one of F, Cl, Br or I.

[0082] 4. Preparation of solid-state soft-pack batteries

[0083] (1) The rate-type solid-state battery electrode and the polymer-based sulfide electrolyte layer are die-cut into a size of 9.6*12.6 cm respectively, and the area of ​​the positive electrode material region (i.e., the region formed after the positive electrode slurry layer is dried) in the battery electrode is controlled to be 9.3*12.3 cm, and the area of ​​the negative electrode material region (i.e., the region formed after the negative electrode slurry layer is dried) is controlled to be 9.6*12.6 cm;

[0084] In other embodiments, the die-cutting area may also be adjusted according to the size of the battery model.

[0085] (2) Alternately stack three-layer rate-type solid-state battery electrodes and two-layer polymer-based sulfide electrolyte layers, and arrange the two-layer polymer-based sulfide electrolyte layers between the gaps formed by the stacking of the three-layer battery electrodes, so that one side of the polymer-based electrolyte layer is the positive electrode material layer and the other side is the negative electrode material layer. The electrodes are welded and isostatically pressed at 300 MPa for 5 minutes to obtain a rate-type solid-state soft-pack battery.

[0086] In other embodiments of the present invention, the pressure and time of isostatic pressing can also be adjusted as needed, such as 200MPa isostatic pressing for 10min, 350MPa isostatic pressing for 3min, etc., as long as the three layers of battery pole pieces and the two layers of polymer-based sulfide electrolyte can be laminated into one. The rate-type solid-state soft-pack battery can also alternately stack n+1 layers of battery pole pieces and n layers of polymer-based sulfide electrolyte layers, and the n layers of polymer-based sulfide electrolyte layers are respectively arranged between the intervals formed by the stacking of n+1 layers of battery pole pieces, so that one side of the polymer-based electrolyte layer is the positive electrode active layer (positive electrode material layer), and the other side is the negative electrode active layer (negative electrode material layer).

[0087] The specific capacity of the positive electrode material of the solid-state soft-pack battery prepared in this embodiment is 210 mAh / cm 2 The specific capacity of the negative electrode material is 1700mAh / cm 2 The positive material layer in the middle layer (the positive electrode located inside the stacked three-layer battery electrode) has a surface capacity of 3 mAh / cm 2 (corresponding coating gap is 200um), the capacity of the outermost positive electrode material layer is 1.5mAh / cm 2 (The corresponding coating gap is 100um). The surface capacity of the middle layer negative electrode material layer (referring to the negative electrode located inside the stacked three-layer battery electrode) is 3.3mAh / cm 2 (corresponding to coating gap of 100um), the capacity of the outermost negative electrode material layer is 1.65mAh / cm 2 (The corresponding coating gap is 50um). In order to match the battery capacity, in case of overcharge or overdischarge, the surface capacity of the outermost electrode of the soft-pack battery is half of the middle one.

[0088] Example 2

[0089] A method for preparing a solid-state soft-pack battery, which differs from Example 1 in that: the positive electrode material layer of the middle layer of the solid-state soft-pack battery (referring to the positive electrode located on the inner side of the stacked three-layer battery electrode sheet) has a surface capacity of 4 mA / cm 2 (The corresponding coating gap is 260um), and the capacity of the outermost positive electrode material layer is 2mAh / cm 2 (The corresponding coating gap is 130um). The surface capacity of the middle layer negative electrode material layer (referring to the negative electrode located inside the stacked three-layer battery electrode) is 4.4mAh / cm 2 (corresponding to coating gap of 130um), the capacity of the outermost negative electrode material layer is 2.2mAh / cm 2 (The corresponding coating gap is 65um).

[0090] Example 3

[0091] A method for preparing a solid-state soft-pack battery, which differs from Example 1 in that: the positive electrode material layer of the middle layer of the solid-state soft-pack battery (referring to the positive electrode located on the inner side of the stacked three-layer battery electrode sheet) has a surface capacity of 5 mA / cm 2 (The corresponding coating gap is 300um), and the capacity of the outermost positive electrode material layer is 2.5mAh / cm 2 (The corresponding coating gap is 165um). The surface capacity of the middle layer negative electrode material layer (referring to the negative electrode located inside the stacked three-layer battery electrode) is 5.5mAh / cm 2 (The corresponding coating gap is 165um), and the capacity of the outermost negative electrode material layer is 2.75mAh / cm 2 (The corresponding coating gap is 85m).

[0092] like Figure 1 As shown, the solid-state soft-pack batteries in Examples 1-3 include three layers of rate-type solid-state battery pole pieces 1 and two layers of first polymer-based sulfide electrolyte layers 2. The three layers of rate-type solid-state battery pole pieces 1 and the two layers of first polymer-based sulfide electrolyte layers 2 are alternately stacked, and the two layers of first polymer-based sulfide electrolyte layers 2 are respectively arranged between the intervals formed by the three layers of rate-type solid-state battery pole pieces 1.

[0093] The rate-type solid-state battery electrode 1 includes a porous composite current collector 11, a positive electrode material layer 12, and a negative electrode material layer 13. The positive electrode material layer 12 is obtained by coating a positive electrode slurry and setting it on the front side of the porous composite current collector 11 and drying it. The negative electrode slurry layer 13 is obtained by coating a negative electrode slurry and setting it on the back side of the porous composite current collector 11, and then drying it at 70°C to obtain the rate-type solid-state battery electrode 1.

[0094] The porous composite current collector 11 includes a positive electrode current collector 111, a negative electrode current collector 112 and a second polymer-based sulfide solid electrolyte layer 113. The positive electrode current collector 111 is an aluminum foil, and the negative electrode current collector 112 is a stainless steel foil. Both the positive electrode current collector 111 and the negative electrode current collector 112 are provided with through holes with a diameter of 100 um, and the spacing between the through holes is 800 um. The positive electrode current collector 111 and the negative electrode current collector 112 are respectively attached to the front and back of the second polymer-based sulfide solid electrolyte layer 113. The positive electrode current collector 111 and the negative electrode current collector stainless steel 112 are respectively fixed to the front and back of the second polymer-based sulfide solid electrolyte layer 113 at a static pressure of 300 MPa, so that the three become a whole to form the porous composite current collector 11.

[0095] The first polymer-based sulfide electrolyte layer 2 and the second polymer-based sulfide solid electrolyte layer 113 have the same structure, both comprising a porous insulating polymer substrate 21 and an electrolyte layer 22. The porous insulating polymer substrate 21 is provided with a through hole with a pore size of 100 um. The electrolyte slurry is coated on the porous insulating polymer substrate 21 and dried at 70°C to form the electrolyte layer 22.

[0096] When assembling the solid-state soft-pack battery, the rate-type solid-state battery pole piece 1 and the first polymer-based sulfide electrolyte layer 2 are first die-cut into a size of 9.6*12.6 cm, respectively, and the area of ​​the positive electrode material layer 12 in the rate-type solid-state battery pole piece 1 is controlled to be 9.3*12.3 cm, and the area of ​​the negative electrode material layer 13 is controlled to be 9.6*12.6 cm. Then, the three-layer rate-type solid-state battery pole piece 1 and the two-layer first polymer-based sulfide electrolyte layer 2 are alternately stacked, and the two-layer polymer-based sulfide electrolyte layer 2 is respectively arranged between the intervals formed by the stacking of the three-layer rate-type solid-state battery pole piece 1, so that one side of the first polymer-based sulfide electrolyte layer 2 is the negative electrode material layer 13, and the other side is the positive electrode material layer 12. The pole ears are welded and isostatically pressed at 300 MPa for 5 minutes to obtain a rate-type solid-state soft-pack battery.

[0097] Comparative Example 1

[0098] A method for preparing a solid-state soft-pack battery comprises the following steps:

[0099] 1. Preparation of polymer-based sulfide electrolyte layer

[0100] (1) dissolving a binder fluororubber EY in isobutyl isobutyrate to obtain a glue solution;

[0101] (2) adding sulfide electrolyte Li6PS5Cl into the glue solution and ball milling at 300 rpm for 30 min to obtain electrolyte slurry, wherein the solid content of the electrolyte slurry is 55%, wherein m(Li6PS5Cl):m(EY)=97:3;

[0102] (3) coating the electrolyte slurry onto a PET membrane with a pore size of 100-1000 μm and drying at 70° C. to obtain a polymer-based sulfide electrolyte layer;

[0103] 2. Preparation of traditional double-sided positive electrode sheets and single-sided negative electrode sheets

[0104] (1) Dissolving a binder fluoropolymer EY in isobutyl isobutyrate to obtain a glue solution, adding a positive electrode active material NCM83, a conductive agent VGCF, and a sulfide electrolyte Li6PS5Cl to the glue solution, and ball milling at 300 rpm for 60 min to obtain a positive electrode slurry, wherein the solid content of the positive electrode slurry is 60%, wherein m(NCM83):m(Li6PS5Cl):m(EY):m(VGCF)=85:15:2.5:1.5;

[0105] (2) dissolving the binder fluorocarbon EY in isobutyl isobutyrate to obtain a glue solution, adding the negative electrode active material homogeneous silicon carbon and the sulfide electrolyte Li6PS5Cl into the glue solution, and ball milling at 300 rpm for 60 min to obtain a negative electrode slurry, wherein the solid content of the negative electrode slurry is 55%, and m(homogeneous silicon carbon):m(Li6PS5Cl):m(EY):m(VGCF)=77:20:2:1;

[0106] (3) The positive electrode slurry is coated on the surface of the aluminum foil and dried at 70°C. Then, the positive electrode slurry is coated on the other side of the aluminum foil to obtain a double-sided positive electrode sheet. The surface capacity of the double-sided positive electrode is 6 mAh / cm 2 Similarly, the negative electrode slurry was coated on one side of the stainless steel foil and dried at 70°C to obtain a single-sided negative electrode sheet with a single-sided negative electrode surface capacity of 3.3 mAh / cm 2 ;

[0107] 3. Preparation of solid-state soft-pack batteries

[0108] (1) die-cutting a double-sided positive electrode sheet, a single-sided negative electrode sheet and a polymer-based sulfide electrolyte layer, wherein the size of the obtained double-sided positive electrode sheet is 9.3*12.3 cm, and the size of the obtained single-sided negative electrode sheet and the polymer-based sulfide electrolyte layer is 9.6*12.6 cm;

[0109] (2) The single-sided negative electrode sheet, polymer-based sulfide electrolyte layer, double-sided positive electrode sheet, polymer-based electrolyte membrane layer, and single-sided negative electrode sheet are stacked in sequence, the tabs are welded, and the battery is isostatically pressed at 300 MPa for 5 minutes to obtain a rate-type solid-state soft-pack battery.

[0110] Comparative Example 2

[0111] A method for preparing a solid-state soft-pack battery, which differs from Comparative Example 1 in that the double-sided positive electrode surface capacity is 8 mA / cm 2 The single-sided negative electrode surface capacity is 4.4 mAh / cm 2 .

[0112] Comparative Example 3

[0113] A method for preparing a solid-state soft-pack battery, which differs from Comparative Example 1 in that the double-sided positive electrode surface capacity is 10 mA / cm 2 The single-sided negative electrode surface capacity is 5.5 mAh / cm 2 .

[0114] Comparative Example 4

[0115] A method for preparing a solid-state soft-pack battery, which differs from Example 1 in that when preparing an electrode sheet, the electrolyte slurry in Example 1 is directly applied to the back of a porous aluminum foil or a porous stainless steel foil, and then the porous aluminum foil or the porous stainless steel foil coated with the electrolyte slurry on one side is dried, and then the porous aluminum foil, the electrolyte layer, and the porous stainless steel foil are pressed into a porous composite current collector by a pressure of 200MPa, the electrolyte layer is between the porous aluminum foil and the porous stainless steel foil, the positive electrode slurry is applied to the porous aluminum foil side of the porous composite current collector, and the negative electrode slurry is applied to the porous stainless steel foil side of the porous composite current collector, and the electrode sheet of a multiplier type solid-state battery is obtained by drying at 70°C. When assembling a solid-state soft-pack battery, the electrolyte slurry is directly applied to the aluminum foil current collector, and then peeled off to obtain a polymer-free electrolyte membrane to replace the polymer-based electrolyte layer.

[0116] As a result, the process is not only more complicated, but the success rate of the step of peeling the electrolyte membrane from the aluminum foil current collector to obtain a polymer-free electrolyte membrane is extremely low, which increases the production cost. In addition, since the electrolyte layer lacks the support of the porous insulating polymer substrate, the mechanical strength is low, which is not convenient for subsequent battery assembly. The electrolyte membrane without polymer support is prone to defects during processing, resulting in micro-short circuits during the battery charging and discharging process.

[0117] Comparative Example 5

[0118] A method for preparing a solid-state soft-pack battery, which differs from Example 1 in that the positive electrode active layer (the positive electrode located on the inner side of the stacked three-layer battery pole piece) of the middle layer of the rate-type solid-state soft-pack battery has a surface capacity of 3 mAh / cm 2 The capacity of the outermost positive electrode active layer is 2 mAh / cm 2 The surface capacity of the middle negative electrode active layer (the negative electrode located inside the stacked three-layer battery electrode) is 3.3 mAh / cm 2 The capacity of the outermost negative electrode active layer is 1 mAh / cm 2 The obtained solid-state soft-pack battery was overcharged and over-discharged.

[0119] Performance Testing

[0120] 1. Use the Xinwei test cabinet to test the battery charge and discharge, the charge and discharge range is 2-4.25V, the test temperature is 55℃, the test pressure is 100MPa, and the test results are shown in Table 1:

[0121] Table 1 Charge and discharge test results

[0122]

[0123]

[0124] As can be seen from Table 1, the difference between Examples 1, 2, and 3 is that the surface load of the pole piece is different. From Example 1 to Example 3, and Comparative Example 1 to Comparative Example 3, as the surface load of the pole piece increases, the rate performance of the battery gradually decreases. The difference between Example 1 and Comparative Example 1, Example 2 and Comparative Example 2, and Example 3 and Comparative Example 3 is that the structure of the pole piece is different. The battery capacity and rate performance of the battery using the rate-type solid electrolyte pole piece are better than those of the battery with the traditional pole piece. It can be found from Comparative Examples 2 and 3 that when the single-sided positive electrode surface load is greater than 4 mAh / cm 2 When the battery is overcharged at 2C, a short circuit occurs. This is because lithium ions can only be transmitted in one direction in the traditional electrode. In the thick electrode with high surface loading, the lithium ion transmission path is long and the speed is slow. Lithium ions are easily accumulated on the surface of the negative electrode, and long dendrites cause the battery to short-circuit. In the current-rate solid-state electrolyte electrode, lithium ions have two transmission directions, and the porous composite current collector and the electrolyte layer can conduct lithium ions, which is equivalent to shortening the transmission path of lithium ions, weakening the diffusion limitation of lithium ions in the electrode, and improving the battery rate performance.

[0125] Compared with Example 1, Comparative Example 4 removes the polymer substrate in the polymer-based electrolyte membrane, which results in a more complicated battery preparation process. The success rate of the step of peeling the electrolyte membrane from the aluminum foil current collector to obtain a polymer-free electrolyte membrane is extremely low, which increases the production cost. In addition, since the electrolyte layer lacks the support of the porous insulating polymer substrate, the mechanical strength is low, which is not convenient for subsequent battery assembly. The electrolyte membrane without polymer-based support is prone to defects during processing, resulting in micro-short circuits during the battery charge and discharge process, and the battery initial efficiency is low.

[0126] Compared with Example 1, in Comparative Example 5, the ratio of the surface capacity of the negative electrode to the surface capacity of the positive electrode of the battery is less than 1, resulting in lithium deposition on the surface of the negative electrode, short circuit during battery charging, and low initial efficiency.

[0127] It is to be understood that the present invention is described by some embodiments, and it is known to those skilled in the art that various changes or equivalent substitutions may be made to these features and embodiments without departing from the spirit and scope of the present invention. In addition, under the teachings of the present invention, these features and embodiments may be modified to adapt to specific circumstances and materials without departing from the spirit and scope of the present invention. Therefore, the present invention is not limited by the specific embodiments disclosed herein, and all embodiments falling within the scope of the claims of this application are within the scope of protection of the present invention.

Claims

1. A solid-state soft-pack battery, characterized in that: It includes a rate-type solid-state battery pole piece and a polymer-based sulfide electrolyte layer, and the rate-type solid-state battery pole piece includes: A positive electrode material layer; Anode material layer; A porous composite current collector, the porous composite current collector comprising an overlapping positive current collector and a negative current collector, the positive current collector and the negative current collector having through holes; the positive electrode material layer is arranged on the side of the positive electrode current collector away from the negative electrode current collector, and the negative electrode material layer is arranged on the side of the negative electrode current collector away from the positive electrode current collector.

2. The solid-state soft-pack battery according to claim 1, characterized in that: The diameter of the holes on the positive electrode current collector and the negative electrode current collector is 1-500 um, and the pore gap is 750-800 um; Preferably, the positive electrode current collector is stainless steel foil, aluminum foil or carbon-coated aluminum foil, and the negative electrode current collector is carbon-coated copper foil or stainless steel foil.

3. The solid-state soft-pack battery according to claim 1, characterized in that: The positive electrode material layer is obtained by drying the positive electrode slurry, wherein the positive electrode slurry includes a positive electrode active material, a sulfide electrolyte, a binder and a conductive agent; Preferably, the positive electrode slurry has a solid content of 50-65%; Preferably, the weight ratio of the positive electrode active material, the sulfide electrolyte, the binder, and the conductive agent in the positive electrode slurry layer is (75-85): (12-20): (2-4): (1-2); Preferably, the positive electrode active material is one or more of lithium cobalt oxide, lithium nickel oxide, lithium manganese oxide, lithium manganese oxide, lithium nickel manganese oxide, lithium-rich manganese-based, lithium iron manganese phosphate, lithium nickel cobalt aluminum oxide, lithium nickel cobalt manganese oxide, lithium iron phosphate, and lithium vanadium phosphate coated with lithium niobate or alumina; Preferably, the conductive agent is one or more of vapor-grown carbon fibers, carbon nanotubes, and multi-walled carbon nanotubes; Preferably, the negative electrode material layer is obtained by drying a negative electrode slurry, wherein the negative electrode slurry comprises a negative electrode active material, a sulfide electrolyte, a binder and a conductive agent; Preferably, the solid content of the negative electrode slurry is 45-60%; Preferably, the weight ratio of the negative electrode active material, the sulfide electrolyte, the binder, and the conductive agent in the negative electrode slurry layer is 70-90): (7-25): (2-4): (1-2); Preferably, the negative electrode active material is at least one of micron silicon, nano silicon, silicon oxide, and homogeneous silicon carbon; Preferably, the binder includes at least one of fluororubber, styrene butadiene styrene triblock copolymer, hydrogenated styrene butadiene styrene triblock copolymer, hydrogenated nitrile rubber, nitrile rubber, SEBS, polymethyl methacrylate, and polyethylene oxide; Preferably, the sulfide electrolyte is one or more of LGPS, LPS, Li6PS5X, and LiSiPSX; wherein, in the Li6PS5X and LiSiPSX, the X is selected from at least one of F, Cl, Br, and I.

4. The solid-state soft-pack battery according to claim 1, characterized in that: The porous composite current collector further comprises a polymer-based sulfide electrolyte layer, wherein the polymer-based sulfide electrolyte layer comprises a porous insulating polymer substrate and an electrolyte layer coated on the surface thereof, wherein the porous insulating polymer substrate is provided with through holes; Preferably, the pore diameter of the porous insulating polymer substrate is 1-1000 um; Preferably, the porous insulating polymer substrate is at least one of PET, PVDF and PTFE; Preferably, the electrolyte layer comprises a binder and a sulfide electrolyte; Preferably, the binder includes at least one of fluororubber, styrene butadiene styrene triblock copolymer, hydrogenated styrene butadiene styrene triblock copolymer, hydrogenated nitrile rubber, nitrile rubber, SEBS, polymethyl methacrylate, and polyethylene oxide; Preferably, the sulfide electrolyte is one or more of LGPS, LPS, Li6PS5X, and LiSiPSX; wherein, in the Li6PS5X and LiSiPSX, X is selected from at least one of F, Cl, Br, and I.

5. The solid-state soft-pack battery according to claim 1, characterized in that: The rate-type solid-state battery pole pieces are arranged in n+1 layers, and the polymer-based sulfide electrolyte layers are arranged in n layers. The n+1 layers of the rate-type solid-state battery pole pieces and the n layers of the polymer-based sulfide electrolyte layers are stacked alternately, and the polymer-based sulfide electrolyte layers are arranged between the gaps formed by stacking adjacent rate-type solid-state battery pole pieces, and n is greater than or equal to 1.

6. The solid-state soft-pack battery according to any one of claims 1 to 5, characterized in that: The surface capacity of the positive electrode material layer located at the outermost side of the solid-state soft-pack battery is 0.4-0.6 times the surface capacity of the positive electrode material layer located in the middle; the surface capacity of the negative electrode material layer located at the outermost side of the solid-state soft-pack battery is 0.4-0.6 times the surface capacity of the negative electrode material layer located in the middle; Preferably, the surface capacity of the positive electrode material layer located in the middle of the solid-state soft-pack battery is 3-5 mAh / cm 2 The surface capacity of the positive electrode material layer located on the outermost side of the solid-state soft-pack battery is 1.5-2.5 mAh / cm 2 The surface capacity of the negative electrode material layer located in the middle of the solid-state soft-pack battery is 3.3-5.5 mAh / cm 2 The surface capacity of the negative electrode material layer located on the outermost side of the solid-state soft-pack battery is 1.65-2.75 mAh / cm 2 .

7. A method for preparing a solid-state soft-pack battery according to any one of claims 1 to 6, characterized in that: The following steps are involved: (1) Die-cutting the rate-type solid-state battery electrode and the polymer-based sulfide electrolyte layer respectively; (2) Alternately stacking three layers of rate-type solid-state battery pole pieces and two layers of polymer-based sulfide electrolyte layers, wherein the two layers of polymer-based sulfide electrolyte layers are respectively arranged between the gaps formed by stacking the three layers of rate-type solid-state battery pole pieces, to obtain a rate-type solid-state soft-pack battery.

8. The preparation method according to claim 7, characterized in that: The method for preparing the rate-type solid-state battery electrode is as follows: Applying positive electrode slurry on the side of the porous composite current collector away from the negative electrode current collector to form the positive electrode material layer, and applying negative electrode slurry on the side of the negative electrode current collector away from the positive electrode current collector to form the negative electrode material layer, and drying to obtain a rate-type solid-state battery electrode sheet; Preferably, the preparation method of the porous composite current collector is as follows: the preparation method of the porous composite current collector is as follows: after punching holes in the positive electrode current collector and the negative electrode current collector, they are respectively arranged on both sides of the polymer-based sulfide solid electrolyte layer.

9. The preparation method according to claim 7, characterized in that: The preparation method of the polymer-based sulfide electrolyte layer is: The binder is dissolved in an organic solvent to obtain a glue solution; a sulfide electrolyte is added to the glue solution and mixed to obtain an electrolyte slurry; and the electrolyte slurry is coated on a porous insulating polymer substrate to obtain a polymer-based sulfide electrolyte layer.

10. The preparation method according to claim 8, characterized in that: The positive electrode slurry preparation method is: The binder is dissolved in a solvent to obtain a glue solution, and the positive electrode active material, the conductive agent, and the sulfide electrolyte are added to the glue solution and mixed to obtain a positive electrode slurry; Preferably, the negative electrode slurry preparation method is: adding negative electrode active material and sulfide electrolyte to glue solution, mixing, and obtaining negative electrode slurry.

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