Cathode sheet, solid-state battery and electric apparatus

Abstract

The present disclosure relates to a cathode sheet. The cathode sheet comprises: a current collector and an active layer, wherein the active layer is arranged on at least one surface of the current collector, the active layer comprises a core layer and a surrounding layer arranged around the core layer, and the conductivity of the surrounding layer is greater than the conductivity of the core layer.

Description

Positive electrode sheet, solid-state battery and electric device

[0001] Priority information

[0002] The present disclosure claims priority to the Chinese patent application No. 202411381005.3, filed on September 27, 2024, entitled "Positive electrode sheet, solid-state battery and electric device", and incorporates it herein by reference in its entirety. TECHNICAL FIELD

[0003] The present disclosure relates to the technical field of batteries, and in particular, to a positive electrode sheet, an energy storage device and an electric device. BACKGROUND

[0004] At present, solid-state batteries exhibit an increasingly important research position in the field of new batteries due to excellent safety performance. As one of the components of solid-state batteries, solid-state electrolytes have poor wettability, and therefore need to be mixed with active materials and conductive agents to prepare a slurry during the preparation of the positive electrode. Due to particle barriers, the connection between solid-state electrolytes is reduced, resulting in low ionic conductivity of the positive electrode, and the prepared battery can only be charged and discharged at a small rate. With the improvement of the performance of electric products, the demand for high-energy-density solid-state batteries is increasing day by day, which also means that the positive electrode load is becoming higher and higher. The flowability of solid-state electrolytes is much lower than that of liquid electrolytes, resulting in significant differences in the transmission of lithium ions in the positive electrode. The higher the thickness of the positive electrode, the more difficult it is for lithium ions to transmit near the current collector, which seriously affects the rate performance and capacity of the battery.

[0005] Therefore, how to optimize the lithium ion diffusion path of high-load electrode sheets in all directions and achieve high-rate and long-cycle performance of the battery has become a hot and key issue in the field of solid-state batteries. SUMMARY

[0006] The present disclosure aims to at least partially solve one of the technical problems in the related art.

[0007] The first aspect of the present disclosure provides a positive electrode sheet. According to the embodiments of the present disclosure, the positive electrode sheet comprises a current collector (100) and a composite active layer, the composite active layer is arranged on at least one surface of the current collector (100), the composite active layer comprises an intermediate layer and a surrounding layer (400) arranged around the intermediate layer, and the electrical conductivity of the surrounding layer (400) is greater than that of the intermediate layer. According to the positive electrode sheet of the embodiments of the present disclosure, by making the electrical conductivity of the positive electrode sheet around higher than that of the middle part, the problem that the lithium ion diffusion speed around the positive electrode sheet is slower than that in the middle part due to uneven heat distribution can be solved, and the battery capacity and cycle performance can be improved.

[0008] According to embodiments of the present disclosure, the positive electrode plate can further have the following additional technical features:

[0009] According to embodiments of the present disclosure, the intermediate layer has a smaller electrical conductivity on the side away from the current collector (100) than on the side close to the current collector (100), and the surrounding layer (400) has a larger electrical conductivity than the intermediate layer on the side close to the current collector (100).

[0010] According to embodiments of the present disclosure, the intermediate layer comprises: a first electrical conductivity active layer (200) disposed on one surface of the current collector (100), and a second electrical conductivity active layer (300) disposed on the surface of the first electrical conductivity active layer (200) away from the current collector (100); the surrounding layer (400) is disposed at least around the periphery of the second electrical conductivity active layer (300) and is in contact with the second electrical conductivity active layer (300); wherein the first electrical conductivity active layer (200) has a larger electrical conductivity than the second electrical conductivity active layer (300).

[0011] According to embodiments of the present disclosure, the surrounding layer (400) is disposed on the surface of the first electrical conductivity active layer (200) away from the current collector (100).

[0012] According to embodiments of the present disclosure, the thickness of the surrounding layer (400) is the same as the thickness of the second electrical conductivity active layer (300).

[0013] According to embodiments of the present disclosure, the orthographic projection of the second electrical conductivity active layer (300) on the current collector (100) overlaps the orthographic projection of the first electrical conductivity active layer (200) on the current collector (100), the surrounding layer (400) is further disposed around the periphery of the first electrical conductivity active layer (200) and is in contact with the first electrical conductivity active layer (200).

[0014] According to embodiments of the present disclosure, the thickness of the surrounding layer (400) is the same as the sum of the thicknesses of the first electrical conductivity active layer (200) and the second electrical conductivity active layer (300).

[0015] According to embodiments of the present disclosure, the thickness of the surrounding layer (400) is 100 μm-450 μm.

[0016] According to embodiments of the present disclosure, the thickness of the second electrical conductivity active layer (300) is 100 μm-250 μm.

[0017] According to embodiments of the present disclosure, the first electrical conductivity active layer (200) has a thickness of 100-200 pm.

[0018] According to embodiments of the present disclosure, the positive electrode tab has a thickness of 206-465 pm.

[0019] According to embodiments of the present disclosure, the area ratio of the wraparound layer (400) to the first electrical conductivity active layer (200) is (10-40): 100.

[0020] According to embodiments of the present disclosure, the area ratio of the wraparound layer (400) to the first electrical conductivity active layer (200) is (15-25): 100.

[0021] According to embodiments of the present disclosure, the area ratio of the wraparound layer (400) to the first electrical conductivity active layer (200) is (10-40):(90-60).

[0022] According to embodiments of the present disclosure, the area ratio of the wraparound layer (400) to the first electrical conductivity active layer (200) is (10-20):(90-80).

[0023] According to embodiments of the present disclosure, the first electrical conductivity active layer (200) comprises a first active material, a first conductive agent, a first binder, and a first solid-state electrolyte.

[0024] According to embodiments of the present disclosure, the second electrical conductivity active layer (300) comprises a second active material, a second conductive agent, a second binder, and a second solid-state electrolyte.

[0025] According to embodiments of the present disclosure, the wraparound layer (400) comprises a third active material, a third conductive agent, a third binder, and a third solid-state electrolyte.

[0026] According to embodiments of the present disclosure, the third solid-state electrolyte has a greater electrical conductivity than the first solid-state electrolyte, and the first solid-state electrolyte has a greater electrical conductivity than the second solid-state electrolyte.

[0027] According to embodiments of the present disclosure, the first active material, the first conductive agent, the first binder, and the first solid-state electrolyte have a mass ratio of (60-90):(1-10):(0-3):(0-30).

[0028] According to embodiments of the present disclosure, the second active material, the second conductive agent, the second binder, and the second solid-state electrolyte have a mass ratio of (60-90):(1-10):(0-3):(0-30).

[0029] According to embodiments of the present disclosure, the mass ratio of the third active material, the third conductive agent, the third binder, and the third solid-state electrolyte is (60-90):(1-10):(0-3):(0-30).

[0030] According to embodiments of the present disclosure, the first solid-state electrolyte, the second solid-state electrolyte, and the third solid-state electrolyte each independently comprises at least one of an oxide solid-state electrolyte, a sulfide solid-state electrolyte, a halide solid-state electrolyte, and a polymer solid-state electrolyte, and at least one of the following conditions is met: the D50 of the oxide solid-state electrolyte, the sulfide solid-state electrolyte, and the halide solid-state electrolyte particles is 0.5-50 μm; and the weight percentage of the polymer solid-state electrolyte in the third solid-state electrolyte is 10%-100%. 50 respectively; and the weight percentage of the polymer solid-state electrolyte in the third solid-state electrolyte is 10%-100%.

[0031] In a second aspect of the present disclosure, a solid-state battery is provided. According to embodiments of the present disclosure, the solid-state battery comprises the positive electrode sheet of the first aspect.

[0032] In a third aspect of the present disclosure, an electric device is provided. According to embodiments of the present disclosure, the electric device comprises the solid-state battery of the second aspect.

[0033] Additional aspects and advantages of the present disclosure will be in part apparent and in part pointed out hereinafter. BRIEF DESCRIPTION OF DRAWINGS

[0034] The above and / or additional aspects and advantages of the present disclosure will become apparent and be readily appreciated from the following description, including the appended drawings, wherein:

[0035] FIG. 1 is a first structure of a positive electrode sheet according to embodiments of the present disclosure;

[0036] FIG. 2 is a first structure of a positive electrode sheet according to embodiments of the present disclosure;

[0037] FIG. 3 is a second structure of a positive electrode sheet according to embodiments of the present disclosure;

[0038] FIG. 4 is a second structure of a positive electrode sheet according to embodiments of the present disclosure;

[0039] Reference signs: 100: current collector; 200: first conductivity active layer; 300: second conductivity active layer; 400: wrap-around layer. DETAILED DESCRIPTION

[0040] Embodiments of the present disclosure are described in detail below. The embodiments described below are exemplary only, and are not intended to be limiting of the present disclosure.

[0041] It should be noted that the terms "first", "second" are used only for descriptive purposes, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of the technical features indicated. Therefore, the features defined with "first", "second" can explicitly or implicitly include one or more of the features. Further, in the description of the present disclosure, the meaning of "a plurality of" is two or more, unless otherwise specified.

[0042] The endpoints of the ranges and any values disclosed in the present disclosure are not limited to the precise values stated. The ranges or values should be construed to be roughly around the ranges or values. For ranges of values, the endpoints of the ranges are combined with the individual points to form new ranges or values, which are to be considered as being specifically disclosed in the present disclosure.

[0043] In the present disclosure, the term "comprising" or "including" is an open-ended expression, i.e., including the indicated content of the present disclosure, but not excluding other aspects.

[0044] Commercialized lithium-ion batteries use organic liquid electrolytes, which have the risk of leakage and explosion. Solid-state electrolytes greatly improve the safety performance of batteries due to their non-flammable nature, so all-solid-state lithium batteries using solid electrolytes instead of liquid electrolytes have gained more and more attention in recent years.

[0045] For batteries, the key to improving energy density lies in improving the loading of electrode active materials. With the increase of the loading and thickness of the positive electrode, the transport of lithium ions and electrons is more severely limited, and serious polarization occurs due to the significant increase in charge transport distance. Since the heat generated by the battery during charging and discharging cannot be evenly distributed throughout the positive electrode in time, the temperature in the middle of the positive electrode is higher than that in the surrounding, resulting in slower lithium ion transport rate and higher polarization around the positive electrode, and serious attenuation of the electrode sheet after long cycle.

[0046] To improve the above problems, the prior art mainly proceeds from two aspects. One is the modification of the positive electrode material, which coats high ionic conductivity materials on the surface of the active material or dopes heteroatoms into the active material, optimizing the transport of lithium ions at the interface, but the coating / doping process is complex, and the coating / doping amount is uncontrollable, resulting in significant differences in local ionic conductivity. The other is the optimization of the formulation, which adjusts the composition and proportion of the active material, electrolyte and conductive agent to improve the diffusion mode of lithium ions in it, but the improvement of ionic conductivity is limited.

[0047] Therefore, the present disclosure provides a positive electrode tab. According to an embodiment of the present disclosure, the positive electrode tab comprises: a current collector and a composite active layer, the composite active layer is arranged on at least one surface of the current collector, the composite active layer comprises an intermediate layer and a surrounding layer arranged around the intermediate layer, and the electrical conductivity of the surrounding layer is greater than that of the intermediate layer. According to the positive electrode tab of the embodiment of the present disclosure, by making the electrical conductivity of the periphery of the positive electrode tab greater than that of the middle part, the problem that the lithium ion diffusion speed of the periphery of the positive electrode tab is slower than that of the middle part due to uneven heat distribution can be solved, and the battery capacity and cycle performance can be improved.

[0048] According to an embodiment of the present disclosure, the electrical conductivity of the side of the intermediate layer away from the current collector is less than that of the side of the intermediate layer close to the current collector, and the electrical conductivity of the surrounding layer is greater than that of the side of the intermediate layer close to the current collector. By making the electrical conductivity of the side of the intermediate layer away from the current collector less than that of the side of the intermediate layer close to the current collector, a gradient of increasing ion conductivity can be formed in the middle part of the positive electrode tab, which can improve the utilization rate of the active material, improve the capacity, balance the charge distribution, reduce the polarization, optimize the lithium ion transmission path, and thus improve the rate performance of the battery.

[0049] It should be noted that the positional relationship of the intermediate layer and the surrounding layer described above is defined for the same side of the current collector, and the above definition is also applicable to the other side.

[0050] According to an embodiment of the present disclosure, the intermediate layer comprises: a first electrical conductivity active layer arranged on one surface of the current collector; a second electrical conductivity active layer arranged on the surface of the first electrical conductivity active layer away from the current collector; and the surrounding layer arranged at least around the periphery of the second electrical conductivity active layer and in contact with the second electrical conductivity active layer, wherein the electrical conductivity of the first electrical conductivity active layer is greater than that of the second electrical conductivity active layer.

[0051] According to the positive electrode tab of the embodiment of the present disclosure, by making the electrical conductivity of the surrounding layer greater than that of the intermediate layer, the electrical conductivity of the periphery of the positive electrode tab is the highest, and thus the problem that the lithium ion diffusion speed of the periphery of the positive electrode tab is slower than that of the middle part due to uneven heat distribution can be solved, and the battery capacity and cycle performance can be improved. In addition, the electrical conductivity of the first electrical conductivity active layer is greater than that of the second electrical conductivity active layer, and the second electrical conductivity active layer is arranged on the surface of the first electrical conductivity active layer away from the current collector, so that the electrical conductivity of the positive electrode tab in the middle part has an upward trend from the second electrical conductivity active layer to the current collector, and thus the utilization rate of the active material and the capacity can be improved, the charge in the depth direction of the electrode tab can be balanced and the polarization can be reduced, the lithium ion transmission path can be optimized and the rate performance of the battery can be improved.

[0052] It should be noted that the positive electrode tab of the present disclosure has two structures, which will be described in detail below.

[0053] The first structure of the positive electrode tab, referring to FIG. 1 and FIG. 2, the positive electrode tab comprises: a current collector 100, a first conductivity active layer 200, a second conductivity active layer 300 and a surrounding layer 400. Among them, the first conductivity active layer 200 is arranged on one surface of the current collector 100, the second conductivity active layer 300 and the surrounding layer 400 are arranged on the surface of the first conductivity active layer 200 away from the current collector 100, and the surrounding layer 400 is arranged around the four sides of the second conductivity active layer 300, and the surrounding layer 400 is arranged in contact with the second conductivity active layer 300. Therefore, this structure can form a gradient of increasing ionic conductivity from the second conductivity active layer 300 to the current collector 100 in the middle of the positive electrode tab, which can improve the utilization rate of active materials, increase the capacity, reduce the polarization, and improve the battery rate performance; at the same time, the conductivity of the positive electrode tab around is the highest, which can solve the problem that the lithium ion diffusion speed of the positive electrode tab around is slower than that of the middle of the positive electrode tab due to uneven heat distribution, and further improve the battery capacity and cycle performance.

[0054] In some embodiments of the present disclosure, in the first structure, the thickness of the surrounding layer is the same as the thickness of the second conductivity active layer. Therefore, the manufacturing process can be simplified to ensure the consistency of the structure, so that the product quality is easier to control in the production process.

[0055] In some embodiments of the present disclosure, in the first structure, the thickness of the second conductivity active layer is 100-250 μm. For example, it can be 100 μm, 150 μm, 200 μm or 250 μm, etc., or it can be a range composed of any of the above values. Therefore, the thickness of the second conductivity active layer in the above range can ensure that sufficient active material is provided, increase the energy storage capacity of the battery, and at the same time reduce the phenomenon of tab cracking and polarization increasing dramatically.

[0056] In some embodiments of the present disclosure, in the first structure, the thickness of the first conductivity active layer is 100-200 μm. For example, it can be 100 μm, 150 μm or 200 μm, etc., or it can be a range composed of any of the above values. Therefore, the thickness of the first conductivity active layer in the above range is conducive to the stability of the structure and the improvement of its peel strength with the current collector, improves the current collection efficiency of the current collector, reduces the internal resistance, improves the power density of the battery, and at the same time, the diffusion distance of lithium ions is shorter, which can reduce the polarization, so as to maintain a lower overpotential during high-rate charging and discharging.

[0057] In some embodiments of the present disclosure, in the first structure, the thickness of the surrounding layer is 100-250 μm. For example, it can be 100 μm, 150 μm, 200 μm, 250 μm, or the like, or a range consisting of any of the above values. Therefore, the surrounding layer in the above range can ensure stable drying of the surrounding layer, while providing sufficient active material to increase the energy storage capacity of the battery and ensure effective diffusion of ions during battery charging and discharging.

[0058] In some embodiments of the present disclosure, in the first structure, the thickness of the positive electrode tab is 206-465 μm. For example, it can be 206 μm, 250 μm, 305 μm, 350 μm, 380 μm, 395 μm, 420 μm, 465 μm, or the like, or a range consisting of any of the above values.

[0059] In some embodiments of the present disclosure, in the first structure, the area ratio of the surrounding layer to the first conductivity active layer is (10-40): 100. For example, it can be 10: 100, 15: 100, 20: 100, 25: 100, 30: 100, 35: 100, 40: 100, or the like, or a range consisting of any of the above values. In some embodiments of the present disclosure, the area ratio of the surrounding layer to the first conductivity active layer is (15-25): 100. Thus, the area ratio of the surrounding layer to the first conductivity active layer in the above range can enable the surrounding layer to more completely cover the area with low ion conductivity due to heat diffusion, while reducing the problems of excessive internal voids, cracking, and material loss of the positive electrode tab, as well as the probability of generating a large number of irreversible cracks inside after long cycles.

[0060] It should be noted that, in the first structure, the second conductivity active layer and the surrounding layer are both located on the surface of the first conductivity active layer away from the current collector, i.e., the area of the first conductivity active layer is the sum of the areas of the second conductivity active layer and the surrounding layer. When the area ratio of the surrounding layer to the first conductivity active layer is defined, the area ratio of the second conductivity active layer to the first conductivity active layer can be obtained by calculation.

[0061] Referring to FIGS. 3 and 4, the positive electrode tab includes a current collector 100, a first conductivity active layer 200, a second conductivity active layer 300, and a surrounding layer 400. The first conductivity active layer 200 is disposed on one surface of the current collector 100, the second conductivity active layer 300 is disposed on a surface of the first conductivity active layer 200 away from the current collector 100, and the orthographic projection of the second conductivity active layer 300 on the current collector 100 overlaps the orthographic projection of the first conductivity active layer 300 on the current collector 100. The surrounding layer 400 is disposed around the first conductivity active layer 200 and the second conductivity active layer 300, and the surrounding layer 400 is in contact with the first conductivity active layer 200 and the second conductivity active layer 300. Therefore, the structure can form a gradient of increasing ionic conductivity from the second conductivity active layer 300 to the current collector 100 in the middle of the positive electrode tab, which can improve the utilization of active materials, increase the capacity, reduce polarization, and improve the rate capability of the battery. At the same time, the conductivity of the positive electrode tab around is the highest, which can solve the problem that the lithium ion diffusion speed around the positive electrode tab is slower than that in the middle of the positive electrode tab due to uneven heat distribution, and further improve the capacity performance and cycle performance of the battery.

[0062] In some embodiments of the present disclosure, in the second structure, the thickness of the surrounding layer is the same as the sum of the thicknesses of the first conductivity active layer and the second conductivity active layer. Thereby, the structural integrity of the positive electrode tab is enhanced, the stress concentration caused by inconsistent thickness is reduced, and the manufacturing process is simplified to ensure the consistency of the structure.

[0063] In some embodiments of the present disclosure, in the second structure, the thickness of the second conductivity active layer is 100 μm-250 μm. For example, it can be 100 μm, 150 μm, 200 μm, or 250 μm, or a range composed of any of the above values. Therefore, the thickness of the second conductivity active layer in the above range can ensure sufficient active material to increase the energy storage capacity of the battery, while reducing the phenomenon of cracking of the tab and dramatic increase of polarization.

[0064] In some embodiments of the present disclosure, in the second structure, the thickness of the first conductivity active layer is 100 μm-200 μm. For example, it can be 100 μm, 150 μm, or 200 μm, or a range composed of any of the above values. Therefore, the thickness of the first conductivity active layer in the above range is conducive to structural stability and improving the peel force of the first conductivity active layer and the current collector, improving the current collection efficiency of the current collector, reducing the internal resistance, improving the power density of the battery, and reducing polarization, thereby maintaining a lower overpotential during high-rate charging and discharging.

[0065] In some embodiments of the present disclosure, in the second structure, the thickness of the surrounding layer is 200-450 μm. For example, it can be 200 μm, 250 μm, 300 μm, 350 μm, 400 μm or 450 μm, etc., or can be a range consisting of any of the above values. Therefore, the thickness of the surrounding layer is in the above range, which can ensure stable drying of the surrounding layer, while providing sufficient active material to increase the energy storage capacity of the battery and ensure effective diffusion of ions during charging and discharging of the battery.

[0066] In some embodiments of the present disclosure, in the second structure, the thickness of the positive electrode tab is 206-465 μm. For example, it can be 206 μm, 250 μm, 305 μm, 350 μm, 380 μm, 395 μm, 420 μm, 465 μm, etc., or can be a range consisting of any of the above values.

[0067] In some embodiments of the present disclosure, in the second structure, the area ratio of the surrounding layer to the first conductivity active layer is (10-40):(90-60). For example, it can be 10:90, 15:85, 20:80, 25:75, 30:70, 35:65 or 40:60, etc., or can be a range consisting of any of the above values. In some embodiments of the present disclosure, the area ratio of the surrounding layer to the first conductivity active layer is (10-20):(90-80). Thus, the area ratio of the surrounding layer to the first conductivity active layer is in the above range, which can enable the surrounding layer to completely cover the area with low ion conductivity caused by heat diffusion, while reducing the problems of excessive internal voids, cracking and material loss of the positive electrode tab, and the probability of generating a large number of irreversible cracks inside the battery after long cycle.

[0068] It should be noted that in the second structure, the orthographic projection of the second conductivity active layer on the current collector overlaps with the orthographic projection of the first conductivity active layer on the current collector, i.e., the area of the second conductivity active layer is the same as that of the first conductivity active layer, and the area ratio of the second conductivity active layer to the surrounding layer can be obtained after the area ratio of the first conductivity active layer to the surrounding layer is defined.

[0069] In some embodiments of the present disclosure, the current collector is a conventional component in the art, and the thickness of the current collector can be selected by a person skilled in the art according to the actual situation. For example, the thickness of the current collector used in the present disclosure is 6-15 μm. For example, it can be 6 μm, 8 μm, 10 μm, 12 μm, 14 μm or 15 μm, etc., or can be a range consisting of any of the above values.

[0070] In some embodiments of the present disclosure, the thickness of the current collector, the thickness of the first conductivity active layer, the thickness of the second conductivity active layer and the thickness of the surrounding layer can be measured by a screw micrometer.

[0071] In some embodiments of the present disclosure, the first conductivity active layer comprises a first active material, a first conductive agent, a first binder, and a first solid-state electrolyte. The mass ratio of the first active material, the first conductive agent, the first binder, and the first solid-state electrolyte is (60-90):(1-10):(0-3):(0-30). For example, it can be 60:5:2:10, 65:6:1:30, 70:8:3:7, 75:10:2:20, 82:2:2:14, 90:1:3:25, or a range composed of any of the above values. Thus, the first conductivity active layer prepared by using the above ratio has good electronic conductivity and high energy density, while maintaining the mechanical stability and structural integrity of the positive electrode sheet.

[0072] In some embodiments of the present disclosure, the second conductivity active layer comprises a second active material, a second conductive agent, a second binder, and a second solid-state electrolyte. The mass ratio of the second active material, the second conductive agent, the second binder, and the second solid-state electrolyte is (60-90):(1-10):(0-3):(0-30). For example, it can be 60:5:2:10, 65:6:1:30, 70:8:3:7, 75:10:2:20, 82:2:2:14, 90:1:3:25, or a range composed of any of the above values. Thus, the second conductivity active layer prepared by using the above ratio has good electronic conductivity and high energy density, while maintaining the mechanical stability and structural integrity of the positive electrode sheet.

[0073] In some embodiments of the present disclosure, the surrounding layer comprises a third active material, a third conductive agent, a third binder, and a third solid-state electrolyte. The mass ratio of the third active material, the third conductive agent, the third binder, and the third solid-state electrolyte is (60-90):(1-10):(0-3):(0-30). For example, it can be 60:5:2:10, 65:6:1:30, 70:8:3:7, 75:10:2:20, 82:2:2:14, 90:1:3:25, or a range composed of any of the above values. Thus, the surrounding layer prepared by using the above ratio has good electronic conductivity and high energy density, while maintaining the mechanical stability and structural integrity of the positive electrode sheet.

[0074] In the prior art, the active material near the current collector cannot fully participate in the electrochemical reaction, thus the capacity cannot be fully utilized. This exacerbates the instability of the electrode structure and accelerates the deterioration of the electrochemical-mechanical coupling of the electrode. In addition, the solid-state electrolyte in the positive electrode directly affects the ion transport and stability in the positive electrode, and is an important factor affecting the capacity utilization and retention rate of the battery. Therefore, the present disclosure optimizes the lithium ion transport path by regulating the electrical conductivity of the solid-state electrolyte at different positions in the active layer, thereby improving the rate performance of the battery. That is, in the present disclosure, the electrical conductivity of the third solid-state electrolyte is greater than that of the first solid-state electrolyte, and the electrical conductivity of the first solid-state electrolyte is greater than that of the second solid-state electrolyte. In this way, the ion conductivity of the surrounding layer in the active layer can be greater than that of the first conductivity active layer, and the ion conductivity of the first conductivity active layer can be greater than that of the second conductivity active layer.

[0075] It should be noted that the mass ratio of the first active material, the first conductive agent, the first binder and the first solid-state electrolyte in the first conductivity active layer, the mass ratio of the second active material, the second conductive agent, the second binder and the second solid-state electrolyte in the second conductivity active layer, and the mass ratio of the third active material, the third conductive agent, the third binder and the third solid-state electrolyte in the surrounding layer can be the same or different, as long as the ion conductivity of the surrounding layer is greater than that of the first conductivity active layer, and the ion conductivity of the first conductivity active layer is greater than that of the second conductivity active layer.

[0076] In some embodiments of the present disclosure, the first active material, the second active material and the third active material are conventional materials in the art, and a person skilled in the art can select the specific types of the first active material, the second active material and the third active material according to the actual situation, for example, lithium cobaltate (LiCoO2), lithium nickelate (LiNiO2), lithium iron phosphate (LiFePO4), lithium cobalt phosphate (LiCoPO4), lithium manganese phosphate (LiMnPO4), lithium nickel phosphate (LiNiPO4), lithium manganate (LiMnO2), binary material LiNi x A (1-x) O2(Wherein, A is selected from one of Co, Mn, 0 m B n C (1-m-n) O2(Wherein, B, C are independently selected from at least one of Co, Al, Mn, and B and C are not the same, 0

[0077] In some embodiments of the present disclosure, the first conductive agent, the second conductive agent and the third conductive agent are conventional components in the art, and a person skilled in the art can select the specific types of the first conductive agent, the second conductive agent and the third conductive agent according to actual conditions, for example, at least one of acetylene black, Super P, Super S, graphene, carbon fiber, carbon nanotube and Ketjen black can be independently selected.

[0078] In some embodiments of the present disclosure, the first binder, the second binder and the third binder are conventional materials in the art, and a person skilled in the art can select the specific types of the first binder, the second binder and the third binder according to actual conditions, for example, at least one of polyvinylidene fluoride (PVDF), vinylidene fluoride-hexafluoropropylene copolymer (PVDF-HFP), polytetrafluoroethylene (PTFE), polyacrylonitrile (PAN), polypropylene carbonate (PPC), polyethylene oxide (PEO) and ethylene oxide-propylene oxide copolymer (PEO-PO) can be independently selected.

[0079] In some embodiments of the present disclosure, the first solid-state electrolyte, the second solid-state electrolyte and the third solid-state electrolyte are conventional materials in the art, and a person skilled in the art can select the specific types of the first solid-state electrolyte, the second solid-state electrolyte and the third solid-state electrolyte according to actual conditions, for example, at least one of oxide solid-state electrolyte, sulfide solid-state electrolyte, halide solid-state electrolyte and polymer solid-state electrolyte can be independently selected.

[0080] It should be noted that the difference in ionic conductivity of the first conductivity active layer, the second conductivity active layer and the surrounding layer of the present disclosure is caused by the difference in ionic conductivity of the solid-state electrolyte in each layer. Among them, the first solid-state electrolyte, the second solid-state electrolyte and the third solid-state electrolyte can be the same or different, when the first solid-state electrolyte, the second solid-state electrolyte and the third solid-state electrolyte are the same, the ionic conductivity of the solid-state electrolyte can be adjusted by controlling the particle size, composition and other factors of the solid-state electrolyte, as long as the ionic conductivity of the surrounding layer is greater than that of the first conductivity active layer, and the ionic conductivity of the first conductivity active layer is greater than that of the second conductivity active layer.

[0081] In some embodiments of the present disclosure, the D50 of the oxide solid-state electrolyte, the sulfide solid-state electrolyte and the halide solid-state electrolyte particles is 0.5-50 μm, respectively. For example, it can be 0.5 μm, 1 μm, 5 μm, 10 μm, 20 μm, 30 μm, 40 μm or 50 μm, etc., or can be a range consisting of any of the above values. Therefore, by making the D50 of the particles in the above range, the ion conduction channels of the solid-state electrolyte can be increased, the ion mobility and the overall ionic conductivity can be improved, and at the same time, the contact area between the solid-state electrolyte and the active material can be increased, the interfacial impedance can be reduced, and thus the charge and discharge performance of the electrode can be improved. In some embodiments of the present disclosure, the D50 of the oxide solid-state electrolyte, the sulfide solid-state electrolyte and the halide solid-state electrolyte particles is 0.5-10 μm, respectively. In some embodiments of the present disclosure, the D50 of the oxide solid-state electrolyte, the sulfide solid-state electrolyte and the halide solid-state electrolyte particles is 0.5-5 μm, respectively.

[0082] In the present disclosure, the volume average particle size D50 refers to the particle size corresponding to the cumulative volume distribution percentage of 50%, for example, the volume average particle size D50 test method can refer to the standard GB / T 19077-2016, and is determined using a laser particle size analyzer (for example, Malvern Master Size 3000).

[0083] In some embodiments of the present disclosure, the oxide solid-state electrolyte is a conventional electrolyte in the art, and a person skilled in the art can select the specific type of the oxide solid-state electrolyte according to the actual situation. For example, it can be at least one of AB2(MO4)3 (A includes an alkali metal, B includes Ge, Zr, Ti or V, M includes i, Mo or P), Li 1.3 Al 0.3 Ti 1.7 (PO4)3(LATP), Li 0.5 La 0.5 TiO3(LLTO), Li5La3M2O 12 (M includes Ta, Nb or Zr), Li x M 1-y A y S4 (M includes Si or Ge, A includes P, Al, Zn, Ga or Sb), LiAlO2.

[0084] In some embodiments of the present disclosure, the sulfide solid-state electrolyte is a conventional electrolyte in the art, and a person skilled in the art can select the specific type of the sulfide solid-state electrolyte according to the actual situation. For example, it can be Li6PS5Br, Li7P3S 11 , Li 10 GeP2S 12Li6PS5Cl, Li 6+x P 1-x Ge x S5I(x = 0~1), Li6PS5Cl x Br 1-x (x = 0~1), Li6PS5Cl x Br 1-x (x = 0~1), Li5PS4X2(X includes Cl, Br or I), xLi2S·(100-x)P2S5(60≤x≤80), Li 9.54 Si 1.74 P 1.44 S 11.7 C l0.3 , Li 10 MP2S 12 (M includes Si, Ge or Sn), Li5PS4X2(X includes Cl, Br or I).

[0085] In some embodiments of the present disclosure, the halide solid-state electrolyte is a conventional electrolyte in the art, and a person skilled in the art can select the specific type of halide solid-state electrolyte according to actual needs, and exemplarily, it can be Li3ErX6(X includes Cl, Br or I), Li3LaI6, Li3LuCl6, Li3InBr 6-x Cl x (x≤4), Li3InBr3Cl3, Li3InBr6, Li3InCl6, LiInBr4, CsSnCl3, Li x ScCl 3+x (x = 0~0.6), Li3ScX6(X includes Cl, Br or I), Li 3-x Er 1-x Zr x Cl6(x≤0.6), Li 3-x Y 1-x Zr x Cl6(x≤0.6), Li3YX6(X includes Cl, Br or I), Li3Y 1-x In x Cl6(0≤x<1).

[0086] In some embodiments of the present disclosure, the polymer solid-state electrolyte includes at least one of a polymer main chain, a lithium salt and a plasticizer.

[0087] In some embodiments of the present disclosure, the mass ratio of the polymer backbone, the lithium salt and the plasticizer is (30-60):(10-50):(0-50). For example, it can be 30:10:25, 35:25:40, 40:20:30, 45:10:20, 50:25:10, 55:30:40 or 60:45:50, etc., or it can be a range consisting of any of the above values. Thus, the polymer solid-state electrolyte can have excellent ion transport performance, good flexibility and film-forming property.

[0088] In some embodiments of the present disclosure, the polymer backbone is a conventional material in the art, and a person skilled in the art can select the specific type of the polymer backbone according to the actual situation. For example, it can be at least one of polyvinylidene fluoride (PVDF), polyvinylidene fluoride-hexafluoropropylene copolymer (PVDF-HFP), polytetrafluoroethylene (PTFE), polyacrylonitrile (PAN), polypropylene carbonate (PPC), polyethylene oxide (PEO) and ethylene oxide-propylene oxide copolymer (PEO-PO).

[0089] In some embodiments of the present disclosure, the molecular weight of the polymer backbone is 10000-600000 g / mol. For example, it can be 10000 g / mol, 50000 g / mol, 100000 g / mol, 200000 g / mol, 300000 g / mol, 400000 g / mol, 500000 g / mol or 600000 g / mol, etc., or it can be a range consisting of any of the above values. Thus, by making the molecular weight of the polymer backbone within the above range, the polymer solid-state electrolyte can have better tensile strength and toughness.

[0090] In some embodiments of the present disclosure, the lithium salt is a conventional material in the art, and a person skilled in the art can select the specific type of the lithium salt according to the actual situation. For example, it can be one or more of organic lithium salt, inorganic lithium salt, such as LiPF6, LiBF4, LiClO4, LiAsF6, LiTFSI, LiFSI, LiBOB, LiDFOB, LiTFOP.

[0091] In some embodiments of the present disclosure, the plasticizer is a conventional material in the art, and a person skilled in the art can select a specific type of plasticizer according to actual needs. For example, the plasticizer can be at least one of N-methylpyrrolidone, N,N-dimethylformamide, N,N-dimethylacetamide, ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, dipropyl carbonate, methyl ethyl carbonate, ethylene glycol dimethyl ether, ethylene glycol diethyl ether, ethylene glycol methyl ethyl ether, diethylene glycol dimethyl ether, triethylene glycol dimethyl ether, tetraethylene glycol dimethyl ether, 1,3-dioxolane, 1,4-dioxane, butanedinitrile (SN), and polyethylene glycol dimethyl ether with a molecular weight less than 1000.

[0092] In some embodiments of the present disclosure, the weight percentage of the polymer solid-state electrolyte in the third solid-state electrolyte is 10% to 100%. For example, the weight percentage can be 10%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, 90%, or 100%, or a range formed by any of the above values. Therefore, by setting the weight percentage of the polymer solid-state electrolyte in the above range, the surrounding layer has better stability, and the overall stability is improved.

[0093] In some embodiments of the present disclosure, the current collector 100 is a conventional component in the art, and a person skilled in the art can select a specific type of current collector 100 according to actual needs. For example, an aluminum foil, a foamed aluminum, a carbon-coated aluminum foil, a carbon mesh, or a carbon cloth can be used.

[0094] In some embodiments of the present disclosure, the ion conductivity test method of each active layer is as follows: taking the first conductivity active layer as an example, the positive electrode slurry of the first conductivity active layer is uniformly coated on one surface of a terylene resin (PET) material by scraping, and after heating and baking to remove the solvent, a positive electrode film of the first conductivity active layer is obtained. The positive electrode film is coated on the release surface of the PET, and is removed when assembling the button cell. A button cell is made using a steel sheet-electrolyte-positive electrode film-electrolyte-steel sheet structure, and is incubated at 50-80°C for 20-40 min to promote interface fusion. Finally, the ion conductivity of the positive electrode sheet is tested by an electrochemical workstation-EIS program, and the calculation formula is as follows:

[0095] σ = L / (SR)

[0096] Wherein σ represents the ion conductivity of the positive electrode sheet, L represents the thickness of the positive electrode sheet, S represents the area of the steel sheet, and R represents the resistance of the positive electrode sheet.

[0097] In some embodiments of the present disclosure, a method for testing the ionic conductivity of the composite active layer on the positive electrode tab: the three layers of conductivity active layer (surrounding layer, first conductivity active layer and second conductivity active layer) are uniformly coated on one surface of the PET material by a special coating process, and then the composite active layer is peeled off from the release surface of the PET. The ionic conductivity of the composite active layer is tested according to the single layer method.

[0098] The second aspect of the present disclosure provides a solid-state battery, which comprises the positive electrode tab of the first aspect of the present disclosure.

[0099] In some embodiments of the present disclosure, the solid-state battery comprises a positive electrode tab, a negative electrode tab and an electrolyte. During the charging and discharging process of the solid-state battery, active ions are embedded and extracted between the positive electrode tab and the negative electrode tab. The electrolyte plays a role in conducting ions between the positive electrode tab and the negative electrode tab.

[0100] In some embodiments of the present disclosure, the negative electrode tab comprises a negative electrode current collector and a negative electrode active layer disposed on at least one side surface of the negative electrode current collector, and the negative electrode active layer comprises a negative electrode active material, a conductive agent and a binder.

[0101] In some embodiments of the present disclosure, the negative electrode current collector can be a metal foil or a composite current collector. For example, as a metal foil, a copper foil can be used. The composite current collector can include a polymer material base layer and a metal layer formed on at least one surface of the polymer material base material. The composite current collector can be formed by forming a metal material (copper, copper alloy, nickel, nickel alloy, etc.) on a polymer material base material (such as a base material of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), etc.).

[0102] In some embodiments of the present disclosure, the negative electrode active material can use a negative electrode active material known in the art for a battery. As an example, the negative electrode active material can include at least one of the following materials: graphite, soft carbon, hard carbon, silicon-based material, tin-based material, etc. The silicon-based material can include at least one of elemental silicon, silicon oxide compound, silicon-carbon composite, silicon-nitrogen composite and silicon alloy. The tin-based material can include at least one of elemental tin, tin oxide compound and tin alloy.

[0103] In some embodiments of the present disclosure, the binder can include at least one of styrene butadiene rubber (SBR), polyacrylic acid (PAA), sodium polyacrylate (PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), polymethacrylic acid (PMAA) and carboxymethyl chitosan (CMCS).

[0104] In some embodiments of the present disclosure, the conductive agent can include at least one of superconducting carbon, acetylene black, carbon black, ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0105] In some embodiments of the present disclosure, the negative active layer can further optionally include other auxiliary agents, such as a thickening agent, a plasticizer including at least one of ethylene glycol dimethyl ether, ethylene glycol diethyl ether, propylene glycol dimethyl ether, propylene glycol diethyl ether, diethylene glycol dimethyl ether, triethylene glycol dimethyl ether, tetraethylene glycol dimethyl ether, diethylene glycol diethyl ether, triethylene glycol diethyl ether, tetraethylene glycol diethyl ether, dipropylene glycol dimethyl ether, tripropylene glycol dimethyl ether, tetrapropylene glycol dimethyl ether, dipropylene glycol diethyl ether, tripropylene glycol diethyl ether, tetrapropylene glycol diethyl ether, 1,3-dioxolane, 1,4-dioxane, propylene carbonate, ethylene carbonate, diethyl carbonate, or dimethyl carbonate, butanedinitrile, and hexanedinitrile.

[0106] In some embodiments of the present disclosure, the negative electrode tab includes lithium metal and / or a lithium metal alloy.

[0107] In some embodiments of the present disclosure, the electrolyte is as previously described, including at least one of an oxide solid-state electrolyte, a sulfide solid-state electrolyte, a halide solid-state electrolyte, and a polymer solid-state electrolyte.

[0108] In some embodiments of the present disclosure, the solid-state battery can include an outer package. The outer package is used to package the positive electrode tab, the negative electrode tab, and the electrolyte.

[0109] In some embodiments of the present disclosure, the outer package can include a housing and a cover plate. The housing can include a bottom plate and a side plate connected to the bottom plate, and the bottom plate and the side plate enclose a receiving cavity. The housing has an opening in communication with the receiving cavity, and the cover plate can be provided on the opening to close the receiving cavity.

[0110] In some embodiments of the present disclosure, the outer package of the solid-state battery can be a hard shell, such as a hard plastic shell, an aluminum shell, a steel shell.

[0111] The outer package of the solid-state battery can also be a soft package, such as a bag-type soft package. The material of the soft package can be plastic, such as including at least one of polypropylene (PP), polybutylene terephthalate (PBT), and polybutylene succinate (PBS).

[0112] The solid-state battery of the present disclosure can include a solid-state battery cell form, a solid-state battery module form, and a solid-state battery pack form. In some embodiments, the solid-state battery cells can be assembled into a solid-state battery module, and the number of solid-state battery cells contained in the solid-state battery module can be one or more, and the specific number can be selected by those skilled in the art according to the application and capacity of the solid-state battery module. In some embodiments, the solid-state battery module can also be assembled into a solid-state battery pack, and the number of battery modules contained in the solid-state battery pack can be one or more, and the specific number can be selected by those skilled in the art according to the application and capacity of the solid-state battery pack.

[0113] The third aspect of the present disclosure provides a power utilization device. According to the embodiments of the present disclosure, the power utilization device includes the solid-state battery of the foregoing second aspect. Thus, the power utilization device of the present disclosure has high efficiency of energy output and excellent service life and safety performance.

[0114] The solid-state battery cell, the solid-state battery module, and the solid-state battery pack can be used as a power source of a power utilization device, or can be used as an energy storage unit of a power utilization device. The power utilization device can include a mobile device (such as a mobile phone, a notebook computer, etc.), an electric vehicle (such as a pure electric vehicle, a hybrid electric vehicle, a plug-in hybrid electric vehicle, an electric bicycle, an electric scooter, an electric golf cart, an electric truck, etc.), an electric train, a ship and a satellite, an energy storage system, etc., but is not limited thereto.

[0115] As a power utilization device, a solid-state battery cell, a solid-state battery module, or a solid-state battery pack can be selected according to the use requirements thereof.

[0116] The power utilization device as one embodiment can be a pure electric vehicle, a hybrid electric vehicle, a plug-in hybrid electric vehicle, etc. In order to meet the requirements of high power and high energy density of the solid-state battery for the power utilization device, a solid-state battery pack or a solid-state battery module can be used.

[0117] The device as another embodiment can be a mobile phone, a tablet computer, a notebook computer, etc. The device usually requires thinning, and a solid-state battery cell can be used as a power source.

[0118] The solutions of the present disclosure will be explained below in combination with examples. Those skilled in the art will understand that the examples below are only used to illustrate the present disclosure, and should not be regarded as limiting the scope of the present disclosure. If the specific techniques or conditions are not specified in the examples, the techniques or conditions described in the literature in the art or according to the product instructions are used. If the reagents or instruments are not specified by the manufacturer, they are all conventional products that can be obtained by purchase.

[0119] Example 1

[0120] The structure of the positive electrode tab is shown in FIGS. 1 and 2, and LiNi0.8 Co 0.1 Mn 0.1 O2 is an active material, Super P is a conductive agent, PVDF is a binder, LATP is an oxide solid-state electrolyte, Li6PS5Cl is a sulfide solid-state electrolyte, PEO+LiTFSI+SN (SPE) is a polymer solid-state electrolyte, and the 8-μm aluminum foil is a current collector.

[0121] The mass ratios of the active materials, conductive agents, binders, and solid-state electrolytes in the first conductivity active layer, the second conductivity active layer, and the surrounding layer are the same.

[0122] The mass ratio of the active material, conductive agent, binder, and solid-state electrolyte is 82:2:2:14.

[0123] The mass ratio of PEO, LiTFSI, and SN in the SPE is 50:25:25.

[0124] The structure of the positive electrode tab is the first structure, in which:

[0125] The first conductivity active layer has a thickness of 120 μm, and the solid-state electrolyte is Li6PS5Cl (abbreviated as S111). The D50 of S111 is 2 μm.

[0126] The second conductivity active layer has a thickness of 150 μm, and the solid-state electrolyte is Li6PS5Cl (abbreviated as S121). The D50 of S121 is 1 μm.

[0127] The surrounding layer has a thickness of 150 μm, and the solid-state electrolyte is Li6PS5Cl (abbreviated as S131) and SPE (abbreviated as P132). The D50 of S131 is 3 μm, the molecular weight of PEO in P132 is 200,000 g / mol, and the mass ratio of S131 to P132 is 9:1.

[0128] The area ratio of the surrounding layer to the first conductivity active layer is 20:100.

[0129] Example 2

[0130] The structure of the positive electrode tab and the raw materials are the same as in Example 1, and the mass ratios of the active materials, conductive agents, binders, and solid-state electrolytes are the same as in Example 1.

[0131] The first conductivity active layer has a thickness of 120 μm, and the solid-state electrolyte is Li6PS5Cl (abbreviated as S211) and LATP (abbreviated as S212). The D50 of S211 is 2 μm, and the D50 of S212 is 10 μm. The mass ratio of S211 to S212 is 9:1.

[0132] The second conductivity active layer has a thickness of 150 μm and a solid-state electrolyte of Li6PS5Cl (S221) and LATP (S222). The D50 of S221 is 1 μm and the D50 of S222 is 5 μm. The mass ratio of S211 and S212 is 8:2.

[0133] The surrounding layer has a thickness of 150 μm and a solid-state electrolyte of Li6PS5Cl (S231) and SPE (S232). The D50 of S131 is 3 μm and the PEO molecular weight in S232 is 200000 g / mol. The mass ratio of S131 and S232 is 9:1.

[0134] The area ratio of the surrounding layer to the first conductivity active layer is 20:100.

[0135] Example 3

[0136] The structure and raw materials of the positive electrode tab are the same as those in Example 1, and the mass ratio of the active material, the conductive agent, the binder, and the solid-state electrolyte is the same as that in Example 1, that is, the mass ratio of the active material, the conductive agent, the binder, and the solid-state electrolyte is 82:2:2:14.

[0137] The first conductivity active layer has a thickness of 120 μm and a solid-state electrolyte of Li6PS5Cl (S311) and SPE (S312). The D50 of S311 is 2 μm and the PEO molecular weight in S312 is 100000 g / mol. The mass ratio of S311 and S312 is 9:1.

[0138] The second conductivity active layer has a thickness of 150 μm and a solid-state electrolyte of Li6PS5Cl (S321) and SPE (S322). The D50 of S321 is 1 μm and the PEO molecular weight in S322 is 100000 g / mol. The mass ratio of S321 and S322 is 8:2.

[0139] The surrounding layer has a thickness of 150 μm and a solid-state electrolyte of Li6PS5Cl (S331) and SPE (S332). The D50 of S331 is 3 μm and the PEO molecular weight in S332 is 200000 g / mol. The mass ratio of S331 and S332 is 9:1.

[0140] The area ratio of the surrounding layer to the first conductivity active layer is 20:100.

[0141] Example 4

[0142] The structure and composition of the positive electrode tab are the same as those in Example 3, and the difference is that the area ratio of the surrounding layer to the first conductivity active layer is 10:100.

[0143] Example 5

[0144] The structure and composition of the positive electrode tab are the same as in Example 3, except that the area ratio of the surround layer to the first conductivity active layer is 40: 100.

[0145] Example 6

[0146] The structure and composition of the positive electrode tab are the same as in Example 3, except that the area ratio of the surround layer to the first conductivity active layer is 40: 100.

[0147] The first conductivity active layer has a thickness of 120 μm; the second conductivity active layer has a thickness of 150 μm; and the surround layer has a thickness of 270 μm.

[0148] The area ratio of the surround layer to the first conductivity active layer is 10: 90.

[0149] Example 7

[0150] The structure and composition of the positive electrode tab are the same as in Example 6, except that the area ratio of the surround layer to the first conductivity active layer is 15: 85.

[0151] Example 8

[0152] The structure and composition of the positive electrode tab are the same as in Example 6, except that the area ratio of the surround layer to the first conductivity active layer is 40: 60.

[0153] Example 9

[0154] The structure and composition of the positive electrode tab are the same as in Example 3, except that the area ratio of the active layers is the same as in Example 3, and only the thickness of each active layer is different. The first conductivity active layer has a thickness of 100 μm; the second conductivity active layer has a thickness of 100 μm; and the surround layer has a thickness of 100 μm.

[0155] Example 10

[0156] The structure and composition of the positive electrode tab are the same as in Example 3, except that the area ratio of the active layers is the same as in Example 3, and only the thickness of each active layer is different. The first conductivity active layer has a thickness of 200 μm; the second conductivity active layer has a thickness of 250 μm; and the surround layer has a thickness of 250 μm.

[0157] Example 11

[0158] The structure and composition of the positive electrode tab are the same as in Example 6, except that the area ratio of the active layers is the same as in Example 6, and only the thickness of each active layer is different. The first conductivity active layer has a thickness of 100 μm; the second conductivity active layer has a thickness of 100 μm; and the surround layer has a thickness of 200 μm.

[0159] Example 12

[0160] The structure and composition of the positive electrode sheet are the same as in Example 6, the area ratio of the active layers is the same as in Example 6, and only the thickness of each active layer is different. The first conductivity active layer has a thickness of 200 μm, the second conductivity active layer has a thickness of 250 μm, and the surrounding layer has a thickness of 450 μm.

[0161] Example 13

[0162] The specific embodiment is the same as in Example 1, except that the surrounding layer uses a single solid-state electrolyte, which is as follows:

[0163] The first conductivity active layer has a thickness of 120 μm, and the solid-state electrolyte is Li6PS5Cl (abbreviated as S111), and the D50 of S111 is 2 μm.

[0164] The second conductivity active layer has a thickness of 150 μm, and the solid-state electrolyte is Li6PS5Cl (abbreviated as S121), and the D50 of S121 is 1 μm.

[0165] The surrounding layer has a thickness of 150 μm, and the solid-state electrolyte is Li6PS5Cl (abbreviated as S131), and the D50 of S131 is 3 μm.

[0166] Example 14

[0167] The specific embodiment is the same as in Example 1, except that only the second conductivity active layer and the surrounding layer are included, which are as follows:

[0168] The second conductivity active layer has a thickness of 150 μm, and the solid-state electrolyte is Li6PS5Cl (abbreviated as S121), and the D50 of S121 is 1 μm.

[0169] The surrounding layer has a thickness of 150 μm, and the solid-state electrolyte is Li6PS5Cl (abbreviated as S131) and SPE (abbreviated as P132). The D50 of S131 is 3 μm, the molecular weight of PEO in P132 is 200000 g / mol, and the mass ratio of S131 to P132 is 9:1.

[0170] The area ratio of the surrounding layer to the second conductivity active layer is 20:80.

[0171] Comparative Example 1

[0172] The raw materials of the positive electrode sheet are the same as those of the first conductivity active layer in Example 1, except that the positive electrode sheet only has one active layer, and the specific process is as follows:

[0173] LiNi 0.8 Co 0.1 Mn 0.1O2 is an active material, Super P is a conductive agent, PVDF is a binder, Li6PS5Cl is a solid-state electrolyte, the active material, the conductive agent, the binder and the solid-state electrolyte are mixed uniformly according to a mass ratio of 82:2:2:14, the slurry is directly uniformly coated on the current collector by a doctor blade, and baking for a certain time to obtain a composite positive electrode sheet with a thickness of 270 μm.

[0174] Comparative Example 2

[0175] The structure and raw materials of the positive electrode sheet are the same as those of Example 3, and the difference lies in that the types of solid-state electrolytes of the first conductivity active layer, the second conductivity active layer and the surrounding layer, and the formula of the positive electrode sheet are consistent with those of the first conductivity active layer of Example 3, and the specific conditions are as follows:

[0176] The first conductivity active layer has a thickness of 120 μm, and the solid-state electrolyte is Li6PS5Cl (referred to as SD11) and SPE (referred to as SD12). The D50 of SD11 is 2 μm, and the PEO molecular weight in SD12 is 100000 g / mol; the mass ratio of SD11 and SD12 is 9:1.

[0177] The second conductivity active layer has a thickness of 150 μm, and the solid-state electrolyte is Li6PS5Cl (referred to as SD21) and SPE (referred to as SD22). The D50 of SD21 is 2 μm, and the PEO molecular weight in SD22 is 100000 g / mol; the mass ratio of SD21 and SD22 is 9:1.

[0178] The surrounding layer has a thickness of 150 μm, and the solid-state electrolyte is Li6PS5Cl (referred to as SD31) and SPE (referred to as SD32). The D50 of SD31 is 2 μm, and the PEO molecular weight in SD32 is 100000 g / mol; the mass ratio of SD31 and SD32 is 9:1.

[0179] The specific differences of Examples 1-14 are shown in Table 1.

[0180] Table 1

[0181] I. Materials used for battery assembly:

[0182] The positive electrode is the positive electrode sheet obtained by the present patent;

[0183] The solid-state electrolyte is Li6PS5Cl, and the thickness is 40 μm, wherein the mass ratio of Li6PS5Cl and the binder PVDF is 99:1;

[0184] The negative electrode coating layer is a pure silicon material, and the thickness is 25 μm, wherein the mass ratio of pure silicon and the binder PVDF is 96:4;

[0185] The negative current collector is pure copper with a thickness of 10 μm.

[0186] II. Assembling of button cell for ion conductivity test

[0187] Take button cell shell of model 2025 and steel sheet with a diameter of 16 mm, which are dried after removing impurities by ultrasonic deionized water and ethanol; assemble the cell in the order of negative shell, steel sheet, solid electrolyte, positive film, solid electrolyte, steel sheet, and positive shell. The assembled cell is sealed by a sealing machine under a pressure of 700 PMa for 5 s. Then the prepared button cell is incubated at 60°C for 20 min to promote interface fusion. Finally, the ion conductivity of the positive electrode sheet is tested by an electrochemical workstation-EIS program.

[0188] III. Assembling of soft package battery for electrochemical performance test

[0189] First, the positive electrode sheet and the negative electrode sheet are welded with tabs; then the cut solid electrolyte sheet is transferred to the negative electrode sheet by a roller press; then the positive electrode sheet is neatly stacked on the surface of the solid electrolyte to form a sandwich structure; then the aluminum plastic film is wrapped, and the soft package battery to be tested is obtained after sealing under vacuum.

[0190] IV. Ion conductivity test process and program setting

[0191] (1) Test environment preparation: adjust the constant temperature oven to 25°C;

[0192] (2) Balance the battery temperature: connect the test line of the electrochemical workstation into the oven, put the measured battery into the oven, connect the electrochemical workstation, and start testing after the oven and battery temperatures completely reach the test temperature and are stable;

[0193] (3) EIS test program setting: set the test frequency to 100 kHz-50 MHz; voltage protection range -10V-10V; disturbance voltage setting is 5mV.

[0194] V. Rate and cycle test process and program setting

[0195] (1) Battery test preparation: give the soft package battery a restraint force of 20Mpa with a self-made steel clamp;

[0196] (2) Test environment preparation: adjust the constant temperature oven to 25°C;

[0197] (3) Balance the battery temperature: connect the test line of the blue electric test cabinet into the oven, put the measured battery into the oven, connect the blue electric test cabinet, and start testing after the oven and battery temperatures completely reach the test temperature and are stable;

[0198] (4) Rate test procedure setting: set the test voltage upper and lower limit to 2.5V-4.2V. After the capacity calibration of the soft package battery is completed, according to the current value corresponding to the calibrated capacity, set the battery to complete a cycle of charging and discharging process under the program of 0.2C charging / 1C discharging, and record the overpotential data of the battery under 1C discharging condition.

[0199] (5) Cycle test procedure setting: set the test voltage upper and lower limit to 2.5V-4.2V. After the capacity calibration of the soft package battery is completed, according to the current value corresponding to the calibrated capacity, set the battery to complete a cycle of charging and discharging process under the program of 0.2C charging / 1C discharging, and record the overpotential data of the battery under 1C discharging condition.

[0200] The specific test results are shown in Table 2:

[0201] Table 2

[0202] Comparing Examples 1-14 and Comparative Example 1, it can be seen that the structure of the present disclosure can effectively improve the ionic conductivity of the positive electrode sheet, reduce polarization, and thus improve the rate and cycle performance of the battery; the ionic conductivity of the four sides of the positive electrode sheet is slightly higher than that of the middle part, which can effectively avoid the problem of poor cycle performance of the battery caused by uneven lithium ion transmission rate due to thermal diffusion during the charging and discharging process of the battery.

[0203] Comparing Examples 1-14 and Comparative Example 2, it can be seen that when the conductivity of the surrounding layer in the active layer is greater than that of the middle layer, the ionic conductivity of the positive electrode sheet can be effectively improved, and the setting of the conductivity of different positions in the active layer is the key to improving the ionic conductivity of the positive electrode sheet, reducing polarization, and improving the rate and cycle performance of the battery.

[0204] As can be seen from Examples 1-3, the type of electrolyte has an important influence on the performance of the battery. The polymer electrolyte has a slightly lower ionic conductivity of the positive electrode sheet due to its low ionic conductivity, but its excellent processability and flowability reduce the interface impedance between the positive electrode sheet and the electrolyte, and improve the cycle performance of the battery.

[0205] As can be seen from Examples 3-5 and Examples 6-8, the design structure of the positive electrode sheet (the first structure or the second structure) has little effect on the performance of the sheet and the battery; the area ratio of the surrounding layer and the first conductivity active layer has a greater effect on the performance of the sheet and the battery, and too low or too high a ratio will cause the cycle performance of the sheet to decrease.

[0206] As can be seen from the comparison of Example 3 and Example 9-10 and Example 6 and Example 11-12, the loading (i.e. the active layer thickness) of the positive electrode sheet has a significant impact on the rate and cycle performance of the battery. If the loading is too low, the energy density of the battery is small, which is not suitable for mass production. If the loading is too high, the migration of lithium ions from the surface of the positive electrode to the interior of the sheet increases significantly, resulting in increased polarization and increased capacity decay of the battery.

[0207] As can be seen from the comparison of Example 1 and Example 13, the use of a composite electrolyte containing a polymer electrolyte for the surround layer can effectively fill the gaps between the first and second conductivity active layers, thereby improving the cycle performance of the battery.

[0208] As can be seen from the comparison of Example 1 and Example 14, the design of the gradient conductivity on the surface of the current collector can effectively optimize the overall ion transport path of the sheet.

[0209] Although the embodiments of the present disclosure have been shown and described above, it will be understood by those skilled in the art that the above embodiments are exemplary and should not be construed as limiting the present disclosure, and those skilled in the art can make changes, modifications, replacements and variations to the above embodiments within the scope of the present disclosure.

Claims

1. A positive electrode sheet, wherein, The positive electrode plate comprises: a current collector (100) and a composite active layer provided on at least one surface of the current collector (100), the composite active layer comprising an intermediate layer and a surrounding layer (400) provided around the intermediate layer, the electrical conductivity of the surrounding layer (400) being greater than that of the intermediate layer.

2. The cathode sheet of claim 1, wherein, The electrical conductivity of the intermediate layer away from the current collector (100) is less than that of the intermediate layer close to the current collector (100), and the electrical conductivity of the surrounding layer (400) is greater than that of the intermediate layer close to the current collector (100).

3. The cathode sheet of claim 1 or 2, wherein, The intermediate layer comprises: a first electrical conductivity active layer (200) provided on one surface of the current collector (100); and a second electrical conductivity active layer (300) provided on the surface of the first electrical conductivity active layer (200) away from the current collector (100); The surrounding layer (400) is provided at least around the periphery of the second electrical conductivity active layer (300), and the surrounding layer (400) is in contact with the second electrical conductivity active layer (300); The electrical conductivity of the first electrical conductivity active layer (200) is greater than that of the second electrical conductivity active layer (300).

4. The cathode sheet of claim 3, wherein, The surrounding layer (400) is provided on the surface of the first electrical conductivity active layer (200) away from the current collector (100).

5. The cathode sheet of claim 3 or 4, wherein, The thickness of the surrounding layer (400) is the same as that of the second electrical conductivity active layer (300).

6. The cathode sheet of claim 3 or 4, wherein, The orthographic projection of the second electrical conductivity active layer (300) on the current collector (100) overlaps with that of the first electrical conductivity active layer (200) on the current collector (100), the surrounding layer (400) is further provided around the periphery of the first electrical conductivity active layer (200), and the surrounding layer (400) is in contact with the first electrical conductivity active layer (200).

7. The cathode sheet of claim 6, wherein, The thickness of the surrounding layer (400) is the same as the sum of the thicknesses of the first electrical conductivity active layer (200) and the second electrical conductivity active layer (300).

8. The cathode sheet of any one of claims 3-7, wherein, The thickness of the surrounding layer (400) is 100 μm to 450 μm; And / or, the thickness of the second electrical conductivity active layer (300) is 100 μm to 250 μm; And / or, the thickness of the first electrical conductivity active layer (200) is 100 μm to 200 μm.

9. The cathode electrode according to any one of claims 3 to 8, wherein The thickness of the positive electrode plate is 206 μm to 465 μm.

10. The cathode sheet of any one of claims 3-9, wherein, The area ratio of the surrounding layer (400) to the first electrical conductivity active layer (200) is (10-40):100; Or, the area ratio of the surrounding layer (400) to the first electrical conductivity active layer (200) is (10-40):(90-60), preferably (10-20):(90-80).

11. The cathode sheet of any one of claims 3-9, wherein, The area ratio of the surrounding layer (400) to the first electrical conductivity active layer (200) is (15-25):

100.

12. The cathode sheet of any one of claims 3-11, wherein, The first electrical conductivity active layer (200) comprises a first active material, a first conductive agent, a first binder, and a first solid-state electrolyte; And / or, the second conductivity active layer (300) comprises a second active material, a second conductive agent, a second binder and a second solid-state electrolyte; And / or, the surrounding layer (400) comprises a third active material, a third conductive agent, a third binder and a third solid-state electrolyte.

13. The cathode sheet of claim 12, wherein, The third solid-state electrolyte has a greater conductivity than the first solid-state electrolyte, and the first solid-state electrolyte has a greater conductivity than the second solid-state electrolyte.

14. The cathode sheet of claim 12 or 13, wherein, The mass ratio of the first active material, the first conductive agent, the first binder and the first solid-state electrolyte is (60-90):(1-10):(0-3):(0-30); And / or, the mass ratio of the second active material, the second conductive agent, the second binder and the second solid-state electrolyte is (60-90):(1-10):(0-3):(0-30); And / or, the mass ratio of the third active material, the third conductive agent, the third binder and the third solid-state electrolyte is (60-90):(1-10):(0-3):(0-30).

15. The cathode sheet of any one of claims 12-14, wherein, The first solid-state electrolyte, the second solid-state electrolyte and the third solid-state electrolyte each independently comprise at least one of an oxide solid-state electrolyte, a sulfide solid-state electrolyte, a halide solid-state electrolyte and a polymer solid-state electrolyte, and at least one of the following conditions is met: D50 of the oxide solid electrolyte, the sulfide solid electrolyte, and the halide solid electrolyte particles 50 0.5 μm to 50 μm, respectively; The weight percentage of the polymer solid-state electrolyte in the third solid-state electrolyte is 10% to 100%.

16. A solid state battery, wherein, The positive electrode plate comprises the positive electrode plate according to any one of claims 1 to 15.

17. An electrical device, comprising: The solid-state battery comprises the positive electrode plate according to claim 16. The solid-state battery comprises the positive electrode plate according to claim 16.

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