Composite positive electrode sheet, preparation method therefor, all-solid-state battery, and electrical device

Abstract

The present invention relates to a composite positive electrode sheet, a preparation method therefor, an all-solid-state battery, and an electrical device. The composite positive electrode sheet comprises a positive electrode current collector and a positive electrode active material layer. In the positive electrode active material layer, in a direction away from the positive electrode current collector, the content of additive-coated positive electrode active material shows an increasing trend, the content of uncoated positive electrode active material shows a decreasing trend, the content of additive-coated sulfide electrolyte shows a decreasing trend, and the content of uncoated sulfide electrolyte shows an increasing trend. The additive comprises a lithium salt containing the element fluorine and / or the element boron.

Description

Composite cathode sheet, preparation method thereof, all-solid-state battery and electric device

[0001] Priority information

[0002] The present disclosure claims priority to the patent application with the patent application number 202411377998.7 and the title “Composite cathode sheet, preparation method thereof, all-solid-state battery and electric device” filed on September 29, 2024 with the State Intellectual Property Office of China, the content of which is incorporated herein by reference in its entirety. TECHNICAL FIELD

[0003] The present disclosure relates to the field of batteries, in particular, to a composite cathode sheet, a preparation method thereof, an all-solid-state battery and an electric device. BACKGROUND

[0004] Nowadays, solid-state batteries equipped with solid-state electrolyte have excellent safety and the possibility of achieving high energy density, which is more in line with the needs of future development in the field of electric vehicles and large-scale energy storage. Current all-solid-state batteries can be mainly divided into polymer-based all-solid-state batteries, organic-inorganic composite all-solid-state batteries and sulfide-based all-solid-state batteries. Among them, sulfide-based all-solid-state batteries have attracted widespread attention in the industry due to their high room temperature ionic conductivity and good mechanical properties.

[0005] However, there are still many major challenges in the large-scale application of current sulfide-based all-solid-state batteries. Among them, the composite cathode material layer composed of the positive active material, sulfide electrolyte and conductive agent on the positive electrode side is a decisive factor affecting the electrochemical performance of sulfide solid-state batteries. However, the side reactions at the interface between the positive active material and the sulfide solid-state electrolyte, the space charge layer effect and many other problems result in unsatisfactory rate performance and cycle performance of sulfide-based all-solid-state batteries.

[0006] Therefore, the current composite cathode sheet, preparation method thereof, all-solid-state battery and electric device still need to be improved. SUMMARY

[0007] The present disclosure aims to at least partially alleviate or solve at least one of the above-mentioned problems.

[0008] In an aspect of the present disclosure, a composite cathode tab is provided. In some embodiments of the present disclosure, the composite cathode tab comprises a cathode current collector and a cathode active material layer on at least one surface of the cathode current collector; the cathode active material layer comprises additive-coated cathode active material, uncoated cathode active material, additive-coated sulfide electrolyte and uncoated sulfide electrolyte; in the cathode active material layer, the content of additive-coated cathode active material shows a trend of increase, the content of uncoated cathode active material shows a trend of decrease, the content of additive-coated sulfide electrolyte shows a trend of decrease, and the content of uncoated sulfide electrolyte shows a trend of increase in the direction away from the cathode current collector; and the additive comprises lithium salt containing fluorine element and / or boron element. Thus, during the charging and discharging of the all-solid-state battery, the composite cathode tab can directly form a uniform interface stabilization layer in situ at the cathode active material / sulfide electrolyte interface in the composite cathode and the interface between the entire cathode tab and the electrolyte layer, so as to inhibit the interface side reaction between the cathode and the electrolyte under high pressure, thereby improving the electrochemical performance of the battery.

[0009] In another aspect of the present disclosure, a method for preparing a composite cathode tab is provided. In some embodiments of the present disclosure, the method for preparing a composite cathode tab comprises: providing a cathode current collector; and forming a cathode active material layer on at least one surface of the cathode current collector, wherein the cathode active material layer comprises additive-coated cathode active material, uncoated cathode active material, additive-coated sulfide electrolyte and uncoated sulfide electrolyte; in the cathode active material layer, the content of additive-coated cathode active material shows a trend of increase, the content of uncoated cathode active material shows a trend of decrease, the content of additive-coated sulfide electrolyte shows a trend of decrease, and the content of uncoated sulfide electrolyte shows a trend of increase in the direction away from the cathode current collector; and the additive comprises lithium salt containing fluorine element and / or boron element. Thus, during the charging and discharging of the all-solid-state battery, the composite cathode tab prepared by the method can directly form a uniform interface stabilization layer in situ at the cathode active material / sulfide electrolyte interface in the composite cathode and the interface between the entire cathode tab and the electrolyte layer, so as to inhibit the interface side reaction between the cathode and the electrolyte under high pressure, thereby improving the electrochemical performance of the battery.

[0010] In yet another aspect of the present disclosure, an all-solid-state battery is provided. In some embodiments of the present disclosure, the all-solid-state battery comprises a cathode, a solid electrolyte layer and an anode, and the cathode comprises the composite cathode tab as described above or prepared by the method as described above. Thus, the battery has all the features and advantages of the composite cathode tab as described above, which will not be repeated here.

[0011] In yet another aspect of the present disclosure, a power consuming device is provided. In some embodiments of the present disclosure, the power consuming device comprises the all-solid-state battery as described above. Thus, the power consuming device has all the features and advantages of the all-solid-state battery as described above, which will not be repeated here. BRIEF DESCRIPTION OF DRAWINGS

[0012] The above and / or additional aspects and advantages of the present disclosure will become apparent and more readily appreciated from the following description of the embodiments, taken in conjunction with the accompanying drawings in which:

[0013] FIG. 1 shows a structural schematic diagram of a composite positive electrode tab according to one embodiment of the present disclosure;

[0014] FIG. 2 shows a structural schematic diagram of a composite positive electrode tab according to another embodiment of the present disclosure;

[0015] FIG. 3 shows a structural schematic diagram of a composite positive electrode tab according to yet another embodiment of the present disclosure;

[0016] FIG. 4 shows a structural schematic diagram of a composite positive electrode tab according to yet another embodiment of the present disclosure;

[0017] FIG. 5 shows a structural schematic diagram of different particle contacts in a positive electrode tab;

[0018] FIG. 6 shows a structural schematic diagram of a positive electrode tab and a solid-state electrolyte layer in the related art;

[0019] FIG. 7 shows a structural schematic diagram of a composite positive electrode tab and a solid-state electrolyte layer according to one embodiment of the present disclosure.

[0020] REFERENCE SIGNS: 100: composite positive electrode tab; 110: positive electrode current collector; 120: positive electrode active material layer; 121: first sub-layer; 122: second sub-layer; 123: third sub-layer; 200: solid-state electrolyte layer; 10: positive electrode active material; 20: sulfide electrolyte; 30: first coating layer; 40: second coating layer; 50: interface side reaction substance layer; 11: first positive electrode active material; 12: first sulfide electrolyte; 13: third coating layer; 14: second positive electrode active material; 15: fourth coating layer; 16: second sulfide electrolyte. DETAILED DESCRIPTION

[0021] Embodiments of the present disclosure are described in detail below with reference to the attached drawings, which are presented as examples and do not limit the present disclosure. The embodiments described below are examples and are not intended to limit the present disclosure.

[0022] The present disclosure is made based on the findings and recognitions of the inventors on the following facts and problems:

[0023] For the problems existing in the all-solid-state battery, the surface coating method of the positive electrode material can be used to improve the electrochemical performance of the battery. At present, the commonly used coating material system of the positive electrode material mainly uses oxygen-based inorganic compounds with low electronic conductivity and certain ionic conductivity, but such coating layer still cannot well meet the current needs in terms of ionic conductivity, electrochemical stability window, and cost, etc. In addition, coating low electronic conductivity material on the surface of the positive electrode active material will also affect the electron transport in the composite positive electrode. In addition, the side reaction between the positive electrode and the sulfide electrolyte also occurs at the interface between the entire composite positive electrode tab and the sulfide electrolyte layer. However, due to the thermal stability of the tab itself, the traditional positive electrode material coating method cannot be directly applied to the tab; although the gas phase reaction method can realize uniform coating of the entire tab interface, it is high in cost and is not conducive to large-scale commercial application.

[0024] The inventors of the present disclosure coat the positive electrode active material and the sulfide electrolyte with additives, and design the content variation rules of the additive-coated positive electrode active material, the additive-coated sulfide electrolyte, the uncoated positive electrode active material, and the uncoated sulfide electrolyte. During the charging process of the battery, the additive can decompose at high pressure, so that a uniform (B and / or F enriched) interface stabilization layer is formed in situ at the positive electrode active material / sulfide electrolyte interface in the composite positive electrode and the interface between the entire positive electrode tab and the electrolyte layer during the charging process of the all-solid-state battery, to inhibit the interface side reaction between the positive electrode and the electrolyte under high pressure, while sufficient electron transport paths still exist in the composite positive electrode, thereby improving the electrochemical performance of the battery.

[0025] In view of this, in one aspect of the present disclosure, the present disclosure provides a composite positive electrode tab. In some embodiments of the present disclosure, referring to FIGS. 1-4, the composite positive electrode tab 100 can include a positive electrode current collector 110 and a positive electrode active material layer 120, and the positive electrode active material layer 120 is located on at least one surface of the positive electrode current collector 110.

[0026] In some embodiments of the present disclosure, the positive electrode active material layer 120 can include an additive-coated positive electrode active material, an uncoated positive electrode active material, an additive-coated sulfide electrolyte, and an uncoated sulfide electrolyte; in the positive electrode active material layer 120, along the direction away from the positive electrode current collector 110, the content of the additive-coated positive electrode active material shows a trend of increasing, the content of the uncoated positive electrode active material shows a trend of decreasing, the content of the additive-coated sulfide electrolyte shows a trend of decreasing, and the content of the uncoated sulfide electrolyte shows a trend of increasing; wherein the additive can include a lithium salt containing fluorine element and / or boron element. Thus, by designing the content variation of the substances in the positive electrode active material layer, during the charging process of the battery, the additive can decompose at high pressure, so that a uniform (B and / or F enriched) interfacial stabilization layer is formed in situ at the positive electrode active material / sulfide electrolyte interface inside the composite positive electrode and the interface between the entire positive electrode tab and the electrolyte layer during the charging process of the full solid-state battery, to inhibit the interfacial side reaction between the positive electrode and the electrolyte at high pressure, while sufficient electron transport paths can still exist inside the composite positive electrode, thereby improving the electrochemical performance of the battery.

[0027] It should be noted that the "content" in the present disclosure refers to the mass content.

[0028] It should also be noted that "shows a trend of increasing" and "shows a trend of decreasing" in the present disclosure can include a variety of different cases. The following will be described taking "shows a trend of increasing" as an example, and "shows a trend of decreasing" can be understood in a similar manner.

[0029] In some embodiments, "shows a trend of increasing" can mean that the content of a certain component can gradually increase along the direction away from the positive electrode current collector.

[0030] In another embodiment, "shows a trend of increasing" can mean that the content of a certain component can increase in a gradient along the direction away from the positive electrode current collector, for example, the positive electrode active material layer can include a plurality of sub-layers, and the content of a certain component in any one sub-layer is greater than the content of the component in a sub-layer closer to the positive electrode current collector.

[0031] In yet another embodiment, "shows a trend of increasing" can mean that the content of a certain component can remain unchanged within a certain thickness range along the direction away from the positive electrode current collector, for example, the positive electrode active material layer can include at least three sub-layers, and the content of a certain component in two adjacent sub-layers can be the same.

[0032] In some embodiments of the present disclosure, the additive can include at least one of lithium bis(oxalato)borate (LiBOB), lithium bis(fluorooxalato)borate (LiDFOB), lithium difluorophosphate (LiPO2F2), lithium bis(fluorosulfonyl)imide (LiFSI), lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), and lithium bis(monofluoromalonato)borate (LiBFMB). The additive described above can decompose to generate a stable interface layer with certain ionic conductivity and low electronic conductivity under high temperature, high pressure, or current, which is conducive to inhibiting the interface side reaction between the positive active material and the sulfide electrolyte interface in the composite positive electrode and between the positive electrode sheet and the sulfide electrolyte layer under high pressure conditions, thereby facilitating the improvement of the electrochemical performance of the all-solid-state battery.

[0033] In some embodiments of the present disclosure, the additive can be LiBOB, LiDFOB, LiPO2F2, LiFSI, LiTFSI, or LiBFMB. In other embodiments of the present disclosure, the additive can include two or more of LiBOB, LiDFOB, LiPO2F2, LiFSI, LiTFSI, and LiBFMB.

[0034] In some embodiments of the present disclosure, the additive for coating the sulfide electrolyte can be the same as the additive for coating the positive active material. In other embodiments of the present disclosure, the additive for coating the sulfide electrolyte can be different from the additive for coating the positive active material.

[0035] It should be noted that "coating" in the present disclosure can refer to full coating or partial coating. Taking the positive active material coated with the additive as an example, the positive active material particles can be fully coated with the additive, or only a part of the positive active material particles can be covered with the additive.

[0036] In some embodiments of the present disclosure, the thickness of the additive coating layer in the positive active material coated with the additive can be 1 nm to 20 nm, for example, the thickness of the coating layer can be 1 nm, 3 nm, 5 nm, 7 nm, 10 nm, 12 nm, 15 nm, 20 nm, etc. The thickness of the coating layer in the above range is more conducive to forming a uniform interface stable layer between the positive active material coated with the additive and the sulfide electrolyte without coating, thereby inhibiting the side reaction under high pressure conditions, and further improving the electrochemical performance of the all-solid-state battery.

[0037] In some embodiments of the present disclosure, in the additive-coated sulfide electrolyte, the thickness of the additive coating layer can be 1 nm-20 nm, for example, the thickness of the coating layer can be 1 nm, 2 nm, 4 nm, 8 nm, 10 nm, 13 nm, 16 nm, 20 nm, etc. Thus, it is more conducive to form a uniform interfacial stabilization layer between the uncoated positive electrode active material and the additive-coated sulfide electrolyte, inhibit side reactions under high pressure, and thus more conducive to improve the electrochemical performance of the all-solid-state battery.

[0038] In some embodiments of the present disclosure, in the additive-coated positive electrode active material, the mass of the additive can be 0.1%-10% of the mass of the positive electrode active material before coating, for example, the mass of the additive can be 0.1%, 0.5%, 0.8%, 1%, 4%, 6%, 8%, 10% of the mass of the positive electrode active material before coating, etc. Thus, the above-mentioned amount of additive can form a relatively thin coating layer on the surface of the positive electrode active material, and in the charging and discharging process, the additive can decompose to form a component with certain ion conductivity but poor electronic conductivity, thereby facilitating the inhibition of side reactions between the positive electrode active material and the electrolyte.

[0039] In some embodiments of the present disclosure, in the additive-coated sulfide electrolyte, the mass of the additive can be 0.1%-10% of the mass of the sulfide electrolyte before coating, for example, the mass of the additive can be 0.1%, 0.3%, 0.6%, 0.9%, 2%, 5%, 7%, 10% of the mass of the sulfide electrolyte before coating, etc. Thus, the above-mentioned amount of additive can form a relatively thin coating layer on the surface of the sulfide electrolyte, and in the isostatic pressing process of the solid-state battery preparation, the relatively thin coating layer will not affect the elastic modulus of the sulfide, facilitating the effective results between the sulfide solid-state electrolyte and the positive electrode active material; at the same time, in the charging and discharging process, the additive can decompose to form a component with good ion conductivity but poor electronic conductivity, thereby better inhibiting the side reactions between the electrolyte and the positive electrode active material.

[0040] In some embodiments of the present disclosure, referring to FIGS. 1 and 3, the positive electrode current collector 110 is provided with a positive electrode active material layer 120 on one surface thereof. In some other embodiments of the present disclosure, referring to FIGS. 2 and 4, the positive electrode current collector 110 is provided with a positive electrode active material layer 120 on both surfaces thereof.

[0041] In some embodiments of the present disclosure, referring to FIGS. 1 and 2, the positive electrode active material layer 120 can include a first sub-layer 121 and a second sub-layer 122, wherein the first sub-layer 121 is located between the positive electrode current collector 110 and the second sub-layer 122; in the first sub-layer 121, the positive electrode active material is the first positive electrode active material without coating, and the sulfide electrolyte is the first sulfide electrolyte with additive coating; in the second sub-layer 122, the positive electrode active material is the second positive electrode active material with additive coating, and the sulfide electrolyte is the second sulfide electrolyte without coating. Thus, at the interfaces where the positive electrode active materials and the sulfide electrolytes in the first sub-layer and the second sub-layer contact, and at the contact interface between the first sub-layer and the second sub-layer, a uniform and stable interface layer is formed in situ by the additive, the interfacial side reaction between the positive electrode active material and the electrolyte in the composite positive electrode is inhibited, and thus the electrochemical performance of the battery is improved.

[0042] The reasons why the composite positive electrode sheet of the present disclosure can improve the electrochemical performance of the all-solid-state battery are described in detail below in combination with the accompanying drawings.

[0043] FIG. 5(a) illustrates a case where the uncoated sulfide electrolyte 20 and the uncoated positive electrode active material 10 directly contact each other. In this case, the contact interface between the two has poor ion conduction performance but has certain electron conduction capacity. In the above case, an interfacial side reaction easily occurs, forming an interfacial side reaction substance layer 50, which deteriorates the performance of the battery. It is necessary to avoid this case as much as possible on the side of the positive electrode active material layer close to the positive electrode current collector or on the side far from the positive electrode current collector.

[0044] FIG. 5(b) illustrates a case where the uncoated sulfide electrolyte 20 and the positive electrode active material 10 with additive coating directly contact each other. The additive forms a first coating layer 30 on the surface of the positive electrode active material 10. In this case, the interface between the positive electrode active material 10 and the sulfide electrolyte 20 has certain ion conduction capacity but poor electron conduction performance. On the side of the positive electrode active material layer far from the positive electrode current collector, there can be more positive electrode active materials with coating and uncoated sulfide electrolytes directly contacting each other, which can avoid the occurrence of side reactions.

[0045] FIG. 5(c) illustrates a case where the sulfide electrolyte 20 with additive coating and the uncoated positive electrode active material 10 directly contact each other. The additive forms a second coating layer 40 on the surface of the sulfide electrolyte 20. In this case, the interface also has certain ion conduction capacity but poor electron conduction performance. On the side of the positive electrode active material layer close to the positive electrode current collector, there can be more uncoated positive electrode active materials and coated sulfide electrolytes directly contacting each other, which can avoid the occurrence of side reactions.

[0046] On the side of the positive electrode active material layer close to the positive electrode current collector, there can also be a case where the uncoated positive electrode active material particles are in contact with each other, in which case, the positive electrode active material particles can provide sufficient electron transport paths, increasing the electrochemical activity of the battery. On the side of the positive electrode active material layer away from the positive electrode current collector, the presence of more coated positive electrode active material particles helps to alleviate side reactions on the contact interface between the composite positive electrode layer and the solid-state electrolyte layer, increasing the electrochemical activity of the battery.

[0047] In some embodiments of the present disclosure, referring to FIGS. 3 and 4, the positive electrode active material layer 120 further includes at least one third sub-layer 123, the third sub-layer 123 being located between the first sub-layer 121 and the second sub-layer 122; the third sub-layer 123 includes the additive-coated third positive electrode active material, the uncoated fourth positive electrode active material, the additive-coated third sulfide electrolyte, and the uncoated fourth sulfide electrolyte.

[0048] In some embodiments of the present disclosure, the positive electrode active material layer 120 includes the first sub-layer 121, the third sub-layer 123, and the second sub-layer 122, in the third sub-layer 123, the mass content of the additive-coated positive electrode active material, the uncoated positive electrode active material, the additive-coated sulfide electrolyte, and the uncoated sulfide electrolyte can be 45%, 45%, 5%, and 5%, respectively, based on the total mass of the positive electrode active materials (including coated and uncoated) and the sulfide electrolytes (including coated and uncoated).

[0049] It should be noted that the first positive electrode active material, the second positive electrode active material, the third positive electrode active material, and the fourth positive electrode active material can be the same or different; the first sulfide electrolyte, the second sulfide electrolyte, the third sulfide electrolyte, and the fourth sulfide electrolyte can be the same or different; the additives forming the various coating layers can be the same or different.

[0050] In some embodiments of the present disclosure, the positive electrode active material layer 120 can include the first sub-layer 121, the second sub-layer 122, and at least two third sub-layers 123, the closer to the second sub-layer 122, the higher the mass content of the additive-coated positive electrode active material, the lower the mass content of the uncoated positive electrode active material, the lower the mass content of the additive-coated sulfide electrolyte, and the higher the mass content of the uncoated sulfide electrolyte.

[0051] Through the above component content change design, the electronic transmission in the positive active material can be better ensured, and the side reaction at the interface where the positive active material and the sulfide electrolyte contact and the interface between the positive active material layer and the electrolyte layer can be better avoided. In the charging and discharging process, the additive can be decomposed into a component with poor electronic conductivity but good ionic conductivity, thereby helping to improve the electrochemical performance of the battery.

[0052] In some embodiments, in the positive active material layer, the content of the additive-coated positive active material increases in the direction away from the positive current collector, the content of the uncoated positive active material decreases, the content of the additive-coated sulfide electrolyte decreases, and the content of the uncoated sulfide electrolyte increases.

[0053] In some related technologies, as shown in FIG. 6, the positive active material layer is located between the positive current collector 110 and the solid-state electrolyte layer 200, the sulfide electrolyte 20 (smaller particles) in the positive active material layer is uncoated, and the positive active material 10 (larger particles) is additive-coated, and the additive forms a first coating layer 30 on the surface of the positive active material 10. In this case, there are more coated positive active material particles directly contacting in the entire positive active material layer, which causes poor electronic conductivity in the positive active material layer and is not conducive to improving the electrochemical performance of the battery.

[0054] In some embodiments of the present disclosure, referring to FIG. 7, the positive active material layer is located between the positive current collector 110 and the solid-state electrolyte layer 200, and the positive active material layer includes a first sub-layer 121 and a second sub-layer 122. The first sub-layer 121 is close to the positive current collector 110, the first positive active material 11 (larger particles) in the layer is uncoated, and the first sulfide electrolyte 12 (smaller particles) is additive-coated, and the additive forms a third coating layer 13 on the surface of the first sulfide electrolyte 12. In this case, more positive active material particles directly contact, the electronic conductivity is good, and the coated sulfide electrolyte directly contacts the positive active material particles, the interface has poor ionic conductivity but good electronic conductivity, and is not prone to side reactions; the second sub-layer 122 is close to the solid-state electrolyte layer 200, the second positive active material 14 (larger particles) in the layer is additive-coated, and the additive forms a fourth coating layer 15 on the surface of the second positive active material 14, and the second sulfide electrolyte 16 (smaller particles) is uncoated. In this case, the coated positive active material is not prone to side reactions when contacting the uncoated sulfide electrolyte, and the second sub-layer 122 is not prone to side reactions with the solid-state electrolyte layer 200.

[0055] It should be noted that the additives forming the first coating layer 30 and the second coating layer 40 can be the same or different; the additives forming the third coating layer 13 and the fourth coating layer 15 can be the same or different; the first positive electrode active material 11 and the second positive electrode active material 14 can be the same or different; and the first sulfide electrolyte 12 and the second sulfide electrolyte 16 can be the same or different.

[0056] The additive is a material with high ionic conductivity and low electronic conductivity. After the positive electrode active material is coated with the additive, if the coated positive electrode active material particles directly contact the coated positive electrode active material particles, the electronic conductivity in the composite positive electrode will be limited. Therefore, on the side close to the positive electrode current collector, the sulfide electrolyte is mainly coated to inhibit the side reaction between the positive electrode and the sulfide electrolyte while ensuring sufficient electronic transmission path inside the composite positive electrode. On the side away from the positive electrode current collector, i.e., the side close to the solid electrolyte layer (sulfide electrolyte layer), the positive electrode active material is mainly coated to achieve the formation of a stable interface when contacting the sulfide electrolyte layer.

[0057] In some embodiments of the present disclosure, in any two sub-layers of the positive electrode active material layer, the thickness of the sub-layer away from the positive electrode current collector is ≤ the thickness of the sub-layer close to the positive electrode current collector. In this way, it is more conducive to ensuring that the composite positive electrode has sufficient electronic transmission path inside.

[0058] In some embodiments, the positive electrode active material layer 120 is composed of a first sub-layer 121 and a second sub-layer 122, and the thickness of the second sub-layer 122 can be less than the thickness of the first sub-layer 121. In other embodiments, the positive electrode active material layer 120 is composed of a first sub-layer 121 and a second sub-layer 122, and the thickness of the second sub-layer 122 can be equal to the thickness of the first sub-layer 121.

[0059] In some embodiments, the positive electrode active material layer is composed of at least two sub-layers, and the thickness of each sub-layer decreases in the direction away from the positive electrode current collector.

[0060] In some embodiments of the present disclosure, the mass content of the positive electrode active material can be 75%-89.5% based on the total mass of the positive electrode active material layer, for example, the mass content of the positive electrode active material can be 75%, 80%, 82%, 85%, 87%, 89.5%, etc. The presence of a large amount of positive electrode active material in the positive electrode active material layer can ensure that the positive electrode has a high capacity.

[0061] In some embodiments of the present disclosure, the positive electrode active material can be a ternary positive electrode material. In some embodiments, the positive electrode active material can include NCM811 (ternary material LiNi 0.8 Co 0.1Mn 0.1 O2), Ni88 ternary cathode material (LiNi 0.88 Co x Mn 0.12-x O2, 0 < x < 0.12), Ni90 ternary cathode material (LiNi 0.9 Co y Mn 0.1-y O2, 0 < y < 0.1). In some embodiments of the present disclosure, the cathode active material can be NCM811, Ni88 ternary cathode material, or Ni90 ternary cathode material, or the like high-voltage cathode material. In some other embodiments of the present disclosure, the cathode active material can include at least two of NCM811, Ni88 ternary cathode material, and Ni90 ternary cathode material. It should be noted that these cathode materials can be undoped or doped modified, and the surface thereof can have or not have a conductive coating layer.

[0062] In some embodiments of the present disclosure, the sulfide electrolyte can include at least one of glass ceramic Li-P-S system electrolyte (e.g., 75Li2S·5P2S3·20P2S5), argyrodite Li6PS5X (X can be halogen such as Cl, Br, I, etc., and can be Li 5.5 PS 4.5 Cl 1.5 ) system electrolyte, lithium germanium phosphorus sulfide Li 10 GeP2S 12 (LGPS) system electrolyte. Adding the sulfide electrolyte in the cathode active material layer can optimize the ion transport channel, improve the lithium ion conductivity, and reduce the internal resistance of the battery, thereby being conducive to improving the charge and discharge performance of the battery; the above-mentioned sulfide electrolyte can also form a relatively stable interface with the cathode active material, reduce the interface side reaction, and thereby improve the cycle stability of the battery.

[0063] In some embodiments of the present disclosure, the cathode current collector can include an aluminum foil. In some embodiments of the present disclosure, the cathode current collector can be a carbon-coated aluminum foil.

[0064] In some embodiments of the present disclosure, the cathode active material layer can further include a binder and a conductive agent.

[0065] In some embodiments of the present disclosure, the binder in the cathode active material layer can include at least one of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), styrene butadiene rubber (SBR), nitrile rubber (NBR, e.g., hydrogenated nitrile rubber HNBR), polyacrylate, polyacrylic acid (PAA), alkyl cellulose, and polyethylene oxide (PEO).

[0066] In some embodiments of the present disclosure, the mass content of the binder can be 0.48%-2%, for example, the mass content of the binder can be 0.48%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1%, 1.5%, 2%, etc., based on the total mass of the positive electrode active material layer. In this way, the binder in the above content can play a good binding role, can bind various particles in the positive electrode active material layer, and firmly bind the positive electrode active material layer on the positive electrode current collector, thereby facilitating the improvement of the stability of the positive electrode sheet.

[0067] In some embodiments of the present disclosure, the conductive agent of the positive electrode active material layer can include at least one of carbon black (for example, acetylene black, Super P, etc.), carbon nanotubes, and graphene. The addition of the above conductive agent is conducive to improving the conductivity of the positive electrode active material layer, thereby facilitating the further improvement of the electrochemical performance of the battery.

[0068] In some embodiments of the present disclosure, the mass content of the conductive agent can be 0.48%-2%, for example, the mass content of the conductive agent can be 0.48%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1%, 1.5%, 2%, etc., based on the total mass of the positive electrode active material layer. In this way, it is conducive to improving the conductivity of the positive electrode, thereby facilitating the improvement of the electrochemical performance of the battery.

[0069] In some embodiments of the present disclosure, the positive electrode active material layer can include a positive electrode active material (including additive-coated and uncoated) with a mass content of 75%-89.5%, a binder with a mass content of 0.48%-2%, a conductive agent with a mass content of 0.48%-2%, and a sulfide electrolyte (including additive-coated and uncoated) in the remainder.

[0070] In the present disclosure, the contact state of the coated and uncoated materials does not need to be specially controlled, and the components in the sheet can be detected by means such as XPS, SEM, etc.

[0071] In another aspect of the present disclosure, the present disclosure proposes a method for preparing a composite positive electrode sheet. In some embodiments of the present disclosure, the method for preparing a composite positive electrode sheet can include the following steps:

[0072] S100: providing a positive electrode current collector.

[0073] In some embodiments of the present disclosure, the positive electrode current collector can include an aluminum foil. In some specific embodiments of the present disclosure, the positive electrode current collector can be a carbon-coated aluminum foil.

[0074] S200: forming a positive electrode active material layer on at least one surface of the positive electrode current collector.

[0075] In embodiments of the present disclosure, the positive electrode active material layer comprises additive-coated positive electrode active material, uncoated positive electrode active material, additive-coated sulfide electrolyte, and uncoated sulfide electrolyte; in the positive electrode active material layer, the content of the additive-coated positive electrode active material shows a trend of increasing, the content of the uncoated positive electrode active material shows a trend of decreasing, the content of the additive-coated sulfide electrolyte shows a trend of decreasing, and the content of the uncoated sulfide electrolyte shows a trend of increasing in the direction away from the positive electrode current collector; and the additive comprises a lithium salt containing fluorine element and / or boron element.

[0076] By means of the design of component content variation, more uncoated positive electrode active material particles directly contact on the side close to the positive electrode current collector, which can provide sufficient electron transmission path, and the interface between the uncoated positive electrode active material and the coated sulfide electrolyte has certain ion conductivity but poor electronic conductivity, which can better avoid the generation of side reactions; on the side away from the positive electrode current collector, the interface between the coated positive electrode active material and the uncoated sulfide electrolyte has certain ion conductivity but poor electronic conductivity, which can also better avoid the generation of side reactions. In the process of charging, the full-solid-state battery forms a uniform interface stabilization layer in situ at the positive electrode active material / sulfide electrolyte interface in the composite positive electrode sheet and the interface between the entire positive electrode sheet and the electrolyte layer to inhibit the interface side reactions between the positive electrode and the electrolyte under high pressure conditions, while sufficient electron transmission path can still exist in the composite positive electrode, thereby improving the electrochemical performance of the battery.

[0077] In some embodiments of the present disclosure, the mass content of the positive electrode active material can be 75%-89.5% based on the total mass of the positive electrode active material layer.

[0078] In some embodiments of the present disclosure, forming the positive electrode active material layer on at least one surface of the positive electrode current collector can comprise the following steps:

[0079] S210: coating the first sulfide electrolyte with an additive to obtain additive-coated first sulfide electrolyte, uniformly mixing the additive-coated first sulfide electrolyte, uncoated first positive electrode active material, first conductive agent, and first binder to obtain a first mixture, placing the first mixture on the surface of the positive electrode current collector, and pressing into a sheet to obtain a first sub-layer.

[0080] In some embodiments of the present disclosure, in the step of coating the first sulfide electrolyte with an additive, the mass of the additive can be 0.1%-10% of the mass of the first sulfide electrolyte before coating, for example, the mass of the additive can be 0.1%, 0.5%, 1%, 5%, 7%, 10%, etc. of the mass of the first sulfide electrolyte before coating. Thus, it is beneficial to form a relatively thin coating layer on the surface of the sulfide electrolyte.

[0081] In some embodiments of the present disclosure, the method of coating the first sulfide electrolyte with the additive can include: mixing the additive and the first sulfide electrolyte uniformly, ball-milling and / or mechanically fusing the mixture using a ball mill and / or a mechanical fusing machine, and coating the additive on the surface of the first sulfide electrolyte. In this way, the additive can be built on the surface of the sulfide electrolyte particles, and the material is subjected to both extrusion force and shear force during the mixing process, so that the additive is thinly and uniformly coated on the surface of the sulfide electrolyte material particles.

[0082] In some embodiments of the present disclosure, the process of coating the first sulfide electrolyte can be carried out in an inert atmosphere.

[0083] In some embodiments of the present disclosure, the additive and the first sulfide electrolyte can be ball-milled using a ball mill to coat the additive on the surface of the first sulfide electrolyte. In some specific embodiments of the present disclosure, when the ball mill is used for coating, the rotation speed can be 1000 rpm-10000 rpm, thereby facilitating the formation of a thin and uniform coating layer of the additive on the surface of the sulfide electrolyte, and the material is less likely to be decomposed during the mixing process.

[0084] In some embodiments of the present disclosure, the additive and the first sulfide electrolyte can be mechanically fused using a mechanical fusing machine, and the mechanical fusing machine can also be used for mixing to form a thin and uniform coating layer on the surface of the first sulfide electrolyte.

[0085] In some embodiments of the present disclosure, the additive can include at least one of lithium bis(oxalato)borate, lithium bis(difluoro oxalato)borate, lithium difluorophosphate, lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethanesulfonyl)imide, and lithium bis(monofluoromalonato)borate.

[0086] In some embodiments of the present disclosure, the positive active material can include a ternary positive electrode material, for example, the positive active material can include at least one of NCM811 (LiNi 0.8 Co 0.1 Mn 0.1 O2), Ni88 ternary positive electrode material (LiNi 0.88 Co x Mn 0.12-x O2, 0 0.9 Co y Mn 0.1-y O2, 0

[0087] In some embodiments of the present disclosure, the sulfide electrolyte can include at least one of a Li-P-S system electrolyte, a argyrodite system electrolyte, and a lithium germanium phosphorus sulfide system electrolyte.

[0088] As to the first conductive agent and the first binder in the first sub-layer, reference can be made to the materials of the conductive agent and the binder in the positive electrode active material layer mentioned above, which will not be repeated here.

[0089] S220: coating the second positive electrode active material with the additive to obtain an additive-coated second positive electrode active material, mixing the additive-coated second positive electrode active material, the uncoated second sulfide electrolyte, a second conductive agent, and a second binder uniformly to obtain a second mixture, and placing the second mixture on the side of the first sub-layer away from the positive electrode current collector and pressing into a sheet to obtain a second sub-layer.

[0090] In some embodiments of the present disclosure, in the step of coating the second positive electrode active material with the additive, the mass of the additive can be 0.1%-10% of the mass of the second positive electrode active material before coating, for example, the mass of the additive can be 0.1%, 0.5%, 1%, 5%, 7%, 10%, etc. of the mass of the second positive electrode active material before coating. In this way, it is beneficial to form a relatively thin coating layer on the surface of the positive electrode active material.

[0091] In some embodiments of the present disclosure, the method of coating the second positive electrode active material with the additive can include: mixing the additive and the second positive electrode active material uniformly, and using a ball mill and / or a mechanical fusion machine to ball mill and / or mechanically fuse the mixture to coat the additive on the surface of the positive electrode active material. In this way, the additive can be built on the surface of the particles of the positive electrode active material, and during the mixing process, the material is subjected to both extrusion force and shear force, so that the additive is thinly and uniformly coated on the surface of the particles of the positive electrode active material.

[0092] In some embodiments of the present disclosure, the process of coating the second positive electrode active material can be carried out in an inert atmosphere.

[0093] In some embodiments of the present disclosure, a ball mill or a mechanical fusion machine can be used to coat the second positive electrode active material. In some embodiments of the present disclosure, when a ball mill is used for coating, the rotation speed can be 1000 rpm-10000 rpm. In this way, it is beneficial to form a thin and uniform additive coating layer on the surface of the positive electrode active material, and the material is not easy to decompose during the process, so that good chemical stability can be maintained.

[0094] In some embodiments of the present disclosure, forming the second sub-layer can further comprise the step of forming at least one third sub-layer before forming the second sub-layer. Forming the third sub-layer can comprise the steps of:

[0095] The third positive active material is coated with the additive to obtain an additive-coated third positive active material. The method and parameters for coating the third positive active material can refer to the method and parameters for coating the second positive active material, which will not be repeated here.

[0096] The third sulfide electrolyte is coated with the additive to obtain an additive-coated third sulfide electrolyte. The method and parameters for coating the third sulfide can refer to the method and parameters for coating the first sulfide electrolyte, which will not be repeated here.

[0097] In some embodiments of the present disclosure, the additive-coated third positive active material and the additive-coated third sulfide electrolyte in the third sub-layer can also be obtained by using a ball mill and / or a mechanical fusion machine to process the mixture of the additive and the third positive active material, the mixture of the additive and the fourth sulfide electrolyte.

[0098] The additive-coated third positive active material, the uncoated fourth positive active material, the additive-coated third sulfide electrolyte, the uncoated fourth sulfide electrolyte, the third conductive agent, and the third binder are mixed uniformly to obtain a third mixture. The third mixture is placed on the side of the first sub-layer away from the positive current collector, and is pressed into a sheet to obtain a third sub-layer.

[0099] In some embodiments of the present disclosure, before forming the second sub-layer, a third sub-layer can be formed on the side of the first sub-layer away from the positive current collector. In some other embodiments of the present disclosure, before forming the second sub-layer, at least two third sub-layers can be formed on the side of the first sub-layer away from the positive current collector. Regardless of the number of third sub-layers, the following conditions must be met: in the positive active material layer, in the direction away from the positive current collector, the content of the additive-coated positive active material shows an increasing trend, the content of the uncoated positive active material shows a decreasing trend, the content of the additive-coated sulfide electrolyte shows a decreasing trend, and the content of the uncoated sulfide electrolyte shows an increasing trend.

[0100] In some embodiments of the present disclosure, before the second sub-layer is formed, at least one third sub-layer can be formed on the side of the first sub-layer away from the positive current collector, and in the positive active material layer, the content of the additive-coated positive active material increases in the direction away from the positive current collector, the content of the uncoated positive active material decreases, the content of the additive-coated sulfide electrolyte decreases, and the content of the uncoated sulfide electrolyte increases.

[0101] As for the second conductive agent and the second binder of the second sub-layer, the third conductive agent and the third binder of the third sub-layer, the materials of the conductive agent and the binder mentioned above in the positive active material layer can be referred to, and will not be repeated here.

[0102] It should be noted that the additives of each coating layer can be the same or different; the first conductive agent, the second conductive agent, the third conductive agent can be the same or different; the first binder, the second binder, the third binder can be the same or different; the first positive active material, the second positive active material, the third positive active material, the fourth positive active material can be the same or different; the first sulfide electrolyte, the second sulfide electrolyte, the third sulfide electrolyte, the fourth sulfide electrolyte can be the same or different.

[0103] As for the thickness relationship of each sub-layer, it has been described above and will not be repeated here.

[0104] In another aspect of the present disclosure, the present disclosure provides a full solid-state battery. In some embodiments of the present disclosure, the full solid-state battery comprises a positive electrode, a solid-state electrolyte layer and a negative electrode, and the solid-state electrolyte layer is located between the positive electrode and the negative electrode, wherein the positive electrode comprises the composite positive electrode sheet described above or is prepared by the method described above. Therefore, the battery is less likely to produce side reactions during charging and discharging, and has good electrochemical performance.

[0105] In some embodiments of the present disclosure, the material of the solid-state electrolyte layer can comprise at least one of an oxide electrolyte, a sulfide electrolyte and a polymer electrolyte.

[0106] In some embodiments of the present disclosure, the oxide electrolyte can comprise at least one of LATP, LLZO, LLTO and the like. In some embodiments of the present disclosure, the sulfide electrolyte can comprise a glass-ceramic Li-P-S system electrolyte (for example, 75Li2S·5P2S3·20P2S5), a sulfide Li 5.5 PS 4.5 Cl 1.5 ) system electrolyte, a lithium germanium phosphorus sulfide Li 10 GeP2S12 In some embodiments of the present disclosure, the polymer electrolyte can include at least one of PEO, PVDF, PAN.

[0107] In some embodiments of the present disclosure, the particle size of the solid-state electrolyte in the solid-state electrolyte layer can be 1 nm-5 μm. In some specific embodiments, micron-sized solid-state electrolyte materials can be used.

[0108] In some embodiments of the present disclosure, the negative electrode active material used by the negative electrode can be various lithium-embeddable and -extractable negative electrode active materials commonly used by those skilled in the art, for example, can be selected from one or more of carbon materials, tin alloys, silicon alloys, silicon, tin, germanium, and can also use lithium metal, lithium-indium alloy, etc. Among them, the carbon material can use one or more of non-graphitized carbon, graphite, or carbon obtained by high-temperature oxidation of polyacetylene-based polymer materials or pyrolytic carbon, coke, organic polymer sintered material, activated carbon.

[0109] In some embodiments of the present disclosure, after assembling the positive electrode, the solid-state electrolyte, and the negative electrode to obtain the all-solid-state battery, three cycles of pre-cycling can be performed, preferably high-temperature (30-60°C) small rate (0.01-0.1C) cycling, so that the additive is oxidized and decomposed at the positive electrode / sulfide interface, thereby forming a uniform interface stabilization layer in situ to inhibit the interface side reaction between the positive electrode and the sulfide electrolyte under high pressure, thereby improving the electrochemical performance of the battery.

[0110] In another aspect of the present disclosure, the present disclosure provides a power-using device. In some embodiments of the present disclosure, the power-using device can include the all-solid-state battery described above. Therefore, the power-using device has all the features and advantages of the all-solid-state battery described above, which will not be repeated here.

[0111] In some embodiments of the present disclosure, the power-using device can be a vehicle (for example, an electric bicycle, an electric vehicle, a hybrid vehicle, etc.), a portable electronic device (for example, a smart phone, a notebook computer, a tablet computer, etc.), a robot, an energy storage system, etc.

[0112] In summary, the composite cathode tab design scheme of the all-solid-state battery proposed in the present disclosure, through the design of component content variation, makes the all-solid-state battery in-situ form a uniform interface stabilization layer at the interface between the cathode active material / sulfide electrolyte in the composite cathode and the interface between the entire cathode tab and the electrolyte layer during the charging process, which can not only inhibit the interface side reaction between the cathode and the electrolyte under high pressure conditions, but also ensure the existence of sufficient electron transmission path in the composite cathode. Therefore, the electrochemical performance of the all-solid-state battery assembled by the above composite cathode tab is significantly improved. The composite cathode design scheme of the all-solid-state battery proposed in the present disclosure does not require expensive / complex preparation process / method, is simple and economical, and has wide application range.

[0113] The present disclosure will be described below through specific examples, and those skilled in the art can understand that the specific examples below are only for illustrative purposes, and do not limit the scope of the present disclosure in any way. In addition, in the following examples, unless otherwise specified, the materials and equipment used are commercially available. If the specific processing conditions and processing methods are not explicitly described in the following examples, the conditions and methods known in the art can be used for processing.

[0114] Example 1

[0115] 90 parts by mass of LiNi 0.88 Co 0.08 Mn 0.04 O2, 10 parts by mass of LiDFOB-coated LPSC (Li 5.5 PS 4.5 Cl 1.5 ), 0.5 parts by mass of HNBR, 0.5 parts by mass of SBR, and 0.5 parts by mass of Super P were used as the materials of the composite cathode I, 90 parts by mass of LiDFOB-coated LiNi 0.88 Co 0.08 Mn 0.04 O2, 10 parts by mass of uncoated LPSC (Li 5.5 PS 4.5 Cl 1.5 ), 0.5 parts by mass of HNBR, 0.5 parts by mass of SBR, and 0.5 parts by mass of Super P were used as the materials of the composite cathode II, and LPSC (Li 5.5 PS 4.5 Cl 1.5 ) was used to prepare a solid electrolyte layer, Li / In was used as the negative electrode to assemble a mold battery, and the battery performance was tested.

[0116] The manufacturing process is: ①the material of the composite positive electrode I and the material of the composite positive electrode II are mixed uniformly; a certain amount of composite positive electrode I powder is placed in the tablet press mold, and a tablet is pressed on the surface of the positive electrode current collector by cold pressing technology, then a certain amount of composite positive electrode II powder is placed in the tablet press mold, and the composite positive electrode II powder is pressed on the surface of the composite positive electrode I tablet to obtain a double-layer composite positive electrode tablet; ②prepare the LPSC solid-state electrolyte; ③assemble the mold battery with Li / In negative electrode.

[0117] In Example 1, the amount of LiDFOB coating in the LiDFOB-coated LPSC is 1% (the mass of LiDFOB is 1% of the mass of LPSC before coating), the amount of LiDFOB coating in the LiDFOB-coated LiNi 0.88 Co 0.08 Mn 0.04 O2 is 1% (the mass of LiDFOB is 1% of the mass of LiNi 0.88 Co 0.08 Mn 0.04 O2 before coating); the thickness of the composite positive electrode I is 6.75 μm, the thickness of the composite positive electrode II is 0.75 μm, and the thickness ratio of the composite positive electrode I to the composite positive electrode II is 9:1.

[0118] Example 2

[0119] Use 90 parts by mass of LiNi 0.88 Co 0.08 Mn 0.04 O2, 10 parts by mass of LiDFOB-coated LPSC (Li 5.5 PS 4.5 Cl 1.5 ), 0.5 parts by mass of HNBR, 0.5 parts by mass of SBR, and 0.5 parts by mass of Super P as the material of the composite positive electrode I, and use 90 parts by mass of LiDFOB-coated LiNi 0.88 Co 0.08 Mn 0.04 O2, 10 parts by mass of LiDFOB-coated LPSC (Li 5.5 PS 4.5 Cl 1.5 ), 0.5 parts by mass of HNBR, 0.5 parts by mass of SBR, and 0.5 parts by mass of Super P as the material of the composite positive electrode II, to prepare the composite positive electrode; use LPSC (Li 5.5 PS 4.5 Cl 1.5 ) to prepare the solid-state electrolyte layer, and Li / In as the negative electrode to assemble the mold battery, and test the battery performance.

[0120] The manufacturing process is: ①the material of the composite positive electrode I and the material of the composite positive electrode II are mixed uniformly; a certain amount of composite positive electrode I powder is placed in the tablet press mold, and a tablet is pressed on the surface of the positive electrode current collector by cold pressing technology, then a certain amount of composite positive electrode II powder is placed in the tablet press mold, and the composite positive electrode II powder is pressed on the surface of the composite positive electrode I tablet to obtain a double-layer composite positive electrode tablet; ②prepare the LPSC solid-state electrolyte; ③assemble the mold battery with Li / In negative electrode.

[0121] In Example 2, the amount of LiDFOB coating in the LiDFOB-coated LPSC is 3% (the mass of LiDFOB is 3% of the mass of LPSC before coating), the amount of LiDFOB coating in the LiDFOB-coated LiNi 0.88 Co 0.08 Mn 0.04 O2 is 3% (the mass of LiDFOB is 3% of the mass of LiNi 0.88 Co 0.08 Mn 0.04 O2 before coating); the thickness of the composite positive electrode I is 6.75 μm, the thickness of the composite positive electrode II is 0.75 μm, and the thickness ratio of the composite positive electrode I to the composite positive electrode II is 9:1.

[0122] Example 3

[0123] Use 90 parts by mass of LiNi 0.88 Co 0.08 Mn 0.04 O2, 10 parts by mass of LiDFOB-coated LPSC (Li 5.5 PS 4.5 Cl 1.5 ), 0.5 parts by mass of HNBR, 0.5 parts by mass of SBR, and 0.5 parts by mass of Super P as the material of the composite positive electrode I, and use 90 parts by mass of LiDFOB-coated LiNi 0.88 Co 0.08 Mn 0.04 O2, 10 parts by mass of LiDFOB-coated LPSC (Li 5.5 PS 4.5 Cl 1.5 ), 0.5 parts by mass of HNBR, 0.5 parts by mass of SBR, and 0.5 parts by mass of Super P as the material of the composite positive electrode II, to prepare the composite positive electrode; use LPSC (Li 5.5 PS 4.5 Cl 1.5 ) to prepare the solid-state electrolyte layer, and Li / In as the negative electrode to assemble the mold battery, and test the battery performance.

[0124] The manufacturing process is: ①the material of the composite positive electrode I and the material of the composite positive electrode II are mixed uniformly; a certain amount of composite positive electrode I powder is placed in the tablet press mold, and a tablet is pressed on the surface of the positive electrode current collector by cold pressing technology, then a certain amount of composite positive electrode II powder is placed in the tablet press mold, and the composite positive electrode II powder is pressed on the surface of the composite positive electrode I tablet to obtain a double-layer composite positive electrode tablet; ②prepare the LPSC solid-state electrolyte; ③assemble the mold battery with Li / In negative electrode.

[0125] In Example 3, the amount of LiDFOB coating in the LiDFOB-coated LPSC is 5% (the mass of LiDFOB is 5% of the mass of LPSC before coating), the amount of LiDFOB coating in the LiDFOB-coated LiNi 0.88 Co 0.08 Mn 0.04 O2 is 5% (the mass of LiDFOB is 5% of the mass of LiNi 0.88 Co 0.08 Mn 0.04 O2 before coating); the thickness of the composite positive electrode I is 6.75 μm, the thickness of the composite positive electrode II is 0.75 μm, and the thickness ratio of the composite positive electrode I to the composite positive electrode II is 9:1.

[0126] Example 4

[0127] Use 90 parts by mass of LiNi 0.88 Co 0.08 Mn 0.04 O2, 10 parts by mass of LiDFOB-coated LPSC (Li 5.5 PS 4.5 Cl 1.5 ), 0.5 parts by mass of HNBR, 0.5 parts by mass of SBR, and 0.5 parts by mass of Super P as the material of the composite positive electrode I, and use 90 parts by mass of LiDFOB-coated LiNi 0.88 Co 0.08 Mn 0.04 O2, 10 parts by mass of LiDFOB-coated LPSC (Li 5.5 PS 4.5 Cl 1.5 ), 0.5 parts by mass of HNBR, 0.5 parts by mass of SBR, and 0.5 parts by mass of Super P as the material of the composite positive electrode II, to prepare the composite positive electrode; use LPSC (Li 5.5 PS 4.5 Cl 1.5 ) to prepare the solid-state electrolyte layer, and Li / In as the negative electrode to assemble the mold battery, and test the battery performance.

[0128] The manufacturing process is: ①the material of the composite positive electrode I and the material of the composite positive electrode II are mixed uniformly; a certain amount of composite positive electrode I powder is placed in the tablet press mold, and a tablet is pressed on the surface of the positive electrode current collector by cold pressing technology, then a certain amount of composite positive electrode II powder is placed in the tablet press mold, and the composite positive electrode II powder is pressed on the surface of the composite positive electrode I tablet to obtain a double-layer composite positive electrode tablet; ②prepare the LPSC solid-state electrolyte; ③assemble the mold battery with Li / In negative electrode.

[0129] In Example 4, the amount of LiDFOB coating in the LiDFOB-coated LPSC is 10% (the mass of LiDFOB is 10% of the mass of LPSC before coating), the amount of LiDFOB coating in the LiDFOB-coated LiNi 0.88 Co 0.08 Mn 0.04 O2 is 10% (the mass of LiDFOB is 10% of the mass of LiNi 0.88 Co 0.08 Mn 0.04 O2 before coating); the thickness of the composite positive electrode I is 6.75 μm, the thickness of the composite positive electrode II is 0.75 μm, and the thickness ratio of the composite positive electrode I to the composite positive electrode II is 9:1.

[0130] Example 5

[0131] Use 90 parts by mass of LiNi 0.88 Co 0.08 Mn 0.04 O2, 10 parts by mass of LiDFOB-coated LPSC (Li 5.5 PS 4.5 Cl 1.5 ), 0.5 parts by mass of HNBR, 0.5 parts by mass of SBR, and 0.5 parts by mass of Super P as the material of the composite positive electrode I, and use 90 parts by mass of LiDFOB-coated LiNi 0.88 Co 0.08 Mn 0.04 O2, 10 parts by mass of LiDFOB-coated LPSC (Li 5.5 PS 4.5 Cl 1.5 ), 0.5 parts by mass of HNBR, 0.5 parts by mass of SBR, and 0.5 parts by mass of Super P as the material of the composite positive electrode II, to prepare the composite positive electrode; use LPSC (Li 5.5 PS 4.5 Cl 1.5 ) to prepare the solid-state electrolyte layer, and Li / In as the negative electrode to assemble the mold battery, and test the battery performance.

[0132] The manufacturing process is: ①the material of the composite positive electrode I and the material of the composite positive electrode II are mixed uniformly; a certain amount of composite positive electrode I powder is placed in the tablet press mold, and a tablet is pressed on the surface of the positive electrode current collector by cold pressing technology, then a certain amount of composite positive electrode II powder is placed in the tablet press mold, and the composite positive electrode II powder is pressed on the surface of the composite positive electrode I tablet to obtain a double-layer composite positive electrode tablet; ②prepare the LPSC solid-state electrolyte; ③assemble the mold battery with Li / In negative electrode.

[0133] In Example 5, the LiDFOB coating amount in the LiDFOB-coated LPSC is 0.5% (the mass of LiDFOB is 0.5% of the mass of LPSC before coating), the LiDFOB-coated LiNi 0.88 Co 0.08 Mn 0.04 O2, the LiDFOB coating amount in the LiDFOB-coated LiNi 0.88 Co 0.08 Mn 0.04 O2 is 0.5% (the mass of LiDFOB is 0.5% of the mass of LiNi

[0134] Example 6

[0135] Use 90 parts by mass of LiNi 0.88 Co 0.08 Mn 0.04 O2, 10 parts by mass of LiDFOB-coated LPSC (Li 5.5 PS 4.5 Cl 1.5 ), 0.5 parts by mass of HNBR, 0.5 parts by mass of SBR, and 0.5 parts by mass of Super P as the material of the composite positive electrode I, and use 90 parts by mass of LiDFOB-coated LiNi 0.88 Co 0.08 Mn 0.04 O2, 10 parts by mass of LiDFOB-coated LPSC (Li 5.5 PS 4.5 Cl 1.5 ), 0.5 parts by mass of HNBR, 0.5 parts by mass of SBR, and 0.5 parts by mass of Super P as the material of the composite positive electrode II to prepare the composite positive electrode; use LPSC (Li 5.5 PS 4.5 Cl 1.5 ) to prepare the solid-state electrolyte layer, and Li / In as the negative electrode to assemble the mold battery, and test the battery performance.

[0136] The manufacturing process is: ①the material of the composite positive electrode I and the material of the composite positive electrode II are respectively fully mixed and uniformly mixed; a certain amount of composite positive electrode I powder is placed in a tablet press mold, and a tablet is pressed on the surface of the positive electrode current collector by using cold pressing technology, then a certain amount of composite positive electrode II powder is placed in the tablet press mold, and the composite positive electrode II powder is pressed on the surface of the composite positive electrode I tablet to obtain a double-layer composite positive electrode tablet; ②prepare the LPSC solid-state electrolyte; ③assemble the mold battery with Li / In negative electrode.

[0137] The coating amount of LiDFOB in Example 6 is the same as that in Example 1, both of which are 1%, the thickness of the composite positive electrode I is 5.25 μm, the thickness of the composite positive electrode II is 2.25 μm, and the thickness ratio of the composite positive electrode I to the composite positive electrode II is 7:3.

[0138] Example 7

[0139] Use 90 parts by mass of LiNi 0.88 Co 0.08 Mn 0.04 O2, 10 parts by mass of LiDFOB-coated LPSC (Li 5.5 PS 4.5 Cl 1.5 ), 0.5 parts by mass of HNBR, 0.5 parts by mass of SBR, and 0.5 parts by mass of Super P as the material of the composite positive electrode I, and use 90 parts by mass of LiDFOB-coated LiNi 0.88 Co 0.08 Mn 0.04 O2, 10 parts by mass of LiDFOB-coated LPSC (Li 5.5 PS 4.5 Cl 1.5 ), 0.5 parts by mass of HNBR, 0.5 parts by mass of SBR, and 0.5 parts by mass of Super P as the material of the composite positive electrode II, to prepare the composite positive electrode; use LPSC (Li 5.5 PS 4.5 Cl 1.5 ) to prepare the solid-state electrolyte layer, and assemble the mold battery with Li / In as the negative electrode to test the battery performance.

[0140] The manufacturing process is: ①the material of the composite positive electrode I and the material of the composite positive electrode II are respectively fully mixed and uniformly mixed; a certain amount of composite positive electrode I powder is placed in a tablet press mold, and a tablet is pressed on the surface of the positive electrode current collector by using cold pressing technology, then a certain amount of composite positive electrode II powder is placed in the tablet press mold, and the composite positive electrode II powder is pressed on the surface of the composite positive electrode I tablet to obtain a double-layer composite positive electrode tablet; ②prepare the LPSC solid-state electrolyte; ③assemble the mold battery with Li / In negative electrode.

[0141] The coating amount of LiDFOB in Example 7 is the same as that in Example 1, both of which are 1%, the thickness of the composite cathode I is 3.75 μm, the thickness of the composite cathode II is 3.75 μm, and the thickness ratio of the composite cathode I to the composite cathode II is 5:5.

[0142] Example 8

[0143] 90 parts by mass of LiNi 0.88 Co 0.08 Mn 0.04 O2, 10 parts by mass of LiDFOB-coated LPSC (Li 5.5 PS 4.5 Cl 1.5 ), 0.5 parts by mass of HNBR, 0.5 parts by mass of SBR, and 0.5 parts by mass of Super P were used as the materials of the composite cathode I, 45 parts by mass of LiNi 0.88 Co 0.08 Mn 0.04 O2, 45 parts by mass of LiDFOB-coated LiNi 0.88 Co 0.08 Mn 0.04 O2, 5 parts by mass of LiDFOB-coated LPSC (Li 5.5 PS 4.5 Cl 1.5 ), 5 parts by mass of LPSC (Li 5.5 PS 4.5 Cl 1.5 ), 0.5 parts by mass of HNBR, 0.5 parts by mass of SBR, and 0.5 parts by mass of Super P were used as the materials of the composite cathode II, 90 parts by mass of LiDFOB-coated LiNi 0.88 Co 0.08 Mn 0.04 O2, 10 parts by mass of LPSC (Li 5.5 PS 4.5 Cl 1.5 ), 0.5 parts by mass of HNBR, 0.5 parts by mass of SBR, and 0.5 parts by mass of Super P were used as the materials of the composite cathode III, and a composite cathode was prepared; a solid electrolyte layer was prepared using LPSC (Li 5.5 PS 4.5 Cl 1.5 ), and a Li / In negative electrode was used to assemble a mold battery, and the battery performance was tested.

[0144] The manufacturing process is: ①the material of composite positive electrode I, composite positive electrode II and composite positive electrode III are mixed respectively; a certain amount of composite positive electrode I powder is placed in the tablet mold, and the cold pressing technology is used to press the tablet on the surface of the positive electrode current collector, then a certain amount of composite positive electrode II powder is placed in the tablet mold, and the composite positive electrode II powder is pressed on the surface of the composite positive electrode I tablet, finally a certain amount of composite positive electrode III powder is placed in the tablet mold, and the composite positive electrode III powder is pressed on the surface of the composite positive electrode II tablet, so as to obtain a three-layer composite positive electrode tablet; ②prepare LPSC solid-state electrolyte; ③match Li / In negative electrode to assemble mold battery.

[0145] The coating amount of LiDFOB in example 8 is the same as that in example 1, both of which are 1%, the thickness of composite positive electrode I is 5.25 μm, the thickness of composite positive electrode II is 1.5 μm, and the thickness of composite positive electrode III is 0.75 μm, and the thickness ratio of composite positive electrode I, composite positive electrode II and composite positive electrode III is 7:2:1.

[0146] Example 9

[0147] Use 90 parts by mass of LiNi 0.88 Co 0.08 Mn 0.04 O2, 10 parts by mass of LiDFOB coated LPSC (Li 5.5 PS 4.5 Cl 1.5 ), 0.5 parts by mass of HNBR, 0.5 parts by mass of SBR and 0.5 parts by mass of Super P as the material of composite positive electrode I, use 60 parts by mass of LiNi 0.88 Co 0.08 Mn 0.04 O2, 30 parts by mass of LiDFOB coated LiNi 0.88 Co 0.08 Mn 0.04 O2, 6.67 parts by mass of LiDFOB coated LPSC (Li 5.5 PS 4.5 Cl 1.5 ), 3.33 parts by mass of LPSC (Li 5.5 PS 4.5 Cl 1.5 ), 0.5 parts by mass of HNBR, 0.5 parts by mass of SBR and 0.5 parts by mass of Super P as the material of composite positive electrode II, use 30 parts by mass of LiNi 0.88 Co 0.08 Mn 0.04 O2, 60 parts by mass of LiDFOB coated LiNi 0.88 Co 0.08 Mn 0.04O2, 6.67 parts by mass of LiDFOB-coated LPSC (Li 5.5 PS 4.5 Cl 1.5 ), 3.33 parts by mass of LPSC (Li 5.5 PS 4.5 Cl 1.5 ), 0.5 parts by mass of HNBR, 0.5 parts by mass of SBR, and 0.5 parts by mass of Super P as the material of the composite cathode III, using 90 parts by mass of LiDFOB-coated LiNi 0.88 Co 0.08 Mn 0.04 O2, 10 parts by mass of LPSC (Li 5.5 PS 4.5 Cl 1.5 ), 0.5 parts by mass of HNBR, 0.5 parts by mass of SBR, and 0.5 parts by mass of Super P as the material of the composite cathode IV, a composite cathode was prepared; using LPSC (Li 5.5 PS 4.5 Cl 1.5 ) to prepare a solid electrolyte layer, Li / In as the negative electrode to assemble a mold battery, and the battery performance was tested.

[0148] The manufacturing process is: ①the material of the composite cathode I, the material of the composite cathode II, the material of the composite cathode III, and the material of the composite cathode IV are mixed and uniformly mixed respectively; a certain amount of composite cathode I powder is placed in the tablet press mold, and a tablet is pressed on the surface of the positive electrode current collector by cold pressing technology, then a certain amount of composite cathode II powder is placed in the tablet press mold, and the composite cathode II powder is pressed on the surface of the composite cathode I tablet, then a certain amount of composite cathode III powder is placed in the tablet press mold, and the composite cathode III powder is pressed on the surface of the composite cathode II tablet, and finally a certain amount of composite cathode IV powder is placed in the tablet press mold, and the composite cathode IV powder is pressed on the surface of the composite cathode III tablet, to obtain a four-layer composite cathode tablet; ②prepare the LPSC solid electrolyte; ③match Li / In negative electrode to assemble a mold battery.

[0149] The coating amount of LiDFOB in Example 9 is the same as that in Example 1, both of which are 1%, the thickness of the composite cathode I is 3μm, the thickness of the composite cathode II is 2.25μm, the thickness of the composite cathode III is 1.5μm, and the thickness of the composite cathode IV is 0.75μm, and the thickness ratio of the composite cathode I, the composite cathode II, the composite cathode III, and the composite cathode IV is 4:3:2:1.

[0150] Comparative Example 1

[0151] Using 90 parts by mass of LiNi 0.88 Co0.08 Mn 0.04 O2, 10 parts by mass of uncoated LPSC (Li 5.5 PS 4.5 Cl 1.5 ), 0.5 parts by mass of HNBR, 0.5 parts by mass of SBR, and 0.5 parts by mass of Super P were mixed uniformly, and a composite positive electrode was prepared by pressing the mixture on the surface of a positive current collector using a cold pressing technique. A composite positive electrode was prepared using 90 parts by mass of LiNi 5.5 PS 4.5 Cl 1.5 ) to prepare a solid-state electrolyte layer, and a Li / In negative electrode was used to assemble a mold battery, and the performance of the battery was tested.

[0152] The manufacturing process is as follows: ① 90 parts by mass of LiNi 0.88 Co 0.08 Mn 0.04 O2, 10 parts by mass of uncoated LPSC (Li 5.5 PS 4.5 Cl 1.5 ), 0.5 parts by mass of HNBR, 0.5 parts by mass of SBR, and 0.5 parts by mass of Super P were mixed uniformly, and a composite positive electrode was prepared by pressing the mixture on the surface of a positive current collector using a cold pressing technique. A composite positive electrode was prepared using 90 parts by mass of LiNi 5.5 PS 4.5 Cl 1.5 ) to prepare a solid-state electrolyte; and ③ matching Li / In negative electrode to assemble a mold battery.

[0153] Battery performance test

[0154] The sulfide electrolyte was pre-pressed into a mold using a PEEK mold at a pressure of 150 MPa, and then an indium foil, a lithium-copper foil (lithium-copper composite tape) was assembled on one side of the electrolyte layer, and a composite positive electrode layer and a carbon-coated aluminum foil were assembled on the other side of the electrolyte layer. The cold pressing was performed using a tablet press at a forming pressure of 300 MPa, and the solid-state mold battery was obtained after tightening the bolts (this step was performed in an inert atmosphere). After three cycles of pre-cycling at 0.05C and 45°C (charge-discharge voltage was 2V-3.7V), the 0.1C-0.5C charge-discharge rate and the 0.33C cycle test were performed, and the test results were recorded in Table 1.

[0155] Rct (charge transfer resistance) test

[0156] The assembled battery was pre-cycled at 0.05C and 45°C (charge-discharge voltage was 2V-3.7V) for three cycles, and then charged at 0.1C (charged to 3.7V) to perform EIS test. The obtained EIS data was analyzed by relaxation time distribution (DRT) to obtain Rct, and the test results were recorded in Table 1.

[0157] Table 1

[0158] As can be seen from Table 1, compared with Comparative Example 1, the composite positive electrode sheet in Examples 1-9 of the present application using gradient design can significantly improve the performance of the all-solid-state battery. Compared with Example 6 and Example 7, the thickness of the sub-layer away from the positive current collector in Example 1 is thinner, the composite positive electrode has more sufficient electron transport path, and the performance of the battery is more excellent.

[0159] In the description of the present disclosure, the orientation or positional relationship indicated by the terms “upper”, “lower” and the like is based on the orientation or positional relationship shown in the drawings, and is only for the convenience of describing the present disclosure and does not require the present disclosure to be constructed and operated in a specific orientation, therefore cannot be understood as a limitation on the present disclosure.

[0160] In the description of the present disclosure, the description referring to the terms “one embodiment”, “another embodiment” and the like means that the specific features, structures, materials or characteristics described in conjunction with the embodiment are contained in at least one embodiment of the present disclosure. In the present specification, the illustrative description of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any appropriate manner in any one or more embodiments or examples. In addition, the person skilled in the art can combine and combine the different embodiments or examples described in the present specification and the features of the different embodiments or examples without contradiction. In addition, it should be noted that in the present specification, the terms “first”, “second” are only for the purpose of description, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of indicated technical features.

[0161] Although the embodiments of the present disclosure have been shown and described above, it can be understood that the above embodiments are exemplary and cannot be understood as a limitation on the present disclosure, and the person 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 composite cathode sheet, comprising a cathode current collector (110) and a cathode active material layer (120), the cathode active material layer (120) being located on at least one surface of the cathode current collector (110); the cathode active material layer (120) comprising an additive-coated cathode active material, an uncoated cathode active material (10), an additive-coated sulfide electrolyte and an uncoated sulfide electrolyte (20); in the cathode active material layer (120), along a direction away from the cathode current collector (110), a content of the additive-coated cathode active material presents a trend of increase, a content of the uncoated cathode active material (10) presents a trend of decrease, a content of the additive-coated sulfide electrolyte presents a trend of decrease, and a content of the uncoated sulfide electrolyte (20) presents a trend of increase; the additive comprises a lithium salt containing fluorine element and / or boron element.

2. The composite cathode electrode sheet according to claim 1, wherein in the additive-coated cathode active material, a mass of the additive is 0.1%-10% of a mass of the cathode active material before coating; and / or, in the additive-coated sulfide electrolyte, a mass of the additive is 0.1%-10% of a mass of the sulfide electrolyte before coating.

3. The composite cathode electrode sheet according to claim 1 or 2, wherein the cathode active material layer (120) comprises a first sub-layer (121) and a second sub-layer (122), the first sub-layer (121) being located between the cathode current collector (110) and the second sub-layer (122); in the first sub-layer (121), the cathode active material is an uncoated first cathode active material (11), and the sulfide electrolyte is an additive-coated first sulfide electrolyte (12); in the second sub-layer (122), the cathode active material is an additive-coated second cathode active material (14), and the sulfide electrolyte is an uncoated second sulfide electrolyte (16).

4. The composite cathode electrode sheet according to claim 3, wherein the cathode active material layer (120) further comprises at least one third sub-layer (123), the third sub-layer (123) being located between the first sub-layer (121) and the second sub-layer (122); in the third sub-layer (123), the cathode active material comprises an additive-coated third cathode active material and an uncoated fourth cathode active material, and the sulfide electrolyte comprises an additive-coated third sulfide electrolyte and an uncoated fourth sulfide electrolyte.

5. The composite cathode sheet of claim 3 or 4, wherein, in any two sub-layers of the cathode active material layer (120), a thickness of a sub-layer farther away from the cathode current collector (110) is ≤ a thickness of a sub-layer closer to the cathode current collector (110).

6. The composite cathode electrode sheet according to any one of claims 1-5, wherein, the additive comprises at least one of lithium bis(oxalato)borate, lithium difluoro(oxalato)borate, lithium difluorophosphate, lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethanesulfonyl)imide and lithium bis(monofluoromalonato)borate.

7. The composite cathode electrode sheet according to any one of claims 1-6, wherein, the cathode active material comprises a ternary cathode material; and / or, the sulfide electrolyte comprises at least one of a Li-P-S system electrolyte, a argyrodite system electrolyte and a lithium germanium phosphorus sulfur system electrolyte; and / or, the cathode current collector (110) comprises an aluminum foil.

8. The composite cathode electrode sheet according to any one of claims 1-7, wherein, The mass content of the positive electrode active material is 75% to 89.5% based on the total mass of the positive electrode active material layer (120).

9. The composite cathode electrode sheet according to any one of claims 1-8, wherein, The positive electrode active material layer (120) further comprises a binder and a conductive agent; the positive electrode active material layer (120) satisfies at least one of the following conditions: The binder comprises at least one of polyvinylidene fluoride, polytetrafluoroethylene, styrene butadiene rubber, nitrile butadiene rubber, polyacrylate, polyacrylic acid, alkyl cellulose and polyethylene oxide; The mass content of the binder is 0.48% to 2% based on the total mass of the positive electrode active material layer (120); The conductive agent comprises at least one of carbon black, carbon nanotube and graphene; The mass content of the conductive agent is 0.48% to 2% based on the total mass of the positive electrode active material layer (120).

10. A method for preparing a composite positive electrode sheet, comprising: providing a positive electrode current collector (110); forming a positive electrode active material layer (120) on at least one surface of the positive electrode current collector (110), wherein the positive electrode active material layer (120) comprises an additive-coated positive electrode active material, an uncoated positive electrode active material (10), an additive-coated sulfide electrolyte and an uncoated sulfide electrolyte (20); in the positive electrode active material layer (120), along the direction away from the positive electrode current collector (110), the content of the additive-coated positive electrode active material shows a trend of increase, the content of the uncoated positive electrode active material shows a trend of decrease, the content of the additive-coated sulfide electrolyte shows a trend of decrease, and the content of the uncoated sulfide electrolyte shows a trend of increase; the additive comprises a lithium salt containing fluorine element and / or boron element.

11. The method of claim 10, wherein, forming the positive electrode active material layer (120) on at least one surface of the positive electrode current collector (110) comprises: coating a first sulfide electrolyte with an additive to obtain an additive-coated first sulfide electrolyte (12), uniformly mixing the additive-coated first sulfide electrolyte, an uncoated first positive electrode active material (11), a first conductive agent and a first binder to obtain a first mixture, placing the first mixture on the surface of the positive electrode current collector (110) and pressing into a sheet to obtain a first sublayer (121); coating a second positive electrode active material with an additive to obtain an additive-coated second positive electrode active material (14), uniformly mixing the additive-coated second positive electrode active material (14), an uncoated second sulfide electrolyte (16), a second conductive agent and a second binder to obtain a second mixture, placing the second mixture on the side of the first sublayer (121) away from the positive electrode current collector (110) and pressing into a sheet to obtain a second sublayer (122).

12. The method of claim 11, wherein, In the step of coating the first sulfide electrolyte with an additive, the mass of the additive is 0.1% to 10% of the mass of the first sulfide electrolyte before coating; and / or, in the step of coating the second positive electrode active material with an additive, the mass of the additive is 0.1% to 10% of the mass of the second positive electrode active material before coating.

13. The method of claim 11 or 12, wherein, forming the positive active material layer (120) on at least one surface of the positive current collector (110) before forming the second sub-layer (122) further comprises a step of forming at least one third sub-layer (123), forming one of the third sub-layers (123) comprises: coating the third positive active material with the additive to obtain an additive-coated third positive active material; coating the third sulfide electrolyte with the additive to obtain an additive-coated third sulfide electrolyte; mixing the additive-coated third positive active material, the uncoated fourth positive active material, the additive-coated third sulfide electrolyte, the uncoated fourth sulfide electrolyte, the third conductive agent, and the third binder uniformly to obtain a third mixture, placing the third mixture on a side of the first sub-layer (121) away from the positive current collector (110), and pressing into a sheet to obtain the third sub-layer (123).

14. The method of any one of claims 11-13, wherein, In any two sub-layers of the positive active material layer (120), the thickness of the sub-layer away from the positive current collector (110) is ≤ the thickness of the sub-layer close to the positive current collector (110).

15. The method of any one of claims 11-14, employing a method of coating the first sulfide electrolyte with an additive comprising: mixing the additive and the first sulfide electrolyte uniformly, and ball-milling and / or mechanically fusing the mixture using a ball mill and / or a mechanical fusing machine to coat the additive on the surface of the first sulfide electrolyte; and / or, the method of coating the second positive active material with the additive comprises: mixing the additive and the second positive active material uniformly, and ball-milling and / or mechanically fusing the mixture using a ball mill and / or a mechanical fusing machine to coat the additive on the surface of the second positive active material.

16. The method of any one of claims 10-15, at least one of the following conditions is met: the additive comprises at least one of lithium bis-oxalato-borate, lithium bis-fluorooxalato-borate, lithium difluorophosphate, lithium bisfluorosulfonylimide, lithium bis-trifluoromethanesulfonylimide, and lithium bis(monofluoromalonato)borate; the positive active material comprises a ternary positive material; the sulfide electrolyte comprises at least one of a Li-P-S system electrolyte, a argyrodite system electrolyte, and a lithium-germanium-phosphorus-sulfur system electrolyte; the positive current collector (110) comprises an aluminum foil; the mass content of the positive active material is 75%-89.5% based on the total mass of the positive active material layer (120).

17. An all-solid-state battery, comprising a positive electrode, a solid electrolyte layer, and a negative electrode, the positive electrode comprising the composite positive electrode sheet (100) of any one of claims 1-9 or prepared by the method of any one of claims 10-16.

18. The all-solid battery according to claim 17, wherein the solid electrolyte layer comprises a sulfide solid electrolyte, the sulfide solid electrolyte comprising at least one of a Li-P-S system electrolyte, a argyrodite system electrolyte, and a lithium-germanium-phosphorus-sulfur system electrolyte.

19. An electrical device comprising the all-solid-state battery of claim 17 or 18.

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