lithium batteries

Abstract

This application discloses a lithium battery. The lithium battery of this application includes a positive electrode and a negative electrode current collector disposed opposite and spaced apart from the positive electrode. The positive electrode contains a composite positive electrode material, which includes a lithium-depleted phase as the positive electrode material and a lithium-rich phase for lithium replenishment. The lithium-rich phase and the lithium-depleted phase form a composite material. During charging and discharging, the lithium-rich phase migrates at least to the negative electrode current collector and forms a lithium-rich film layer on the surface of the negative electrode current collector. After charging, the composite positive electrode material of this application can release lithium ions. Some of the released lithium ions can irreversibly accumulate on the surface of the negative electrode current collector to form a lithium-rich film layer, so that the lithium-rich film layer and the negative electrode current collector form a negative electrode after the lithium battery is charged and discharged. Thus, the structure of the lithium battery of this application is effectively simplified, with low internal resistance, stable electrochemical performance such as cycle performance, and significantly reduced economic costs.

Description

Technical Field

[0001] This application belongs to the field of secondary battery technology, and particularly relates to a lithium battery. Background Technology

[0002] A rechargeable battery, also known as a secondary battery or accumulator, is a battery that can be recharged after discharge to reactivate its active materials and continue to be used. Rechargeable batteries are small and lightweight, meeting the growing demand for miniaturized electronic devices. With the rapid development of rechargeable battery technology, lithium-ion batteries, using lithium metal as the active material, are widely used in electric vehicles, power tools, portable consumer electronics, and energy storage due to their high energy density, long cycle life, high safety, and environmental friendliness, gradually becoming the mainstream rechargeable battery. Lithium metal, with its low redox potential (relative to the standard hydrogen electrode, -3.045V) and high gravimetric energy density (3860mAh / g), shows promise as a negative electrode material for high-capacity rechargeable batteries.

[0003] Among them, the positive electrode material or negative electrode material is one of the important factors affecting the electrochemical performance of lithium-ion batteries. For example, during the charging and discharging process, the lithium ions contained in the positive electrode material will gradually form a solid electrolyte interphase (SEI) film on the negative electrode, resulting in a decrease in the lithium ion content of the positive electrode, which in turn affects the first-cycle capacity and cycle life of the positive electrode material.

[0004] To address the issue of lithium consumption in the cathode material, current methods typically involve mixing the cathode material with a lithium replenishment additive to form a cathode active material layer. During the initial charging process, the lithium contained in the lithium replenishment additive is sacrificed, thereby ensuring the content of lithium ions that can be intercalated or deintercalated in the cathode material.

[0005] Another approach uses lithium foil as the negative electrode to provide lithium ions and replenish those consumed during the initial charge. However, lithium foil is elemental lithium metal, which is highly chemically reactive and prone to explosive reactions upon contact with water. It also oxidizes with atmospheric oxygen, forming oxides such as LiOH, Li₂O, and Li₂CO₃. This increases the complexity of battery assembly. Furthermore, the oxides formed after lithium foil oxidation are insulating materials; therefore, the oxidized lithium negative electrode surface reduces electrode conductivity and increases battery resistance. Additionally, current manufacturing processes make it difficult to achieve extremely low lithium foil thicknesses. Using lithium foil as both the negative electrode and the lithium replenishment source leads to two problems: firstly, a significant overconsumption of the lithium replenishment source increases costs; secondly, it increases battery weight and reduces energy density. Summary of the Invention

[0006] The purpose of this application is to provide a lithium battery that solves the technical problems of increased cost and process difficulty, and low energy density caused by the direct use of lithium foil as the negative electrode in existing lithium metal batteries.

[0007] To achieve the aforementioned objectives, a first aspect of this application provides a lithium battery. The lithium battery of this application includes a positive electrode sheet containing a positive active layer, and a negative current collector, which is disposed opposite to and spaced apart from the positive active layer. The positive electrode material contained in the positive active layer includes a composite positive electrode material, which includes a lithium-depleted phase serving as the positive electrode material and a lithium-rich phase for lithium replenishment. The lithium-rich phase and the lithium-depleted phase form a composite material, and during charging and discharging, the lithium-rich phase migrates at least towards the negative current collector and forms a lithium-rich film layer on the surface of the negative current collector.

[0008] In some embodiments, the lithium-rich film layer includes a lithium metal layer.

[0009] In some embodiments, the thickness of the lithium-rich film is 5 nm-100 μm.

[0010] In some embodiments, the composite cathode material accounts for 50%-99% of the mass content in the cathode active layer.

[0011] In some embodiments, the positive electrode active layer also includes a conductive agent and a binder.

[0012] In some embodiments, a separator is also included, which is stacked between the negative current collector and the positive active layer, and forms a cell with the negative current collector and the positive active layer. The cell is wetted with a first liquid electrolyte, and a lithium-rich film layer is formed on the surface of the negative current collector near the separator.

[0013] In some embodiments, a solid electrolyte layer is also included, which is stacked between the negative electrode current collector and the positive electrode active layer, and the lithium-rich film layer is formed on the surface of the negative electrode current collector near the solid electrolyte layer.

[0014] In a further embodiment, a second liquid electrolyte is also included, which wets the solid electrolyte layer, the negative electrode current collector, and the positive electrode active layer. The lithium-rich film layer is formed on the surface of the negative electrode current collector near the solid electrolyte layer.

[0015] In a further embodiment, the thickness of the solid electrolyte layer is 1μm-200μm.

[0016] In a further embodiment, the solid electrolyte in the solid electrolyte layer is at least one of polymer-based lithium salt electrolyte, oxide-based electrolyte, and sulfide-based electrolyte.

[0017] In some embodiments, the material of the negative electrode current collector includes one of the following: copper foil, carbon-coated copper foil, composite copper foil, copper mesh, copper foam, carbon paper, carbon cloth, etc.

[0018] In some embodiments, the thickness of the negative electrode current collector is 1–30 μm.

[0019] In some embodiments, the surface roughness of the negative electrode current collector is R. a The range is 0.5-20μm.

[0020] Compared with the prior art, this application has the following technical effects:

[0021] This application describes a lithium battery that incorporates a composite positive electrode material within its positive electrode sheet and uses a negative electrode current collector as the carrier for the negative electrode sheet. This design allows the composite positive electrode material to release lithium ions after charging and discharging. Some of these released lithium ions irreversibly accumulate on the surface of the negative electrode current collector, forming a lithium-rich film. This lithium-rich film and the negative electrode current collector then form the negative electrode sheet after the lithium battery is charged and discharged. In this way, the lithium battery of this application directly uses the negative electrode current collector during the assembly stage, avoiding the use of a negative electrode sheet, especially a lithium foil negative electrode. This effectively simplifies the structure, resulting in lower internal resistance, improved electrochemical performance stability such as cycle performance, and a significant reduction in economic costs. Attached Figure Description

[0022] To more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0023] Figure 1 This is a schematic diagram of the structure of Example A, in which the lithium-poor phase and lithium-rich phase contained in the composite cathode material of this application form a composite.

[0024] Figure 2 This is a schematic diagram of the structure of Example B, in which the lithium-poor phase and lithium-rich phase contained in the composite cathode material of this application form a composite.

[0025] Figure 3 This is a schematic diagram of the structure of the composite cathode material of this application, which contains lithium-poor phase and lithium-rich phase to form a composite embodiment C; wherein Figure A is a schematic diagram of the structure without a functional encapsulation layer, and Figure B is a schematic diagram of the structure with a functional encapsulation layer.

[0026] Figure 4 This is a schematic diagram of a non-solid-state lithium battery structure according to an embodiment of this application; wherein, Figure A is a schematic diagram of a non-solid-state battery structure without a negative electrode; Figure B is a schematic diagram of a battery structure with a negative electrode formed after charging and discharging of the non-solid-state battery without a negative electrode shown in Figure A.

[0027] Figure 5This is a schematic diagram of a solid-state lithium battery structure according to an embodiment of this application; wherein, Figure A is a schematic diagram of a solid-state battery structure without a negative electrode; Figure B is a schematic diagram of a battery structure with a negative electrode formed after the solid-state battery without a negative electrode shown in Figure A is charged and discharged;

[0028] Figure 6 This is a schematic diagram of a semi-solid-state lithium battery structure according to an embodiment of this application; wherein, Figure A is a schematic diagram of a semi-solid-state battery structure without a negative electrode; Figure B is a schematic diagram of a battery structure with a negative electrode formed after charging and discharging of the semi-solid-state battery without a negative electrode shown in Figure A. Detailed Implementation

[0029] To make the technical problems, technical solutions, and beneficial effects of this application clearer, the following detailed description is provided in conjunction with embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the scope of this application.

[0030] In this application, the term "and / or" describes the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, A and B existing simultaneously, or B existing alone. A and B can be singular or plural. The character " / " generally indicates that the preceding and following related objects have an "or" relationship.

[0031] In this application, "at least one" means one or more, and "more than one" means two or more. "At least one of the following" or similar expressions refer to any combination of these items, including any combination of single or multiple items. For example, "at least one of a, b, or c", or "at least one of a, b, and c", can both mean: a, b, c, ab (i.e., a and b), ac, bc, or abc, where a, b, and c can be single or multiple.

[0032] It should be understood that in the various embodiments of this application, the order of the above processes does not imply the order of execution. Some or all steps may be executed in parallel or sequentially. The execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiments of this application.

[0033] The terminology used in the embodiments of this application is for the purpose of describing particular embodiments only and is not intended to be limiting of this application. The singular forms “a,” “the,” and “the” used in the embodiments of this application and the appended claims are also intended to include the plural forms unless the context clearly indicates otherwise.

[0034] The weights of the relevant components mentioned in the embodiments of this application can refer not only to the specific content of each component, but also to the proportional relationship between the weights of the components. Therefore, any scaling up or down of the content of the relevant components according to the embodiments of this application is within the scope disclosed in the embodiments of this application. Specifically, the mass described in the embodiments of this application can be a mass unit known in the chemical industry, such as μg, mg, g, or kg.

[0035] Existing lithium metal batteries typically use lithium foil directly as the negative electrode. Due to the reactive chemical properties of lithium metal, lithium foil is easily oxidized by residual oxygen in the environment during processing as a negative electrode and battery assembly, forming lithium oxide. Lithium oxide has low conductivity, thus reducing the conductivity of the lithium foil electrode and increasing battery resistance. Achieving an extremely inert environment for lithium foil processing and battery assembly would inevitably increase the economic cost of these processes. Furthermore, current lithium foil processing methods still result in relatively thick foils, leading to an absolute surplus of lithium, resulting in lithium overload, increased costs, and reduced battery energy density. Based on this, the embodiments of this application propose the following lithium battery solution:

[0036] The lithium battery in this application embodiment includes a positive electrode and a negative current collector, and may also include necessary components such as an electrolyte, and may further include other auxiliary components.

[0037] The structure of the positive electrode in the lithium battery of this application embodiment can be as follows: Figures 4 to 6 The structure shown includes a positive electrode sheet 04 comprising a positive electrode current collector 41 and a positive electrode active layer 42 bonded to the surface of the positive electrode current collector 41.

[0038] The structure and material of the positive electrode current collector 41 can be conventional positive electrode current collectors, such as at least one of aluminum foil, carbon-coated aluminum foil, carbon cloth, and carbon paper, but are not limited thereto. In some embodiments, the thickness of the positive electrode current collector 41 can be 1 to 30 μm. For example, the thickness of the positive electrode current collector 41 can be 1 μm, 2 μm, 3 μm, 5 μm, 10 μm, 15 μm, 20 μm, 25 μm, 30 μm, etc. Of course, the positive electrode current collector 41 can also be an improved version of an existing positive electrode current collector or a completely new positive electrode current collector.

[0039] The positive electrode active layer 42 contains a positive electrode material. In this embodiment, the positive electrode material includes a composite positive electrode material, specifically a lithium-poor phase used as the positive electrode material and a lithium-rich phase used for lithium replenishment. The lithium-rich phase and the lithium-poor phase form a composite material, and during the first charge-discharge process, the lithium-rich phase at least... Figures 4 to 6The negative electrode current collector 51 migrates and forms a lithium-rich film layer 52 on its surface. Simultaneously, the lithium ions released by this lithium-rich phase during the first charge-discharge process can also replenish the lithium ions consumed by the SEI film. Since the composite cathode material also contains a lithium-poor phase, the lithium ions provided by this lithium-rich phase can also act as reversible lithium ions to replenish the lithium-poor phase, thereby improving the capacity of the cathode material and the energy density and cycle performance of the lithium battery.

[0040] In this embodiment, the composite cathode material contained in the positive electrode active layer 42 has a mass content of 50-99%. By controlling and adjusting the mass content of the composite cathode material in the positive electrode active layer 42, the aforementioned functions of the composite cathode material can be enhanced, the content and integrity of the lithium-rich film layer 52 can be increased, thereby improving the energy density and cycle performance of the lithium battery.

[0041] In this embodiment, the positive electrode active layer 42 further includes a conductive agent and a binder. In a further embodiment, the binder may have a mass content of 0.1-25%, and the binder may be a commonly used electrode binder, such as one or more of polyvinylidene chloride, soluble polytetrafluoroethylene, styrene-butadiene rubber, hydroxypropyl methylcellulose, methylcellulose, carboxymethyl cellulose, polyvinyl alcohol, acrylonitrile copolymer, sodium alginate, chitosan, and chitosan derivatives. These binders effectively enhance the mechanical properties of the positive electrode active layer 42, effectively improve the cycle performance of the positive electrode sheet 04, and enhance the function of the composite positive electrode material. The conductive agent may have a mass content of 0.1-25%, and the conductive agent may be a commonly used conductive agent, such as one or more of graphite, carbon black, acetylene black, graphene, carbon fiber, C60, and carbon nanotubes. These conductive agents effectively enhance the conductivity of the positive electrode active layer 42, effectively reduce the internal resistance of the positive electrode sheet, and effectively enhance the function of the composite positive electrode material.

[0042] The adhesive may be at least one of the following: polyvinylidene fluoride, silicone, polyvinylidene chloride, soluble polytetrafluoroethylene, styrene-butadiene rubber, hydroxypropyl methylcellulose, methylcellulose, carboxymethylcellulose, polyvinyl alcohol, acrylonitrile copolymer, sodium alginate, chitosan, and chitosan derivatives.

[0043] Of course, the positive electrode active layer 42 may further contain other positive electrode materials. These positive electrode materials can either function as the primary positive electrode material or synergistically enhance the composite positive electrode material, thereby increasing the capacity of the positive electrode sheet and fully utilizing the function of the composite positive electrode material. For example, when the positive electrode active layer 42 further contains other positive electrode materials, these other positive electrode materials may include phosphate-based positive electrode materials, ternary positive electrode materials, lithium cobalt oxide positive electrode materials, lithium nickel manganese oxide positive electrode materials, lithium-rich manganese-based positive electrode materials, and lithium manganese oxide positive electrode materials. When these other positive electrode materials are included, their content ranges from 0% to 50%.

[0044] In this embodiment, the thickness of the positive electrode active layer 42 can be 1 μm-500 μm. By adjusting its thickness, the thickness or content of the lithium-rich film layer 52 formed in the negative electrode current collector 51 can be effectively increased, thereby improving the energy density and cycle performance of the lithium battery.

[0045] Regarding the negative electrode current collector in the lithium battery of this application embodiment, it should be noted that the negative electrode current collector 51 in the lithium battery of this application embodiment does not contain negative electrode material before charging and discharging. Thus, since the lithium battery of this application embodiment has a composite positive electrode material set in the positive electrode active layer 42 within its positive electrode sheet 04, and uses the negative electrode current collector as the carrier of the negative electrode sheet, that is, before charging and discharging after assembly, the lithium battery of this application embodiment only contains the negative electrode current collector 51 and does not contain a negative electrode sheet. After charging and discharging, the composite positive electrode material can release lithium ions, and some of the released lithium ions can irreversibly accumulate on the surface of the negative electrode current collector 51 to form a lithium-rich film layer 52. This lithium-rich film layer 52 and the negative electrode current collector 51 form a negative electrode sheet after the lithium battery is charged and discharged. In this way, the negative electrode current collector 51 is directly used in the assembly stage of the lithium battery, avoiding the use of a negative electrode sheet, especially a lithium foil negative electrode. Its structure is effectively simplified, with low internal resistance, stable electrochemical performance such as cycle performance, and significantly reduced economic costs.

[0046] The negative electrode current collector 51 can be as follows: Figures 4 to 6 The structure shown can be, but is not limited to, sheet-like structures. In the embodiments, the material of the negative electrode current collector 51 includes one of the following: copper foil, carbon-coated copper foil, composite copper foil, copper mesh, copper foam, carbon paper, carbon cloth, etc. These materials of the negative electrode current collector 51 have good electrical conductivity and are conducive to forming a surface layer such as... Figures 4 to 6 The lithium-rich layer 52 in the middle also facilitates the formation of a film such as an SEI film. Of course, the negative electrode current collector 51 can also have other structural morphologies, and its material can also be other current collector materials suitable for negative electrodes. However, regardless of the material, it should have good conductivity.

[0047] In this embodiment, the thickness of the negative electrode current collector 51 can be 1 to 30 μm. For example, the thickness of the negative electrode current collector 51 can be 1 μm, 2 μm, 3 μm, 5 μm, 10 μm, 15 μm, 20 μm, 25 μm, 30 μm, etc.

[0048] Further research by the inventors revealed that the surface quality of the negative electrode current collector 51, such as its roughness, has a certain impact on the uniformity of the formation of the lithium-rich film layer 52 and the bonding strength between the lithium-rich film layer 52 and the surface of the negative electrode current collector 51. Further research shows that, in the embodiments of this application, the surface roughness of the negative electrode current collector 51 is R. aThe roughness is 0.5-20 μm, and more specifically, 0.5-10 μm. Controlling the surface roughness of the negative electrode current collector 51 within this range improves the uniformity of the lithium-rich film layer 52 formation. The resulting lithium-rich film layer 52 exhibits high bonding strength with the surface of the negative electrode current collector 51, thereby improving the cycle performance of the battery in this embodiment and reducing the impact of lithium dendrite formation. Figure 4 The diaphragm 06 or such Figure 5 The adverse effects of solid electrolyte 08 are mitigated, thereby improving the safety performance of lithium batteries.

[0049] In this embodiment, the lithium-rich film layer 52 includes a lithium metal layer. Specifically, lithium ions released from the lithium-rich phase of the composite cathode material contained in the cathode sheet 41 during the first charge-discharge process migrate to the surface of the negative electrode current collector 51, undergo redox reduction to generate elemental lithium metal, and form a lithium metal layer in situ on the surface of the negative electrode current collector 51. Thus, this lithium metal layer, together with the negative electrode current collector 51, constitutes the... Figures 4 to 6 The negative electrode substrate 05 is shown.

[0050] In this embodiment, the thickness of the lithium-rich film layer 52 is 5 nm-100 μm. The thickness of this lithium-rich film layer 52 is controlled and adjusted by the lithium ions provided by the composite positive electrode material contained in the positive electrode active layer 42 of the positive electrode sheet 04. Controlling the thickness of the lithium-rich film layer 52 ensures that it provides sufficient reversible lithium ions during charging and discharging, thereby improving the performance and energy density of the lithium battery. The 5 nm-100 μm thickness of the lithium-rich film layer 52 can be the thickness of the lithium metal layer generated on the surface of the negative electrode current collector 51.

[0051] Based on the above-mentioned scheme of positive electrode plate 04 and negative electrode current collector 51 contained in the lithium battery, in the embodiments of this application, the lithium battery of this application embodiment may have at least the following structure:

[0052] In the embodiments, such as Figure 4 As shown in Figure A, the lithium battery in this embodiment further includes a separator 06. In this case, the positive electrode 04, separator 06, and negative electrode current collector 51 are sequentially stacked to form a cell with a sandwich composite structure of positive electrode 04 / separator 06 / negative electrode current collector 51. This cell is wetted with a first liquid electrolyte 07. The symbol " / " indicates a stacked arrangement. Figure 4 As shown in Figure A, after charging and discharging, the lithium-rich phase contained in the composite positive electrode material of the positive electrode 04 irreversibly releases lithium ions. These lithium ions migrate to the negative electrode current collector 51 and form a lithium-rich film layer 52. This lithium-rich film layer 52 is formed on the surface of the negative electrode current collector 51 near the separator 06, specifically as shown in Figure A. Figure 4 As shown in Figure B. At this time. Figure 4 The lithium battery shown is a non-solid-state lithium battery, and the negative electrode current collector 51 and the lithium-rich film layer 52 formed on its surface constitute the negative electrode sheet 05.

[0053] In the embodiments, Figure 4 The separator 06 in the text can be a separator used in ion batteries, such as at least one of PE film, PP film, or coated film. This type of separator, while fully utilizing the functions of conventional separators, can assist composite cathode materials in performing the functions described above.

[0054] In the embodiments, Figure 4 The first liquid electrolyte 07 comprises the following components by weight percentage:

[0055] Lithium salts 5-15%;

[0056] Solvent 75-95%;

[0057] Additives: 0-10%.

[0058] The lithium salt may be at least one of LiPF6, LiFSI, and LiTFSI; the solvent may be at least one of TFPC, EC, PC, DEC, and DMC; and the additive may be at least one of VC, FEC, ES, PS, DMTFA, BTE, and LiPO4.

[0059] The first liquid electrolyte containing these components can function as a conventional electrolyte while also assisting the positive electrode material in performing its functions as described above, thereby facilitating the formation of a lithium-rich film 52 on the surface of the negative electrode current collector 51 and improving the formation rate and quality of the lithium-rich film 52.

[0060] In the embodiments, such as Figure 5 As shown in Figure A, the electrolyte in the lithium battery of this embodiment is a solid electrolyte 08. In this case, the solid electrolyte layer 08 is stacked between the negative electrode current collector 51 and the positive electrode active layer 42. That is, the positive electrode sheet 04, the solid electrolyte 08, and the negative electrode current collector 51 are stacked sequentially to form a sandwich composite structure of positive electrode sheet 04 / solid electrolyte 08 / negative electrode current collector 51. Here, " / " indicates a stacked arrangement. When... Figure 5 As shown in Figure A, after charging and discharging, the lithium-rich phase contained in the composite positive electrode material of the positive electrode 04 irreversibly releases lithium ions. These lithium ions migrate to the negative electrode current collector 51 and form a lithium-rich film layer 52. This lithium-rich film layer 52 is formed on the surface of the negative electrode current collector 51 of the solid electrolyte 08, specifically as shown in Figure A. Figure 5 As shown in Figure B. At this time. Figure 5 The lithium battery shown is a solid-state lithium battery, and the negative electrode current collector 51 and the lithium-rich film layer 52 formed on its surface constitute the negative electrode sheet 05.

[0061] In the embodiments, such as Figure 6As shown in Figure A, the electrolyte in the lithium battery of this embodiment consists of a solid electrolyte 08 and a second liquid electrolyte 09. In this case, the solid electrolyte layer 08 is stacked between the negative electrode current collector 51 and the positive electrode active layer 42, that is, the positive electrode sheet 04, the solid electrolyte 08, and the negative electrode current collector 51 are sequentially stacked to form a sandwich composite structure of positive electrode sheet 04 / solid electrolyte 08 / negative electrode current collector 51. Here, " / " indicates a stacked arrangement. The second liquid electrolyte 09 wets the solid electrolyte layer 08, the negative electrode current collector 51, and the positive electrode active layer 42. When... Figure 6 As shown in Figure A, after charging and discharging, the lithium-rich phase contained in the composite positive electrode material of the positive electrode 04 irreversibly releases lithium ions. These lithium ions migrate to the negative electrode current collector 51 and form a lithium-rich film layer 52. This lithium-rich film layer 52 is formed on the surface of the negative electrode current collector 51 of the solid electrolyte 08, specifically as shown in Figure A. Figure 6 As shown in Figure B. At this time. Figure 6 The lithium battery shown is a semi-solid lithium battery, and the negative electrode current collector 51 and the lithium-rich film layer 52 formed on its surface constitute the negative electrode sheet 05.

[0062] In the embodiments, Figure 5 and Figure 6 The thickness of the solid electrolyte layer can range from 1 μm to 200 μm. Figure 5 The thickness of the solid electrolyte layer and Figure 6 The thickness of the solid electrolyte layer can be the same or different.

[0063] In the embodiments, Figure 5 and Figure 6 The solid electrolyte layer contained therein can be at least one of polymer-based lithium salt electrolyte, oxide-based electrolyte, and sulfide-based electrolyte. The solid electrolyte layer containing these solid electrolytes can perform the functions of a conventional electrolyte while also assisting the positive electrode material in performing its functions as described above, thereby facilitating the formation of a lithium-rich film layer 52 on the surface of the negative electrode current collector 51 and improving the formation rate and quality of the lithium-rich film layer 52.

[0064] in addition, Figure 5 The solid electrolyte contained in the middle solid electrolyte layer and Figure 6 The solid electrolytes contained in the middle solid electrolyte layer can be the same or different.

[0065] In the embodiments, Figure 6 The second liquid electrolyte 09 comprises the following components by weight percentage:

[0066] Lithium salts 5-15%;

[0067] Solvent 75-95%;

[0068] Additives: 0-10%.

[0069] The lithium salt may be at least one of LiPF6, LiFSI, and LiTFSI; the solvent may be at least one of TFPC, EC, PC, DEC, and DMC; and the additive may be at least one of VC, FEC, ES, PS, DMTFA, BTE, and LiPO4.

[0070] The second liquid electrolyte containing these components can function as a conventional electrolyte while also assisting the positive electrode material in performing its functions as described above, thereby facilitating the formation of a lithium-rich film 52 on the surface of the negative electrode current collector 51 and improving the formation rate and quality of the lithium-rich film 52.

[0071] The composite cathode material contained in the positive electrode sheet 04 of the lithium battery in the above embodiments is specifically the composite cathode material described below.

[0072] The composite cathode material of this application includes a lithium-poor phase as the cathode material and a lithium-rich phase for lithium replenishment, and the lithium-rich phase and the lithium-poor phase form a composite material.

[0073] In this embodiment, the lithium-poor phase in the composite cathode material functions as the cathode material itself, thus playing a role in lithium ion insertion / extraction during charge / discharge. The lithium-rich phase, composite with the lithium-poor phase, refers to a material that releases lithium ions during charge / discharge, and these released lithium ions can be reversibly and abundantly added to the negative electrode current collector or the surface of the negative electrode material, thus serving as a lithium replenishment agent. Simultaneously, it can also reversibly replenish the lithium-poor phase with lithium ions. Therefore, during the initial charge / discharge process, the lithium-rich phase can effectively release lithium ions, forming a lithium-containing film layer on the negative electrode. This can replenish the lithium ions consumed by the SEI film and eliminate the need for an additional lithium-rich negative electrode. Furthermore, the lithium ions provided by the lithium-rich phase can also reversibly replenish the lithium-poor phase, thereby improving the cathode material's capacity, battery energy density, and cycle performance.

[0074] The composite cathode material of this application can be composed of either a lithium-poor phase or a lithium-rich phase in any way that allows both phases to exert a synergistic effect, such as at least one of the following composite embodiments A to C:

[0075] Composite Example A: As Figure 1 As shown, the lithium-poor phase has a porous structure 11, and the lithium-rich phase is filled in the porous structure 11 of the lithium-poor phase.

[0076] In the above-described composite embodiment A, the lithium-poor phase acts as a carrier for the positive electrode material, loading the lithium-rich phase and allowing the lithium-rich phase to be relatively uniformly embedded in the positive electrode material carrier, specifically in its porous structure 11. On the one hand, this enhances the uniformity of the dispersion of the lithium-rich phase among the lithium-poor phases, improving the synergistic effect between the two. This allows the lithium-rich phase to effectively improve its efficiency in providing reversible ions to the lithium-poor phase while simultaneously providing irreversible lithium ions to the negative electrode. On the other hand, embedding the lithium-rich phase into the porous structure 11 of the lithium-poor phase provides protection for the lithium-rich phase, such as isolating it from environmental moisture and harmful gases like carbon dioxide, thereby improving the stability of the lithium-rich phase and thus endowing the composite positive electrode material with processing and storage properties.

[0077] In the embodiments, Figure 1 The lithium-depleted phase in the lithium-depleted phase has a particle size of 500 nm-100 μm, more specifically 500 nm-30 μm, and even more specifically 500 nm-20 μm. In another embodiment, the pore diameter of the porous structure 11 in the lithium-depleted phase is 5 nm-10 μm, more specifically 5 nm-3 μm. In yet another embodiment, the pore distribution density of the porous structure 11 in the lithium-depleted phase is 1%-50%, more specifically 10%-50%, and even more specifically 20%-40%. By controlling and adjusting at least one of the particle size, pore diameter, and pore diameter distribution density of the lithium-depleted phase, the capacity and density of the lithium-depleted phase as a cathode material can be improved based on the effective loading of the lithium-rich phase, thereby improving the capacity and compaction density of the composite cathode material.

[0078] Composite Example B: As Figure 2 As shown, the lithium-rich phase is the lithium-rich core 21, and the lithium-poor phase forms a lithium-poor coating layer 22, which coats the lithium-rich core 21.

[0079] In the aforementioned composite embodiment B, the lithium-rich phase serves as the core, thus the lithium-poor phase acts as a protective layer, effectively isolating the lithium-rich phase from environmental moisture and harmful gases such as carbon dioxide. This improves the stability of the lithium-rich phase, thereby enhancing the processing and storage properties of the composite cathode material. Furthermore, as the core, the lithium-rich phase is positioned along the lithium-poor phase's path during delithiation. The lithium ions supplied by the lithium-rich phase first contact the lithium-poor phase coating layer 22, replenishing the lithium-poor phase with intercalation-deintercalation lithium ions. These lithium ions then migrate to the negative electrode to form a lithium-containing film. The lithium-poor phase, acting as a coating layer, shortens the reversible lithium ion intercalation-deintercalation efficiency and migration path, thereby improving the cycle performance of the composite cathode material.

[0080] In the embodiments, the particle size of the lithium-rich core 21 in the above-mentioned composite embodiment B is 50nm-100μm, further 500nm-30μm, and even further 500nm-20μm. It can be primary particles, secondary particles, or a mixture of primary and secondary particles. In another embodiment, the thickness of the lithium-poor coating layer 22 is 5nm-10μm, further 5nm-8μm, and even further 5nm-3μm. By controlling the particle size of the lithium-rich core 21 and / or the thickness of the lithium-poor coating layer 22, the synergistic effect between the lithium-poor phase and the lithium-rich phase can be improved, thereby improving the electrochemical performance of the composite cathode material, such as capacity, battery energy density, and cycle performance.

[0081] In this embodiment, the lithium-poor coating layer 22 is also doped with a lithium-rich phase, and the lithium-rich phase doped in the lithium-poor coating layer 22 exhibits a gradient decreasing distribution from the lithium-rich core 21 to the outer surface of the lithium-poor coating layer 22. In a further embodiment, the mass of the lithium-rich phase doped in the lithium-poor coating layer 22 is controlled to be 0-50% of the mass of the lithium-poor coating layer 22, more specifically 5-50%, and even more specifically 10-30%. Thus, the gradient decreasing doping of the lithium-rich phase in the lithium-poor coating layer 22 improves the contact between the lithium-rich and lithium-poor phases, increases the efficiency of lithium-ion extraction from the lithium-rich phase to the lithium-poor phase, and also avoids direct contact between the lithium-rich phase and the external environment, thereby improving the stability of the lithium-rich phase doped in the lithium-poor coating layer 22. The lithium-rich phase doped in the lithium-poor coating layer 22 is not limited to a single particle.

[0082] Composite Example C: As Figure 3 As shown in Figure A, the lithium-poor phase is the lithium-poor core 31, and the lithium-rich phase forms a lithium-rich coating layer 32, which coats the lithium-poor core 31.

[0083] In the above-described composite embodiment C, a lithium-rich phase is used as the lithium-rich coating layer 32. During the initial charge-discharge process, the lithium-rich coating layer 32 preferentially delithiates and releases lithium ions, forming a lithium-containing film on the negative electrode, thus reducing or preventing lithium ion consumption from the lithium-poor phase. Simultaneously, the lithium-rich coating layer 32 can also replenish the lithium-poor phase in the lithium-poor core 31 with intercalable lithium ions, thereby improving the electrochemical performance of the composite cathode material, including capacity, battery energy density, and cycle performance.

[0084] In the embodiments, the particle size of the lithium-poor core 31 in the above-mentioned composite embodiment C is 50nm-100μm, further 500nm-30μm, and even further 500nm-20μm. It can be primary particles, secondary particles, or a mixture of primary and secondary particles. In another embodiment, the thickness of the lithium-rich coating layer 32 is 5nm-10μm, further 5nm-8μm, and even further 5nm-3μm. By controlling the particle size of the lithium-poor core 31 and / or the thickness of the lithium-rich coating layer 32, the synergistic effect between the lithium-poor phase and the lithium-rich phase can be improved, thereby improving the electrochemical performance of the composite cathode material, such as capacity, battery energy density, and cycle performance.

[0085] In this embodiment, the lithium-rich coating layer 32 is also doped with a lithium-poor phase, and the lithium-poor phase doped in the lithium-rich coating layer 32 exhibits a gradient decreasing distribution from the lithium-poor core 31 to the outer surface of the lithium-rich coating layer 32. In a further embodiment, the mass of the lithium-poor phase doped in the lithium-rich coating layer 32 is controlled to be 0-50% of the mass of the lithium-rich coating layer 32, more specifically 5-50%, and even more specifically 10-30%. Thus, the gradient decreasing doping of the lithium-poor phase in the lithium-rich coating layer 32 improves the contact between the lithium-rich and lithium-poor phases, thereby increasing the efficiency of lithium ion insertion / extraction from the lithium-rich phase to the lithium-poor phase.

[0086] In a further embodiment, such as Figure 3 As shown in Figure B, a functional encapsulation layer 33 is also provided on the outer surface of the lithium-rich coating layer 32. The presence of this encapsulation layer 33 effectively encapsulates the lithium-rich coating layer 32, preventing the lithium-rich phase in the coating layer 32 from directly contacting the environment, such as isolating it from adverse factors like water vapor and carbon dioxide. This ensures the stability of the lithium-rich phase, fully leveraging its lithium-supplementing effect and the synergistic effect between the lithium-rich and lithium-poor phases, thereby improving the electrode material activity of the composite cathode material. In this embodiment, the thickness of the encapsulation layer 33 can be controlled to be 5-1000 nm, further 10-800 nm, and even further 50-500 nm. By controlling and adjusting the thickness of the encapsulation layer 33, the composite cathode material's storage and processing performance, energy density and capacity retention, and cycle performance can be guaranteed.

[0087] In this embodiment, the encapsulation functional layer 33 can be a composite layer structure of an ion conductor encapsulation layer, an electronic conductor encapsulation layer, or an ion conductor encapsulation layer or an electronic conductor encapsulation layer. The ion conductor encapsulation layer can improve the lithium-ion intercalation / deintercalation effect and the lithium-ion ionic conductivity of the lithium-rich phosphate cathode material.

[0088] When the encapsulation functional layer 33 includes an ion conductor encapsulation layer, the material of the ion conductor encapsulation layer can be a material that is beneficial to improving ion conductivity, such as, but not limited to, at least one of perovskite, NASICON, and garnet types. The perovskite type may include Li. 3x La 2 / 3-x TiO3(LLTO), specifically Li 0.5 La 0.5 TiO3, Li 0.33 La 0.57 TiO3, Li 0.29 La 0.57 TiO3, Li 0.33 Ba 0.25 La 0.39 TiO3, (Li 0.33 La 0.56 ) 1.005 Ti 0.99 Al 0.01 O3, Li 0.5 La 0.5 Ti 0.95 Zr 0.05 At least one of O3, etc., NASICON type such as, but not limited to, Li1.4Al0.4Ti1.6(PO4)3(LATP), garnet type can include Li7La3Zr2O 12 (LLZO), Li 6·4 La3Zr 1·4 Ta 0·6 O 12 Li 6.5 La3Zr 1.5 Ta 0.5 O 12 At least one of the following. By selecting the appropriate material for the ion conductor encapsulation layer, the ionic conductivity of the ion conductor encapsulation layer can be further improved. The thickness of the ion conductor encapsulation layer can also be adjusted as needed, but it should be conducive to ion conduction while also being conducive to isolating the core and stabilizing the lithium-rich phosphate cathode material, i.e., the core.

[0089] When the encapsulation functional layer 33 includes an electronic conductor encapsulation layer, the material of this electronic conductor encapsulation layer can be a material that is beneficial to improving electronic conductivity, such as, but not limited to, at least one of carbon materials, conductive oxides, and conductive organic materials. Specifically, when the material of the electronic conductor encapsulation layer is a carbon material, the carbon material can include at least one of amorphous carbon, carbon nanotubes, graphite, carbon black, and graphene. When the material of the electronic conductor encapsulation layer is a conductive oxide, the conductive oxide can include at least one of In₂O₃, ZnO, and SnO₂. The conductive organic material can be a conductive polymer, etc. By selecting the material of the electronic conductor encapsulation layer, the electronic conductivity of the electronic conductor encapsulation layer can be further improved. The thickness of the electronic conductor encapsulation layer can also be adjusted as needed, but it should be conducive to electron conduction while also being conducive to isolating the core and stabilizing the lithium-rich phosphate cathode material, i.e., the core.

[0090] In addition, the encapsulation functional layer 33 may also include other functional layers as needed, and the types of other functional layers can be flexibly selected as required. Regardless of the above-mentioned composite method of lithium-rich phase and lithium-poor phase, the mass ratio of lithium-rich phase to lithium-poor phase can be controlled to be 1:(0.01-100).

[0091] In the embodiments, the lithium-deficient phase may include at least one of phosphate-based cathode materials, ternary cathode materials, and lithium cobalt oxide cathode materials, but is not limited thereto. When the lithium-deficient phase is a phosphate-based cathode material, it may include Li (1-x) A y B (1-y) PO4, wherein A is selected from at least one of the metallic elements Fe, Co, Ni, and Mn, and B is selected from at least one of the metallic elements Fe, Co, Ni, Mn, V, Mg, Ca, Cr, Cu, Zn, Ti, and Sn, and the values ​​of x and y satisfy: 0 <x≤1,0<y≤1。

[0092] Based on this Li (1-x) A y B (1-y) The elements and proportions contained in PO4 can vary depending on the value of x, resulting in materials with different lithium contents. In some specific embodiments, the value of x can be 1, 0.95, 0.9, 0.85, 0.8, 0.75, 0.7, 0.65, 0.6, 0.55, 0.5, 0.45, 0.4, 0.35, 0.3, 0.25, 0.2, 0.15, 0.1, 0.05, 0.03, 0.02, 0.01, 0.001, etc.

[0093] Specifically, when x approaches 0, the lithium-ion content of the phosphate-based cathode material is high; as the value of x increases, the lithium-ion content of the phosphate-based cathode material gradually decreases, and the phosphate-based cathode material becomes lithium-poor; when x = 1, Li...(1-x) A y B (1-y) The chemical formula of PO4 is A y B (1-y) PO4. At this time, the phosphate-based cathode material becomes a lithium-free material.

[0094] Correspondingly, the value of y satisfies: 0 < y ≤ 1. In some specific embodiments, the value of y can be specific values such as 1, 0.95, 0.9, 0.85, 0.8, 0.75, 0.7, 0.65, 0.6, 0.55, 0.5, 0.45, 0.4, 0.35, 0.3, 0.25, (1-x) (1-x) A y B (1-y) PO4 does not contain element B. At this time, the chemical formula corresponds to Li (1-x) APO4.

[0095] In some embodiments of the present application, Li (1-x) A y B (1-y) PO4 is Li 1-x FePO4, Li 1-x MnPO4, Li 1-x CoPO4, Li 1-x NiPO4, Li 1-x Fe y Mn 1-y PO4, Li 1-x Fe y Co 1-y PO4, Li 1-x Fe y Ni 1-y PO4, Li 1-x Mn y Co[[ID=,60]] 1-y PO4, Li 1- x Mn y Ni 1-y PO4, Li 1-x Co[[ID=,71]] y Ni 1-y At least one of PO4.

[0096] In the embodiment, the above-mentioned lithium-rich phase can release lithium ions during charge and discharge to supplement lithium in the negative electrode current collector or the lithium supplement material on the surface of the negative electrode material, and at the same time can also provide reversible lithium ions for the lithium-poor phase to supplement lithium, such as the above-mentioned Li (1-x) A y B (1-y)The x-value in the lithium-lean phase of PO4 tends to be 1 to improve the capacity of the lithium-lean phase. In some embodiments, the lithium-rich phase includes lithium-rich metal oxides. In the embodiments, the lithium-rich metal oxide material includes at least one of Li5MO4, Li2MO2, Li6MO4, and Li8MO6, wherein M can be selected from at least one of the metal elements Fe, Co, Ni, Mn, Al, Cr, Ga, In, La, and Bi. As part of the composite cathode material, the above-mentioned lithium-rich metal oxide material can release irreversible lithium ions through an electrochemical reaction during charging, and the released lithium ions can be enriched on the surface of the negative electrode current collector or the negative electrode material to form an SEI film or a lithium-rich film layer. This lithium-rich film layer can directly form on the surface of the negative electrode current collector to play the role of a negative electrode active material, thereby avoiding the problems described in the background caused by using lithium foil as a negative electrode. Moreover, these lithium-rich metal oxide materials can also simultaneously replenish reversibly lithium ions to the lithium-lean phase, improving the capacity and cycle performance of the lithium-lean phase.

[0097] For example, when lithium-rich metal oxide materials include Li5MO4, Li5MO4 releases lithium ions during the first charge of the battery. Because the material after lithium release has better structural stability, Li5MO4 provides irreversible lithium-rich capacity. Li5MO4 can not only enrich lithium-poor or lithium-free phosphate systems... (1-x) A y B (1-y) PO4 provides lithium ions, and the excess irreversible lithium ions migrate to the negative electrode current collector to form a lithium metal layer, which functions as a negative electrode active material.

[0098] In some specific embodiments, Li5MO4 can be oxides such as Li5FeO4, Li5AlO4, Li5BiO4, Li5NiO4, Li5CoO4, Li5MnO4, Li5CrO4, Li5GaO4, Li5InO4, Li5LaO4, and Li5BiO4.

[0099] Based on the lithium-poor and lithium-rich phases contained in the aforementioned composite cathode material, in some embodiments, the composite cathode material contains a phosphate-based cathode material and Li5MO4 compounded with the phosphate-based cathode material, and the general structural formula of the composite cathode material is 5Li. (1-x) A y B (1-y) PO4·zxLi5MO4; where Li (1-x) A y B (1-y) For PO4, A, B, x, and y are as described above, and the value of z satisfies: 1 ≤ z. At this point, the lithium-rich phase Li5MO4 and the lithium-poor phase Li... (1-x) A y B (1-y)PO4 and PO4 each play their respective roles as described above, and the two can have a synergistic effect, improving the capacity and cycle performance of the composite cathode material.

[0100] As an example, when Li (1-x) A y B (1-y) In PO4, x is 1, and Li (1-x) A y B (1-y) The chemical formula of PO4 is A y B (1-y) PO4, at this point, the phosphate-based cathode material is in a lithium-free state. Under these conditions, during the first charge, the lithium-rich phase Li5MO4 can irreversibly provide lithium ions, some of which replenish the Li-2 phase. (1-x) A y B (1-y) In PO4, make A y B (1-y) PO4 is rich in reversible lithium ion insertion and extraction for lithium extraction and insertion during battery cycling. At the same time, Li5MO4 irreversibly provides lithium ions that can migrate to the negative electrode and form a lithium-rich film.

[0101] As another example, Li (1-x) A y B (1-y) In PO4, x is less than 1 but not 0. At this time, Li (1-x) A y B (1-y) PO4 is in a lithium-deficient state. In this condition, during the first charge, the lithium-rich Li5MO4 can irreversibly provide lithium ions, with some of these ions replenishing the Li4+. (1-x) A y B (1-y) In PO4, Li (1-x) A y B (1-y) PO4 is rich in reversible lithium-ion intercalation and deintercalation to facilitate lithium extraction and intercalation during battery cycling. Simultaneously, Li5MO4 irreversibly provides lithium ions that can migrate to the negative electrode and form a lithium-rich film.

[0102] In some specific embodiments, Li5MO4 can be Li5FeO4, corresponding to 5Li (1-x) A y B (1-y) PO4·zxLi5MO4 is Li 1-x FePO4·zxLi5FeO4、Li 1-x Fe y Mn 1-yAt least one of PO4·zxLi5FeO4. Among them, Li5FeO4 has a suitable de-lithiation potential, high cost performance, and stable products after battery charging and de-lithiation, and has almost no reversible capacity within the working voltage range.

[0103] In the embodiments of the present application, taking the molar amount of Li (1-x) A y B (1-y) PO4 as 5, the molar amount of Li5MO4 is zx. Here, zx represents the product between z and x, and the values of x and z satisfy: 0 < x ≤ 1, 1 ≤ z. In the embodiments of the present application, the excess amount of lithium ions in the cathode material can be adjusted by controlling the value of z, so as to supplement sufficient lithium ions for the lithium battery system.

[0104] In a possible implementation manner, the value of z satisfies: 1 ≤ z ≤ 100. At this time, after the first charge of the assembled battery, Li5MO4 releases lithium capacity, and the excess irreversible lithium ions migrate to the negative current collector to form a lithium-rich film layer with a thickness of 5 nm - 100 μm. Exemplarily, the value of z can be numerical values such as 1, 3, 5, 10, 20, 30, 40, 50, 60, 70, 80, 90, 100, etc.

[0105] Second, the embodiments of the present application provide a preparation method for the above composite cathode material. The preparation method of the embodiments of the present application includes the following steps:

[0106] S01: Provide a lithium-poor phase as the cathode material and a lithium-rich phase for providing lithium ions;

[0107] S02: Perform composite treatment and heat treatment on the lithium-poor phase and the lithium-rich phase in a certain proportion to obtain a composite cathode material.

[0108] In this way, the preparation method of the composite cathode material in the embodiments of the present application performs composite treatment on the lithium-poor phase and the lithium-rich phase to form a composite cathode material, and can endow the prepared composite cathode material with a lithium supplementing function and high-capacity characteristics, and has stable electrochemical performance and good storage performance. In addition, the preparation method of the composite cathode material can ensure the stable electrochemical performance of the prepared composite cathode material, high efficiency, and cost savings in production.

[0109] In step S01, both the lithium-poor phase and the lithium-rich phase are the lithium-poor phase and lithium-rich phase contained in the composite cathode material described above. Therefore, as in the embodiments, the lithium-rich phase may include lithium-rich metal oxides. In further embodiments, the lithium-rich metal oxide material includes at least one of Li5MO4, Li2MO2, Li6MO4, and Li8MO6; wherein M is selected from at least one of the metal elements Fe, Co, Ni, Mn, Al, Cr, Ga, In, La, and Bi. In the embodiments, the lithium-poor phase may include at least one of phosphate-based cathode materials, ternary cathode materials, lithium cobalt oxide cathode materials, lithium manganese oxide cathode materials, and lithium nickel manganese oxide cathode materials; wherein the phosphate-based cathode material may be Li (1-x) A y B (1-y) PO4.

[0110] In addition, the lithium-poor phase and the lithium-rich phase can be prepared according to their respective types and corresponding preparation methods, such as by existing methods.

[0111] In step S02, the composite treatment and heat treatment combine the lithium-poor phase and the lithium-rich phase to form a composite cathode material. Furthermore, the heat treatment temperature in step S02 should be lower than the sintering temperature of the lithium-poor and lithium-rich phases. This sintering temperature should be understood as the sintering temperature at which the lithium-poor phase precursor is sintered to prepare the lithium-poor phase, and the lithium-rich phase precursor is sintered to prepare the lithium-rich phase. Setting this heat treatment temperature lower than the sintering temperature ensures that the lithium-poor and lithium-rich phases do not melt or migrate during the heat treatment process.

[0112] In one embodiment, the method for combining and heat-treating a lithium-poor phase and a lithium-rich phase in a certain proportion includes the following steps:

[0113] The lithium-poor phase has a porous structure. The lithium-rich phase is filled into the porous structure of the lithium-poor phase and then heat-treated.

[0114] This method enables the preparation of the composite cathode material with the structure of the composite embodiment A described above. The heat treatment is used to stabilize the lithium-rich phase within the porous structure of the lithium-poor phase, thereby improving the stability of the prepared composite cathode material structure. The parameters of the lithium-poor phase and its contained porous structure, such as the lithium-poor phase particle size, the porosity of the porous structure, and the pore density, are the same as those of the lithium-poor phase in the composite embodiment A described above. The parameters of the lithium-rich phase are also the same as those of the lithium-rich phase in the composite embodiment A described above.

[0115] In one embodiment, the method for combining and heat-treating a lithium-poor phase and a lithium-rich phase in a certain proportion includes the following steps:

[0116] The lithium-rich phase is used as the lithium-rich core, and the lithium-poor phase is coated on the interface of the lithium-rich core and then subjected to heat treatment.

[0117] This method enables the preparation of composite cathode materials with the structure of Embodiment B in the above application. The heat treatment is performed to stabilize the lithium-poor phase coating layer structure formed at the lithium-rich core interface or surface, and to ensure strong bonding with the lithium-rich core interface, thereby improving the stability of the composite cathode material structure.

[0118] In a further embodiment, as described in the composite embodiment B of the above text application, when the lithium-poor phase contains a lithium-rich phase doped with it, during the process of coating the lithium-poor phase onto the lithium-rich core interface, a mixture containing a certain amount of the lithium-rich phase and the lithium-poor phase can be formed and coated together onto the lithium-rich core interface. Furthermore, during the formation of the coating layer, the coating process can be performed multiple times to control the content of the lithium-rich phase in the coating layer, such as controlling the lithium-rich phase to have a gradient decreasing distribution in the coating layer.

[0119] The parameters for the lithium-poor phase and the lithium-rich phase are the same as those for the lithium-poor phase and the lithium-rich phase in the composite embodiment C structure of the above application.

[0120] In one embodiment, the method for combining and heat-treating a lithium-poor phase and a lithium-rich phase in a certain proportion includes the following steps:

[0121] The lithium-poor phase is used as the lithium-poor core, and the lithium-rich phase is coated on the interface of the lithium-poor core before heat treatment.

[0122] This method enables the preparation of a composite cathode material with the structure of Embodiment C in the above application. The heat treatment is performed to stabilize the lithium-rich phase coating layer structure formed at the lithium-poor core interface or surface, and to ensure strong bonding with the lithium-poor core interface, thereby improving the stability of the composite cathode material structure.

[0123] In a further embodiment, as described in the composite embodiment C of the above text application, when the lithium-rich phase contains a lithium-poor phase, during the process of coating the lithium-rich phase onto the lithium-poor core interface, a mixture containing a certain amount of the lithium-poor phase and the lithium-rich phase can be formed and coated together onto the lithium-poor core interface. Moreover, during the formation of the coating layer, the coating process can be performed multiple times to control the content of the lithium-poor phase in the coating layer, such as controlling the lithium-poor phase to have a gradient decreasing distribution in the coating layer.

[0124] The parameters for the lithium-poor phase and the lithium-rich phase are the same as those for the lithium-poor phase and the lithium-rich phase in the composite embodiment C structure of the above application.

[0125] In addition, the heat treatment in the above embodiments is to improve the bonding strength between the lithium-rich phase and the lithium-poor phase and improve the electrochemical performance of the interface between the two. Therefore, in the embodiments, the temperature of the heat treatment should be lower than the melting temperature of the lithium-rich phase and the lithium-poor phase. For example, in the embodiments, the temperature range of the heat treatment in the above embodiments can be 200-800℃, and further can be 500-700℃.

[0126] The following examples illustrate the lithium battery embodiments of this application through several specific implementations.

[0127] The following description is based on specific embodiments.

[0128] Example 1

[0129] This embodiment provides a negative electrode-free lithium battery. The structure of this negative electrode-free lithium battery before charging and discharging is as follows: Figure 4 Figure A shows a battery cell with a positive electrode and a negative current collector arranged opposite each other, a spacer membrane between the positive and negative current collectors, and a liquid electrolyte wetting the cell; wherein...

[0130] The positive electrode sheet includes a 20 μm thick aluminum foil and a 90 μm thick positive electrode material layer bonded to the surface of the aluminum foil. The positive electrode material layer includes a composite positive electrode material with a mass ratio of 95:2:3, SuperP conductive agent and PVDF binder. The composite positive electrode material is a phosphate-based positive electrode material FePO4·0.5Li5FeO4.

[0131] The negative electrode current collector is a 10 μm thick carbon-coated copper foil with a surface roughness R. a Approximately 3μm;

[0132] The diaphragm is a PE membrane with a thickness of 10μm;

[0133] The liquid electrolyte is 1M LiPF6.

[0134] In the positive electrode sheet, the FePO4 phase in the phosphate-based positive electrode material FeO4FePO4·0.5Li5FeO4 is lithium-poor, while the lithium-rich phase is Li5FeO4. The lithium-poor FePO4 phase consists of porous, large particles with a particle size D. 50 The particle size is approximately 6 μm, with an average pore size of approximately 300 nm; the lithium-rich Li5FeO4 phase consists of small particles with a particle size D. 50 Approximately 200 nm; Li5FeO4 fills the porous structure of FePO4 to form a garnet-like composite cathode material.

[0135] The preparation method of the phosphate-based cathode material FeO4FePO4·0.5Li5FeO4 in this embodiment includes the following steps:

[0136] S1. Preparation of lithium-poor FePO4 phase: Iron source, phosphate and pore-forming agent are mixed evenly according to stoichiometric ratio, precipitant is added for co-precipitation to obtain FePO4 precursor, pore-forming agent in precursor is washed and heat-treated to obtain porous lithium-poor FePO4 phase.

[0137] Preparation of S2. Li5FeO4 lithium-rich phase: Iron source and lithium source were mixed evenly in stoichiometric ratio, solvent was evaporated to obtain precursor, additional lithium source was added appropriately and ball-milled evenly with precursor, high-temperature solid-state sintering, and sand milling to nano-size to obtain Li5FeO4 lithium-rich phase.

[0138] S3. Composite treatment and heat treatment of lithium-poor and lithium-rich phases: The porous FePO4 lithium-poor phase and the nano Li5FeO4 lithium-rich phase are prepared according to the stoichiometric ratio, mixed uniformly by high-energy ball milling, and the structure is stabilized by medium-low temperature heat treatment at 600℃ to obtain garnet-shaped FePO4·0.5Li5FeO4 phosphate-based cathode material.

[0139] Example 2

[0140] This embodiment provides a negative electrode-free lithium battery. The structure of this negative electrode-free lithium battery before charging and discharging is as follows: Figure 5 Figure A shows a positive electrode and a negative current collector positioned opposite each other, with a solid electrolyte layer disposed between them; wherein...

[0141] The positive electrode sheet includes a 20 μm thick aluminum foil and a 90 μm thick positive electrode material layer bonded to the surface of the aluminum foil. The positive electrode material layer includes a composite positive electrode material with a mass ratio of 95:2:3, SuperP conductive agent and PVDF binder. The composite positive electrode material is a phosphate-based positive electrode material FePO4·0.5Li5FeO4.

[0142] The negative electrode current collector is a 10 μm thick carbon-coated copper foil with a surface roughness of R. a Approximately 3μm

[0143] The solid electrolyte layer is lithium titanium aluminum phosphate (LATP) with a thickness of 40 μm.

[0144] Among them, the Li5FeO4 in the phosphate-based cathode material FePO4·0.5Li5FeO contained in the cathode sheet is a lithium-rich phase, and as a lithium-rich core, the particle size D 50 The thickness is approximately 3 μm; Li5FeO is a lithium-poor phase and forms a lithium-poor coating layer that coats the lithium-rich core, with a thickness of approximately 3 μm.

[0145] The preparation method of the phosphate-based cathode material FePO4·0.5Li5FeO in this embodiment includes the following steps:

[0146] Preparation of Li5FeO4 lithium-rich phase: Iron source and lithium source were mixed evenly according to stoichiometric ratio, solvent was evaporated to obtain precursor, additional lithium source was added appropriately and ball-milled evenly with precursor, and high-temperature solid-state sintering was performed to obtain Li5FeO4 lithium-rich phase.

[0147] S2. Preparation of lithium-poor FePO4 precursor: Iron source and phosphate were mixed evenly according to stoichiometric ratio, and a precipitant was added for co-precipitation to obtain nano FePO4 precursor;

[0148] S3. Composite treatment and heat treatment of lithium-poor and lithium-rich phases: Large-particle Li5FeO4 lithium-rich phase and nano-FePO4 lithium-poor phase precursor are prepared according to stoichiometric ratio, mixed uniformly by high-energy ball milling, and then sintered at 650℃ to fuse the nano-FePO4 lithium-poor phase precursor structure and form a highly crystalline nano-FePO4 lithium-poor phase. At the same time, it is bonded to the interface of the Li5FeO4 lithium-rich phase, and finally forms a core-shell structure FePO4·0.25Li5FeO4 phosphate cathode material with lithium-poor phase encapsulating lithium-rich phase.

[0149] Example 3

[0150] This embodiment provides a negative electrode-free lithium battery. The structure of this negative electrode-free lithium battery before charging and discharging is as follows: Figure 6 Figure A shows a composite structure consisting of a positive electrode and a negative current collector arranged opposite each other, with a solid electrolyte layer between them, and the positive electrode, solid electrolyte layer, and negative current collector all wetted by a liquid electrolyte.

[0151] The positive electrode sheet includes a 20 μm thick aluminum foil and a 90 μm thick positive electrode material layer bonded to the surface of the aluminum foil. The positive electrode material layer includes a composite positive electrode material with a mass ratio of 95:2:3, SuperP conductive agent and PVDF binder. The composite positive electrode material is a phosphate-based positive electrode material FePO4·0.5Li5FeO4.

[0152] The negative electrode current collector is a 10 μm thick carbon-coated copper foil with a surface roughness of R. a Approximately 3μm

[0153] The solid electrolyte layer is lithium titanium aluminum phosphate (LATP) with a thickness of 40 μm.

[0154] The liquid electrolyte is 1M LiPF6.

[0155] The phosphate-based positive electrode material FePO4·0.5Li5FeO4 contained in the positive electrode sheet is the same as the phosphate-based positive electrode material FePO4·0.5Li5FeO4 in Example 1.

[0156] Example 4

[0157] This embodiment provides a negative electrode-free lithium battery. The structure of this negative electrode-free lithium battery before charging and discharging is the same as that of the negative electrode-free lithium battery in Embodiment 1, the difference being that the composite positive electrode material is a phosphate-based positive electrode material, FePO4·0.25Li5FeO4.

[0158] Furthermore, the phosphate-based positive electrode material FePO4·0.25Li5FeO4 contained in the positive electrode sheet in this embodiment is the same as the phosphate-based positive electrode material FePO4·0.5Li5FeO4 in Example 2.

[0159] Example 5

[0160] This embodiment provides a negative electrode-free lithium battery. The structure of this negative electrode-free lithium battery before charging and discharging is the same as that of the negative electrode-free lithium battery in Embodiment 1, the difference being that the composite positive electrode material is a phosphate-based positive electrode material, Fe. 0.4 Mn 0.6 PO4·0.25Li5FeO4;

[0161] Among them, the positive electrode contains phosphate-based positive electrode material Fe 0.4 Mn 0.6 Fe in PO4·0.25Li5FeO4 0.4 Mn 0.6 PO4 is a lithium-poor phase and forms the lithium-poor core, with a particle size D. 50 The thickness is approximately 1 μm; Li5FeO4 is a lithium-rich phase and forms a lithium-rich coating layer that coats the lithium-poor core, with a thickness of approximately 500 nm.

[0162] In this embodiment, the phosphate-based cathode material is Fe. 0.4 Mn 0.6 The preparation method of PO4·0.25Li5FeO4 includes the following steps:

[0163] S1.Fe 0.4 Mn 0.6 Preparation of lithium-poor phase of PO4: Iron source, manganese source and phosphate were prepared and mixed evenly according to stoichiometric ratio, and a precipitant was added for co-precipitation to obtain Fe. 0.4 Mn 0.6 PO4 precursor, heat treatment to obtain Fe 0.4 Mn 0.6 PO4 lithium-poor phase;

[0164] S2. Preparation of composite cathode material precursor: combining nanoscale iron source with Fe... 0.4 Mn 0.6 The PO4 lithium-depleted phase was prepared according to stoichiometric ratio and mixed by high-energy ball milling, so that the nano-iron source was uniformly attached to the Fe. 0.4 Mn 0.6The lithium-poor phase surface of PO4 was then subjected to medium-low temperature heat treatment to stabilize the structure and obtain the precursor of composite cathode material.

[0165] S3. Composite treatment and heat treatment of lithium-poor and lithium-rich phases: The composite cathode material precursor and lithium source are prepared according to the stoichiometric ratio of the lithium-rich phase. The solid phase is mixed uniformly by high-energy ball milling, and then sintered at 500℃. The lithium source melts and fuses with the nano-iron source, and the reaction generates a dense lithium-rich phase that coats the interface of the lithium-poor phase, ultimately forming a core-shell structure of lithium-rich phase coating the lithium-poor phase. 0.4 Mn 0.6 PO4·0.25Li5FeO4 composite cathode material.

[0166] Example 6

[0167] This embodiment provides a negative electrode-free lithium battery. The structure of this negative electrode-free lithium battery before charging and discharging is the same as that of the negative electrode-free lithium battery in Embodiment 1, the difference being that the composite positive electrode material is a phosphate-based positive electrode material, Li. 0.5 FePO4·0.25Li5FeO4.

[0168] Among them, the positive electrode contains phosphate-based positive electrode material Li 0.5 In FePO4·0.25Li5FeO4, Li5FeO4 is a lithium-rich phase and forms the lithium-rich core, with a particle size D. 50 Approximately 3 μm; Li 0.5 FePO4 is a lithium-poor phase, forming a lithium-poor coating layer that coats the lithium-rich core. The lithium concentration exhibits a gradient, with a relatively high lithium concentration in the inner layer and a relatively low lithium concentration in the outer layer, with a thickness of approximately 3 μm.

[0169] The preparation method of the composite cathode material in this embodiment includes the following steps:

[0170] Preparation of Li5FeO4 lithium-rich phase: Iron source and lithium source were mixed evenly according to stoichiometric ratio, solvent was evaporated to obtain precursor, additional lithium source was added appropriately and ball-milled evenly with precursor, and high-temperature solid-state sintering was performed to obtain Li5FeO4 lithium-rich phase.

[0171] S2. Preparation of lithium-poor FePO4 precursor: Iron source and phosphate were mixed evenly according to stoichiometric ratio, and a precipitant was added for co-precipitation to obtain nano FePO4 precursor;

[0172] S3. Composite treatment and heat treatment of lithium-poor and lithium-rich phases: Combining large-particle Li5FeO4 lithium-rich phase with nano-Li 0.5The lithium source required for the lithium-poor FePO4 phase is prepared according to stoichiometric ratio and mixed uniformly by high-energy ball milling to form a mixed phase of lithium-rich Li5FeO4 and lithium source. Then, nano-FePO4 precursor is added according to stoichiometric ratio and mixed uniformly by high-energy ball milling to form a mixed structure of lithium-rich phase / lithium source / lithium-poor phase from the inside out. Finally, sintering at 700℃ allows the nano-FePO4 lithium-poor phase precursor structure to fuse and form a highly crystalline nano-FePO4 lithium-poor phase. Simultaneously, due to concentration polarization, the lithium source permeates outward and partially intercalates with the nano-FePO4 lithium-poor phase, creating a gradient change in lithium concentration. Ultimately, a core-shell structure is formed where the lithium-poor phase with a lithium concentration gradient encapsulates the lithium-rich phase. 0.5 FePO4·0.25Li5FeO4 composite cathode material.

[0173] Example 7

[0174] This embodiment provides a negative electrode-free lithium battery. The structure of this negative electrode-free lithium battery before charging and discharging is the same as that of the negative electrode-free lithium battery in Embodiment 2, the difference being that the composite positive electrode material is a phosphate-based positive electrode material, Li. 0.5 FePO4·0.25Li5FeO4;

[0175] Furthermore, in this embodiment, the positive electrode contains a phosphate-based positive electrode material, Li. 0.5 FePO4·0.25Li5FeO4 was prepared according to the preparation method of FePO4·0.5Li5FeO4, a phosphate-based cathode material, in Example 2 to form a core-shell structured Li. 0.5 FePO4·0.25Li5FeO4, wherein Li 0.5 FePO4·0.25Li5FeO4, wherein Li5FeO4 is a lithium-rich phase, and the particle size D 50 Approximately 3 μm; Li 0.5 FePO4 is a lithium-poor phase, forming a lithium-poor coating layer that coats the lithium-rich core, with a thickness of approximately 3 μm.

[0176] Example 8

[0177] This embodiment provides a negative electrode-free lithium battery. The structure of this negative electrode-free lithium battery before charging and discharging is the same as that of the negative electrode-free lithium battery in Embodiment 3, the difference being that the composite positive electrode material is a phosphate-based positive electrode material, FePO4·0.25Li5FeO4.

[0178] The phosphate-based cathode material FePO4·0.25Li5FeO4 contained in the cathode sheet was prepared as garnet-shaped FePO4·0.25Li5FeO4 according to the preparation method of FePO4·0.5Li5FeO4 in Example 1. The lithium-depleted FePO4 phase consists of porous, large particles with a particle size D. 50The particle size is approximately 6 μm, with an average pore size of approximately 300 nm; the lithium-rich Li5FeO4 phase consists of small particles with a particle size D. 50 Approximately 200 nm; Li5FeO4 fills the FePO4 porous structure.

[0179] Example 9

[0180] This embodiment provides a negative electrode-free lithium battery. The structure of this negative electrode-free lithium battery before charging and discharging is the same as that of the negative electrode-free lithium battery in Embodiment 1, except that the negative electrode current collector is a 10μm thick smooth copper foil with a surface roughness R. a It is approximately 1 μm.

[0181] Example 10

[0182] This embodiment provides a negative electrode-free lithium battery. The structure of this negative electrode-free lithium battery before charging and discharging is the same as that of the negative electrode-free lithium battery in Embodiment 1, except that the negative electrode current collector is a 10μm thick rough copper foil with a surface roughness R. a It is approximately 2μm.

[0183] Example 11

[0184] This embodiment provides a negative electrode-free lithium battery. The structure of this negative electrode-free lithium battery before charging and discharging is the same as that of the negative electrode-free lithium battery in Embodiment 1, except that the negative electrode current collector is a 10μm thick carbon paper with a surface roughness R. a It is approximately 8μm.

[0185] Comparative Example 1

[0186] This comparative example provides a lithium battery comprising a positive electrode and a negative electrode disposed opposite to each other, with a liquid electrolyte and a separator disposed between the positive electrode and the negative electrode current collector. The positive electrode comprises an aluminum foil with a thickness of 20 μm and a positive electrode material layer bonded to the surface of the aluminum foil, the positive electrode material layer being lithium iron phosphate with a thickness of 90 μm. The negative electrode comprises a copper foil with a thickness of 10 μm and a negative electrode material layer bonded to the surface of the copper foil, the negative electrode material layer being a commercial graphite negative electrode with a thickness of 100 μm. The separator is a PE film with a thickness of 10 μm, and the electrolyte is 1M LiPF6.

[0187] Lithium battery performance testing

[0188] The negative electrode-free batteries provided in Examples 1 to 8 and the lithium-ion batteries provided in the comparative examples were subjected to performance tests according to the following test indicators and test methods:

[0189] (1) Electrochemical performance testing of lithium-ion batteries

[0190] The lithium batteries provided in Examples 1 to 11 and the lithium-ion batteries provided in the comparative examples were tested for their charge and discharge capacity performance according to the following method: constant current and constant voltage charging at a rate of 0.05C to 4.3V, with a cutoff current of 0.02C; resting for 5 minutes, constant current discharging at a rate of 0.05C to 2.8V, and then resting for another 5 minutes; 50 charge and discharge cycles.

[0191] (2) Cell thickness test

[0192] The thickness of the lithium batteries provided in Examples 1 to 11 and the lithium-ion batteries provided in the comparative examples was tested from the positive electrode current collector to the negative electrode current collector.

[0193] Test results:

[0194] The battery structures obtained after charging in Examples 1 to 3 are as follows: Figure 4 China B map Figure 5 China B map Figure 6 As shown in Figure B. This is attributed to the fact that lithium ions are released from the positive electrode material, including reversible and irreversible lithium ions, with some irreversible lithium ions migrating to the negative electrode current collector to form lithium metal.

[0195] The relevant test data for each embodiment are shown in Table 1 below.

[0196] Table 1

[0197]

[0198] As shown in Table 1, the composite cathode materials in Examples 1 to 8, due to the presence of sufficient surplus lithium ions, enable the assembly of electrodeless battery cells, reducing the thickness of the negative electrode sheet in the cell system and significantly decreasing the overall cell thickness, resulting in a substantial reduction in cell volume. Although the introduction of this irreversible capacity of the lithium-rich composite cathode leads to a decrease in the overall cycle reversible specific capacity of the composite cathode material, the emergence of this composite cathode material makes electrodeless batteries possible, thereby significantly improving the overall volumetric energy density of the cell. This enables the controllable and safe application of lithium metal batteries and facilitates the promotion of high volumetric energy density electrodeless lithium batteries.

[0199] Meanwhile, in electrodeless batteries, the solid electrolyte layer is thicker than the separator, resulting in a significant increase in the cell thickness of solid / semi-solid electrodeless batteries compared to liquid electrolyte systems. Furthermore, the interfacial contact between the solid electrolyte and the positive electrode is not as close as that of the liquid electrolyte, slightly affecting the charge-discharge performance of the composite positive electrode material, and causing a slight decrease in the cell volumetric energy density compared to liquid electrolyte electrodeless battery systems. However, overall, compared to existing commercial battery systems, the volumetric energy density of liquid, semi-solid, and solid electrodeless battery cells assembled using lithium-rich composite positive electrode materials is still significantly improved, which has a positive effect on the application of high volumetric energy density batteries.

[0200] Further cycle tests were conducted on the batteries in the above embodiments. The capacity retention rates of the batteries selected from Embodiments 1, 9 to 11 are shown in Table 2 below:

[0201] Table 2

[0202]

[0203] As shown in Table 2, the battery capacity retention rates of Examples 1 and 9-11 differed after 50 cycles. This indicates that changes in the surface roughness of the negative electrode current collector affect the interaction force between the current collector and the deposited lithium metal layer, thus indirectly affecting the battery's cycle performance. Relatively large surface roughness increases the adhesion between the negative electrode current collector and the lithium metal layer, thereby improving the cycle performance and stability of the negative electrode-less lithium battery. If the surface roughness of the negative electrode current collector is too small, the adhesion is weak, and the lithium metal layer is more likely to detach and form dead lithium during charge-discharge cycles. If the surface roughness of the negative electrode current collector is too large, although the adhesion increases, the rough surface makes it difficult for the lithium metal layer to flatten, making it more prone to lithium dendrite formation, which harms the battery system.

[0204] The above are merely preferred embodiments of this application and are not intended to limit this application. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. A lithium battery, comprising a positive electrode sheet, said positive electrode sheet having a positive electrode active layer, characterized in that: It also includes a negative electrode current collector, which is positioned opposite and spaced apart from the positive electrode active layer. Before charging and discharging after assembly, the negative electrode current collector does not contain any negative electrode material. The positive electrode material contained in the positive electrode active layer includes a composite positive electrode material, which includes a lithium-poor phase as the positive electrode material and a lithium-rich phase for lithium replenishment. The lithium-rich phase and the lithium-poor phase form a composite material. During charging and discharging, the lithium-rich phase migrates at least to the negative electrode current collector and forms a lithium-rich film layer on the surface of the negative electrode current collector. The lithium-rich film layer includes a lithium metal layer. In the composite positive electrode material, the lithium-poor phase is a phosphate-based positive electrode material with a porous structure, and the lithium-rich phase fills the porous structure of the lithium-poor phase. The lithium-poor phase includes a phosphate-based cathode material Li (1 x) A y B (1 y) PO4, where A is selected from at least one of the metal elements Fe, Co, Ni, Mn, and B is selected from at least one of the metal elements Fe, Co, Ni, Mn, V, Mg, Ca, Cr, Cu, Zn, Ti, Sn; the values of x and y satisfy: x = 1, 0 < y ≤ 1; the lithium-rich phase includes at least one of lithium-rich metal oxide materials Li5MO4, Li2MO2, Li6MO4, Li8MO6, where M can be selected from at least one of the metal elements Fe, Co, Ni, Mn, Al, Cr, Ga, In, La, Bi.

2. The lithium battery as described in claim 1, characterized in that: The thickness of the lithium-rich film is 5nm-100μm.

3. The lithium battery as described in claim 1, characterized in that: The composite cathode material has a mass content of 50%-99% in the cathode active layer; and / or The positive electrode active layer also includes a conductive agent and a binder.

4. The lithium battery according to any one of claims 1-3, characterized in that: It also includes a separator, which is stacked between the negative electrode current collector and the positive electrode active layer, and forms a battery cell with the negative electrode current collector and the positive electrode active layer. The battery cell is wetted with a first liquid electrolyte, and the lithium-rich film layer is formed on the surface of the negative electrode current collector near the separator.

5. The lithium battery according to any one of claims 1-3, characterized in that: It also includes a solid electrolyte layer, which is stacked between the negative electrode current collector and the positive electrode active layer, and the lithium-rich film layer is formed on the surface of the negative electrode current collector near the solid electrolyte layer.

6. The lithium battery as described in claim 5, characterized in that: It also includes a second liquid electrolyte, which wets the solid electrolyte layer, the negative electrode current collector, and the positive electrode active layer, wherein the lithium-rich film layer is formed on the surface of the negative electrode current collector near the solid electrolyte layer; and / or The thickness of the solid electrolyte layer is 1μm-200μm: and / or The solid electrolyte in the solid electrolyte layer is at least one of polymer-based lithium salt electrolyte, oxide-based electrolyte, and sulfide-based electrolyte.

7. The lithium battery according to any one of claims 1-3 and 6, characterized in that: The material of the negative electrode current collector includes one of the following: copper foil, carbon-coated copper foil, composite copper foil, copper mesh, copper foam, carbon paper, carbon cloth, etc.

8. The lithium battery according to any one of claims 1-3 and 6, characterized in that: The thickness of the negative electrode current collector is 1~30μm.

9. The lithium battery according to any one of claims 1-3 and 6, characterized in that: The surface roughness R of the negative electrode current collector a The range is 0.5-20 μm.

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