Composite negative electrode and battery

Abstract

The embodiment of the invention provides a composite negative electrode and a battery, the composite negative electrode comprises a three-dimensional conductive skeleton layer, a solid-state lithium source layer and a liquid-state lithium solution distributed in the three-dimensional conductive skeleton layer, and the solid-state lithium source layer comprises a solid-state lithium source. The composite negative electrode is a solid-liquid mixed composite negative electrode, simultaneously comprises a solid-state lithium source and a liquid-state lithium solution, can form good contact with a solid-state electrolyte, has good lithium dissolving capacity, and can effectively inhibit nucleation and growth of lithium dendrites and improve cycle performance.

Description

Technical Field

[0001] This application relates to the field of battery technology, and in particular to a composite negative electrode and a battery. Background Technology

[0002] Traditional commercial lithium-ion batteries mostly use liquid electrolytes, which face a bottleneck in energy density (up to 350 Wh / kg) and pose safety hazards such as high-temperature thermal runaway. Solid-state electrolytes (SSEs) offer advantages such as high thermal stability, non-flammability, leak-proofness, and non-volatility, which are beneficial for improving battery safety and stability. However, recent research indicates that the high mechanical strength of SSEs cannot effectively suppress lithium dendrite formation. When using metallic lithium or Li-Si alloy anodes, lithium dendrites can still form in the SSE, leading to problems such as high interfacial impedance, short cycle life, and low critical current density in all-solid-state batteries. Furthermore, the solid-solid contact between the SSE and the solid electrode continuously deteriorates, resulting in persistently worsened interfacial stability, further hindering the practical application of all-solid-state batteries.

[0003] To address these issues, researchers have improved solid-solid contact and suppressed lithium dendrite diffusion in the electrolyte by optimizing the solid electrolyte composition and forming artificial electrolyte layers at the interface. However, based on current battery structures, interfacial instability between the solid electrolyte and solid electrode remains, making it difficult to fundamentally solve this problem. Summary of the Invention

[0004] In view of this, embodiments of this application provide a composite negative electrode and a battery. The composite negative electrode is a solid-liquid hybrid composite negative electrode, which includes both a solid lithium source and a liquid lithium solution. The composite negative electrode can form good contact with the solid electrolyte, has good lithium dissolving ability, can effectively suppress the nucleation and growth of lithium dendrites, and improve cycle performance.

[0005] In a first aspect, embodiments of this application provide a composite negative electrode, the composite negative electrode comprising a three-dimensional conductive framework layer and a solid lithium source layer, and a liquid lithium solution distributed in the three-dimensional conductive framework layer, the solid lithium source layer comprising a solid lithium source.

[0006] The composite anode provided in this application is a solid-liquid hybrid composite anode or a semi-solid composite anode, which simultaneously includes a solid lithium source and a liquid lithium solution. This composite anode can form good contact with the solid electrolyte and has good lithium-solidifying ability, which can fundamentally and effectively suppress the nucleation and growth of lithium dendrites and improve cycle performance. Compared with traditional all-solid-state batteries, this composite anode, through the introduction of liquid lithium solution, can improve the problems of poor contact and interface instability between the solid electrolyte and the solid anode, and suppress the nucleation and growth of lithium dendrites. Specifically, the liquid lithium solution can fully contact the solid lithium source and the solid electrolyte to achieve uniform and rapid Li-liquid hydrolysis.+ The conductive properties of the liquid lithium solution make it difficult for lithium dendrites to nucleate and grow in this composite anode. Furthermore, the liquid lithium solution has lithium-dissolving capabilities, which can dissolve lithium dendrites to a certain extent, further reducing their formation. Compared to liquid anodes, this composite anode is a non-flowing solid, solving the problem of limited battery models caused by the fluidity of liquid anodes. This composite anode can be applied to coin cells, pouch cells, and other lithium-ion batteries with more mature technology and higher energy density.

[0007] In this embodiment of the application, the liquid lithium solution is a mixed liquid system of lithium-containing ether solvent and polycyclic aromatic hydrocarbons or their derivatives.

[0008] In this embodiment, the liquid lithium solution is prepared by mixing metallic lithium, polycyclic aromatic hydrocarbons (PAHs) or their derivatives, and an ether solvent. This mixing can be carried out at room temperature. After mixing metallic lithium with PAHs or their derivatives and the ether solvent, the metallic lithium rapidly dissolves into the mixture formed by the PAHs or their derivatives and the ether solvent, resulting in intermolecular interactions among the three components. This liquid lithium solution can provide a liquid lithium source for the composite anode, achieving sufficient contact with the solid lithium source and solid electrolyte, improving the contact between the anode and the solid electrolyte, and achieving uniform and rapid Li-ionization. + The conductivity makes it difficult for lithium dendrites to nucleate and grow in the composite negative electrode, thus improving the stability of the interface between the negative electrode and the solid electrolyte. The liquid lithium solution has good electronic and ionic conductivity, and it can dissolve lithium dendrites even in an unsaturated state. Therefore, it can reduce the problems of high interface impedance, short cycle life and low critical current density caused by lithium dendrites.

[0009] In the embodiments of this application, the polycyclic aromatic hydrocarbons or their derivatives include one or more of biphenyl compounds or their derivatives, naphthalene or its derivatives, anthracene or its derivatives, and phenanthrene or its derivatives;

[0010] The ether solvents include one or more of the following: diethyl ether, methyl ether, diethylene glycol dimethyl ether (DEM), diethylene glycol dimethyl ether (DEGDEM), triethylene glycol dimethyl ether, tetraethylene glycol dimethyl ether (TEGDEM), polyethylene glycol dimethyl ether, tetrahydrofuran, 1,3-dioxocyclopentane, dipropyl ether, diisopropyl ether, ethyl butyl ether, dibutyl ether, dipentane ether, diisopentane ether, dihexyl ether, 2-methyltetrahydrofuran, 4-methyl-1,3-dioxocyclopentane, dimethoxymethane, 1,2-dimethoxypropane, dioxopentane, 1,4-dioxane, ethylene oxide, propylene oxide, and 1,1-diethoxyethane.

[0011] In this embodiment, the total conductivity of the liquid lithium solution is not less than 1 mS / cm. The total conductivity of the liquid lithium solution includes ionic conductivity and electronic conductivity. The high conductivity of the liquid lithium solution is beneficial for improving the electron conduction and ion transport capabilities of the negative electrode, thereby enhancing the electrochemical performance of the composite negative electrode. The total conductivity of the liquid lithium solution can be obtained by obtaining the resistance from the electrochemical impedance spectroscopy of the liquid lithium solution and calculating the total conductivity using the conductivity formula σ = k / R.

[0012] In this embodiment of the application, the molar concentration of lithium in the liquid lithium solution is ≥0.5 mol / L. A suitable molar concentration of lithium is beneficial for obtaining a relatively low redox potential and improving the battery energy density.

[0013] In this embodiment, the solid lithium source is also distributed within the three-dimensional conductive framework layer. The simultaneous inclusion of a liquid lithium solution and a solid lithium source in the three-dimensional conductive framework layer facilitates good contact between the liquid lithium solution and the solid lithium source.

[0014] In this embodiment, the solid lithium source is distributed in the three-dimensional conductive framework layer at least on the side closest to the solid lithium source layer. This structure helps to improve the adhesion of the solid lithium source layer to the three-dimensional conductive framework layer and enhances the overall structural stability of the composite anode.

[0015] In this embodiment, the content of the solid lithium source in the three-dimensional conductive framework layer gradually decreases from the direction closest to the solid lithium source layer to the direction furthest away from it. This design is beneficial for both the bonding of the solid lithium source layer and for better adsorption of liquid lithium solution.

[0016] In this embodiment of the application, in the composite negative electrode, the mass of lithium in the liquid lithium solution accounts for less than 5% of the total lithium mass in the solid lithium source and the liquid lithium solution. Controlling the total content of the liquid lithium source within a certain range is beneficial for better balancing electrochemical performance and energy density.

[0017] In this embodiment, the solid lithium source includes metallic lithium and / or lithium alloys. The lithium alloy can be any alloy that can serve as the negative electrode of a lithium battery, including but not limited to lithium-silicon alloys.

[0018] In this embodiment, the three-dimensional conductive framework layer includes nickel foam, copper foam, carbon felt, or a porous carbon layer. Using the aforementioned three-dimensional conductive framework to construct a composite anode not only effectively supports solid lithium sources and liquid lithium solutions, but also reduces costs, lightens the overall weight of the anode, and increases energy density. Furthermore, its porous structure provides deposition space for lithium, mitigating volume changes during charging and discharging and improving the structural stability of the anode.

[0019] A second aspect of this application provides a method for preparing a composite negative electrode, comprising:

[0020] A solid lithium source is placed on a three-dimensional conductive framework layer, and pressure is applied to make the solid lithium source adhere to the three-dimensional conductive framework layer.

[0021] Liquid lithium solution is added dropwise to allow it to penetrate into the three-dimensional conductive framework layer.

[0022] The preparation method of this composite anode is simple, easy to operate, and conducive to industrial production.

[0023] A third aspect of this application provides a battery, including a solid positive electrode, a composite negative electrode as described in the first aspect, and a solid electrolyte layer disposed between the solid positive electrode and the composite negative electrode. The solid lithium source layer side of the composite negative electrode is disposed close to the solid electrolyte layer. This battery, using the composite negative electrode provided in this application, is a quasi-solid-state battery. This battery can improve the problem of poor contact between the negative electrode and the solid electrolyte in traditional all-solid-state batteries, effectively suppressing lithium dendrite growth and improving the battery's long-cycle performance. This battery can be assembled in the form of button cells or pouch cells, making it easy to industrialize.

[0024] In this embodiment, the solid electrolyte layer includes an inorganic solid electrolyte layer or a composite solid electrolyte layer; the inorganic solid electrolyte layer includes an inorganic solid electrolyte, and the composite solid electrolyte layer includes an inorganic solid electrolyte, a polymer electrolyte, and / or a gel electrolyte. Using an inorganic solid electrolyte combined with a polymer electrolyte and / or a gel electrolyte to form a composite solid electrolyte layer helps to balance the advantages of each type of electrolyte, enabling the battery to operate better at room temperature and pressure, thus improving battery performance; it also improves the contact between the composite negative electrode and the solid electrolyte layer, and improves the contact between the solid positive electrode and the solid electrolyte layer, further enhancing battery performance.

[0025] In one embodiment of this application, the inorganic solid electrolyte is mixed and distributed with the polymer electrolyte and / or gel electrolyte in the composite solid electrolyte layer. This composite solid electrolyte layer possesses both high flexibility and density, is chemically stable to the composite negative electrode, and can achieve sufficient and stable contact with the solid positive and negative electrodes.

[0026] In another embodiment of this application, the composite solid electrolyte layer includes an inorganic layer and an organic layer stacked on one or both sides of the inorganic layer. The organic layer includes a polymer electrolyte layer or a gel electrolyte layer. The inorganic layer includes the inorganic solid electrolyte, the polymer electrolyte layer includes the polymer electrolyte, and the gel electrolyte layer includes the gel electrolyte. Introducing an ultrathin organic layer onto the inorganic layer allows the solid electrolyte layer to possess both excellent ionic conductivity and density, preventing the liquid components in the composite negative electrode from seeping into the solid electrolyte and causing potential side reactions.

[0027] In one embodiment of this application, the composite solid electrolyte layer includes an inorganic layer and a polymer electrolyte layer stacked on both sides of the inorganic layer; or

[0028] The composite solid electrolyte layer includes an inorganic layer, a polymer electrolyte layer stacked on the inorganic layer near the composite negative electrode, and a gel electrolyte layer stacked on the inorganic layer near the solid positive electrode.

[0029] In this embodiment of the application, the total mass percentage of polymer electrolyte and gel electrolyte in the composite solid electrolyte layer is 1%-50%. In this embodiment of the application, the mass percentage of inorganic solid electrolyte in the composite solid electrolyte layer is 50%-99%. Controlling the content of inorganic solid electrolyte in the composite solid electrolyte layer to a relatively higher percentage is beneficial to achieving higher room temperature conductivity of the solid electrolyte layer and improving the room temperature operation performance of the battery.

[0030] In this embodiment of the application, the inorganic solid electrolyte includes one or more of the following: oxidized solid electrolyte, sulfide solid electrolyte, and halide solid electrolyte;

[0031] The polymer electrolyte comprises a polymer material and a lithium salt; the gel electrolyte uses a polymer monomer and a lithium salt.

[0032] The polymer material includes one or more of polyethylene oxide (PEO), polypropylene oxide (PPO), polymethyl methacrylate (PMMA), polyacrylonitrile (PAN), and polyvinylidene fluoride (PVDF); the polymer monomer includes one or more of 1,3-dioxolane (DOL), 1,4-dioxane, fluoroethylene carbonate (FEC), and methyl methacrylate (MMA); the lithium salt includes one or more of lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), lithium bis(fluorosulfonyl)imide (LiFSI), lithium trifluoromethanesulfonate (LiOTf), lithium hexafluorophosphate (LiPF6), lithium tetrafluoroborate (LiBF4), and lithium perchlorate (LiClO4).

[0033] In this embodiment, the liquid lithium solution accounts for less than 5% of the total mass of the battery. Controlling the total liquid lithium solution content in the battery within a suitable range is beneficial for improving relevant performance using the liquid lithium solution, while also facilitating better process assembly and taking into account other performance aspects such as battery energy density.

[0034] This application also provides an electrical device, which includes the battery described in the third aspect. Attached Figure Description

[0035] Figure 1 This is a schematic diagram of the cross-sectional structure of the composite negative electrode 100 provided in the embodiments of this application;

[0036] Figure 2 This is a flowchart illustrating a method for preparing a composite negative electrode according to an embodiment of this application;

[0037] Figure 3 This is a schematic diagram of the preparation process of a composite negative electrode provided in an embodiment of this application;

[0038] Figure 4 A schematic diagram of the cross-sectional structure of a battery 200 provided in one embodiment of this application;

[0039] Figure 5 A schematic diagram of the cross-sectional structure of a battery 200 provided for another embodiment of this application;

[0040] Figure 6 This is a schematic diagram of the structure of an electrical device 300 provided in an embodiment of this application;

[0041] Figure 7 The charge-discharge cycle curve of the symmetrical battery in Embodiment 1 of this application;

[0042] Figure 8A and Figure 8B The limiting current density test curve of the symmetrical battery in Embodiment 2 of this application;

[0043] Figure 9 The charge-discharge cycle curve of the symmetrical battery in Embodiment 3 of this application;

[0044] Figure 10 The results of charge-discharge cycles of the full battery in Example 4 of this application;

[0045] Figure 11 The results of charge-discharge cycles of the full battery in Example 5 of this application are shown. Detailed Implementation

[0046] The embodiments of this application will now be described in conjunction with the accompanying drawings.

[0047] The high mechanical strength of solid-state electrolytes cannot effectively suppress lithium dendrites, leading to problems such as high interfacial impedance, short cycle life, and low critical current density in all-solid-state batteries. Furthermore, during charge-discharge cycles, the solid-solid contact between the solid electrolyte and the solid positive and negative electrodes continuously deteriorates, resulting in persistently worse interfacial stability. To address these issues, researchers have improved the solid-solid contact and suppressed lithium dendrite diffusion in the electrolyte by optimizing the solid electrolyte composition and forming artificial electrolyte layers at the interface. However, based on current solid-state battery structures, interfacial instability between the solid electrolyte and the solid positive and negative electrodes remains, making it difficult to fundamentally solve this problem. Therefore, this application provides a composite negative electrode, a solid-liquid hybrid composite negative electrode comprising both a solid lithium source and a liquid lithium solution. This composite negative electrode can form good contact with the solid electrolyte, exhibits excellent lithium dissolution capability, effectively suppresses lithium dendrite nucleation and growth, and improves cycle performance.

[0048] See Figure 1 , Figure 1 This is a schematic cross-sectional view of the composite negative electrode 100 provided in an embodiment of this application. The composite negative electrode 100 includes a three-dimensional conductive framework layer 10 and a solid lithium source layer 20 stacked together, and a liquid lithium solution 40 distributed in the three-dimensional conductive framework layer 10. The solid lithium source layer 20 includes a solid lithium source. In some embodiments, the composite negative electrode 100 further includes a solid lithium source 30 distributed in the three-dimensional conductive framework layer 10. It should be noted that... Figure 1 The structures of the three-dimensional conductive framework layer 10, the solid lithium source 30, and the liquid lithium solution 40 are schematic diagrams and do not limit the actual product structure of this application. In actual products, the three-dimensional conductive framework layer 10 may not be a regular network structure, the solid lithium source 30 may not be a regular particle structure, and the liquid lithium solution 40 may not be a regular droplet shape.

[0049] The composite anode 100 provided in this application embodiment is a solid-liquid hybrid composite anode or a semi-solid composite anode, which simultaneously includes a solid lithium source and a liquid lithium solution. This composite anode can form good contact with the solid electrolyte and has good lithium dissolving ability, which can fundamentally and effectively suppress the nucleation and growth of lithium dendrites and improve cycle performance. Compared with traditional all-solid-state batteries, this composite anode, through the introduction of liquid lithium solution, can improve the problems of poor contact and interface instability between the solid electrolyte and the solid anode, and suppress the nucleation and growth of lithium dendrites. Specifically, the liquid lithium solution can fully contact the solid lithium source and the solid electrolyte to achieve uniform and rapid Li-liquid dissolution. +The conductive properties of the liquid lithium solution make it difficult for lithium dendrites to nucleate and grow in this composite anode. Furthermore, the liquid lithium solution has lithium-dissolving capabilities, which can dissolve lithium dendrites to a certain extent, further reducing their formation. Compared to liquid anodes, this composite anode is a non-flowing solid, solving the problem of limited battery models caused by the fluidity of liquid anodes. This composite anode can be applied to coin cells, pouch cells, and other lithium-ion batteries with more mature technology and higher energy density.

[0050] In this application, the three-dimensional conductive framework layer 10 serves as the negative electrode current collector, providing mechanical support, loading a solid lithium source 30, and adsorbing a liquid lithium solution 40. The three-dimensional conductive framework layer 10 forms a three-dimensional network structure with a porous structure. The solid lithium source 30 and liquid lithium solution 40 can be embedded in the porous structure and adsorbed onto the three-dimensional conductive framework. In this application, the three-dimensional conductive framework layer 10 can be any conductive material with good conductivity, a three-dimensional porous structure, and capable of serving as a negative electrode current collector, including but not limited to nickel foam, copper foam, carbon felt, or porous carbon layers. Using a three-dimensional conductive framework to construct the composite negative electrode 100 not only effectively loads the solid lithium source 30 and liquid lithium solution 40, but also reduces costs, lightens the total weight of the negative electrode, and increases energy density. Its porous structure also provides deposition space for lithium, mitigating volume changes during charging and discharging and improving the structural stability of the negative electrode. In this application, the porous structure in the three-dimensional conductive framework layer 10 can have nanometer-scale, micrometer-scale, or millimeter-scale pore sizes.

[0051] In this embodiment, the liquid lithium solution is a mixed liquid system of lithium-containing ether solvent and polycyclic aromatic hydrocarbons (PAHs) or their derivatives. Specifically, the liquid lithium solution can be prepared by mixing metallic lithium, PAHs or their derivatives, and an ether solvent. That is, metallic lithium is dissolved in the mixed liquid system formed by PAHs or their derivatives and the ether solvent, and this mixing can be completed at room temperature. After mixing metallic lithium with PAHs or their derivatives and the ether solvent, the metallic lithium rapidly dissolves into the mixed system, forming intermolecular interactions among the three components. This liquid lithium solution can provide a liquid lithium source for the composite anode, achieving sufficient contact with the solid lithium source and solid electrolyte, improving the contact between the anode and the solid electrolyte, and achieving uniform and rapid Li-ionization. + The conductivity makes it difficult for lithium dendrites to nucleate and grow in the composite negative electrode, thus improving the stability of the interface between the negative electrode and the solid electrolyte. The liquid lithium solution has good electronic and ionic conductivity and can also dissolve lithium dendrites, thereby reducing the problems of high interface impedance, short cycle life and low critical current density caused by lithium dendrites.

[0052] In this application, the polycyclic aromatic hydrocarbon or its derivative may be one or more of the following: biphenyl compounds or their derivatives, naphthalene or its derivatives, anthracene or its derivatives, and phenanthrene or its derivatives. The biphenyl compounds may be diphenyl, terphenyl, or tetraphenyl, etc.

[0053] In the embodiments of this application, the ether solvent may be one or more of the following: diethyl ether, methyl ether, ethylene glycol dimethyl ether, diethylene glycol dimethyl ether, triethylene glycol dimethyl ether, tetraethylene glycol dimethyl ether, polyethylene glycol dimethyl ether, tetrahydrofuran, 1,3-dioxocyclopentane, dipropyl ether, diisopropyl ether, ethyl butyl ether, dibutyl ether, dipentane ether, diisopentane ether, dihexyl ether, 2-methyltetrahydrofuran, 4-methyl-1,3-dioxocyclopentane, dimethoxymethane, 1,2-dimethoxypropane, dioxopentane, 1,4-dioxane, ethylene oxide, propylene oxide, and 1,1-diethoxyethane.

[0054] Taking phenanthrene and dimethyl ethylene glycol (DME) as examples, the interaction mechanism between the components in a liquid lithium solution is as follows: Charge transfer first occurs between Li and Phen, forming [(Phen· - Li + The adduct is further stabilized by the coordination of lithium ions with DME, ultimately forming the adduct [(Phen· - Li + (DME).

[0055] In this embodiment, the total conductivity of the liquid lithium solution is not less than 1 mS / cm, that is, the total conductivity of the liquid lithium solution is greater than or equal to 1 mS / cm. The total conductivity of the liquid lithium solution includes ionic conductivity and electronic conductivity. The high conductivity of the liquid lithium solution is beneficial for improving the electron conduction and ion transport capabilities of the negative electrode, thereby enhancing the electrochemical performance of the composite negative electrode. In some embodiments, the total conductivity of the liquid lithium solution is 1 mS / cm-20 mS / cm. In some embodiments, the total conductivity of the liquid lithium solution is, for example, 1 mS / cm, 3 mS / cm, 5 mS / cm, 6 mS / cm, 7 mS / cm, 9 mS / cm, 10 mS / cm, 12 mS / cm, 15 mS / cm, 18 mS / cm, or 20 mS / cm. The total conductivity of a liquid lithium solution can be obtained by measuring the resistance R of the liquid lithium solution through an electrochemical impedance spectroscopy of a selected conductivity electrode, and then calculating the total conductivity of the liquid lithium solution using the conductivity formula σ = k / R, where k is the conductivity constant of the corresponding electrode.

[0056] In this embodiment, the liquid lithium solution can be a saturated or unsaturated solution, and the molar concentration of lithium in the liquid lithium solution is ≥0.5 mol / L. A suitable lithium molar concentration is beneficial for obtaining a relatively low redox potential and improving the battery energy density. In some embodiments, the molar concentration of lithium in the liquid lithium solution is 0.5 mol / L-5.0 mol / L. Exemplarily, the molar concentration of lithium in the liquid lithium solution is 0.5 mol / L, 1 mol / L, 1.5 mol / L, 2 mol / L, 2.5 mol / L, 3 mol / L, 3.5 mol / L, 4 mol / L, 4.5 mol / L, and 5.0 mol / L.

[0057] In this embodiment, the liquid lithium solution 40 can be uniformly distributed in the three-dimensional conductive framework layer 10. Uniform distribution of the liquid lithium solution is beneficial to improving the performance of the composite anode. In some embodiments, the content of the liquid lithium solution may gradually decrease from the direction closer to the solid lithium source layer 20 to the direction farther away from the solid lithium source layer 20; or the content of the liquid lithium solution may gradually decrease from the direction farther away from the solid lithium source layer 20 to the direction closer to the solid lithium source layer 20.

[0058] In some embodiments of this application, in the composite negative electrode 100, the mass of lithium in the liquid lithium solution accounts for less than 5% of the total mass of lithium in the solid lithium source and the liquid lithium solution; that is, based on the mass of lithium, the mass of the liquid lithium solution accounts for less than 5% of the total mass of the solid lithium source and the liquid lithium solution. Controlling the total content of the liquid lithium source within a certain range is beneficial for better balancing electrochemical performance and energy density. In some embodiments, the above percentage can be 0.1%-4.9%, exemplarily 0.1%, 0.5%, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, and 4.9%.

[0059] In this embodiment, the solid lithium source can be metallic lithium and / or a lithium alloy. The lithium alloy can be any alloy capable of serving as a negative electrode in a lithium battery, including but not limited to lithium-silicon alloys. For example, a lithium-silicon alloy can include Li... 15 Si4,Li 22 One or more of Si5.

[0060] In some embodiments of this application, the three-dimensional conductive framework layer 10 contains only liquid lithium solution 40 and no solid lithium source 30. The solid lithium source is bonded to the three-dimensional conductive framework layer 10 in the form of a solid lithium source layer 20. In this embodiment, the composite negative electrode contains both liquid lithium solution and solid lithium source, which can effectively improve the contact between the negative electrode and the electrolyte and suppress lithium dendrite growth.

[0061] In some other embodiments of this application, the three-dimensional conductive framework layer 10 includes both a liquid lithium solution 40 and a solid lithium source 30. The solid lithium source 30 in the three-dimensional conductive framework layer 10 can be formed by partially embedding a solid lithium source into the three-dimensional conductive framework layer 10 when a solid lithium source layer 20 is formed on the three-dimensional conductive framework layer 10. The three-dimensional conductive framework layer includes both a liquid lithium solution and a solid lithium source, which is beneficial to better improve the contact between the negative electrode and the solid electrolyte.

[0062] In some embodiments of this application, the three-dimensional conductive framework layer 10 has a solid lithium source 30 distributed in at least one layer structure near the solid lithium source layer 20. This structure is beneficial to improving the bonding force of the solid lithium source layer 20 to the three-dimensional conductive framework layer 10 and enhancing the overall structural stability of the composite negative electrode. In some embodiments, the distribution depth of the solid lithium source 30 in the three-dimensional conductive framework layer 10 is less than the thickness of the three-dimensional conductive framework layer 10. It can be distributed only in the surface layer near the solid lithium source layer 20. Specifically, the depth of the solid lithium source in the three-dimensional conductive framework layer 10 is 1 / 10 to 3 / 4 of the thickness of the three-dimensional conductive framework layer 10, for example, 1 / 10, 1 / 8, 1 / 6, 1 / 5, 1 / 4, 2 / 5, 1 / 2, 3 / 5, or 3 / 4. This can better ensure the stable bonding between the solid lithium source layer 20 and the three-dimensional conductive framework layer 10, while also allowing the three-dimensional conductive framework layer 10 to retain sufficient porosity to mitigate volume changes.

[0063] In some embodiments of this application, in the three-dimensional conductive framework layer 10, the content of solid lithium source gradually decreases from the direction close to the solid lithium source layer 20 to the direction away from the solid lithium source layer 20. This design is beneficial for both the bonding of the solid lithium source layer and the better adsorption of liquid lithium solution.

[0064] In this application, the solid lithium sources included in the three-dimensional conductive framework layer 10 and the solid lithium source layer 20 may be the same or different. In some embodiments, the solid lithium sources included in the three-dimensional conductive framework layer 10 and the solid lithium source layer 20 are the same. In some embodiments, the solid lithium source in the composite anode 100 includes only metallic lithium; in some embodiments, the solid lithium source in the composite anode 100 includes only lithium alloy; in some embodiments, the solid lithium source in the composite anode 100 includes both metallic lithium and lithium alloy.

[0065] In this application, the thickness of the three-dimensional conductive framework layer 10 is 1µm-5mm, for example, it can be 1µm, 50µm, 100µm, 200µm, 500µm, 800µm, 1mm, 2mm, 3mm, 4mm, or 5mm. The thickness of the solid lithium source layer 20 is 0.5µm-3µm, for example, it can be 0.5µm, 1µm, 1.5µm, 2µm, 2.5µm, or 3µm. In some embodiments, the thickness of the solid lithium source layer 20 is less than the thickness of the three-dimensional conductive framework layer 10.

[0066] The composite negative electrode provided in this application is a solid-liquid hybrid composite negative electrode, which can fundamentally suppress the nucleation and growth of lithium dendrites (solid lithium dendrites are dissolved in liquid lithium solution). In addition, the liquid lithium solution in the composite negative electrode can achieve full contact between the negative electrode and the electrolyte layer, thereby achieving stable long-term cycling.

[0067] See Figure 2 and Figure 3 , Figure 2 This is a flowchart illustrating a method for preparing a composite negative electrode according to an embodiment of this application. Figure 3 A schematic diagram illustrating the preparation process of a composite negative electrode provided in this application embodiment; the preparation method includes the following steps:

[0068] S101. Place the solid lithium source on the three-dimensional conductive framework layer and apply pressure to make the solid lithium source adhere to the three-dimensional conductive framework layer.

[0069] S102. Add liquid lithium solution dropwise to allow the liquid lithium solution to penetrate into the three-dimensional conductive framework layer.

[0070] The specific selection of the solid lithium source and liquid lithium solution involved in the above preparation method can be as described above, and will not be repeated here.

[0071] In step S101, the solid lithium source is placed on the three-dimensional conductive framework layer. This can be done by placing metallic lithium powder or lithium alloy powder on the three-dimensional conductive framework layer; or by placing metallic lithium sheets or lithium alloy sheets on the three-dimensional conductive framework layer. During the pressing process, a solid lithium source layer can be formed on the three-dimensional conductive framework layer, with a portion of the solid lithium source embedded in the three-dimensional conductive framework layer.

[0072] The preparation method of this composite anode is simple, easy to operate, and conducive to industrial production.

[0073] See Figure 4 and Figure 5 , Figure 4 This is a schematic diagram of a cross-sectional structure of a battery 200 provided in one embodiment of this application. Figure 5 This is a cross-sectional structural diagram of a battery 200 according to another embodiment of this application. The battery 200 includes a solid positive electrode 201, a composite negative electrode 100, and a solid electrolyte layer 202 disposed between the solid positive electrode 201 and the composite negative electrode 100. The solid lithium source layer 20 side of the composite negative electrode 100 is disposed close to the solid electrolyte layer 202.

[0074] The battery 200 uses the composite negative electrode 100 provided in the embodiments of this application, which is a quasi-solid-state battery. The battery 200 can improve the problem of poor contact between the negative electrode and the solid electrolyte in traditional all-solid-state batteries, effectively suppress lithium dendrite growth, and improve the long cycle performance of the battery. The battery 200 can be assembled in the form of button batteries or pouch batteries, which is easy to industrialize.

[0075] In this embodiment, the liquid lithium solution in battery 200 accounts for less than 5% of the total mass of battery 200. Controlling the total liquid lithium solution content in battery 200 within a suitable range is beneficial for improving relevant performance using the liquid lithium solution while also facilitating better process assembly and considering other performance aspects such as battery energy density. In some embodiments, the total mass of the liquid lithium solution in battery 200 accounts for 0.5%-4.9% of the total mass of battery 200. Exemplary values ​​are 0.5%, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, and 4.9%.

[0076] In this embodiment, the solid positive electrode 201 may include a positive current collector and a positive active layer disposed on the positive current collector. The positive current collector may be aluminum foil, etc., and the positive active layer includes a positive active material, which may be one or more of lithium cobalt oxide (LCO), lithium iron phosphate (LFP), ternary cathode material (NCM), lithium-rich manganese-based material (LMO), TiS2, FeS2, TiS2, S, CuS, Li2S, and MoS6. The positive active layer may also include a conductive agent and a binder. In some embodiments, the solid positive electrode 201 may be a lithium iron phosphate wet-process electrode sheet, that is, a positive electrode sheet whose positive active material is lithium iron phosphate prepared by a wet process.

[0077] In this embodiment of the application, the solid electrolyte layer 202 may include an inorganic solid electrolyte layer or a composite solid electrolyte layer; the inorganic solid electrolyte layer includes an inorganic solid electrolyte, and the composite solid electrolyte layer includes an inorganic solid electrolyte, as well as a polymer electrolyte and / or a gel electrolyte.

[0078] In this embodiment, the inorganic solid electrolyte can be one or more of the following: oxidized solid electrolyte, sulfide solid electrolyte, and halide solid electrolyte. The room temperature ionic conductivity of the inorganic solid electrolyte can be greater than 1 mS / cm.

[0079] In the embodiments of this application, the sulfide-type solid electrolyte can be selected from Li3PS4, Li 10 GeP2S 12 Li7P3S 11 Li6PS5Cl, Li 9.54 Si 1.74 P 1.44 S11.7 Cl 0.3 Li4SnS4, Li 3.85 Sn 0.85 Sb 0.15 S4, Li 3.8 Sn 0.8 As 0.2 S4, Li4Sn 0.9 Si 0.1 S4, Li 10 SnP2S 12 Li7GePS8, Li 3.25 Ge 0.25 P 0.75 S4, Li 3.25 P 0.95 S4, Li 11 Si2PS 12 Any one or more of the following: Li7P2S8I, Li8P2S9, 80(0.7Li2S·0.3P2S5)·20LiI, 95(0.8Li2S·0.2P2S5)5LiI, 56Li2S·24P2S5·20Li2O, 75Li2S·21P2S5·4P2O5, 33(0.7B2S3·0.3P2S5)·67Li2S, and 67(0.75Li2S·0.25P2S5)·33LiBH4.

[0080] In the embodiments of this application, the oxidized solid electrolyte can be selected from Li 3x La (2 / 3)-x □ (1 / 3)-2x TiO3 (□ represents a hole), Li 1+6x M 4+ 2-x M′ 3+ x (PO4)3(M=Ti, Ge, Sn, Hf, or Zr; M′= Al, Cr, Ga, Sc, Y, In, La), Li 16-2x M x (TO4)4(M=Mg,Zn; T=Si,Ge),Li 7-x La3Zr 2-x M x O 12 One or more of (M = Ta, Al, Ga, Nb, W).

[0081] In this embodiment of the application, the halide-type solid electrolyte can be selected from Li3MCl6 (M is Y, Sc, Er).

[0082] In this embodiment of the application, the polymer electrolyte includes a polymer material and a lithium salt; wherein, the polymer material may be one or more of polyethylene oxide (PEO), polypropylene oxide (PPO), polymethyl methacrylate (PMMA), polyacrylonitrile (PAN), and polyvinylidene fluoride (PVDF); and the lithium salt may be one or more of lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), lithium bis(fluorosulfonyl)imide (LiFSI), lithium trifluoromethanesulfonate (LiOTf), lithium hexafluorophosphate (LiPF6), lithium tetrafluoroborate (LiBF4), and lithium perchlorate (LiClO4).

[0083] In the embodiments of this application, the molar ratio of polymer material to lithium salt in polymer electrolyte can be 1:10-10:1, for example 1:10, 1:8, 1:5, 1:3, 1:1, 2:1, 3:1, 5:1, 8:1, 10:1.

[0084] In this embodiment, the gel electrolyte uses a polymer monomer and a lithium salt. The gel electrolyte includes the polymerization product of the polymer monomer. The polymer monomer may be one or more of 1,3-dioxolane (DOL), 1,4-dioxane, fluoroethylene carbonate (FEC), and methyl methacrylate (MMA). The lithium salt may be one or more of lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), lithium bis(fluorosulfonyl)imide (LiFSI), lithium trifluoromethanesulfonate (LiOTf), lithium hexafluorophosphate (LiPF6), lithium tetrafluoroborate (LiBF4), and lithium perchlorate (LiClO4).

[0085] In the embodiments of this application, the molar ratio of polymer monomers to lithium salts in the gel electrolyte can be 1:10-10:1, for example 1:10, 1:8, 1:5, 1:3, 1:1, 2:1, 3:1, 5:1, 8:1, 10:1.

[0086] In some embodiments of this application, the solid electrolyte layer 202 includes a composite solid electrolyte layer. Currently, batteries based on polymer solid electrolytes require relatively high temperatures (>50°C) to operate because polymer electrolytes have low room temperature conductivity, while most solid-state batteries based on inorganic solid electrolytes require high pressures (tens to hundreds of megapascals) to operate. Using an inorganic solid electrolyte combined with a polymer electrolyte and / or a gel electrolyte to form a composite solid electrolyte layer helps to balance the advantages of each type of electrolyte, enabling the battery 200 to operate better at room temperature and pressure, thus improving battery performance. It also improves the contact between the composite negative electrode 100 and the solid electrolyte layer 202, and improves the contact between the solid positive electrode 201 and the solid electrolyte layer 202, further enhancing battery performance.

[0087] In this embodiment of the application, the inorganic solid electrolyte in the composite solid electrolyte layer accounts for 50%-99% by mass, specifically, for example, 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, 95%, and 99%. In this embodiment of the application, the polymer electrolyte and gel electrolyte in the composite solid electrolyte layer account for 1%-50% by mass, specifically, for example, 1%, 5%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, and 50%. Maintaining a relatively high proportion of inorganic solid electrolyte in the composite solid electrolyte layer is beneficial for achieving higher room temperature conductivity in the solid electrolyte layer 202, thereby improving the battery's room temperature operating performance.

[0088] In this embodiment, the composite solid electrolyte layer is in the form of a film or sheet, with a thickness between 10 μm and 1000 μm. For example, the thickness is 10 μm, 20 μm, 50 μm, 100 μm, 150 μm, 200 μm, 300 μm, 400 μm, 500 μm, 600 μm, 700 μm, 800 μm, 900 μm, or 1000 μm.

[0089] In some embodiments of this application, such as Figure 4 As shown, a single-layer composite electrolyte membrane is formed by thoroughly mixing polymer electrolytes and / or gel electrolytes with inorganic solid electrolytes. In the composite solid electrolyte layer, the inorganic solid electrolyte is mixed and distributed with the polymer electrolyte and / or gel electrolyte; that is, the composite solid electrolyte layer is a homogeneous membrane layer composed of the inorganic solid electrolyte and the polymer electrolyte and / or gel electrolyte, which can be prepared using a wet process. This composite solid electrolyte layer possesses both high flexibility and density, is chemically stable to the composite negative electrode, and can achieve sufficient and stable contact with the solid positive and negative electrodes.

[0090] In other embodiments of this application, polymer electrolytes and / or gel electrolytes are bonded to an inorganic solid electrolyte layer as independent membrane layers to form a multilayer electrolyte membrane, such as... Figure 5As shown, the composite solid electrolyte layer, i.e., the solid electrolyte layer 202, includes an inorganic layer 2021 and an organic layer 2022 stacked on one or both sides of the inorganic layer 2021. The organic layer 2022 includes a polymer electrolyte layer or a gel electrolyte layer, and the thickness of the organic layer 2022 can be 1µm-50µm, specifically, for example, 1µm, 5µm, 10µm, 15µm, 20µm, 25µm, 30µm, 35µm, 40µm, 45µm, and 50µm. Introducing an ultrathin organic layer on the inorganic layer allows the solid electrolyte layer to possess both excellent ionic conductivity and density, preventing the liquid components in the composite negative electrode from seeping into the solid electrolyte and causing potential side reactions. The inorganic layer 2021 includes an inorganic solid electrolyte, the polymer electrolyte layer includes the polymer electrolyte, and the gel electrolyte layer includes the gel electrolyte. When the inorganic layer 2021 has an organic layer 2022 on only one side, the organic layer 2022 can be disposed on the side of the inorganic layer 2021 closer to the composite negative electrode 100, or it can be disposed on the side of the inorganic layer 2021 closer to the solid positive electrode 201. When the inorganic layer 2021 has organic layers 2022 on both sides, the organic layers 2022 on both sides can both be polymer electrolyte layers; or both can be gel electrolyte layers; or one side can be a polymer electrolyte layer and the other side can be a gel electrolyte layer.

[0091] In some embodiments of this application, the composite solid electrolyte layer includes an inorganic layer and a polymer electrolyte layer or a gel electrolyte layer stacked on the inorganic layer near the solid positive electrode side. Introducing a polymer electrolyte layer or a gel electrolyte layer on the positive electrode side of the full cell can achieve sufficient and stable contact between the positive electrode side and the solid electrolyte.

[0092] In some embodiments of this application, the composite solid electrolyte layer includes an inorganic layer and a polymer electrolyte layer stacked on both sides of the inorganic layer.

[0093] In some embodiments of this application, the composite solid electrolyte layer includes an inorganic layer, a polymer electrolyte layer stacked on the inorganic layer near the composite negative electrode side, and a gel electrolyte layer stacked on the inorganic layer near the solid positive electrode side.

[0094] In this application, the composite solid electrolyte layer can be prepared by directly coating the solid positive electrode.

[0095] The embodiments of this application can improve the solid-solid contact between the positive electrode side and the solid electrolyte by introducing polymer electrolyte and / or gel electrolyte inside or on the surface of the inorganic solid electrolyte, and can also further improve the contact between the negative electrode side and the solid electrolyte. This allows the battery 200 to avoid the problem that traditional all-solid batteries need to rely on high pressure and high temperature to cycle well, and better realize applications under normal temperature and pressure.

[0096] The battery in this application embodiment can operate at normal temperature and pressure, achieve stable cycling at normal temperature and pressure, and has high safety performance and high energy density.

[0097] The battery provided in this application embodiment can be used in terminal devices, such as consumer electronic products, such as mobile phones, tablets, power banks, laptops, and other wearable or mobile electronic devices, as well as in vehicles, energy storage devices, base stations, and other equipment products, to improve product safety and reliability.

[0098] See Figure 6 , Figure 6 This is a schematic diagram of the structure of an electrical device 300 provided in an embodiment of this application. The electrical device 300 includes a housing 311, electronic components housed within the housing 311, and the battery 200 described above in this embodiment of the application. The battery 200 supplies power to the electronic components. In this application, the electrical device 300 can be a consumer electronic product, such as a mobile phone, tablet computer, desktop computer, laptop computer, power bank, portable computer, smart screen, monitor, audio equipment, in-vehicle products, and other wearable or portable electronic devices (e.g., glasses, watches, bracelets, headphones, etc.), or it can be a vehicle, energy storage device, base station, or other equipment. Using the sodium-ion battery provided in this embodiment of the application can improve the safety and reliability of the product.

[0099] The embodiments of this application will be further described below through multiple examples.

[0100] Example 1

[0101] In this embodiment, Li6PS5Cl sulfide electrolyte is selected as the core lithium-conducting medium. A thin layer of PEO electrolyte is composited onto both sides of the sulfide electrolyte. The composite negative electrode consists of nickel foam, lithium-silicon alloy, and Li-Phen-DME liquid lithium solution. Figure 5 Assemble a coin cell (i.e., both sides of the solid electrolyte layer are composite negative electrodes) based on the battery model shown. The specific implementation steps are as follows:

[0102] (1) Take Li6PS5Cl tablets and press them to obtain Li6PS5Cl electrolyte tablets with a diameter of 15mm and a thickness of 0.6mm. Measure its ionic conductivity as 5mS / cm.

[0103] (2) Dissolve PEO and LiTFSI in acetonitrile (ACN) and stir at 25°C for 24 hours until PEO is completely dissolved and a uniform slurry is formed. Take 40 μL of the above slurry and drop it onto both sides of the Li6PS5Cl electrolyte sheet and coat it evenly. Bake and dry at 200°C to obtain the PEO composite Li6PS5Cl electrolyte sheet.

[0104] (3) Dissolve phenanthrene in 6 mL of ethylene glycol dimethyl ether (DME) to form a transparent Phen-DME solution. Dissolve lithium wire in the Phen-DME solution to form a blue-black Li-Phen-DME liquid lithium solution. The total conductivity of the liquid lithium solution is 10 mS / cm.

[0105] (4) Using nickel foam as a three-dimensional conductive framework, lithium-silicon alloy powder as a solid lithium source, and liquid lithium solution as... Figure 2 and Figure 3 The process shown yields a composite negative electrode.

[0106] (5) Attach the two composite negative electrodes to both sides of the PEO composite Li6PS5Cl electrolyte sheet to assemble a symmetrical battery.

[0107] Comparative Example 1

[0108] The only difference from Example 1 is that no liquid lithium solution was added during the preparation of the negative electrode.

[0109] Performance testing:

[0110] The charge-discharge cycle data of the symmetrical batteries of Example 1 and Comparative Example 1 were measured at 30°C using the Blue Battery Testing System, with a current density of 1.27 mA / cm². 2 .

[0111] Figure 7 The charge-discharge cycle curve of the symmetrical battery in Embodiment 1 of this application; from Figure 7 The symmetrical battery cycling curves show a relatively small initial polarization voltage of 0.2V, and a voltage of 1.27mA / cm. 2 It can cycle for over 800 hours at high current density. Meanwhile, the initial polarization voltage of the symmetrical cell in Comparative Document 1 was measured to be higher, at 0.5V, at 1.27mA / cm². 2 The battery could only cycle for 100 hours at high current density. The test results show that the symmetrical battery of Example 1 of this application achieved lower interfacial impedance and better cycle stability compared to Comparative Example 1. This indicates that the composite solid electrolyte and composite anode of this application have good contact and chemical compatibility, thus enabling the symmetrical battery to achieve lower interfacial impedance and better cycle stability.

[0112] Example 2

[0113] In this embodiment, Li6PS5Cl sulfide electrolyte is selected as the core lithium-conducting medium. A thin layer of PEO electrolyte is composited onto both sides of the sulfide electrolyte. The composite negative electrode consists of nickel foam, lithium-silicon alloy, and Li-BP-DME liquid lithium solution. Figure 5 Assemble a coin cell (i.e., both sides of the solid electrolyte layer are composite negative electrodes) based on the battery model shown. The specific implementation steps are as follows:

[0114] (1) Take Li6PS5Cl tablets and press them to obtain Li6PS5Cl electrolyte tablets with a diameter of 15mm and a thickness of 0.6mm. Measure its ionic conductivity as 5mS / cm.

[0115] (2) Dissolve PEO and LiTFSI in acetonitrile (ACN) and stir at 25°C for 24 hours until PEO is completely dissolved and a uniform slurry is formed. Take 40 μL of the above slurry and drop it onto both sides of the Li6PS5Cl electrolyte sheet and coat it evenly. Bake and dry at 200°C to obtain the PEO composite Li6PS5Cl electrolyte sheet.

[0116] (3) Dissolve biphenyl (BP) in 6 mL of ethylene glycol dimethyl ether (DME) to form a transparent BP-DME solution. Dissolve lithium wire in the BP-DME solution to form a blue-black Li-BP-DME liquid lithium solution. The total conductivity of the liquid lithium solution is 10 mS / cm.

[0117] (4) Using nickel foam as a three-dimensional conductive framework, lithium-silicon alloy powder as a solid lithium source, and liquid lithium solution as... Figure 2 and Figure 3 The process shown yields a composite negative electrode.

[0118] (5) Attach the two composite negative electrodes to both sides of the PEO composite Li6PS5Cl electrolyte sheet to assemble a symmetrical battery.

[0119] Comparative Example 2

[0120] The only difference from Example 2 is that no liquid lithium solution was added during the preparation of the negative electrode.

[0121] Performance testing:

[0122] The Blue Battery Testing System was used to conduct a limit current density test on the symmetrical batteries of Example 2 and Comparative Example 2 at 30°C. That is, the test current was gradually increased from 0.2mA to perform charge-discharge cycle tests on the symmetrical batteries until a short circuit occurred or the voltage reached the safe voltage of the testing instrument.

[0123] like Figure 8A and Figure 8B As shown, Figure 8A and Figure 8B This is the limiting current density test curve of the symmetrical battery in Embodiment 2 of this application.

[0124] from Figure 8A It can be seen that, under the test condition of fixing the single cycle time at 1 hour, the limiting current density of the symmetrical battery is as high as 4.2 mA / cm². 2 The critical areal capacity is as high as 2.1 mAh / cm³. 2 ;from Figure 8B It can be seen that the fixed single-cycle surface capacity is 0.16 mAh / cm². 2 Under the test conditions, the limiting current density of the symmetrical cell reached as high as 12.7 mA / cm². 2 Meanwhile, under the test condition of fixing the single cycle time at 1 hour, the limiting current density of the symmetrical cell in Comparative Example 2 was measured to be 2.1 mA / cm². 2 The critical areal capacity is 1.05 mAh / cm². 2 The single-cycle surface capacity is fixed at 0.16 mAh / cm². 2 Under the test conditions, the limiting current density of the symmetrical cell in Comparative Example 2 was measured to be as high as 6.3 mA / cm². 2 The critical current density of a symmetrical battery represents its ability to suppress lithium dendrite growth. The high critical current density of the symmetrical battery in Example 2 of this application fully demonstrates that the novel battery provided by this application can significantly suppress the formation of lithium dendrites and extend cycle life.

[0125] Example 3

[0126] In this embodiment, Li6PS5Cl sulfide electrolyte is selected as the core lithium-conducting medium. A thin layer of PEO electrolyte is composited onto both sides of the sulfide electrolyte. The composite negative electrode consists of nickel foam, lithium sheet, and Li-Phen-DME liquid lithium solution. Figure 5 Assemble a coin cell (i.e., both sides of the solid electrolyte layer are composite negative electrodes) based on the battery model shown. The specific implementation steps are as follows:

[0127] (1) Take Li6PS5Cl tablets and press them to obtain Li6PS5Cl electrolyte tablets with a diameter of 15mm and a thickness of 0.6mm. Measure its ionic conductivity as 5mS / cm.

[0128] (2) Dissolve PEO and LiTFSI in acetonitrile (ACN) and stir at 25°C for 24 hours until PEO is completely dissolved and a uniform slurry is formed. Take 40 μL of the above slurry and drop it onto both sides of the Li6PS5Cl electrolyte sheet and coat it evenly. Bake and dry at 200°C to obtain the PEO composite Li6PS5Cl electrolyte sheet.

[0129] (3) Dissolve phenanthrene in 6 mL of ethylene glycol dimethyl ether (DME) to form a transparent Phen-DME solution. Dissolve lithium wire in the Phen-DME solution to form a blue-black Li-Phen-DME liquid lithium solution. The total conductivity of the liquid lithium solution is 10 mS / cm.

[0130] (4) Using nickel foam as a three-dimensional conductive framework, lithium metal sheets as a solid lithium source, and liquid lithium solution as... Figure 2 and Figure 3 The process shown yields a composite negative electrode.

[0131] (5) Attach the two composite negative electrodes to both sides of the PEO composite Li6PS5Cl electrolyte sheet to assemble a symmetrical battery.

[0132] Performance testing:

[0133] The charge-discharge cycle data of the symmetrical battery were measured at 30°C using the Blue Battery Testing System, with a current density of 0.254 mA / cm². 2 . Figure 9 The charge-discharge cycle curve of the symmetrical battery in Embodiment 3 of this application; from Figure 9 The symmetrical battery cycling curves show a relatively small initial polarization voltage of 0.3V, at 0.254mA / cm. 2 The ability to cycle for nearly 1000 hours at a current density indicates that the composite solid electrolyte and the composite anode based on lithium metal as the lithium source have good contact and chemical compatibility. Therefore, this symmetric battery achieves low interfacial impedance and good cycle stability.

[0134] Example 4

[0135] In this embodiment, Li6PS5Cl sulfide electrolyte is selected as the core lithium-conducting medium. A thin layer of PEO electrolyte is composited onto the negative electrode side of the sulfide electrolyte, and a thin layer of DOL-LiFSI gel is composited onto the positive electrode side of the sulfide electrolyte. The composite negative electrode consists of nickel foam, lithium-silicon alloy, and Li-Phen-DEGME liquid lithium solution. The positive electrode is a lithium iron phosphate wet electrode (LFP loading of 2 mg / cm³). 2 ),by Figure 5 The battery model shown is assembled with a button cell. The specific implementation steps are as follows:

[0136] (1) Take Li6PS5Cl tablets and press them to obtain Li6PS5Cl electrolyte tablets with a diameter of 15mm and a thickness of 0.6mm. Measure its ionic conductivity as 5mS / cm.

[0137] (2) Dissolve PEO and LiTFSI in acetonitrile (ACN) and stir at 25°C for 24 hours until PEO is completely dissolved to form a uniform slurry. Take 40 μL of the above slurry and drop it onto one side of the Li6PS5Cl electrolyte sheet and coat it evenly. Bake and dry at 200°C to obtain a Li6PS5Cl electrolyte sheet with PEO composite on one side.

[0138] (3) Take DOL liquid, add LiFSI salt to it, stir at room temperature for several hours until DOL liquid becomes very viscous due to polymerization initiated by LiFSI, and obtain a viscous liquid. Take 10 μL of the above viscous liquid and spread it evenly on the surface of the lithium iron phosphate positive electrode. Then attach the positive electrode to the surface of the Li6PS5Cl electrolyte sheet and let it stand for several hours to wait for the DOL-LiFSI solution to fully gel. PEO and DOL are located on opposite sides of the Li6PS5Cl electrolyte sheet.

[0139] (4) Dissolve phenanthrene in 6 mL of diethylene glycol dimethyl ether (DEGME) to form a transparent Phen-DEGME solution. Dissolve lithium wire in the Phen-DEGME solution to form a blue-black Li-Phen-DEGME liquid lithium solution. The total conductivity of the liquid lithium solution is 6 mS / cm.

[0140] (5) Using nickel foam as a three-dimensional conductive framework, lithium-silicon alloy powder as a solid lithium source, and liquid lithium solution as... Figure 2 and Figure 3 The process shown yields a composite negative electrode.

[0141] (6) Attach the composite negative electrode to the side of the Li6PS5Cl electrolyte sheet that is composited with PEO and assemble it into a full cell.

[0142] Performance testing:

[0143] The charge-discharge cycle data of the entire battery were measured using the Blue Battery Testing System at 30°C, with a charge-discharge rate of 0.3C. Figure 10 The results of charge-discharge cycles for the full battery in Embodiment 4 of this application are shown. Figure 10 It can be seen that the first discharge capacity of the full battery is 137 mAh / g, the first coulombic efficiency is 96%, and the capacity retention rate is over 90% after 40 cycles, indicating that the full battery can achieve good cycling at room temperature and normal pressure.

[0144] Example 5

[0145] In this embodiment, Li6PS5Cl sulfide electrolyte is selected as the core lithium-conducting medium. A sulfide polymer composite electrolyte is prepared by thoroughly mixing DOL-LiFSI material and Li6PS5Cl sulfide electrolyte. The composite negative electrode consists of nickel foam, lithium-silicon alloy, and Li-Phen-DEGME liquid lithium solution. The positive electrode is a lithium iron phosphate wet-process electrode (LFP loading of 2 mg / cm³). 2 ),by Figure 4 The battery model shown is assembled with a button cell. The specific implementation steps are as follows:

[0146] (1) Take DOL liquid, add LiFSI salt and Li6PS5Cl electrolyte powder to it, stir at room temperature for several hours, and after the slurry becomes viscous, take the above viscous slurry and evenly coat it on the surface of lithium iron phosphate positive electrode sheet, and vacuum dry for several hours to prepare a sulfide polymer composite electrolyte membrane supported by lithium iron phosphate positive electrode sheet with a thickness of 200μm.

[0147] (2) Dissolve phenanthrene in 6 mL of diethylene glycol dimethyl ether (DEGME) to form a transparent Phen-DEGME solution. Dissolve lithium wire in the Phen-DEGME solution to form a blue-black Li-Phen-DEGME liquid lithium solution. The total conductivity of the liquid lithium solution is 6 mS / cm.

[0148] (3) Using nickel foam as a three-dimensional conductive framework, lithium-silicon alloy powder as a solid lithium source, and liquid lithium solution as... Figure 2 and Figure 3 The process shown yields a composite negative electrode.

[0149] (4) Attach the composite negative electrode to one side of the sulfide polymer composite electrolyte membrane obtained in step (1) and assemble it into a full cell.

[0150] Performance testing:

[0151] The full battery charge-discharge cycle data were measured using the Blue Battery Testing System at 30°C, with a charge-discharge rate of 0.2C. Figure 11 The results of charge-discharge cycles for the full battery in Embodiment 5 of this application are shown. Figure 11 It can be seen that the first-cycle discharge capacity of the full battery is 120mAh / g, the first-cycle coulombic efficiency is 91%, and the discharge capacity after fifteen cycles is 125mAh / g, with a coulombic efficiency of 99.2%, indicating that the full battery can achieve good cycling at room temperature and normal pressure.

[0152] It should be understood that the use of the terms "first," "second," and various numerical designations in this document is for descriptive convenience only and is not intended to limit the scope of this application.

[0153] In this application, "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, where A and B can be singular or plural. The character " / " generally indicates that the related objects before and after it are in an "or" relationship.

[0154] 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.

[0155] In this application, "-" indicates a range value, including the endpoint values ​​at both ends. For example, the value of a can be 0.5-15, meaning that the value of a can be between 0.5 and 15, and includes the endpoint values ​​of 0.5 and 15.

[0156] 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.

Claims

1. A composite negative electrode, characterized in that, The composite negative electrode includes a three-dimensional conductive framework layer and a solid lithium source layer, as well as a liquid lithium solution distributed in the three-dimensional conductive framework layer, wherein the solid lithium source layer includes a solid lithium source.

2. The composite negative electrode as described in claim 1, characterized in that, The liquid lithium solution is a mixed liquid system of lithium-containing ether solvent and polycyclic aromatic hydrocarbons or their derivatives.

3. The composite negative electrode as described in claim 1 or 2, characterized in that, The liquid lithium solution is prepared by mixing metallic lithium, polycyclic aromatic hydrocarbons or their derivatives, and ether solvents.

4. The composite negative electrode as described in claim 2 or 3, characterized in that, The polycyclic aromatic hydrocarbons or their derivatives include one or more of biphenyl compounds or their derivatives, naphthalene or its derivatives, anthracene or its derivatives, and phenanthrene or its derivatives. The ether solvents include one or more of the following: diethyl ether, methyl ether, ethylene glycol dimethyl ether, diethylene glycol dimethyl ether, triethylene glycol dimethyl ether, tetraethylene glycol dimethyl ether, polyethylene glycol dimethyl ether, tetrahydrofuran, 1,3-dioxocyclopentane, dipropyl ether, diisopropyl ether, ethyl butyl ether, dibutyl ether, dipentane ether, diisopentane ether, dihexyl ether, 2-methyltetrahydrofuran, 4-methyl-1,3-dioxocyclopentane, dimethoxymethane, 1,2-dimethoxypropane, dioxopentane, 1,4-dioxane, ethylene oxide, propylene oxide, and 1,1-diethoxyethane.

5. The composite negative electrode according to any one of claims 1-4, characterized in that, The total conductivity of the liquid lithium solution is not less than 1 mS / cm.

6. The composite negative electrode according to any one of claims 1-5, characterized in that, In the liquid lithium solution, the molar concentration of lithium is ≥0.5 mol / L.

7. The composite negative electrode according to any one of claims 1-6, characterized in that, The solid lithium source is also distributed in the three-dimensional conductive framework layer; the solid lithium source is distributed in the layer structure of the three-dimensional conductive framework layer at least on the side close to the solid lithium source layer.

8. The composite negative electrode as described in claim 7, characterized in that, In the three-dimensional conductive framework layer, the content of the solid lithium source gradually decreases from the direction closest to the solid lithium source layer to the direction furthest away from the solid lithium source layer.

9. The composite negative electrode according to any one of claims 1-8, characterized in that, In the composite negative electrode, the mass of lithium in the liquid lithium solution accounts for less than 5% of the total lithium mass in the solid lithium source and the liquid lithium solution.

10. The composite negative electrode according to any one of claims 1-9, characterized in that, The solid lithium source includes metallic lithium and / or lithium alloys; the three-dimensional conductive framework layer includes nickel foam, copper foam, carbon felt, or porous carbon layer.

11. A method for preparing a composite negative electrode, characterized in that, include: A solid lithium source is placed on a three-dimensional conductive framework layer, and pressure is applied to make the solid lithium source adhere to the three-dimensional conductive framework layer. Liquid lithium solution is added dropwise to allow it to penetrate into the three-dimensional conductive framework layer.

12. A battery, characterized in that, It includes a solid positive electrode, a composite negative electrode as described in any one of claims 1-10, and a solid electrolyte layer disposed between the solid positive electrode and the composite negative electrode.

13. The battery as claimed in claim 12, characterized in that, The solid electrolyte layer includes an inorganic solid electrolyte layer or a composite solid electrolyte layer; the inorganic solid electrolyte layer includes an inorganic solid electrolyte, and the composite solid electrolyte layer includes an inorganic solid electrolyte, as well as a polymer electrolyte and / or a gel electrolyte.

14. The battery as claimed in claim 13, characterized in that, In the composite solid electrolyte layer, the inorganic solid electrolyte is mixed and distributed with the polymer electrolyte and / or gel electrolyte.

15. The battery as claimed in claim 13, characterized in that, The composite solid electrolyte layer includes an inorganic layer and an organic layer stacked on one or both sides of the inorganic layer. The organic layer includes a polymer electrolyte layer or a gel electrolyte layer. The inorganic layer includes the inorganic solid electrolyte, the polymer electrolyte layer includes the polymer electrolyte, and the gel electrolyte layer includes the gel electrolyte.

16. The battery as claimed in claim 15, characterized in that, The composite solid electrolyte layer includes an inorganic layer and polymer electrolyte layers stacked on both sides of the inorganic layer; or The composite solid electrolyte layer includes an inorganic layer, a polymer electrolyte layer stacked on the inorganic layer near the composite negative electrode, and a gel electrolyte layer stacked on the inorganic layer near the solid positive electrode.

17. The battery according to any one of claims 13-16, characterized in that, In the composite solid electrolyte layer, the total mass percentage of polymer electrolyte and gel electrolyte is 1%-50%.

18. The battery according to any one of claims 13-17, characterized in that, The inorganic solid electrolyte includes one or more of the following: oxidized solid electrolyte, sulfide solid electrolyte, and halide solid electrolyte; The polymer electrolyte comprises a polymer material and a lithium salt; the gel electrolyte uses a polymer monomer and a lithium salt. The polymer material includes one or more of polyethylene oxide, polypropylene oxide, polymethyl methacrylate, polyacrylonitrile, and polyvinylidene fluoride; the polymer monomer includes one or more of 1,3-dioxolane, 1,4-dioxane, fluoroethylene carbonate, and methyl methacrylate; the lithium salt includes one or more of lithium bis(trifluoromethanesulfonyl)imide, lithium bis(fluorosulfonyl)imide, lithium trifluoromethanesulfonate, lithium hexafluorophosphate, lithium tetrafluoroborate, and lithium perchlorate.

19. The battery according to any one of claims 12-18, characterized in that, The mass of the liquid lithium solution accounts for less than 5% of the total mass of the battery.

20. An electrical appliance, characterized in that, The electrical device includes the battery as described in any one of claims 12-19.

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