A lithium metal battery with a chemical potential gradient driven interface and applications thereof

Abstract

The application discloses a lithium metal battery with a chemical potential gradient driven interface and application thereof, and comprises a positive electrode, an electrolyte, a diaphragm, a lithium boron alloy negative electrode wrapped with a chemical potential gradient driven interface layer, wherein the chemical potential gradient driven interface layer is formed through a "polymerization coupling-orientation reorganization-in-situ growth" method, lithium salt and additive molecules in the electrolyte are first adsorbed to the surface of the lithium boron alloy through electrostatic force to form a physical connection interface, and then the interface is induced through electric field regulation, so that the electron-deficient boron sites enriched at the interface are arranged in order, the local electron density at the interface is changed, the content of boron elements in the interface layer is distributed in a gradient manner, specific chemical reactions are promoted, and the rate performance and cycle life of the battery are improved. The lithium metal battery has good interface stability and can significantly improve the electrochemical performance of the battery.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of lithium metal batteries, and relates to a lithium metal battery with a chemical potential gradient driven interface and application thereof. BACKGROUND

[0002] Lithium batteries have advantages such as high energy density and long cycle life, and have been widely used in various fields. At present, lithium ion batteries are the most popular type, but their energy density has reached a technical bottleneck due to the limitation of the specific capacity (372 mAh / g) of the negative electrode graphite material. Metal lithium has a low redox potential (-3.04 V) and a theoretical specific capacity (3860 mAh / g) 10 times higher than that of traditional graphite negative electrodes, and is recognized by the industry as the ultimate solution for high-energy-density lithium battery negative electrodes. Therefore, the development of lithium metal batteries and related technologies is crucial to break through the technical bottleneck of lithium battery energy density.

[0003] The electrode and electrolyte interface layer is crucial to the performance and safety of lithium metal batteries. A good interface layer can effectively isolate the chemical reaction between the lithium metal electrode and the electrolyte, prevent unnecessary electrolyte decomposition and instability of the solid electrolyte interface layer, and in addition, can promote the directional and uniform deposition of lithium ions, thereby avoiding the formation of lithium dendrites and the unevenness of the electrode surface, which can lead to reduced battery safety and shortened cycle life. At present, the lithium metal battery interface layer still faces many challenges in stability and performance optimization. Due to the limitations of its chemical composition and electrochemical properties, the traditional interface layer cannot fully meet the needs of high-energy-density batteries. In particular, under high-rate charging and discharging and long-term cycling conditions, the existing interface layer may fail and peel off, leading to reduced battery performance or safety hazards.

[0004] Therefore, in order to further improve the energy density, safety and cycle life of lithium metal batteries, the modification and optimization of the interface layer are particularly critical. By introducing new materials, nanostructure design, interface chemical regulation and other strategies, the stability and electrochemical performance of the interface layer can be effectively improved, thereby promoting the development and application of lithium metal battery technology. SUMMARY

[0005] The purpose of the present application is to overcome the shortcomings and deficiencies of the prior art, and to provide a lithium metal battery with a chemical potential gradient driven interface and application thereof.

[0006] In a first aspect, the present application provides a negative electrode with a chemical potential gradient driven interface, wherein the negative electrode is a lithium boron alloy negative electrode with a surface wrapped with a chemical potential gradient driven interface layer.

[0007] The chemical potential gradient driven interface layer is prepared by including the following steps:

[0008] S1, polymerization coupling: under inert atmosphere, the molecules in the electrolyte are adsorbed to the surface of the lithium-boron alloy negative electrode by electrostatic force, forming a (physical) connection interface;

[0009] S2, orientation recombination: using electric field regulation, the (enriched) electron-deficient boron sites at the interface in step S1 are induced to orderly arrange, and the lithium-boron alloy is subjected to chemical potential gradient driven chemical reaction;

[0010] S3, in-situ growth: the lithium-boron alloy after reaction is dried and treated, forming a (in-situ grown) chemical potential gradient driven interface layer.

[0011] As an embodiment of the present application, the lithium-boron alloy is a low-content boron-doped lithium alloy, wherein the atomic ratio of lithium to boron is (90-99.5):(0.5-10). Its role is to balance the energy density and safety of the battery, high lithium content ensures the high capacity and good conductivity of the battery, and appropriate boron helps to inhibit the growth of lithium dendrites, improve the cycle stability and safety, and beyond this range may cause the battery performance to decline or increase the safety risk. If the boron content is less than 0.5%, it may cause the growth of lithium dendrites in the lithium metal battery during the cycle process, increase the risk of short circuit and thermal runaway, thereby affecting the safety and life of the battery; if the boron content is too high, it may cause the electrical conductivity of the alloy to decrease, and may also cause the phase separation or structural change of the negative electrode material, thereby reducing the stability and cycle life of the battery.

[0012] As an embodiment of the present application, in step S1, the electrolyte includes lithium salt, solvent, additive; the additive includes lithium salt-based boron compound.

[0013] Further, the lithium salt includes at least one of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium bisfluorosulfonylimide; the concentration of the lithium salt in the electrolyte is 0.1-2.0 mol / L. The lithium salt with a suitable concentration can ensure that the electrolyte has sufficient ionic conductivity, so that the lithium ion can migrate efficiently in the battery, thereby improving the charge-discharge performance and power density of the battery, and if the concentration is too low, it may cause insufficient conductivity, affecting the performance of the battery; if the concentration is too high, it may cause the viscosity of the electrolyte to increase, reducing the ion migration speed; in addition, the lithium salt can help form a stable interface layer, thereby improving the long-term stability and safety of the battery.

[0014] Further, the solvent includes at least one of carbonates, carboxylates, ethers, sulfones, nitriles, fluorinated carbonates, fluorinated carboxylates, fluorinated ethers, fluorinated sulfones. Preferably, the solvent includes fluorinated carbonates, fluorinated ethers. More preferably, the solvent includes at least one of fluorinated ethylene carbonate, fluorinated ethylene carbonate, 3,3,3-trifluoropropene carbonate, bis(2,2,2-trifluoroethyl) ether, 1,1,2,2-tetrafluoroethyl 2,2,3,3-tetrafluoropropyl ether, fluorinated orthoformate.

[0015] Further, the lithium salt-based boron compound includes at least one of lithium bis(oxalato)borate, lithium difluoro(oxalato)borate, lithium trifluoro(perfluoro-t-butoxy)borate.

[0016] Further, the addition amount of the lithium salt-based boron compound is 0.01w% to 5w% of the total mass of the electrolyte. The lithium salt-based boron compound can effectively improve the chemical stability and electrochemical stability window of the electrolyte, thereby reducing the side reactions and safety hazards generated during the charging and discharging process of the lithium metal battery, ensuring that the lithium salt-based boron compound plays the best inhibitor role in the electrolyte, while not causing negative side effects. If it is less than 0.01w%, it may not be enough to significantly improve the stability and ionic conductivity of the electrolyte; if it is more than 5w%, it may cause an increase in the viscosity of the electrolyte, affecting the ionic conductivity; and too much additive may also cause a decrease in the concentration of lithium salt in the electrolyte, reducing the energy density of the battery, and may cause other side reactions, thereby affecting the overall performance and stability of the battery.

[0017] In the present application, the boron element component layer of the lithium salt-based boron compound in the chemical potential gradient driven interface layer and the boron element component layer of the lithium boron alloy are reversibly diffused with boron atoms between the two component layers, and the boron element content in the interface layer is gradiently distributed, which mainly functions to not only improve the chemical reaction kinetics and improve the ionic conductivity, but also to improve the charging and discharging cycle stability of the battery and prolong the service life of the battery by ensuring the gradient distribution and rapid diffusion of ions in the interface layer.

[0018] As an embodiment of the present application, the thickness of the chemical potential gradient driven interface layer is 600 nm to 10 μm. The appropriate thickness can effectively improve the ion conductivity of the battery, ensure that the interface layer maintains good mechanical stability during the charging and discharging process, and avoid interface structure failure caused by lithium deposition or dissolution. If the thickness is less than 600 nm, it may not be able to form an effective chemical potential gradient, which is insufficient to cope with the stress and chemical reaction inside the battery, resulting in unstable interface during the charging and discharging process of the battery, affecting the performance of the battery, and the too thin interface layer may not meet the ion migration requirements of the battery, reducing the charging and discharging efficiency; if the thickness is higher than 10 μm, it will increase the ion diffusion path, reduce the power density and charging and discharging rate of the battery, and the too thick interface layer may cause instability of the interface structure during the charging and discharging process, increase the mechanical stress of the battery, and thus affect its long life and cycle stability.

[0019] In the present application, the chemical potential gradient driven interface is formed by the method of "polymerization coupling-orientation reorganization-in situ growth".

[0020] As an embodiment of the present application, in step S1, the inert atmosphere includes argon.

[0021] As an embodiment of the present application, in step S1, the ambient temperature of the electrostatic force acting environment is 20℃ to 25℃, and the distance between the electrostatic field generator and the electrode is 1cm to 10cm. The main purpose is to ensure that the strength and uniformity of the electrostatic field are not affected by temperature changes during the entire operation process, and by adjusting the distance between the electrostatic field generator and the electrode, the size of the electrostatic force can be controlled. The appropriate distance can ensure that the electrostatic force effectively attracts the target substance to the surface, while avoiding too large distance leading to weakening of the electrostatic force and affecting the adsorption effect.

[0022] As an embodiment of the present application, in step S2, the method of inducing includes electric field regulation. By applying an electric field through an electric field regulator, the orientation and arrangement of molecules or ions on the interface are regulated to induce the ordered arrangement of electron-deficient boron sites enriched at the interface.

[0023] Further, the electric field strength of the electric field regulation is 80-120V / m. The ambient temperature of the electric field regulation is 15-35℃.

[0024] In step S2 of the present application, the specific process of orientation reorganization includes: inducing the ordered arrangement of electron-deficient boron sites enriched at the interface by regulating the orientation and arrangement of molecules or ions on the interface, so as to form a local electron density change on the interface that is conducive to chemical reaction, and establish a chemical potential gradient to drive the chemical reaction.

[0025] As an embodiment of the present application, in step S3, the standing time is 30 min to 5 h, and the drying treatment temperature is 60 DEG C to 120 DEG C.

[0026] In a second aspect, the present application provides a lithium metal battery with a chemical potential gradient driven interface, the lithium metal battery comprising a positive electrode, an electrolyte, a separator, and the negative electrode.

[0027] As an embodiment of the present application, the positive electrode comprises a positive electrode active material, the positive electrode active material being selected from at least one of lithium cobaltate positive electrode material, lithium iron phosphate positive electrode material, lithium manganate positive electrode material, lithium nickelate positive electrode material, ternary positive electrode material, and modified materials thereof.

[0028] As an embodiment of the present application, the separator comprises polypropylene (PP), polyethylene (PE), and ceramic composite separator.

[0029] In a third aspect, the present application provides a use of a lithium metal battery with a chemical potential gradient driven interface in the preparation of electric aviation products.

[0030] Compared with the prior art, the present application has the following beneficial effects:

[0031] 1. Firstly, the present application uses electrostatic force to adsorb lithium salt and additive molecules in the electrolyte to the lithium borohydride alloy surface to form a physical connection interface; further, the interface is induced by using electric field regulation, so that the electron-deficient boron sites enriched at the interface are orderly arranged, resulting in changes in local electron density at the interface and gradient distribution of boron content in the interface layer, thereby promoting specific chemical reactions and improving the rate performance and cycle life of the battery.

[0032] 2. Compared with the vertical immersion in the prior art, the electrostatic adsorption used in the present application can enhance the bonding force between the lithium borohydride negative electrode and the electrolyte, reduce the contact impedance between the electrode and the electrolyte; and the physical interface layer formed by the adsorbed molecules can play a protective role, reducing the risk of dissolution of the lithium borohydride negative electrode in the electrolyte, while improving the compatibility of the lithium borohydride negative electrode with the electrolyte, reducing the generation of adverse interface reactions and by-products, thereby significantly improving the rate performance and cycle life of the lithium metal battery.

[0033] 3. Compared to high-temperature heat treatment in existing technologies, the electric field modulation employed in this invention can more precisely guide molecules or ions at the interface, enabling the enriched electron-deficient boron sites to arrange themselves in an orderly manner under the influence of the electric field. This orderly arrangement can lead to changes in local electron density at the interface, thereby promoting specific chemical reactions and improving the battery's charge-discharge efficiency, rate performance, and cycle life. Furthermore, the orderly arrangement of electron-deficient boron sites can form a more stable chemical potential gradient (i.e., a gradient distribution of boron content in the interface layer), which facilitates rapid charge transfer, thus enhancing the overall performance of the battery.

[0034] 4. The lithium metal battery of this invention has good interface stability, which can significantly improve the electrochemical performance of the battery, help promote the advancement of lithium metal battery technology, and provide reliable support for the research on battery performance improvement and material interface modification. Attached Figure Description

[0035] Other features, objects, and advantages of the invention will become more apparent from the following detailed description of non-limiting embodiments with reference to the accompanying drawings:

[0036] Figure 1 A schematic diagram of the components of the chemical potential gradient driven interface provided in Example 1;

[0037] Figure 2 The XPS signal gradient variation diagram of boron in the interface layer provided in Example 1;

[0038] Figure 3 A schematic flowchart of the method for forming a chemical potential gradient driven interface provided in Example 1;

[0039] Figure 4 The full-cell cycle performance diagram of lithium cobalt oxide as the cathode material at 1C rate provided in Example 1;

[0040] Figure 5 The full-cell cycle performance diagram of lithium iron phosphate as the cathode material at a 0.5C rate provided in Example 2;

[0041] Figure 6 A schematic diagram of the morphology of the chemical potential gradient driven interface provided in Example 1;

[0042] Figure 7 The rate performance diagram of the full cell with lithium cobalt oxide as the cathode material provided in Example 1;

[0043] Figure 8 The full-cell cycle performance diagram of lithium cobalt oxide as the cathode material is provided for Comparative Example 1.

[0044] Figure 9 The rate performance diagram of the full cell with lithium cobalt oxide as the cathode material provided for Comparative Example 1;

[0045] Figure 10 Cycle performance graph of full battery using lithium iron phosphate provided for Comparative Example 2 as a positive electrode material;

[0046] Figure 11 Rate performance graph of full battery using lithium iron phosphate provided for Comparative Example 2 as a positive electrode material;

[0047] Figure 12 Cycle performance graph of full battery using lithium cobaltate provided for Comparative Example 3 as a positive electrode material;

[0048] Figure 13 Rate performance graph of full battery using lithium cobaltate provided for Comparative Example 3 as a positive electrode material;

[0049] Figure 14 Cycle performance graph of full battery using lithium cobaltate provided for Comparative Example 4 as a positive electrode material;

[0050] Figure 15 Rate performance graph of full battery using lithium cobaltate provided for Comparative Example 4 as a positive electrode material. DETAILED DESCRIPTION

[0051] In order to make the objects, technical solutions, and advantages of the present application clearer, the present application will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0052] It should be noted that, unless otherwise defined, technical terms or scientific terms used in the embodiments of the present application should be understood as their common meanings to those of ordinary skill in the art to which the present application pertains. The terms "first", "second", and similar terms used in the embodiments of the present application do not denote any order, quantity, or importance, but are only used to distinguish different components. The terms "include", "contain", and similar terms mean that the elements or objects before the terms encompass the elements or objects listed after the terms and their equivalents, without excluding other elements or objects. The terms "connect" and "connected" and similar terms do not mean only physical or mechanical connections, but can also include electrical connections, whether direct or indirect. The terms "upper", "lower", "left", "right", and the like only denote relative positional relationships, and when the absolute positions of the described objects change, the relative positional relationships can also change accordingly.

[0053] The present application will be described in detail below with reference to the embodiments. The following embodiments will help those skilled in the art to further understand the present application, but do not limit the present application in any form. It should be noted that, for those skilled in the art, without departing from the concept of the present application, a number of adjustments and improvements can be made. These all belong to the protection scope of the present application.

[0054] Example 1

[0055] Reference Figure 3 The method for forming the chemical potential gradient driven interface layer adopts a "polymerization coupling-orientation reorganization-in-situ growth" method to form a chemical potential gradient driven interface layer, and further assembles a battery to obtain a lithium metal battery with a chemical potential gradient driven interface layer, which comprises a positive electrode, an electrolyte, a separator, and a lithium borohydride negative electrode wrapped with a chemical potential gradient driven interface layer, the atomic ratio of lithium to boron in the lithium borohydride is 99:1, the electrolyte comprises a lithium salt, a solvent and an additive, the additive is a lithium salt-based boron compound, the lithium salt-based boron compound is lithium difluoro(oxalato)borate, the addition amount of the lithium difluoro(oxalato)borate is 1% of the total mass of the electrolyte; the lithium salt is lithium hexafluorophosphate, the concentration of the lithium salt in the electrolyte is 1 mol / L; the solvent is fluoroethylene carbonate, the positive electrode comprises a positive electrode active material, and the positive electrode active material is a lithium cobaltate positive electrode material; the separator is polypropylene (PP).

[0056] The method for forming the chemical potential gradient driven interface layer comprises the following steps:

[0057] S1, polymerization coupling: under an argon atmosphere, molecules in the electrolyte are adsorbed to the surface of the lithium borohydride negative electrode by electrostatic force, the environmental temperature of the electrostatic force adsorption is 25°C, the distance between the electrostatic field generator and the electrode (i.e. the negative electrode) is 3 cm, and a physically connected interface is formed.

[0058] S2, orientation reorganization: an electric field is applied by an electric field regulator, the orientation and arrangement of molecules or ions on the interface are regulated by the electric field, the ordered arrangement of electron-deficient boron sites enriched at the interface is induced, a local electron density change conducive to chemical reactions is formed on the interface, and a chemical potential gradient is established to drive chemical reactions. The electric field strength of the electric field regulation is 100 V / m, and the environmental temperature is 25°C.

[0059] S3, in-situ growth: the reacted lithium borohydride negative electrode is left to dry, the standing time is 2 h, and the drying temperature is 80°C, and an in-situ grown chemical potential gradient driven interface is formed, and the thickness is 5 μm. The component diagram of the chemical potential gradient driven interface layer is shown in Figure 1 , which comprises a boron element component layer in the lithium borohydride and a boron element component layer in the lithium salt-based boron compound, the boron atoms in the boron element component layer reversibly diffuse with each other, the boron content in the interface layer is gradiently distributed, and the XPS signal gradient change diagram of boron in the interface layer is shown in Figure 2 . Figure 6

[0060] The battery has excellent cycle stability, as shown in Figure 4 , the capacity retention rate is 91.72% after stable cycling at 1C rate for 300 cycles. From the rate performance Figure 7 ​As can be seen, the specific capacity is about 175 mAh / g at a rate of 0.1C, about 170 mAh / g at a rate of 0.5C, about 160 mAh / g at a rate of 3C, and about 170 mAh / g again when returning to a rate of 0.5C, exhibiting excellent rate performance.

[0061] Example 2

[0062] The "polymerization coupling-orientation reorganization-in-situ growth" method is used to form a chemical potential gradient driven interface layer, and a lithium metal battery with a chemical potential gradient driven interface layer is further assembled, which comprises a positive electrode, an electrolyte, a separator, a lithium boride alloy negative electrode, and a chemical potential gradient driven interface layer wrapped on the surface thereof. The atomic ratio of lithium and boron in the lithium boride alloy is 99:1. The electrolyte comprises a lithium salt, a solvent and an additive. The additive is a lithium salt-based boron compound. The lithium salt-based boron compound is lithium difluoro(oxalato)borate. The addition amount of the lithium difluoro(oxalato)borate is 2% of the total mass of the electrolyte. The lithium salt is lithium hexafluorophosphate. The concentration of the lithium salt in the electrolyte is 0.5 mol / L. The solvent is fluoroethylene carbonate. The positive electrode comprises a positive electrode active material, and the positive electrode active material is a lithium cobaltate positive electrode material. The separator is polypropylene (PP).

[0063] The method for forming the chemical potential gradient driven interface layer comprises the following steps:

[0064] S1, polymerization coupling: under an argon atmosphere, molecules in the electrolyte are adsorbed to the surface of the lithium boride alloy negative electrode by electrostatic force. The environmental temperature of the electrostatic force adsorption is 25°C. The distance between the electrostatic field generator and the electrode is 2 cm, forming a physically connected interface.

[0065] S2, orientation reorganization: an electric field is applied by an electric field adjuster. The orientation and arrangement of molecules or ions on the interface are regulated by the electric field. The ordered arrangement of electron-deficient boron sites enriched at the interface is induced, thereby forming a local electron density change on the interface that is conducive to chemical reactions, and establishing a chemical potential gradient to drive chemical reactions.

[0066] S3, in-situ growth: the reacted lithium boride alloy negative electrode is left to dry, the standing time is 2 h, and the drying temperature is 80°C, forming an in-situ grown chemical potential gradient driven interface layer with a thickness of 5.5 μm.

[0067] The battery has excellent cycle stability. As shown in Figure 5 , the capacity retention rate is 96.8% after stable cycling at a rate of 0.5C for 100 cycles.

[0068] Example 3

[0069] The method of "polymerization coupling-orientation reorganization-in-situ growth" is used to form an interface layer driven by chemical potential gradient, and further assemble a battery to obtain a lithium metal battery with an interface layer driven by chemical potential gradient, which comprises a positive electrode, an electrolyte, a separator, a lithium boride alloy negative electrode, and a chemical potential gradient driven interface layer wrapped on the surface of the lithium boride alloy negative electrode, the atomic ratio of lithium to boron in the lithium boride alloy is 99:1, the electrolyte comprises a lithium salt, a solvent and an additive, the additive is a lithium salt-based boron compound, the lithium salt-based boron compound is lithium difluoro(oxalato)borate, the addition amount of the lithium difluoro(oxalato)borate is 2% of the total mass of the electrolyte, the lithium salt is lithium hexafluorophosphate, the concentration of the lithium salt in the electrolyte is 1 mol / L, the solvent is fluoroethylene carbonate, the positive electrode comprises a positive electrode active material, and the positive electrode active material is a lithium cobaltate positive electrode material; the separator is polypropylene (PP).

[0070] The method for forming the interface layer driven by chemical potential gradient comprises the following steps:

[0071] S1, polymerization coupling: under an argon atmosphere, molecules in the electrolyte are adsorbed to the surface of the lithium boride alloy negative electrode by electrostatic force, the environmental temperature of the electrostatic force adsorption is 25°C, the distance between the electrostatic field generator and the electrode is 2.5 cm, and a physically connected interface is formed.

[0072] S2, orientation reorganization: an electric field is applied by an electric field adjuster, the orientation and arrangement of molecules or ions on the interface are regulated by the electric field, the ordered arrangement of electron-deficient boron sites enriched at the interface is induced, a local electron density change conducive to chemical reaction is formed on the interface, and a chemical potential gradient is established to drive the chemical reaction.

[0073] S3, in-situ growth: the reacted lithium boride alloy negative electrode is placed and dried, the placing time is 2 h, the drying temperature is 80°C, an in-situ grown chemical potential gradient driven interface is formed, and the thickness of the interface is 6 μm.

[0074] Example 4

[0075] The method of "polymerization coupling-orientation reorganization-in-situ growth" is used to form an interface layer driven by chemical potential gradient, and further assemble a battery to obtain a lithium metal battery with an interface layer driven by chemical potential gradient, which comprises a positive electrode, an electrolyte, a separator, a lithium boride alloy negative electrode, and a chemical potential gradient driven interface layer wrapped on the surface of the lithium boride alloy negative electrode, the atomic ratio of lithium to boron in the lithium boride alloy is 98.5:1.5, the electrolyte comprises a lithium salt, a solvent and an additive, the additive is a lithium salt-based boron compound, the lithium salt-based boron compound is lithium difluoro(oxalato)borate, the addition amount of the lithium difluoro(oxalato)borate is 2% of the total mass of the electrolyte, the lithium salt is lithium hexafluorophosphate, the concentration of the lithium salt in the electrolyte is 2 mol / L, the solvent is fluorocarbon carbonate and fluorinated ether, the positive electrode comprises a positive electrode active material, and the positive electrode active material is a lithium cobaltate positive electrode material; the separator is a polypropylene (PP) separator.

[0076] The method for forming the interface layer driven by chemical potential gradient comprises the following steps:

[0077] S1, polymerization coupling: under an argon atmosphere, molecules in the electrolyte are adsorbed to the surface of the lithium boride alloy negative electrode by electrostatic force, the environmental temperature of the electrostatic force adsorption is 25°C, the distance between the electrostatic field generator and the electrode is 3 cm, and a physically connected interface is formed.

[0078] S2, orientation reorganization: an electric field is applied by an electric field adjuster, the orientation and arrangement of molecules or ions on the interface are regulated by the electric field, the ordered arrangement of electron-deficient boron sites enriched at the interface is induced, a local electron density change conducive to chemical reaction is formed on the interface, and a chemical potential gradient is established to drive the chemical reaction.

[0079] S3, in-situ growth: the reacted lithium boride alloy negative electrode is placed and dried, the placing time is 2 h, the drying temperature is 80°C, an in-situ grown chemical potential gradient driven interface is formed, and the thickness of the interface is 8 μm.

[0080] Example 5

[0081] The method of "polymerization coupling-orientation reorganization-in-situ growth" is adopted to form an interface layer driven by chemical potential gradient, and a lithium metal battery with the interface layer driven by chemical potential gradient is further assembled, which comprises a positive electrode, an electrolyte, a separator, a lithium boride alloy negative electrode, and a chemical potential gradient driven interface layer wrapped on the surface of the lithium boride alloy negative electrode, the atomic ratio of lithium and boron in the lithium boride alloy is 99.5:0.5, the electrolyte comprises a lithium salt, a solvent and an additive, the additive is a lithium salt-based boron compound, the lithium salt-based boron compound is lithium difluoro(oxalato)borate, the addition amount of the lithium difluoro(oxalato)borate is 2% of the total mass of the electrolyte, the lithium salt is lithium hexafluorophosphate, the concentration of the lithium salt in the electrolyte is 1.5 mol / L, the solvent is fluorocarbon carbonate and fluorinated ether, and the positive electrode comprises a positive electrode active material, and the positive electrode active material is a lithium cobaltate positive electrode material; the separator is polypropylene (PP).

[0082] The method for forming the interface layer driven by chemical potential gradient comprises the following steps:

[0083] S1, polymerization coupling: under an argon atmosphere, molecules in the electrolyte are adsorbed to the surface of the lithium boride alloy negative electrode by electrostatic force, the environmental temperature of the electrostatic force adsorption is 25°C, the distance between the electrostatic field generator and the electrode is 3 cm, and a physically connected interface is formed.

[0084] S2, orientation reorganization: an electric field is applied by an electric field adjuster, the orientation and arrangement of molecules or ions on the interface are regulated by the electric field, the ordered arrangement of electron-deficient boron sites enriched at the interface is induced, a local electron density change conducive to chemical reaction is formed on the interface, and a chemical potential gradient is established to drive the chemical reaction.

[0085] S3, in-situ growth: the lithium boride alloy negative electrode after reaction is left to dry, the left time is 2 h, and the drying temperature is 80°C, and an in-situ grown chemical potential gradient driven interface layer is formed, and the thickness of the interface layer is 7 μm.

[0086] Comparative Example 1

[0087] The preparation of the lithium metal battery in the present comparative example is basically the same as that in Example 1, except that the electrostatic force in step S1 is replaced by vertical immersion, specifically:

[0088] S1, under an inert atmosphere, the lithium boride alloy negative electrode is vertically immersed in the electrolyte and vertically taken out.

[0089] The cycle performance of the lithium metal battery is as shown in Figure 8 The rate performance is as shown in Figure 9As shown, the electrostatic force used in Example 1 can enhance the binding force between the lithium borohydride alloy negative electrode and the electrolyte, form a physical interface layer, thereby reducing the contact impedance between the electrode and the electrolyte and the risk of electrode dissolution, the generation of adverse interface reactions and byproducts, improving the interface stability, reactivity and compatibility, and thus significantly improving the cycle performance and rate performance of the battery.

[0090] Comparative Example 2

[0091] The preparation of the lithium metal battery in this comparative example is basically the same as that in Example 1, except that step S2 is omitted, specifically:

[0092] S1, under an argon atmosphere, the molecules in the electrolyte are adsorbed to the surface of the lithium borohydride alloy negative electrode by electrostatic force, the environmental temperature of the electrostatic force adsorption is 25°C, the distance between the electrostatic field generator and the electrode is 3cm, and a physically connected interface is formed;

[0093] S2, the lithium borohydride alloy negative electrode is placed and dried, the standing time is 2h, and the drying temperature is 80°C.

[0094] The cycle performance of the lithium metal battery is as shown in Figure 10 , and the rate performance is as shown in Figure 11 .

[0095] Comparative Example 3

[0096] The preparation of the lithium metal battery in this comparative example is basically the same as that in Example 1, except that the electric field regulation in step S2 is replaced by high-temperature heat treatment, specifically:

[0097] S2, high-temperature heat treatment is used at a temperature of 70°C for 1h.

[0098] The cycle performance of the lithium metal battery is as shown in Figure 12 , and the rate performance is as shown in Figure 13 . High-temperature heat treatment is difficult to achieve the precise molecular-level arrangement as the electric field regulation, so its cycle performance and rate performance are significantly lower than those of Example 1. The electric field regulation used in Example 1 can make the ordered arrangement of the electron-rich boron sites, forming an interface with enhanced reactivity. This arrangement can lead to changes in local electron density at the interface, thereby promoting specific chemical reactions and improving the cycle performance and rate performance of the battery.

[0099] Comparative Example 4

[0100] The preparation of the lithium metal battery in this comparative example is basically the same as that in Example 1, except that the electric field strength of the electric field regulation in step S2 is adjusted to 300V / m. The cycle performance of the lithium metal battery is as shown in Figure 14 , and the rate performance is as shown in Figure 15As shown, the high electric field strength can affect the induction of the electron-deficient boron site, reduce the promotion of specific chemical reactions, and thus reduce the cycle performance and rate performance of the battery.

[0101] Those skilled in the art should understand that the above discussion of any embodiment is only exemplary and is not intended to suggest that the scope of the present application is limited to these examples; under the idea of the present application, the above embodiments or technical features among different embodiments can also be combined, the steps can be implemented in any order, and there are many other changes of different aspects of the embodiments of the present application as described above, which are not provided in details for the sake of brevity.

[0102] In addition, in the case of setting forth details to describe the exemplary embodiments of the present application, it is obvious to those skilled in the art that the embodiments of the present application can be implemented without these details or with changes of these details. Therefore, these descriptions should be considered as illustrative rather than limiting.

[0103] To simplify the description and discussion, and so as not to make the embodiments of the present application difficult to understand, the well-known power supply / ground connections with other components can or can not be shown in the provided drawings. In addition, the devices can be shown in the form of block diagrams in order to avoid making the embodiments of the present application difficult to understand, and this also takes into account the fact that the details of the implementation of these block diagram devices are highly dependent on the platform to be implemented the embodiments of the present application (i.e. these details should be fully within the understanding of those skilled in the art). In the case of setting forth specific details to describe the exemplary embodiments of the present application, it is obvious to those skilled in the art that the embodiments of the present application can be implemented without these specific details or with changes of these specific details. Therefore, these descriptions should be considered as illustrative rather than limiting.

[0104] Although the present application has been described in conjunction with the specific embodiments thereof, it is evident that many alternatives, modifications and variations will be apparent to those skilled in the art in light of the foregoing description. The embodiments of the present application intended to embrace all such alternatives, modifications and variations as fall within the scope of the appended claims. Accordingly, any omission, modification, equivalent replacement, improvement, etc. made within the spirit and principle of the embodiments of the present application should be included in the protection scope of the present application.

Claims

1. A negative electrode having a chemical potential gradient driven interface, characterized by, The negative electrode is a lithium boride alloy negative electrode with a chemical potential gradient driven interface layer on the surface thereof; The chemical potential gradient driven interface layer is prepared by comprising the following steps: S1, polymerization coupling: under an inert atmosphere, molecules in an electrolyte are adsorbed to the surface of a lithium boride alloy negative electrode by electrostatic force to form a connecting interface; S2, orientation recombination: an electric field is used to induce the ordered arrangement of electron-deficient boron sites at the interface in step S1, and a chemical potential gradient driven chemical reaction of the lithium boride alloy is induced; S3, in-situ growth: the lithium boride alloy after the reaction is left to dry to form a chemical potential gradient driven interface layer.

2. The negative electrode according to claim 1, characterized by In step S1, the electrolyte comprises a lithium salt, a solvent and an additive; the additive comprises a lithium salt-based boron compound.

3. The negative electrode according to claim 2, characterized by The lithium salt comprises at least one of lithium hexafluorophosphate, lithium tetrafluoroborate and lithium bisfluorosulfonylimide; the concentration of the lithium salt in the electrolyte is 0.1-2.0 mol / L.

4. The negative electrode according to claim 2, characterized by The lithium salt-based boron compound comprises at least one of lithium bisoxalate borate, lithium difluorooxalate borate and lithium trifluoro(perfluoro-t-butoxy) borate; the addition amount of the lithium salt-based boron compound is 0.01w%-5w% of the total mass of the electrolyte.

5. The negative electrode according to claim 1, wherein The atomic ratio of lithium to boron in the lithium boride alloy is 90-99.5:0.5-10; the thickness of the chemical potential gradient driven interface layer is 600 nm-10 μm.

6. The negative electrode according to claim 1, wherein In step S1, the ambient temperature of the electrostatic force is 20-25℃, and the distance between the electrostatic field generator and the electrode is 1-10 cm.

7. The negative electrode according to claim 1, wherein In step S2, the method of induction comprises electric field regulation; the electric field strength of the electric field regulation is 80-120 V / m, and the ambient temperature is 15-35℃.

8. The negative electrode according to claim 1, wherein In step S3, the standing time is 30 min-5 h, and the drying temperature is 60-120℃.

9. A lithium metal battery having a chemical potential gradient driven interface, characterized in that, The lithium metal battery comprises a positive electrode, an electrolyte, a separator and the negative electrode as claimed in any one of claims 1-8.

10. Use of the lithium metal battery with the chemical potential gradient driven interface as claimed in claim 9 in the preparation of an electrically powered aircraft product.

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