Electrolyte containing protein additive, preparation method and application thereof, and secondary battery

Abstract

The invention provides an electrolyte containing a protein additive, a preparation method and application of the electrolyte, and a secondary battery. The electrolyte containing the protein additive comprises the protein additive, a non-aqueous solvent and metal salt, and the protein additive comprises one or more of bovine serum albumin, gelatin, whey protein, silk fibroin, casein and antibody protein. According to the electrolyte containing the protein additive provided by the invention, a metal negative electrode can be uniformly deposited and stripped in the circulation process through the tip adsorption effect of the protein additive, and the surface of the metal negative electrode tends to be rearranged with a flatter structure, so that the formation of dendritic crystals is inhibited; and meanwhile, the specific protein can form uniform and compact SEI and CEI layers on the surface of the electrode in the circulation process, so that the cycle life of the battery is effectively prolonged.

Description

Technical Field

[0001] This invention belongs to the field of secondary battery technology, and relates to an electrolyte containing protein additives, its preparation method, application, and secondary battery. Background Technology

[0002] Sodium batteries are made from sodium metal, which is abundant on Earth, and have a high theoretical capacity (~1166 mAh·g). -1 Sodium batteries, with their low electrode potential (-2.714V), are gradually becoming strong competitors to lithium batteries. However, although sodium batteries can achieve 863~1876Wh·kg⁻¹, they are still relatively weak. -1 While it boasts theoretical advantages in terms of energy density, it still faces a series of challenges in practical applications.

[0003] First, sodium ions are larger than lithium ions, making their intercalation and deintercalation processes in electrode materials relatively difficult. This can lead to interfacial instability and uneven sodium deposition / stripping, resulting in lower energy density and poorer cycle performance. Second, the interfacial reaction between the electrode and the electrolyte not only affects the sodium ion transport efficiency but may also cause interfacial instability due to uncontrolled side reactions, leading to battery capacity decay. Furthermore, sodium metal electrodes tend to transform to lower energy crystal planes during charge and discharge, causing uneven sodium ion aggregation and dendrite growth in the electrode material. This not only affects cycle stability but may also lead to safety issues such as short circuits. Therefore, in-depth research into the interfacial problems of sodium batteries during cycling and finding effective solutions are not only key to improving sodium battery performance but also necessary for promoting their commercial application.

[0004] Current technologies employ various strategies to address interface issues, thereby improving battery energy density and cycle life. The main methods include: 1) optimizing electrolyte composition; 2) improving electrode structure; 3) optimizing the SEI layer through interface engineering; and 4) utilizing electrochemical pulses to regulate sodium ion deposition behavior. Among these, introducing additives into the sodium battery electrolyte is the simplest and most effective solution, generally including dendrite growth inhibitors and SEI forming agents. Dendrite growth inhibitors mainly include nanomaterials (such as graphene and carbon nanotubes) that form physical barriers on the electrode surface, and ester compounds (such as tris(trimethylsilane)phosphite (TMSPI) and vinylene carbonate (VC)) that promote uniform current distribution by increasing electrolyte viscosity. SEI forming agents mainly include organic solvents that promote good SEI formation (such as ethylene carbonate (EC) and dimethyl carbonate (DMC),) and fluorides and salts that improve the mechanical strength and ionic conductivity of the SEI layer.

[0005] For example, reference 1 describes adding three additives to a sodium-ion battery electrolyte. Through the synergistic effect of these three additives, a uniform and stable SEI film is formed, inhibiting the decomposition of the sodium-ion battery electrolyte, reducing the impedance of the sodium-ion battery, and improving cycle performance. The first additive is a non-sodium metal cation compound, the second is a halogenated organic ester compound, and the third is TMSPI and VC, etc. Reference 2 discloses a sodium-ion battery electrolyte containing additives including basic additives and orthoesters. Through the combined effect of these two, the electrode-electrolyte interface is improved, a stable SEI layer is formed, and the growth of sodium dendrites and dead sodium is inhibited. However, existing additives often require multiple additives to work synergistically, and these chemical additives not only have single effects and unstable performance, but also cause environmental pollution.

[0006] Therefore, exploring environmentally friendly additives that can simultaneously inhibit dendrite growth and promote the formation of an effective SEI layer is crucial for the preparation of high-rate, long-cycle stable sodium batteries.

[0007] References:

[0008] Reference 1: CN120600916A

[0009] Reference 2: CN117219855A Summary of the Invention

[0010] The problem the invention aims to solve

[0011] Based on the problems existing in the prior art, the present invention provides an electrolyte with specific additives that are environmentally friendly and biocompatible, and can simultaneously inhibit dendrite growth and promote the formation of an effective SEI (solid electrolyte interphase) layer to improve the cycle life of the battery.

[0012] Solution for solving the problem

[0013] In nature, proteins possess an inherent tip adsorption effect, meaning that the local electric field and chemical environment in protein tip or sharp edge regions may differ from that on flat surfaces, leading to increased protein concentration in these areas. The inventors discovered that this characteristic can influence the distribution of the electric field on the electrode surface, reducing current density at tips and minimizing local supersaturation, thereby reducing dendrite nucleation and growth at tips. Furthermore, the adsorption layer formed by proteins with specific structures on the electrode surface can participate in the formation of the SEI (solid electrolyte interphase) and CEI (positive electrode electrolyte interphase) during cycling, effectively improving battery cycle performance.

[0014] The electrolyte containing protein additives provided by this invention can achieve uniform deposition and stripping of the metal anode during cycling through the tip adsorption effect of the protein additives, and rearrange the surface of the metal anode towards a more flat structure, thereby inhibiting dendrite formation. At the same time, specific proteins can form uniform and dense SEI and CEI layers on the electrode surface during cycling, thereby effectively improving the cycle life of the battery.

[0015] The present invention first provides an electrolyte containing protein additives, comprising protein additives, non-aqueous solvents and metal salts, wherein the protein additives include one or more of bovine serum albumin, gelatin, whey protein, silk fibroin, casein and antibody proteins.

[0016] According to the electrolyte of the present invention, the content of the protein additive is 0.05~0.5wt% of the total mass of the electrolyte.

[0017] According to the electrolyte of the present invention, the non-aqueous solvent includes one or more of diethylene glycol dimethyl ether, diethylene glycol dimethyl ether, ethylene glycol dimethyl ether, dioxolane, propylene carbonate, ethylene carbonate, dimethyl carbonate, diethyl carbonate, diethyl carbonate, methyl ethyl carbonate, N-methylpyrrolidone, dimethyl thionamide, acetonitrile, and dimethyl carbonate.

[0018] According to the electrolyte of the present invention, the metal salt includes one or more of sodium salt, lithium salt and potassium salt.

[0019] According to the electrolyte of the present invention, the sodium salt is selected from one or more of sodium hexafluorophosphate, sodium bis(fluorosulfonyl)imide, sodium trifluoromethanesulfonate, and sodium perchlorate; the lithium salt is selected from one or more of lithium bis(trifluoromethanesulfonyl)imide, lithium trifluoromethanesulfonate, lithium bis(fluorosulfonyl)imide, lithium perchlorate, lithium difluorophosphate, lithium hexafluorophosphate, lithium nitrate, lithium difluorooxalateborate, and lithium bis(oxalateborate); and the potassium salt is selected from one or more of potassium hexafluorophosphate, potassium bis(fluorosulfonyl)imide, and potassium bis(trifluoromethanesulfonyl)imide.

[0020] According to the electrolyte of the present invention, the concentration of the metal salt in the electrolyte is 0.5~2 mol / L.

[0021] The present invention also provides a method for preparing an electrolyte containing protein additives according to the present invention, which includes the following steps: mixing and stirring a protein additive, a non-aqueous solvent and a metal salt to obtain an electrolyte containing protein additives.

[0022] According to the preparation method of the present invention, the stirring temperature is 20~40℃ and the stirring time is 12~48h;

[0023] The stirring process further includes an ultrasonic step, the ultrasonication time being 0-30 minutes.

[0024] The present invention also provides the application of the electrolyte containing protein additives according to the present invention in the preparation of secondary batteries, preferably in the preparation of high-rate secondary batteries, wherein the high-rate range is 0.5~100C.

[0025] The present invention further provides a secondary battery comprising a positive electrode, a negative electrode and an electrolyte, wherein the electrolyte comprises an electrolyte containing protein additives according to the present invention, and preferably, the secondary battery is a sodium secondary battery.

[0026] The effects of the invention

[0027] The electrolyte provided by this invention is the first to use green and sustainable protein materials as electrolyte additives. Utilizing the inherent tip adsorption effect of proteins, dendrite formation on the sodium metal anode can be effectively suppressed during cycling. Simultaneously, specific proteins can form uniform and dense SEI and CEI layers on the electrode surface during cycling, thereby effectively improving the battery's cycle performance. Furthermore, the electrolyte containing protein additives can be matched with different anodes for application at high rates.

[0028] The electrolyte preparation method provided by this invention is simple and suitable for industrial production. It can be used in sodium metal batteries, sodium-ion batteries, lithium metal batteries, lithium-ion batteries, potassium metal batteries, potassium-ion batteries, and other secondary high-energy-density batteries (such as lithium-sulfur batteries, lithium-air batteries, sodium-sulfur batteries, etc.). Attached Figure Description

[0029] Figure 1 Figure a shows the XRD pattern of the sodium electrode surface after 10 cycles of the sodium metal symmetric cell obtained in Example 1 and Comparative Example 1.

[0030] Figure 1 Figure b shows the XRD pattern of the sodium electrode surface after 50 cycles of the sodium metal symmetric cell obtained in Example 1 and Comparative Example 1.

[0031] Figure 2 The image shows SEM images of the surface and cross-section of the sodium metal anode after 200 cycles of the sodium metal symmetric cells obtained in Example 1 and Comparative Example 1.

[0032] Figure 3 Figure a shows the cycle performance test graph of the sodium metal batteries obtained in Example 1 and Comparative Example 1 at 0.5C-100C;

[0033] Figure 3Figure b shows the cycle performance test graph of the sodium metal batteries obtained in Example 1 and Comparative Example 1 at 10C;

[0034] Figure 3 Figure c shows the cycle performance test graph of the sodium metal batteries obtained in Example 1 and Comparative Example 1 at 50C;

[0035] Figure 3 Figure d shows the cycle performance test graph of the sodium-ion batteries obtained in Example 8 and Comparative Example 4 at 5C. Detailed Implementation

[0036] Various exemplary embodiments, features, and aspects of the present invention will be described in detail below. The term "exemplary" as used herein means "serving as an example, embodiment, or illustration." Any embodiment described herein as "exemplary" is not necessarily to be construed as superior to or better than other embodiments.

[0037] Furthermore, to better illustrate the present invention, numerous specific details are set forth in the following detailed embodiments. Those skilled in the art should understand that the present invention can be practiced without certain specific details. In other instances, methods, means, apparatus, and steps well known to those skilled in the art have not been described in detail in order to highlight the spirit of the present invention.

[0038] Unless otherwise stated, all units used in this specification are international standard units, and all numerical values ​​and ranges appearing in this invention should be understood to include systematic errors that are unavoidable in industrial production.

[0039] In this specification, the word "may" has two meanings: to perform a certain process and not to perform a certain process.

[0040] In this specification, references to "some specific / preferred embodiments," "other specific / preferred embodiments," "implementation," etc., refer to specific elements (e.g., features, structures, properties, and / or characteristics) related to that embodiment, which are included in at least one of the embodiments described herein and may or may not be present in other embodiments. Furthermore, it should be understood that these elements may be combined in any suitable manner in various embodiments.

[0041] In this specification, the range of values ​​referred to as "value A to value B" refers to the range including the endpoint values ​​A and B.

[0042] In this instruction manual, "room temperature" is used to indicate a temperature range of 20~25℃.

[0043] <First Aspect>

[0044] A first aspect of the present invention provides an electrolyte containing a protein additive, comprising the protein additive, a non-aqueous solvent, and a metal salt. By introducing a protein additive into a conventional electrolyte, the present invention utilizes the tip adsorption effect of specific protein additives to suppress dendrite formation while promoting the formation of an effective SEI layer, thereby improving the cycle life of the battery.

[0045] In some specific embodiments, the electrolyte containing protein additives is composed of protein additives, non-aqueous solvents, and metal salts.

[0046] The protein additives of this invention include one or more of bovine serum albumin, gelatin, whey protein, silk fibroin, casein, and antibody proteins, with bovine serum albumin being preferred. These protein additives not only exhibit a tip adsorption effect but also form a uniform and dense SEI and CEI layer on the electrode surface during battery cycling.

[0047] The protein additive of this invention comprises 0.05-0.5 wt% of the total mass of the electrolyte, preferably 0.05-0.3 wt%, for example, 0.1 wt%, 0.15 wt%, 0.2 wt%, 0.25 wt%, 0.3 wt%, 0.35 wt%, 0.4 wt%, 0.45 wt%, etc. When the protein additive content is too high, it leads to poor dispersibility of the protein additive, failing to effectively improve battery cycle life. The protein additive of this invention achieves an effective improvement in battery cycle life with only a very small amount added.

[0048] The present invention does not particularly limit the type of non-aqueous solvent, and it can be selected as needed. In some specific embodiments, the non-aqueous solvent may include one or more of the following: diethylene glycol dimethyl ether, diethylene glycol dimethyl ether, dioxolane, propylene carbonate, ethylene carbonate (EC), dimethyl carbonate (DMC), diethyl carbonate, methyl ethyl carbonate (EMC), N-methylpyrrolidone, dimethyl thionamide, acetonitrile, and dimethyl carbonate.

[0049] The metal salts of the present invention may include one or more of sodium salts, lithium salts, and potassium salts. Specifically, the sodium salt may be selected from one or more of sodium hexafluorophosphate (NaPF6), sodium bis(fluorosulfonyl)imide (NaFSI), sodium trifluoromethanesulfonate (NaCF3SO3), sodium perchlorate (NaClO4), etc.; the lithium salt may be selected from one or more of lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), lithium trifluoromethanesulfonate (LiCF3SO3), lithium bis(fluorosulfonyl)imide (LiFSI), lithium perchlorate (LiClO4), lithium difluorophosphate (LiPO2F2), lithium hexafluorophosphate (LiPF6), lithium nitrate (LiNO3), lithium difluorooxalate borate (LiDFOB), lithium bis(oxalate borate) borate (LiBOB), etc.; the potassium salt may be selected from one or more of potassium hexafluorophosphate (KPF6), potassium bis(fluorosulfonyl)imide (KFSI), potassium bis(trifluoromethanesulfonyl)imide (KTFSI), etc. Preferably, the metal salt can be a sodium salt.

[0050] In some specific implementations, the concentration of the metal salt can be 0.5~2 mol / L, for example, 0.8 mol / L, 1 mol / L, 1.2 mol / L, 1.5 mol / L, 1.8 mol / L, etc.

[0051] <Second aspect>

[0052] A second aspect of the present invention provides a method for preparing an electrolyte according to the first aspect, comprising the following steps: mixing and stirring a protein additive, a non-aqueous solvent and a metal salt to obtain an electrolyte containing the protein additive.

[0053] The types and amounts of the protein additives, non-aqueous solvents, and metal salts are the same as those described in the first aspect, and will not be repeated here.

[0054] In some specific implementations, the stirring temperature can be 20~40℃, for example, 25℃, 30℃, 35℃, etc.; the stirring time can be 12~48h, for example, 15h, 20h, 24h, 30h, 36h, 40h, 45h, etc.

[0055] In some preferred embodiments, in order to better disperse the protein additive, the stirring may be followed by an ultrasonic step, the ultrasonic time of which may be 0 to 30 minutes, for example, 5 minutes, 10 minutes, 15 minutes, 20 minutes, 25 minutes, etc.

[0056] <Third aspect>

[0057] A third aspect of the present invention provides the application of the electrolyte according to the first aspect in the preparation of secondary batteries, particularly in the preparation of high-rate secondary batteries, wherein the high-rate range can be 0.5~100C, for example, 1C, 2C, 3C, 4C, 5C, 10C, 15C, 20C, 25C, 30C, 50C, etc.

[0058] The secondary battery described in this invention can be a sodium metal battery, a sodium-ion battery, a lithium metal battery, a lithium-ion battery, a potassium metal battery, a potassium-ion battery, or other secondary high-energy-density batteries. Among them, the secondary high-energy-density batteries can be sodium-sulfur batteries, lithium-sulfur batteries, lithium-air batteries, etc.

[0059] <Fourth Aspect>

[0060] A fourth aspect of the present invention provides a secondary battery comprising a positive electrode, a negative electrode, and an electrolyte, wherein the electrolyte comprises an electrolyte containing a protein additive as described in the first aspect.

[0061] In this invention, metallic sodium, metallic sodium alloy, metallic lithium, metallic lithium alloy, metallic potassium, or metallic potassium alloy can be directly used as the positive electrode. The positive electrode can also include a positive electrode current collector and a positive electrode material, wherein the positive electrode material includes a positive electrode active material, a conductive agent, and a binder.

[0062] In some specific implementations, the positive electrode active material may include one or more of the following: sodium vanadium phosphate (Na3V2(PO4)3), vanadium pentoxide (V2O5), sodium manganese oxide, sodium ferrous fluorophosphate (Na2FePO4F), lithium iron phosphate (LiFeO4), lithium nickel cobalt aluminum oxide (NCA), lithium-rich layered oxides (LLOs), lithium cobalt oxide (LiCoO2), lithium nickel cobalt manganese oxide, lithium manganese oxide, lithium manganese oxide, lithium nickel manganese oxide, lithium manganese iron phosphate, lithium nickel oxide, potassium molybdate (KMoO2), ferrite, vanadate (VS4), and Prussian blue.

[0063] The present invention does not impose any particular limitation on the types of conductive agents and binders, and they can be selected as needed. For example, the conductive agent may include Super P, and the binder may include polyvinylidene fluoride (PVDF), etc.

[0064] In some preferred embodiments, based on a total mass of 100wt% of the positive electrode material, the mass percentage of the positive electrode active material is 50-90wt%; the mass percentage of the conductive agent is 5-30wt%; and the mass percentage of the binder is 1-15wt%.

[0065] The present invention does not impose any particular limitation on the type of positive current collector, which can be selected as needed, such as aluminum foil.

[0066] In some specific implementations, the positive electrode can be prepared using the following methods:

[0067] (1) A positive electrode coating is obtained by mixing positive electrode active material, conductive agent, binder and solvent in a certain proportion;

[0068] (2) The positive electrode coating is applied to the surface of the positive electrode current collector and dried to obtain the positive electrode.

[0069] The present invention does not impose any particular limitation on the type and amount of the solvent, which can be selected as needed, for example, N-methylpyrrolidone (NMP). The solvent is mainly used to adjust the viscosity of the coating; as long as the viscosity is adjusted to a suitable range, it is acceptable.

[0070] In this invention, metallic sodium, metallic sodium alloy, metallic lithium, metallic lithium alloy, metallic potassium, or metallic potassium alloy can be directly used as the negative electrode. The negative electrode can also include a negative electrode current collector and a negative electrode material, wherein the negative electrode material includes a negative electrode active material, a conductive agent, and a binder.

[0071] In some specific implementations, the negative electrode active material may include one or more of the following: sodium metal, sodium alloy, hard carbon, soft carbon, titanate, lithium metal, lithium alloy, silicon-carbon composite material, lithium titanate, graphite, lithium metal nitride, antimony oxide, germanium-carbon composite material, lithium titanium oxide, potassium metal, potassium alloy, and styrene.

[0072] The present invention does not impose any particular limitation on the types of conductive agents and binders, and they can be selected as needed. For example, the conductive agent may include Super P, and the binder may include polyvinylidene fluoride (PVDF), etc.

[0073] In some preferred embodiments, based on a total mass of 100wt% of the negative electrode material, the mass percentage of the negative electrode active material can be 35-85wt%, the mass percentage of the conductive agent can be 5-30wt%, and the mass percentage of the binder can be 5-20wt%.

[0074] The present invention does not impose any particular limitation on the type of positive current collector, which can be selected as needed, such as copper foil.

[0075] In some specific implementations, the negative electrode can be prepared using the following methods:

[0076] (1) A negative electrode coating is obtained by mixing the negative electrode active material, conductive agent, binder and solvent in a certain proportion;

[0077] (2) The negative electrode coating is applied to the surface of the negative electrode current collector and dried to obtain the negative electrode.

[0078] The present invention does not impose any particular limitation on the type and amount of the solvent, which can be selected as needed, for example, N-methylpyrrolidone (NMP). The solvent is mainly used to adjust the viscosity of the coating; as long as the viscosity is adjusted to a suitable range, it is acceptable.

[0079] Example

[0080] The embodiments of the present invention will be described in detail below with reference to examples. However, those skilled in the art will understand that the following examples are for illustrative purposes only and should not be considered as limiting the scope of the invention. Unless otherwise specified in the examples, conventional conditions or conditions recommended by the manufacturer are followed. Reagents or instruments whose manufacturers are not specified are all commercially available conventional products.

[0081] I. Preparation and Assembly of Sodium Metal Batteries

[0082] Example 1

[0083] Electrolyte preparation: In an argon-filled glove box (moisture content < 1 ppm, oxygen content < 1 ppm), NaPF6 and diethylene glycol dimethyl ether were mixed to prepare a 1 mol / L NaPF6 solution.

[0084] Preparation of electrolyte containing protein additives: In an argon-filled glove box (moisture content < 1 ppm, oxygen content < 1 ppm), bovine serum albumin (BSA) was added to the electrolyte at a mass ratio of 0.1%, and the mixture was stirred continuously at room temperature for 24 h to obtain an electrolyte containing protein additives.

[0085] Assembly of sodium metal symmetric cells: Sodium metal is used as the positive and negative electrodes and assembled with an electrolyte containing protein additives to obtain sodium metal symmetric cells.

[0086] Assembly of sodium metal battery: 200 mg of sodium vanadium phosphate (Na3V2(PO4)3, NVP) and 25 mg of conductive agent acetylene black were uniformly ground for 40 min; 25 mg of binder polyvinylidene fluoride and 200 μL of 1-methyl-2-pyrrolidone were added and uniformly ground for 40 min; the mixture was then coated onto the surface of aluminum foil and dried at 80 °C under vacuum for 8 h to obtain the positive electrode material (the compaction density of the active material is 2.8 mg / cm³). 2 The positive electrode is cut into a circular piece with a diameter of 1.2 mm, and sodium metal (Na) is used as the negative electrode. Sodium metal batteries are assembled using an electrolyte containing protein additives.

[0087] Comparative Example 1

[0088] Electrolyte preparation: In an argon-filled glove box (moisture content < 1 ppm, oxygen content < 1 ppm), NaPF6 and diethylene glycol dimethyl ether were mixed to prepare a 1 mol / L NaPF6 solution.

[0089] Assembly of sodium metal symmetric cells: Sodium metal is used as the positive and negative electrodes and assembled with an electrolyte to obtain a sodium metal symmetric cell.

[0090] Assembly of sodium metal battery: 200 mg of sodium vanadium phosphate (Na3V2(PO4)3, NVP) and 25 mg of conductive agent acetylene black were uniformly ground for 40 min; 25 mg of binder polyvinylidene fluoride and 200 μL of 1-methyl-2-pyrrolidone were added and uniformly ground for 40 min; the mixture was then coated onto the surface of aluminum foil and dried at 80 °C under vacuum for 8 h to obtain the positive electrode material (the compaction density of the active material is 2.8 mg / cm³). 2 The positive electrode is cut into a circular piece with a diameter of 1.2 mm, and sodium metal (Na) is used as the negative electrode. Sodium metal batteries are assembled using electrolyte.

[0091] Comparative Example 2

[0092] Electrolyte preparation: In an argon-filled glove box (moisture content < 1 ppm, oxygen content < 1 ppm), NaPF6 and diethylene glycol dimethyl ether were mixed to prepare a 1 mol / L NaPF6 solution.

[0093] Preparation of electrolyte containing protein additives: In an argon-filled glove box (moisture content < 1 ppm, oxygen content < 1 ppm), sericin was added to the electrolyte at a mass ratio of 0.05%, and the mixture was stirred continuously at room temperature for 24 h to obtain an electrolyte containing protein additives.

[0094] Assembly of sodium metal symmetric cells: Sodium metal is used as the positive and negative electrodes and assembled with an electrolyte containing protein additives to obtain sodium metal symmetric cells.

[0095] Assembly of sodium metal battery: 200 mg of sodium vanadium phosphate (Na3V2(PO4)3, NVP) and 25 mg of conductive agent acetylene black were uniformly ground for 40 min; 25 mg of binder polyvinylidene fluoride and 200 μL of 1-methyl-2-pyrrolidone were added and uniformly ground for 40 min; the mixture was then coated onto the surface of aluminum foil and dried at 80 °C under vacuum for 8 h to obtain the positive electrode material (the compaction density of the active material is 2.8 mg / cm³). 2 The positive electrode is cut into a circular piece with a diameter of 1.2 mm, and sodium metal (Na) is used as the negative electrode. Sodium metal batteries are assembled using an electrolyte containing protein additives.

[0096] Comparative Example 3

[0097] Electrolyte preparation: In an argon-filled glove box (moisture content < 1 ppm, oxygen content < 1 ppm), NaPF6 and diethylene glycol dimethyl ether were mixed to prepare a 1 mol / L NaPF6 solution.

[0098] Preparation of electrolyte containing protein additives: In an argon-filled glove box (moisture content < 1 ppm, oxygen content < 1 ppm), bovine serum albumin (BSA) was added to the electrolyte at a mass ratio of 1%, and the mixture was stirred continuously at room temperature for 24 h to obtain an electrolyte containing protein additives.

[0099] Assembly of sodium metal symmetric cells: Sodium metal is used as the positive and negative electrodes and assembled with an electrolyte containing protein additives to obtain sodium metal symmetric cells.

[0100] Assembly of sodium metal battery: 200 mg of sodium vanadium phosphate (Na3V2(PO4)3, NVP) and 25 mg of conductive agent acetylene black were uniformly ground for 40 min; 25 mg of binder polyvinylidene fluoride and 200 μL of 1-methyl-2-pyrrolidone were added and uniformly ground for 40 min; the mixture was then coated onto the surface of aluminum foil and dried at 80 °C under vacuum for 8 h to obtain the positive electrode material (the compaction density of the active material is 2.8 mg / cm³). 2 The positive electrode is cut into a circular piece with a diameter of 1.2 mm, and sodium metal (Na) is used as the negative electrode. Sodium metal batteries are assembled using an electrolyte containing protein additives.

[0101] Example 2

[0102] Electrolyte preparation: In an argon-filled glove box (moisture content < 1 ppm, oxygen content < 1 ppm), NaPF6 and diethylene glycol dimethyl ether were mixed to prepare a 1 mol / L NaPF6 solution.

[0103] Preparation of electrolyte containing protein additives: In an argon-filled glove box (moisture content < 1 ppm, oxygen content < 1 ppm), bovine serum albumin (BSA) was added to the electrolyte at a mass ratio of 0.05%, and the mixture was stirred continuously at room temperature for 24 h to obtain an electrolyte containing protein additives.

[0104] Assembly of sodium metal symmetric cells: Sodium metal is used as the positive and negative electrodes and assembled with an electrolyte containing protein additives to obtain sodium metal symmetric cells.

[0105] Assembly of sodium metal battery: 200 mg of sodium vanadium phosphate (Na3V2(PO4)3, NVP) and 25 mg of conductive agent acetylene black were uniformly ground for 40 min; 25 mg of binder polyvinylidene fluoride and 200 μL of 1-methyl-2-pyrrolidone were added and uniformly ground for 40 min; the mixture was then coated onto the surface of aluminum foil and dried at 80 °C under vacuum for 8 h to obtain the positive electrode material (the compaction density of the active material is 2.8 mg / cm³). 2 The positive electrode is cut into a circular piece with a diameter of 1.2 mm, and sodium metal (Na) is used as the negative electrode. Sodium metal batteries are assembled using an electrolyte containing protein additives.

[0106] Example 3

[0107] Electrolyte preparation: In an argon-filled glove box (moisture content < 1 ppm, oxygen content < 1 ppm), NaPF6 and diethylene glycol dimethyl ether were mixed to prepare a 1 mol / L NaPF6 solution.

[0108] Preparation of electrolyte containing protein additives: In an argon-filled glove box (moisture content < 1 ppm, oxygen content < 1 ppm), bovine serum albumin (BSA) was added to the electrolyte at a mass ratio of 0.3%, and the mixture was stirred continuously at room temperature for 24 h to obtain an electrolyte containing protein additives.

[0109] Assembly of sodium metal symmetric cells: Sodium metal is used as the positive and negative electrodes and assembled with an electrolyte containing protein additives to obtain sodium metal symmetric cells.

[0110] Assembly of sodium metal battery: 200 mg of sodium vanadium phosphate (Na3V2(PO4)3, NVP) and 25 mg of conductive agent acetylene black were uniformly ground for 40 min; 25 mg of binder polyvinylidene fluoride and 200 μL of 1-methyl-2-pyrrolidone were added and uniformly ground for 40 min; the mixture was then coated onto the surface of aluminum foil and dried at 80 °C under vacuum for 8 h to obtain the positive electrode material (the compaction density of the active material is 2.8 mg / cm³). 2 The positive electrode is cut into a circular piece with a diameter of 1.2 mm, and sodium metal (Na) is used as the negative electrode. Sodium metal batteries are assembled using an electrolyte containing protein additives.

[0111] Example 4

[0112] Electrolyte preparation: In an argon-filled glove box (moisture content < 1 ppm, oxygen content < 1 ppm), NaPF6 and diethylene glycol dimethyl ether were mixed to prepare a 1 mol / L NaPF6 solution.

[0113] Preparation of electrolyte containing protein additives: In an argon-filled glove box (moisture content < 1 ppm, oxygen content < 1 ppm), bovine serum albumin (BSA) was added to the electrolyte at a mass ratio of 0.5%, and the mixture was stirred continuously at room temperature for 24 h to obtain an electrolyte containing protein additives.

[0114] Assembly of sodium metal symmetric cells: Sodium metal is used as the positive and negative electrodes and assembled with an electrolyte containing protein additives to obtain sodium metal symmetric cells.

[0115] Assembly of sodium metal battery: 200 mg of sodium vanadium phosphate (Na3V2(PO4)3, NVP) and 25 mg of conductive agent acetylene black were uniformly ground for 40 min; 25 mg of binder polyvinylidene fluoride and 200 μL of 1-methyl-2-pyrrolidone were added and uniformly ground for 40 min; the mixture was then coated onto the surface of aluminum foil and dried at 80 °C under vacuum for 8 h to obtain the positive electrode material (the compaction density of the active material is 2.8 mg / cm³). 2 The positive electrode is cut into a circular piece with a diameter of 1.2 mm, and sodium metal (Na) is used as the negative electrode. Sodium metal batteries are assembled using an electrolyte containing protein additives.

[0116] Example 5

[0117] Electrolyte preparation: In an argon-filled glove box (moisture content < 1 ppm, oxygen content < 1 ppm), NaPF6 and diethylene glycol dimethyl ether were mixed to prepare a 1 mol / L NaPF6 solution.

[0118] Preparation of electrolyte containing protein additives: In an argon-filled glove box (moisture content < 1 ppm, oxygen content < 1 ppm), gelatin was added to the electrolyte at a mass ratio of 0.1%, and the mixture was stirred continuously at room temperature for 24 h to obtain an electrolyte containing protein additives.

[0119] Assembly of sodium metal symmetric cells: Sodium metal is used as the positive and negative electrodes and assembled with an electrolyte containing protein additives to obtain sodium metal symmetric cells.

[0120] Assembly of sodium metal battery: 200 mg of sodium vanadium phosphate (Na3V2(PO4)3, NVP) and 25 mg of conductive agent acetylene black were uniformly ground for 40 min; 25 mg of binder polyvinylidene fluoride and 200 μL of 1-methyl-2-pyrrolidone were added and uniformly ground for 40 min; the mixture was then coated onto the surface of aluminum foil and dried at 80 °C under vacuum for 8 h to obtain the positive electrode material (the compaction density of the active material is 2.8 mg / cm³). 2 The positive electrode is cut into a circular piece with a diameter of 1.2 mm, and sodium metal (Na) is used as the negative electrode. Sodium metal batteries are assembled using an electrolyte containing protein additives.

[0121] Example 6

[0122] Electrolyte preparation: In an argon-filled glove box (moisture content < 1 ppm, oxygen content < 1 ppm), NaPF6 and diethylene glycol dimethyl ether were mixed to prepare a 1 mol / L NaPF6 solution.

[0123] Preparation of electrolyte containing protein additives: In an argon-filled glove box (moisture content < 1 ppm, oxygen content < 1 ppm), casein was added to the electrolyte at a mass ratio of 0.1%, and the mixture was stirred continuously at room temperature for 24 h to obtain an electrolyte containing protein additives.

[0124] Assembly of sodium metal symmetric cells: Sodium metal is used as the positive and negative electrodes and assembled with an electrolyte containing protein additives to obtain sodium metal symmetric cells.

[0125] Assembly of sodium metal battery: 200 mg of sodium vanadium phosphate (Na3V2(PO4)3, NVP) and 25 mg of conductive agent acetylene black were uniformly ground for 40 min; 25 mg of binder polyvinylidene fluoride and 200 μL of 1-methyl-2-pyrrolidone were added and uniformly ground for 40 min; the mixture was then coated onto the surface of aluminum foil and dried at 80 °C under vacuum for 8 h to obtain the positive electrode material (the compaction density of the active material is 2.8 mg / cm³). 2 The positive electrode is cut into a circular piece with a diameter of 1.2 mm, and sodium metal (Na) is used as the negative electrode. Sodium metal batteries are assembled using an electrolyte containing protein additives.

[0126] Example 7

[0127] Electrolyte preparation: In an argon-filled glove box (moisture content < 1 ppm, oxygen content < 1 ppm), NaPF6 and diethylene glycol dimethyl ether were mixed to prepare a 1 mol / L NaPF6 solution.

[0128] Preparation of electrolyte containing protein additives: In an argon-filled glove box (moisture content < 1 ppm, oxygen content < 1 ppm), silk fibroin was added to the electrolyte at a mass ratio of 0.1%, and the mixture was stirred continuously at room temperature for 24 h to obtain an electrolyte containing protein additives.

[0129] Assembly of sodium metal symmetric cells: Sodium metal is used as the positive and negative electrodes and assembled with an electrolyte containing protein additives to obtain sodium metal symmetric cells.

[0130] Assembly of sodium metal battery: 200 mg of sodium vanadium phosphate (Na3V2(PO4)3, NVP) and 25 mg of conductive agent acetylene black were uniformly ground for 40 min; 25 mg of binder polyvinylidene fluoride and 200 μL of 1-methyl-2-pyrrolidone were added and uniformly ground for 40 min; the mixture was then coated onto the surface of aluminum foil and dried at 80 °C under vacuum for 8 h to obtain the positive electrode material (the compaction density of the active material is 2.8 mg / cm³). 2 The positive electrode is cut into a circular piece with a diameter of 1.2 mm, and sodium metal (Na) is used as the negative electrode. Sodium metal batteries are assembled using an electrolyte containing protein additives.

[0131] Performance testing

[0132] 1. XRD test

[0133] The changes in the crystal structure of the sodium electrode surface after cycling were tested using XRD in the sodium metal symmetric batteries prepared in Example 1 and Comparative Example 1. The test results are as follows: Figure 1 As shown, where, Figure 1 In the figure, 'a' and 'b' represent the XRD test results of the sodium electrode surface after 10 and 50 cycles of the sodium metal symmetric cell, respectively.

[0134] Depend on Figure 1 It can be seen that after 10 cycles, the original sodium crystals in the sodium metal symmetric battery without protein additives (Comparative Example 1) decreased. This is because a severe side reaction occurred between sodium and the ether-based electrolyte during cycling, destroying its crystal structure. In contrast, a strong 110 crystal plane intensity was observed on the sodium anode surface of the sodium metal symmetric battery prepared with the electrolyte containing protein additives (Example 1), indicating that the introduction of protein additives can maintain the rearrangement of the 110 crystal plane. Further testing of the sodium anode surface after 50 cycles revealed that the sodium metal symmetric battery prepared with the electrolyte without protein additives (Comparative Example 1) still did not show a sodium metal crystal peak, but a corresponding peak for sodium oxide appeared; the sodium anode surface of the sodium metal symmetric battery prepared with the electrolyte containing protein additives (Example 1) showed the same result as before, namely, a large peak at the 110 crystal plane. In summary, the results show that the introduction of protein additives can not only rearrange the crystal structure of the sodium metal electrode surface and maintain it during cycling, but also effectively prevent the occurrence of side reactions.

[0135] 2. SEM testing

[0136] After 200 cycles, the sodium metal symmetric batteries obtained in Example 1 and Comparative Example 1 were subjected to SEM tests on the surface and cross-section of the sodium metal anode. The results are as follows: Figure 2 As shown.

[0137] Depend on Figure 2It can be seen that when no protein additive is added to the ether-based electrolyte, severe cracks appear on the surface of the sodium metal anode in the sodium metal symmetric cell after 200 deposition / stripping cycles, with cracks and pores in the cross-section. This phenomenon is because the loose and unstable SEI layer deteriorates with charge-discharge cycles, exposing fresh sodium metal from the cracked SEI layer, resulting in a loose and porous SEI layer and irregular sodium deposition. Conversely, the addition of protein additives makes the sodium electrode surface smooth and dense, and a denser sodium deposition layer is observed in the vertical direction.

[0138] 3. Cyclic performance test

[0139] (1) Cyclic performance tests were conducted on the sodium metal batteries obtained in Example 1 and Comparative Example 1. Specifically, a Wuhan Landian tester was used, and the battery test conditions were: 2-3.8V, 0.5C-100C, 26℃. The test results are as follows: Figure 3 As shown in 'a'; 2-3.8V, 10C, 26℃, the test results are as follows. Figure 3 As shown in b; 2-3.8V, 50C, 26℃, the test results are as follows. Figure 3 As shown in c in the figure.

[0140] Depend on Figure 3 As can be seen from 'a', compared to the electrolyte assembly battery without protein additives (Comparative Example 1), the electrolyte assembly battery with protein additives (Example 1) exhibits superior discharge capacity as the rate increases from 0.5C to 100C. Figure 3 As can be seen from b, the discharge capacity of the battery assembled with electrolyte without protein additives (Comparative Example 1) began to decrease significantly after 3000 cycles. The cycle performance of the battery assembled with electrolyte containing protein additives (Example 1) was significantly and effectively improved; its discharge capacity did not decrease significantly after 20000 cycles, and the discharge capacity after 20000 cycles was 41.3 mAh·g. -1 ;Depend on Figure 3 As can be seen from 'c', the battery assembled with electrolyte without protein additives (Comparative Example 1) exhibits rapid capacity decay after 1950 cycles, while the battery assembled with electrolyte containing protein additives (Example 1) shows significantly improved cycle performance, capable of 16000 cycles without significant capacity decay, and a discharge capacity of 31.8 mAh·g after 16000 cycles. -1 .

[0141] (2) The sodium metal batteries prepared in Comparative Examples 1-3 and Examples 1-7 were subjected to cycle performance tests. Specifically, the Wuhan Landian tester was used, and the test conditions were as follows: the longest number of cycles and the discharge capacity after 2000 cycles were tested at 2-3.8V, 10C, and 26℃; the longest number of cycles and the discharge capacity after 1000 cycles were tested at 2-3.8V, 50C, and 26℃. The test results are shown in Table 1.

[0142] Table 1

[0143]

[0144] As can be seen from Table 1, compared with the sodium metal battery without protein additive (Comparative Example 1), the sodium metal batteries prepared in Examples 1 to 7 of the present invention have excellent cycle performance at high rates (10C and 50C), indicating that adding the protein additive of the present invention can effectively improve the cycle performance of sodium metal batteries.

[0145] The protein additive added in Comparative Example 2 was sericin, which is not included in the scope of protein additives defined in this invention. Its cycle performance was worse than that of Comparative Example 1. This is because although sericin has a tip adsorption effect, its linear and loose structure makes it difficult to form a uniform and stable interface layer on the electrode surface, thus failing to improve cycle performance. In contrast, the protein additives used in this invention, such as bovine serum albumin, have a dense spherical structure and hydrophobic groups, which can form a uniform and dense SEI and CEI layer on the electrode surface through physical adsorption and selective decomposition, enabling the prepared battery to undergo stable long-term cycling. Therefore, specific protein additives are necessary to effectively improve cycle performance.

[0146] The protein additive content in Comparative Example 3 was too high, and the protein additive had poor dispersibility, resulting in a significant decrease in cycle performance.

[0147] II. Preparation and Assembly of Sodium-ion Batteries

[0148] Example 8

[0149] Electrolyte preparation: In an argon-filled glove box (moisture content < 1 ppm, oxygen content < 1 ppm), NaPF6 and diethylene glycol dimethyl ether were mixed to prepare a 1 mol / L NaPF6 solution.

[0150] Preparation of electrolyte containing protein additives: In an argon-filled glove box (moisture content < 1 ppm, oxygen content < 1 ppm), bovine serum albumin (BSA) was added to the electrolyte at a mass ratio of 0.1%, and the mixture was stirred continuously at room temperature for 24 h to obtain an electrolyte containing protein additives.

[0151] Assembly of sodium-ion batteries: Purchase commercial sodium vanadium phosphate (Na3V2(PO4)3, NVP) positive electrode sheets (the compaction density of the active material is 10.32 mg / cm³). 2 Cut into 1.2mm diameter discs, use hard carbon (HC) as the negative electrode, and assemble sodium-ion batteries using an electrolyte containing protein additives.

[0152] Comparative Example 4

[0153] Electrolyte preparation: In an argon-filled glove box (moisture content < 1 ppm, oxygen content < 1 ppm), NaPF6 and diethylene glycol dimethyl ether were mixed to prepare a 1 mol / L NaPF6 solution.

[0154] Assembly of sodium-ion batteries: Purchase commercial sodium vanadium phosphate (Na3V2(PO4)3, NVP) positive electrode sheets (the compaction density of the active material is 10.32 mg / cm³). 2 Cut into 1.2mm diameter circular pieces, use hard carbon (HC) as the negative electrode, and assemble sodium-ion batteries using electrolyte.

[0155] Comparative Example 5

[0156] Electrolyte preparation: In an argon-filled glove box (moisture content < 1 ppm, oxygen content < 1 ppm), NaPF6 and diethylene glycol dimethyl ether were mixed to prepare a 1 mol / L NaPF6 solution.

[0157] Preparation of electrolyte containing protein additives: In an argon-filled glove box (moisture content < 1 ppm, oxygen content < 1 ppm), sericin was added to the electrolyte at a mass ratio of 0.05%, and the mixture was stirred continuously at room temperature for 24 h to obtain an electrolyte containing protein additives.

[0158] Assembly of sodium-ion batteries: Purchase commercial sodium vanadium phosphate (Na3V2(PO4)3, NVP) positive electrode sheets (the compaction density of the active material is 10.32 mg / cm³). 2 Cut into 1.2mm diameter discs, use hard carbon (HC) as the negative electrode, and assemble sodium-ion batteries using an electrolyte containing protein additives.

[0159] Comparative Example 6

[0160] Electrolyte preparation: In an argon-filled glove box (moisture content < 1 ppm, oxygen content < 1 ppm), NaPF6 and diethylene glycol dimethyl ether were mixed to prepare a 1 mol / L NaPF6 solution.

[0161] Preparation of electrolyte containing protein additives: In an argon-filled glove box (moisture content < 1 ppm, oxygen content < 1 ppm), bovine serum albumin (BSA) was added to the electrolyte at a mass ratio of 1%, and the mixture was stirred continuously at room temperature for 24 h to obtain an electrolyte containing protein additives.

[0162] Assembly of sodium-ion batteries: Purchase commercial sodium vanadium phosphate (Na3V2(PO4)3, NVP) positive electrode sheets (the compaction density of the active material is 10.32 mg / cm³). 2 Cut into 1.2mm diameter discs, use hard carbon (HC) as the negative electrode, and assemble sodium-ion batteries using an electrolyte containing protein additives.

[0163] Example 9

[0164] Electrolyte preparation: In an argon-filled glove box (moisture content < 1 ppm, oxygen content < 1 ppm), NaPF6 and diethylene glycol dimethyl ether were mixed to prepare a 1 mol / L NaPF6 solution.

[0165] Preparation of electrolyte containing protein additives: In an argon-filled glove box (moisture content < 1 ppm, oxygen content < 1 ppm), bovine serum albumin (BSA) was added to the electrolyte at a mass ratio of 0.05%, and the mixture was stirred continuously at room temperature for 24 h to obtain an electrolyte containing protein additives.

[0166] Assembly of sodium-ion batteries: Purchase commercial sodium vanadium phosphate (Na3V2(PO4)3, NVP) positive electrode sheets (the compaction density of the active material is 10.32 mg / cm³). 2 Cut into 1.2mm diameter discs, use hard carbon (HC) as the negative electrode, and assemble sodium-ion batteries using an electrolyte containing protein additives.

[0167] Example 10

[0168] Electrolyte preparation: In an argon-filled glove box (moisture content < 1 ppm, oxygen content < 1 ppm), NaPF6 and diethylene glycol dimethyl ether were mixed to prepare a 1 mol / L NaPF6 solution.

[0169] Preparation of electrolyte containing protein additives: In an argon-filled glove box (moisture content < 1 ppm, oxygen content < 1 ppm), bovine serum albumin (BSA) was added to the electrolyte at a mass ratio of 0.3%, and the mixture was stirred continuously at room temperature for 24 h to obtain an electrolyte containing protein additives.

[0170] Assembly of sodium-ion batteries: Purchase commercial sodium vanadium phosphate (Na3V2(PO4)3, NVP) positive electrode sheets (the compaction density of the active material is 10.32 mg / cm³). 2Cut into 1.2mm diameter discs, use hard carbon (HC) as the negative electrode, and assemble sodium-ion batteries using an electrolyte containing protein additives.

[0171] Example 11

[0172] Electrolyte preparation: In an argon-filled glove box (moisture content < 1 ppm, oxygen content < 1 ppm), NaPF6 and diethylene glycol dimethyl ether were mixed to prepare a 1 mol / L NaPF6 solution.

[0173] Preparation of electrolyte containing protein additives: In an argon-filled glove box (moisture content < 1 ppm, oxygen content < 1 ppm), bovine serum albumin (BSA) was added to the electrolyte at a mass ratio of 0.5%, and the mixture was stirred continuously at room temperature for 24 h to obtain an electrolyte containing protein additives.

[0174] Assembly of sodium-ion batteries: Purchase commercial sodium vanadium phosphate (Na3V2(PO4)3, NVP) positive electrode sheets (the compaction density of the active material is 10.32 mg / cm³). 2 Cut into 1.2mm diameter discs, use hard carbon (HC) as the negative electrode, and assemble sodium-ion batteries using an electrolyte containing protein additives.

[0175] Example 12

[0176] Electrolyte preparation: In an argon-filled glove box (moisture content < 1 ppm, oxygen content < 1 ppm), NaPF6 and diethylene glycol dimethyl ether were mixed to prepare a 1 mol / L NaPF6 solution.

[0177] Preparation of electrolyte containing protein additives: In an argon-filled glove box (moisture content < 1 ppm, oxygen content < 1 ppm), gelatin was added to the electrolyte at a mass ratio of 0.1%, and the mixture was stirred continuously at room temperature for 24 h to obtain an electrolyte containing protein additives.

[0178] Assembly of sodium-ion batteries: Purchase commercial sodium vanadium phosphate (Na3V2(PO4)3, NVP) positive electrode sheets (the compaction density of the active material is 10.32 mg / cm³). 2 Cut into 1.2mm diameter discs, use hard carbon (HC) as the negative electrode, and assemble sodium-ion batteries using an electrolyte containing protein additives.

[0179] Example 13

[0180] Electrolyte preparation: In an argon-filled glove box (moisture content < 1 ppm, oxygen content < 1 ppm), NaPF6 and diethylene glycol dimethyl ether were mixed to prepare a 1 mol / L NaPF6 solution.

[0181] Preparation of electrolyte containing protein additives: In an argon-filled glove box (moisture content < 1 ppm, oxygen content < 1 ppm), casein was added to the electrolyte at a mass ratio of 0.1%, and the mixture was stirred continuously at room temperature for 24 h to obtain an electrolyte containing protein additives.

[0182] Assembly of sodium-ion batteries: Purchase commercial sodium vanadium phosphate (Na3V2(PO4)3, NVP) positive electrode sheets (the compaction density of the active material is 10.32 mg / cm³). 2 Cut into 1.2mm diameter discs, use hard carbon (HC) as the negative electrode, and assemble sodium-ion batteries using an electrolyte containing protein additives.

[0183] Example 14

[0184] Electrolyte preparation: In an argon-filled glove box (moisture content < 1 ppm, oxygen content < 1 ppm), NaPF6 and diethylene glycol dimethyl ether were mixed to prepare a 1 mol / L NaPF6 solution.

[0185] Preparation of electrolyte containing protein additives: In an argon-filled glove box (moisture content < 1 ppm, oxygen content < 1 ppm), silk fibroin was added to the electrolyte at a mass ratio of 0.1%, and the mixture was stirred continuously at room temperature for 24 h to obtain an electrolyte containing protein additives.

[0186] Assembly of sodium-ion batteries: Purchase commercial sodium vanadium phosphate (Na3V2(PO4)3, NVP) positive electrode sheets (the compaction density of the active material is 10.32 mg / cm³). 2 Cut into 1.2mm diameter discs, use hard carbon (HC) as the negative electrode, and assemble sodium-ion batteries using an electrolyte containing protein additives.

[0187] Performance testing

[0188] 1. Cyclic performance test

[0189] (1) The performance of the sodium-ion batteries obtained in Example 8 and Comparative Example 4 was tested. Specifically, the Wuhan Landian tester was used, and the battery test conditions were: 2.5-4V, 5C, 26℃. The test results are as follows: Figure 3 As shown by d in the diagram. Figure 3 As can be seen from d, the sodium-ion battery assembled with the electrolyte containing protein additives (Example 8) has a certain improvement in cycle performance compared with the sodium-ion battery assembled with the electrolyte without protein additives (Comparative Example 4). The sodium-ion battery obtained in Example 8 has a discharge capacity of 39 mAh·g after 1000 cycles. -1 .

[0190] (2) The sodium-ion batteries obtained in Comparative Examples 4-6 and Examples 8-14 were subjected to cycle performance tests. Specifically, the Wuhan Landian Tester was used, and the test conditions were 2.5-4V, 5C, and 26℃. The test results were shown in Table 2.

[0191] Table 2

[0192]

[0193] As can be seen from Table 2, compared with sodium-ion batteries without protein additives (Comparative Example 4), the sodium-ion batteries prepared in Examples 8-14 of this invention have better cycle performance. Their discharge capacity after 1000 cycles is higher than that of Comparative Example 4, indicating that adding the protein additives of this invention can effectively improve the cycle performance of sodium-ion batteries.

[0194] The protein additive added in Comparative Example 5 was sericin, which is not included in the scope of protein additives defined in this invention. Its discharge capacity after 1000 cycles was significantly lower than that of Comparative Example 4 without additives. It can be seen that only specific protein additives can effectively improve cycle performance. The protein additive content in Comparative Example 6 was too high and the protein additive had poor dispersibility, resulting in a significant decrease in discharge capacity after 1000 cycles.

[0195] It should be noted that although the technical solution of the present invention has been described with specific examples, those skilled in the art will understand that the present invention should not be limited thereto.

[0196] The various embodiments of the present invention have been described above. These descriptions are exemplary and not exhaustive, nor are they limited to the disclosed embodiments. Many modifications and variations will be apparent to those skilled in the art without departing from the scope and spirit of the described embodiments. The terminology used herein is chosen to best explain the principles, practical application, or technical improvements to the embodiments in the market, or to enable others skilled in the art to understand the embodiments disclosed herein.

Claims

1. An electrolyte containing a protein additive, characterized in that, It includes protein additives, non-aqueous solvents, and metal salts, wherein the protein additives include one or more of bovine serum albumin, gelatin, whey protein, silk fibroin, casein, and antibody proteins.

2. The electrolyte according to claim 1, characterized in that, The content of the protein additive is 0.05~0.5wt% of the total mass of the electrolyte.

3. The electrolyte according to claim 1 or 2, characterized in that, The non-aqueous solvent includes one or more of diethylene glycol dimethyl ether, diethylene glycol dimethyl ether, dioxolane, propylene carbonate, ethylene carbonate, dimethyl carbonate, diethyl carbonate, diethyl carbonate, methyl ethyl carbonate, N-methylpyrrolidone, dimethyl thionamide, acetonitrile, and dimethyl carbonate.

4. The electrolyte according to any one of claims 1 to 3, characterized in that, The metal salt includes one or more of sodium, lithium, and potassium salts.

5. The electrolyte according to claim 4, characterized in that, The sodium salt is selected from one or more of sodium hexafluorophosphate, sodium difluorosulfonylimide, sodium trifluoromethanesulfonate, and sodium perchlorate; the lithium salt is selected from one or more of lithium bis(trifluoromethanesulfonylimide), lithium trifluoromethanesulfonate, lithium difluorosulfonylimide, lithium perchlorate, lithium difluorophosphate, lithium hexafluorophosphate, lithium nitrate, lithium difluorooxalateborate, and lithium bis(oxalateborate); the potassium salt is selected from one or more of potassium hexafluorophosphate, potassium difluorosulfonylimide, and potassium bis(trifluoromethanesulfonyl)imide.

6. The electrolyte according to any one of claims 1 to 5, characterized in that, The concentration of the metal salt in the electrolyte is 0.5~2 mol / L.

7. A method for preparing an electrolyte containing a protein additive according to any one of claims 1 to 6, characterized in that, The process includes the following steps: mixing and stirring a protein additive, a non-aqueous solvent, and a metal salt to obtain an electrolyte containing the protein additive.

8. The preparation method according to claim 7, characterized in that, The stirring temperature is 20~40℃, and the stirring time is 12~48h; The stirring process further includes an ultrasonic step, the ultrasonication time being 0-30 minutes.

9. The application of an electrolyte containing a protein additive according to any one of claims 1 to 6 in the preparation of a secondary battery, preferably in the preparation of a high-rate secondary battery, wherein, The high-magnification range is 0.5~100C.

10. A secondary battery, characterized in that, It includes a positive electrode, a negative electrode, and an electrolyte, wherein the electrolyte includes an electrolyte containing protein additives according to any one of claims 1 to 6, and preferably, the secondary battery is a sodium secondary battery.

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