Combined electrolyte additive, non-aqueous electrolyte containing additive and application

Abstract

The invention relates to a combined electrolyte additive, a non-aqueous electrolyte containing the additive and application of the non-aqueous electrolyte in a secondary battery, and belongs to the technical field of metal secondary batteries. According to the additive, the self-repairing capacity of a positive electrode interface is enhanced through the electrochemical oxidation effect of hydrogen bond donor micromolecules, meanwhile, the side reaction of a negative electrode interface is effectively inhibited through the reduction and passivation effect of metal halide salt, and a brand new regulation and control strategy is provided for high-stability interface engineering of a metal battery. In addition, the hydrogen bond donor small molecules and polysulfide can form a stable hydrogen bond complex, the solvation structure of the electrolyte is further optimized, interfacial ion transmission is promoted, the cycle life of the sulfur-based battery is remarkably prolonged, and the rate capability of the sulfur-based battery is remarkably improved. In addition, the hydrogen bond donor micromolecules can be coordinated with metal cations in metal salt halide / chalcogenide (such as ZnCl2, ZnI2, MgS2 and the like) and the like in a solution to form a new complex which participates in formation evolution and dynamic repair of a positive and negative electrode interface layer.

Description

Technical Field

[0001] The present invention belongs to the technical field of metal secondary batteries and relates to a combined electrolyte additive and a preparation method thereof, a non-aqueous electrolyte containing the additive and applications thereof. Background Art

[0002] In recent years, metal secondary batteries represented by lithium metal batteries and sodium metal batteries have gradually become a research hotspot in the field of energy storage due to their ultra-high theoretical energy density. However, the high voltage positive electrode (≥4.5V vs.Li + The development of electrolyte systems that combine compatibility with Li / Li (anode) and stability with metal anodes still faces significant challenges. On the cathode side, traditional carbonate-based electrolytes are susceptible to oxidative decomposition at high voltages, leading to transition metal dissolution and CEI membrane rupture. On the anode side, uncontrollable dendritic growth of lithium / sodium metals and interfacial side reactions lead to low Coulombic efficiency. Existing additives such as vinylene carbonate (VC) and fluoroethylene carbonate (FEC) can improve solid electrolyte interface (SEI) membrane performance through preferential reduction, but they suffer from drawbacks such as decreased low-temperature ionic conductivity and severe gassing at high temperatures, and their effectiveness in modifying the cathode CEI membrane is limited. In recent years, eutectic electrolytes have demonstrated unique advantages due to their multi-component synergistic effects. However, traditional eutectic systems require strict control of component ratios and suffer from high viscosity, poor electrode wettability, and insufficient compatibility with metal anodes, severely hindering their industrial application. Therefore, there is an urgent need to develop novel electrolyte systems that overcome these component ratio limitations and achieve both cathode stability and compatibility with metal anodes. Summary of the Invention

[0003] In view of this, the object of the present invention is to provide a combined electrolyte additive and a preparation method thereof that can synergistically optimize the positive and negative electrode interface stability and the electrolyte solvation structure, and the non-aqueous electrolyte and secondary battery using the additive have excellent electrochemical properties.

[0004] In order to achieve the above object, the present invention provides the following technical solutions:

[0005] A combined electrolyte additive consists of a small molecule hydrogen bond donor with a high HOMO energy level and a metal compound with a low LUMO energy level. The metal compound is at least one of a metal halide or a metal oxide.

[0006] Preferably, the hydrogen bond donor small molecule is composed of one or more of amino compounds, hydroxyl-containing compounds, sulfhydryl-containing compounds, carboxylic acid compounds, amide compounds, phosphonic acid, guanidine-containing compounds, or salts of the above compounds.

[0007] Preferably, the amino compound is one or more of ammonia, aniline, urea, and amino acid; the hydroxyl-containing compound is one or more of ethylene glycol, glycerol, phenol, lactic acid, and glucose; the sulfhydryl-containing compound is one or more of thiol and thiophenol; the carboxylic acid compound is one or more of acetic acid and benzoic acid; the amide compound is one or more of acetamide and glycine dipeptide; and the guanidine-containing compound is one or more of guanidine hydrochloride, guanidine sulfamate, dodecylguanidine acetate, and guanidine phosphate.

[0008] Preferably, the salt is one or more of ethylamine hydrochloride, aniline sulfate, triethylamine citrate, sodium glutamate, and copper glutamate.

[0009] Preferably, the metal halide is one or more of ZnCl2, ZnI2, MgBr2, AlCl3, SnCl2, FeCl3, and CuBr2, and the metal sulfide is one or more of ZnS2, MgS2, AlCl3, SnS2, FeS3, and CuS2.

[0010] Preferably, the molar ratio of the hydrogen bond donor small molecule to the metal compound is 1:0.1-1:5.

[0011] A non-aqueous electrolyte comprises, by mass fraction, 0.01%-15% of an electrolyte additive, 60%-90% of an organic solvent, 5%-30% of an electrolyte lithium salt, and 0.01%-10% of other additives.

[0012] Preferably, the organic solvent is at least one of ethylene carbonate, propylene carbonate, dimethyl carbonate, ethyl methyl carbonate, γ-butyrolactone, and ethyl acetate; the electrolyte lithium salt is at least one of lithium perchlorate, sodium hexafluorophosphate, sodium bisfluorosulfonyl imide, sodium bis(trifluoromethanesulfonyl)imide, sodium perchlorate, potassium hexafluorophosphate, potassium bisfluorosulfonyl imide, potassium bis(trifluoromethanesulfonyl)imide, and potassium perchlorate; and the other additives are at least one of vinylene carbonate, fluoroethylene carbonate, lithium difluorophosphate, 1,3-propane sultone, and vinyl sulfate.

[0013] The invention discloses an application of a non-aqueous electrolyte in a metal-based non-aqueous secondary battery.

[0014] The beneficial effects of the present invention are:

[0015] The non-aqueous electrolyte additive disclosed in the present invention is composed of a small molecule hydrogen bond donor with a high HOMO energy level and a metal halide salt with a low LUMO energy level, and has the following advantages: (1) the small molecule hydrogen bond donor (such as an amino or hydroxyl compound) forms a stable complex with polysulfide or its derivatives through hydrogen bonds, effectively inhibiting the dissolution and shuttling of polysulfide or its derivatives, and reducing the loss of active sulfur. At the same time, an organic-inorganic composite CEI film containing elements such as N / O / S / P is dynamically formed to enhance the stability of the positive electrode interface; (2) Metal halide / oxygen compounds with low LUMO energy levels (such as ZnCl2, AlCl3) induce the formation of a dense passivation layer on the surface of the metal negative electrode, which contains metal sulfides, halides and other components, significantly inhibiting dendrite growth and avoiding short circuit risks; (3) High HOMO energy level hydrogen bond donors and low LUMO energy level metal halide / oxygen compounds are compounded in a specific molar ratio to form a "eutectic" system, which simultaneously covers the needs of positive and negative electrode interface repair and breaks through the functional limitations of a single additive; (4) This additive is combined with conventional electrolytic The electrolyte solvents (such as carbonates), electrolyte salts (such as LiPF6, etc.) and second additives (such as FEC, etc.) are highly compatible, the addition amount is flexible (0.01%-15%), and it is adapted to the existing battery production process; (5) the raw materials of hydrogen bond donor small molecules (such as urea, ethylene glycol) and metal salt halides (such as ZnI2) are cheap and easy to obtain, the additive amount is small (minimum 0.01%), and the overall cost is low; (6) it is particularly suitable for sulfur-based systems such as lithium-sulfur batteries and sodium-sulfur batteries, solving problems such as short cycle life and poor safety; by adjusting the types and ratios of hydrogen bond donor small molecules and metal salts / sulfur compounds, it can be customized to adapt to different electrolyte systems and electrode materials.

[0016] This patent innovatively proposes a new type of "combination" electrolyte additive, which cleverly combines a small molecule hydrogen bond donor with a high HOMO and a metal halide / oxygen compound with a low LUMO to synergistically optimize the stability of the positive and negative electrode interfaces and the electrolyte solvation structure. This system enhances the self-repair ability of the positive electrode interface through the electrochemical oxidation of the hydrogen bond donor small molecule, while effectively inhibiting the side reactions at the negative electrode interface by utilizing the reduction passivation effect of the metal halide salt, providing a new regulatory strategy for the high-stability interface engineering of metal batteries. In addition, the hydrogen bond donor small molecule can form a stable hydrogen bond complex with polysulfide, further optimizing the solvation structure of the electrolyte and promoting interfacial ion transport, thereby significantly improving the cycle life and rate performance of sulfur-based batteries. In addition, the hydrogen bond donor small molecule can also coordinate with the metal cations in the metal salt halide / oxygen compound (such as ZnCl2, ZnI2, MgBr2, etc.) in the solution to form a new complex to participate in the formation, evolution and dynamic repair of the positive and negative electrode interface layer.

[0017] Other advantages, objects, and features of the present invention will be described in part in the following description and, in part, will be apparent to those skilled in the art upon examination of the following description or may be learned from practice of the present invention. The objects and other advantages of the present invention may be realized and obtained through the following description. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] In order to make the purpose, technical solutions and advantages of the present invention more clear, the present invention will be described in detail below with reference to the accompanying drawings, in which:

[0019] Figure 1 A comparison chart of Li-Li symmetric battery cycle performance tests using the electrolytes prepared in Example 1 and Comparative Example 1;

[0020] Figure 2 A comparison chart of the Li-SPAN battery cycle performance tests using the electrolytes prepared in Example 2 and Comparative Example 2;

[0021] Figure 3 Surface morphology comparison of the CEI film formed on the positive electrode surface after battery cycling using the electrolytes prepared in Example 2 and Comparative Example 2;

[0022] Figure 4 Comparison diagram of dendrite generation after battery cycling using the electrolytes prepared in Example 3 and Comparative Example 3;

[0023] Figure 5 This is a comparison diagram of the sodium metal negative electrode surface detection after cycling of the electrolyte battery prepared in Example 4 and Comparative Example 4;

[0024] Figure 6 The morphology of the potassium metal electrode after the electrolyte battery prepared in Example 5 and Comparative Example 5 is cycled;

[0025] Figure 7 A comparison of voltage-time curves of KK symmetrical batteries after cycling using the electrolytes prepared in Example 6 and Comparative Example 6; DETAILED DESCRIPTION

[0026] The following describes the embodiments of the present invention by means of specific examples, and those skilled in the art can easily understand other advantages and effects of the present invention from the contents disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and the details in this specification can also be modified or changed in various ways based on different viewpoints and applications without departing from the spirit of the present invention. It should be noted that the illustrations provided in the following embodiments are only schematic illustrations of the basic concept of the present invention, and the following embodiments and features in the embodiments can be combined with each other without conflict.

[0027] Example 1

[0028] A non-aqueous electrolyte, comprising the following components by mass fraction:

[0029] Electrolyte additive: Aniline and ZnI2 in a molar ratio of 1:2, accounting for 3% of the electrolyte by mass;

[0030] Organic solvent: a combination of ethylene carbonate and dimethyl carbonate in a volume ratio of 3:7, accounting for 82% by mass in the electrolyte;

[0031] Electrolyte lithium salt: lithium hexafluorophosphate, accounting for 10% by mass in the electrolyte;

[0032] Other additives: fluoroethylene carbonate, accounting for 5% by mass in the electrolyte.

[0033] Comparative Example 1:

[0034] An electrolyte, comprising the following components by mass fraction:

[0035] Organic solvent: a combination of ethylene carbonate and dimethyl carbonate in a volume ratio of 3:7, with its mass fraction in the electrolyte accounting for 85%;

[0036] Electrolyte lithium salt: lithium hexafluorophosphate, accounting for 10% by mass in the electrolyte;

[0037] Other additives: fluoroethylene carbonate, accounting for 5% by mass in the electrolyte.

[0038] The electrolytes prepared in Example 1 and Comparative Example 1 were respectively applied to metal-based non-aqueous secondary batteries (Li-Li symmetrical batteries), including the electrolytes prepared in Example 1 and Comparative Example 1.

[0039] The above-mentioned Li-Li symmetrical battery was subjected to electrical performance test, and the test results are as follows: Figure 1 The Li-Li symmetric battery containing the electrolyte of Example 1 was -2 and 2 mA h cm -2 Even after 1400 cycles, the curve remained stable and smooth, with a low polarization voltage. In contrast, the polarization voltage of the symmetrical cell containing the electrolyte of Comparative Example 1 gradually increased, leading to a short circuit after 500 hours. This example demonstrates that the addition of the aniline and ZnI2 combination significantly reduces the polarization voltage and improves stability.

[0040] Example 2

[0041] A non-aqueous electrolyte, comprising the following components by mass fraction:

[0042] Electrolyte additives: Silver citrate and ZnS2 are combined in a molar ratio of 1:1, and their mass fraction in the electrolyte accounts for 7%;

[0043] Organic solvent: a combination of ethylene carbonate and ethyl acetate in a volume ratio of 1:1, with its mass fraction in the electrolyte accounting for 78%;

[0044] Electrolyte lithium salt: lithium bis(fluorosulfonyl)imide LiFSI, accounting for 15% by mass in the electrolyte;

[0045] Comparative Example 2

[0046] An electrolyte, comprising the following components by mass fraction:

[0047] Organic solvent: a combination of ethylene carbonate and ethyl acetate in a volume ratio of 1:1, with its mass fraction in the electrolyte accounting for 85%;

[0048] Electrolyte lithium salt: lithium hexafluorophosphate LiPF6, its mass fraction in the electrolyte accounts for 15%;

[0049] The electrolytes prepared in Example 2 and Comparative Example 2 were respectively applied to secondary batteries, with polyacrylonitrile sulfide as the positive electrode, metallic lithium as the negative electrode, and Example 2 as the electrolyte. After 200 cycles, the capacity retention rate was 81% (as shown in FIG. Figure 2 As shown), the CEI film formed on the cathode surface after cycling is more uniform (as shown Figure 3 As shown). Comparative Example 2 is used as the electrolyte for the battery, the capacity retention rate is only 30% after 200 cycles (as shown). Figure 2 As shown), the CEI film formed on the cathode surface after cycling is not uniform (as shown Figure 3 shown).

[0050] Example 3

[0051] A non-aqueous electrolyte, comprising the following components by mass fraction:

[0052] Electrolyte additive: p-toluenethiophenol and MgF2 in a molar ratio of 1:3, accounting for 7% of the electrolyte by mass;

[0053] Organic solvent: γ-butyrolactone (GBL): ethyl methyl carbonate (EMC) in a volume ratio of 4:6, accounting for 80% of the mass fraction in the electrolyte;

[0054] Electrolyte lithium salt: sodium bis(trifluoromethanesulfonyl)imide (NaTFSI), accounting for 12% by mass in the electrolyte;

[0055] Other additives: ethyl sulfite, accounting for 1% by mass in the electrolyte.

[0056] Comparative Example 3

[0057] An electrolyte, comprising the following components by mass fraction:

[0058] Organic solvent: γ-butyrolactone (GBL): ethyl methyl carbonate (EMC) in a volume ratio of 4:6, accounting for 87% of the electrolyte by mass;

[0059] Electrolyte lithium salt: sodium bis(trifluoromethanesulfonyl)imide (NaTFSI), accounting for 12% by mass in the electrolyte;

[0060] Other additives: ethyl sulfite, accounting for 1% by mass in the electrolyte.

[0061] The electrolytes prepared in Example 3 and Comparative Example 3 were respectively applied to secondary batteries, and Na-Na symmetrical batteries were prepared with metallic sodium as the negative electrode. When the electrolyte was circulated in the battery using Example 3 as the electrolyte, no obvious dendrites were observed under an optical microscope (e.g. Figure 4 As shown), while in Comparative Example 3 as the electrolyte, very obvious dendrite generation can be seen (as shown Figure 4 shown).

[0062] Example 4

[0063] A non-aqueous electrolyte, comprising the following components by mass fraction:

[0064] Electrolyte additive: methyltaurine and MgBr2 in a molar ratio of 1:4, accounting for 4.5% of the electrolyte;

[0065] Organic solvent: γ-butyrolactone (GBL): ethyl methyl carbonate (EMC) in a volume ratio of 4:6, accounting for 85% of the mass fraction in the electrolyte;

[0066] Electrolyte lithium salt: NaPF6, its mass fraction in the electrolyte accounts for 10%;

[0067] Other additives: 1,3-propane sultone (PS), the mass fraction of which in the electrolyte is 0.5%.

[0068] Comparative Example 4

[0069] An electrolyte, comprising the following components by mass fraction:

[0070] Organic solvent: γ-butyrolactone (GBL): ethyl methyl carbonate (EMC) in a volume ratio of 4:6, accounting for 89.5% of the mass fraction in the electrolyte;

[0071] Electrolyte lithium salt: NaPF6, its mass fraction in the electrolyte accounts for 10%;

[0072] Other additives: 1,3-propane sultone (PS), the mass fraction of which in the electrolyte is 0.5%.

[0073] like Figure 5 As shown in the figure, the surface of the sodium metal negative electrode circulating in the electrolyte with the addition of the combined additives is covered with a uniform and dense film, and the surface is relatively smooth and flat, while the surface of the sodium metal negative electrode circulating in the electrolyte without the addition of the combined additives presents an uneven morphology and has more holes.

[0074] Example 5

[0075] A non-aqueous electrolyte, comprising the following components by mass fraction:

[0076] Electrolyte additive: Phenylalanine and BiF3 are combined in a molar ratio of 1:0.5, and their mass fraction in the electrolyte accounts for 4%;

[0077] Organic solvent: γ-butyrolactone (GBL): ethyl methyl carbonate (EMC) in a volume ratio of 4:6, accounting for 83% of the electrolyte by mass;

[0078] Electrolyte lithium salt: KFSI, accounting for 12% by mass in the electrolyte;

[0079] Other additives: 1,3-propane sultone (PS), the mass fraction of which in the electrolyte accounts for 1%.

[0080] Comparative Example 5

[0081] An electrolyte, comprising the following components by mass fraction:

[0082] Organic solvent: γ-butyrolactone (GBL): ethyl methyl carbonate (EMC) in a volume ratio of 4:6, accounting for 87% of the electrolyte by mass;

[0083] Electrolyte lithium salt: KFSI, accounting for 12% by mass in the electrolyte;

[0084] Other additives: 1,3-propane sultone (PS), the mass fraction of which in the electrolyte accounts for 1%.

[0085] The electrolytes prepared in Example 5 and Comparative Example 5 were respectively applied to metal-based non-aqueous secondary batteries, including a metal potassium negative electrode, a sulfur / carbon composite positive electrode, a separator, and the electrolytes prepared in Example 5 and Comparative Example 5. Figure 6 As shown, the metal potassium electrode after cycling was disassembled for morphological observation, and it was found that the surface of the metal potassium negative electrode after cycling in the electrolyte containing the combined additives was uniform and flat, while the surface of the electrolyte without the "combination" additives had obvious strip dendrites and more porous structures after cycling.

[0086] Example 6

[0087] A non-aqueous electrolyte, comprising the following components by mass fraction:

[0088] Electrolyte additive: a combination of copper glutamate and InI3 at a molar ratio of 1:0.5, with their mass fraction in the electrolyte accounting for 10%;

[0089] Organic solvent: γ-butyrolactone (GBL): ethyl methyl carbonate (EMC) in a volume ratio of 4:6, accounting for 80% of the mass fraction in the electrolyte;

[0090] Electrolyte lithium salt: KPF6, its mass fraction in the electrolyte accounts for 10%;

[0091] Other additives: None.

[0092] Comparative Example 6

[0093] An electrolyte, comprising the following components by mass fraction:

[0094] Organic solvent: γ-butyrolactone (GBL): ethyl methyl carbonate (EMC) in a volume ratio of 4:6, accounting for 90% of the mass fraction in the electrolyte;

[0095] Electrolyte lithium salt: KPF6, its mass fraction in the electrolyte accounts for 10%;

[0096] Other additives: None.

[0097] The electrolytes prepared in Example 6 and Comparative Example 6 were respectively applied to metal-based non-aqueous secondary batteries (KK symmetrical batteries). The electrical performance of the KK symmetrical batteries was tested. Figure 7 As shown in the figure, the voltage-time curve of the symmetrical battery is very flat, there is no short circuit phenomenon, and the polarization voltage is small. The voltage-time curve of the symmetrical battery without additives is violently jittery, and the polarization is particularly large.

[0098] It can be seen from the above embodiments that the electrolyte disclosed in the present invention can synergistically optimize the positive and negative electrode interface stability and the electrolyte solvation structure by combining small molecule hydrogen bond donors with metal halide / oxygen compounds. The self-repairing ability of the positive electrode interface can be enhanced by the electrochemical oxidation of hydrogen bond donor small molecules, while the reduction passivation effect of metal halide salts is used to effectively inhibit the negative electrode interface side reactions, thereby significantly improving the high stability of metal batteries. In addition, hydrogen bond donor small molecules can form stable hydrogen bond complexes with polysulfides, further optimize the solvation structure of the electrolyte, promote interfacial ion transport, and thus significantly improve the cycle life and rate performance of sulfur-based batteries. In addition, hydrogen bond donor small molecules can also coordinate with metal cations in metal salt halides / oxygen compounds (such as ZnCl2, ZnI2, MgS2, etc.) in the solution to form new complexes to participate in the formation, evolution and dynamic repair of the positive and negative electrode interface layer.

[0099] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not limiting. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solutions of the present invention can be modified or replaced by equivalents without departing from the purpose and scope of the technical solutions, which should all be included in the scope of the claims of the present invention.

Claims

1. A combined electrolyte additive, characterized in that: The additive consists of a small molecule hydrogen bond donor with a high HOMO energy level and a metal compound with a low LUMO energy level. The metal compound is at least one of a metal halide or a metal oxide.

2. The combined electrolyte additive according to claim 1, characterized in that: The hydrogen bond donor small molecule is composed of one or more of amino compounds, hydroxyl-containing compounds, sulfhydryl-containing compounds, carboxylic acid compounds, amide compounds, phosphonic acid, and guanidine-containing compounds, or salts of the compounds.

3. The combined electrolyte additive according to claim 2, characterized in that: The amino compound is one or more of ammonia, aniline, urea, and amino acids; the hydroxyl-containing compound is one or more of ethylene glycol, glycerol, phenol, lactic acid, and glucose; the sulfhydryl-containing compound is one or more of thiol and thiophenol; the carboxylic acid compound is one or more of acetic acid and benzoic acid; the amide compound is one or more of acetamide and glycine dipeptide; and the guanidine-containing compound is one or more of guanidine hydrochloride, guanidine sulfamate, dodecylguanidine acetate, and guanidine phosphate.

4. The combined electrolyte additive according to claim 2, characterized in that: The salt is one or more of ethylamine hydrochloride, aniline sulfate, triethylamine citrate, sodium glutamate, and copper glutamate.

5. The combined electrolyte additive according to claim 1, characterized in that: The metal halide is one or more of ZnCl2, ZnI2, MgBr2, AlCl3, SnCl2, FeCl3, and CuBr2, and the metal oxide is one or more of MgO, ZnO, ZnS2, MgS2, Al2S3, SnS2, Fe2Se3, and CuSe2.

6. The combined electrolyte additive according to claim 1, characterized in that: The molar ratio of the hydrogen bond donor small molecule to the metal compound is 1:0.1-1:

5.

7. A non-aqueous electrolyte, characterized in that Calculated by mass fraction, the electrolyte includes 0.01%-15% of electrolyte additives, 60%-90% of organic solvents, 5%-30% of electrolyte lithium salts, and 0.01%-10% of other additives.

8. The non-aqueous electrolyte according to claim 7, characterized in that: The organic solvent is at least one of ethylene carbonate, propylene carbonate, dimethyl carbonate, ethyl methyl carbonate, γ-butyrolactone, and ethyl acetate; the electrolyte lithium salt is at least one of lithium perchlorate, sodium hexafluorophosphate, sodium bisfluorosulfonyl imide, sodium bis(trifluoromethanesulfonyl)imide, sodium perchlorate, potassium hexafluorophosphate, potassium bisfluorosulfonyl imide, potassium bis(trifluoromethanesulfonyl)imide, and potassium perchlorate; and the other additives are at least one of vinylene carbonate, fluoroethylene carbonate, lithium difluorophosphate, 1,3-propane sultone, and vinyl sulfate.

9. Application of a non-aqueous electrolyte in a metal-based non-aqueous secondary battery.

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