Triazine derivative and application thereof as dewatering additive in secondary battery

Abstract

The invention provides a triazine derivative and application of the triazine derivative as a water removal additive in a secondary battery, and belongs to the field of secondary battery electrolyte additives. The triazine derivative has a structure as shown in a formula I; wherein R1, R2, R3, R4, R5 and R6 are respectively and independently selected from bis (perfluoroalkyl) sulfonyl imide groups. The highly delocalized triazine ring skeleton has reaction activity highly sensitive to water, and water molecules in an electrolyte system can be effectively reduced or removed, so that the influence of water on the whole battery system is avoided. The characteristic metal ion source part, such as a lithium ion source, can effectively improve the solubility of the whole derivative in an electrolyte system, and plays a role in trace and high efficiency of an electrolyte additive; and after 1mol of the electrolyte additive is decomposed in water, 12mol of LiTFSI salt and the like can be generated, so that the overall salt concentration of the whole electrolyte is improved. # imgabs0 #

Description

Technical Field

[0001] The present invention relates to the field of electrolyte additives for secondary batteries, in particular to a triazine derivative and its application as a dehydrating additive in secondary batteries, specifically to a dehydrating electrolyte additive and its application in secondary batteries. Background Art

[0002] In today's world, energy storage batteries have become an indispensable part of life. The government has introduced a series of policies to guide and support the development of the lithium battery industry. For example, the Ministry of Industry and Information Technology issued the "Lithium Battery Industry Standard Conditions (2024 Edition) (Draft for Comments)", which provides guidance and specific suggestions on industrial layout, production and operation, product performance, safety and quality management. The introduction and implementation of these policies will help regulate the market order of the lithium battery industry and promote technological innovation and industrial upgrading of enterprises.

[0003] With the rapid development of the new energy vehicle market, power lithium batteries have become the main application field of the lithium battery industry chain. The continued growth in new energy vehicle sales will directly drive the expansion of the lithium battery market. It is predicted that China's power battery shipments will exceed 820GWh in 2024, an increase of more than 20% year-on-year. Energy storage systems are another important area of ​​lithium battery application; with the advancement of battery technology and the reduction of costs, the application of lithium batteries in energy storage systems is also gradually expanding. It is expected that by 2024, China's energy storage battery shipments will exceed 200GWh, an increase of more than 25% year-on-year. In terms of the industrial chain, the lithium battery industry chain covers multiple links from raw material mining, production and processing to application recycling, which requires close cooperation and coordinated development of all links. With the continuous improvement and maturity of the industrial chain, the overall competitiveness of the lithium battery industry will be further enhanced. And with the intensification of domestic market competition, more and more lithium battery industry chain companies are beginning to go overseas. Southeast Asia, Eastern Europe and South America will become the main areas for the overseas layout of domestic lithium battery industry chain companies.

[0004] In summary, the development trend of lithium-ion batteries shows the characteristics of continuous growth in market demand, development driven by technological innovation, coordinated development of the industrial chain, and support from the policy environment. In the future, with the rapid development of the new energy vehicle market and the widespread application of energy storage systems, as well as the continuous research and development and application of new battery technologies, the lithium-ion battery industry will usher in a broader development prospect.

[0005] When batteries are transformed from laboratories to factories on a large scale, the amplification effect is particularly prominent in the preparation of battery cells and the production and configuration of electrolytes, especially the strict control of water content, which reflects the R&D strength and quality control strength of an enterprise. However, in the traditional preparation of battery cells, there are problems caused by water molecules, such as excessive water content in the positive and negative electrodes, which is difficult to remove, and excessive water content in the electrolyte, which is not conducive to electrical performance. Summary of the invention

[0006] In view of this, the purpose of the present invention is to provide a triazine derivative and its use as a water-removing additive in a secondary battery. The triazine derivative provided by the present invention is sensitive to water and can be added to an electrolyte to effectively react and remove water molecules in the electrolyte, thereby inhibiting the increase in acidity caused by the decomposition of lithium hexafluorophosphate in the electrolyte when it encounters water and the subsequent generation of side reactions in the battery.

[0007] The present invention provides a triazine derivative having a structure of Formula I:

[0008]

[0009] Wherein, R1, R2, R3, R4, R5 and R6 are independently selected from bisperfluoroalkylsulfonyl imide groups.

[0010] In some embodiments, R1, R2, R3, R4, R5 and R6 are all the same bis-perfluoroalkylsulfonyl imide group.

[0011] In some embodiments, the triazine derivative has a structure of Formula I-1:

[0012]

[0013] The present invention provides a method for synthesizing the triazine derivatives as described above, comprising the following steps:

[0014] The polyhalogenated triazine ring skeleton compound shown in formula II is reacted with a perfluorinated compound to obtain a triazine derivative shown in formula I;

[0015]

[0016] Wherein, X is a halogen element; and the perfluorinated compound is bisperfluoroalkylsulfonyl imide benzene.

[0017] In some embodiments, the perfluorinated compound is bis-perfluoromethylsulfonyl imide benzene;

[0018] The preparation of the polyhalogenated triazine ring skeleton compound shown in formula II comprises: subjecting a s-triazine Grignard reagent to an alkylation-like reaction with a monohalogenated s-triazine, and then subjecting the obtained reactant to a perhalogenation reaction with a halogenating reagent to obtain the polyhalogenated triazine ring skeleton compound.

[0019] In some embodiments, in the perhalogenation reaction of the reactant and the halogenation reagent, the molar ratio of the reactant to the halogenation reagent is controlled to be 1:(6-20);

[0020] The molar ratio of the polyhalogenated triazine ring skeleton compound represented by formula II to the perfluorinated compound is 1:(6-20), and the tert-butanol solution of lithium tert-butoxide is used as the reaction solvent.

[0021] The present invention provides the use of the above-mentioned triazine derivatives as water removal additives in secondary batteries, wherein the secondary batteries include but are not limited to lithium-sulfur batteries, lithium batteries, sodium-sulfur batteries or sodium batteries.

[0022] In some embodiments, the secondary battery may be in the form of, but not limited to, a button battery, a soft-pack battery, a square battery, a steel-shell battery, an aluminum-shell battery, and a 18650 battery.

[0023] The present invention provides an electrolyte, which uses the above-mentioned triazine derivatives as additives.

[0024] In some embodiments, the electrolyte includes a carbonate mixture, an ether mixture, a sulfone mixture or a nitrile mixture; and the amount of the triazine derivative added to the electrolyte is 0.01 wt %-5 wt %.

[0025] Compared with the prior art, the present invention provides a triazine derivative having a structure of Formula I, which is structurally divided into two parts: a highly electron-delocalized triazine ring skeleton and a characteristic metal ion source, namely a bis-perfluoroalkylsulfonyl imide group. In the present invention, the highly delocalized triazine ring skeleton has a reaction activity that is highly sensitive to water, and can effectively reduce or remove water molecules in the electrolyte system, thereby avoiding the influence of water on the entire battery system (such as hydrogen evolution reaction, oxygen evolution reaction, salt decomposition, etc.). The characteristic metal ion source part of the present invention, such as a lithium ion source, can effectively improve the solubility of the derivative as a whole in the electrolyte system, and play the role of a trace and efficient electrolyte additive; and after 1 mol of the electrolyte additive is decomposed by water (or positive and negative electrode redox), it can produce 12 mol of LiTFSI salt, etc., so that the overall salt concentration of the entire electrolyte is improved.

[0026] The presence of the preferred bis-perfluoromethylsulfonyl imide (TFSI) anion of the present invention greatly improves the sensitivity of the triazine ring structure to water (about ≥50ppm), and can effectively capture and react water molecules in the electrolyte system, so that the moisture content is reduced to below 50ppm, meeting the national application standards. The redox and hydrolysis products of the additive are oxalate and TFSI salt, which can effectively participate in the formation of SEI / CEI membranes and form a synergistic effect of multiple salts, effectively improving the electrochemical performance of the battery. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 is the carbon nuclear magnetic resonance spectrum of the triazine derivatives represented by formula I-1 in the embodiments of the present invention;

[0028] Figure 2 The graph of the charge and discharge capacity-voltage platform curve obtained in Example 1 in the long cycle test at a rate of 1C in the LFP / graphite soft pack battery;

[0029] Figure 3 This is a graph showing the relationship between the capacity and voltage platform curves obtained in Example 2 in a long cycle test at a rate of 1C in an LFP / graphite soft pack battery;

[0030] Figure 4 This is a graph showing the relationship between the capacity and voltage platform curves obtained in Comparative Example 2 in a long cycle test at a rate of 1C in an LFP / graphite soft-pack battery. DETAILED DESCRIPTION

[0031] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in combination with the drawings and the like in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0032] The present invention provides a triazine derivative having a structure of Formula I:

[0033]

[0034] Wherein, R1, R2, R3, R4, R5 and R6 are independently selected from bisperfluoroalkylsulfonyl imide groups.

[0035] The triazine derivatives provided by the present invention are sensitive to water and can be added to an electrolyte to effectively react and remove water molecules in the electrolyte, thereby inhibiting the increase in acidity caused by the decomposition of lithium hexafluorophosphate in the electrolyte when it encounters water and the subsequent generation of side reactions in the battery.

[0036] The general structural formula of the triazine derivatives described in the embodiment of the present invention is shown in Formula I, which is composed of a highly electron-delocalized triazine ring skeleton and a characteristic metal ion source. In Formula I, the triazine derivatives are mainly composed of tri-triazine-substituted s-triazine, the central body is a highly negatively charged s-triazine ring, and the carbon skeleton connects three triazine rings to greatly enhance the degree of electron delocalization of the entire structure. The highly delocalized triazine ring skeleton has a highly sensitive reaction activity to water, and the sensitivity to water is ≥50ppm, which can effectively reduce or remove water molecules in the electrolyte system, thereby avoiding the influence of water on the entire battery system (such as hydrogen evolution reaction, oxygen evolution reaction, salt decomposition, etc.).

[0037] In addition to the main body, the carbon skeleton of the three triazine rings is also linked to the groups R1, R2, R3, R4, R5 and R6, wherein R1, R2, R3, R4, R5 and R6 are independently selected from bis-perfluoroalkylsulfonyl imide groups and can be the same or different; these groups are electron-withdrawing groups and have a high dielectric constant. As a metal ion source, they can promote the dissociation of metal ions and increase the salt concentration, and have a certain solvation effect. Among them, the perfluoroalkyl group in the bis-perfluoroalkylsulfonyl imide group is preferably a trifluoromethyl group.

[0038] In some embodiments, the R1, R2, R3, R4, R5 and R6 are all the same bis-perfluoroalkylsulfonyl imide group, and further all are bis-trifluoromethylsulfonyl imide groups (which can be expressed as -N(SO2CF3)2, referred to as TFSI group, etc.). The TFSI- anion group is a strong electron-withdrawing group and has the characteristics of a high dielectric constant. It can effectively promote the dissociation of lithium ions and increase the salt concentration, as well as the solvation effect in the electrolyte system, and to a certain extent improve the overall lithium conductivity of the electrolyte system. The group can be a lithium ion source part, which can effectively improve the solubility of the derivative as a whole in the electrolyte system, and play the role of a trace and efficient electrolyte additive. After 1 mol of the additive is decomposed in water (or positive and negative electrode redox), 6 mol of LiTFSI salt can be produced, so that the entire electrolyte produces a beneficial double salt (multiple salt) synergistic effect.

[0039] Preferably, the triazine derivative has a structure of formula I-1, including a TFSI group, and its full chemical name is hexa-1,3-bis(trifluoromethylsulfonyl)imide fully substituted 1,3,5-tri(2,4,6-isotriazine)substituted triazine, which can be referred to as triazine derivative of formula I-1. Its decomposition products when exposed to water are ammonium formate and bis(trifluoromethylsulfonyl)imide salt. In an electrolyte environment, since the amount of water is trace, the trace amount of ammonium formate generated will be converted into lithium formate and participate in the formation of an interfacial film. The released bis(trifluoromethylsulfonyl)imide salt will increase the salt concentration in the electrolyte. As a special type of anion, the trifluoromethylsulfonyl imide group can effectively improve the high-voltage oxidation stability of the positive electrode material, thereby obtaining a higher upper limit of energy density.

[0040]

[0041] The present invention provides a method for synthesizing the triazine derivatives as described above, comprising the following steps:

[0042] The polyhalogenated triazine ring skeleton compound shown in formula II is reacted with a perfluorinated compound to obtain a triazine derivative shown in formula I;

[0043]

[0044] Wherein, X is a halogen element (chlorine, bromine, iodine, etc., preferably chlorine (Cl)); and the perfluorinated compound is bisperfluoroalkylsulfonyl imide benzene.

[0045] Taking the perfluorinated compound as bisperfluoromethylsulfonyl imide benzene, the triazine derivative of the synthetic formula I-1 is taken as an example, and the reaction formula involved in the synthetic route includes:

[0046]

[0047]

[0048] In the above-mentioned embodiment, the reaction (1) is a simple cyclization reaction of hydrocyanic acid (HCN) and hydrogen chloride (HCl). 2,4,6-s-triazine with a purity of 99.9% can also be purchased directly from Aladdin Shanghai Technology Co., Ltd. or the like.

[0049] The reaction (2) is a full halogenation reaction of s-triazine, and the molar ratio of s-triazine to the halogenating agent can be controlled to be 1:(3-10). The halogenating agent selected includes but is not limited to halogenated succinimide (such as chlorosuccinimide), chloroform, methyl iodide, methyl bromide, etc., preferably chlorosuccinimide.

[0050] The reaction (3) is the preparation of Grignard reagent (abbreviated as Grignard reagent, which is an organic metal compound containing magnesium halide). Grignard reagent is generally prepared by reacting halogenated hydrocarbons with magnesium powder (Mg) in anhydrous ether or tetrahydrofuran (THF) and other solvents. In the embodiment of the present invention, the above-mentioned trichloro-s-triazine is reacted with magnesium powder. The selected solvent can be 99.99% pure tetrahydrofuran. The reaction temperature is preferably -40°C to -10°C, and the triazine Grignard reagent is obtained.

[0051] In addition, the reaction (4) is a monohalogenation reaction of s-triazine, and s-triazine can be subjected to a monosubstitution reaction with a halogenating agent, and the molar ratio of s-triazine to the halogenating agent is controlled to be 1:1 to obtain a monohalogenated s-triazine; the halogenating agent (or halogenating agent) includes but is not limited to halogenated succinimide (such as chlorosuccinimide), chloroform, methyl iodide, methyl bromide, etc., preferably chlorosuccinimide.

[0052] The reaction (5) described in the specific embodiment of the present invention is a quasi-alkylation reaction of a Grignard reagent, and the molar ratio of the obtained triazine Grignard reagent to the monohalogenated s-triazine can be controlled to be 1:3. The alkylation reaction of the Grignard reagent is a reaction used to extend the carbon chain. The embodiment of the present invention introduces three s-triazine rings through the quasi-alkylation reaction.

[0053] The reaction (6) is a perhalogenation reaction of the alkylation reaction product, and the molar ratio of the reactant to the halogenation agent can be controlled to be 1: (6-20) to obtain a polyhalogenated triazine ring skeleton compound shown in formula II; the halogenation agent includes but is not limited to halogenated succinimide (such as chlorosuccinimide), chloroform, iodomethane, bromomethane, etc., preferably chlorosuccinimide. For other reactions where the reaction conditions are not marked, it is assumed that the reactants are added at room temperature and standard pressure, and the relevant products can be obtained after a period of time, without special reaction conditions (i.e., the selection of reactants is an important condition, such as the selection of halogenation agents).

[0054] Finally, the reaction (7) can be a halogen exchange reaction of the polyhalogenated triazine ring skeleton compound shown in formula II. It is preferred to control the molar ratio of the polyhalogenated triazine ring skeleton compound to bis(trifluoromethylsulfonyl)imide benzene to be 1:(6-20), and further to be 1:7-15, to obtain the triazine compound of formula I-1. The halogen exchange reaction is a quasi-inorganic metathesis reaction of the halogen atom and the large anion group. The reaction kinetics is the stronger binding energy of the linking group of the halogen atom and the anion group, forcing it to undergo a quasi-metathesis exchange. Among them, the bis(trifluoromethylsulfonyl)imide benzene can be a commercially available raw material of Aladdin, and the reaction solvent is preferably a tert-butanol solution of lithium / sodium tert-butoxide (such as expressed as CH3OH / CH3ONa).

[0055] The electrolyte additive of the new structure prepared in the embodiment of the present application has a simple structure, a yield of more than 80% (all reactions are classic organic reactions with high yield characteristics), and low raw material costs. The presence of a fully conjugated structure and 12 equivalent substitution salts greatly reduces the cost of separation and purification. The cost of the reaction raw materials is calculated based on the reactant consumption / yield, and the cost of the additive of the structure described in the present invention is relatively low.

[0056] The present invention provides the use of the above-mentioned triazine derivatives as water-removing additives in secondary batteries; the types of secondary batteries to which the water-removing additives are applied include but are not limited to: lithium-sulfur batteries, lithium batteries (including lithium-ion batteries, lithium metal batteries), sodium-sulfur batteries or sodium batteries (including sodium-ion batteries, sodium metal batteries), etc.

[0057] In some embodiments, the secondary battery to which the water removal additive is applied includes but is not limited to: one or more of button batteries, soft-pack batteries, square batteries, steel-shell batteries, aluminum-shell batteries and 18650 batteries.

[0058] Specifically, an embodiment of the present invention provides an electrolyte, which uses the triazine derivatives mentioned above as additives; the electrolyte can be called an electrolyte system that is easily hygroscopic.

[0059] In some embodiments, the electrolyte system includes carbonate mixtures, ether mixtures, sulfone mixtures or nitrile mixtures. The carbonate mixture generally includes carbonate (EC), polycarbonate (PC), dimethyl carbonate (DMC), etc. In a preferred embodiment, the volume ratio of EC, PC and DMC is 1:1:1, which is conducive to obtaining better electrochemical performance. Ethers are mainly polyethylene glycol dimethyl ether, and the number of ethylene glycol structures can be 1-4 (such as tetraethylene glycol dimethyl ether); sulfones include disulfones or cyclic sulfones, the number of carbon atoms in the carbon chain of disulfones is within 4, and the number of carbon atoms in the cyclic sulfone is more than 4 (such as dimethyl sulfone, cyclopentane sulfone); nitriles are generally dinitriles, and the number of carbon atoms in the carbon chain of dinitriles is more than 4 (such as succinonitrile).

[0060] In some embodiments, the amount of the triazine derivative additive added to the electrolyte system is preferably 0.01wt%-5wt%, more preferably 0.01-3wt%, further 0.01-2wt%, such as 0.01%, 0.05%, 0.1%, 0.5%, 0.6%, 1%, 1.2%, etc. In addition, the embodiments of the present invention have no special restrictions on the metal salt in the electrolyte system, and conventional lithium salts (such as lithium hexafluorophosphate LiPF6) and sodium salts can be used.

[0061] Compared with conventional electrolytes, the addition of the additive in the embodiment of the present invention can effectively inhibit the hydrogen evolution and oxygen evolution reactions at the positive and negative electrodes, reduce the corrosion and damage of water to the positive and negative electrode structures, improve the oxidation potential of the positive electrode, and help improve the overall energy density of the battery cell.

[0062] In order to better illustrate the present invention, the following examples are further illustrated. Unless otherwise specified, the various reagents and raw materials used in the present invention are all commodities that can be purchased from the market or products that can be prepared by recognized methods. Among them, the s-triazine involved is 2,4,6-s-triazine with a purity of 99.9% directly purchased from Aladdin Shanghai Technology Co., Ltd.; bistrifluoromethylsulfonyl imide benzene is a commercially available raw material from Aladdin. Unless otherwise specified, the proportions involved are all mass proportions.

[0063] The additives described in the examples are all fully substituted triazine derivatives of lithium bis(trifluoromethylsulfonyl)imide, and the preparation method thereof is the synthesis of a triazine derivative shown in formula I-1, which is specifically as follows:

[0064] The s-triazine is subjected to a full halogenation reaction with chlorosuccinimide, the molar ratio of the reactant to the chlorosuccinimide is controlled to be 1:5, and the trichloro-s-triazine is obtained by separation extraction;

[0065] The Grignard reagent is prepared by reacting trichloro-s-triazine with magnesium, the selected solvent is 99.99% pure tetrahydrofuran, and the reaction temperature is -20°C.

[0066] In addition, s-triazine was subjected to a monohalogenation reaction using chlorosuccinimide, and the molar ratio of the reactant to the halogenation reagent was controlled to be 1:1. The monochloro-s-triazine was obtained by rotary evaporation at different boiling points and condensation.

[0067] The prepared triazine Grignard reagent is subjected to a quasi-alkylation reaction with monochloro-s-triazine, and the molar ratio of the triazine Grignard reagent to the monochloro-s-triazine is controlled to be 1:3; then, the obtained reactant is subjected to a perhalogenation reaction with chlorosuccinimide, and the molar ratio of the reactant to the halogenation reagent is controlled to be 1:7, so as to obtain a polychlorinated triazine ring skeleton compound.

[0068] The polychlorinated triazine ring skeleton compound is reacted with bis(trifluoromethylsulfonyl)imide benzene, and the molar ratio of the polychlorinated triazine ring skeleton compound to bis(trifluoromethylsulfonyl)imide benzene is controlled to be 1:9; the reaction solvent is a tert-butanol solution of lithium tert-butoxide, and the target product is obtained by separation extraction and reduced pressure distillation.

[0069] Product testing method 1 (GB / T 6682):

[0070] (1) Using acetone-dichloromethane mixed solvent as the extractant, extract by Soxhlet extraction or pressurized fluid extraction: carefully transfer the synthetic sample into the Soxhlet extraction sleeve, place the sleeve in the reflux tube of the Soxhlet extractor, add 200 ml of acetone-dichloromethane mixed solvent into the bottom bottle, reflux and extract for 24 hours, control the reflux rate at 3-4 times / h, and collect the extract.

[0071] (2) Extraction liquid concentration: Sample loading was performed according to the national standard HJ783, and the extract was collected after static extraction for 3 times. Extraction reference conditions: carrier gas pressure 0.8 MPa, heating temperature 100 °C, extraction pressure 1.034 x 10 7 Pa (1500 psi), preheating equilibrium for 5 min, static extraction for 5 min, solvent elution 60% cell volume, nitrogen purge for 60 s.

[0072] (3) The extract was concentrated to about 0.5 ml, and about 5 ml of n-hexane was added and concentrated to 1 ml, thereby completely converting the solvent to n-hexane.

[0073] (4) Purification: Fix the solid phase extraction column on the solid phase extraction device, activate the extraction column with 5 ml acetone and 10 ml n-hexane in turn, and keep the column head wet. Before the solvent runs dry, transfer about 1 ml of the concentrated extract into the column, start collecting the effluent, wash the concentration container with 3 ml n-hexane three times, transfer all the washing liquid into the column, elute with 10 ml acetone-n-hexane mixed solvent, and collect all the eluate.

[0074] (5) Volume adjustment: Concentrate the purified eluate to about 0.5 ml, add about 3 ml of acetonitrile, and concentrate again to about 0.5 ml, completely convert the solvent to acetonitrile, and adjust the volume to 1.0 ml with acetonitrile for testing.

[0075] (6) The components were determined by high performance liquid chromatography: the injection flow rate was set at 1.0 ml / min; the column temperature was set at 30°C; the injection volume was 10 μl; the detection wavelength was 222 nm; and the auxiliary qualitative wavelength was 231 nm.

[0076] (7) If a peak appears at a wavelength of 222 nm, it proves that the main skeleton structure of the substance has been successfully synthesized.

[0077] (8) Auxiliary proof: 1 mmol of the intermediate product obtained in the synthesis step reaction (6) was dissolved in 1 L of water, and the content of ammonium formate, a decomposition product of the additive, was quantitatively detected by UV-visible spectrophotometry or acid-base titration, thereby inferring the structure and content of the intermediate product and confirming that the main skeleton structure of the product has been successfully synthesized.

[0078] (9) The concentration and amount of bis(trifluoromethylsulfonyl)imidebenzene in the final solution obtained in the synthesis step (7) are detected by UV-visible spectrophotometry, and the difference between the concentration and the amount of the substance initially added is converted to verify whether the final product is successfully synthesized. The specific structure of the substance can be obtained by UV spectrophotometry, which belongs to specific detection.

[0079] Product detection method 2:

[0080] The final structure of the product was detected by nuclear magnetic resonance, with deuterated heavy water as the indicator standard, and the obtained carbon spectrum (C'NMR) was as follows Figure 1 As shown; this substance has no protons, so there is no H'NMR.

[0081] In C'NMR, three carbon atoms with a chemical shift of 175.5 ppm are three equivalent carbon atoms of the central triazine; three carbon atoms with a chemical shift of 178.7 ppm are three equivalent carbon atoms at the connection between the three triazines and the central triazine; six carbon atoms with a chemical shift of 177.6 ppm are two equivalent carbon atoms of each of the three substituent triazines; and 12 carbon atoms with a chemical shift of 157.9 ppm are 12 equivalent trifluoromethyl carbon atoms on the bistrifluoromethylsulfonyl imide group.

[0082] Example 1

[0083] Optimization of electrolyte for a hygroscopic lithium iron phosphate (LFP) cathode electrode material:

[0084] The electrolyte selected is a common commercial electrolyte (1M LiPF6-EC / PC / DMC=1:1:1). In this embodiment, a synthesized triazine derivative is used as an additive, and the addition ratio is 1.0wt%. The soft-pack battery selected for injection is LFP positive electrode / graphite negative electrode, and the injection amount is 4.5Ah / g.

[0085] The electrolyte with additives added is used to fill the soft pack battery, and the standard test procedure of formation-capacity separation-long cycle (GB31241-2022) is carried out. The voltage curve of the first cycle of the long cycle is as follows Figure 2 The gas production conditions are shown in Table 1.

[0086] like Figure 2 As shown, the voltage curves of the first cycle and the 41st cycle are slightly different, and the capacity retention rate is 94.2%. It can be seen that due to the presence of the additive, the content of water molecules in the electrolyte system is effectively controlled, the side reactions in the system are less, and the capacity decay is relatively slow.

[0087] Example 2

[0088] Electrolyte optimization for a hygroscopic LFP cathode electrode material:

[0089] The electrolyte selected is a common commercial electrolyte (1M LiPF6-EC / PC / DMC=1:1:1). In this embodiment, a synthesized triazine derivative is used as an additive, and the addition ratio is 0.01wt%. The soft-pack battery selected for injection is LFP positive electrode / graphite negative electrode, and the injection amount is 4.5Ah / g.

[0090] The electrolyte with additives added is used to fill the soft pack battery, and the standard test procedure of formation-capacity separation-long cycle is carried out. The voltage curve of the first cycle of the long cycle is as follows: Figure 3 The gas production conditions are shown in Table 1.

[0091] like Figure 3As shown, there is little difference in the voltage curves between the 1st cycle and the 41st cycle, and the capacity retention rate is 93.4%. Adding 0.01% of the additive can produce a more obvious effect, which is in line with the principle of trace additives and high efficiency.

[0092] Example 3

[0093] Optimization of electrolyte for a hygroscopic positive electrode NCM811 electrode material:

[0094] The electrolyte selected is ordinary commercial electrolyte (1M LiPF6-EC / PC / DMC=1:1:1), and the synthesized triazine derivative of formula I-1 is used as an additive with an addition ratio of 0.1wt%; the soft-pack battery selected for injection is NCM811 positive electrode / graphite negative electrode, and the injection amount is 5.6Ah / g.

[0095] The electrolyte with the additive added was used to inject the soft-pack battery, and the standard test procedure of formation-capacity separation-long cycle was carried out. The gas production of the soft-pack battery is shown in Table 1.

[0096] Comparative Example 1

[0097] A common electrolyte combination for positive LFP electrode material:

[0098] The electrolyte selected is ordinary commercial electrolyte (1M LiPF6-EC / PC / DMC=1:1:1), the soft-pack battery selected for injection is LFP / graphite negative electrode, and the injection amount is 4.5Ah / g.

[0099] The commercial electrolyte was used to fill the soft-pack battery, and the standard test procedure of formation-capacity separation-long cycle was carried out. The gas production of the soft-pack battery is shown in Table 1.

[0100] Comparative Example 2

[0101] A common electrolyte combination for positive NCM811 electrode material:

[0102] The electrolyte selected is ordinary commercial electrolyte (1M LiPF6-EC / PC / DMC=1:1:1), the soft-pack battery selected for injection is NCM811 positive electrode / graphite negative electrode, and the injection amount is 5.6Ah / g.

[0103] The commercial electrolyte was used to fill the soft pack battery and then the standard test procedure of formation-capacity division-long cycle was carried out. The voltage curve of the first cycle of the long cycle is as follows: Figure 4 The gas production conditions are shown in Table 1.

[0104] like Figure 4As shown in the figure, a large difference can be seen between the voltage curves of the first cycle and the eleventh cycle, and the fluctuation point of abnormal increase in capacity due to the side reaction during battery discharge clearly shows the side effects of the presence of water. The moisture content of the comparative battery electrolyte exceeded the standard, that is, without adding the additive, the battery dropped after a dozen cycles.

[0105] Table 1. Soft pack battery formation and 100 cycle volume test

[0106]

[0107] Note: The volume unit of soft pack battery before and after formation is milliliter.

[0108] It can be seen from Table 1 that in the LFP / graphite and NCM811 / graphite systems, the addition of the additive has a significant inhibitory effect on the gas production compared to no addition.

[0109] Depend on Figure 2-Figure 3 It can be seen that the triazine derivative electrolyte additive developed in the embodiment of the present application has good compatibility with LFP / graphite soft-pack batteries (nominal 0.6Ah), and as the amount of addition increases, the battery's cycle capacity retention performance will be positively correlated. This shows that the triazine derivative additive can effectively reduce the water content in the electrolyte system, and its hydrolysis product has no toxic effect on the entire battery system and will not cause deactivation and poisoning of the positive and negative electrode materials. Figure 2-4 It can be seen that the capacity decay of the additive-free electrolyte system in the comparative example is more serious than that of the additive-containing electrolyte system in the embodiment, and there is an inflection point of abnormal capacity increase caused by obvious side reactions (hydrogen evolution and oxygen evolution reaction of water, hydrolysis of salt, and influence of acidity) during discharge.

[0110] In addition, the present application conducted comparative experiments with other added substances, and the results are shown in Table 2.

[0111] Table 2. Water removal additive effect test

[0112]

[0113] Note: The additive amount is 0.5%.

[0114] The general types of water removal additives on the market are shown in Table 2, which are compared and evaluated from the aspects of cost, toxicity, compatibility with battery systems, sensitivity to water reaction, and hydrolysis products:

[0115] As can be seen from Table 2, zeolite molecular sieves rely on physical adsorption to remove water, and may dissolve impurity ions such as potassium, sodium, and calcium. Although the cost is low, they need to be dehydrated before preparing the electrolyte and cannot be added to the battery system as an additive for operation.

[0116] Dicyclohexylcarbodiimide water-removing additives have low costs, but the hydrolysis product amide precipitate is toxic to the battery; its optimized products diisopropylcarbodiimide and 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride, although the hydrolysis products are harmless to the battery system, the cost increases sharply, which is not conducive to large-scale market application and promotion (the yield of this type of product is low and the presence of chiral molecules and asymmetric molecules makes separation and purification difficult. The purified high-purity material is very prone to decomposition reactions and requires the addition of stabilizers, which further increases the cost, especially in high-concentration purification and preservation. It costs extremely high; it is more than 100 times more than the additive of the present application, and is an extremely high-cost high-efficiency additive. It is not within the acceptable cost range for large-scale production in the market, and the application market is limited or there is basically no possibility of large-scale application).

[0117] Phosphorus pentoxide, isocyanate, and thiocyanate dewatering additives have problems with toxicity, corrosiveness, and battery compatibility, and still need to be improved or optimized; hexamethyldisilazane additives can meet most of the requirements of dewatering additives, but they are difficult to preserve, expensive, and cause the electrolyte to turn yellow and become more turbid, which still limits their application in high-end electrolyte products.

[0118] The product described in the present application has low-cost raw materials for synthesis, high water-reaction sensitivity, non-toxic hydrolysis products, is compatible with battery systems, and has the potential to become a new type of high-efficiency water-removal additive.

[0119] There are certain water molecules in the commercial standard electrolyte without adding triazines, and the control of water molecules is not ideal after the positive and negative electrode materials are subjected to processes such as slurry coating, cell winding and lamination. After the battery drying process, a certain amount of water molecules will still remain in the positive and negative electrode cells and are difficult to dry out. After the electrolyte is injected, these water molecules will infiltrate and dissolve into the electrolyte system, thereby hydrolyzing with lithium salts such as lithium hexafluorophosphate, causing the acidity of the electrolyte system to increase abnormally. For the electrolyte system that has been standing for a long time, the influence of acidity will gradually cause irreversible phase change and structural damage to the alkaline positive electrode material structure, thereby causing the dissolution of transition metal ions and precipitation on the negative electrode side, affecting the generation of dead sodium and dead lithium and the reaction with the electrolyte to produce gas; the residual water molecules will also directly free at the positive and negative electrodes to participate in electron gain and loss reactions, thereby causing hydrogen and oxygen evolution reactions at the positive and negative electrodes, leading to safety hazards such as swelling and explosion of soft-pack batteries.

[0120] It can be seen that the triazine derivative electrolyte additive developed in this application can effectively inhibit the concentration of water molecules in the electrolyte and the electrode, has positive significance for the structural stability of the positive and negative electrode materials, inhibits the decomposition of the electrolyte salt, and the increase in acidity, and has application value in specific fields.

[0121] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention rather than to limit the scope of protection of the present invention. 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 solution of the present invention can be modified or replaced by equivalents without departing from the essence and scope of the technical solution of the present invention.

Claims

1. A triazine derivative, characterized in that: Having the structure of formula I: Wherein, R1, R2, R3, R4, R5 and R6 are independently selected from bisperfluoroalkylsulfonyl imide groups.

2. The triazine derivative according to claim 1, characterized in that: The R1, R2, R3, R4, R5 and R6 are all the same bisperfluoroalkylsulfonyl imide group.

3. The triazine derivative according to claim 2, characterized in that: The triazine derivatives have a structure of formula I-1:

4. The method for synthesizing a triazine derivative according to any one of claims 1 to 3, characterized in that: The following steps are involved: The polyhalogenated triazine ring skeleton compound shown in formula II is reacted with a perfluorinated compound to obtain a triazine derivative shown in formula I; Wherein, X is a halogen element; and the perfluorinated compound is bisperfluoroalkylsulfonyl imide benzene.

5. The synthesis method according to claim 4, characterized in that The perfluorinated compound is bis-perfluoromethylsulfonyl imide benzene; The preparation of the polyhalogenated triazine ring skeleton compound shown in formula II comprises: subjecting a s-triazine Grignard reagent to an alkylation-like reaction with a monohalogenated s-triazine, and then subjecting the obtained reactant to a perhalogenation reaction with a halogenating reagent to obtain the polyhalogenated triazine ring skeleton compound.

6. The synthesis method according to claim 5, characterized in that In the perhalogenation reaction of the reactant and the halogenation reagent, the molar ratio of the reactant to the halogenation reagent is controlled to be 1:(6-20); The molar ratio of the polyhalogenated triazine ring skeleton compound represented by formula II to the perfluorinated compound is 1:(6-20), and the tert-butanol solution of lithium tert-butoxide is used as the reaction solvent.

7. Use of the triazine derivative according to any one of claims 1 to 3 as a water removal additive in a secondary battery, wherein the secondary battery includes but is not limited to a lithium-sulfur battery, a lithium battery, a sodium-sulfur battery or a sodium battery.

8. The use according to claim 7, characterized in that: The secondary battery may be in the form of, but not limited to, one or more of, button batteries, soft-pack batteries, square batteries, steel-shell batteries, aluminum-shell batteries, and 18650 batteries.

9. An electrolyte, characterized in that: The triazine derivative according to any one of claims 1 to 3 is used as an additive.

10. The electrolyte according to claim 9, characterized in that The electrolyte includes a carbonate mixture, an ether mixture, a sulfone mixture or a nitrile mixture; and the amount of the triazine derivative added to the electrolyte is 0.01wt%-5wt%.

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