Flame-retardant sodium ion battery electrolyte, preparation method and battery

Abstract

A flame-retardant sodium ion battery electrolyte solves the problem that the current sodium battery flame-retardant electrolyte lacks high flame retardancy and electrochemical compatibility. The electrolyte is composed of the following components: 0.5-2 mol / L sodium salt, carbonate organic solvent or sulfonate organic solvent, and 1-30% by mass of flame retardant additive.

Description

Technical Field

[0001] The present invention relates to the technical field of battery materials, and in particular to a flame-retardant sodium ion battery electrolyte, a preparation method and a battery. Background Art

[0002] With the rapid development of wind power generation and solar power generation technology, the demand for high-capacity energy storage stations is increasing year by year. Sodium batteries are low-priced, have a high voltage similar to lithium, have a low self-discharge rate, and have a high energy density. Compared with lithium-ion batteries, sodium-ion batteries have significant advantages in a wide operating temperature range. They are more likely to gradually replace the current mainstream lead-acid liquid flow battery energy storage facilities and continue to expand their application areas and market share.

[0003] However, since the electrolyte used in sodium batteries is a flammable carbonate mixed solvent system, when the battery is overcharged, short-circuited or heated, the battery may catch fire, burn or explode, thus causing a safety accident. The safety risks of sodium batteries have always been our primary concern.

[0004] Compared with sodium-ion batteries, lithium-ion batteries developed earlier, and there are more studies on the safety of lithium-ion batteries. In order to improve the safety of lithium batteries, US Patents US6589697, US6924061 and US6589697 reported the use of trimethyl phosphate (TMP), triphenyl phosphate (TPP), tributyl phosphate (TBP), trifluoroethyl phosphate (TFFP) and other phosphates or fluoroethers or esters as flame retardant additives for electrolytes to reduce the flammability of electrolytes. However, there are very few studies on flame-retardant electrolytes for sodium batteries. Therefore, it is necessary to develop new sodium-ion battery electrolyte solutions with high flame retardancy and good electrochemical compatibility. Summary of the invention

[0005] In view of the above situation, in order to overcome the defects of the prior art, the present invention provides a flame retardant sodium ion battery electrolyte, a preparation method and a battery, which effectively solves the problem that the current sodium battery flame retardant electrolyte lacks high flame retardancy and electrochemical compatibility.

[0006] To achieve the above purpose, the technical solution of the present invention is: a flame retardant sodium ion battery electrolyte, which is composed of the following components in concentration: 0.5-2 mol / L of sodium salt, carbonate organic solvent or sulfonate organic solvent, and 1-30% by mass of a flame retardant additive.

[0007] Preferably, the general structural formula of the flame retardant additive is as shown in I and II:

[0008] ; ;

[0009] (I) (II) ;

[0010] Wherein, R 1 -R 2 can all be alkyl, halogenated alkyl, halogenated olefin, biphenyl, halogenated biphenyl, alkyl silicon, alkyl phosphate or amide.

[0011] Preferably, the sodium salt is a mixture of one or more of NaPF 6 , NaN(SO 2 CF 3 ) 2 , NaFSI, or NaSO 3 CF 3 .

[0012] Preferably, the cyclic carbonate compound is one or a mixture of dimethyl carbonate, ethylene carbonate, propylene carbonate, ethyl methyl carbonate, fluoroethylene carbonate, vinyl sulfate, 1,3-propane sultone or vinylene carbonate.

[0013] The preparation method of the flame retardant sodium ion battery electrolyte is as follows: dissolving a flame retardant additive in an organic solvent after water is removed, and then adding sodium salt to the organic solvent containing the flame retardant additive in an anhydrous and oxygen-free environment to prepare electrolytes of different concentrations.

[0014] Preferably, the sodium salt is slowly added in batches to the organic solvent containing the flame retardant additive.

[0015] Preferably, the dehydration is accomplished by dehydrating with 4A sodium molecular sieve for 50-80 hours.

[0016] A battery comprises a positive electrode, a negative electrode, a separator and the above-mentioned sodium ion battery electrolyte.

[0017] Compared with the prior art, the present invention has the following benefits: 1. Compounds containing fluorinated cyclotriphosphazene groups have good flame retardant properties and little effect on electrochemical properties, and can be used as new electrolyte flame retardant additives; and the alkoxy or amino substituents of R1 and R2 can form stable five-membered rings or six-membered rings with adjacent phosphorus atoms, which increases the stability of the flame retardant and improves the flame retardant effect. 2. By adding flame retardant additives to the electrolyte solution, the flammability of the electrolyte can be greatly reduced. After the electrolyte of the present invention is applied to sodium batteries, the possibility of combustion of the electrolyte can be reduced to zero. 3. This electrolyte has the characteristics of high efficiency flame retardant effect, low viscosity, low toxicity, and a wide electrochemical window and temperature range; sodium batteries using this electrolyte not only have good safety, but also their electrochemical properties are almost unaffected. Therefore, this type of sodium ion battery has a wider application market in the field of energy storage. DETAILED DESCRIPTION

[0018] Example 1

[0019] Preparation process of ethylenedioxytetrafluorocyclotriphosphazene:

[0020] First, 600 ml of THF, 300 g of hexachlorocyclotriphosphazene, 238 g of potassium carbonate, and 54.5 g of ethylene glycol were added in sequence to a 2-liter four-necked bottle, and refluxed for 4 h. The filter cake was filtered out and the filtrate was distilled to obtain 230 g of ethylenedioxytetrachlorocyclotriphosphazene. Then, 500 ml of acetonitrile and 200 g of ethylenedioxytetrachlorocyclotriphosphazene intermediate were added in sequence to a 2-liter four-necked bottle. 112 g of NaF was added in batches under mechanical stirring. After the addition was completed, the mixture was refluxed for 7 hours, filtered, and the filter cake was distilled to obtain 145 g of ethylenedioxytetrafluorocyclotriphosphazene.

[0021] Example 2

[0022] Preparation process of biphenyldioxytetrafluorocyclotriphosphazene:

[0023] First, 600 ml of THF, 200 g of hexachlorocyclotriphosphazene, 159 g of potassium carbonate, and 107 g of 2,2'-dihydroxybiphenyl were added to a 2-liter four-necked bottle in sequence, and the mixture was refluxed for 6 h. The filter cake was filtered out and the filtrate was distilled to obtain 205 g of biphenyldioxytetrachlorocyclotriphosphazene tetrachlorocyclotriphosphazene. Then, 800 ml of acetonitrile and 150 g of biphenyldioxytetrachlorocyclotriphosphazene intermediate were added to a 2-liter four-necked bottle in sequence. 61.5 g of NaF was added in batches under mechanical stirring. After the addition was completed, the mixture was refluxed for 5 h, filtered, and the filter cake was distilled to obtain 110 g of biphenyldioxytetrafluorocyclotriphosphazene.

[0024] Example 3

[0025] Preparation process of ethylenediamine tetrafluorocyclotriphosphazene:

[0026] First, 600 ml of THF, 250 g of hexachlorocyclotriphosphazene, 199 g of potassium carbonate, and 43.2 g of ethylenediamine were added to a 2-liter four-necked bottle in sequence, and the mixture was refluxed for 4 h. The filter cake was filtered out and the filtrate was distilled to obtain 200 g of ethylenediamine tetrachlorocyclotriphosphazene. Then, 450 ml of acetonitrile and 150 g of ethylenedioxytetrachlorocyclotriphosphazene intermediate were added to a 2-liter four-necked bottle in sequence. 85 g of NaF was added in batches under mechanical stirring. After the addition was completed, the mixture was refluxed for 5 h, filtered, and the filter cake was distilled to obtain 100 g of ethylenediamine tetrafluorocyclotriphosphazene.

[0027] Example 4

[0028] Preparation process of biphenyl diamino tetrafluorocyclotriphosphazene:

[0029] First, 600 ml of THF, 200 g of hexachlorocyclotriphosphazene, 160 g of potassium carbonate, and 106 g of 2,2'-diaminobiphenyl were added to a 2-liter four-necked bottle in sequence, and the mixture was refluxed for 4.5 h. The filter cake was filtered out and the filtrate was distilled to obtain 200 g of biphenyldioxytetrachlorocyclotriphosphazene tetrachlorocyclotriphosphazene. Then, 800 ml of acetonitrile and 100 g of biphenyldiaminotetrachlorocyclotriphosphazene intermediate were added to a 2-liter four-necked bottle in sequence. 41.2 g of NaF was added in batches under mechanical stirring. After the addition was completed, the mixture was refluxed for 5 hours, filtered, and the filter cake was distilled to obtain 70 g of biphenyldioxytetrafluorocyclotriphosphazene.

[0030] Preparation process of electrolyte:

[0031] The flame retardant additive is dissolved in the organic solvent after the water is removed, and then the sodium salt is added to the organic solvent containing the flame retardant additive in an environment without water and oxygen to prepare electrolytes of different concentrations. The sodium salt should be added to the organic solvent containing the flame retardant additive slowly in batches to prevent the heat released during the addition process from overheating and causing the solvent to boil.

[0032] Table 1 lists the composition of four flame-retardant electrolyte solutions and the test data of the self-extinguishing time of each electrolyte solution.

[0033] Serial number Component A sodium salt (molar concentration in electrolyte mol / L) Component B solvent (volume ratio of various components in the electrolyte) Component C flame retardant additive (mass ratio %) Self-extinguishing time (seconds) 1 NaPF6(1M) EMC / PC(1:1) Ethylenedioxytetrafluorocyclotriphosphazene (5) 0 2 NaPF6(1M) EMC / PC(1:1) Ethylenediamine tetrafluorocyclotriphosphazene (7) 0 3 NaPF6(1M) EMC / PC(1:1) Biphenyldioxytetrafluorocyclotriphosphazene (5) 0 4 NaPF6(1M) EMC / PC(1:1) Biphenyldiaminotetrafluorocyclotriphosphazene (10) 0

[0034] As shown in Table 1, adding 5% of ethylenedioxytetrafluorocyclotriphosphazene or biphenyldioxytetrafluorocyclotriphosphazene to an electrolyte of methyl ethylene carbonate and propylene carbonate in a volume ratio of 1:1 containing 1 mol / L NaPF6 can achieve complete non-flammability.

[0035] The embodiments are merely examples for the purpose of clear explanation, and are not intended to limit the implementation methods. For those skilled in the art, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to list all the implementation methods here. The obvious changes or modifications derived therefrom are still within the scope of protection of the invention.

Claims

1. A flame retardant sodium ion battery electrolyte, It is characterized in that The composition is composed of the following components in concentrations: 0.5-2 mol / L sodium salt, carbonate organic solvent or sulfonate organic solvent, and 1-30% by mass of flame retardant additive; The general structural formulas of the flame retardant additives are shown in I and II: Wherein, R1-R2 can all be alkyl, halogenated alkyl, halogenated olefin, biphenyl, halogenated biphenyl, alkyl silicon, alkyl phosphate or amide.

2. A flame retardant sodium ion battery electrolyte according to claim 1, It is characterized in that The sodium salt is a mixture of one or more of NaPF6, NaN(SO2 CF3)2, NaFSI, or NaSO3 CF3.

3. A flame retardant sodium ion battery electrolyte according to claim 1, It is characterized in that The carbonate organic solvent or sulfonate organic solvent is one or a mixture of dimethyl carbonate, ethylene carbonate, propylene carbonate, ethyl methyl carbonate, fluoroethylene carbonate, 1,3-propane sultone or vinylene carbonate.

4. The method for preparing the flame-retardant sodium ion battery electrolyte according to any one of claims 1 to 3 is as follows: dissolving the flame retardant additive in an organic solvent after dehydration, and then adding the sodium salt to the organic solvent containing the flame retardant additive in an anhydrous and oxygen-free environment to prepare electrolytes of different concentrations.

5. The preparation method according to claim 4, It is characterized in that The sodium salt is slowly added in batches into the organic solvent containing the flame retardant additive.

6. The preparation method according to claim 4, It is characterized in that The water removal is accomplished by using 4A sodium molecular sieve for 50-80 hours.

7. A battery comprising a positive electrode, a negative electrode, a separator and the sodium ion battery electrolyte according to any one of claims 1 to 3.

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