CN111224165B - Preparation method of flame-retardant lithium salt with high organic compatibility and composite flame-retardant electrolyte thereof - Google Patents
Preparation method of flame-retardant lithium salt with high organic compatibility and composite flame-retardant electrolyte thereof Download PDFInfo
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Abstract
The invention discloses a lithium with an isocyanuric acid ring, which is easily dissolved in an organic solvent and has a flame retardant functionSalt (R-Ar-O) n (‑C(O)N‑) 3 (PO 3 Li 2 ) 3‑n Wherein (-C (O) N-) 3 Is an isocyanuric acid ring group; n =1 or 2; r = C 1 ～C 8 Alkyl, alkenyl of (a); ar is selected from benzene ring, naphthalene ring, five-membered or six-membered heterocyclic ring; lithium salt and its phosphate intermediate [ (R-Ar-O) n (‑C(O)N‑) 3 (PO 3 R’ 2 ) 3‑n ](R' is methyl, ethyl or isopropyl) is prepared by compounding the following components in a mass ratio of (10) - (1), wherein the electrolyte additive is easy to dissolve in an organic solvent, and the mass ratio concentration of the electrolyte additive is 8% -40% of that of the electrolyte additive in the organic solvent, so that a flame-retardant electrolyte is obtained, the conductivity and the flame-retardant performance of lithium ion are considered, and the flame-retardant electrolyte can be used in lithium ion batteries, lithium sulfur batteries, lithium fluorocarbon batteries or lithium oxygen batteries.
Description
Technical Field
The invention relates to a preparation method of flame-retardant lithium salt and a composite electrolyte thereof for a lithium battery, belonging to the field of battery materials. Can be used as flame-retardant composite electrolyte for lithium ion batteries, lithium oxygen batteries and lithium sulfur batteries.
Technical Field
The lithium secondary battery mainly comprises a lithium ion battery, a lithium oxygen battery and a lithium sulfur battery, has the advantages of high working voltage, large specific power, small self-discharge, no memory effect and the like, has become a hot spot of current secondary battery research and development, and has been widely applied to the fields of power sources and the like. Lithium batteries generally consist of positive/negative electrodes, a separator and an electrolyte. Among them, the electrolyte of the conventional lithium battery is composed of an organic solvent and a lithium salt, and has important influences on the output voltage, rate capability, applicable temperature range, cycle performance, safety performance and the like of the battery. And the organic solvent tends to have high activity, high volatility and inflammability, and is easy to cause combustion or explosion when the battery leaks. In order to achieve both safety and battery performance, it is necessary to add a flame retardant to improve the safety of the lithium secondary battery.
Due to their low viscosity and high solubility requirements, organophosphate flame retardant additives such as dimethyl methylphosphonate (DMMP), diethyl ethylphosphonate (DEEP), and the like, are commonly used. However, the organophosphates have disadvantages of low flame-retardant efficiency and poor electrochemical compatibility with electrode materials. In order to obtain a completely non-flammable electrolyte, the phosphate addition proportion generally needs to exceed 40% by weight. A high content of phosphate in the electrolyte results in a decreased concentration of lithium ions in the electrolyte and a low charge/discharge performance of the graphite anode, thereby causing a rapid decrease in electrochemical performance. The basic requirement of the additive is that the flame retardant is incorporated into the electrolyte without adversely affecting the electrochemical performance of the lithium battery. For example, patent document CN 107293790A discloses a flame retardant lithium ion battery electrolyte, a fluoro alkoxy silicon based polyphosphazene flame retardant, which contains P, N, si, F and other flame retardant elements in cooperation to make the flame retardant efficiency high, and phosphazene can be degraded by heat to generate phosphate, metaphosphate, polyphosphate and non-flammable gas, and a non-volatile protective film is formed on the surface of the flame retardant material to isolate air, thereby inhibiting combustion. However, the addition of the flame retardant inevitably causes the reduction of the lithium salt content in the electrolyte, and the problem that the high-rate transmission of the lithium ion battery is influenced due to the low lithium ion concentration exists.
In addition, lithium hexafluorophosphate (LiPF 6) is one of the most widely used electrolyte lithium salts in currently commercialized lithium ion batteries, has high conductivity and a wide electrochemical stability window, and is capable of forming an SEI film on a carbon negative electrode. However, the lithium hexafluorophosphate has complex synthesis process, is easy to decompose under heating and sensitive to trace water, needs production links such as strong corrosion protection and the like, is easy to hydrolyze, has high requirements on equipment and operation, and greatly improves the production cost and the process complexity.
In conclusion, the design idea of the high-safety lithium ion battery electrolyte can be started from two aspects: (1) lithium salt modification: firstly, anions in lithium salt are main factors determining physical and chemical properties of electrolyte, but the existing material has poor general stability, and modification becomes a problem to be solved urgently; and (2) the use of additives. But there are significant disadvantages to the single use of both strategies. Therefore, the development of organic lithium phosphonate with an organic-inorganic hybrid structure as a composite electrolyte additive can achieve both high ionic conductivity and high flame retardant property of the electrolyte.
The patent provides a preparation method of aromatic hydrocarbon organic group modified high phosphate flame-retardant lithium salt with high organic compatibility, and the application of the flame-retardant electrolyte additive formed by compounding the lithium salt and intermediate esters thereof in different lithium batteries is researched. At present, no such lithium salt has been reported. The phosphoric acid group combined by the nitrogen-containing trichloroisocyanuric acid forms an N-P synergistic flame retardant effect, and the aromatic hydrocarbon organic group modification can obviously improve the solubility of lithium salt in an organic solvent, so that higher lithium ion concentration is provided for realizing high-rate cycle performance. We further provide a composite electrolyte additive compounded by lithium salt and phosphate ester intermediates thereof, which remarkably improves the flame retardant property.
The invention content is as follows:
in order to improve the concentration of lithium ions in an electrolyte by improving the compatibility of lithium salt and an organic solvent while realizing the flame retardant property, the invention provides a high phosphate flame retardant lithium salt modified by aromatic organic groups and a preparation method of a composite electrolyte thereof. The flame retardant has the advantages that:
(1) Aromatic hydrocarbon organic groups and phosphites replace active chlorine on the trichloroisocyanuric acid organic monomer, and a large number of aromatic hydrocarbon groups improve the solubility of lithium salt in an organic solvent;
(2) The balance between conductivity and solubility is achieved by regulating the types of aromatic hydrocarbon groups in the lithium salt and the proportion of the aromatic hydrocarbon groups to phosphate groups, the high solubility in an organic solvent promotes the dissociation of lithium ions on molecules, and the problem of the reduction of the concentration of the lithium ions caused by the addition of a flame retardant is solved;
(3) The large pi bond of the aromatic hydrocarbon group has pi-pi interaction with the graphite-based negative electrode, so that the wettability of the electrode and the formation of an SEI film are improved; (4) Lithium salt [ (R-Ar-O) n (-C(O)N-) 3 (PO 3 Li 2 ) 3-n ]With their intermediate esters [ (R-Ar-O) n (-C(O)N-) 3 (PO 3 R’ 2 ) 3-n ]The flame-retardant electrolyte lithium salt additive is obtained by compounding, has better compatibility, higher phosphate group content and-C (O) N-group, and can better exert the flame-retardant performance.
The flame-retardant lithium salt, the organic solvent and other functional additives are compounded to prepare the electrolyte for the lithium battery, and the flame-retardant electrolyte has the advantages that:
(1) The high solubility of lithium salt improves the content of effective lithium ions in electrolyte, the concentration of lithium salt in organic solvent can reach 40wt%, and the solubility can be further improved by regulating the length of aromatic hydrocarbon group and alkyl chain;
(2) The higher effective lithium ion content brings better rate cycling stability, and meets the requirement of long-term use;
(3) The electrolyte system has low requirement on the environment in the preparation process, and the problem that lithium hexafluorophosphate is sensitive to water is avoided;
(4) The compounded electrolyte has a nitrogen-phosphorus synergistic flame retardant effect, and the application range is wider;
(5) In the compound [ (R-Ar-O) n (-C(O)N-) 3 (PO 3 R’ 2 ) 3-n ]The component has good solubility in organic solvent and good flame retardant property, and the addition of the component is to improve the flame retardant property.
The preparation process route of the flame-retardant lithium salt is as follows:
1) Dissolving trichloroisocyanuric acid (TCCA) as a main body in a specific solvent such as anhydrous xylene, adding a certain amount of matched phosphite ester under the ice bath condition, continuously heating to 80-100 ℃, carrying out nucleophilic substitution reaction, and replacing active chlorine to obtain phosphate ester partially-substituted [ Cl ] n (-C(O)N-) 3 (PO 3 R’ 2 ) 3-n ]A precursor; continuously substituting residual chlorine on the precursor by alkyl aromatic phenol sodium salt (R-Ar-ONa) to obtain an intermediate [ (R-Ar-O) n (-C(O)N-) 3 (PO 3 R’ 2 ) 3-n ](ii) a Hydrolysis of phosphate group since phenolic ether bond is acid-sensitive, lithium salt [ (R-Ar-O) can be obtained in one step by alkaline hydrolysis of lithium hydroxide n (-C(O)N-) 3 (PO 3 Li 2 ) 3-n ](ii) a Or alkaline hydrolysis with sodium hydroxide to obtain sodium phosphate [ (R-Ar-O) n (-C(O)N-) 3 (PO 3 Na 2 ) 3-n ]Cation exchange with a cation exchange resin to give [ (R-Ar-O) n (-C(O)N-) 3 (PO 3 H 2 ) 3-n ]Then lithium hydroxide is used for reaction to obtain lithium salt [ (R-Ar-O) n (-C(O)N-) 3 (PO 3 Li 2 ) 3-n ]。
2) According to the requirements of use, lithium salt [ (R-Ar-O) is mixed according to a certain proportion n (-C(O)N-) 3 (PO 3 Li 2 ) 3-n ]With intermediates [ (R-Ar-O) n (-C(O)N-) 3 (PO 3 R’ 2 ) 3-n ]And compounding, wherein the compound is used as a flame-retardant lithium battery electrolyte additive.
3) Dissolving the electrolyte additive obtained in the step 2) in organic solvents matched with different batteries to obtain a flame-retardant electrolyte; the electrolyte not only has certain flame retardant property, but also has better compatibility with electrodes. The electrolyte additive can be applied to lithium ion batteries, lithium oxygen batteries, lithium sulfur batteries and lithium carbon fluoride batteries.
The preparation method comprises the following steps:
(1) Partially phosphate-substituted [ Cl n (-C(O)N-) 3 (PO 3 R’ 2 ) 3-n ]Preparation of
Weighing 0.1mol of trichloroisocyanuric acid (23.2 g) and 0.2mol of triethyl phosphite (23.2 g), respectively dissolving into 100mL of dimethylbenzene (dried), mixing the two solutions in a 500mL three-neck flask under ice bath and stirring conditions, connecting a condensing and heating device, heating to 80-100 ℃, reacting for 48-10 h, cooling, evaporating and concentrating to 50mL, washing with 100mL of petroleum ether (boiling range of 30-60 ℃) for 2-3 times to remove unreacted raw materials, separating out a large amount of solids, performing suction filtration, drying the solids at 60-80 ℃ in a vacuum drying oven to obtain a solid powdery product [ Cl (-C (O) N- ]) 3 (PO 3 Et 2 ) 2 ]。
The same method is adopted, and the raw materials with different molar ratios are proportioned to obtain [ Cl ] n (-C(O)N-) 3 (PO 3 Et 2 ) 3-n ](n is 1 or 2). The reaction equation is as follows:
(2) Intermediate [ (R-Ar-O) n (-C(O)N-) 3 (PO 3 R’ 2 ) 3-n ]Synthesis of
In a three-necked flask equipped with electric stirring, a condenser and a nitrogen blanket, 0.1mol (43.5 g) of [ Cl (-C (O) N-) obtained in step (1) was weighed 3 (PO 3 Et 2 ) 2 ]Dissolving in 1, 4-dioxane, slowly adding dropwise into 0.11mol (17.38 g) of 1, 4-dioxane solution of sodium salt of p-isopropylphenol, stirring at 100 deg.C for 4 hr to react, cooling, neutralizing with glacial acetic acid to neutrality, standing in ice water bath, cooling, precipitating crystal, vacuum filtering to obtain crude product, and recrystallizing with 1, 4-dioxane to obtain purified [ ((CH) 3 ) 2 CH-ph-O)(-C(O)N-) 3 (PO 3 Et 2 ) 2 ]And (3) powder.
Adopting the same method and different molar ratios of raw materials to obtain [ ((CH) 3 ) 2 CH-ph-O) n (-C(O)N-) 3 (PO 3 Et 2 ) 3-n ](n is 1 or 2). The reaction equation is as follows:
(3) Lithium salt [ (R-Ar-O) n (-C(O)N-) 3 (PO 3 Li 2 ) 3-n ]Preparation of
Intermediate [ (R-Ar-O) n (-C(O)N-) 3 (PO 3 R’ 2 ) 3-n ]The hydrolysis reaction of the flame-retardant lithium salt [ (R-Ar-O) n (-C(O)N-) 3 (PO 3 Li 2 ) 3-n ]
[ method one ] hydrolysis in lithium hydroxide solution
Adding a certain amount of [ ((CH) into a three-neck flask with an electric stirring and condensing tube 3 ) 2 CH-ph-O)(-C(O)N-) 3 (PO 3 Et 2 ) 2 ]Dispersing the solution into excessive (the molar ratio is 1.5-2.0) 2mol/L lithium hydroxide solution, heating to 80 ℃, stirring, and refluxing for 24 hours; cooling, taking out, and evaporatingConcentrating to 20mL, removing generated ethanol to obtain crude product, and recrystallizing the crude product with mixture of ethanol and water twice to obtain [ ((CH) 3 ) 2 CH-ph-O)(-C(O)N-) 3 (PO 3 Li 2 ) 2 ]And (3) powder. And exchanging the mother liquor by using cation exchange resin to collect and recover lithium ions.
[ method two ]]Hydrolysis in sodium hydroxide solution. In the same manner as in the first method, the sodium hydroxide solution is replaced with a lithium hydroxide solution to obtain [ ((CH) 3 ) 2 CH-ph-O)(-C(O)N-) 3 (PO 3 Na 2 ) 2 ]The solution is prepared and exchanged for 24h with cation exchange resin to obtain acid structure [ ((CH) 3 ) 2 CH-ph-O)(-C(O)N-) 3 (PO 3 H 2 ) 2 ]The lithium salt is obtained by reaction and exchange with equimolar lithium hydroxide (controlling the pH of the solution = 9-11), and the product [ ((CH) is obtained after purification 3 ) 2 CH-ph-O)(-C(O)N-) 3 (PO 3 Li 2 ) 2 ]. Compared with the first method, the second method has more advantages in controllability and cost.
The same method is adopted, and the raw material proportions with different molar ratios are adopted to obtain [ ((CH) 3 ) 2 CH-ph-O) n (-C(O)N-) 3 (PO 3 Li 2 ) 3-n ](n is 1 or 2). The reaction equations for method one and method two are as follows:
by the above method, other phenoxide is used to replace isopropylphenylphenolate (other phenoxide is aromatic phenoxide (R-Ar-ONa) R is C 1 ～C 8 Alkyl group of (C), CH 2 ＝CH-(CH 2 ) n - (n =1 to 6); ar is selected from one or more of ph-, naphthyl, disubstituted naphthyl, furyl, pyridyl, pyrazinyl, thienyl, imidazolyl and benzimidazolyl. Other phenoxide substituted products can be obtained.
(4) Research on compounding process of electrolyte additive
[(R-Ar-O) n (-C(O)N-) 3 (PO 3 Li 2 ) 3-n ]Lithium salt and [ (R-Ar-O) n (-C(O)N-) 3 (PO 3 R’ 2 ) 3-n ]Mixing and compounding the intermediate in a mass ratio of 10; dissolved in a suitable organic solvent. The solvents used were: one or more of methyl carbonate, ethyl carbonate, propyl carbonate, ethylene carbonate, fluoroethylene carbonate, dimethyl sulfoxide, dimethylformamide, dimethylacetamide, N-methylpyrrolidone, 1, 3-dioxolane and ethylene glycol dimethyl ether is used as a solvent of the electrolyte. As a flame retardant lithium battery electrolyte.
(5) Preparation and testing of functionalized electrolytes
(a) Preparation of functionalized electrolytes
Adding a series of additives of the lithium ion battery into the flame-retardant electrolyte additive obtained by compounding in the step (4), such as: an overcharge-preventing additive, such as diacetyl ferrocene, a transition metal complex of bigeminal, terpyridyl or phenanthroline, anisyl ether, cyclohexylbenzene and one or a mixture of more of N-phenyl maleic amide, wherein the addition mass ratio is 6-25%; additives that promote SEI film generation: for example, one or a mixture of more of fluoroethylene carbonate, fluoropropylene carbonate, nonafluorobutylethyl ether, butyl sultone, 1, 3-propyl sultone, vinyl trimethoxy silane, 2-phenylimidazole and 4-fluorophenyl isocyanate is used as an additive, and the addition mass ratio is 4-20%.
(b) Performance testing of the electrolyte
Testing various physical and chemical performance indexes of the electrolyte: such as viscosity, flame retardant properties, lithium ion conductivity, etc. The formula and compounding process of the electrolyte are improved through performance tests. So as to find a preparation process of the electrolyte with more excellent performance.
(6) Battery assembly and performance testing
The performance, the initial generation performance, the charge and discharge performance with different multiplying powers, the cycle stability, the overheating resistance and the puncture resistance of the battery, the overcharge resistance of the battery and the like are tested by assembling the battery by using the flame-retardant electrolyte.
(7) Assembled lithium sulfur and lithium oxygen cell performance
And (3) assembling the lithium-sulfur battery and the lithium-oxygen battery by using the flame-retardant electrolyte to respectively test the battery performances. Various properties of the flame-retardant electrolyte were examined.
Detailed Description
[ example 1]: partially phosphate-substituted [ Cl n (-C(O)N-) 3 (PO 3 R’ 2 ) 3-n ]Preparation of (2)
With [ Cl (-C (O) N-) 3 (PO 3 Et 2 ) 2 ]Preparation of (D) is as an example
Weighing 0.1mol of trichloroisocyanuric acid (23.2 g) and 0.2mol of triethyl phosphite (23.2 g), respectively dissolving into 100mL of dimethylbenzene (dried), mixing the two solutions in a 500mL three-neck flask under ice bath and stirring conditions, connecting a condensing and heating device, heating to 80-100 ℃, reacting for 4-10 h, cooling, evaporating and concentrating to 50mL, washing with 100mL of petroleum ether (boiling range of 30-60 ℃) for 2-3 times to remove unreacted raw materials, separating out a large amount of solids, performing suction filtration, drying the solids at 60-80 ℃ in a vacuum drying oven to obtain a solid powdery product [ Cl (-C (O) N- ]) 3 (PO 3 Et 2 ) 2 ]。
The [ Cl ] is obtained by adopting the same method and different molar ratios of the raw materials n (-C(O)N-) 3 (PO 3 Et 2 ) 3-n ](n is 1 or 2).
In the same manner as above, other phosphate compounds [ Cl ] can be obtained by replacing ethyl phosphite with other phosphite esters (one or a mixture of trimethyl phosphite, tripropyl phosphite or triisopropyl phosphite) 3 (-CP-) 3 (PO 3 R’ 2 ) 3 ]。
[ example 2]: intermediate [ (R-Ar-O) n (-C(O)N-) 3 (PO 3 R’ 2 ) 3-n ]Synthesis of
By [ ((CH) 3 ) 2 CH-ph-O)(-C(O)N-) 3 (PO 3 Et 2 ) 2 ]Synthesis example (c):
in a three-necked flask equipped with electric stirring, a condenser and a nitrogen blanket, 0.1mol (43.5 g) of [ Cl (-C (O) N-) obtained in step (1) was weighed 3 (PO 3 Et 2 ) 2 ]Dissolving in 1, 4-dioxane, slowly adding 0.11mol (17.38 g) of 1, 4-dioxane solution of sodium salt of p-isopropylphenol dropwise, stirring at 100 deg.C for 4 hr to complete reaction, cooling, neutralizing with glacial acetic acid to neutrality, standing in ice water bath, cooling, precipitating crystal, vacuum filtering to obtain crude product, recrystallizing with 1, 4-dioxane to obtain purified [ ((CH) 3 ) 2 CH-ph-O)(-C(O)N-) 3 (PO 3 Et 2 ) 2 ]And (3) powder.
In the same manner, give [ ((CH) 3 ) 2 CH-ph-O) n (-C(O)N-) 3 (PO 3 Et 2 ) 3-n ]And the raw materials with different molar ratios are mixed (n is 1 or 2).
Wherein, R is selected from: c 1 ～C 8 Alkyl of (C), CH 2 ＝CH-(CH 2 ) n - (n =1 to 6); ar is one or more selected from ph-, -ph-, naphthyl, disubstituted naphthyl, furyl, pyridyl, pyrazinyl, thienyl, imidazolyl and benzimidazolyl. To obtain [ (R-Ar-O) x (-CN-) 3 (PO 3 Et 2 ) 3-x ](x is 1 or 2).
[ example 3]: lithium salt [ (R-Ar-O) n (-C(O)N-) 3 (PO 3 Li 2 ) 3-n ]Preparation of
To [ ((CH) 3 ) 2 CH-ph-O)(-C(O)N-) 3 (PO 3 Li 2 ) 2 ]Synthesis example (c):
[ method one ] hydrolysis in lithium hydroxide solution
Adding a certain amount of [ ((CH) into a three-neck flask with an electric stirring and condensing tube 3 ) 2 CH-ph-O)(-C(O)N-) 3 (PO 3 Et 2 ) 2 ]Dispersing the solution into excessive (the molar ratio is 1.5-2.0) 2mol/L lithium hydroxide solution, heating to 80 ℃, stirring, and refluxing for 24 hours; cooling, taking out, evaporating and concentrating to 20mL, removing generated ethanol,obtaining a crude product, and recrystallizing the crude product twice by using a mixed solution of ethanol and water to obtain [ ((CH) 3 ) 2 CH-ph-O)(-C(O)N-) 3 (PO 3 Li 2 ) 2 ]And (3) powder. And exchanging the mother liquor by using cation exchange resin to collect and recover lithium ions.
[ method two ]]Hydrolysis in sodium hydroxide solution. In the same manner as in the first process, the sodium hydroxide solution is replaced with a lithium hydroxide solution to obtain [ ((CH) 3 ) 2 CH-ph-O)(-C(O)N-) 3 (PO 3 Na 2 ) 2 ]Then the solution is prepared and exchanged for 24h by cation exchange resin to obtain [ ((CH) 3 ) 2 CH-ph-O)(-C(O)N-) 3 (PO 3 H 2 ) 2 ]Reacting the acid structure with equimolar lithium hydroxide (controlling the pH of the solution = 9-11) to obtain a crude lithium salt product, and purifying to obtain a pure lithium salt [ ((CH) 3 ) 2 CH-ph-O)(-C(O)N-) 3 (PO 3 Li 2 ) 2 ]. Compared with the first method, the second method has more advantages in controllability and cost.
In the same manner, give [ ((CH) 3 ) 2 CH-ph-O) n (-C(O)N-) 3 (PO 3 Li 2 ) 3-n ](n is 1 or 2).
[ example 4 ]]: by the above method, other phenoxide is used to replace isopropylphenylphenolate (other phenoxide is aromatic phenoxide (R-Ar-ONa) R is C 1 ～C 8 Alkyl group of (C), CH 2 ＝CH-(CH 2 ) n - (n =1 to 6); ar is selected from ph-, -ph-, naphthyl, disubstituted naphthyl, furyl, pyridyl and pyrazinyl; one or more of thienyl, imidazolyl and benzimidazolyl. Other phenoxide substituted products can be obtained.
The preparation process conditions, yield, solubility, flame retardant properties, conductivity and other data of various lithium salts are shown in table 1.
[ example 5]: research on compounding process of electrolyte additive
[(R-Ar-O) n (-C(O)N-) 3 (PO 3 Li 2 ) 3-n ]Lithium salt and [ (R-Ar-O) n (-C(O)N-) 3 (PO 3 R’ 2 ) 3-n ]Mixing and compounding the intermediate in a mass ratio of 10; dissolved in a suitable organic solvent. The solvents used were: one or more of methyl carbonate, ethyl carbonate, propyl carbonate, ethylene carbonate, fluoroethylene carbonate, dimethyl sulfoxide, dimethylformamide, dimethylacetamide, N-methylpyrrolidone, 1, 3-dioxolane and ethylene glycol dimethyl ether is used as a solvent of the electrolyte. As a flame retardant lithium battery electrolyte.
[ example 6]: preparation of functionalized electrolytes
A series of additives for lithium ion batteries were added to the flame-retardant electrolyte additive compounded in example 5, as follows: an additive for preventing overcharge, such as diacetyl ferrocene, bigeminal, terpyridyl or phenanthroline transition metal complex, anisyl ether, cyclohexylbenzene and one or a mixture of more of N-phenyl maleimide, wherein the addition mass ratio is 6-25%; additives that promote SEI film generation: for example, one or a mixture of more of fluoroethylene carbonate, fluoropropylene carbonate, nonafluorobutyl ethyl ether, butyl sultone, 1, 3-propyl sultone, vinyl trimethoxy silane, 2-phenyl imidazole and 4-fluorophenyl isocyanate is used as an additive, and the addition mass ratio is 4-20%.
[ example 7]: performance testing of the electrolyte
Testing various physical and chemical performance indexes of the electrolyte: such as viscosity, flame retardant properties, lithium ion conductivity, etc. The formula and compounding process of the electrolyte are improved through performance tests. So as to find a preparation process of the electrolyte with more excellent performance.
The test results of various electrolyte formulations, compounding processes, flame retardant properties, conductivity and the like are shown in table 2.
[ example 8]: lithium ion battery assembly and performance testing
The anode material is selected from NCM811 type ternary material (LiNi) 0.8 Co 0.1 Mn 0.1 O 2 ) Mixing with acetylene black and a binder (PVDF) in a mass ratio of 8Drying for 12h to obtain a positive electrode; selecting graphite, super P and PVDF as a negative electrode, mixing the graphite, the super P and the PVDF according to a mass ratio of 85 to 5, coating the mixture on a copper foil, and performing vacuum drying at 60 ℃ for 12 hours to obtain the negative electrode; the electrolyte is 2M of compound electrolyte dissolved in 1V% of propyl carbonate/ethylene carbonate; assembled into a CR2032 coin cell.
The battery is assembled with the flame-retardant electrolyte to test the performance, the initial generation performance, the charge and discharge performance with different multiplying powers, the cycle stability, the overheating resistance and the puncture resistance of the battery, the overcharge resistance of the battery and the like.
[ example 9]: lithium sulfur battery assembly and performance testing
The positive electrode is sulfur simple substance, conductive carbon black and a binder (PVDF) according to the weight ratio of 7:2:1, dispersing in NMP, coating on aluminum foil, and vacuum drying at 60 ℃ for 12h to obtain a positive electrode; the negative electrode is a metal lithium sheet; the electrolyte is 2M of a compound electrolyte additive, is dissolved in 1, 3-dioxolane/glycol dimethyl ether = 1% and 1% of LiNO is added 3 (ii) a Assembling the CR2032 button cell.
[ example 10]: lithium oxygen battery assembly and performance test
The positive electrode is a catalyst (CuCo) 2 O 4 ) With binder (PVDF) according to 8:2, dispersing in NMP, coating on a foamed nickel current collector, and performing vacuum drying at 80 ℃ for 12 hours to obtain a positive electrode; the negative electrode is a metal lithium sheet; the electrolyte is 2M of compound electrolyte additive and equal ratio of methyl carbonate/ethylene carbonate/N-methyl pyrrolidone dissolved in LiPF6 (1); the diaphragm is made of glass fiber paper and Celgard 2320; assembling a CR2032 button cell (19 small holes with the diameter of 1.0mm are uniformly distributed on the surface of the positive shell). After the cell assembly was completed, it was placed in a sealed glass jar (1 atm. Under high-purity oxygen).
And (3) assembling the lithium-sulfur battery and the lithium-oxygen battery by using the flame-retardant electrolyte to respectively test the battery performances. Various properties of the flame-retardant electrolyte were examined.
The performance of various batteries assembled using different electrolytes is shown in table 2, table 3.
TABLE 1 lithium salt [ (R-Ar-o) n (-C(O)N-) 3 (Li 2 o 3 P) 3-n ]Composition, preparation process conditions, yield, solubility, conductivity andflame retardant properties
TABLE 2 electrolyte formulation, conductivity, flame retardant Properties, battery Performance
TABLE 3 lithium-sulfur battery and lithium-oxygen battery performance assembled by different electrolytes
Notes from table 2, table 3:
* The electrolyte formula is as follows: 1: lithium salt [ (N-Bu-ph-O) (-C (O) N-) 3 (Li 2 O 3 P) 2 ]The ester intermediate is (N-Bu-ph-O) (-C (O) N-) 3 (R’ 2 O 3 P) 2 ]The mass ratio of the two is 5:1, the organic solvent is a mixed solvent of ethyl carbonate, propyl carbonate, ethylene carbonate, fluoroethylene carbonate, dimethyl sulfoxide, dimethyl acetamide and N-methyl pyrrolidone, and the mass percentage concentration of the mixed solvent is 30 percent; the varieties and the mass percentage concentrations of other additives are respectively as follows: 3% of diacetyl ferrocene, 3% of anisic ether, 2% of butyl sultone, 2% of 1, 3-propyl sultone and 5% of 2-phenylimidazole.
2: lithium salt [ (CH) 3 (CH 2 ) 6 CH 2 -ph-O) 2 (-C(O)N-) 3 (Li 2 O 3 P)]The ester intermediate is (CH) 3 (CH 2 ) 6 CH 2 -ph-O) 2 (-C(O)N-) 3 (R’ 2 O 3 P)]The mass ratio of the two is 60 percent; the varieties and the mass percentage concentrations of other additives are respectively as follows: 3% of diacetyl ferrocene, 3% of anisic ether, 2% of butyl sultone, 2% of 1, 3-propyl sultone and 5% of 2-phenylimidazole.
3: lithium salt [ (i-Bu-C) 4 H 2 S-O)(-C(O)N-) 3 (Li 2 O 3 P) 2 ]The ester intermediate is (i-Bu-C) 4 H 2 S-O)(-C(O)N-) 3 (R’ 2 O 3 P) 2 ]And the mass ratio of the two is 7:1, using a mixed solvent of ethyl carbonate, propyl carbonate, ethylene carbonate, fluoroethylene carbonate, dimethyl sulfoxide, dimethylacetamide and N-methylpyrrolidone as an organic solvent, wherein the mass percentage concentration of the mixed solvent is 30%; the varieties and the mass percentage concentrations of other additives are respectively as follows: 3% of diacetyl ferrocene, 3% of anisic ether, 2% of butyl sultone, 2% of 1, 3-propyl sultone and 5% of 2-phenylimidazole.
4: lithium salt [ (n-Pr-C) 4 H 2 N 2 -O)(-C(O)N-) 3 (Li 2 O 3 P) 2 ]The ester intermediate is (n-Pr-C) 4 H 2 N 2 -O)(-C(O)N-) 3 (R’ 2 O 3 P) 2 ]The mass ratio of the two is 4; the varieties and the mass percentage concentrations of other additives are respectively as follows: 3% of diacetyl ferrocene, 3% of anisic ether, 2% of butyl sultone, 2% of 1, 3-propyl sultone and 5% of 2-phenylimidazole.
5: lithium salt [ (CH) 2 ＝CH(CH 2 ) 4 -ph-O) 2 (-C(O)N-) 3 (Li 2 O 3 P)]The ester intermediate is (CH) 2 ＝CH(CH 2 ) 4 -ph-O) 2 (-C(O)N-) 3 (R’ 2 O 3 P)]The mass ratio of the two is 10A mixed solvent of pyrrolidone and these solvents, the mass percentage concentration of which is 30%; the varieties and the mass percentage concentrations of other additives are respectively as follows: 3% of diacetyl ferrocene, 3% of anisic ether, 2% of butyl sultone, 2% of 1, 3-propyl sultone and 5% of 2-phenylimidazole.
6: lithium salt [ (CH) 2 ＝CH(CH 2 ) 4 -C 4 H 3 N-O)(-C(O)N-) 3 (Li 2 O 3 P) 2 ]The ester intermediate is (CH) 2 ＝CH(CH 2 ) 4 -C 4 H 3 N-O)(-C(O)N-) 3 (R’ 2 O 3 P) 2 ]The mass ratio of the two is 5, the organic solvent is a mixed solvent of ethyl carbonate, propyl carbonate, ethylene carbonate, fluoroethylene carbonate, dimethyl sulfoxide, dimethyl acetamide and N-methyl pyrrolidone, and the mass percentage concentration of the mixed solvent is 30%; the varieties and the mass percentage concentrations of other additives are respectively as follows: 3% of diacetyl ferrocene, 3% of anisic ether, 2% of butyl sultone, 2% of 1, 3-propyl sultone and 5% of 2-phenylimidazole.
# Lithium ion battery
The invention adopts a commercial ternary lithium ion battery, and the electrolyte is changed into the electrolyte. The performance of the battery is tested by GB/T18287.
& Lithium sulfur battery
Lithium-sulfur battery capacity retention rate test: cycle at 1C for 10 weeks.
Safety performance of battery
The safety performance of all batteries was superior to that of the batteries using commercial electrolytes under various test conditions: for example, the air is not blown when meeting water; the temperature resistance can be improved to 80-100 ℃; the puncture resistance, compression resistance and bending resistance are all greatly improved.
Claims (5)
1. The preparation method of the flame-retardant lithium salt with high organic compatibility and the composite flame-retardant electrolyte thereof is characterized in that: from lithium salts with it (R-Ar-O) n (-C(O)N-) 3 (PO 3 R’ 2 ) 3-n Compounding intermediate phosphonateTo a flame retardant electrolyte; the general structural formula of the lithium salt is as follows: (R-Ar-O) n (-C(O)N-) 3 (PO 3 Li 2 ) 3-n Wherein (-C (O) N-) 3 Is an isocyanuric acid ring group; n =1 or 2; the lithium salt is easily dissolved in an organic solvent and has a flame retardant function, the lithium salt is lithium phosphate of isocyanuric ring partially substituted by alkyl aromatic hydrocarbon oxy, and the solubility of the lithium salt in the organic solvent is improved due to the alkyl aromatic hydrocarbon oxy group; the solubility of the lithium salt in an organic solvent is regulated and controlled by controlling the substitution amount of alkyl arene oxyl in molecules; due to the aromatic ring, the compatibility of the electrode material with the electrode material is improved; because the molecules contain lithium ions which can be ionized, the lithium salt has good lithium ion conductivity; because the molecule contains the phosphonic acid group of isocyanuric acid ring with good flame retardant property, the salt has good flame retardant property; the lithium salt and an intermediate phosphonate
(R-Ar-O) n (-C(O)N-) 3 (PO 3 R’ 2 ) 3-n Compounding to obtain the flame-retardant electrolyte; the preparation process route of the electrolyte is as follows:
(1) 2,4, 6-trichloro-1, 3, 5-trioxy-triazine, namely trichloroisocyanuric acid TCCA, is taken as a raw material, and nucleophilic substitution reaction is carried out between the raw material and phosphorous triester in a specific solvent according to a required molar ratio, wherein the specific solvent is as follows: toluene, xylene, tetrachloroethylene, dioxane; the method is characterized in that: the dissolving performance to TCCA and phosphite triester is good, and inert to two reactants, do not react; preparation to obtain Cl containing partial phosphonate substituted n (-C(O)N-) 3 (PO 3 R’ 2 ) 3-n Continuously substituting residual chlorine on the precursor with alkyl aromatic phenol sodium salt R-Ar-ONa to obtain an intermediate (R-Ar-O) n (-C(O)N-) 3 (PO 3 R’ 2 ) 3-n (ii) a The lithium salt (R-Ar-O) is prepared in one step by alkaline hydrolysis of lithium hydroxide n (-C(O)N-) 3 (PO 3 Li 2 ) 3-n (ii) a Or hydrolyzing in sodium hydroxide solution to obtain sodium phosphate [ (R-Ar-O) n (-C(O)N-) 3 (PO 3 Na 2 ) 3-n ]Cationic ion exchange resinSub-exchanging to obtain (R-Ar-O) n (-C(O)N-) 3 (PO 3 H 2 ) 3-n Then reacting with lithium hydroxide to obtain lithium salt (R-Ar-O) n (-C(O)N-) 3 (PO 3 Li 2 ) 3-n ；
(2) Lithium salt (R-Ar-O) n (-C(O)N-) 3 (PO 3 Li 2 ) 3-n And intermediates
(R-Ar-O) n (-C(O)N-) 3 (PO 3 R’ 2 ) 3-n The mass ratio of (1) to (1) is 10;
(3) Dissolving the flame-retardant electrolyte additive obtained in the step (2) into a proper organic solvent to obtain a flame-retardant electrolyte; the electrolyte has both flame retardant property and lithium ion conductivity, and the compatibility of the electrolyte and an electrode is better; the flame retardant property and the safety performance of the assembled battery are improved.
2. The method for preparing the flame-retardant lithium salt with high organic compatibility and the flame-retardant electrolyte compounded by the same as in claim 1, wherein the phosphite triester is selected from the following components: one or more of trimethyl phosphite, triethyl phosphite, tripropyl phosphite or triisopropyl phosphite, and is characterized in that: the alcohol generated by the hydrolysis reaction has low boiling point and is easy to evaporate and remove; the molar ratio of TCCA to phosphite triester was 1.
3. The method for preparing the lithium salt with high organic compatibility and the composite flame-retardant electrolyte thereof according to claim 1, is characterized in that: r in the alkyl aromatic phenol sodium salt R-Ar-ONa is selected from: c 1 ～C 8 Alkyl group of (C), CH 2 ＝CH-(CH 2 ) n -, where n is selected from: 1 to 6; ar is selected from: one or more of phenyl, disubstituted phenyl, naphthyl, disubstituted naphthyl, furyl, pyridyl, pyrazine, thienyl, imidazolyl and benzimidazolyl.
4. The highly organic compatible flame retardant lithium salt and the composite flame retardant electrolyte thereof according to claim 1The preparation method is characterized by comprising the following steps: (R-Ar-O) n (-C(O)N-) 3 (PO 3 Li 2 ) 3-n And with
(R-Ar-O) n (-C(O)N-) 3 (PO 3 R’ 2 ) 3-n Mixing and compounding according to the mass ratio of 10; the solvents used were: one or more of methyl carbonate, ethyl carbonate, propyl carbonate, ethylene carbonate, fluoroethylene carbonate, dimethyl sulfoxide, dimethyl formamide, dimethyl acetamide and N-methyl pyrrolidone.
5. The method for preparing the lithium salt with high organic compatibility and the composite flame-retardant electrolyte thereof according to claim 1, is characterized in that: (R-Ar-O) n (-C(O)N-) 3 (PO 3 Li 2 ) 3-n And with
(R-Ar-O) n (-C(O)N-) 3 (PO 3 R’ 2 ) 3-n The mass percentage concentration of the compounded flame-retardant electrolyte additive added into the electrolyte is 8-40%.
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