Electrolyte additive and preparation method thereof, electrolyte and lithium ion battery
By adding picric acid as a modifier to the electrolyte, the problem of lithium dendrite precipitation was solved, the cycle performance and stability of lithium-ion batteries were improved, and efficient charging and discharging of the batteries were achieved.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- JIANGSU ZENIO NEW ENERGY BATTERY TECH CO LTD
- Filing Date
- 2023-05-05
- Publication Date
- 2026-06-26
AI Technical Summary
Existing electrolytes are prone to lithium dendrite precipitation, resulting in poor cycle performance of lithium-ion batteries.
By dissolving picric acid in an organic solution containing B, F, and N elements, an electrolyte additive is crystallized out, forming a modified substance containing B, F, or N bonds. This substance is then used in the electrolyte to promote the formation of more LiF, Li3N, etc. in the SEI film, making the polymer layer harder and inhibiting the growth of lithium dendrites.
It effectively suppresses lithium dendrite precipitation, improves the cycle performance and stability of lithium-ion batteries, reduces resistance, and enhances battery cycle life and safety.
Smart Images
Figure CN116525942B_ABST
Abstract
Description
Technical Field
[0001] This application relates to the field of battery technology, and more specifically, to electrolyte additives and their preparation methods, electrolytes, and lithium-ion batteries. Background Technology
[0002] Electrolyte, as a crucial component of lithium-ion batteries, directly affects the overall performance of the battery, including cycle life, rate capability, internal resistance, capacity, and safety. Liquid electrolytes typically consist of lithium salts, organic solvents, and additives. Existing electrolytes have defects that lead to the easy precipitation of lithium dendrites on the electrodes, resulting in poor battery cycle performance.
[0003] Therefore, this application is hereby submitted. Summary of the Invention
[0004] The purpose of this application is to provide an electrolyte additive and its preparation method, an electrolyte, and a lithium-ion battery. The electrolyte with the added electrolyte additive can effectively suppress lithium dendrite precipitation and improve battery cycle performance.
[0005] This application is implemented as follows:
[0006] In a first aspect, this application provides a method for preparing an electrolyte additive, the electrolyte additive being added to the electrolyte of a lithium-ion battery, the method comprising:
[0007] Picric acid is dissolved in an organic solution to obtain an additive solution, wherein the organic solution contains at least one element selected from B, F, and N.
[0008] Electrolyte additives are crystallized from the additive solution.
[0009] In an optional embodiment, the organic solution comprises at least one of an alcohol solution, an ether solution, and a ketone solution.
[0010] In optional embodiments, the alcohol solution includes one or more of the following: tetrafluorop-methoxymethylmethanol, β-sitosterol, 2-bromo-9-methyl-9H-fluoren-9-ol, (1S,4R)-1-methyl-4-(1-methylvinyl)-2-cyclohexen-1-ol, pinacol ester of 4-trifluoromethylbenzylborate, tetramethylpiperidinol, triisopropanolamine, and 2-(5-methylfuran-2-yl)ethanol;
[0011] Ether solutions include one or more of the following: diethyl ether, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, boron trifluoride diethyl ether, tetrafluoroborate diethyl ether, tetrafluoromethyl ether, and tetrahydrofuran;
[0012] Ketone solutions include one or more of 2-phenylchromone, flavonol, 2-hydroxychalcone, N-ethyl-2-pyrrolidone, isophorone, and 2,4-pentanedione.
[0013] In an optional embodiment, the step of dissolving picric acid in an organic solution includes:
[0014] Add picric acid to the organic solution and stir.
[0015] The reaction is carried out under vacuum in a vacuum oven.
[0016] In an optional embodiment, the stirring temperature is 20–30°C and the stirring duration is 6–8 hours.
[0017] In an optional embodiment, the temperature inside the vacuum oven is 60–80°C.
[0018] In an optional embodiment, the step of crystallizing the electrolyte additive from the additive solution includes:
[0019] Electrolyte additives are crystallized and precipitated using at least one of the following methods: rotary evaporator drying, oven drying, vacuum drying under reduced pressure, slow drying in an oil bath, and vacuum drying in a low-temperature container.
[0020] In an optional embodiment, the step of crystallizing the electrolyte additive from the additive solution includes:
[0021] Remove the solvent from the additive solution in an oven at 90–105°C;
[0022] And / or, after vacuuming, remove the solvent from the additive solution at 60–70°C;
[0023] And / or, after heating to above 100°C in a rotary evaporator, stop heating, wrap the oil bath with aluminum foil, cool down to room temperature for 6-8 hours, and then maintain for 24-48 hours to allow the electrolyte additive to crystallize out of the additive solution.
[0024] And / or, vacuum is applied at -5 to -20°C to remove the solvent from the additive solution.
[0025] Secondly, this application provides an electrolyte additive, which is prepared by any of the electrolyte additive preparation methods described in the foregoing embodiments.
[0026] Thirdly, this application provides an electrolyte whose raw materials include the electrolyte additives described in the aforementioned embodiments.
[0027] Fourthly, this application provides a lithium-ion battery including the electrolyte of the aforementioned embodiments.
[0028] This application has the following beneficial effects:
[0029] The method for preparing the electrolyte additive provided in this application includes dissolving picric acid in an organic solution to obtain an additive solution, wherein the organic solution contains at least one element selected from B, F, and N; and crystallizing the electrolyte additive from the additive solution. Since the organic solution contains B, F, and N, these elements can be grafted onto the picric acid structure. The final crystallized electrolyte additive is equivalent to a picric acid-modified substance. This electrolyte additive contains B, F, or N bonds. After being used in the electrolyte, the electrolyte additive can polymerize during battery charging and discharging to form B bonds. x O y (x = n, y = n + 1), and also helps the SEI film generate more LiF, Li3N, etc. These substances can preferentially adsorb at the tips of lithium dendrites, which helps to make the polymer layer and SEI film more rigid and stable, and helps to inhibit the growth of lithium dendrites. The electrolyte with this electrolyte additive can undergo electropolymerization reaction during battery charging and discharging, thereby reducing the loss of electrolyte and lithium metal, reducing the resistance of lithium-ion batteries and thus improving the cycle performance of lithium-ion batteries.
[0030] The lithium-ion battery provided in this application contains the electrolyte with added electrolyte additives, and therefore has lower resistance and better cycle performance. Attached Figure Description
[0031] To more clearly illustrate the technical solutions of the embodiments of this application, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of this application and should not be regarded as a limitation of the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.
[0032] Figure 1 SEM image of the electrolyte lithium anode deposition layer surface in Comparative Example 1;
[0033] Figure 2 This is a SEM image of the surface of the electrolyte lithium anode deposition layer in Example 5 of this application. Detailed Implementation
[0034] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions in the embodiments of this application will be clearly and completely described below. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall apply. Reagents or instruments whose manufacturers are not specified are all conventional products that can be purchased commercially.
[0035] The features and performance of this application will be further described in detail below with reference to the embodiments.
[0036] The preparation method of the electrolyte additive provided in this application includes:
[0037] Step S100: Dissolve picric acid in an organic solution to obtain an additive solution, wherein the organic solution contains at least one element selected from B, F, and N.
[0038] In the embodiments of this application, the organic solution includes at least one of alcohol solutions, ether solutions, and ketone solutions.
[0039] Optionally, the alcohol solution may be one or more of the following: tetrafluorop-methoxymethyl methanol, β-sitosterol, 2-bromo-9-methyl-9H-fluoren-9-ol, (1S,4R)-1-methyl-4-(1-methylvinyl)-2-cyclohexen-1-ol, 4-trifluoromethylbenzylborate pinacol ester, tetramethylpiperidinol, triisopropanolamine, and 2-(5-methylfuran-2-yl)ethanol;
[0040] The ether solution can be one or more of the following: diethyl ether, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, boron trifluoride diethyl ether, tetrafluoroborate diethyl ether, tetrafluoromethyl ether, and tetrahydrofuran.
[0041] The ketone solution can be one or more of the following: 2-phenylchromone, flavonol, 2-hydroxychalcone, N-ethyl-2-pyrrolidone, isophorone, and 2,4-pentanedione.
[0042] The C and H atoms in picric acid can undergo oxidation-reduction reactions, spontaneous reactions, catalytic induction, and similar-like solubility in acidic solutions such as ethers. Solutions containing fluorine, oxygen, nitrogen, boron, and metal ions, or mixtures of these, can be incorporated into the picric acid structure, ultimately improving the protective effect of the electrolyte additive on the negative electrode. Specifically, these components can make the electropolymerization layer more stable and uniform, or participate in the formation of the SEI film with a higher content of LiF, Li₂O, Li₃N, etc.
[0043] Furthermore, the step of dissolving picric acid in an organic solution may specifically include:
[0044] Picric acid was added to the organic solution and stirred; the reaction was carried out under vacuum in a vacuum oven.
[0045] Optionally, the stirring temperature is 20–30°C, and the stirring duration is 6–8 hours. Optionally, the temperature inside the vacuum oven is 60–80°C. Using appropriate stirring temperature, stirring time, and reaction temperature can improve the solubility and functionality of picric acid in organic solutions, and can facilitate the reaction of some functional groups and chemical bonds.
[0046] The resulting additive solution is essentially a modified picric acid solution. Because the additive solution contains B bonds, F bonds, metal ions, or various other functional groups, this substance undergoes electropolymerization during battery charging and discharging, generating B bonds in the polymer layer. x O y (x=n,y=n+1), F element combines with lithium ions in the electrolyte to form LiF. Metal ions can preferentially adsorb at the tip of lithium dendrites, which is beneficial for the polymer layer and SEI film to become harder and more stable, and helps to suppress the growth of lithium dendrites.
[0047] Step S200: Crystallize the electrolyte additive from the additive solution.
[0048] In this embodiment, step S200 may include crystallizing the electrolyte additive using at least one of the following methods: rotary evaporator drying, oven drying, vacuum drying under reduced pressure, slow drying in an oil bath, or vacuum drying in a low-temperature container. Optionally, the crystallinity is controlled between 50% and 65%.
[0049] For example, electrolyte additives can be crystallized and precipitated using the following methods:
[0050] 1) Remove the solvent from the additive solution in an oven at 90-105℃, with a heating rate of 5℃ per minute.
[0051] 2) After vacuuming, remove the solvent from the additive solution at 60-70℃, with a heating rate of 5℃ per minute.
[0052] 3) After heating the rotary evaporator to above 100°C, stop heating, wrap the oil bath with aluminum foil, cool it down to room temperature for 6-8 hours, and then maintain it for 24-48 hours to allow the electrolyte additive to crystallize out of the additive solution.
[0053] 4) Vacuum the solution at -5 to -20°C to remove the solvent from the additive solution; add an appropriate amount of liquid nitrogen and dry ice to ensure uniform crystal formation in the solution, then slowly remove the solvent in 3 to 5 small vacuum cycles and let it stand for 24 to 48 hours.
[0054] The following detailed description, in conjunction with various embodiments, illustrates the effects of the electrolyte additive prepared by the method provided in this application on lithium-ion batteries.
[0055] Example 1
[0056] Dissolve 20 mg of picric acid in 40 mL of 2-(5-methylfuran-2-yl)ethanol by stirring, and dry using a rotary evaporator to obtain an electrolyte additive (crystallization of about 50%).
[0057] 0.5 wt% electrolyte additive was used in the electrolyte base solution (without added electrolyte additives). The lithium salt in the electrolyte base solution was lithium bis(trifluoromethanesulfonyl)imide, with a lithium salt concentration of 1.0 mol / L. -1 The solvent is 1,3-dioxolane and ethylene glycol dimethyl ether, and it contains 0.5 wt% lithium nitrate.
[0058] Example 2
[0059] 10 mg of picric acid was dissolved in 20 mL of boron trifluoride ether by stirring, dried in an oven, and the temperature was increased from an initial 25 °C to 90 °C at a rate of 5 °C per minute and maintained for 6 hours to obtain a powdered electrolyte additive.
[0060] 1 wt% electrolyte additive was used in the electrolyte base solution. The electrolyte base solution was the same as that in Example 1.
[0061] Example 3
[0062] 10 mg of picric acid was dissolved in 20 mL of N-ethyl-2-pyrrolidone by stirring. After vacuum drying under reduced pressure, the temperature was increased from the initial 25 °C to 60-70 °C at a rate of 5 °C per minute and maintained for 6 h to obtain a powdered electrolyte additive.
[0063] 1.2 wt% electrolyte additives were used in the electrolyte base solution. The electrolyte base solution was the same as that in Example 1.
[0064] Example 4
[0065] Dissolve 10 mg of picric acid in 20 mL of 2-bromo-9-methyl-9H-fluorene-9-ol by stirring. After slow drying in an oil bath, transfer the solution to a rotary evaporator for further drying. Increase the temperature from an initial 25°C to 100°C at a rate of 5°C per minute, then stop heating. Wrap the entire oil bath with aluminum foil to slow down the temperature drop. Allow the temperature to drop for 6–8 hours until it reaches room temperature. Then maintain the temperature for 24–48 hours to allow the electrolyte additive to crystallize out (crystallization degree of about 55–60%).
[0066] 1.5 wt% electrolyte additives were used in the electrolyte base solution. The electrolyte base solution was the same as that in Example 1.
[0067] Example 5
[0068] 10 mg of picric acid was dissolved in 30 mL of 4-trifluoromethylbenzylboronic acid pinacol ester solution by stirring. The solution was then vacuum dried in a cryogenic container at -10°C. This method requires the addition of appropriate amounts of liquid nitrogen and dry ice to ensure uniform crystal formation in the solution (crystallization degree approximately 65%). The solvent was then slowly removed in 3–5 portions using a micro-vacuum. After standing for 24–48 hours, the electrolyte additive was obtained.
[0069] 2 wt% electrolyte additives were used in the electrolyte base solution. The electrolyte base solution was the same as that in Example 1.
[0070] Comparative Example 1
[0071] No electrolyte additives are added to the electrolyte, that is, the composition of the electrolyte base is the same as that in Examples 1-5.
[0072] Comparative Example 2
[0073] Add 0.5 wt% picric acid to the electrolyte.
[0074] The electrolytes from the above embodiments and comparative examples were applied to batteries, and their performance was tested. The specific methods are as follows.
[0075] 1. Preparation of positive electrode:
[0076] (1) Lithium iron phosphate, conductive agent, and binder are mixed and stirred at a mass ratio of 8:1:1 according to the formula. Then, NMP solvent is added and mixed evenly to prepare a positive electrode slurry. The positive electrode slurry is then uniformly coated on an aluminum foil coated with a conductive carbon layer at a certain ratio and vacuum dried at 80-120℃ to obtain a positive electrode material coated with an active material layer. The binder is PVDF; the conductive agent is one or more of SP, acetylene black, and graphite.
[0077] (2) The positive electrode material in step 1 is cut into positive electrode sheets by die cutting;
[0078] 2. The negative electrode uses lithium metal sheets.
[0079] 3. Battery Fabrication: A symmetrical battery is fabricated using two lithium metal sheets as counter electrodes. The positive electrode, separator, and negative electrode are assembled together to form the battery, where the separator must completely encapsulate the positive and negative electrodes. Electrolyte is injected into the battery. Finally, a lithium iron phosphate battery is fabricated.
[0080] 4. Battery impedance test:
[0081] Battery impedance was tested at 100Hz after cycling.
[0082] 5. Loop testing:
[0083] At 25±2℃, charge the battery at 1C constant current and constant voltage to 3.65V, with a cutoff current of 0.05C; let it stand for 60 minutes, then discharge it at 1C to 2.5V, and continue the above process until the capacity decays to 80% of the initial capacity, and record the number of cycles.
[0084] Table 1 shows the parameters and test results for each embodiment and comparative example.
[0085] Table 1:
[0086]
[0087] As can be seen from Table 1, the electrolytes of Examples 1-5 of this application, after being applied to batteries, result in a thinner lithium anode deposition thickness compared to the comparative examples; the battery impedance is also lower, indicating better conductivity. Furthermore, the number of cycle times is significantly improved compared to the comparative examples. Therefore, the electrolyte additives provided in the examples of this application can improve the cycle performance of lithium-ion batteries.
[0088] Figure 1 This is a SEM image of the lithium anode deposition layer in Comparative Example 1. From... Figure 1 As can be seen, the irregular growth of lithium dendrites results in a relatively loose and porous deposition layer, which provides a site for adverse chemical reactions between the electrolyte and lithium metal, leading to excessive loss of electrolyte and lithium metal.
[0089] Figure 2 This is a SEM image of the surface of the electrolyte lithium anode deposition layer in Example 5 of this application. From... Figure 2 It can be seen that after using the electrolyte additive of the present application embodiment, the surface of the lithium anode after electropolymerization is more dense, thereby reducing the side reactions between the electrolyte and lithium metal.
[0090] The electrolyte provided in this application embodiment is prepared using electrolyte additives prepared by the above-described method. In addition to its electropolymerization function, the electrolyte additive provided in this application embodiment can participate in the electropolymerization reaction on the negative electrode surface to generate a stronger polymer layer, reducing adverse reactions between the electrolyte and lithium ions, thereby reducing the thickness of the deposition layer on the negative electrode surface and reducing the internal impedance of the battery. The functional groups and chemical bonds contained in the electrolyte additive can partially participate in the negative electrode SEI film reaction, increasing the amount of inorganic substances such as Li₂O, LiF, and Li₃N in the SEI film, making the negative electrode SEI film more robust and effectively inhibiting lithium dendrite growth. Simultaneously, the chemical bonds and functional groups possess a certain electrostatic field, which can form ion channels, promoting uniform lithium ion transport and improving the cycle performance and safety performance of the lithium battery. Furthermore, the preparation process of the electrolyte additive provided in this application embodiment is simple and easy to implement for industrial production.
[0091] In addition, this application embodiment also provides a lithium-ion battery, which includes the electrolyte provided in this application embodiment.
[0092] The above description is merely a preferred embodiment of this application and is not intended to limit this application. Various modifications and variations can be made to this application by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the protection scope of this application.
Claims
1. A method for preparing an electrolyte additive, wherein the electrolyte additive is used to be added to the electrolyte of a lithium-ion battery, characterized in that, The preparation method of the electrolyte additive includes: Picric acid is dissolved in an organic solution to obtain an additive solution, wherein the organic solution contains at least one of an alcohol solution, an ether solution, and a ketone solution, and wherein the organic solution contains at least one element selected from B, F, and N. The electrolyte additive is crystallized from the additive solution.
2. The method for preparing the electrolyte additive according to claim 1, characterized in that, The alcohol solution comprises one or more of the following: tetrafluorop-methoxymethylmethanol, β-sitosterol, 2-bromo-9-methyl-9H-fluoren-9-ol, (1S,4R)-1-methyl-4-(1-methylvinyl)-2-cyclohexen-1-ol, 4-trifluoromethylbenzylborate pinacol ester, tetramethylpiperidinol, triisopropanolamine, and 2-(5-methylfuran-2-yl)ethanol; The ether solution includes one or more of the following: diethyl ether, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, boron trifluoride diethyl ether, tetrafluoroborate diethyl ether, tetrafluoromethyl ether, and tetrahydrofuran. The ketone solution includes one or more of 2-phenylchromone, flavonol, 2-hydroxychalcone, N-ethyl-2-pyrrolidone, isophorone, and 2,4-pentanedione.
3. The method for preparing the electrolyte additive according to claim 1, characterized in that, The steps of dissolving picric acid in an organic solvent include: The picric acid is added to the organic solution and stirred. The reaction is carried out under vacuum in a vacuum oven.
4. The method for preparing the electrolyte additive according to claim 3, characterized in that, The stirring temperature is 20~30℃, and the duration is 6~8h.
5. The method for preparing the electrolyte additive according to claim 3, characterized in that, The temperature inside the vacuum oven is 60~80℃.
6. The method for preparing the electrolyte additive according to claim 1, characterized in that, The step of crystallizing the electrolyte additive from the additive solution includes: The electrolyte additive is crystallized out using at least one of the following methods: rotary evaporator drying, oven drying, vacuum drying under reduced pressure, slow drying in an oil bath, and vacuum drying in a low-temperature container.
7. The method for preparing the electrolyte additive according to claim 6, characterized in that, The step of crystallizing the electrolyte additive from the additive solution includes: The solvent in the additive solution is removed in an oven at 90~105℃; And / or, after vacuuming, remove the solvent from the additive solution at 60~70°C; And / or, after heating to above 100°C in a rotary evaporator, stop heating, wrap the oil bath with aluminum foil, cool down to room temperature for 6-8 hours, and then maintain for 24-48 hours to allow the electrolyte additive to crystallize out of the additive solution; And / or, vacuum is applied at -5 to -20°C to remove the solvent from the additive solution.
8. An electrolyte additive, characterized in that, It is prepared by the method of any one of claims 1 to 7 for preparing electrolyte additives.
9. An electrolyte, characterized in that, The raw materials for its preparation include the electrolyte additives described in claim 8.
10. A lithium-ion battery, characterized in that, Includes the electrolyte as described in claim 9.