Electrolyte applied to high-energy-density lithium ion battery and preparation method thereof
Technical Field
The invention relates to the technical field of lithium ion batteries, in particular to an electrolyte applied to a high-energy-density lithium ion battery and a preparation method thereof.
Background
Lithium ion batteries are rapidly commercialized due to their advantages of high operating voltage, high specific energy, long cycle life, good safety, low self-discharge, and rapid charge and discharge. At present, lithium ion batteries are widely applied to electronic products such as mobile phones, notebook computers, digital cameras and the like, and are also applied to electric tools, electric bicycles and electric automobiles as power batteries.
With the development of power batteries, the anode of the high-energy density lithium ion battery adopts a high-nickel ternary material, and the cathode adopts a silicon-carbon electrode. However, high nickel has nickel ions separated out, gas is easy to generate, and the gas expansion phenomenon occurs, and the silicon-carbon negative electrode is easy to expand to damage a negative electrode SEI film, so that the cycle performance is reduced, and potential safety hazards are caused. The electrolyte is used as an important component of the lithium ion battery, plays a role in conducting lithium ions between the positive electrode and the negative electrode, and has important influence on the electrochemical performance of the lithium ion battery. Functional additives are added into the electrolyte to optimize the components of the electrolyte, and the method is an important way for improving the electrochemical performance of the lithium ion battery.
Disclosure of Invention
The technical problem to be solved by the invention is to provide an electrolyte applied to a high-energy-density lithium ion battery, so as to solve the problems that the conventional high-energy-density lithium ion battery is easy to generate gas, and a silicon-carbon negative electrode is easy to expand to damage a negative electrode SEI film, and further improve the cycle performance and the safety performance of the battery.
In order to solve the technical problems, the technical scheme adopted by the invention is as follows.
An electrolyte applied to a high-energy-density lithium ion battery comprises the following components in parts by weight: 70-88 parts of a non-aqueous organic solvent, 10-20 parts of a lithium salt and 2-10 parts of an additive containing 30-70% of SFMD1611 by mass;
the SFMD1611 comprises succinic anhydride, fluorobenzene, methylene methanedisulfonate and vinyl sulfate.
According to the further optimized technical scheme, the non-aqueous organic solvent comprises 60-70 wt% of Ethyl Methyl Carbonate (EMC) and 30-40 wt% of Ethylene Carbonate (EC).
Further optimizing the technical scheme, the lithium salt is lithium hexafluorophosphate (LiPF) with the total concentration of 0.8-1.4M6)。
The technical scheme is further optimized, the additive comprises 30-70 wt% of SFMD1611, 20-50 wt% of fluoroethylene carbonate, 5-15 wt% of lithium difluorophosphate and 10-30 wt% of 1, 3-propane sultone.
The technical scheme is further optimized, and the electrolyte applied to the high-energy-density lithium ion battery comprises the following components in parts by weight: 70-80 parts of a nonaqueous organic solvent, 12-20 parts of a lithium salt and 4-10 parts of an additive containing SFMD 1611;
the SFMD1611 comprises succinic anhydride, fluorobenzene, methylene methanedisulfonate and vinyl sulfate.
The invention also provides a preparation method of the electrolyte applied to the high-energy-density lithium ion battery, which comprises the following steps:
s1: mixing ethylene carbonate and methyl ethyl carbonate to prepare a non-aqueous organic solvent;
s2: preparing a common electrolyte from a nonaqueous organic solvent and a lithium salt;
s3: mixing SFMD1611, fluoroethylene carbonate, lithium difluorophosphate and 1, 3-propane sultone to prepare an additive;
s4: uniformly mixing the additive prepared in the step S3 with the electrolyte prepared in the step S2 to obtain the electrolyte applied to the high-energy-density lithium ion battery;
the above processes are all carried out in a glove box with the moisture content less than or equal to 10 ppm.
Further optimizing the technical scheme, the ethylene carbonate and the methyl ethyl carbonate in the step S1 are both subjected to rectification dehydration purification treatment.
Further optimizing the technical scheme, the preparation method of the SFMD1611 in the additive in the step S3 is as follows:
dissolving 1 part of succinic anhydride in 6 parts of fluorobenzene, uniformly mixing, sealing, and standing for 4 hours in a refrigerator at the temperature of below 0 ℃; then 1 part of methylene methanedisulfonate and 1 part of vinyl sulfate are added and mixed evenly, the temperature in the mixing process is less than 15 ℃, and finally the SFMD1611 is prepared.
Due to the adoption of the technical scheme, the technical progress of the invention is as follows.
According to the electrolyte applied to the high-energy-density lithium ion battery, the SFMD611 is added to effectively inhibit the precipitation of nickel ions and the generation of gas in the high-nickel ternary material, and an elastic SEI film is formed, so that the SEI film is not easily damaged due to the expansion of a silicon-carbon negative electrode, and the cycle performance, the high-temperature performance and the safety performance of the lithium ion battery with the high-nickel ternary material and the silicon-carbon negative electrode are improved.
Detailed Description
An electrolyte applied to a high-energy-density lithium ion battery comprises the following components in parts by weight: 70-88 parts of a non-aqueous organic solvent, 10-20 parts of a lithium salt and 2-10 parts of an additive containing SFMD 1611.
The additive comprises 30-70 wt% of SFMD1611, 20-50 wt% of fluoroethylene carbonate, 5-15 wt% of lithium difluorophosphate, 10-30 wt% of 1, 3-propane sultone and 100 wt% of additive.
The SFMD1611 in the additive is formed by mixing succinic anhydride, fluorobenzene, methylene methanedisulfonate and vinyl sulfate in a certain order. The preparation method of the SFMD1611 comprises the following steps: dissolving 1 part of succinic anhydride in 6 parts of fluorobenzene, uniformly mixing, sealing, standing in a refrigerator below 0 ℃ for 4 hours, adding 1 part of methylene methanedisulfonate and 1 part of vinyl sulfate, and controlling the temperature to be lower than 15 ℃ in the process.
The non-aqueous organic solvent is selected from a mixture of at least two of: ethylene Carbonate (EC), Propylene Carbonate (PC), Ethyl Methyl Carbonate (EMC), dimethyl carbonate (DMC), diethyl carbonate (DEC). The non-aqueous solvent is a mixture of Ethyl Methyl Carbonate (EMC) and Ethylene Carbonate (EC), the Ethylene Carbonate (EC) accounts for 60-70 wt%, the Ethyl Methyl Carbonate (EMC) accounts for 30-40 wt%, and the total mass of the Ethylene Carbonate (EC) and the Ethyl Methyl Carbonate (EMC) is equal to 100 wt% of the non-aqueous organic solvent.
The lithium salt in the high-energy density lithium ion battery electrolyte is lithium hexafluorophosphate, and the total concentration of the lithium hexafluorophosphate is 0.8-1.4M.
The preparation method of the electrolyte applied to the high-energy-density lithium ion battery comprises the following specific steps:
s1: rectifying and dehydrating the ethylene carbonate and the methyl ethyl carbonate for purification, and uniformly mixing 60-70 wt% of the ethylene carbonate and 30-40 wt% of the methyl ethyl carbonate in a glove box with the water content less than or equal to 10ppm to obtain the non-aqueous organic solvent.
S2: in a glove box with the water content less than or equal to 10ppm, 70-88 parts of nonaqueous organic solvent is put into a closed container with the temperature of-10 ℃, is taken out after being placed for 4 hours and is uniformly mixed with 10-20 parts of lithium salt, and the common electrolyte is prepared.
S3: dissolving 1 part of succinic anhydride in 6 parts of fluorobenzene, uniformly mixing, sealing, and standing for 4 hours in a refrigerator at the temperature of below 0 ℃; then adding 1 part of methylene methanedisulfonate and 1 part of vinyl sulfate, and uniformly mixing, wherein the temperature in the mixing process is less than 15 ℃, so as to prepare SFMD 1611; the additive is prepared by mixing 3-7 parts of SFMD1611, 2-5 parts of fluoroethylene carbonate, 0.5-1.5 parts of lithium difluorophosphate and 1-3 parts of 1, 3-propane sultone.
S4: and (3) uniformly mixing 2-10 parts of additive and the electrolyte prepared by S2 in a glove box with the water content less than or equal to 10ppm to obtain the electrolyte applied to the high-energy-density lithium ion battery.
The present invention will be described in further detail with reference to specific examples.
Example 1
In a glove box with the water content less than or equal to 10ppm, 30g of ethylene carbonate and 70g of methyl ethyl carbonate are refined and purified to obtain the non-aqueous organic solvent.
And (3) taking 70g of the nonaqueous organic solvent, putting the nonaqueous organic solvent into a closed container, standing the nonaqueous organic solvent for 4 hours at the temperature of minus 10 ℃, taking the nonaqueous organic solvent out, adding 20g of lithium hexafluorophosphate, and uniformly stirring to obtain the common electrolyte.
Dissolving 1 part of succinic anhydride in 6 parts of fluorobenzene, uniformly mixing, sealing, standing for 4 hours in a refrigerator at the temperature of below 0 ℃, adding 1 part of methylene methanedisulfonate and 1 part of vinyl sulfate, controlling the temperature to be not higher than 15 ℃ in the process, and uniformly stirring to obtain the SFDM 1611.
Taking 16117 g of SFDM, 0.5g of fluoroethylene carbonate, 1g of lithium difluorophosphate and 1.5g of 1, 3-propane sultone, and stirring for 30 minutes to obtain the additive.
And adding the additive into the prepared common electrolyte and uniformly mixing to obtain the electrolyte applied to the high-energy-density lithium ion battery.
Example 2
In a glove box with the water content less than or equal to 10ppm, 30g of ethylene carbonate and 70g of methyl ethyl carbonate are refined and purified to obtain the non-aqueous organic solvent.
And (3) putting 88g of the mixed solvent into a closed container, standing for 4h at-10 ℃, taking out, adding 10g of lithium hexafluorophosphate, and uniformly stirring to obtain the common electrolyte.
Dissolving 1 part of succinic anhydride in 6 parts of fluorobenzene, uniformly mixing, sealing, standing for 4 hours in a refrigerator at the temperature of below 0 ℃, adding 1 part of methylene methanedisulfonate and 1 part of vinyl sulfate, controlling the temperature to be not higher than 15 ℃ in the process, and uniformly stirring to obtain the SFDM 1611.
An additive was obtained by stirring 16110.6 g of SFDM, 0.4g of fluoroethylene carbonate, 0.8g of lithium difluorophosphate and 0.2g of 1,3 propane sultone for 30 minutes.
And adding the additive into the prepared common electrolyte and uniformly mixing to obtain the electrolyte applied to the high-energy-density lithium ion battery.
Example 3
In a glove box with the water content less than or equal to 10ppm, 30g of ethylene carbonate and 70g of methyl ethyl carbonate are refined and purified to obtain the non-aqueous organic solvent.
And (3) putting 74g of the mixed solvent into a closed container, standing for 4h at the temperature of minus 10 ℃, taking out, adding 18g of lithium hexafluorophosphate, and uniformly stirring to obtain the common electrolyte.
Dissolving 1 part of succinic anhydride in 6 parts of fluorobenzene, uniformly mixing, sealing, standing for 4 hours in a refrigerator at the temperature of below 0 ℃, adding 1 part of methylene methanedisulfonate and 1 part of vinyl sulfate, controlling the temperature to be not higher than 15 ℃ in the process, and uniformly stirring to obtain the SFDM 1611.
An additive was obtained by stirring 16110.8 g of SFDM, 4g of fluoroethylene carbonate, 1.2g of lithium difluorophosphate and 2g of 1, 3-propane sultone for 30 minutes.
And adding the additive into the prepared common electrolyte and uniformly mixing to obtain the electrolyte applied to the high-energy-density lithium ion battery.
Example 4
In a glove box with the water content less than or equal to 10ppm, 30g of ethylene carbonate and 70g of methyl ethyl carbonate are refined and purified to obtain the non-aqueous organic solvent.
And (3) putting 84g of the mixed solvent into a closed container, standing for 4h at-10 ℃, taking out, adding 12g of lithium hexafluorophosphate, and uniformly stirring to obtain the common electrolyte.
Dissolving 1 part of succinic anhydride in 6 parts of fluorobenzene, uniformly mixing, sealing, standing for 4 hours in a refrigerator at the temperature of below 0 ℃, adding 1 part of methylene methanedisulfonate and 1 part of vinyl sulfate, controlling the temperature to be not higher than 15 ℃ in the process, and uniformly stirring to obtain the SFDM 1611.
Taking SFDM16112.4g, fluoroethylene carbonate 0.6g, lithium difluorophosphate 0.4g and 1,3 propane sultone 0.6g, stirring for 30 minutes to obtain the additive.
And adding the additive into the prepared common electrolyte and uniformly mixing to obtain the electrolyte applied to the high-energy-density lithium ion battery.
Comparative example 1
In a glove box with the water content less than or equal to 10ppm, 30g of ethylene carbonate and 70g of methyl ethyl carbonate are refined and purified to obtain a mixed solvent, 81g of the mixed solvent is taken out, put into a closed container and kept stand for 4 hours at the temperature of minus 10 ℃, and then taken out. Then, 13g of lithium hexafluorophosphate was added thereto, the mixture was stirred uniformly, 3g of fluoroethylene carbonate, 1g of lithium difluorophosphate and 2g of 1,3 propane sultone were added thereto, and the mixture was stirred for 30 minutes to obtain an electrolyte.
The electrolytes of the high energy density lithium ion batteries manufactured in examples 1 to 4 and the common electrolyte manufactured in comparative example 1 were prepared into batteries, and then normal temperature and low temperature cycle performance and high temperature storage performance tests were performed, respectively, and the test results are shown in table 1.
Table 1:
examples 1-4 were compared to comparative example 1: examples 1-4 differ from comparative example 1 in that comparative example 1 does not contain SFMD1611 and the remaining components are the same. In combination with the test data in table 1, the battery prepared by adding the electrolyte of SFMD1611 has obviously improved normal temperature and low temperature cycle performance and high temperature storage performance, in the embodiment, the capacity retention rate of the lithium ion battery after 1000 cycles at 25 ℃ is up to 92.15%, the capacity retention rate of the lithium ion battery after 500 cycles at 55 ℃ is up to 93.10%, while the capacity retention rate of the lithium ion battery in comparative example 1 after 1000 cycles at 25 ℃ is only 86.47%, the capacity retention rate of the lithium ion battery after 500 cycles at 55 ℃ is only 87.48%, in the embodiment, the capacity retention rate and the capacity recovery rate of the lithium ion battery after 7 days of high temperature storage at 60 ℃ can be up to 96.12% and 99.89%, respectively, and the thickness expansion rate is reduced to 3.9%, while the capacity retention rate and the capacity recovery rate of the lithium ion battery in comparative example 1 after 7 days of high temperature storage at 60 ℃ are 92.59% and 96.78. It can be seen that the addition of SFMD1611 to the electrolyte improves the cycle performance and high temperature performance of the battery.
Through performance tests on the lithium ion battery prepared in the embodiment, the lithium battery prepared by applying the electrolyte disclosed by the invention has the characteristics of stable normal-temperature and low-temperature cycle performance and stable high-temperature storage performance, so that the electrolyte disclosed by the invention is applied to the lithium ion battery, and the charge-discharge cycle performance, the high-temperature performance and the safety performance of the lithium ion battery are greatly improved.