Lithium iron phosphate battery, electrolyte and preparation method of lithium iron phosphate battery
阅读说明：本技术 一种磷酸铁锂电池、电解液及磷酸铁锂电池的制备方法 (Lithium iron phosphate battery, electrolyte and preparation method of lithium iron phosphate battery ) 是由 鞠以彬 郭建 董宏亮 于 2019-09-16 设计创作，主要内容包括：本发明公开了一种磷酸铁锂电池、电解液及磷酸铁锂电池的制备方法,属于锂电池技术领域。本发明通过采用含有碳酸乙烯脂、碳酸甲乙酯、碳酸二甲酯、碳酸丙烯酯、六氟磷酸锂、丙磺酸内酯、碳酸亚乙烯酯和二氟草酸硼酸锂的低温型电解液作为磷酸铁锂电池的电解液,并对磷酸铁锂电池的正、负极片进行改进,以降低磷酸铁锂电池的内部阻抗,便可使得磷酸铁锂电池在零下40±3℃的环境下也能正常放电,其低温环境下的放电效率较高,从而可以延长磷酸铁锂电池的使用寿命以及可以起到节能的作用。(The invention discloses a lithium iron phosphate battery, an electrolyte and a preparation method of the lithium iron phosphate battery, and belongs to the technical field of lithium batteries. The invention adopts the low-temperature electrolyte containing the ethylene carbonate, the ethyl methyl carbonate, the dimethyl carbonate, the propylene carbonate, the lithium hexafluorophosphate, the propane sultone, the vinylene carbonate and the lithium difluoroborate as the electrolyte of the lithium iron phosphate battery, improves the positive pole piece and the negative pole piece of the lithium iron phosphate battery to reduce the internal impedance of the lithium iron phosphate battery, so that the lithium iron phosphate battery can normally discharge at the temperature of minus 40 +/-3 ℃, has higher discharge efficiency in the low-temperature environment, prolongs the service life of the lithium iron phosphate battery and plays a role in energy conservation.)
1. The electrolyte is characterized by comprising the following components in percentage by mass: 24-35.4% of ethylene carbonate, 20-35% of ethyl methyl carbonate, 15-25% of dimethyl carbonate, 3-7% of propylene carbonate, 10-18% of lithium hexafluorophosphate, 0.5-2% of propane sultone, 1-3% of vinylene carbonate and 0.1-1% of lithium difluoro oxalate borate, wherein the sum of the mass fractions of the components is 100%.
2. the electrolyte of claim 1, wherein the electrolyte comprises the following components in parts by mass: 27.6 to 33.4 percent of ethylene carbonate, 25 to 30 percent of ethyl methyl carbonate, 18 to 22 percent of dimethyl carbonate, 4 to 6 percent of propylene carbonate, 12 to 15 percent of lithium hexafluorophosphate, 0.8 to 1.2 percent of propane sultone, 1.5 to 2.5 percent of vinylene carbonate and 0.3 to 0.7 percent of lithium difluoro oxalato borate, wherein the sum of the mass fractions of the components is 100 percent.
3. The electrolyte of claim 2, wherein the electrolyte comprises the following components in parts by mass: 29% of ethylene carbonate, 28.4% of ethyl methyl carbonate, 20% of dimethyl carbonate, 5.6% of propylene carbonate, 13.5% of lithium hexafluorophosphate, 1% of propane sultone, 2% of vinylene carbonate and 0.5% of lithium difluorooxalato borate.
4. A lithium iron phosphate battery comprising the electrolyte according to any one of claims 1 to 3.
5. A method for preparing a lithium iron phosphate battery according to claim 4, characterized by comprising the following steps:
Weighing the components of ethylene carbonate, ethyl methyl carbonate, dimethyl carbonate, propylene carbonate, lithium hexafluorophosphate, propane sultone, vinylene carbonate and lithium difluoro oxalato borate according to the mass fractions of the components, and mixing the components together to obtain an electrolyte for later use;
weighing the following components in parts by weight: 40-60 parts of lithium iron phosphate, 0.5-4 parts of polyvinylidene fluoride, 0.5-4 parts of a conductive agent and 40-60 parts of N-methylpyrrolidone for later use; sequentially adding the polyvinylidene fluoride, the conductive agent and the lithium iron phosphate into the N-methyl pyrrolidone, and stirring to obtain anode slurry for later use;
Weighing the following components in parts by weight: 20-30 parts of graphite, 0.1-1 part of carboxymethyl cellulose, 0.1-1 part of a conductive agent, 0.5-3 parts of styrene butadiene rubber and 15-45 parts of deionized water for later use; sequentially adding the carboxymethyl cellulose, the conductive agent, the graphite and the styrene butadiene rubber into the deionized water, and stirring to obtain negative electrode slurry for later use;
Coating the anode slurry on an aluminum foil, and sequentially performing rolling, die cutting and baking treatment to obtain an anode plate;
Coating the negative electrode slurry on copper foil, and sequentially performing rolling, die cutting and baking treatment to obtain a negative electrode sheet;
stacking the positive plate, the negative plate and the diaphragm into a battery cell, and sequentially carrying out hot pressing, shaping and baking treatment on the battery cell;
And injecting the electrolyte into the baked battery core, and then sequentially carrying out formation, aging and sealing treatment to obtain the lithium iron phosphate battery.
6. The preparation method of the lithium iron phosphate battery as claimed in claim 5, wherein in the step, the following components are weighed according to parts by weight: 45-55 parts of lithium iron phosphate, 1-3 parts of polyvinylidene fluoride, 1-2 parts of a conductive agent and 42-50 parts of N-methylpyrrolidone for later use; and sequentially adding the polyvinylidene fluoride, the conductive agent and the lithium iron phosphate into the N-methylpyrrolidone, and stirring to obtain the anode slurry.
7. The preparation method of the lithium iron phosphate battery as claimed in claim 5, wherein in the step, the following components are weighed according to parts by weight: 24-28 parts of graphite, 0.4-0.6 part of carboxymethyl cellulose, 0.3-0.5 part of a conductive agent, 1-2 parts of styrene butadiene rubber and 40-45 parts of deionized water for later use; and sequentially adding the carboxymethyl cellulose, the conductive agent, the graphite and the styrene butadiene rubber into the deionized water, and stirring to obtain the cathode slurry.
8. The method for preparing the lithium iron phosphate battery as claimed in claim 5, wherein in the step, the coating amount per unit area of each surface of the aluminum foil is 130-140 g/m 2.
9. the method for preparing the lithium iron phosphate battery as claimed in claim 5, wherein in the step, the coating amount per unit area of each surface of the copper foil is 60-65 g/m 2.
10. the method for preparing the lithium iron phosphate battery according to claim 5, wherein in the step, the temperature of the battery cell baking treatment is 80-90 ℃.
Technical Field
The invention relates to the technical field of lithium batteries, in particular to a lithium iron phosphate battery, electrolyte and a preparation method of the lithium iron phosphate battery.
Background
A lithium iron phosphate battery is a lithium ion battery taking lithium iron phosphate as a positive electrode material.
at present, the traditional lithium iron phosphate battery can only be used at normal temperature. Under the low-temperature condition, electrolyte in the traditional lithium iron phosphate battery is easy to freeze in the battery, the battery cannot normally discharge at minus 10-20 ℃, generally, the discharge efficiency can only reach 60-70%, so that the attenuation of the battery is accelerated, and chemical crystal blocks growing in the battery are easy to cause the problems of instant short circuit, explosion, ignition and the like of the battery in charging and discharging.
Disclosure of Invention
The invention aims to provide a lithium iron phosphate battery, an electrolyte and a preparation method of the lithium iron phosphate battery, so as to solve the problems in the background technology.
In order to achieve the above purpose, the embodiments of the present invention provide the following technical solutions:
an electrolyte comprises the following components in percentage by mass: 24-35.4% of ethylene carbonate, 20-35% of ethyl methyl carbonate, 15-25% of dimethyl carbonate, 3-7% of propylene carbonate, 10-18% of lithium hexafluorophosphate, 0.5-2% of propane sultone, 1-3% of vinylene carbonate and 0.1-1% of lithium difluoro oxalate borate, wherein the sum of the mass fractions of the components is 100%.
According to a preferable scheme adopted by the embodiment of the invention, the electrolyte comprises the following components in parts by mass: 27.6 to 33.4 percent of ethylene carbonate, 25 to 30 percent of ethyl methyl carbonate, 18 to 22 percent of dimethyl carbonate, 4 to 6 percent of propylene carbonate, 12 to 15 percent of lithium hexafluorophosphate, 0.8 to 1.2 percent of propane sultone, 1.5 to 2.5 percent of vinylene carbonate and 0.3 to 0.7 percent of lithium difluoro oxalato borate, wherein the sum of the mass fractions of the components is 100 percent.
According to another preferable scheme adopted by the embodiment of the invention, the electrolyte comprises the following components in parts by mass: 29% of ethylene carbonate, 28.4% of ethyl methyl carbonate, 20% of dimethyl carbonate, 5.6% of propylene carbonate, 13.5% of lithium hexafluorophosphate, 1% of propane sultone, 2% of vinylene carbonate and 0.5% of lithium difluorooxalato borate.
The embodiment of the invention also provides a lithium iron phosphate battery containing the electrolyte.
The embodiment of the invention also provides a preparation method of the lithium iron phosphate battery, which comprises the following steps:
Weighing the components of ethylene carbonate, ethyl methyl carbonate, dimethyl carbonate, propylene carbonate, lithium hexafluorophosphate, propane sultone, vinylene carbonate and lithium difluoro oxalato borate according to the mass fractions of the components, and mixing the components together to obtain an electrolyte for later use;
Weighing the following components in parts by weight: 40-60 parts of lithium iron phosphate, 0.5-4 parts of polyvinylidene fluoride, 0.5-4 parts of a conductive agent and 40-60 parts of N-methylpyrrolidone for later use; sequentially adding the polyvinylidene fluoride, the conductive agent and the lithium iron phosphate into the N-methyl pyrrolidone, and stirring to obtain anode slurry for later use;
Weighing the following components in parts by weight: 20-30 parts of graphite, 0.1-1 part of carboxymethyl cellulose, 0.1-1 part of a conductive agent, 0.5-3 parts of styrene butadiene rubber and 15-45 parts of deionized water for later use; sequentially adding the carboxymethyl cellulose, the conductive agent, the graphite and the styrene butadiene rubber into the deionized water, and stirring to obtain negative electrode slurry for later use;
Coating the anode slurry on an aluminum foil, and sequentially performing rolling, die cutting and baking treatment to obtain an anode plate;
Coating the negative electrode slurry on copper foil, and sequentially performing rolling, die cutting and baking treatment to obtain a negative electrode sheet;
Stacking the positive plate, the negative plate and the diaphragm into a battery cell, and sequentially carrying out hot pressing, shaping and baking treatment on the battery cell;
And injecting the electrolyte into the baked battery core, and then sequentially carrying out formation, aging and sealing treatment to obtain the lithium iron phosphate battery.
According to another preferable scheme adopted by the embodiment of the invention, in the step, the following components are weighed according to parts by weight: 45-55 parts of lithium iron phosphate, 1-3 parts of polyvinylidene fluoride, 1-2 parts of a conductive agent and 42-50 parts of N-methylpyrrolidone for later use; and sequentially adding the polyvinylidene fluoride, the conductive agent and the lithium iron phosphate into the N-methylpyrrolidone, and stirring to obtain the anode slurry.
According to another preferable scheme adopted by the embodiment of the invention, in the step, the following components are weighed according to parts by weight: 24-28 parts of graphite, 0.4-0.6 part of carboxymethyl cellulose, 0.3-0.5 part of a conductive agent, 1-2 parts of styrene butadiene rubber and 40-45 parts of deionized water for later use; and sequentially adding the carboxymethyl cellulose, the conductive agent, the graphite and the styrene butadiene rubber into the deionized water, and stirring to obtain the cathode slurry.
According to another preferable scheme adopted by the embodiment of the invention, in the step, the coating weight of each surface of the aluminum foil is 130-140 g/m 2.
According to another preferable scheme adopted by the embodiment of the invention, in the step, the coating weight per unit area of each surface of the copper foil is 60-65 g/m 2.
According to another preferable scheme adopted by the embodiment of the invention, in the step, the temperature of the battery cell baking treatment is 80-90 ℃.
Compared with the prior art, the embodiment of the invention has the beneficial effects that:
According to the embodiment of the invention, the low-temperature electrolyte containing the vinyl carbonate, the ethyl methyl carbonate, the dimethyl carbonate, the propylene carbonate, the lithium hexafluorophosphate, the propane sultone, the vinylene carbonate and the lithium difluoroborate is adopted as the electrolyte of the lithium iron phosphate battery, and the positive plate and the negative plate of the lithium iron phosphate battery are improved to reduce the internal impedance of the lithium iron phosphate battery, so that the lithium iron phosphate battery can normally discharge at the temperature of minus 40 +/-3 ℃, the discharge efficiency of the lithium iron phosphate battery in the low-temperature environment is higher, the service life of the lithium iron phosphate battery can be prolonged, and the energy-saving effect can be achieved.
Drawings
fig. 1 is a discharge curve diagram of the lithium iron phosphate battery prepared in example 5 in a normal temperature environment.
Fig. 2 is a discharge curve diagram of the lithium iron phosphate battery prepared in example 5 at-40 ℃.
Detailed Description
The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.