Electrolyte material package, electrolyte injection method and secondary battery

Abstract

The invention provides an electrolyte material package, an electrolyte injection method and a secondary battery, and belongs to the technical field of secondary batteries. The electrolyte material comprises a first material package and a second material package, the first material comprises a first non-aqueous organic solvent and a first additive, the first additive is fluoroethylene carbonate, and the second material comprises a lithium salt or sodium salt, a second non-aqueous organic solvent and a second additive. According to the electrolyte material and the electrolyte injection method, the first additive fluoroethylene carbonate in the first material package is introduced into the battery, and heat is absorbed and the temperature of the battery is reduced through the hydrolysis reaction of the first additive fluoroethylene carbonate at high temperature, so that the electrolyte injection efficiency can be effectively improved, and the rate capability and the cycle performance of the battery are improved; besides, the first additive fluoroethylene carbonate can consume moisture in the battery, so that the production efficiency of baking and liquid injection procedures can be improved, and the electrochemical performance and the safety performance of the battery can also be improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of secondary batteries, and particularly relates to an electrolyte material package, an electrolyte injection method, and a secondary battery. Background Art

[0002] Lithium-ion batteries are widely used in fields such as 3C digital products, electric vehicles, and military aerospace due to their advantages such as high working voltage, high energy density, long cycle life, and environmental friendliness. With the popularization and application of intelligent digital products and the widespread use of new energy vehicles, all walks of life have put forward more stringent requirements for the performance of lithium-ion batteries, such as the improvement of battery capacity, the increase of battery cycle life, and the improvement of battery anti-deformation performance. Square aluminum shell lithium-ion batteries are a main type of battery currently used in the field of electric vehicles. The electrolyte content in square aluminum shell lithium-ion batteries has a great influence on the cycle performance and rate performance of the batteries. To a certain extent, the above-mentioned performance of the batteries can be improved by increasing the liquid retention amount during the manufacturing process.

[0003] In current square aluminum shell lithium-ion batteries, in addition to the electrode sheets and separators having an adsorption effect on the electrolyte, the free electrolyte is stored in the voids of the square aluminum shell batteries. However, in order to maximize the energy density of the batteries during battery design, the compaction density of the positive and negative electrodes is designed to be relatively extreme, the electrode sheets absorb liquid slowly, and the internal space margin of the batteries is also small. In the actual production process, after the battery baking process is completed, it directly enters the liquid injection process. The temperature inside the battery is relatively high, and the density of the electrolyte decreases as the temperature rises. The space required to inject a certain weight of electrolyte becomes larger, so that it will overflow after the voids inside the square aluminum shell are filled, and the liquid retention amount of the electrolyte becomes less, that is, the liquid injection efficiency decreases. In addition, the overflowing electrolyte will corrode the equipment, seriously affecting the production efficiency and the cycle life of the equipment, resulting in an increase in production costs. Summary of the Invention

[0004] The present invention aims to solve at least one of the technical problems in the related art to some extent. For this reason, an embodiment of the present invention provides an electrolyte material package, an electrolyte injection method, and a secondary battery. The electrolyte material package and the electrolyte injection method can effectively improve the liquid injection efficiency of the electrolyte. In addition, the amount of electrolyte overflow can be reduced, and the corrosion of the production equipment can be reduced.

[0005] In a first aspect, an embodiment of the present invention provides an electrolyte material package, including a first material package and a second material package. The first material package contains a first non-aqueous organic solvent and a first additive, and the first additive is fluoroethylene carbonate. The second material package contains a lithium salt or a sodium salt, a second non-aqueous organic solvent, and a second additive.

[0006] The advantages and technical effects brought by the electrolyte material package of the embodiment of the present invention are as follows:

[0007] (1) The electrolyte material package in the embodiments of the present invention is divided into a first material package and a second material package. When injecting the electrolyte into the battery subsequently, it can be injected in stages. First, inject the first material package within a period of time before the battery baking process is about to end. Turn off the heating function of the vacuum baking device but continue to evacuate the air, so that at least a part of the first non-polar organic solvent injected into the battery is pumped out, and the first additive fluoroethylene carbonate remains in the battery. The first additive fluoroethylene carbonate can undergo a decomposition reaction with the moisture in the electrode sheet under high-temperature conditions. During the continuous evacuation process, the by-products of the reaction are carried out by the first non-polar organic solvent, without introducing impurities into the battery. After the baking process is completed, turn off the evacuation function of the vacuum baking device, and then perform the liquid injection operation of the second material package.

[0008] (2) The decomposition reaction of the first additive fluoroethylene carbonate with the moisture in the electrode sheet under high-temperature conditions is an endothermic reaction, which can effectively reduce the temperature of the battery internal winding core. As the temperature of the winding core decreases, the density of the second material package will increase, and the space required to accommodate the same amount of electrolyte will be smaller. That is to say, more electrolyte can be retained in the limited space of the battery shell, improving the liquid injection efficiency of the electrolyte. The increase in the electrolyte content in the battery thus improves the rate performance and cycle performance of the battery; in other words, after injecting the same amount of the second material package into the limited space of the battery shell, the overflow amount of the electrolyte decreases, reducing the corrosion of the production equipment; at the same time, the first additive fluoroethylene carbonate in the first material package can consume the moisture inside the battery, which can not only improve the production efficiency of the baking and liquid injection processes, but also improve the electrochemical performance and safety performance of the battery.

[0009] In some embodiments, based on the total mass of the electrolyte material package being 100 wt%, the content of the first additive is 1 - 6 wt%.

[0010] In some embodiments, based on the total mass of the electrolyte material package being 100 wt%, the content of the second additive is 1 - 6 wt%.

[0011] In some embodiments, the second additive is vinylene carbonate.

[0012] In some embodiments, based on the total mass of the electrolyte material package being 100 wt%, the sum of the contents of the first non-aqueous organic solvent and the second non-aqueous organic solvent is 75 - 80 wt%.

[0013] In some embodiments, the mass ratio of the first non-aqueous organic solvent to the second non-aqueous organic solvent is 1:4 - 2:3.

[0014] In some embodiments, the first non-aqueous organic solvent and the second non-aqueous organic solvent independently include a cyclic carbonate solvent and a linear carbonate solvent.

[0015] In some embodiments, the cyclic carbonate solvent includes ethylene carbonate.

[0016] In some embodiments, the linear carbonate solvent includes at least one of dimethyl carbonate, ethyl methyl carbonate, diethyl carbonate, and methyl propyl carbonate.

[0017] In some embodiments, based on the total mass of the electrolyte material package being 100 wt%, the content of the lithium salt or sodium salt is 15 - 20 wt%.

[0018] In a second aspect, an embodiment of the present invention provides an electrolyte injection method, including the following steps: within 20 min to 1 h before the end of the battery baking process, inject the first material package in the electrolyte material package described in the first aspect into the battery, then turn off the heating function of the vacuum baking device, turn off the vacuum pumping function of the vacuum baking device after the baking process ends, and then inject the second material package in the electrolyte material package described in the first aspect into the battery.

[0019] The advantages and technical effects brought by the electrolyte injection method of the embodiment of the present invention are as follows:

[0020] (1) The electrolyte injection method of the embodiment of the present invention is carried out in stages. First, inject the first material package within a period of time before the end of the battery baking process, turn off the heating function of the vacuum baking device but continue to pump vacuum, so that at least a part of the first non-polar organic solvent injected into the battery is pumped out, and the first additive fluoroethylene carbonate remains in the battery. The first additive fluoroethylene carbonate can undergo a decomposition reaction with the moisture in the electrode sheet under high-temperature conditions, and the by-products of the reaction are carried out by the first non-polar organic solvent during the continuous vacuum pumping process, without introducing impurities into the battery. After the baking process ends, turn off the vacuum pumping function of the baking device, and then perform the liquid injection operation of the second material package.

[0021] (2) The decomposition reaction of the first additive, vinyl fluorocarbonate, with the moisture in the electrode sheet under high-temperature conditions is an endothermic reaction, which can effectively reduce the temperature of the battery core. As the temperature of the battery core decreases, the density of the second material package increases, and the space required to accommodate the same amount of electrolyte is smaller. That is to say, more electrolyte can be retained in the limited space of the battery case, improving the electrolyte injection efficiency. The increase in the electrolyte content in the battery thus improves the rate performance and cycle performance of the battery. In other words, when the same amount of the second material package is injected into the limited space of the battery case, the overflow amount of the electrolyte decreases, reducing the corrosion of the production equipment. At the same time, the first additive, vinyl fluorocarbonate, in the first material package can consume the moisture inside the battery, which can not only improve the production efficiency of the baking and injection processes but also improve the electrochemical performance and safety performance of the battery.

[0022] In a third aspect, an embodiment of the present invention provides a secondary battery, including an electrolyte, which is prepared from the electrolyte material package described in the first aspect or by the electrolyte injection method described in the second aspect.

[0023] The advantages and technical effects brought by the secondary battery according to the embodiment of the present invention are as follows:

[0024] Since the electrolyte is prepared from the electrolyte material package described in the first aspect or by the electrolyte injection method described in the second aspect, the electrolyte content of the secondary battery according to the embodiment of the present invention increases, and the rate performance and cycle performance of the battery are relatively high. In addition, the moisture inside the secondary battery according to the embodiment of the present invention decreases, and the electrochemical performance and safety performance of the secondary battery are relatively high. Moreover, the production efficiency of the baking and injection processes of the secondary battery is also relatively high. Description of the Drawings

[0025] Figure 1 Curve of the density of the second material package prepared in Example 1 varying with the battery temperature.

[0026] Figure 2 Curve of the high-rate cycle capacity retention rate of the batteries in Examples 1 to 5 and the control group. Detailed Embodiments

[0027] The embodiments of the present invention will be described in detail below. The examples of the embodiments are shown in the drawings. The embodiments described below with reference to the drawings are exemplary and are intended to explain the present invention and should not be construed as limiting the present invention.

[0028] In a first aspect, an embodiment of the present invention provides an electrolyte material package, which includes a first material package and a second material package. The first material includes a first non-aqueous organic solvent and a first additive, and the first additive is fluoroethylene carbonate (FEC). The second material includes a lithium salt or a sodium salt, a second non-aqueous organic solvent, and a second additive.

[0029] The electrolyte material package in the embodiment of the present invention is divided into a first material package and a second material package. When injecting the electrolyte into the battery subsequently, it can be injected in stages. First, inject the first material package within a period of time before the end of the battery baking process. Turn off the heating function of the vacuum baking device but continue to evacuate the air, so that at least a part of the first non-polar organic solvent injected into the battery is pumped out, and the first additive fluoroethylene carbonate remains in the battery. The first additive fluoroethylene carbonate can undergo a decomposition reaction with the moisture in the electrode sheet under high-temperature conditions. During the continuous evacuation process, the by-products of the reaction are carried out by the first non-polar organic solvent without introducing impurities into the battery. After the baking process is completed, turn off the vacuum pumping function of the vacuum baking device, and then perform the liquid injection operation of the second material package.

[0030] The decomposition reaction of the first additive fluoroethylene carbonate with the moisture in the electrode sheet under high-temperature conditions is an endothermic reaction, which can effectively reduce the temperature of the battery internal winding core. As the temperature of the winding core decreases, the density of the second material package will increase, and the space required to accommodate the same amount of electrolyte will be smaller. That is to say, more electrolyte can be retained in the limited space of the battery shell, improving the electrolyte injection efficiency (injection efficiency = liquid retention amount / injection amount = (injection amount - overflow amount) / injection amount). The increase in the electrolyte content in the battery improves the rate performance and cycle performance of the battery; in other words, after injecting the same amount of the second material package into the limited space of the battery shell, the overflow amount of the electrolyte decreases, reducing the corrosion of the production equipment. At the same time, the first additive fluoroethylene carbonate in the first material package can consume the moisture inside the battery, which can not only improve the production efficiency of the baking and liquid injection processes, but also improve the electrochemical performance and safety performance of the battery.

[0031] In some embodiments, based on the total mass of the electrolyte material package being 100 wt%, the content of the first additive is 1 to 6 wt%, such as 1 wt%, 1.5 wt%, 2 wt%, 2.5 wt%, 3 wt%, 3.5 wt%, 4 wt%, 4.5 wt%, 5 wt%, 5.5 wt%, 6 wt%, etc. When the content of the first additive in the electrolyte material package is too low, it is not conducive to the decomposition reaction with the moisture in the electrode sheet, reducing the temperature of the winding core, and thus improving the injection efficiency of the electrolyte. When the content of the first additive in the electrolyte material package is too high, the above effects will not be significantly improved, but instead, the content of other components will be reduced, which is not conducive to improving the comprehensive effect.

[0032] In some embodiments, based on the total mass of the electrolyte material package being 100 wt%, the content of the second additive is 1 - 6 wt%, such as 1 wt%, 1.5 wt%, 2 wt%, 2.5 wt%, 3 wt%, 3.5 wt%, 4 wt%, 4.5 wt%, 5 wt%, 5.5 wt%, 6 wt%, etc. The second additive is a film-forming additive, which is used to improve the high-temperature cycling performance of the battery. When the content of the second additive in the electrolyte material package is too low, it is not conducive to improving the high-temperature cycling performance of the battery. When the content of the second additive in the electrolyte material package is too high, the above effects will not be significantly improved, but instead the content of other components will be reduced, which is not conducive to improving the comprehensive effect.

[0033] The type of the second additive in the electrolyte material package of the embodiments of the present invention can be adjusted according to the type of battery to be applied. In some embodiments, when the battery to be applied is a lithium-ion battery, the second additive can be vinylene carbonate (VC), because vinylene carbonate has a lower film-forming potential and is easier to form a SEI film, which is conducive to improving the high-temperature cycling performance of the battery.

[0034] In some embodiments, based on the total mass of the electrolyte material package being 100 wt%, the content of the first non-aqueous organic solvent is 15 - 32 wt%, such as 15 wt%, 18 wt%, 20 wt%, 22 wt%, 24 wt%, 26 wt%, 28 wt%, 30 wt%, 32 wt%, etc. When the content of the first non-aqueous organic solvent in the electrolyte material package is too low, it is not conducive to the uniform dispersion of the first additive in the battery, is not conducive to the decomposition reaction with the moisture in the electrode sheet, and reduces the core temperature, thereby improving the filling efficiency of the electrolyte. When the content of the first non-aqueous organic solvent in the electrolyte material package is too high, the content of the second non-aqueous organic solvent may be too low, and the concentration of the finally formed electrolyte may be too high, which is not conducive to improving the battery charging efficiency and cycle life.

[0035] In some embodiments, based on the total mass of the electrolyte material package being 100 wt%, the content of the second non-aqueous organic solvent is 45 - 64 wt%, such as 45 wt%, 48 wt%, 50 wt%, 52 wt%, 55 wt%, 58 wt%, 60 wt%, 62 wt%, 64 wt%, etc. When the content of the second non-aqueous organic solvent in the electrolyte material package is too low, the concentration of the finally formed electrolyte may be too high, which is not conducive to improving the charging efficiency and battery cycle life. When the content of the second non-aqueous organic solvent in the electrolyte material package is too high, the content of the first non-aqueous organic solvent may be too low, which is not conducive to the uniform dispersion of the first additive in the battery, is not conducive to the decomposition reaction with the moisture in the electrode sheet, and reduces the core temperature, thereby improving the filling efficiency of the electrolyte.

[0036] In some embodiments, based on the total mass of the electrolyte material package being 100 wt%, the sum of the contents of the first non-aqueous organic solvent and the second non-aqueous organic solvent is 75-80 wt%, such as 75 wt%, 76 wt%, 77 wt%, 78 wt%, 79 wt%, 80 wt%, etc. In some embodiments, the mass ratio of the first non-aqueous organic solvent to the second non-aqueous organic solvent is 1:4-2:3, such as 1:4, 1:3, 3:7, 7:13, 2:3, etc. When the contents of the first non-aqueous organic solvent and the second non-aqueous organic solvent in the electrolyte material package and the mass ratio of the first non-aqueous organic solvent to the second non-aqueous organic solvent are within the above ranges, it can not only ensure the uniform dispersion of the first additive by the first non-aqueous organic solvent, facilitate the decomposition reaction with the moisture in the electrode sheet, reduce the temperature of the wound core, thereby improving the injection efficiency of the electrolyte, but also ensure that the finally formed electrolyte has a suitable concentration, thereby improving the battery charging efficiency and cycle life.

[0037] In some embodiments, the first non-aqueous organic solvent includes a cyclic carbonate solvent and a linear carbonate solvent. Among them, the cyclic carbonate solvent may include ethylene carbonate. The linear carbonate solvent may include at least one of dimethyl carbonate, ethyl methyl carbonate, diethyl carbonate, and methyl propyl carbonate.

[0038] In some embodiments, the second non-aqueous organic solvent includes a cyclic carbonate solvent and a linear carbonate solvent. Among them, the cyclic carbonate solvent may include ethylene carbonate. The linear carbonate solvent may include at least one of dimethyl carbonate, ethyl methyl carbonate, diethyl carbonate, and methyl propyl carbonate.

[0039] In some embodiments, the specific types of the first non-aqueous organic solvent and the second non-aqueous organic solvent are the same.

[0040] In some embodiments, based on the total mass of the electrolyte material package being 100 wt%, the content of the lithium salt or sodium salt is 15-20 wt%, such as 15 wt%, 16 wt%, 17 wt%, 18 wt%, 19 wt%, 20 wt%, etc. When the content of the lithium salt or sodium salt in the electrolyte material package is too low, it is not conducive to improving the battery energy density and cycle life. When the content of the lithium salt or sodium salt in the electrolyte material package is too high, it will increase the viscosity of the electrolyte and reduce the ionic conductivity, thereby affecting the charge and discharge efficiency and cycle life of the battery.

[0041] When the applied secondary battery is a lithium-ion battery, a lithium salt is selected. In some embodiments, the lithium salt is selected from at least one of lithium hexafluorophosphate (LiPF6), lithium tetrafluoroborate (LiBF4), lithium bis(oxalato)borate (LiBOB), lithium difluoro(oxalato)borate (LiDFOB), lithium trifluoromethanesulfonate (LiSO3CF3), lithium perchlorate (LiClO4), lithium hexafluoroarsenate (LiAsF6), and lithium bis(trifluoromethylsulfonyl)imide (Li(CF3SO2)2N).

[0042] When the applied secondary battery is a sodium-ion battery, a sodium salt is selected. In some embodiments, the sodium salt includes at least one of sodium hexafluorophosphate, sodium difluoro(oxalato)borate, sodium tetrafluoroborate, sodium bis(oxalato)borate, sodium perchlorate, sodium hexafluoroarsenate, sodium bis(fluorosulfonyl)imide, sodium trifluoromethanesulfonate, and sodium bis(trifluoromethylsulfonyl)imide.

[0043] In a second aspect, an embodiment of the present invention provides an electrolyte injection method, including the following steps: within 20 min to 1 h before the end of the battery baking process, inject the first material package in the electrolyte material package described in the first aspect into the battery, then turn off the heating function of the vacuum baking device, turn off the vacuum pumping function of the vacuum baking device after the baking process ends, and then inject the second material package in the electrolyte material package described in the first aspect into the battery.

[0044] The electrolyte injection method of the embodiment of the present invention is carried out in stages. First, inject the first material package within a period of time before the end of the battery baking process, turn off the heating function of the vacuum baking device but continue to pump vacuum, so that at least a part of the first non-polar organic solvent injected into the battery is pumped out, and the first additive fluoroethylene carbonate remains in the battery. The first additive fluoroethylene carbonate can undergo a decomposition reaction with the moisture in the electrode sheet under high-temperature conditions. During the continuous vacuum pumping process, the by-products of the reaction are carried out by the first non-polar organic solvent without introducing impurities into the battery. After the baking process ends, turn off the vacuum pumping function of the baking device, and then carry out the liquid injection operation of the second material package.

[0045] Inject the first material package within a certain period of time before the battery baking process is about to end, turn off the heating function of the vacuum baking device, and subsequently use the remaining heat to cause the first additive, fluoroethylene carbonate, to decompose with the moisture in the electrode sheet. This decomposition reaction is an endothermic reaction, and the purpose is to quickly lower the battery temperature. As the temperature of the wound core decreases, the density of the second material package will increase, and the space required to accommodate the same amount of electrolyte will be smaller. That is to say, more electrolyte can be retained in the limited space of the battery case, improving the electrolyte injection efficiency. The increase in the electrolyte content in the battery thus improves the rate performance and cycle performance of the battery; in other words, after injecting the same amount of the second material package into the limited space of the battery case, the overflow amount of the electrolyte decreases, reducing the corrosion of the production equipment. At the same time, the first additive, fluoroethylene carbonate, in the first material package can consume the moisture inside the battery, which can not only improve the production efficiency of the baking and injection processes but also improve the electrochemical performance and safety performance of the battery.

[0046] It should be understood that the purpose of the baking process is to remove the moisture in the electrode sheet, but the crystal water in the electrode sheet cannot be removed by baking. However, the first additive, fluoroethylene carbonate, added in the embodiments of the present invention can decompose with the crystal water in the electrode sheet under high-temperature conditions to remove it. For the electrolyte injection method of the embodiments of the present invention, it is selected to inject the first material package in the electrolyte material package described in the first aspect into the battery within 20 min to 1 h before the end of the battery baking process (such as 20 min, 30 min, 40 min, 50 min, 1 h, etc.), rather than injecting it after the baking process ends and the temperature drops. On the one hand, each process of the production line has time requirements, and doing so can improve the production efficiency. On the other hand, at this time, the battery temperature is relatively high, which can promote the hydrolysis reaction of the first additive, fluoroethylene carbonate, to remove the crystal water in the electrode sheet.

[0047] Thirdly, the embodiments of the present invention provide a secondary battery, including an electrolyte, which is prepared from the electrolyte material package described in the first aspect or by the electrolyte injection method described in the second aspect.

[0048] Since the electrolyte is prepared using the electrolyte material package described in the first aspect or by the electrolyte injection method described in the second aspect, the electrolyte content of the secondary battery in the embodiments of the present invention increases, and the rate performance and cycle performance of the battery are relatively high; in addition, the moisture inside the secondary battery in the embodiments of the present invention decreases, and the electrochemical performance and safety performance of the secondary battery are relatively high; furthermore, the production efficiency of the baking and injection processes of the secondary battery is also relatively high.

[0049] In some embodiments, the concentration of lithium salt or sodium salt in the electrolyte is 0.8 - 1.3 mol / L, such as 0.8 mol / L, 0.9 mol / L, 1 mol / L, 1.1 mol / L, 1.2 mol / L, 1.3 mol / L, etc. When the content of lithium salt or sodium salt in the electrolyte is too low, it is not conducive to improving the energy density and cycle life of the battery. When the content of lithium salt or sodium salt in the electrolyte is too high, it will increase the viscosity of the electrolyte and reduce the ionic conductivity, thereby affecting the charge and discharge efficiency and cycle life of the battery.

[0050] The present invention will be described in detail below with reference to embodiments and drawings.

[0051] Example 1

[0052] (1) Preparation of electrolyte

[0053] The cyclic carbonate solvent ethylene carbonate (EC), the linear carbonate solvents ethyl methyl carbonate (EMC) and diethyl carbonate (DEC) are mixed in a mass ratio of EC:EMC:DEC = 3:5:2, and are purified and dewatered using molecular sieves, calcium hydride, and lithium hydride to obtain a mixed solvent; 20 wt% of the mixed solvent is taken as the first non-polar organic solvent, and the first additive fluoroethylene carbonate (FEC) is added thereto, and the amount of FEC is 1 wt% of the total mass of the electrolyte material package, and it is stirred evenly to obtain the first material package. The remaining 80 wt% of the mixed solvent is used as the second non-polar organic solvent, and the lithium salt LiPF6 is added to the second non-polar organic solvent, and the amount of the lithium salt is 18 wt% of the total mass of the electrolyte material package. Then, the second additive vinylene carbonate (VC) is dissolved therein, and the amount of VC is 5 wt% of the total mass of the electrolyte material package, and it is stirred evenly to obtain the second material package. The first material package and the second material package are stored separately for standby, and the two together constitute the electrolyte material package. The sum of the amounts of the first non-polar organic solvent and the second non-polar organic solvent is 76 wt% of the total mass of the electrolyte material package.

[0054] (2) Assembly of lithium-ion battery

[0055] S1. Preparation of positive electrode sheet: Weigh 95 wt% of lithium iron phosphate, 2 wt% of the positive electrode binder polyvinylidene fluoride, and 3 wt% of the positive electrode conductive agent conductive carbon black by mass. First, polyvinylidene fluoride is added to the N-methylpyrrolidone solvent (solid content 8 wt%) and placed in a double planetary mixer, and stirred at a speed of 2000 m / s for 3.5 h to make a glue solution. Then, conductive carbon black is added to the above glue solution, and stirred at a speed of 4000 m / s for 1.5 h until it is uniform. Then, lithium iron phosphate is added to the above slurry, and stirred at a speed of 4000 m / s for 2.5 h until it is uniform; finally, the slurry is coated on the current collector Al foil (coating thickness 200 μm), and dried at a temperature of 100 °C to prepare a positive electrode sheet, which is roll-pressed and slit to obtain the positive electrode sheet.

[0056] S2. Preparation of the negative electrode sheet: Weigh 96 wt% of graphite negative electrode material, 1.2 wt% of sodium carboxymethyl cellulose as the negative electrode binder, 1.8 wt% of styrene-butadiene rubber as the negative electrode binder, and 1 wt% of conductive carbon black as the negative electrode conductive agent by mass. First, add sodium carboxymethyl cellulose into deionized water (with a solid content of 6 wt%) and put it into a double planetary mixer. Stir at a speed of 2000 m / s for 3 h to make a glue solution. Then, add conductive carbon black and graphite into the above glue solution, stir at a speed of 4000 m / s for 2 h until it is uniform. Next, add styrene-butadiene rubber into the above slurry, stir at a speed of 800 m / s for 0.8 h until it is uniform. Finally, coat the slurry (coating thickness: 150 μm) on the current collector Cu foil, dry it at 80 °C to prepare the negative electrode sheet. After rolling and slitting, the negative electrode sheet is obtained.

[0057] S3. Preparation of the battery cell: Vacuum bake the positive electrode sheet and the negative electrode sheet, and then arrange the positive electrode sheet, the separator (PE porous polymer film), and the negative electrode sheet in sequence, with the separator in the middle of the positive electrode sheet and the negative electrode sheet to play a role in isolation. After winding, the battery cell is made and encapsulated in a square aluminum shell.

[0058] S4. Baking and liquid injection: Put the battery cell into a vacuum drying oven at a temperature of 100 ± 5 °C and a vacuum degree of -0.095 to 0.10 Mpa. Replace the atmosphere in the vacuum drying oven with nitrogen every 1 - 2 h, and set the baking time to 24 h. Inject the first material package into the battery 30 min before the end of baking. Close the temperature of the vacuum drying oven but do not turn off the vacuum, so that the first non-polar organic solvent injected into the battery is pumped out until the baking process ends. Then, perform the liquid injection operation of the second material package. The concentration of the lithium salt in the finally obtained electrolyte is 1.2 mol / L.

[0059] S5. Preparation of the battery: Then, after forming, aging, and grading the battery cell obtained above, the preparation of the lithium-ion battery is completed.

[0060] Example 2

[0061] The cyclic carbonate solvent ethylene carbonate (EC), the linear carbonate solvents ethyl methyl carbonate (EMC) and diethyl carbonate (DEC) are mixed at a mass ratio of EC:EMC:DEC = 3:5:2, and purified and dehydrated using molecular sieve, calcium hydride, and lithium hydride to obtain a mixed solvent; 20 wt% of the mixed solvent is taken as the first non-polar organic solvent, and the first additive fluoroethylene carbonate (FEC) is added thereto, and the dosage of FEC is 2 wt% of the total mass of the electrolyte material package, and it is stirred evenly to obtain the first material package. The remaining 80 wt% of the mixed solvent is used as the second non-polar organic solvent, and the lithium salt LiPF6 is added to the second non-polar organic solvent, and the dosage of the lithium salt is 18 wt% of the total mass of the electrolyte material package. Then, the second additive vinylene carbonate (VC) is dissolved therein, and the dosage of VC is 4 wt% of the total mass of the electrolyte material package, and it is stirred evenly to obtain the second electrolyte material package. The first material package and the second material package are stored separately for standby, and the two together constitute the electrolyte material package. The sum of the dosages of the first non-polar organic solvent and the second non-polar organic solvent is 76 wt% of the total mass of the electrolyte material package.

[0062] The method for assembling the lithium-ion battery is the same as that in Example 1.

[0063] Example 3

[0064] The cyclic carbonate solvent ethylene carbonate (EC), the linear carbonate solvents ethyl methyl carbonate (EMC) and diethyl carbonate (DEC) are mixed at a mass ratio of EC:EMC:DEC = 3:5:2, and purified and dehydrated using molecular sieve, calcium hydride, and lithium hydride to obtain a mixed solvent; 20 wt% of the mixed solvent is taken as the first non-polar organic solvent, and the first additive fluoroethylene carbonate (FEC) is added thereto, and the dosage of FEC is 3 wt% of the total mass of the electrolyte material package, and it is stirred evenly to obtain the first material package. The remaining 80 wt% of the mixed solvent is used as the second non-polar organic solvent, and the lithium salt LiPF6 is added to the second non-polar organic solvent, and the dosage of the lithium salt is 18 wt% of the total mass of the electrolyte material package. Then, the second additive vinylene carbonate (VC) is dissolved therein, and the dosage of VC is 3 wt% of the total mass of the electrolyte material package, and it is stirred evenly to obtain the second electrolyte material package. The first material package and the second material package are stored separately for standby, and the two together constitute the electrolyte material package. The sum of the dosages of the first non-polar organic solvent and the second non-polar organic solvent is 76 wt% of the total mass of the electrolyte material package.

[0065] The method for assembling the lithium-ion battery is the same as that in Example 1.

[0066] Example 4

[0067] The cyclic carbonate solvent ethylene carbonate (EC), the linear carbonate solvents ethyl methyl carbonate (EMC) and diethyl carbonate (DEC) are mixed at a mass ratio of EC:EMC:DEC = 3:5:2, and purified and decontaminated, and dehydrated using molecular sieves, calcium hydride, and lithium hydride to obtain a mixed solvent; 20 wt% of the mixed solvent is taken as the first non-polar organic solvent, and the first additive fluoroethylene carbonate (FEC) is added thereto. The amount of FEC is 4 wt% of the total mass of the electrolyte material package, and it is stirred evenly to obtain the first material package. The remaining 80 wt% of the mixed solvent is used as the second non-polar organic solvent. Lithium salt LiPF6 is added to the second non-polar organic solvent. The amount of the lithium salt is 18 wt% of the total mass of the electrolyte material package. Then, the second additive vinylene carbonate (VC) is dissolved therein. The amount of VC is 2 wt% of the total mass of the electrolyte material package, and it is stirred evenly to obtain the second electrolyte material package. The first material package and the second material package are stored independently for standby, and the two together constitute the electrolyte material package. The sum of the amounts of the first non-polar organic solvent and the second non-polar organic solvent is 76 wt% of the total mass of the electrolyte material package.

[0068] The method of assembling the lithium-ion battery is the same as that in Example 1.

[0069] Example 5

[0070] The cyclic carbonate solvent ethylene carbonate (EC), the linear carbonate solvents ethyl methyl carbonate (EMC) and diethyl carbonate (DEC) are mixed at a mass ratio of EC:EMC:DEC = 3:5:2, and purified and decontaminated, and dehydrated using molecular sieves, calcium hydride, and lithium hydride to obtain a mixed solvent; 20 wt% of the mixed solvent is taken as the first non-polar organic solvent, and the first additive fluoroethylene carbonate (FEC) is added thereto. The amount of FEC is 5 wt% of the total mass of the electrolyte material package, and it is stirred evenly to obtain the first material package. The remaining 80 wt% of the mixed solvent is used as the second non-polar organic solvent. Lithium salt LiPF6 is added to the second non-polar organic solvent. The amount of the lithium salt is 18 wt% of the total mass of the electrolyte material package. Then, the second additive vinylene carbonate (VC) is dissolved therein. The amount of VC is 1 wt% of the total mass of the electrolyte material package, and it is stirred evenly to obtain the second electrolyte material package. The first material package and the second material package are stored independently for standby, and the two together constitute the electrolyte material package. The sum of the amounts of the first non-polar organic solvent and the second non-polar organic solvent is 76 wt% of the total mass of the electrolyte material package.

[0071] The method of assembling the lithium-ion battery is the same as that in Example 1.

[0072] Control group

[0073] The cyclic carbonate solvent ethylene carbonate (EC), the linear carbonate solvents ethyl methyl carbonate (EMC) and diethyl carbonate (DEC) were mixed at a mass ratio of EC:EMC:DEC = 3:5:2, and purified and dehydrated using molecular sieves, calcium hydride, and lithium hydride to obtain a mixed solvent; lithium salt LiPF6 was added to the mixed solvent, and the amount of the lithium salt was 18 wt% of the total mass of the electrolyte. Then, vinylene carbonate (VC) was dissolved therein, and the amount of VC was 6 wt% of the total mass of the electrolyte, and the mixture was stirred evenly to obtain an electrolyte. The amount of the mixed solvent was 76 wt% of the total mass of the electrolyte, and the concentration of the lithium salt in the electrolyte was 1.2 mol / L.

[0074] In the method for assembling a lithium-ion battery, steps S1 to S3 are the same as those in Example 1.

[0075] S4. Baking and liquid injection: The battery cell was placed in a vacuum drying oven at a temperature of 100 ± 5 °C and a vacuum degree of -0.095 to 0.10 Mpa. The atmosphere in the vacuum oven was replaced with nitrogen every 1 to 2 hours, and the baking time was set to 48 hours. After the baking process was completed, the electrolyte injection operation was carried out.

[0076] S5. Preparation of the battery: Then, the battery cell obtained above was formed, aged, and capacity-divided to complete the preparation of the lithium-ion battery.

[0077] Testing:

[0078] (1) Comparison of electrolyte density

[0079] The density of the electrolyte was detected using a portable densitometer of model YP-DS, and the density of the second material package prepared in Example 1 was tested.

[0080] It can be seen from Figure 1 that the density of the electrolyte decreases with the increase of temperature.

[0081] (2) Comparison of the baking time and the residual moisture content on the electrode sheet of batteries in different groups, and the results are shown in Table 1.

[0082] Table 1. Comparison of the baking time and the residual moisture content on the electrode sheet of batteries in different groups

[0083] Group Baking time (h) Residual moisture content of the electrode sheet (PPM) Example 1 24 235 Example 2 24 210 Example 3 24 188 Example 4 24 145 Example 5 24 113 Control group 48 290

[0084] It can be seen from Table 1 that Examples 1-5 with the addition of the first additive can effectively shorten the baking time and reduce the residual moisture content on the electrode sheet, thereby improving the baking efficiency. While the control group without using the first additive has a long baking time and a high residual moisture content on the electrode sheet, and the baking efficiency is low.

[0085] (3) Comparison of the electrolyte overflow situation of batteries in different groups, and the results are shown in Table 2.

[0086] Table 2. Comparison of battery liquid injection and overflow in different groups

[0087] Group Liquid injection volume (g) Overflow volume (g) Example 1 520 2 Example 2 520 8 Example 3 520 0 Example 4 520 0 Example 5 520 0 Control group 520 15

[0088] As can be seen from the results of the examples and the control group in Table 2, when the liquid injection volume is constant, the overflow volume of the batteries in the examples of the present invention is significantly reduced. As can be seen from the results of Examples 1-5 in Table 2, when the liquid injection volume is constant, the battery overflow volume decreases with the increase of the content of the first additive in the electrolyte material package.

[0089] (4) High-rate normal temperature cycling

[0090] For the detection of the high-rate cycling capacity retention rate, the charging cut-off voltage is 3.65V and the discharging cut-off voltage is 2.0V. At 25°C, the battery to be tested is first charged at 0.5C and discharged at 1C to measure the 1C discharging capacity C1; then the battery to be tested is charged at 2C and discharged at 2C for 100 cycles at 25°C, and the discharging capacity of the 100th cycle is C2; the calculation formula for the cycling capacity retention rate: C2 / C1×100%. The test results are shown in Figure 2 。

[0091] From Figure 2 the test results of the examples and the control group, it can be seen that the electrolyte material package of the examples of the present invention combined with the liquid injection method can effectively improve the rate cycling performance of the battery. From Figure 2 the test results of Examples 1-5, it can be seen that the battery has the best rate cycling performance when the content of the first additive in the electrolyte material package is 3%.

[0092] To sum up, in Examples 1-5 of the present invention, the first material package containing the first additive is injected 30 minutes before the end of the vacuum baking, and then the first non-polar organic solvent injected into the battery is pumped out, while the first additive remains in the battery and undergoes a decomposition reaction with water under high-temperature conditions. During the reaction process, the temperature of the winding core can be reduced, and the by-products of the reaction are carried out during the continuous vacuum pumping process without introducing impurities. After the baking process is completed, the liquid injection operation of the second material package is then carried out. As the temperature decreases, the density of the electrolyte will increase, and the space required to inject the same amount of electrolyte will be smaller. In this way, more electrolyte can be injected into the limited space of the square aluminum shell, and at the same time, the moisture inside the battery can be consumed. The baking time of the battery added with the first material package containing the first additive can be effectively reduced, which can not only improve the production efficiency of the baking and liquid injection processes, but also improve the electrochemical performance and safety performance of the battery.

[0093] In the present invention, the terms "one embodiment", "some embodiments", "an example", "a specific example", or "some examples", etc. mean that the specific features, structures, materials, or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials, or characteristics described may be combined in any one or more embodiments or examples in a suitable manner. In addition, without contradiction, those skilled in the art can combine and combine the different embodiments or examples described in this specification and the features of different embodiments or examples.

[0094] Although the embodiments of the present invention have been shown and described above, it can be understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those of ordinary skill in the art can make changes, modifications, substitutions, and variations to the above embodiments within the scope of the present invention.

Claims

1. An electrolyte material package, characterized in that, It includes a first material package and a second material package. The first material contains a first non-aqueous organic solvent and a first additive, and the first additive is vinyl fluorobutyrate. The second material contains a lithium salt or a sodium salt, a second non-aqueous organic solvent, and a second additive.

2. The electrolyte material package according to claim 1, wherein Based on the total mass of the electrolyte material package being 100 wt%, the content of the first additive is 1 - 6 wt%.

3. The electrolyte material package according to claim 1 or 2, characterized in that, Based on the total mass of the electrolyte material package being 100 wt%, the content of the second additive is 1 - 6 wt%.

4. The electrolyte material package according to claim 1 or 2, characterized in that The second additive is vinylene carbonate.

5. The electrolyte material package according to claim 1 or 2, characterized in that, Based on the total mass of the electrolyte material package being 100 wt%, the sum of the contents of the first non-aqueous organic solvent and the second non-aqueous organic solvent is 75 - 80 wt%.

6. The electrolyte material package according to claim 1 or 2, characterized in that, The mass ratio of the first non-aqueous organic solvent to the second non-aqueous organic solvent is 1:4 - 2:

3.

7. The electrolyte material package according to claim 1 or 2, characterized in that The first non-aqueous organic solvent and the second non-aqueous organic solvent independently include a cyclic carbonate solvent and a linear carbonate solvent; Optionally, the cyclic carbonate solvent includes ethylene carbonate; Optionally, the linear carbonate solvent includes at least one of dimethyl carbonate, ethyl methyl carbonate, diethyl carbonate, and methyl propyl carbonate.

8. The electrolyte material package according to claim 1 or 2, characterized in that, Based on the total mass of the electrolyte material package being 100 wt%, the content of the lithium salt or the sodium salt is 15 - 20 wt%.

9. An electrolyte injection method, characterized in that, It includes the following steps: Within 20 min - 1 h before the end of the battery baking process, inject the first material package in the electrolyte material package according to any one of claims 1 - 8 into the battery, then turn off the heating function of the vacuum baking device. After the baking process ends, turn off the vacuum pumping function of the vacuum baking device, and then inject the second material package in the electrolyte material package according to any one of claims 1 - 8 into the battery.

10. A secondary battery, characterized in that, It includes an electrolyte, and the electrolyte is prepared from the electrolyte material package according to any one of claims 1 - 8, or is prepared by the electrolyte injection method according to claim 9.

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