Preparation of surface-coated modified calcium carbonate electrolyte and application thereof in lithium ion battery

Abstract

The application belongs to the technical field of lithium ion batteries, and specifically relates to a kind of surface-coated modified calcium carbonate electrolyte preparation and application in lithium ion battery.The surface-coated modified calcium carbonate is used in lithium battery electrolyte, the electrolyte includes lithium salt, surface-coated modified calcium carbonate additive and carbonate compound, the mass of surface-coated modified calcium carbonate additive used is 0.1%-10% of the mass of lithium battery electrolyte.The surface-coated modified calcium carbonate in the application can protect the surface of electrode material as electrolyte additive, avoid the direct contact of corrosive components of electrolyte with electrode, thereby improve the rate performance and cycle life of lithium ion battery.The innovative application of surface-coated modified calcium carbonate as electrolyte additive is expected to play an important role in future battery technology.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of lithium ion batteries, in particular to a preparation of surface-coated modified electrolyte, which not only improves the performance and safety of the battery, but also improves the cycle life and high-rate performance of the battery. BACKGROUND

[0002] With the rapid development of electric vehicles and portable electronic devices, the performance requirements of lithium ion batteries are constantly improving. As one of the core components of lithium ion batteries, the performance of electrolyte directly affects important indicators such as the cycle life, energy density, and thermal stability of the battery. Existing electrolyte additives are mainly used to improve the thermal stability of the battery, inhibit side reactions, and improve the safety of the battery, but there is still room for performance improvement. The performance of lithium ion batteries is closely related to the stability of the electrolyte. Traditional electrolytes are prone to decomposition at high temperatures or high voltages, generating acidic byproducts (such as HF), which leads to capacity attenuation and reduced safety of the battery. Calcium carbonate has attracted attention due to its excellent adsorption and chemical neutralization performance, however, bare calcium carbonate may have side reactions with electrolyte, limiting its practical application. By adding surface-coated modified calcium carbonate materials such as CaCO3@SiO2, CaCO3@ZnO, CaCO3@TiO2@Ag, CaCO3@Al2O3, CaCO3@Cu, etc., the chemical stability and dispersibility of the material can be effectively improved, making it more suitable as an electrolyte additive, which helps to improve the migration rate of lithium ions in the electrode, reduce internal resistance, and improve the rate performance and cycle performance of the battery. SUMMARY

[0003] In view of the defects of existing lithium ion battery electrolytes, the purpose of the present application is to provide a preparation of surface-coated modified calcium carbonate electrolyte and the application of the electrolyte. The addition of calcium carbonate can effectively improve the electrochemical performance of lithium ion batteries and improve their safety. The electrolyte can reduce the deposition and growth of lithium dendrites, improving the electrochemical performance of the battery.

[0004] The present application provides a surface-coated modified calcium carbonate electrolyte for lithium ion batteries, which is composed of the following components: lithium salt, surface-coated modified calcium carbonate additive, and carbonate compound.

[0005] Preferably, the lithium salt is one or more of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, lithium difluoro(oxalato)borate, and lithium trifluoromethanesulfonate.

[0006] Preferably, the concentration of lithium salt in the lithium ion battery is 0.5-1.5 mol / L.

[0007] Preferably, the coating layer of the surface-coated modified calcium carbonate is one or more of silver, copper, silicon dioxide, titanium dioxide, zinc oxide, and barium sulfate.

[0008] Preferably, the particle size of the calcium carbonate is 50-150 nm, and the thickness of the coating layer is 5-10 nm.

[0009] Preferably, the mass fraction of the surface-coated modified calcium carbonate additive is 0.5%-2%, and the addition amount of the electrolyte is 40-60 μl each time.

[0010] Preferably, the carbonate organic solvent is one or more of propylene carbonate, ethylene carbonate, and dimethyl carbonate.

[0011] Preferably, the carbonate organic solvent generally accounts for 90%-95% of the total components of the electrolyte.

[0012] The surface-coated modified calcium carbonate electrolyte is the electrolyte for lithium ion batteries described above.

[0013] The lithium ion button cell comprises a positive electrode, a negative electrode, a spring, a gasket, and a separator; the material of the positive electrode is lithium iron phosphate, lithium cobaltate, ternary material of nickel-cobalt-manganese, or sulfur; and the separator is a polypropylene or polyethylene separator.

[0014] Compared with the prior art, the beneficial results of the present application are as follows: the surface-coated modified calcium carbonate is used in the electrolyte, which can form a protective layer between the electrolyte and the electrode, reduce the contact between the corrosive components in the electrolyte and the electrode, further improve the safety of the battery, and enhance the stability of the SEI film (solid electrolyte interface film) through chemical adsorption or physical shielding, so that the SEI film is more dense and uniform, and excessive decomposition and adverse reactions are avoided, thereby prolonging the service life of the battery and improving the efficiency. DETAILED DESCRIPTION

[0015] In order to further illustrate the present application, a surface-coated modified calcium carbonate as a lithium ion electrolyte provided by the present application is described in detail in the following examples, but it should not be understood as limiting the scope of protection of the present application.

[0016] Example 1:

[0017] Electrolyte configuration: LiPF6 is dissolved in a mixed solvent of dimethyl carbonate (DMC), ethylene carbonate (EC), and methyl ethyl carbonate (EMC) with a mass ratio of 1:1:1 to form a solution of 1 mol / L LiPF6, which is used as a reference electrolyte; then, the prepared reference electrolyte is added with CaCO3@SiO2 additive, and the addition amount is 1%, to obtain an electrolyte for lithium batteries.

[0018] Battery assembly: lithium sheet, separator, gasket, spring, positive electrode sheet, and battery shell are sequentially stacked, 50 μL of electrolyte is added dropwise, and then sealed by a battery packaging machine.

[0019] The whole operation was carried out in a glove box with water and oxygen content less than 0.1 ppm.

[0020] Example 2:

[0021] Electrolyte preparation: LiPF6 was dissolved in a mixed solvent of dimethyl carbonate (DMC), ethylene carbonate (EC) and methyl ethyl carbonate (EMC) with a mass ratio of 1:1:1 to form a solution of 1 mol / L LiPF6 as a reference electrolyte; then CaCO3@ZnO additive was added to the prepared reference electrolyte, and the addition amount was 1%, to obtain an electrolyte for lithium batteries.

[0022] Battery assembly: lithium sheet, separator, gasket, spring, positive electrode sheet and battery shell were stacked in turn, 50 μL of electrolyte was added dropwise, and then sealed by a battery packaging machine.

[0023] The whole operation was carried out in a glove box with water and oxygen content less than 0.1 ppm.

[0024] Example 3:

[0025] Electrolyte preparation: LiPF6 was dissolved in a mixed solvent of dimethyl carbonate (DMC), ethylene carbonate (EC) and methyl ethyl carbonate (EMC) with a mass ratio of 1:1:1 to form a solution of 1 mol / L LiPF6 as a reference electrolyte; then CaCO3@TiO2@Ag additive was added to the prepared reference electrolyte, and the addition amount was 1%, to obtain an electrolyte for lithium batteries.

[0026] Battery assembly: lithium sheet, separator, gasket, spring, positive electrode sheet and battery shell were stacked in turn, 50 μL of electrolyte was added dropwise, and then sealed by a battery packaging machine.

[0027] The whole operation was carried out in a glove box with water and oxygen content less than 0.1 ppm.

[0028] Comparative Example 1:

[0029] Electrolyte preparation: LiPF6 was dissolved in a mixed solvent of dimethyl carbonate (DMC), ethylene carbonate (EC) and methyl ethyl carbonate (EMC) with a mass ratio of 1:1:1 to form a solution of 1 mol / L LiPF6 as a reference electrolyte.

[0030] Battery assembly: lithium sheet, separator, gasket, spring, positive electrode sheet and battery shell were stacked in turn, 50 μL of electrolyte was added dropwise, and then sealed by a battery packaging machine.

[0031] The whole operation was carried out in a glove box with water and oxygen content less than 0.1 ppm.

[0032] The above example and comparative example batteries were allowed to stand at room temperature for one day, and then subjected to charge-discharge rate test and cycle test.

[0033] Rate test: the positive electrode test voltage was 2.0-4.2V, and the examples and comparative examples were subjected to rate test at 0.2C, 0.5C, 1C, 2C, 3C and 5C respectively for five cycles. The test results are shown in Table 2. Figure 1

[0034] Figure 1 The results show that the capacity of the examples is higher than that of the comparative examples at various rates, especially at high rates (such as 3C and 5C), which indicates that the surface-coated modified calcium carbonate electrolyte significantly improves the rate performance of the lithium battery.

[0035] Cycle test: the positive electrode test voltage was 2.0-4.2V, and the examples and comparative examples were cycled at a current density of 0.5C for two cycles as activation, and then subjected to 200-cycle performance test at a current density of 5C. The test results are shown in Table 3. Figure 2

[0036] Figure 2 The results show that the capacity of the examples at 5C is higher than that of the comparative examples as a whole, and the capacity of the examples is still close to the initial value after 200 cycles, which indicates that the surface-coated modified calcium carbonate electrolyte significantly improves the capacity retention rate of the lithium battery.​​

Claims

1. A lithium-ion electrolyte, characterized by, The application relates to a lithium salt, a carbonate compound and a surface-coated modified calcium carbonate as electrolyte additives, wherein the coating layer of the calcium carbonate is one or several of silver, copper, silicon dioxide, titanium dioxide, zinc oxide and barium sulfate. The lithium salt is one or several of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, lithium difluoro(oxalato)borate, lithium trifluoromethanesulfonate, lithium bis(trifluoromethanesulfonyl)imide and lithium bis(fluorosulfonyl)imide.

2. The lithium-ion electrolyte of claim 1, wherein, The concentration of the lithium salt in the lithium ion battery is 0.2-5 mol / L.

3. The lithium-ion electrolyte of claim 1, wherein, The particle size of the surface-coated modified calcium carbonate additive is 1-200 nm, and the thickness of the coating layer is 5-50 nm.

4. The lithium-ion electrolyte of claim 1, wherein, The mass fraction of the surface-coated modified calcium carbonate additive is 0.1%-5%; and the adding amount of the electrolyte is 30-80 muL each time.

5. The lithium-ion electrolyte of claim 1, wherein, The carbonate compound is one or several of ethylene carbonate, propylene carbonate, vinyl carbonate, dimethyl carbonate, diethyl carbonate and methyl ethyl carbonate.

6. The lithium-ion electrolyte of claim 1, wherein, The carbonate compound accounts for 80%-95% of the total mass of the electrolyte.

7. The lithium-ion electrolyte of claim 1, wherein, The application further discloses the electrolyte as claimed in any one of claims 1 to 7.

8. A lithium-ion battery, characterized by, The material of the positive electrode is lithium iron phosphate, lithium cobaltate, lithium nickelate, a ternary material of nickel, cobalt and manganese or sulfur; and the separator is a polypropylene or polyethylene separator.

9. The lithium-ion battery of claim 8, comprising a positive electrode, a negative electrode, a spring, a gasket, and a separator, wherein: ​

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