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

Abstract

The invention belongs to the technical field of lithium ion batteries, and particularly relates to preparation of a surface-coated modified calcium carbonate electrolyte and application of the surface-coated modified calcium carbonate electrolyte in a lithium ion battery. The surface-coated modified calcium carbonate is used in the lithium battery electrolyte, the electrolyte comprises a lithium salt, a surface-coated modified calcium carbonate additive and a carbonic ester compound, and the mass of the surface-coated modified calcium carbonate additive is 0.1-10% of the mass of the lithium battery electrolyte. The surface-coated modified calcium carbonate is used as an electrolyte additive, so that the surface of an electrode material can be protected, and corrosive components of the electrolyte are prevented from being in direct contact with an electrode, so that the rate capability of the lithium ion battery is improved, and the cycle life of the lithium ion battery is prolonged. The innovative application that the surface-coated modified calcium carbonate is used as an electrolyte additive is expected to play an important role in a future battery technology.

Description

Technical Field

[0001] The present invention relates to the technical field of lithium-ion batteries, and in particular to the preparation of an electrolyte with surface-coated modification, which can not only improve the performance and safety of the battery, but also enhance the cycle life and high-rate performance of the battery. Background Art

[0002] With the rapid development of electric vehicles and portable electronic devices, the performance requirements for lithium-ion batteries are constantly increasing. As one of the core components of lithium-ion batteries, the performance of the electrolyte directly affects important indicators such as the cycle life, energy density, and thermal stability of the battery. Existing electrolyte additives are mostly 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 by-products (such as HF), which can lead to a decrease in battery capacity and a reduction in safety. Calcium carbonate has attracted much attention due to its excellent adsorption and chemical neutralization properties. However, bare calcium carbonate may undergo side reactions with the electrolyte, limiting its practical application. By adding surface-coated modified calcium carbonate such as CaCO 3 @SiO 2 、CaCO 3 @ZnO、CaCO 3 @TiO 2 @Ag、CaCO 3 @ Al 2 O 3 、CaCO 3 @Cu and other materials, the chemical stability and dispersibility can be effectively improved, making it more suitable as an electrolyte additive, which helps to increase the migration rate of lithium ions in the electrode, reduce the internal resistance, and improve the rate performance and cycle performance of the battery. Summary of the Invention

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

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

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

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

[0007] Preferably, the coating layer of the surface-coated modified calcium carbonate is one or more of silver, copper, silica, 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%; the addition amount of the electrolyte each time is 40 - 60 μl.

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

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

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

[0013] The lithium ion button battery includes a positive electrode, a negative electrode, a shrapnel, a gasket, and a separator; the material used for the positive electrode is lithium iron phosphate, lithium cobaltate, nickel cobalt manganese ternary material, or sulfur; the separator is a polypropylene or polyethylene separator.

[0014] Compared with the prior art, the beneficial results of the present invention are as follows: applying the surface-coated modified calcium carbonate to the electrolyte can form a protective layer between the electrolyte and the electrode, reducing the contact between the corrosive components in the electrolyte and the electrode, further improving the safety of the battery. This electrolyte can enhance the stability of the SEI film (solid electrolyte interface film) through chemical adsorption or physical shielding, making it denser and more uniform, avoiding excessive decomposition and adverse reactions, thereby extending the service life of the battery and improving the efficiency. Detailed Embodiments

[0015] In order to further illustrate the present invention, the following is a detailed description of a surface-coated modified calcium carbonate as a lithium ion electrolyte provided by the present invention in combination with embodiments, but it should not be construed as a limitation to the protection scope of the present invention.

[0016] Example 1:

[0017] Electrolyte preparation: Dissolve LiPF 6 in a mixed solvent of dimethyl carbonate (DMC), ethylene carbonate (EC), and ethyl methyl carbonate (EMC) with a mass ratio of 1:1:1 to form a 1 mol / L LiPF 6solution as the reference electrolyte; then add CaCO 3 @SiO 2 additive at a dosage of 1% to obtain the electrolyte for lithium batteries.

[0018] Battery assembly: Stack the lithium sheet, separator, gasket, shrapnel, positive electrode sheet, and battery case in sequence, drop 50 μL of the electrolyte, and then seal it with a battery encapsulation machine.

[0019] The whole operation is carried out in a glove box with the water and oxygen content below 0.1 ppm.

[0020] Example 2:

[0021] Electrolyte preparation: Dissolve LiPF 6 in a mixed solvent of dimethyl carbonate (DMC), ethylene carbonate (EC), and ethyl methyl carbonate (EMC) with a mass ratio of 1:1:1 to form a 1 mol / L LiPF 6 solution as the reference electrolyte; then add CaCO 3 @ZnO additive at a dosage of 1% to obtain the electrolyte for lithium batteries.

[0022] Battery assembly: Stack the lithium sheet, separator, gasket, shrapnel, positive electrode sheet, and battery case in sequence, drop 50 μL of the electrolyte, and then seal it with a battery encapsulation machine.

[0023] The whole operation is carried out in a glove box with the water and oxygen content below 0.1 ppm.

[0024] Example 3:

[0025] Electrolyte preparation: Dissolve LiPF 6 in a mixed solvent of dimethyl carbonate (DMC), ethylene carbonate (EC), and ethyl methyl carbonate (EMC) with a mass ratio of 1:1:1 to form a 1 mol / L LiPF 6 solution as the reference electrolyte; then add CaCO 3 @TiO 2 @Ag additive at a dosage of 1% to obtain the electrolyte for lithium batteries.

[0026] Battery assembly: Stack the lithium sheet, separator, gasket, shrapnel, positive electrode sheet, and battery case in sequence, drop 50 μL of the electrolyte, and then seal it with a battery encapsulation machine.

[0027] The whole operation is carried out in a glove box with the water and oxygen content below 0.1 ppm.

[0028] Comparative Example 1:

[0029] Electrolyte preparation: Dissolve LiPF6 A 1 mol / L LiPF solution formed by dissolving in a mixed solvent of dimethyl carbonate (DMC), ethylene carbonate (EC), and ethyl methyl carbonate (EMC) with a mass ratio of 1:1:1 6 is used as the reference electrolyte.

[0030] Battery assembly: Stack the lithium sheet, separator, gasket, shrapnel, positive electrode sheet, and battery case in sequence, drop 50 μL of electrolyte, and then seal it with a battery encapsulation machine.

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

[0032] After standing at room temperature for one day, the batteries of the above examples and comparative examples are subjected to charge-discharge rate tests and cycle tests.

[0033] Rate test: The positive electrode test voltage is 2.0 - 4.2 V. The examples and comparative examples are cycled five times at 0.2C, 0.5C, 1C, 2C, 3C, and 5C respectively for the rate test. The test results are as Figure 1 shown.

[0034] Figure 1 The results show that, compared with the comparative examples, the examples have higher capacities at various rates, especially stable performance at high rates (such as 3C and 5C), indicating that the surface-coated and modified calcium carbonate electrolyte significantly improves the rate performance of lithium batteries.

[0035] Cycle test: The positive electrode test voltage is 2.0 - 4.2 V. The examples and comparative examples are cycled twice at a current density of 0.5C for activation, and then a 200-cycle performance test is carried out at a current density of 5C. The test results are as Figure 2 shown.

[0036] Figure 2 The results show that the capacities of the examples at 5C are generally higher than those of the comparative examples, and after 200 cycles, the capacities of the examples are still close to their initial values, indicating that the surface-coated and modified calcium carbonate electrolyte significantly improves the retention rate of the battery capacity of lithium batteries.

Claims

1. A lithium ion electrolyte having a surface-coated modified calcium carbonate, characterized in that: include: Lithium salts, surface-coated modified calcium carbonate additives and carbonate compounds.

2. The lithium ion electrolyte according to claim 1, characterized in that The lithium salt is one or more of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, lithium difluorooxalatoborate, lithium trifluoromethanesulfonate, lithium bistrifluoromethanesulfonyl imide and lithium bisfluorosulfonyl imide.

3. The lithium ion electrolyte according to claim 1, characterized in that The concentration of lithium salt in the lithium ion battery is 0.2-5 mol / L.

4. The lithium ion electrolyte according to claim 1, characterized in that The surface-coated modified calcium carbonate additive is calcium carbonate coated with different materials, and the coating material includes inorganic material, organic material or conductive material.

5. The lithium ion electrolyte according to claim 1, characterized in that The particle size of the surface-coated modified calcium carbonate additive particles is 1-200 nm, and the thickness of the coating layer is 5-50 nm.

6. The lithium ion electrolyte according to claim 1, characterized in that The mass fraction of the surface-coated modified calcium carbonate additive is 0.1%-5%; the amount of electrolyte added each time is 30-80 μl.

7. The lithium ion electrolyte according to claim 1, characterized in that The carbonate organic solvent is one or more of ethylene carbonate, propylene carbonate, ethylene carbonate, dimethyl carbonate, diethyl carbonate and ethyl methyl carbonate.

8. According to claim 1, it is characterized in that: Carbonate organic solvents usually account for 80% to 95% of the total electrolyte composition.

9. A lithium ion battery, characterized in that: Comprising the electrolyte described in any one of claims 1 to 8.

10. The lithium ion button cell according to claim 9, comprising a positive electrode, a negative electrode, a spring, a gasket and a separator, characterized in that: The material used for the positive electrode is lithium iron phosphate, lithium cobalt oxide, lithium nickel oxide, nickel-cobalt-manganese ternary material or sulfur; the diaphragm is polypropylene or polyethylene diaphragm.

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