CROSS-REFERENCE TO RELATED APPLICATION

The present application claims priority to Korean Patent Application No. 10-2018-0173268 filed on Dec. 31, 2018, the entire contents of which is incorporated herein for all purposes by this reference.

BACKGROUND OF THE INVENTION

Field of the Invention

The present invention relates to a negative electrode including an active material having a core-shell structure, a manufacturing method thereof and a secondary battery including the same. More particularly, it relates to an ultrabattery to which an active material having a core-shell structure is applied.

Description of Related Art

In general, an ultrabattery refers to a battery for hybrid vehicles which is produced by combining an ultracapacitor (or a supercapacitor) and a lead-acid battery used in conventional internal combustion engines. In a transitional stage in which lithium batteries or fuel cells are commercialized in the hybrid vehicle market, a nickel metalhydride battery occupies the majority of batteries until now. The nickel metal hydride battery has an energy density and a power density, which satisfy requirements of hybrid vehicles, and has a long lifespan. However, the nickel metal hydride battery is very expensive. To make up for such a drawback, an ultrabattery, in which a lead-acid battery being inexpensive and having an excellent energy density and an ultracapacitor having an excellent power density are combined to exhibit performance suitable for hybrid vehicles, has been developed. Such an ultrabattery has advantages, such as low price, enhanced power characteristics and a long lifespan, and is thus being vigorously developed. However, such ultrabattery technology was not yet properly developed in Korea, but there is a high possibility that the ultrabattery technology will be applied to hybrid vehicles and enter the large-capacity energy storage market and thus localization of the ultrabattery technology is urgently required, heavy energy loss was still caused by sulfation reaction between an electrolyte and electrodes including lead due to charge and discharge for a long time, and consequently, a discharge capacity was not sufficient.

The information disclosed in this Background of the Invention section is only for enhancement of understanding of the general background of the invention and may not be taken as an acknowledgement or any form of suggestion that this information forms the prior art already known to a person skilled in the art.

BRIEF SUMMARY

Various aspects of the present invention are directed to providing a negative electrode active material which suppresses sulfation at a negative electrode during discharging and may thus reduce activation loss and Ohmic loss, as compared to conventional lead-acid batteries.

Various aspects of the present invention are directed to providing an electrode for ultrabatteries which may be driven at a voltage having a higher forward voltage driving range, and a manufacturing method thereof.

Various aspects of the present invention are directed to providing a negative electrode of a secondary battery, the negative electrode including an electrode plate including lead, and an active material layer provided on the electrode plate and including composite particles having a core-shell structure, wherein a core of the composite particle may include lead and a shell of the composite particle may include carbon.

In an exemplary embodiment of the present invention, the lead may form a crystalline structure oxidized by heat treatment.

In another exemplary embodiment of the present invention, the carbon may form a porous amorphous structure oxidized by heat treatment.

In yet another exemplary embodiment of the present invention, an average pore size of particles of the carbon may be 1 to 100 nm.

In yet another exemplary embodiment of the present invention, a specific surface area of the composite particles may be 1 to 5,000 m2/g.

In still yet another exemplary embodiment of the present invention, the specific surface area of the composite particles may be 900 to 1,500 m2/g.

In a further exemplary embodiment of the present invention, a pore volume of the composite particles may be 0.1 to 20 cm3/g.

In another further exemplary embodiment of the present invention, a ratio of the crystalline structure in the composite particles may be 0.1 to 50%.

In yet another further exemplary embodiment of the present invention, a weight ratio of the lead to the carbon in the active material layer may be 1:0.001 to 1:9.

Various aspects of the present invention are directed to providing a secondary battery including a positive electrode, the negative electrode, and an electrolyte interposed between the positive electrode and the negative electrode.

Various aspects of the present invention are directed to providing a manufacturing method of a negative electrode of a secondary battery, the manufacturing method including preparing a mixture by physically mixing lead and carbon, preparing an active material including composite particles having a core-shell structure by performing heat treatment of the mixture, preparing an electrode slurry by mixing the active material with a binder and a solvent, and manufacturing the negative electrode by forming a coating layer by coating an electrode plate including lead with the electrode slurry, wherein, in the preparing the mixture, the lead may include lead particles having a diameter of 0.1 to 50 μm, and, in the preparing the active material, a core of the composite particle may include the lead, and a shell of the composite particle may include the carbon.

In an exemplary embodiment of the present invention, in the preparing the mixture, the carbon may include carbon particles having a diameter of 0.01 to 50 μm.

In another exemplary embodiment of the present invention, in the preparing the mixture, a content of the lead may be 10 to 99 parts by weight and a content of the carbon may be 0.1 to 90 parts by weight.

In yet another exemplary embodiment of the present invention, in the preparing the mixture, the mixture may be prepared by physically stirring the lead and the carbon at a temperature of 20° C. to 30° C. for 10 minutes to 24 hours.

In yet another exemplary embodiment of the present invention, in the preparing the active material, the composite particles may be prepared by performing heat treatment of the mixture at a temperature of 100° C. to 380° C. for 1 to 24 hours.

In still yet another exemplary embodiment of the present invention, in the preparing the electrode slurry, a content of the active material may be 2 to 94% by weight, a content of the binder may be 1 to 48% by weight, and a content of the solvent may be 5 to 95% by weight.

In a further exemplary embodiment of the present invention, in the preparing the electrode slurry, the binder may be one selected from the group consisting of Nafion, polyester (PET), polyphenyl oxide (PPO), polytetrafluoroethylene (PTFE), poly etherether ketone (PEEK), polyvinylidene fluoride (PVDF), polyphenylene sulfide (PPS), carboxymethyl cellulose sodium (CMS), styrene butadiene rubber (SBR), polyethylene glycol (PEG) and combinations thereof.

In another further exemplary embodiment of the present invention, in the manufacturing the negative electrode, a thickness of the coated active material layer may be 1 to 100 μm.

Other aspects and exemplary embodiments of the present invention are discussed infra.

The above and other features of the present invention are discussed infra.

