Cross-linked compound particle and secondary battery including the same

Abstract

Disclosed are a cross-linked compound particle and a secondary battery including the same. More particularly, a compound particle which includes a monomer and a polymerization initiator, as a core and a film including a material disappeared at predetermined temperature as a shell is provided.

Claims

1. A compound particle comprised in an electrolyte for a lithium-ion polymer battery, wherein the compound particle comprises: a monomer and a polymerization initiator, as a core; and a film as a shell, wherein the monomer is acrylonitrile, wherein the film comprises a thermoplastic resin that is polyacrylonitrile (PAN), and wherein the polymerization initiator is a photoinitiator, a thermoinitiator, a radiation initiator or a mixture thereof.

2. The compound particle comprised in an electrolyte for a lithium-ion polymer battery according to claim 1, wherein the photoinitiator is at least one selected from the group consisting of -hydroxyketone-based compounds, phenyl glyoxylate-based compounds, benzyl dimethyl ketal-based compounds, -amino ketone-based compounds, monoacyl phosphine-based compounds, bisacyl phosphine-based compounds, phosphine oxide-based compounds, metallocene-based compounds and iodonium salts.

3. The compound particle comprised in an electrolyte for a lithium-ion polymer battery according to claim 1, wherein the thermoinitiator is at least one selected from the group consisting of axo-based compounds, peroxy-based compounds, tert-butyl peracetate, peracetic acid and potassium persulfate.

4. The compound particle comprised in an electrolyte for a lithium-ion polymer battery according to claim 1, wherein the radiation initiator is at least one selected from the group consisting of X-rays, alpha particle gamma rays and high-energy electron rays.

5. The compound particle comprised in an electrolyte for a lithium-ion polymer battery according to claim 1, wherein the film further comprises a vanadium compound.

6. The compound particle comprised in an electrolyte for a lithium-ion polymer battery according to claim 5, wherein the vanadium compound is at least one selected from the group consisting of vanadium(II) chloride, vanadium(III) chloride, vanadium tetrachloride, vanadium(II) bromide, vanadium(III) bromide, vanadium tetrabromide, vanadium(II) iodide and vanadium(III) iodide.

7. The compound particle comprised in an electrolyte for a lithium-ion polymer battery according to claim 1, wherein the film is a copolymer of a thermoplastic resin and a vanadium compound.

8. The compound particle comprised in an electrolyte for a lithium-ion polymer battery according to claim 1, wherein the core further comprises a foaming agent.

9. The compound particle comprised in an electrolyte for a lithium-ion polymer battery according to claim 8, wherein the foaming agent is at least one selected from the group consisting of azodicarbonamide (ADCA), azobisisobutyronitrile (AZDN), N,N-dimethyl-N,N-dinitroso-terephthalate (NTA), 4,4-oxybis(benzenesulfonyl hydrazide (OBSH), 3,3-sulfonbis(benzene-sulfonyl hydrazide, 1,1-azobisformamide (ABFA)-(azodicarbonamide), p-ttoluenesulfonyl semicarbazide and barium azodicarboxylate (BaAC).

10. The compound particle comprised in an electrolyte for a lithium-ion polymer battery according to claim 1, wherein a thickness of the film is 1 m to 10 m.

11. The compound particle comprised in an electrolyte for a lithium-ion polymer battery according to claim 1, wherein a thickness of the film is 2 m to 5 m.

12. A lithium-ion polymer battery comprising the compound particle according to claim 1.

13. A battery pack comprising the lithium-ion polymer battery according to claim 12.

14. A device using the battery pack according to claim 13 as a power source.

Description

MODE FOR INVENTION

(1) Now, the present invention will be described in more detail with reference to the accompanying drawings. These examples are provided for illustrative purposes only and should not be construed as limiting the scope and spirit of the present invention.

Example 1

Preparation of Positive Electrode

(2) Li(Ni.sub.6Mn.sub.2Co.sub.2)O.sub.2 as a positive electrode active material, carbon black as a conductive material and PVdF as a binder were added to n-methyl-2-pyrrolidone (NMP) in a weight ratio of 94:3:3 and mixed, thereby preparing a positive electrode mixture.

(3) After coating the prepared positive electrode mixture on aluminum foil having a thickness of 12 m as a positive electrode current collector to a thickness of 66 m, rolling and drying were carried out, thereby manufacturing a positive electrode.

(4) Preparation of Negative Electrode

(5) Natural graphite as a negative electrode, carbon black as a conductive material, styrene butadiene rubber (SBR) and carboxymethyl cellulose (CMC) were added to deionized H.sub.2O (distilled water) in a weight ratio of 94.5:2:2:1.5 and mixed, thereby preparing a negative electrode mixture.

(6) Copper foil having a thickness of 10 m was used, and the prepared negative electrode mixture was coated onto the negative electrode current collector in a thickness of 73 m. Subsequently, rolling and drying were carried out, thereby manufacturing a positive electrode.

(7) Preparation of Secondary Battery

(8) An SRS separator (film material: Toray, inorganic layer: LG chemistry, total thickness: 16 um) was disposed between the negative electrode and the positive electrode, thereby manufacturing an electrode assembly. Subsequently, the electrode assembly was accommodated in a pouch type battery case. Subsequently, a mixture of ethyl carbonate, dimethyl carbonate and ethylmethyl carbonate mixed in a volumetric ratio of 3:2:5 as an electrolyte solution, and a non-aqueous lithium electrolyte solution including 1 M LiPF.sub.6 as a lithium salt were used. Compound particles including an acrylonitrile monomer (AN) as a core and a polyacrylonitrile (PAN) film formed to a thickness of 2 m as a shell were added thereto, thereby manufacturing a lithium secondary battery.

Example 2

(9) A lithium secondary battery was manufactured in the same manner as in Example 1, except that surfaces of positive and negative electrodes were coated without addition of the compound particles to the electrolyte solution.

Comparative Example 1

(10) A lithium secondary battery was manufactured in the same manner as in Example, except that an electrolyte solution not including the compound particles was used.

Comparative Example 2

(11) A lithium secondary battery was manufactured in the same manner as in Example, except that azobisisobutyronitrile (AZDN) as an additive was injected and an electrolyte solution not including the compound particles was used.

Experimental Example 1

Lifespan Characteristic Evaluation Experiment

(12) The batteries manufactured in each of Examples 1 and 2, and Comparative Examples 1 and 2 were charged and discharge 500 times at 45 C. and 0.5 C. Subsequently, 300- and 500 discharge capacity maintenance ratios with respect to once-discharged capacity were calculated, and results thereof are summarized in Table 1 below.

Experimental Example 2

Evaluation Experiment of High-Temperature Storage Characteristics

(13) The batteries manufactured according to each of Examples 1 and 2, and Comparative Examples 1 and 2 were stored for 3 weeks at 60 C. in a full charge state, and then a resistance increase ratio and a thickness increase ratio thereof were measured. Results are summarized in Table 1 below.

(14) TABLE-US-00001 TABLE 1 Inclusion of Discharge capacity Resistance Thickness electrolyte Inclusion ratio at each cycle with increase increase solution of respect to once- after storing after storing additive compound discharge capacity (%) for 3 weeks for 3 weeks (wt %) particle 300 times 500 times at 60 C. (%) at 60 C. (%) Example 1 2% Inclusion 90 80 14% 3% (electrolyte solution) Example 2 2% Inclusion 90 82 13% 3% (electrode) Comparative 0% None 92 81 14% 3% Example 1 Comparative 2% None 74 52 180% 240% Example 2

(15) As shown in Table 1, it can be confirmed that the batteries according to Examples 1 and 2, in which the compound particles including 2 wt % of the mixture of the monomer and polymerization initiator were added to the electrolyte or coated on the electrode, and the battery according to Comparative Example 1, in which the monomer and the polymerization initiator were not added, exhibit higher capacity, when compared with the battery according to Comparative Example 2, in which 2 wt % of the mixture of the monomer and the polymerization initiator was added to the electrolyte solution. Accordingly, it can be confirmed that the shell prevents that the core material deteriorates battery performance, and thus, characteristics of the batteries are improved.

(16) This is since the battery according to Comparative Example 2, in which the monomer and the polymerization initiator were directly added to the electrolyte solution, exhibits increased viscosity through addition of the additive, and thus, sufficient impregnation of the electrolyte solution is difficult and gas is massively released due to continuous decomposition during high-temperature storage.

(17) It can be confirmed that, from the lifespan and high-temperature storage characteristic results, the batteries according to Examples 1 and 2 in which the concentrations of the additives were properly controlled by including the compound particle including the monomer and the polymerization initiator exhibit excellent characteristics.

Experimental Example 3

(18) The battery according to each of Examples 1 and 2 and Comparative Examples 1 and 2 was subjected to a nail penetration test in a fully charged state. Results are summarized in Table 2 below.

(19) TABLE-US-00002 TABLE 2 Inclusion Highest of temperature electrolyte Inclusion of battery solution of Nail during nail additive compound penetration penetration (wt %) particle test result test Example 1 2% Inclusion Not ignited 73 C. (electrolyte solution) Example 2 2% Inclusion Not ignited 69 C. (electrode) Comparative 0% None Ignited 540 C. Example 1 (ignited) Comparative 2% None Not ignited 65 C. Example 2

(20) As shown in Table 2, it can be confirmed that the battery including the monomer and the initiator as a core is not ignited in the nail penetration test. Accordingly, it can be confirmed that the batteries according to Examples 1 and 2, which are not ignited during the nail penetration test and do not exhibit deteriorated battery performance, have improved characteristics, when compared with the battery according to Comparative Example 2 which is not ignited during the nail penetration test but exhibits deteriorated battery performance.

(21) Although the preferred embodiments of the present invention have been disclosed for illustrative purposes, those skilled in the art will appreciate that various modifications, additions and substitutions are possible, without departing from the scope and spirit of the invention as disclosed in the accompanying claims.

INDUSTRIAL APPLICABILITY

(22) As described above, a compound particle according to the present invention may provide a cross-linked compound particle which has superior electrolyte solution impregnation and does not exhibit deteriorated battery characteristics, and a secondary battery including the same.