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Rechargeable lithium battery

a lithium battery, rechargeable technology, applied in the direction of non-aqueous electrolyte cells, cell components, electrochemical generators, etc., can solve the problems of significant deterioration of cycle characteristics, and achieve the effect of reducing hf generation and improving cycle characteristics

Inactive Publication Date: 2006-01-12
SAMSUNG SDI CO LTD
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Benefits of technology

[0008] An embodiment of the present invention provides a lithium secondary battery having high capacity as well as good cycle characteristics.
[0011] According to the above structure, a polyether modified silicone oil is added to an electrolyte. Since the polyether modified silicone oil is fused with a surface of Si particulate of a negative active material to form a protection layer, a decomposition reaction of the electrolyte with the Si particulate can be inhibited and thus cycle characteristics can be improved.
[0013] According to the above structure, since the polyether modified silicone oil is fused with the Si-phase of a negative active material to form a protection layer, decomposition reaction of the electrolyte on Si-phase can be inhibited and thus cycle characteristics can be improved.
[0020] Since an amount of LiPF6 in the lithium salt is less than or equal to 50 mol %, HF generation reaction between LiPF6 and Si particulate of the negative active material is inhibited and thus cycle characteristics of the lithium secondary battery can be improved.
[0022] The above electrolyte preferably includes at least one selected from the group consisting of Li(N(SO2C2F5)2), Li(N(SO2CF3)2), and LiBF4, as well as LiPF6 as a solute. They can prevent reaction between the Si particulate and LiPF6 and thus HF generation can be reduced to improve cycle characteristics.
[0024] The above electrolyte includes Li(N(SO2CF3)2) as well as LiPF6 as a solute and the Li(N(SO2CF3)2) can prevent reaction between the Si particulate and LiPF6. Therefore, HF generation is reduced so improving cycle characteristics.

Problems solved by technology

However, since Si particulate included in the composite material includes a functional group such as SiOH or Si=O on its surface, such functional groups contact the electrolyte and induce slow decomposition of the electrolyte resulting in significantly deteriorated cycle characteristics.

Method used

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  • Rechargeable lithium battery
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Examples

Experimental program
Comparison scheme
Effect test

experimental example 1

[0109] Lithium secondary battery cells including electrolytes having various additive components and their compositions were fabricated, and their cycle characteristics were estimated.

[0110] Battery cells were prepared as follows. Positive electrode slurry was prepared first by mixing a LiCoO2 positive active material having 10 μm average particle diameter, a binder of polyvinylidene fluoride, and a carbon powder conducting agent having 3 μm average particle diameter, and then by mixing with N-methyl-2-pyrrolidone. The positive electrode slurry was coated onto a current collector of 20 μm thick aluminum foil by doctor blade method, dried at 120° C. for 24 hours under vacuum atmosphere to volatilize N-methyl-2-pyrrolidone, and then pressed. An active mass including a positive active material was laminated with the current collector to fabricate a positive electrode.

[0111] Next, 2 parts by weight of Si particulate having 200 nm average particle diameter was mixed with 1 part by weig...

experimental example 2

[0127] A positive electrode and a negative electrode were fabricated using the same method as in Experimental Example 1.

[0128] Electrolytes of Examples 12 to 14 were prepared by adding 1.3M LiPF6 as a solute to a solvent of ethylenecarbonate (EC) and diethylcarbonate (DEC) mixed in a ratio of EC:DEC=30:70, and adding 5, 10, and 20 wt %, respectively, of silicone oil. The added silicone oil was the same as the silicone oil 2 of Experimental Example 1, where k=0, m=4, n=2, and R and Z=CH3 in the above formula 1.

[0129] Coin-type lithium secondary battery cells of Examples 12 to 14 were fabricated with the same method as in Experimental Example 1 using the positive electrode, negative electrode, and an electrolyte. Cycle characteristics of the obtained lithium secondary battery cells were estimated with the same method as in Experimental Example 1. The results are shown in FIG. 9. The electrolyte of the lithium secondary battery cell of Example 12 includes 5 wt % of silicone oil. The ...

experimental example 3

[0131] A positive electrode and a negative electrode were fabricated using the same method as in Experimental Example 1.

[0132] Electrolytes of Examples 15 to 17 were prepared by adding 1.3M LiPF6 as a solute to a solvent of ethylenecarbonate (EC) and diethylcarbonate (DEC) mixed in a ratio of EC:DEC=30:70, and adding 1 wt % of silicone oil.

[0133] The silicone oil of Example 15 was k=0, m=3, n=3, R and Z=CH3 in the structure of above formula 2. The silicone oil of Example 16 was k=0, m=3, n=6, R and Z=CH3 in the structure of above formula 3. The silicone oil of Example 17 was a silicone oil where k=0, m=3, n=4, and R and Z=CH3 in the above formula 3.

[0134] Coin-type lithium secondary battery cells of Examples 15 to 17 were fabricated using the same method as in Experimental Example 1 using the positive electrode, negative electrode, and an electrolyte. Cycle characteristics of the obtained lithium secondary battery cells were estimated with the same method as in Experimental Examp...

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Abstract

The present invention provides a lithium secondary battery having high-capacity as well as good cycle characteristics. The lithium secondary battery includes a positive electrode comprising a positive active material, a negative electrode comprising a negative active material and an electrolyte. The negative active material includes graphite particles combined to Si particulate. The electrolyte includes a solvent, a polyether modified silicone oil where a linear polyether chain is linked to a polysiloxane chain, and a solute comprising a lithium salt.

Description

CROSS-REFERENCE TO RELATED APPLICATION [0001] This application claims priorities to and the benefit of Japanese Application Nos. 2004-203292 and 2004-378253 filed with the Japanese Patent Office on Jul. 9, 2004 and Dec. 27, 2004, respectively, and Korean Patent Application No. 10-2005-0057680 filed with the Korean Intellectual Property Office on Jun. 30, 2005, the entire contents of which are incorporated herein by reference. FIELD OF THE INVENTION [0002] The present invention relates to a lithium secondary battery. More particularly, the present invention relates to a lithium secondary battery having high capacity and good cycle characteristics. BACKGROUND OF THE INVENTION [0003] As there is demand for a portable electronic device having a small size and light weight, as well as high performance characteristics, lithium secondary batteries having high capacity are needed. [0004] Graphite for a negative active material of a lithium secondary battery has a theoretical electrical capa...

Claims

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Application Information

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Patent Type & Authority Applications(United States)
IPC IPC(8): H01M10/40H01M4/58H01M4/133H01M4/134H01M4/587H01M10/052H01M10/0565H01M10/0567H01M10/0568H01M10/36
CPCH01M4/133H01M4/134H01M4/364H01M4/38H01M4/587H01M4/386H01M10/0565H01M10/0567H01M10/0568Y02E60/122H01M10/052Y02E60/10
Inventor YAMAGUCHI, TAKITAROSHIMIZU, RYUICHI
Owner SAMSUNG SDI CO LTD
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