KR20160002601A - Rechargeable lithium battery - Google Patents

Abstract

One embodiment of the present invention provides a lithium secondary battery that compensates for the irreversible region of the cathode to increase the initial efficiency of the cell, thereby increasing the capacity and energy density. A lithium secondary battery according to an embodiment of the present invention includes a positive electrode current collector having a positive electrode coating portion coated with a positive electrode active material and a positive electrode uncoated portion not coated with the positive electrode active material, A negative electrode coating portion and a negative electrode coating portion on which a negative electrode active material is not coated, the negative electrode coating portion including a negative electrode including a lithium source, a separator positioned between the positive electrode and the negative electrode, and an electrolyte, Wherein the lithium source is spaced apart from the end of the active region and located at the cathode.

Description

[0002] Lithium secondary batteries {RECHARGEABLE LITHIUM BATTERY}

The present invention relates to a lithium secondary battery, and more particularly, to a lithium secondary battery having a positive electrode coating portion and a negative electrode coating portion on a positive electrode and a negative electrode of an electrode group, respectively.

A lithium secondary battery, which has recently been spotlighted as a power source for portable electronic devices, has a discharge voltage twice as high as that of a conventional battery using an alkaline aqueous solution, resulting in high energy density.

The lithium secondary battery generally comprises a positive electrode, a negative electrode, a separator positioned between the positive electrode and the negative electrode, and an electrolyte, and the positive electrode and the negative electrode are composed of a current collector and an active material layer.

Examples of the positive electrode active material of the positive electrode include an oxide made of lithium and a transition metal having a structure capable of lithium intercalation such as LiCoO ₂ , LiMn ₂ O ₄ , LiNi _1-x Co _x O ₂ (0 <X <1) It is mainly used.

As the negative electrode active material for the negative electrode, various types of carbon-based materials including artificial graphite, natural graphite, and hard carbon capable of intercalating / deintercalating lithium are used. However, irreversible capacity occurs in the carbonaceous anode active material, lithium corresponding to the irreversible capacity of the diaphragm becomes insufficient at the anode, and the potential of the anode (Li / Li ⁺ ) increases. Such an increase in the positive electrode potential may lower the cycle life.

These problems arise because the initial discharge for the initial charging of the cathode is poor, that is, the initial discharge efficiency is not good. Such irreversible capacity generation and reduction of the initial discharge efficiency may occur when the thickness of the active material layer is increased, It can get worse.

As a method for increasing the initial discharge efficiency of a cathode, a lithium metal carrier film (LMCF) prepared by applying a stabilized lithium metal powder (SLMP) of FMC Co. or a stabilized lithium metal powder to a release film is applied to a cathode And then transferred to a roll.

One embodiment of the present invention provides a lithium secondary battery that compensates for the irreversible region of the cathode to increase the initial efficiency, thereby increasing the capacity and energy density.

A lithium secondary battery according to an embodiment of the present invention includes a positive electrode current collector having a positive electrode coating portion coated with a positive electrode active material and a positive electrode uncoated portion not coated with the positive electrode active material, A negative electrode coating portion and a negative electrode coating portion on which a negative electrode active material is not coated, the negative electrode coating portion including a negative electrode including a lithium source, a separator positioned between the positive electrode and the negative electrode, and an electrolyte, Wherein the lithium source is spaced apart from the end of the active region and located at the cathode.

The lithium source may be spaced apart from the end of the active region by an interval of 0.1 mm or more.

The lithium source may be spaced apart from the end of the active region by an interval of 0.1 mm to 10 cm.

The lithium source may be spaced apart from the negative electrode uncoated portion formed at the end of the active region.

The active region may be formed on both sides of the negative electrode current collector, and the lithium source may be located on both sides of the negative electrode uncoated portion.

The active region may be formed at both ends of the negative electrode current collector, and the lithium source may be spaced apart from the negative electrode uncoated portion at both ends of the negative electrode current collector.

The negative electrode coating portion may further include an inactive region connected to the active region and corresponding to the outside of the positive electrode coating portion.

The non-active region may be formed on both sides of the negative electrode current collector, and the lithium source may be formed on both surfaces of the negative electrode uncoated portion by being connected to the inactive region.

The inactive region may be formed on both sides of the cathode current collector, and the lithium source may be formed on one surface of the cathode uncoated portion connected to the inactive region.

The non-active region may be formed on both sides of the negative electrode current collector, and the lithium source may be located on at least one side of the inactive region at the interval.

As described above, the lithium secondary battery according to an embodiment of the present invention includes the lithium source in the negative electrode spaced apart from the end of the active region of the negative electrode coating portion to compensate the irreversible portion of the negative electrode not facing the positive electrode coating portion, Thereby increasing the initial efficiency of the battery. Therefore, the capacity and the energy density of the lithium secondary battery are increased.

1 is a perspective view of a lithium secondary battery according to a first embodiment of the present invention.
2 is an exploded perspective view of an electrode assembly and a pouch of a lithium secondary battery according to a first embodiment of the present invention.
FIG. 3 is a cross-sectional view illustrating a cathode and an anode by disassembling the electrode group of FIG. 2; FIG.
FIG. 4 is a cross-sectional view illustrating a cathode and an anode in a lithium secondary battery according to a second embodiment of the present invention in which an electrode group is disassembled.
FIG. 5 is a cross-sectional view illustrating a cathode and an anode in a lithium secondary battery according to a third embodiment of the present invention.
6 is a cross-sectional view illustrating a cathode and an anode in a lithium secondary battery according to a fourth embodiment of the present invention in which the electrode group is disassembled.
7 is a cross-sectional view of a lithium secondary battery of Comparative Example 1 in which an electrode group is decomposed to show a cathode and an anode.
FIG. 8 is a graph showing initial charging / discharging characteristics of a lithium secondary battery manufactured according to Examples 1 to 3 and Comparative Example 1. FIG.
9 is a photograph of the lithium secondary battery of Example 1 disassembled after charge and discharge.
10 is a photograph of a lithium secondary battery of Example 2 disassembled after charging and discharging.
11 is a photograph of a lithium secondary battery of Example 3 disassembled after charging and discharging.
12 is a photograph of a lithium secondary battery of Comparative Example 1 disassembled after charge and discharge.

Hereinafter, embodiments of the present invention will be described in detail. However, the present invention is not limited thereto, and the present invention is only defined by the scope of the following claims.

A lithium secondary battery according to an embodiment of the present invention includes a positive electrode current collector having a positive electrode coating portion coated with a positive electrode active material and a positive electrode uncoated portion not coated with the positive electrode active material, A negative electrode coating portion and a negative electrode coating portion on which a negative electrode active material is not coated, the negative electrode coating portion including a negative electrode including a lithium source, a separator positioned between the positive electrode and the negative electrode, and an electrolyte, Wherein the lithium source is spaced apart from the end of the active region and located at the cathode.

Hereinafter, the lithium secondary battery will be described in detail with reference to the drawings.

FIG. 1 is a perspective view of a lithium secondary battery according to a first embodiment of the present invention, and FIG. 2 is an exploded perspective view of an electrode assembly and a pouch of a lithium secondary battery according to a first embodiment of the present invention. Referring to FIGS. 1 and 2, the secondary battery of the first embodiment includes an electrode assembly 10 and a pouch 20 incorporating an electrode assembly 10.

The electrode group 10 is provided with a first electrode 11 (for convenience, an anode) and a second electrode 12 (for convenience, a cathode) 12 with a separator 13 interposed therebetween, It is made in the form of thin jelly roll. The separator 13 may be made of polyethylene, polypropylene, polyvinylidene fluoride or a multilayer film of two or more thereof. The separator may be a polyethylene / polypropylene double-layer separator, It is needless to say that a mixed multilayer film such as a polyethylene / polypropylene / polyethylene three-layer separator, a polypropylene / polyethylene / polypropylene three-layer separator and the like can be used.

The electrode group 10 includes a first lead tab 14a and a second lead tab 14b connected to positive and negative electrodes 11 and 12 for convenience (15). &Lt; / RTI &gt;

FIG. 3 is a cross-sectional view illustrating a cathode and an anode by disassembling the electrode group of FIG. 2; FIG. 3, the anode 11 includes a cathode coating portion 11a coated with a cathode active material on a cathode current collector, and a cathode uncoated portion 11b set as a cathode current collector exposed without applying a cathode active material . The current collector of the anode 11 may be Al, but is not limited thereto.

As the cathode active material, a compound capable of reversibly intercalating and deintercalating lithium (a lithiated intercalation compound) can be used. Concretely, at least one of complex oxides of metal and lithium selected from cobalt, manganese, nickel, and combinations thereof may be used. As a more specific example, a compound represented by any one of the following formulas may be used. Li _a A _1-b X _b D ₂ (0.90 ≤ a ≤ 1.8, 0 ≤ b ≤ 0.5), Li _a A _1-b X _b O _{2 -c} D _c (0.90 ≤ a ≤ 1.8, 0 ≤ b ≤ 0.5 , 0? C? 0.05); Li _a E _1-b X _b O _{2 -c} D _c (0? B? 0.5, 0? C? 0.05); Li _a E _2-b X _b O _{4 -c} D _c (0? B? 0.5, 0? C? 0.05); Li _a Ni _{1- b c} Co _b X _c D _? (0.90? A? 1.8, 0? B? 0.5, 0? C? 0.5, 0 <?? 2); Li _a Ni _{1- b c} Co _b X _c O _2-α T _α (0.90 ≤ a ≤ 1.8, 0 ≤ b ≤ 0.5, 0 ≤ c ≤ 0.05, 0 <α <2); Li _a Ni _{1- b c} Co _b X _c O _2-α T ₂ (0.90 ≤ a ≤ 1.8, 0 ≤ b ≤ 0.5, 0 ≤ c ≤ 0.05, 0 <α <2); Li _a Ni _1-bc Mn _b X _c D _? (0.90? A? 1.8, 0? B? 0.5, 0? C? 0.05, 0 <? Li _a Ni _1-bc Mn _b X _c O _2-α T _α (0.90 ≤ a ≤ 1.8, 0 ≤ b ≤ 0.5, 0 ≤ c ≤ 0.05, 0 <α <2); Li _a Ni _1-bc Mn _b X _c O _2-α T ₂ (0.90 ≤ a ≤ 1.8, 0 ≤ b ≤ 0.5, 0 ≤ c ≤ 0.05, 0 <α <2); Li _a Ni _b E _c G _d O ₂ (0.90? A? 1.8, 0? B? 0.9, 0? C? 0.5, 0.001? D? 0.1); Li _a Ni _b Co _c Mn _d G _e O ₂ (0.90 ≤ a ≤ 1.8, 0 ≤ b ≤ 0.9, 0 ≤ c ≤ 0.5, 0 ≤ d ≤ 0.5, 0.001 ≤ e ≤ 0.1); Li _a NiG _b O ₂ (0.90? A? 1.8, 0.001? B? 0.1); Li _a CoG _b O ₂ (0.90? A? 1.8, 0.001? B? 0.1); L _a Mn _1-b G _b O ₂ (0.90 ≤ a ≤ 1.8, 0.001 ≤ b ≤ 0.1); Li _a Mn ₂ G _b O ₄ (0.90 ≤ a ≤ 1.8, 0.001 ≤ b ≤ 0.1); Li _a Mn _1-g G _g PO ₄ (0.90? A? 1.8, 0? G? 0.5); QO ₂ QS ₂ LiQS ₂ V ₂ O ₅ LiV ₂ O ₅ LiZO ₂ LiNiVO ₄ Li _(3-f) J ₂ (PO ₄ ) ₃ (0? F? 2); Li _(3-f) Fe ₂ (PO ₄ ) ₃ (0? _F ? 2); Li _a FePO ₄ (0.90? A? 1.8)

In the above formula, A is selected from the group consisting of Ni, Co, Mn, and combinations thereof; X is selected from the group consisting of Al, Ni, Co, Mn, Cr, Fe, Mg, Sr, V, rare earth elements and combinations thereof; D is selected from the group consisting of O, F, S, P, and combinations thereof; E is selected from the group consisting of Co, Mn, and combinations thereof; T is selected from the group consisting of F, S, P, and combinations thereof; G is selected from the group consisting of Al, Cr, Mn, Fe, Mg, La, Ce, Sr, V, and combinations thereof; Q is selected from the group consisting of Ti, Mo, Mn, and combinations thereof; Z is selected from the group consisting of Cr, V, Fe, Sc, Y, and combinations thereof; J is selected from the group consisting of V, Cr, Mn, Co, Ni, Cu, and combinations thereof.

Of course, a compound having a coating layer on the surface of the compound may be used, or a compound having a coating layer may be mixed with the compound. The coating layer comprises at least one coating element compound selected from the group consisting of an oxide of the coating element, a hydroxide of the coating element, an oxyhydroxide of the coating element, an oxycarbonate of the coating element and a hydroxycarbonate of the coating element . The compound constituting these coating layers may be amorphous or crystalline. The coating layer may contain Mg, Al, Co, K, Na, Ca, Si, Ti, V, Sn, Ge, Ga, B, As, Zr or a mixture thereof. The coating layer forming step may be any coating method as long as it can coat the above compound by a method which does not adversely affect the physical properties of the cathode active material (for example, spray coating, dipping, etc.) by using these elements, It will be understood by those skilled in the art that a detailed description will be omitted.

The content of the cathode active material in the cathode active material layer may be 90% by weight to 98% by weight based on the total weight of the cathode active material layer.

The cathode active material layer also includes a binder and a conductive material. At this time, the content of the binder and the conductive material may be 1 wt% to 5 wt% with respect to the total weight of the cathode active material layer.

The binder serves to adhere the positive electrode active material particles to each other and to adhere the positive electrode active material to the current collector. Typical examples thereof include polyvinyl alcohol, carboxymethyl cellulose, hydroxypropyl cellulose, diacetyl cellulose, polyvinyl Polyvinylpyrrolidone, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, styrene-acrylonitrile, styrene-butadiene rubber, Butadiene rubber, acrylated styrene-butadiene rubber, epoxy resin, nylon, and the like, but not limited thereto.

The conductive material is used for imparting conductivity to the electrode. Any conductive material can be used without causing any chemical change in the battery. Examples of the conductive material include natural graphite, artificial graphite, carbon black, acetylene black, Carbon materials such as black, carbon fiber and the like, metal powders such as nickel, aluminum, and silver, or metal-based materials such as metal fibers, or conductive polymers such as polyphenylene derivatives or mixtures thereof.

The negative electrode 12 includes a negative electrode coating portion 12a coated with a negative electrode active material on a negative electrode current collector and a negative electrode uncoated portion 12b configured as a negative electrode current collector exposed without applying a negative electrode active material. The current collector of the cathode 12 may be formed of a copper foil, a nickel foil, a stainless steel foil, a titanium foil, a nickel foam, a copper foil, a polymer substrate coated with a conductive metal, Can be used.

The negative electrode active material includes a material capable of reversibly intercalating / deintercalating lithium ions, a lithium metal, an alloy of lithium metal, a material capable of doping and dedoping lithium, or a transition metal oxide.

As a material capable of reversibly intercalating / deintercalating lithium ions, any carbonaceous anode active material commonly used in lithium ion secondary batteries can be used as the carbonaceous material. Typical examples thereof include crystalline carbon , Amorphous carbon, or a combination thereof. Examples of the crystalline carbon include graphite such as natural graphite or artificial graphite in the form of amorphous, plate-like, flake, spherical or fibrous type. Examples of the amorphous carbon include soft carbon or hard carbon hard carbon, mesophase pitch carbide, fired coke, and the like.

As the lithium metal alloy, a lithium-metal alloy may be selected from the group consisting of lithium, Na, K, Rb, Cs, Fr, Be, Mg, Ca, Sr, Si, Sb, Pb, In, Zn, Ba, An alloy of a selected metal may be used.

As the material capable of being doped and dedoped into lithium, Si, Si-C composite, SiO _x (0 <x <2), Si-Q alloy (Q is an alkali metal, an alkaline earth metal, a Group 13 element, Sn, SnO ₂ , Sn-R (wherein R is an alkali metal, an alkali earth metal, an element selected from the group consisting of Group 15 elements, Group 16 elements, transition metals, rare earth elements and combinations thereof) An element selected from the group consisting of Group IV elements, Group 14 elements, Group 15 elements, Group 16 elements, transition metals, rare earth elements and combinations thereof, and is not Sn). ₂ may be mixed and used. The element Q and the element R may be at least one element selected from the group consisting of Mg, Ca, Sr, Ba, Ra, Sc, Y, Ti, Zr, Hf, Rf, V, Nb, Ta, Db, Cr, Mo, W, Sg, Pb, Pt, Cu, Ag, Au, Zn, Cd, B, Al, Ga, Sn, In, Tl, Ge, P, As, Sb, Bi, S, Se, Te, Po, and combinations thereof.

Examples of the transition metal oxide include vanadium oxide, lithium vanadium oxide, and lithium titanium oxide.

The content of the negative electrode active material in the negative electrode active material layer may be 95 wt% to 99 wt% with respect to the total weight of the negative electrode active material layer.

The negative electrode active material layer also includes a binder, and may optionally further include a conductive material. The content of the binder in the negative electrode active material layer may be 1 wt% to 5 wt% with respect to the total weight of the negative electrode active material layer. When the conductive material is further included, the negative electrode active material may be used in an amount of 90 to 98 wt%, the binder may be used in an amount of 1 to 5 wt%, and the conductive material may be used in an amount of 1 to 5 wt%.

The binder serves to adhere the anode active material particles to each other and to adhere the anode active material to the current collector. As the binder, a water-insoluble binder, a water-soluble binder, or a combination thereof may be used.

Examples of the water-insoluble binder include polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, a polymer containing ethylene oxide, polyvinyl pyrrolidone, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride , Polyethylene, polypropylene, polyamideimide, polyimide, or a combination thereof.

The water-soluble binder means a binder in which water is used as a solvent or a dispersion medium. Since such an aqueous binder uses water as a solvent or a dispersion medium, it is not necessary to use an organic solvent having high toxicity such as N-methylpyrrolidone. Therefore, the active material composition containing the aqueous binder is harmless to the human body and environmentally friendly.

The water-based binder may be the rubber-based binder or the polymeric resin binder. The rubber binder may be selected from styrene-butadiene rubber, acrylated styrene-butadiene rubber (SBR), acrylonitrile-butadiene rubber, acrylic rubber, butyl rubber, fluorine rubber and combinations thereof. The polymeric resin binder may be selected from the group consisting of polytetrafluoroethylene, polyethylene, polypropylene, ethylene propylene copolymer, polyethylene oxide, polyvinylpyrrolidone, polyepichlorohydrin, polyphosphazene, polyacrylonitrile, polystyrene, Polyvinyl pyrrolidone, ethylene propylene diene copolymer, polyvinyl pyridine, chlorosulfonated polyethylene, latex, polyester resin, acrylic resin, phenol resin, epoxy resin, polyvinyl alcohol, and combinations thereof.

When an aqueous binder is used as the negative electrode binder, it may further include a cellulose-based compound capable of imparting viscosity. As the cellulose-based compound, carboxymethyl cellulose, hydroxypropylmethyl cellulose, methyl cellulose, alkali metal salts thereof or the like may be used in combination. As the alkali metal, Na, K or Li can be used. The content of the thickener may be 0.1 part by weight to 3 parts by weight based on 100 parts by weight of the binder.

The conductive material is used for imparting conductivity to the electrode. Any conductive material can be used without causing any chemical change in the battery. Examples of the conductive material include natural graphite, artificial graphite, carbon black, acetylene black, Carbon materials such as black, carbon fiber and the like, metal powders such as nickel, aluminum, and silver, or metal-based materials such as metal fibers, or conductive polymers such as polyphenylene derivatives or mixtures thereof.

The positive and negative electrode uncoated portions 11b and 12b are formed in such a manner that when the positive and negative electrodes 11 and 12 are wound, the amount to be wound, the winding end in the longitudinal direction of the cathodes 11 and 12, And may be provided at the end. As an example, the positive electrode uncoated portion 11b is provided at both ends of the winding, and the negative electrode uncoated portion 12b is provided at both ends of the winding. Although not shown, the anode uncoated portion may be provided at the winding end and may be provided at the winding uncoiled portion winding end.

1 and 2, the positive electrode lead tab 14 is connected to the positive electrode uncoated portion 11b and the negative electrode lead tab 15 is spaced apart from the positive electrode lead tab 14 and connected to the negative electrode uncoated portion 12b .

The positive electrode lead tab 14 and the negative electrode lead tab 15 are drawn out to the same side of the electrode group 10 and are respectively disposed. Although not shown, the positive electrode lead tabs and the negative electrode lead tabs may be disposed on opposite sides (left and right sides in Figs. 1 and 2) of the electrode groups, respectively.

The pouch 20 accommodates the electrode group 10 and thermally fuses the outer portion thereof to form a lithium secondary battery. At this time, the positive electrode lead tab 14 and the negative electrode lead tab 15 are covered with the tap insulating members 16 and 17, and are drawn out of the pouch 20 through the fused portion. That is, the tab insulating members 16 and 17 electrically insulate the positive and negative lead tabs 14 and 15 and electrically insulate the positive and negative lead tabs 14 and 15 from the pouch 20.

The pouch 20 may be formed in a multi-layered sheet structure that surrounds the outside of the electrode assembly 10. For example, the pouch 20 includes a polymer sheet 21 forming an inner surface and insulating and thermally fusing, a polyethyleneterephthalate (PET) sheet, a nylon sheet, or a PET-nylon composite sheet (Hereinafter referred to as "nylon sheet" for convenience), and a metal sheet 23 that provides mechanical strength. The metal sheet 23 is interposed between the polymer sheet 21 and the nylon sheet 22 and can be formed of an aluminum sheet as an example.

The pouch 20 includes a first casing member 201 that accommodates the electrode assembly 10 and a second casing member 202 that covers the electrode assembly 10 and is thermally welded to the first casing member 201 from the outside of the electrode assembly 10 ). The first and second outer casings 201 and 202 may be formed of a polymer sheet 21, a nylon sheet 22 and a metal sheet 23 having the same layer structure.

For example, the first casing member 201 is formed in a concave structure so as to receive the electrode assembly 10, and the second casing member 202 is flattened so as to cover the electrode assembly 10 housed in the first casing member 201. [ Respectively. Although not shown, the second exterior material may be connected to the first exterior material.

Further, the electrode group 10 is formed into a substantially rectangular parallelepiped flat plate structure, whereby the pouch 20 forms an outer appearance with a rectangular parallelepiped flat plate structure. Since the secondary battery is formed by surrounding the electrode assembly 10 with the pouch 20, a planar structure of a rectangular parallelepiped can be formed as a whole.

Referring again to FIG. 3, the cathode coating portion 12a includes an active region AA corresponding to the anode coating portion 11a. The negative electrode 12 further includes a lithium source 12c in the negative electrode 12 not facing the positive electrode coating portion 11a. The lithium source 12c is located on the cathode 12 at a predetermined gap G from the end of the active region AA. That is, the lithium source 12c faces the positive electrode uncoated portion 11b.

The lithium source may be lithium metal, lithiated silicon, lithiated Ge, or a combination thereof. Alternatively, a lithiated metal form may be used in addition to the materials described above as a lithium source.

When the lithium source 12c is located in the active region AA of the anode coating portion 11a facing the anode coating portion 11a, there is a possibility that the lithium source is precipitated. 11a of the cathode 12 and the active region AA of the cathode 12 not facing.

That is, the lithium source 12c is provided on the negative electrode 12 which does not face the positive electrode coating portion 11a and is attached with a lithium source, so that the initial efficiency of the lithium secondary battery can be increased. Therefore, the lithium secondary battery can increase the capacity and the energy density through the initial efficiency increase.

For example, the lithium source 12c may be spaced apart from the end of the active region AA by an interval G of 0.1 mm or more. The lithium source 12c may be spaced apart from the end of the active region AA by an interval G of 0.1 mm to 10 cm. In an embodiment of the present invention, the lithium source 12c may be spaced apart from the end of the active region AA by an interval G of 2 mm to 10 mm. When the spacing distance is included in the above range, the initial charge / discharge characteristics can be further improved.

The lithium source 12c may be spaced apart from the negative electrode uncoated region 12b formed at the end of the active region AA by an interval G. [ In this case, the lithium source 12c increases the initial efficiency, thereby increasing the capacity and the energy density, and the gap G prevents the lithium source from being precipitated between the active region AA and the negative electrode uncoated portion 12b do.

The active area AA may be formed on both sides of the cathode current collector. At this time, the lithium source 12c may be formed on both surfaces of the cathode uncoated portion 12b. In this case, the lithium source 12c increases the initial efficiency on both sides of the negative electrode uncoated portion 12b, and the gap G between the active area AA and the negative electrode uncoated portion 12b on both sides of the negative electrode uncoated portion 12b. To prevent precipitation of lithium.

Further, the active region AA may be formed at both ends of the cathode current collector. At this time, the lithium source 12c may be spaced apart from the cathode uncooled portion 12b at both ends of the cathode current collector by an interval G. In this case, the lithium source 12c raises the initial efficiency at both ends of the negative electrode current collector, and the interval G is set between the active region AA and the negative electrode uncoated portion 12b at both ends of the negative electrode current collector, Precipitation can be prevented.

The electrolyte includes a non-aqueous organic solvent and a lithium salt.

The non-aqueous organic solvent serves as a medium through which ions involved in the electrochemical reaction of the battery can move.

As the non-aqueous organic solvent, a carbonate-based, ester-based, ether-based, ketone-based, alcohol-based, or aprotic solvent may be used. Examples of the carbonate solvent include dimethyl carbonate (DMC), diethyl carbonate (DEC), dipropyl carbonate (DPC), methyl propyl carbonate (MPC), ethyl propyl carbonate (EPC), methyl ethyl carbonate (MEC) EC), propylene carbonate (PC), and butylene carbonate (BC) may be used. As the ester solvent, methyl acetate, ethyl acetate, n-propyl acetate, dimethyl acetate, methyl propionate, ethyl propionate , gamma -butyrolactone, decanolide, valerolactone, mevalonolactone, caprolactone, and the like can be used. Examples of the ether solvent include dibutyl ether, tetraglyme, diglyme, dimethoxyethane, 2-methyltetrahydrofuran, tetrahydrofuran and the like. As the ketone-based solvent, cyclohexanone and the like can be used. As the alcoholic solvent, ethyl alcohol, isopropyl alcohol and the like can be used. As the non-protonic solvent, R-CN (R is a linear, branched or cyclic hydrocarbon group having 2 to 20 carbon atoms, A double bond aromatic ring or an ether bond), amides such as dimethylformamide, dioxolanes such as 1,3-dioxolane, and sulfolanes.

The non-aqueous organic solvent may be used alone or in admixture of one or more. If the non-aqueous organic solvent is used in combination, the mixing ratio may be appropriately adjusted according to the desired cell performance. .

In the case of the carbonate-based solvent, it is preferable to use a mixture of a cyclic carbonate and a chain carbonate. In this case, when the cyclic carbonate and the chain carbonate are mixed in a volume ratio of 1: 1 to 1: 9, the performance of the electrolytic solution may be excellent.

The non-aqueous organic solvent may further include an aromatic hydrocarbon-based organic solvent in the carbonate-based solvent. In this case, the carbonate-based solvent and the aromatic hydrocarbon-based organic solvent may be mixed in a volume ratio of 1: 1 to 30: 1.

The aromatic hydrocarbon-based organic solvent may be an aromatic hydrocarbon-based compound represented by the following formula (1).

[Chemical Formula 1]

Wherein R ₁ to R ₆ are the same or different from each other and selected from the group consisting of hydrogen, halogen, an alkyl group having 1 to 10 carbon atoms, a haloalkyl group, and combinations thereof.

Specific examples of the aromatic hydrocarbon-based organic solvent include benzene, fluorobenzene, 1,2-difluorobenzene, 1,3-difluorobenzene, 1,4-difluorobenzene, 1,2,3-tri Fluorobenzene, 1,2,4-trifluorobenzene, 1,2-dichlorobenzene, 1,3-dichlorobenzene, 1,4-dichlorobenzene, 1,2,3-trichlorobenzene, 1 , 2,4-trichlorobenzene, iodobenzene, 1,2-diiodobenzene, 1,3-diiodobenzene, 1,4-diiodobenzene, 1,2,3-triiodobenzene, Examples of the solvent include 2,4-triiodobenzene, toluene, fluorotoluene, 2,3-difluorotoluene, 2,4-difluorotoluene, 2,5-difluorotoluene, 2,3,4- Dichlorotoluene, 2,3-dichlorotoluene, 2,5-dichlorotoluene, 2,3,4-trichlorotoluene, 2, 3-trifluorotoluene, 3,5-trichlorotoluene, iodotoluene, 2,3-diiodotoluene, 2,4-diiodotoluene, 2 , 5-diiodotoluene, 2,3,4-triiodotoluene, 2,3,5-triiodotoluene, xylene, and combinations thereof.

The non-aqueous electrolyte may further include vinylene carbonate or an ethylene carbonate-based compound represented by the following formula (2) to improve battery life.

(2)

(Wherein R ₇ and R ₈ are the same or different and are selected from the group consisting of hydrogen, a halogen group, a cyano group (CN), a nitro group (NO ₂ ) and an alkyl group having 1 to 5 fluorinated carbon atoms , At least one of R ₇ and R ₈ is selected from the group consisting of a halogen group, a cyano group (CN), a nitro group (NO ₂ ) and an alkyl group having 1 to 5 fluorinated carbon atoms, provided that R ₇ and R ₈ are both It is not hydrogen.)

Representative examples of the ethylene carbonate-based compound include diethylene carbonate, diethylene carbonate, dibromoethylene carbonate, nitroethylene carbonate, cyanoethylene carbonate, fluoroethylene carbonate, and the like, such as difluoroethylene carbonate, chloroethylene carbonate, dichloroethylene carbonate, . When such a life improving additive is further used, its amount can be appropriately adjusted.

The lithium salt is dissolved in an organic solvent to act as a source of lithium ions in the cell to enable operation of a basic lithium secondary battery and to promote the movement of lithium ions between the anode and the cathode. The lithium salt Representative examples are _{LiPF 6, LiBF 4, LiSbF 6} , LiAsF 6, LiN (SO 2 C 2 F 5) 2, Li (CF 3 SO 2) 2 N, LiN (SO 3 C 2 F 5) 2, _{LiC 4 F 9 SO 3, LiClO} 4, LiAlO 2, LiAlCl 4, LiN (C x F 2x + 1 SO 2) (C y F 2y + 1 SO 2) ( where x and y are natural numbers from 1 to 20 ), LiCl, LiI and LiB (C ₂ O ₄ ) ₂ (lithiumbis (oxalato) borate (LiBOB)) as a supporting electrolyte salt. The concentration of the lithium salt is preferably within the range of 0.1 to 2.0 M. When the concentration of the lithium salt is within the above range, the electrolyte has an appropriate conductivity and viscosity, and therefore can exhibit excellent electrolyte performance, .

The lithium secondary battery can be classified into a lithium ion battery, a lithium ion polymer battery, and a lithium polymer battery depending on the type of the separator and electrolyte used. The lithium secondary battery can be classified into a cylindrical shape, a square shape, a coin shape, Depending on the size, it can be divided into bulk type and thin type. The structure and the manufacturing method of these cells are well known in the art, and detailed description thereof will be omitted.

Hereinafter, various embodiments of the present invention will be described. The description of the same constitution as the constitution of the first embodiment and the previously described embodiment will be omitted and the different constitution will be described.

FIG. 4 is a cross-sectional view illustrating a cathode and an anode in a lithium secondary battery according to a second embodiment of the present invention in which an electrode group is disassembled. Referring to FIG. 4, in the electrode group 210 of the lithium secondary battery of the second embodiment, the anode coating portion 212a is connected to the active region AA and the active region AA to correspond to only the anode coating portion 11a And an inactive region (IA).

The active region AA is formed on both sides of the cathode current collector and the inactive region IA is formed in connection with the active region AA on both sides of the cathode current collector. The lithium source 212c is connected to the inactive region IA and is formed on both sides of the cathode uncoated region 212b.

At this time, the interval G2 set from the end of the active area AA is set to the range of the inactive area IA. That is, the lithium source 212c increases the initial efficiency on both sides of the cathode uncoated portion 212b, and the gap G2 increases the lithium efficiency of the lithium ion battery 212b between the active region AA and the inactive region IA on both sides of the cathode non- .

In the electrode group 210 of the second embodiment, the lithium source 212c is formed on both surfaces of the cathode uncoated portion 212b at one end of the cathode current collector. Although not shown, the lithium source may be formed on both surfaces of the negative electrode uncoated portion at one end of the negative electrode current collector.

FIG. 5 is a cross-sectional view illustrating a cathode and an anode in a lithium secondary battery according to a third embodiment of the present invention. 5, in the electrode group 310 of the lithium secondary battery of the third embodiment, the active area AA of the cathode coating 312a is formed on both sides of the cathode current collector, and the inactive area IA is And is connected to the active region AA on both sides of the cathode current collector.

The lithium source 212c is connected to the inactive region IA and is formed on one surface of the cathode uncoated portion 212b. At this time, the interval G3 set from the end of the active area AA is set to the range of the inactive area IA. That is, the lithium source 312c increases the initial efficiency at one surface of the negative electrode uncoated portion 312b, and the interval G3 increases the lithium ion concentration between the active region AA and the inactive region IA on one surface of the negative electrode uncoated portion 312b. Can be prevented.

In the electrode group 310 of the third embodiment, the lithium source 312c is formed on the outer surface of the negative electrode uncoated portion 312b. Although not shown, the lithium source may be formed on the inner surface of the negative electrode uncoated portion.

6 is a cross-sectional view illustrating a cathode and an anode in a lithium secondary battery according to a fourth embodiment of the present invention in which the electrode group is disassembled. Referring to FIG. 6, in the electrode group 410 of the lithium secondary battery of the fourth embodiment, the inactive region IA of the cathode coating portion 412a is formed on both surfaces of the cathode current collector. Therefore, the negative electrode uncoated region 412b is set outside the inactive region IA.

The lithium source 412c is formed on at least one surface of the inactive region IA and is spaced apart from the active region AA by an interval G4. That is, the lithium source 412c increases the initial efficiency on one side of the inactive region IA, and the gap G4 is a distance between the active region AA and the inactive region IA on one side of the inactive region IA. Prevent precipitation.

In the electrode group 410 of the fourth embodiment, the lithium source 412c is formed on both surfaces of the inactive region IA at one end of the cathode current collector. Although not shown, the lithium source may be formed on both sides of the inactive region at one end of the cathode current collector or at one or both sides of the inactive region at both ends.

Hereinafter, preferred embodiments and comparative examples of the present invention will be described. However, the following examples are merely preferred embodiments of the present invention, and the present invention is not limited by the following examples.

(Example 1)

94 wt% of LiCoO ₂ cathode active material, 3 wt% of Super P conductive material and 3 wt% of polyvinylidene fluoride binder were mixed in N-methylpyrrolidone solvent to prepare a cathode active material slurry.

The positive electrode active material slurry was coated on the Al foil current collector except for one end (the uncoated portion was referred to as an ignition portion) and dried to prepare a positive electrode including a positive electrode uncoated portion and a positive electrode coated portion.

A negative electrode active material slurry was prepared by mixing 90% by weight of a graphite negative electrode active material and 10% by weight of a polyvinylidene fluoride binder in N-methylpyrrolidone. The negative electrode active material slurry was coated and dried except for one end of the Cu foil current collector (both uncoated portions were coated with an uncoated portion) to prepare a negative electrode having a negative electrode coating portion and a negative electrode coating portion. At this time, the anode coating portion is composed of the active region corresponding to the anode coating portion and the inactive region corresponding to the non-coated portion. On one surface of the inactive region, which is not in direct contact with the separator, A lithium metal foil was attached at an interval of 3 mm to prepare a negative electrode having the structure shown in Fig.

The positive electrode and the negative electrode were used, and a polyethylene polymer separator was placed between the transfer pole and the negative electrode to take up an electrode group.

A lithium secondary battery was prepared by using a mixed solvent of ethylene carbonate and ethyl methyl carbonate (1: 1 by volume) electrolytic solution in which the electrode group and 1M LiPF ₆ were dissolved.

(Example 2)

The lithium metal foil was attached to one surface of the inactive region which was not in direct contact with the separator at a distance of 5 mm from the end of the active region to produce a negative electrode having the structure shown in Fig. 6, Thereby preparing a lithium secondary battery.

(Example 3)

The same procedure as in Example 1 was carried out except that the lithium metal foil was attached to one surface of the inactive region not in direct contact with the separator at a distance of 10 mm from the end of the active region, Thereby preparing a lithium secondary battery.

(Comparative Example 1)

A lithium metal foil was attached to one surface of the inactive region not in direct contact with the separator to produce a negative electrode having the structure shown in Fig. That is, the lithium metal foil (413c in FIG. 7) is located in the entire inactive region which is not spaced from the end of the active region.

The lithium secondary batteries prepared in Examples 1 to 3 and Comparative Example 1 were charged and discharged at 0.1 C to measure initial charging / discharging characteristics, and the results are shown in FIG.

As shown in Fig. 8, the initial charge-discharge characteristics of the lithium secondary batteries of Examples 1 to 3 in which the lithium metal foil was attached to the negative electrode at intervals of 3 mm, 5 mm, and 10 mm from the ends of the active region, Which is superior to the lithium secondary battery of Comparative Example 1, which is not used.

9 shows a photograph of the disassembly of the lithium secondary battery of Example 1 after charging and discharging, FIG. 10 shows a photograph of the disassembled lithium secondary battery of Example 2, and FIG. 10 shows a photograph of the disassembled lithium secondary battery of Example 3 The photographs are shown in Fig. FIG. 12 shows a photograph of the disassembly of the lithium secondary battery of Comparative Example 1 after charging and discharging, and FIG. 12 shows the case where the lithium metal is not used (ref.) For comparison. As shown in FIGS. 9 to 11, the lithium secondary batteries of Examples 1 to 3 are clear because the surface is clean, and lithium precipitation does not occur. However, in the case of Comparative Example 1 shown in FIG. 12 (with Li metal) , Ref., White powder is generated on the surface, that is, lithium precipitation occurs.

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it is to be understood that the invention is not limited to the disclosed exemplary embodiments, and that various changes and modifications may be made therein without departing from the scope of the appended claims, And it goes without saying that the invention belongs to the scope of the invention.

10, 210, 310, 410: electrode group 11: first electrode (anode)
11a: anode coating part 11b: anode coating part
12: Second electrode (cathode) 12a, 212a, 312a, 412a: cathode coating
12b, 212b, 312b, 412b: cathode uncoated portions 12c, 212c, 312c, 412c:
13: separator 14: first lead tab (positive lead tab)
15: second lead tab (negative electrode lead tab) 16, 17:
20: Pouch 21: Polymer sheet
22: nylon sheet 23: metal sheet
201: first exterior material 202: second exterior material
AA: active region IA: inactive region
G, G2, G3, G4: Interval

Claims (10)

A positive electrode including a positive electrode coating portion in which a positive electrode current collector is coated with a positive electrode active material and a positive electrode uncoated portion in which a positive electrode active material is not coated;
A negative electrode coating part including a negative electrode current collector coated with a negative electrode active material and a negative electrode uncoated part not coated with the negative electrode active material, the negative electrode including a lithium source;
A separator positioned between the anode and the cathode; And
Electrolyte
/ RTI &gt;
The negative electrode coating portion
And an active region corresponding to the anode coating portion,
The lithium source
Wherein the active region is spaced apart from the end of the active region at a predetermined interval and is located in the negative electrode. The method according to claim 1,
The lithium source
Wherein the active region is spaced apart from the end of the active region by 0.1 mm or more. The method according to claim 1,
The lithium source is a lithium-
And is spaced apart from the end of the active region by an interval of 0.1 mm to 10 cm. The method according to claim 1,
The lithium source is a lithium-
And is spaced apart from the negative electrode uncoated portion formed at an end of the active region. 5. The method of claim 4,
Wherein the active region is formed on both sides of the cathode current collector,
Wherein the lithium source is formed on both surfaces of the negative electrode uncoated portion. 5. The method of claim 4,
Wherein the active region is formed at both ends of the negative electrode current collector,
Wherein the lithium source is located at the negative electrode nonconductive portions at both ends of the negative electrode current collector at intervals. The method according to claim 1,
The negative electrode coating portion
And a non-active region connected to the active region and corresponding to outside the positive electrode coating portion. 8. The method of claim 7,
Wherein the inactive region is formed on both sides of the cathode current collector,
Wherein the lithium source is connected to the inactive region and formed on both surfaces of the negative electrode uncoated portion. 8. The method of claim 7,
Wherein the inactive region is formed on both sides of the cathode current collector,
Wherein the lithium source is connected to the inactive region and is formed on one surface of the uncoated cathode. 8. The method of claim 7,
Wherein the inactive region is formed on both sides of the cathode current collector,
Wherein the lithium source is located on at least one side of the inactive region at the intervals.

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