KR101914746B1 - Cylindrical Battery Including Pressuring Part and Manufacturing Method for the Same - Google Patents

Abstract

The present invention relates to an electrode assembly (jelly-roll) comprising a cathode, a separator, and a cathode; A cylindrical can including a housing portion in which the electrode assembly and the electrolyte solution are housed together; A cap assembly mounted on an open upper end of the cylindrical can; A safety vent built in the cap assembly and having a notch formed therein to rupture by the pressure of gas existing in the cylindrical battery; And a pressurizing portion located between the safety vent and the accommodating portion and communicating with the accommodating portion and applying a predetermined pressure to the accommodating portion by gas, wherein the positive electrode includes a lithium composite material represented by the following Formula 1 The present invention relates to a cylindrical battery including a transition metal oxide, the life characteristic of which is remarkably increased.
Li _{1 + a} Ni _b M _c Mn _{2 - (b + c)} O _{4 - z} (1)
Wherein M is one or more selected from the group consisting of Ti, Co, Al, Cu, Fe, Mg, B, Cr, Zr, Zn and two period transition metals, and 0? A? 0.1, 0.5, 0? C? 0.1, 0? Z? 0.1.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to a cylindrical battery including a pressing portion,

The present invention relates to a cylindrical battery including a pressing portion and a method of manufacturing the same.

Due to the rapid increase in the use of fossil fuels, the demand for the use of alternative energy or clean energy is increasing. As a part of this, the most active field of research is electric power generation and storage.

At present, a typical example of an electrochemical device utilizing such electrochemical energy is a secondary battery, and the use area thereof is gradually increasing.

The secondary battery is classified into a cylindrical battery and a prismatic battery in which the electrode assembly is housed in a cylindrical or rectangular metal can according to the shape of the battery case, and a pouch-shaped battery in which the electrode assembly is housed in a pouch-shaped case of an aluminum laminate sheet . Among them, the cylindrical battery has a relatively large capacity and is structurally stable.

In addition, the electrode assembly incorporated in the battery case is a charge / dischargeable power generation device composed of a laminate structure of a positive electrode / separator / negative electrode. The electrode assembly is composed of a jelly-roll type battery having a separator interposed between a positive electrode and a negative electrode coated with an active material, , And a plurality of positive electrodes and negative electrodes of a predetermined size are sequentially stacked in a state in which the separator is interposed therebetween. Among them, the jelly-roll type electrode assembly has an advantage of being easy to manufacture and having a high energy density per weight.

On the other hand, in lithium secondary batteries, lithium-containing cobalt oxide (LiCoO ₂ ) is mainly used as a cathode active material, and lithium-containing manganese oxides such as LiMnO _{2 having a} layered crystal structure and LiMn ₂ O _{4 having a} spinel crystal structure, Lithium-containing nickel oxide (LiNiO ₂ ) is also used.

Among the above cathode active materials, LiCoO ₂ has excellent properties such as excellent cycle characteristics and is widely used at present, but its safety is low and there is a problem that it is expensive due to the resource limit of cobalt as a raw material. Lithium nickel oxide such as LiNiO ₂ exhibits a high discharge capacity when charged at 4.25 V at a lower cost than LiCoO ₂ , but has a high production cost, swelling due to gas generation in the battery, low chemical stability, high pH And so on.

In addition, lithium manganese oxides such as LiMnO ₂ and LiMn ₂ O ₄ have the advantage of using manganese which is rich in resources and environment-friendly as a raw material, and thus attracts much attention as a cathode active material that can replace LiCoO ₂ . Particularly, LiMn ₂ O ₄ has advantages such as relatively low cost and high output, but has a disadvantage that energy density is lower than LiCoO ₂ and ternary active materials.

In order to overcome this disadvantage, replacing a part of Mn with Ni in LiMn ₂ O ₄ has a higher operating potential (about 4.7 V) than the original operating potential (about 4 V). Spinel materials having a composition of Li _{1 + a} Ni _x Mn _{2 - x} O _{4 -z} (0? A? 0.1, 0.4? X? 0.5, 0? Z? 0.1) have high energy and high output It is a material highly likely to be used as a cathode active material for medium and large-sized lithium ion batteries including electric vehicles (EV) which require high performance. However, due to the high charging / discharging voltage potential, dissolution of Mn of the cathode active material and deterioration of battery lifetime due to electrolyte side reaction are problematic.

Therefore, there is a high need for a technique capable of improving the lifetime characteristics of a battery while using a positive electrode active material containing a high Mn content as described above.

SUMMARY OF THE INVENTION It is an object of the present invention to solve the above-mentioned problems of the prior art and the technical problems required from the past.

The inventors of the present application have conducted intensive research and various experiments and have found that a cylindrical secondary battery using a cathode active material containing a high Mn content is provided between a safety vent and a storage portion, The present invention has been accomplished on the basis of confirming that an unexpectedly excellent effect can be achieved when a pressurizing portion for applying a predetermined pressure is included.

Accordingly, a cylindrical battery according to the present invention includes: an electrode assembly (jelly-roll) including a cathode, a separator, and a cathode; A cylindrical can including a housing portion in which the electrode assembly and the electrolyte solution are housed together; A cap assembly mounted on an open upper end of the cylindrical can; A safety vent built in the cap assembly and having a notch formed therein to rupture by the pressure of gas existing in the cylindrical battery; And a pressurizing portion located between the safety vent and the accommodating portion and communicating with the accommodating portion and applying a predetermined pressure to the accommodating portion by gas, wherein the positive electrode includes a lithium composite material represented by the following Formula 1 And a transition metal oxide.

Li _{1 + a} Ni _b M _c Mn _{2 - (b + c)} O _{4 - z} (1)

Wherein M is one or more selected from the group consisting of Ti, Co, Al, Cu, Fe, Mg, B, Cr, Zr, Zn and two period transition metals, and 0? A? 0.1, 0.5, 0? C? 0.1, 0? Z? 0.1.

When the positive electrode active material containing Mn in a high content as shown in Formula 1 is used, a decrease in capacity is severely caused as the charge / discharge cycle progresses. However, when the pressing portion is included, there is an effect of reducing the capacity and improving the life characteristic.

The reasons for such capacity reduction are various, but gas traps (gas traps) are produced by collecting the gases generated by the decomposition reaction of the electrolytic solution during charge and discharge, and hydrofluoric acid produced by the decomposition reaction of the lithium salt contained in the electrolytic solution HF), a lithium fluoride (LiF) layer formed on the surface of the negative electrode in a nonuniform manner, and dissolution of Mn ^{2 +} existing in the positive electrode active material into an electrolytic solution.

Regarding the generation of the gas trap, when the cathode active material containing Mn in a high content is used, since the activation potential is reached at the oxidation potential of the electrolytic solution due to activation or operation at the high voltage potential, The generation also increases. The portion where the gas trap is generated is inaccessible to the electrolyte, and therefore lithium ion exchange between the active materials is not possible, resulting in a capacity reduction by the corresponding volume.

In this regard, since the pressure of the gas and the volume thereof are inversely proportional to each other (Boyle's law), the pressure of the inside of the cell as in the present invention can reduce the volume of the gas trap even if the same amount of gas is generated, Capacity reduction can also be reduced. Therefore, when the pressure is applied to the storage portion through the pressing portion, the volume of the gas trap can be reduced to improve the life characteristics of the battery.

On the other hand, with respect to HF and LiF, these materials are mainly produced by the decomposition reaction of a lithium salt contained in an electrolytic solution, for example, LiPF ₆ . In particular, HF accelerates the dissolution of Mn in the cathode active material by acidifying the electrolytic solution, thereby destroying the crystal structure of the cathode active material, thereby causing a decrease in capacity of the battery.

LiF is generated on the surface of the negative electrode. Thin and uniformly generated lithium ions do not cause a serious problem. However, when lithium ions are generated unevenly and thickly, lithium ions are hardly exchanged at the lithium ion batteries.

According to the inventors of the present invention, when a battery is operated under a low pressure, when a gas trap is locally generated due to generation of gas, overpotential is generated at the site, and a side reaction such as an electrolyte decomposition reaction is concentrated , Thereby locally forming LiF thick on the cathode surface.

In contrast, when the battery is operated at a high pressure, the reaction occurs uniformly over the entire surface of the electrode, so that even if a LiF layer is formed on the surface of the negative electrode, it is thinly and uniformly produced. Therefore, when pressure is applied to the inside of the battery including the pressing portion as in the present invention, the life characteristic of the battery can be improved by a uniform reaction in the battery.

In this manner, the pressing portion is positioned inside the battery, in consideration of the structural stability of the battery, a cylindrical type can is used instead of the pouch type battery in which the durability of the pouch type battery in which the laminate sheet is thermally fused is poor, It is more suitable for batteries.

In one specific example, the pressurizing portion may comprise a gas of 3 to 25 atmospheres of pressure, in particular a gas of 10 to 25 atmospheres of pressure, more specifically of 15 to 25 atmospheres of gas have.

In the case where the pressurizing part contains gas less than 3 atmospheres, the effect of reducing the volume of the gas trap or decreasing the side reaction is not great by applying pressure to the receiving part, and if it exceeds 25 atmospheres, It is not preferable.

On the other hand, the gas may include a gas generated by a decomposition reaction of an electrolytic solution upon charge and discharge for battery activation. A large amount of gas is generated due to the side reaction during the charge and discharge for activating the battery. If a desired pressure is generated in the pressurizing portion by using such gas, a separate gas injection process is not necessary, The process cost can be reduced.

In one specific example, the volume of the pressing portion may be from 0.1% to 20%, more specifically from 0.1% to 10%, and more specifically from 0.1% to 2% of the volume of the receiving portion.

If the volume of the pressing portion is less than 0.1%, the pressure of the pressing portion may excessively increase, which may be a threat to the safety of the battery. If it exceeds 20%, the space efficiency of the battery is low and the energy density is also low.

In one specific example, the electrolyte may be excessively included so that the electrode assembly is completely immersed.

In the case where the electrode assembly is not completely immersed in the electrolytic solution and the electrolytic solution is appropriately impregnated, the fluidity of the electrolytic solution is relatively low, so that even if gas is generated in the electrode assembly, the electrode assembly is difficult to be discharged to the outside of the electrode assembly, There is a problem that the possibility of doing so is higher.

On the other hand, when the electrode assembly is completely immersed in the electrolyte solution, the gas generated in the electrode assembly is easily discharged to the outside of the electrode assembly due to the flow of the electrolyte, thereby reducing the possibility of gas traps.

In one specific example, the negative electrode is a negative electrode active material, for example, carbon such as non-graphitized carbon or graphite carbon; _{Li x Fe 2 O 3 (0≤x≤1} ), Li x WO 2 (0≤x≤1), Sn x Me 1 - x Me 'y O z (Me: Mn, Fe, Pb, Ge; Me' : Metal complex oxides such as Al, B, P, Si, Group 1, Group 2, Group 3 elements of the periodic table, Halogen, 0 < x < Lithium metal; Lithium alloy; Silicon-based alloys; Tin alloy; _{SnO, SnO 2, PbO, PbO} 2, Pb 2 O 3, Pb 3 O 4, Sb 2 O 3, Sb 2 O 4, Sb 2 O 5, GeO, GeO 2, Bi 2 O 3, Bi 2 O 4, and Bi ₂ O ₅ ; Conductive polymers such as polyacetylene; Li-Co-Ni-based materials; Titanium oxide, and a lithium metal oxide represented by the following formula (2).

Li _a M ' _b O _{4 - ca c} (2)

In the above formula, M 'is at least one element selected from the group consisting of Ti, Sn, Cu, Pb, Sb, Zn, Fe, In, Al and Zr;

a and b are 0.1? a? 4; Is determined according to the oxidation number of M 'in the range of 0.2? B? 4;

c is determined according to the oxidation number in the range of 0? c <0.2;

A is one or more of an anion of -1 or -2.

Specifically, the lithium metal oxide of Formula 2 may be a lithium titanium oxide (LTO) of the formula (3) to, specifically, Li _{0. 8} Ti _{2 . 2} O ₄ , Li _{2 . 67} Ti _{1 . 33} O ₄ , LiTi ₂ O ₄ , Li _{1 . 33} Ti _{1 . 67} O ₄ , Li _{1 . 14} Ti _{1 . 71} O _4, etc. However, there is no particular limitation on the composition and type of lithium ions, as long as they can absorb / release lithium ions. More specifically, there is provided a spinel Li _{1 . 33} Ti _{1 . 67} O ₄ or LiTi ₂ O ₄ .

Li _a Ti _b O ₄ (3)

In the above formula, 0.5? A? 3, 1? B? 2.5.

When a spinel-lithium composite transition metal oxide having a relatively high electric potential is used as a cathode active material, the rate characteristic can be improved by using LTO having a high electric potential as an anode active material, and Li plating .

Meanwhile, the safety vent is a kind of safety element that secures the safety of the battery by discharging the gas to the outside when the internal pressure of the battery increases due to abnormal operation of the battery or deterioration of the battery components. For example, when gas is generated inside the battery and the internal pressure is increased beyond the threshold value, the safety vent ruptures, and the gas discharged to the ruptured portion is discharged through one or two gas outlets formed in the upper cap .

In the present invention, the safety vent may be set to be ruptured at a pressure exceeding 25 atm, and more specifically, may be set to rupture at a pressure of 30 atm or higher.

In one specific example, the cap assembly may further include a protruding upper cap connected along an outer circumferential surface of the safety vent, and may further include a gasket mounted on an outer circumferential surface of the upper cap, Between the upper cap of the assembly and the safety vent, a positive temperature coefficient (PTC) element may be interposed to block the current when the internal temperature of the battery rises.

In addition, a current interrupting device (CID) may be installed in the cap assembly to block an abnormal operation current of the battery and to relieve the internal pressure.

Hereinafter, other components of the cylindrical battery will be described.

The anode is prepared by applying a mixture of a cathode active material, a conductive material and a binder on a cathode current collector, followed by drying and pressing. If necessary, a filler may be further added to the mixture.

The cathode current collector generally has a thickness of 3 to 500 mu m. Such a positive electrode current collector is not particularly limited as long as it has high conductivity without causing chemical changes in the battery. Examples of the positive electrode current collector include stainless steel, aluminum, nickel, titanium, sintered carbon, aluminum or stainless steel A surface treated with carbon, nickel, titanium, silver or the like may be used. The current collector may have fine irregularities on the surface thereof to increase the adhesive force of the cathode active material, and various forms such as a film, a sheet, a foil, a net, a porous body, a foam, and a nonwoven fabric are possible.

The conductive material is usually added in an amount of 1 to 30% by weight based on the total weight of the mixture including the cathode active material. Such a conductive material is not particularly limited as long as it has electrical conductivity without causing chemical changes in the battery, for example, graphite such as natural graphite or artificial graphite; Carbon black such as carbon black, acetylene black, ketjen black, channel black, furnace black, lamp black, and summer black; Conductive fibers such as carbon fiber and metal fiber; Metal powders such as carbon fluoride, aluminum, and nickel powder; Conductive whiskey such as zinc oxide and potassium titanate; Conductive metal oxides such as titanium oxide; Conductive materials such as polyphenylene derivatives and the like can be used.

The binder is a component which assists in bonding of the active material and the conductive material and bonding to the current collector, and is usually added in an amount of 1 to 30% by weight based on the total weight of the mixture containing the cathode active material. Examples of such binders include polyvinylidene fluoride, polyvinyl alcohol, carboxymethylcellulose (CMC), starch, hydroxypropylcellulose, regenerated cellulose, polyvinylpyrrolidone, tetrafluoroethylene, polyethylene , Polypropylene, ethylene-propylene-diene terpolymer (EPDM), sulfonated EPDM, styrene butylene rubber, fluorine rubber, various copolymers and the like.

The filler is optionally used as a component for suppressing the expansion of the anode, and is not particularly limited as long as it is a fibrous material without causing a chemical change in the battery. Examples of the filler include olefin polymers such as polyethylene and polypropylene; Fibrous materials such as glass fibers and carbon fibers are used.

On the other hand, the negative electrode is manufactured by applying, drying and pressing an anode active material on an anode current collector, and may optionally further include a conductive material, a binder, a filler, and the like as described above.

The negative electrode current collector is generally made to have a thickness of 3 to 500 mu m. Such an anode current collector is not particularly limited as long as it has electrical conductivity without causing chemical changes in the battery, and examples of the anode current collector include copper, stainless steel, aluminum, nickel, titanium, sintered carbon, a surface of copper or stainless steel A surface treated with carbon, nickel, titanium, silver or the like, an aluminum-cadmium alloy, or the like can be used. In addition, like the positive electrode collector, fine unevenness can be formed on the surface to enhance the bonding force of the negative electrode active material, and it can be used in various forms such as films, sheets, foils, nets, porous bodies, foams and nonwoven fabrics.

The separation membrane is interposed between the anode and the cathode, and an insulating thin film having high ion permeability and mechanical strength is used. The pore diameter of the separator is generally 0.01 to 10 mu m and the thickness is generally 5 to 300 mu m. Such separation membranes include, for example, olefinic polymers such as polypropylene, which are chemically resistant and hydrophobic; A sheet or nonwoven fabric made of glass fiber, polyethylene or the like is used. When a solid electrolyte such as a polymer is used as an electrolyte, the solid electrolyte may also serve as a separation membrane.

The electrolytic solution contains a lithium salt, and as the electrolytic solution, a non-aqueous organic solvent, an organic solid electrolyte, an inorganic solid electrolyte, and the like are used, but the present invention is not limited thereto.

Examples of the non-aqueous organic solvent include N-methyl-2-pyrrolidinone, propylene carbonate, ethylene carbonate, butylene carbonate, dimethyl carbonate, diethyl carbonate, gamma -Butyrolactone, 1,2-dimethoxyethane, tetrahydroxyfuran, 2-methyltetrahydrofuran, dimethylsulfoxide, 1,3-dioxolane, formamide, dimethylformamide, dioxolane , Acetonitrile, nitromethane, methyl formate, methyl acetate, triester phosphate, trimethoxymethane, dioxolane derivatives, sulfolane, methylsulfolane, 1,3-dimethyl-2-imidazolidinone, propylene carbonate Nonionic organic solvents such as tetrahydrofuran derivatives, ethers, methyl pyrophosphate, ethyl propionate and the like can be used.

Examples of the organic solid electrolyte include a polymer electrolyte such as a polyethylene derivative, a polyethylene oxide derivative, a polypropylene oxide derivative, a phosphate ester polymer, an agitation lysine, a polyester sulfide, a polyvinyl alcohol, a polyvinylidene fluoride, A polymer containing an ionic dissociation group and the like may be used.

Examples of the inorganic solid electrolyte include Li ₃ N, LiI, Li ₅ NI ₂ , Li ₃ N-LiI-LiOH, LiSiO ₄ , LiSiO ₄ -LiI-LiOH, Li ₂ SiS ₃ , Li ₄ SiO ₄ , Nitrides, halides and sulfates of Li such as Li ₄ SiO ₄ -LiI-LiOH and Li ₃ PO ₄ -Li ₂ S-SiS ₂ can be used.

The lithium salt is a material that is readily soluble in the non-aqueous electrolyte, for example, LiCl, LiBr, LiI, LiClO 4, LiBF 4, LiB 10 Cl 10, LiPF 6, LiCF 3 SO 3, LiCF 3 CO 2, LiAsF _{6, LiSbF 6, LiAlCl 4,} CH 3 SO 3 Li, (CF 3 SO 2) 2 NLi, chloroborane lithium, lower aliphatic carboxylic acid lithium, lithium tetraphenyl borate and imide.

In some cases, for the purpose of improving the charge-discharge characteristics and flame retardancy of the electrolytic solution, it is possible to use, for example, pyridine, triethylphosphite, triethanolamine, cyclic ether, ethylenediamine, n-glyme, N, N-substituted imidazolidine, ethylene glycol dialkyl ether, ammonium salt, pyrrole, 2-methoxyethanol, aluminum trichloride, May be added. In some cases, halogen-containing solvents such as carbon tetrachloride and ethylene trifluoride may be further added to impart nonflammability. In order to improve the high-temperature storage characteristics, carbon dioxide gas may be further added. FEC (Fluoro-Ethylene Carbonate, PRS (Propene sultone), and the like.

In one specific _{example, LiPF 6, LiClO 4, LiBF} 4, LiN (SO 2 CF 3) 2 , such as a lithium salt, a highly dielectric solvent of DEC, DMC or EMC Fig solvent cyclic carbonate and a low viscosity of the EC or PC of And then adding it to a mixed solvent of linear carbonate to prepare a lithium salt-containing non-aqueous electrolyte.

The present invention also provides a device comprising the cylindrical battery.

Specific examples of such devices include small devices such as computers, mobile phones, power tools, and the like; power tools powered by an electric motor; An electric vehicle including an electric vehicle (EV), a hybrid electric vehicle (HEV), a plug-in hybrid electric vehicle (PHEV), and the like; An electric motorcycle including an electric bike (E-bike) and an electric scooter (E-scooter); An electric golf cart; Power storage systems, and the like, but are not limited thereto.

The structure of the battery pack and the device is well known in the art, so a detailed description thereof will be omitted herein.

The present invention also provides a method of manufacturing the cylindrical battery,

(a) storing an electrode assembly (jelly-roll) including a positive electrode, a separator, and a negative electrode in a receiving portion of a cylindrical can;

(b) adjusting an amount of the electrolyte injected into the accommodating portion to adjust a relative volume of the pressing portion and the accommodating portion formed between the safety vent and the accommodating portion; And

(c) mounting the cap assembly on the open upper end of the cylindrical can;

.

In one specific example, the method may further comprise the following steps after step (c):

(d) generating a predetermined pressure by performing charge and discharge for activating the cylindrical battery and collecting the gas generated in the charge and discharge in a pressurizing portion.

The storage portion and the pressing portion communicate with each other and collect a gas generated in the battery to generate a predetermined pressure so that the pressure of the pressing portion can be determined according to the relative volume of the pressing portion and the receiving portion.

The pressure of the pressing part can be changed according to the specific configuration and the desired performance of the battery. The pressure of the pressing part can be adjusted by adjusting the amount of the electrolyte injected, so that the required pressure can be flexibly obtained.

In one specific example, in the process (b), the volume of the pressing portion may be adjusted to be 0.1% to 20%, more specifically 0.1% to 10%, more specifically 0.1% to 2% have.

In the step (d), the predetermined pressure may be 3 to 25 atm, more specifically 10 to 25 atm, and more particularly 15 to 25 atm.

As described above, the cylindrical battery and the method of manufacturing the same according to the present invention include a pressing portion that applies a predetermined pressure to the storage portion, thereby reducing the volume of the gas trap and reducing the side reaction, Life characteristics can be improved.

1 is a vertical cross-sectional perspective view of a typical cylindrical battery;
2 is a partial cross-sectional view of a cylindrical battery according to one embodiment of the present invention;
3 is a partial cross-sectional view of a cylindrical battery according to one embodiment of the present invention which differs from the cylindrical battery of FIG. 2 in the amount of electrolyte injection;
FIGS. 4 to 6 are vertical cross-sectional views of a series of processes in which a current is cut off and a high-pressure gas is discharged by operation of a safety vent and a CID in a cylindrical battery according to another embodiment of the present invention; FIG.
7 is a perspective view of a safety vent used in a cylindrical battery;
8 is a graph comparing lifetime characteristics of Example 1 of the present invention and Comparative Example 1;
9 is a graph comparing life characteristics of Example 1 and Example 2 of the present invention.

Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings, but the present invention is not limited by the scope of the present invention.

FIG. 1 is a schematic vertical cross-sectional perspective view of a typical cylindrical battery, and FIGS. 2 and 3 schematically show a partial cross-sectional view of a cylindrical battery according to one embodiment of the present invention.

1 and 2, a cylindrical battery 100 includes a jelly-roll type (wound type) electrode assembly 110 housed in a housing part 230 of a cylindrical can 200, The cap assembly 300 is mounted on the open upper end of the cylindrical can 200 after the electrolyte is injected into the housing part 230 so that the electrode assembly 110 is completely immersed in the electrode assembly 110.

The pressing portion 500 is positioned between the safety vent 320 built in the cap assembly 300 and the receiving portion 230 of the cylindrical can 200. The pressing portion 500 communicates with the receiving portion 230 And a predetermined pressure is applied to the accommodating portion 230 by gas.

The electrode assembly 110 has a structure in which an anode, a cathode, and a separator are sequentially stacked and wound in a round shape. A cylindrical center pin 120 is inserted into the center of the electrode assembly 110. The center pin 120 is generally made of a metal material in order to impart a predetermined strength, and is formed of a hollow cylindrical structure in which a plate material is bent in a round shape. In some cases, after the electrode of the electrode assembly 110 is welded to the cylindrical can 200 or the cap assembly 300, the center pin 120 may be removed.

The cap assembly 300 includes an upper cap 310 and a safety vent for internal pressure drop 310. The cap 310 includes a clamping portion 202 of the cylindrical can 200 and a sealing gasket 400 mounted on the upper inner surface of the beading portion 210, And the upper cap 310 protrudes upward to serve as a positive terminal by connection with an external circuit and the gas inside the can 200 along the periphery of the protrusion A plurality of through-holes 312 are formed.

The safety vent 320 is a thin film structure through which the current passes. The central portion of the safety vent 320 is depressed to form a recessed central portion 322. The upper and lower bent portions of the central portion 322 are formed with two notches 324 and 326 are formed.

The upper surface of the electrode assembly 110 is provided with an insulating plate 220 for preventing contact with the electrode leads 600 to prevent a short circuit due to contact between the electrode assembly 110 and the electrode leads 600 .

Meanwhile, the first notch 324 formed in the upper portion of the notches 324 and 326 forms a closed curve, and the second notch 326 formed in the lower portion has an open curve structure with one side opened. In one example, the engaging force of the second notch 326 is configured to be smaller than the engaging force of the first notch 324, so that the second notch 326 is deeper than the first notch 324.

In this case, when the internal pressure of the can 200 rises above the critical pressure, the second notch 326 of the safety vent 320 fails to withstand the pressure, Through the through-hole 312 of the base plate 311. As shown in FIG.

The volume of the pressing portion 500 is relatively large with respect to the volume of the receiving portion 230 and the relative volume between the pressing portion 500 and the receiving portion 230 can be adjusted according to the amount of the electrolyte injected into the receiving portion 230 have. The electrolytic solution is injected into the insulating plate 220 of the cylindrical battery 100. The volume of the pressing part 500 is proportional to h1 and the volume of the receiving part 230 is proportional to H1.

3, the cylindrical battery 100a has more electrolyte than the cylindrical battery 100, and the electrolyte is injected up to the upper side of the insulating plate 220. As shown in FIG. In this case, the storage portion 230 is located above the insulating plate 220 to the portion where the electrolyte is injected. The volume of the storage portion 230 is further increased compared to the cylindrical battery 100, and the volume thereof is proportional to H2 do. As the volume of the storage part 230 increases, the volume of the pressing part 500 decreases relatively, and the volume of the pressing part 500 is proportional to h2.

FIGS. 4 to 6 show a series of processes of operating the safety vent and the CID in the cylindrical battery according to another embodiment of the present invention, and FIG. 7 is a perspective view of the safety vent.

Referring to these drawings, the upper cap 310 is formed with a protruded anode terminal, an exhaust port is punched therein, and a PTC element (not shown) A safety vent 320 that protrudes downward in a normal state and protrudes when the pressure inside the battery rises and ruptures to exhaust gas, and a safety vent 320 at one side of the upper end is coupled to the safety vent 320, And a current blocking member 800 connected to the positive electrode of the electrode assembly 110 are sequentially positioned. A pressing portion 500 is positioned between the safety vent 320 and the electrode assembly 110. Further, a gasket 810 for a current blocking member for fixing the current blocking member 800 surrounds the outer surface of the current blocking member 800.

The anode of the electrode assembly 110 is electrically connected to the upper cap 310 via the electrode lead 600, the current blocking member 800, the safety vent 320, and the PTC device 700 under normal operating conditions Thereby achieving energization.

However, when gas is generated due to overcharging or the like and the pressure of the pressurizing part 500 increases, as shown in FIG. 5, the safety vent 320 protrudes upward while its shape is reversed. At this time, (320) is disconnected from the current blocking member (800) to cut off the current. Therefore, the overcharging is prevented from further proceeding to secure safety. Nevertheless, if the internal pressure continuously increases, as shown in FIG. 6, the safety vent 320 is ruptured and the pressurized gas is exhausted through the exhaust port of the upper cap 310 via the rupture portion, .

Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings, but it should be understood that the scope of the present invention is not limited thereto.

&Lt; Example 1 >

LiNi _{0 . 5} Mn _{1 . 5} O ₄ was used as a positive electrode active material, and a conductive material (Super-P) and a binder (PVdF) were mixed in NMP at a weight ratio of 90: 5: 5 respectively and mixed to prepare a positive electrode mixture. , Rolled and dried to prepare a positive electrode.

Negative electrode active material _{(.. Li 1 33 Ti 1} 67 O 4), a conductive material (Super-P), a binder (PVdF) of 90: 5: producing a negative electrode material mixture to 5. The weight ratio of the insert to the NMP mixing, and 20 ㎛ thickness Coated on a copper foil, rolled and dried to prepare a negative electrode.

An electrode assembly was fabricated with a separator (thickness: 20 占 퐉) interposed between the anode and the cathode thus prepared. The electrode assembly was housed in a cylindrical can, and then ethylene carbonate (EC), dimethyl carbonate DMC) and ethyl methyl carbonate (EMC) were mixed in a volume ratio of 1: 1: 1 and 4.2 g of an electrolyte solution containing LiPF ₆ as a lithium salt in a concentration of 1 M was injected, The cap assembly was mounted on the open upper end of the cylindrical can and was sealed to manufacture a cylindrical battery, wherein the volume of the pressing portion was 2% of the volume of the receiving portion.

&Lt; Example 2 >

A cylindrical battery was produced in the same manner as in Example 1, except that 3.4 g of the electrolyte solution was injected into the cylindrical can in Example 1. At this time, the volume of the pressing portion was 2.5% of the volume of the receiving portion.

&Lt; Comparative Example 1 &

In Example 1, a battery was prepared in the same manner as in Example 1, except that the electrode assembly and the electrolyte were housed in a pouch-shaped battery case instead of the cylindrical can, and then heat-sealed to manufacture a pouch-shaped battery.

<Experimental Example 1>

The cells of Examples 1 and 2 and Comparative Example 1 were charged and discharged at 1 C in a chamber of 25 ° C, and the capacity retention ratio relative to the initial capacity was measured. The results are shown in FIG. 8 and FIG.

Referring to FIG. 8, the capacity of the pouch-type battery of Comparative Example 1 dropped sharply as the charge and discharge proceeded, while the cylindrical battery of Example 1 exhibited a high capacity retention rate even after 100 cycles.

These results show that, in the case of using a positive electrode active material containing Mn in a high content, the use of the positive electrode active material in a cylindrical battery including a pressing portion is superior to that of a pouch type battery containing no pressing portion, .

Referring to FIG. 9, in Example 2, the capacity retention rate is reduced to about 95% at about 40 cycles, while the capacity retention rate at about 120% is maintained at about 97% in Example 1.

In Example 1 in which the volume of the pressing portion was relatively smaller than that in Example 2, the pressing portion pressure was higher than that in Example 2, and it was found that the life characteristics were further improved due to the difference in pressure.

While the present invention has been described in connection with what is presently considered to be practical exemplary embodiments, it is to be understood that the invention is not limited to the disclosed embodiments, but, on the contrary, is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the appended claims.

Claims (8)

An electrode assembly (jelly-roll) comprising a cathode, a separator, and a cathode comprising a lithium complex transition metal oxide represented by Formula 1 as a cathode active material; An insulating plate positioned at an upper end of the electrode assembly; A cylindrical can including the electrode assembly and a housing portion in which the electrolyte solution is housed; A cap assembly mounted on an open upper end of the cylindrical can; A safety vent embedded in the cap assembly and having a notch formed to rupture by the gas pressure inside the cylindrical battery; And a pressurizing portion located between the safety vent and the accommodating portion and communicating with the accommodating portion to apply pressure to the accommodating portion by gas, the method comprising:
(a) storing the electrode assembly in the accommodating portion;
(b) an electrolytic solution is injected into the accommodating portion up to the upper side of the insulating plate so that the electrode assembly is completely immersed so that the volume of the pressing portion becomes 0.1 to 2% with respect to the volume of the accommodating portion; A process of adjusting the relative volume of the sample;
(c) mounting the cap assembly on the open upper end of the cylindrical can; And
(d) performing charging and discharging of the cylindrical battery, and collecting the generated gas at the time of charging and discharging in the pressing portion such that the pressure applied to the receiving portion is 3 to 25 atm. Method of producing battery:
[Chemical Formula 1]
Li _{1 + a} Ni _b M _c Mn _{2- (b + c)} O _4-z (1)
Wherein M is at least one element selected from the group consisting of Ti, Co, Al, Cu, Fe, Mg, B, Cr, Zr, Zn and two period transition metals, b? 0.5, 0? c? 0.1, and 0? z? 0.1. The method of claim 1, wherein the safety vent is configured to rupture at a pressure greater than 25 atmospheres. The method for manufacturing a cylindrical battery according to claim 1, wherein the negative electrode comprises a lithium metal oxide represented by the following formula (2) as a negative electrode active material:
(2)
Li _{a '} M' _{b '} O _{4 - c'} A _{c '} (2)
In the above formula, M 'is at least one element selected from the group consisting of Ti, Sn, Cu, Pb, Sb, Zn, Fe, In, Al and Zr; a ', b' and c 'are determined according to the oxidation number of M' in the range of 0.1? a '? 4, 0.2? b'? 4 and 0? c '<0.2, respectively; A is an anion of -1 or -2 valence. [4] The method of claim 3, wherein the lithium metal oxide represented by Formula 2 comprises lithium titanium oxide (LTO) represented by Formula 3 below:
(3)
Li _{a "} Ti _{b "} O ₄ (3)
In the above formula, 0.5? A?? 3, 1? B? The method of claim 1, wherein the cap assembly further comprises a protruding top cap connected along an outer circumferential surface of the safety vent. 6. The method of claim 5, wherein the cap assembly further comprises a gasket mounted on an outer circumferential surface of the upper cap. 6. The method of claim 5, wherein a PTC device is interposed between the upper cap of the cap assembly and the safety vent. A cylindrical battery produced by the method of any one of claims 1 to 7.

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