KR101222345B1 - Electrode Assembly for lithium rechargeable battery and Lithium rechargeable battery using the same - Google Patents

Abstract

The present invention relates to an electrode assembly for a lithium secondary battery and a lithium secondary battery using the same, and more particularly, to a carbon dioxide gas at a specific voltage by coating a gasification material on a cathode active material layer of lithium manganese oxide (LMO; the low heating value life characteristics by Kane generate CO ₂₎ and the stability relates to improved lithium secondary battery, an electrode assembly and a lithium secondary battery using the same.

Lithium secondary battery, lithium carbonate, lithium manganate, stability, life characteristics, calorific value

Description

Electrode assembly for lithium secondary battery and lithium secondary battery using same {Electrode Assembly for lithium rechargeable battery and Lithium rechargeable battery using the same}

1 is a vertical cross-sectional view of a lithium secondary battery according to an embodiment of the present invention.

2 is a perspective view of an electrode assembly according to an embodiment of the present invention;

Figure 3 is a cross-sectional view of the positive electrode plate according to an embodiment of the present invention

4 is a cross-sectional view of a bipolar plate according to another embodiment of the present invention.

5A is a graph illustrating a change in battery internal pressure, battery voltage, and battery temperature according to an overcharge time when a gasification material is included according to an exemplary embodiment of the present invention.

5B is a graph showing a change in battery internal pressure, battery voltage, and battery temperature according to an overcharge time when no gasifier is included.

Figure 6a is a side view showing a coating method of the gasification material by the three-roll reverse method

Figure 6b is a side view showing the coating method of the gasification material by the spray method

Figure 6c is a side view showing a coating method of the gasification material by the gravure roll method

Description of the Related Art

100-electrode assembly 110, 210-bipolar plate

112, 212-Positive and negative electrode 113, 213-Positive electrode collector

114, 214-Cathode active material layer 115-Anode tab

116, 216-Gasifier 120-Negative plate

130-Separator 140-Can

160-Cap Assembly 310-Left Roll

320-Center Roll 330-Right Roll

430-spray device

The present invention relates to an electrode assembly for a lithium secondary battery and a lithium secondary battery using the same, and more particularly, to a carbon dioxide gas at a specific voltage by coating a gasification material on a cathode active material layer of lithium manganese oxide (LMO; the low heating value life characteristics by Kane generate CO ₂₎ and the stability relates to improved lithium secondary battery, an electrode assembly and a lithium secondary battery using the same.

2. Description of the Related Art [0002] Portable wireless devices such as video cameras, portable phones, portable computers, and the like are generally made lighter and more sophisticated. Such secondary batteries include, for example, nickel-cadmium batteries, nickel-metal hydride batteries, nickel-zinc batteries, and lithium secondary batteries. Among them, lithium secondary batteries are rechargeable, compact, and large-capacity, and are widely used in advanced electronic devices because of their high operating voltage and high energy density per unit weight.

Lithium, which is widely used as a material of a secondary battery, is a material suitable for manufacturing a battery having a large electric capacity per unit mass because the atomic weight of the element itself is small. On the other hand, lithium reacts violently with moisture, and thus a non-aqueous electrolyte is used in a lithium-based battery. In this case, since it is not affected by the electrolysis voltage of water, the lithium-based battery has an advantage of generating an electromotive force of about 3 to 4 volts.

The non-aqueous electrolyte used in the lithium ion secondary battery includes a liquid electrolyte and a solid electrolyte. The liquid electrolyte is obtained by dissociating a lithium salt into an organic solvent. As the organic solvent, ethylene carbonate, propylene carbonate or other alkyl group-containing carbonates or similar organic compounds can be used.

Such lithium secondary batteries mainly use lithium-based oxides as positive electrode active materials and carbon materials as negative electrode active materials. Generally, a battery using a liquid electrolyte is referred to as a lithium ion battery, and a battery using a polymer electrolyte is referred to as a lithium polymer battery, which is classified as a liquid electrolyte cell and a polymer electrolyte cell, depending on the type of the electrolyte. In addition, the lithium secondary battery is manufactured in various shapes, and typical examples thereof include a cylindrical shape, a square shape, and a pouch type.

Typically, the lithium secondary battery is positioned between the positive electrode plate coated with a positive electrode active material, the negative electrode plate coated with a negative electrode active material, and between the positive electrode plate and the negative electrode plate to prevent a short and prevent lithium ion (Li-ion). It consists of an electrode assembly in which a separator that enables movement only is wound, a case accommodating the electrode assembly, and an electrolyte solution injected into the case to enable movement of lithium ions.

Such a lithium secondary battery is manufactured as follows.

First, the positive electrode active material is coated and the positive electrode tab is connected to the positive electrode tab, the negative electrode active material is coated, the negative electrode plate is connected to the negative electrode tab and the separator is laminated, and then wound to prepare an electrode assembly. Then, the electrode assembly is accommodated in the case to prevent the electrode assembly from being separated, and in the case of a cylindrical lithium secondary battery, an electrolyte is injected into the case and then sealed, and in the case of a rectangular lithium secondary battery, the case is a cap assembly. After sealing, the electrolyte is injected to complete the lithium secondary battery.

As the cathode active material, lithium cobalt oxide (LCO; Lithium Cobalt Oxide) system is mainly used. Lithium cobalt-based cathode active material has a problem that the heat generation during charging due to the instability of the hexagonal (hexagonal) structure and the structure may collapse, resulting in a deterioration of life.

Meanwhile, the cylindrical lithium secondary battery has a safety vane that is deformed when the internal pressure increases due to overcharging to prevent an explosion phenomenon during overcharging, and current blocking means for blocking the current by changing the shape of the safety vant (hereinafter, current blocking). Means), and a secondary protective element or the like in which a current is cut off by a rise in temperature is provided. When the cylindrical lithium secondary battery is in an overcharged state, the electrolyte solution evaporates from approximately the upper region of the electrode assembly and the resistance starts to increase. Moreover, at this point, deformation occurs from approximately the center region of the electrode assembly, and lithium begins to precipitate. Of course, as the resistance of the upper region of the electrode assembly increases, heat generation starts locally, and the battery temperature also rapidly increases. In this state, the internal pressure is rapidly increased by electrolyte additives such as cyclohexylbenzene (CHB) and biphenyl (BP) which are normally decomposed during overcharging to generate gas. This internal pressure pushes the safety vane, which is a component of the cap assembly, outward, thereby breaking the current by breaking the current blocking means installed thereon.

In this case, if the content of cyclohexylbenzene (CHB) or biphenyl (BP), which is an electrolyte additive, is increased, the amount of gas generated during overcharging increases, but in this case, .

The future development direction of secondary batteries is a trend toward high capacity, high safety and slimming. To meet this trend, there is a need to improve the stability of the positive electrode active material during charging and to ensure that safety devices such as safety vents and current blocking means operate on time.

The present invention is to solve the problems of the conventional secondary battery described above, in particular, carbon dioxide (CO ₂ ) at a specific voltage by coating a gasification material on the positive electrode active material layer of lithium manganese oxide (LMO; It is an object of the present invention to provide a lithium secondary battery electrode assembly and a lithium secondary battery using the same, which generates less heat and improves life characteristics and stability.

The electrode assembly for a lithium secondary battery of the present invention for achieving the above object comprises a positive electrode plate having a positive electrode active material layer and a positive electrode non-coating portion, a negative electrode plate having a negative electrode active material layer and a negative electrode non-coating portion and a separator interposed between the positive electrode plate and the negative electrode plate In the lithium secondary battery electrode assembly, the cathode active material layer is formed containing lithium manganese oxide (Lithium Manganese Oxide), the cathode active material layer is characterized in that the gasification material is vaporized at a specific voltage is coated.

At this time, the cathode active material layer may be made of a lithium compound selected from the group consisting of (1) to (4).

Li _x Mn _{1 - y} M _y A ₂ (1)

Li _x Mn _{1 - y} MyO _{2 - z} X _z (2)

Li _x Mn ₂ O _{4 - z} X _z (3)

Li _x Mn _{2 - y} M _y M ' _z A ₄ (4)

(Wherein 0.9 ≦ x ≦ 1.1, 0 ≦ y ≦ 0.5, 0 ≦ z ≦ 0.5, M and M ′ are the same or different, Mg, Al, Co, K, Na, Ca, Si, Ti, Sn, V, Ge, Ga, B, As, Zr, Mn, Cr, Fe, Sr, V and rare earth elements, A is selected from the group consisting of O, F, S and P, X is F , S and P.)

In addition, the gasification material may be coated on part or the entire surface of the cathode active material layer. In addition, the gasification material may be coated on the boundary between the positive electrode active material layer and the positive electrode non-coating portion. In addition, the gasification material is preferably gasified by the decomposition of the potential difference between the internal electrodes at least 4.5V. In addition, the gasification material may be lithium carbonate (Li ₂ CO ₃ ).

In addition, the gasification material may be coated by any one of a three-roll reverse method, a spray (spray) method, a gravure roll method (gravure roll) method.

In addition, the lithium secondary battery of the present invention is an electrode assembly comprising a positive electrode plate having a positive electrode active material layer and a positive electrode non-coating portion, a negative electrode plate having a negative electrode active material layer and a negative electrode non-coating portion and a separator interposed between the positive electrode plate and the negative electrode plate, the electrode assembly In a lithium secondary battery comprising a can assembly and a cap assembly for sealing the top opening of the can, the cathode active material layer is formed of lithium manganese oxide (Lithium Manganese Oxide), the cathode active material layer is a specific voltage Characterized in that the gasification material is vaporized in the coating.

At this time, the cathode active material layer may be made of a lithium compound selected from the group consisting of (1) to (4).

Li _x Mn _{1 - y} M _y A ₂ (1)

Li _x Mn _{1 - y} MyO _{2 - z} X _z (2)

Li _x Mn ₂ O _{4 - z} X _z (3)

Li _x Mn _{2 - y} M _y M ' _z A ₄ (4)

(Wherein 0.9 ≦ x ≦ 1.1, 0 ≦ y ≦ 0.5, 0 ≦ z ≦ 0.5, M and M ′ are the same or different, Mg, Al, Co, K, Na, Ca, Si, Ti, Sn, V, Ge, Ga, B, As, Zr, Mn, Cr, Fe, Sr, V and rare earth elements, A is selected from the group consisting of O, F, S and P, X is F , S and P.)

In addition, the gasification material may be coated on part or the entire surface of the cathode active material layer. In addition, the gasification material may be coated on the boundary between the positive electrode active material layer and the positive electrode non-coating portion. In addition, the gasification material is preferably gasified by the decomposition of the potential difference between the internal electrodes at least 4.5V. In addition, the gasification material may be lithium carbonate (Li ₂ CO ₃ ).

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings.

First, a lithium secondary battery according to an embodiment of the present invention will be described. Hereinafter, for convenience, the cylindrical lithium secondary battery has been described as an example, but the present invention can be applied to the square and pouch type lithium secondary batteries.

1 is a vertical cross-sectional view of a lithium secondary battery according to an embodiment of the present invention. FIG. 2 is a perspective view of the electrode assembly of FIG. 1. FIG. 3 is a cross-sectional view of the positive electrode plate in FIG. 2.

A lithium secondary battery according to an embodiment of the present invention, referring to FIG. 1, includes an electrode assembly 100, a can 140, and a cap assembly 160.

Referring to FIG. 2, the electrode assembly 100 includes a positive electrode plate 110 having a positive electrode active material layer 114 formed in a predetermined region of a positive electrode current collector 113, and a negative electrode plate having a negative electrode active material layer formed in a predetermined region of a negative electrode current collector. And a separator 130 interposed between the positive electrode plate 110 and the negative electrode plate 120 to prevent short of the positive electrode plate 110 and the negative electrode plate 120 and to allow only movement of lithium ions. It is wound and formed in roll shape. In addition, the electrode assembly 100 may include a positive electrode tab 115 and a negative electrode tab 125.

Referring to FIG. 3, the positive electrode plate 110 includes a positive electrode current collector 113, a positive electrode active material layer 114, and a positive electrode non-coating portion 112. In addition, the positive electrode plate 110 is formed to include a gasification material 116 formed to cover a part or all of the surface of the positive electrode active material layer 114.

The positive electrode current collector 113 is formed of a conductive metal material so as to collect electrons from the positive electrode active material layer 114 to move to an external circuit, and is generally made of aluminum.

The cathode active material layer 114 is manufactured by mixing a cathode active material, a conductive material, and a binder, and is formed by coating a predetermined thickness on one or both surfaces of the cathode current collector 113. The cathode active material is made of lithium manganese oxide. For example, the cathode active material layer 114 is Li _x Mn _{1 - y} M _y A ₂ (1), Li _x Mn _{1 - y} MyO _{2 - z} X _z (2), Li _x Mn ₂ O _{4 -z} It may be formed including any one selected from X _z (3), Li _x Mn _{2 - y} M _y M ' _z A ₄ (4). In the above formula, 0.9≤x≤1.1, 0≤y≤0.5, 0≤z≤0.5, M and M 'are the same or different, Mg, Al, Co, K, Na, Ca, Si, Ti, Sn, V , Ge, Ga, B, As, Zr, Mn, Cr, Fe, Sr, V and rare earth elements, A is selected from the group consisting of O, F, S and P, X is F, It is selected from the group consisting of S and P. Lithium cobalt oxide (Lithium Cobalt Oxide) is composed of a hexagonal structure (hexagonal) structure that is unstable during charging, whereas lithium manganate is composed of a spinel (spinel) structure. Therefore, lithium manganate-based hardly disintegrates even when a large amount of lithium ions are released, indicating structural stability. As a result, the calorific value is also reduced, and the life characteristics are improved. The amount of heat generated is an important factor in inducing the battery to the deterioration mode in various characteristics including battery overcharge characteristics.

The anode non-coating portion 112 is a portion in which the cathode active material layer 114 is not formed in the cathode current collector 113. The positive electrode tab 216 is welded to one side of the positive electrode non-coating portion 112.

The gasification material 116 is coated on a part or the entire surface of the cathode active material layer 114 to a predetermined thickness. Referring to FIG. 3, the gasification material 116 is formed to have a uniform thickness on the entire surface of the cathode active material layer 114. Although the gasification material 116 is not shown, the gasification material 116 may be formed on a part of the surface of the cathode active material layer 114, and may be formed on the entire surface of the cathode active material layer 114, but may have a non-uniform thickness. Of course. However, the gasification material 116 is preferably formed to have a uniform thickness in terms of ensuring uniformity of the electrode assembly 100. The gasification material 116 faces the negative electrode plate 120 with the separator 130 interposed therebetween. The thickness of the gasifier 116 is determined according to the amount of gas to be generated.

In addition, the gasification material 116 is preferably gasified by decomposition of the potential difference between the internal electrode at 4.5V or more. Charging of a lithium secondary battery usually consists of constant voltage / constant current charging. In this method, the charging voltage is set at a constant voltage of approximately 4.1 V or 4.2 V, and the battery voltage is charged at a constant current until the battery voltage reaches the set voltage. After reaching the set voltage, the current value naturally decreases. Therefore, if the charging voltage is correctly controlled in the charger, there is no overcharge phenomenon. However, if the charger is broken or malfunctions, or there is a possibility of abnormal charging due to the user's misuse. If overcharging continues, the voltage of the battery will rise to 5.0V. Therefore, when it is over 4.5V, which can be regarded as an overcharge state, the charging must be stopped by cutting off the current. If the gasification material 116 is gasified at 4.5V or less, it vaporizes even before overcharging and raises the internal pressure of the battery, thereby operating the safety vent 161 so that the battery can no longer be used.

Lithium fluoride (LiF), lithium carbonate (Li ₂ CO ₃ ), and the like are decomposed and vaporized at a specific voltage. Lithium fluoride (LiF) is usually decomposed and vaporized at 4V, and lithium carbonate (Li ₂ CO ₃ ) is usually decomposed and vaporized at 4.8 to 5.0V. Lithium fluoride (LiF) is not suitable for use as a gasification material because it degrades during charging due to its low decomposition voltage. The decomposition reaction of lithium carbonate (Li ₂ CO ₃ ) is represented as follows.

Li ₂ CO ₃ ↔ Li ₂ O + CO ₂ ↑

That is, lithium carbonate (Li ₂ CO ₃ ) is decomposed into lithium oxide (LiO ₂ ) and carbon dioxide (CO ₂ ) under a voltage of 4.8 to 5.0V. At this time, when the internal temperature of the battery reaches 80 to 200 ° C. due to the pressure of the carbon dioxide (CO ₂ ) and the overcharging, due to gasification of cyclohexylbenzene (CHB), biphenyl (BP), etc. contained in the electrolyte. Pressure is added to deform or rupture the safety vent 161 to destroy the current interruption means 162 and the current is cut off. Therefore, explosion and fire of the battery due to overcharging are prevented.

5A and 5B show graphs based on experimental data in preparation for the case where lithium carbonate is included and when lithium carbonate is not included.

5A is a graph showing a change in battery internal pressure, battery voltage, and battery temperature according to overcharge time when lithium carbonate is included. Referring to FIG. 5A, when the overcharge time exceeds 60 minutes, the voltage of the battery rises to 4.5V or more, and when the battery reaches approximately 4.8V, lithium carbonate decomposes to generate carbon dioxide gas, thereby rapidly increasing the battery internal pressure. Accordingly, the safety vent 161 is operated and the current blocking means 162 is cut off to block the flow of current, and the battery temperature is suppressed to about 50 ° C. to prevent thermal runaway.

5B is a graph showing a change in battery internal pressure, battery voltage, and battery temperature according to an overcharge time when lithium carbonate is not included. Referring to FIG. 5B, even when the battery voltage rises sharply, the increase in the battery internal pressure is slight, and thus the pressure is insufficient to operate the safety vent 161. Therefore, thermal runaway occurs, and further progresses eventually cause the battery to ignite and explode. At this time, the slight increase in the battery internal pressure is mainly due to gasification of cyclohexylbenzene (CHB), biphenyl (BP) and the like contained in the electrolyte solution.

The negative electrode plate 120 includes a negative electrode current collector, a negative electrode active material layer, and a negative electrode non-coating portion. The negative electrode current collector is formed of a conductive metal material to collect electrons from the negative electrode active material layer and move them to an external circuit. The negative electrode active material layer is prepared by mixing a negative electrode active material, a conductive material and a binder, and is formed by coating a predetermined thickness on the negative electrode current collector. The negative electrode non-coating portion is a portion in which a negative electrode active material layer is not formed in the negative electrode current collector, and the negative electrode tab 125 is welded to one side of the negative electrode non-coating portion.

The positive electrode tab 115 and the negative electrode tab 125 are respectively welded to the positive electrode non-coating portion 112 and the negative electrode non-coating portion to serve to electrically connect the electrode assembly 100 and other parts of the battery. The positive electrode tab 115 and the negative electrode tab 125 are welded by resistance welding, and a lamination tape may be attached to the welding portion to prevent short and heat generation. Here, the welding method of the positive electrode tab 115 and the negative electrode tab 125 is not limited.

The separator 130 may be interposed between the positive electrode plate 110 and the negative electrode plate 120 and extend to surround the outer circumferential surface of the electrode assembly 100. The separator 130 is formed of a porous membrane polymer material to prevent short circuit between the positive electrode plate 110 and the negative electrode plate 120 and to allow lithium ions to pass therethrough.

The can 140 is formed in a cylindrical shape including a side plate 141 and a bottom plate 142. In addition, the side plate 141 has an outer circumferential surface and an inner circumferential surface that are substantially concentric with each other, and the bottom plate 142 has a front and a rear surface which are substantially parallel to each other. An upper end of the can 140 is opened to form an upper opening, and an electrode assembly 100 is inserted through the upper opening, and an electrolyte is injected. A lower insulating plate 132 may be inserted between the lower plate 142 and the electrode assembly 100 of the can 140 to insulate the can 140 and the electrode assembly 100 from each other. The upper portion of the can 140 prevents the electrode assembly 100 from flowing in the can 140 after the electrode assembly 100 is inserted, and the beading portion 144 is provided to seat the cap assembly 160. After the insertion of the cap assembly 160, the creeping part 143 is formed to seal the battery. An upper insulating plate 134 may be inserted between the upper end of the electrode assembly 100 and the cap assembly 160 to insulate the electrode assembly 100 and the cap assembly 160. The can 140 is preferably formed of aluminum, nickel, or an alloy thereof, and the can 140 is not limited thereto. The can 140 is preferably manufactured by a deep drawing method, and the method of manufacturing the can 140 is not limited thereto.

The cap assembly 160 includes a safety vent 161, a current blocking means 162, a secondary protective element 163, and a cap up 164.

The safety vent 161 has a plate-like protrusion formed at the center to protrude downward. The safety vent 161 is positioned below the cap assembly 160, and the protrusion is deformed upward by the pressure generated inside the secondary battery. The positive electrode tab 115 drawn from the positive electrode plate 110 and the negative electrode plate 120 of the electrode assembly 100, for example, the positive electrode plate 110, is welded to a predetermined surface of the lower surface of the safety vent 161. The safety vent 161 and the positive electrode plate 110 of the electrode assembly 100 are electrically connected. Herein, the other electrode plate of the positive electrode plate 110 and the negative electrode plate 120, for example, the negative electrode plate 120, has the negative electrode tab 125 drawn from the negative electrode plate 120 being welded to the bottom surface 142 of the can 140. It is electrically connected to the can 140. The safety vent 161 is deformed or ruptured when the pressure rises in the can 140, thereby serving to damage the current interruption means 162. In addition, an upper portion of the safety vent 161, the current blocking means 161 that is damaged when the deformation of the safety vent 161 is cut off is further located, the upper portion of the current blocking means 162 is overcurrent The secondary protection element 163 is located to block the current. In addition, an upper portion of the secondary protection element 163 is further provided with a conductive cap up 164 for providing a positive voltage or a negative voltage to the outside. In addition, the cap assembly 160 further includes a gasket 150 to insulate the cap assembly 160 serving as an anode and the can 140 serving as a cathode.

Next, a lithium secondary battery according to another embodiment of the present invention will be described.

4 is a sectional view of a positive electrode plate according to another embodiment of the present invention. 4 is similar to the embodiment of FIG. 3 except that the gasification material 216 is coated on the boundary between the positive electrode active material layer 214 and the positive electrode non-coating portion 212, and thus the description will be mainly focused on differences.

Lithium secondary battery according to another embodiment of the present invention is formed including an electrode assembly, a can and a cap assembly. Since the can and the cap assembly have been sufficiently described in the embodiment of FIG. 3, detailed description thereof will be omitted.

The electrode assembly is formed to include a positive electrode plate 210, a negative electrode plate and a separator. Since the negative electrode plate and the separator are formed in the same manner as in the embodiment of FIG. 3, a detailed description thereof will be omitted.

Referring to FIG. 4, the positive electrode plate 210 includes a positive electrode current collector 213, a positive electrode active material layer 214, and a positive electrode non-coating portion 212. In addition, the positive electrode plate 210 is formed to include a gasification material 216 coated on the boundary between the positive electrode active material layer 214 and the positive electrode non-coating portion 212.

The gasification material 216 may further include an adhesive for smooth adhesion to the cathode active material layer 214. As described above, the gasification material 216 is preferably gasified by dissolving the potential difference between internal electrodes at least 4.5V, and lithium carbonate (Li ₂ CO ₃ ) is particularly suitable. In addition, the amount may be adjusted by adjusting the coating area of the gasification material 216 layer. In the positive electrode plate, the boundary between the positive electrode active material layer 214 and the positive electrode non-coating portion 212 is a portion where the active material attached to the positive electrode current collector 213 is likely to fall off, which may cause an internal short circuit. The gasification material 216 layer is coated on the boundary between the positive electrode active material layer 214 and the positive electrode non-coating portion 212 to prevent the short with the effect of gas generation at a specific voltage.

6A-6C show side views illustrating a method of coating a gasifier in accordance with the embodiment of FIG. 3. Of course, the embodiment of Figure 4 can also be coated by this method.

FIG. 6A is a side view illustrating a method of coating a gasification material by a 3-roll reverse method. FIG. The three-roll reverse method uses three rolls 310, 320, 330 that are interlocked with each other to apply a layer of gasifier 116. Here, for convenience, the roll located on the left side of the three rolls is referred to as the left roll 310, the roll located in the center of the center roll 320, and the right roll 330. However, the number of rolls is not limited here. The gaseous material 116 to be coated is supplied to the left roll 310, and the gaseous material 116 is moved to the center roll 320 while the left roll 310 rotates clockwise when viewed from the front. The central roll 320 also rotates the gasification material 116 that has moved while rotating clockwise to the right roll 330. During the movement, the amount of gasification material 116 gradually decreases and reaches the right roll 330 to be adjusted to an amount suitable for application. The right roll 330 has a positive electrode plate 110 to be applied, and unlike the other rolls (310, 320), by rotating in a counterclockwise direction, the positive electrode plate 110 is a constant direction by interacting with the central roll (320) It works so that you can move to.

Figure 6b is a side view showing a method for coating the gasification material by the spray (spray) method. The spray method uses the left and right rolls 410 and 420 to move the positive electrode plate 110 to coat the gasification material, and sprays the gasification material by installing a spray device 430 thereon. For convenience, the roll located on the left side will be referred to as the left roll 410 and the roll located on the right side as the right roll 420. Here, the number of rolls is not limited.

Figure 6c is a side view showing a method of coating the gasification material by a gravure roll (gravure roll) method. In the gravure roll method, the gasification material 116 is buried on the surface of the roller 510 and the gasification material 116 is coated by rotating the roller 510 in the direction of the arrow on the anode plate 110 to be coated.

Next will be described the operation of the lithium secondary battery according to an embodiment of the present invention.

In the lithium secondary battery according to an embodiment of the present invention, a cathode active material is formed of lithium manganese-based material, and a gasification material such as lithium carbonate is coated on the cathode active material layer.

The lithium secondary battery has a lithium manganate-based cathode active material, which maintains structural stability even when a large portion of lithium ions are removed during charging, and thus generates less heat and improves life characteristics. In addition, when the voltage of the lithium secondary battery becomes approximately 4.5 V or more due to overcharging, lithium carbonate decomposes to generate carbon dioxide gas (CO ₂ ). In addition, since the temperature inside a battery rises at this time, a part of cyclohexylbenzene (CHB), biphenyl (BP), etc. contained in electrolyte solution gasify. In the case of the cylindrical lithium secondary battery, the large amount of gases rapidly deform or rupture the safety band, thereby destroying the current interruption means to cut off the current, thereby preventing overcharging, and preventing internal temperature rise. In the case of the rectangular lithium secondary battery, the large amount of gases rupture the safety vent quickly to discharge the gas to the outside, thereby preventing the explosion of the battery.

As described above, the present invention is not limited to the specific preferred embodiments described above, and any person having ordinary skill in the art to which the present invention belongs without departing from the gist of the present invention as claimed in the claims. Various modifications are possible, of course, such changes are within the scope of the claims.

According to the lithium secondary battery according to the present invention, by using a lithium manganate-based cathode active material having a spinel structure, the amount of heat generated is low, safety is improved, and life characteristics are improved.

In addition, the lithium secondary battery according to the present invention has an effect of improving the safety of the secondary battery by generating a carbon dioxide (CO ₂ ) at a specific voltage during overcharging to operate a safety device.

In addition, according to the lithium secondary battery according to the present invention there is an effect that the internal short of the battery can be prevented by coating the gasification material on a portion where the active material is easy to drop off.

Claims (13)

In the electrode assembly for a lithium secondary battery comprising a positive electrode plate having a positive electrode active material layer and a positive electrode non-coating portion, a negative electrode plate having a negative electrode active material layer and a negative electrode non-coating portion, and a separator interposed between the positive electrode plate and the negative electrode plate, The positive electrode active material layer is formed of lithium manganese oxide (Lithium Manganese Oxide), the positive electrode active material layer is coated with a gasification material to be gasified at a specific voltage, the gasification material is lithium carbonate (Li ₂ CO ₃ ) An electrode assembly for a lithium secondary battery, characterized in that. The method of claim 1, The cathode active material layer is a lithium secondary battery electrode assembly, characterized in that made of a lithium compound selected from the group consisting of (1) to (4). Li _x Mn _{1 - y} M _y A ₂ (1) Li _x Mn _{1 - y} MyO _{2 - z} X _z (2) Li _x Mn ₂ O _{4 - z} X _z (3) Li _x Mn _{2 - y} M _y M ' _z A ₄ (4) (Wherein 0.9 ≦ x ≦ 1.1, 0 ≦ y ≦ 0.5, 0 ≦ z ≦ 0.5, M and M ′ are the same or different, Mg, Al, Co, K, Na, Ca, Si, Ti, Sn, V, Ge, Ga, B, As, Zr, Mn, Cr, Fe, Sr, V and rare earth elements, A is selected from the group consisting of O, F, S and P, X is F , S and P.) The method of claim 1, The gasification material is a lithium secondary battery electrode assembly, characterized in that the coating on part or all of the surface of the positive electrode active material layer. The method of claim 1, The gasification material is a lithium secondary battery electrode assembly, characterized in that the coating on the boundary between the positive electrode active material layer and the positive electrode non-coating portion. The method of claim 1, Wherein the gasification material is a lithium secondary battery electrode assembly characterized in that the potential difference between the internal electrode is decomposed at least 4.5V and gasified. delete The method of claim 1, The gasification material is an electrode assembly for a lithium secondary battery, characterized in that the coating by any one of a three-roll reverse method, a spray method, a gravure roll method. An electrode assembly comprising a positive electrode plate having a positive electrode active material layer and a positive electrode non-coating portion, a negative electrode plate having a negative electrode active material layer and a negative electrode non-coating portion, and a separator interposed between the positive electrode plate and the negative electrode plate, a can housing the electrode assembly and an upper opening of the can In the lithium secondary battery comprising a cap assembly for sealing the, The positive electrode active material layer is formed of lithium manganese oxide (Lithium Manganese Oxide), the positive electrode active material layer is coated with a gasification material to be gasified at a specific voltage, the gasification material is lithium carbonate (Li ₂ CO ₃ ) Lithium secondary battery characterized in that. 9. The method of claim 8, The cathode active material layer is a lithium secondary battery, characterized in that made of a lithium compound selected from the group consisting of (1) to (4). Li _x Mn _{1 - y} M _y A ₂ (1) Li _x Mn _{1 - y} MyO _{2 - z} X _z (2) Li _x Mn ₂ O _{4 - z} X _z (3) Li _x Mn _{2 - y} M _y M ' _z A ₄ (4) (Wherein 0.9 ≦ x ≦ 1.1, 0 ≦ y ≦ 0.5, 0 ≦ z ≦ 0.5, M and M ′ are the same or different, Mg, Al, Co, K, Na, Ca, Si, Ti, Sn, V, Ge, Ga, B, As, Zr, Mn, Cr, Fe, Sr, V and rare earth elements, A is selected from the group consisting of O, F, S and P, X is F , S and P.) 9. The method of claim 8, The gasification material is a lithium secondary battery, characterized in that coated on part or the entire surface of the positive electrode active material layer. 9. The method of claim 8, The gasification material is a lithium secondary battery, characterized in that the coating on the boundary between the positive electrode active material layer and the positive electrode non-coating portion. 9. The method of claim 8, The gasification material is a lithium secondary battery, characterized in that the potential difference between the internal electrode is decomposed at least 4.5V and gasified. 9. The method of claim 8, The gasification material is a lithium secondary battery, characterized in that lithium carbonate (Li ₂ CO ₃ ).

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