KR101058313B1 - Electrochemical device showing excellent safety - Google Patents

Abstract

The present invention relates to an electrochemical device in which an electrode assembly including one or more first electrodes, one or more separators, and one or more second electrodes is housed in a container, wherein the container is intentionally separated from the outside by a predetermined pressure or pressure. Or an electrochemical device characterized in that one or more protrusions capable of rupturing both are formed on an inner surface.

The electrochemical device can secure the safety of the electrochemical device when a physical shock is applied from the outside, such as compression, impact.

Description

ELECTROCHEMICAL DEVICE ENSURING A GOOD SAFETY

1 illustrates a conventional electrochemical device in which a wound electrode assembly is accommodated in a battery can.

Figure 2 is a schematic diagram showing the mechanism of action showing the safety when using the container according to one embodiment of the present invention.

Figure 3 shows the collapse test results of the battery prepared in Comparative Example 1.

Figure 4 shows the collapse test results of the battery prepared in Example 1.

[Description of Symbols for Major Parts of Drawing]

1: negative electrode, 2: positive electrode, 3: separator, 4: insulating plate, 5: battery can, 6: sealing gasket, 7: cap, 8: safety plate device, 9: PTC element, 10: negative electrode current collector, 11: positive electrode current collector, 12: negative electrode tab, 13: positive electrode tab, 14: center pin

The present invention relates to an electrochemical device in which an electrode assembly including one or more first electrodes, one or more separators, and one or more second electrodes is housed in a container, when a physical shock such as a compression or an impact is applied. It relates to a structure of a container that can ensure safety.

Recently, as miniaturization and light weight of electronic equipment have been realized, and the use of portable electronic devices has become common, research on lithium secondary batteries having high energy density has been actively conducted.

A lithium secondary battery is prepared by using a material capable of inserting and detaching lithium ions in a cathode and an anode, and filling an organic electrolyte or a polymer electrolyte between the cathode and the anode, and lithium ions comprising the anode and Electrical energy is generated by oxidation and reduction reactions when inserted and detached from the cathode.

However, since such a lithium secondary battery has a safety problem, attempts have been made to solve this problem.

In general, a lithium secondary battery using a flammable non-aqueous electrolyte has a flammable gas due to decomposition reaction of the electrolyte when the temperature inside the battery rises, a flammable gas due to the reaction between the electrolyte and the electrode, and oxygen generated by decomposition of the anode. Has a problem that occurs.

On the other hand, when the battery is pressed by a heavy object or subjected to a strong shock, safety problems occur. That is, in the case of nail penetration, compression, impact, etc., the positive electrode and the negative electrode inside the battery locally generate short circuits. At this time, locally excessive current flows and heat is generated by this current. Since the magnitude of the short circuit current due to local short circuit is inversely proportional to the resistance, the short circuit current flows much toward the lower resistance. At this time, a very high heat generation is generated locally around the short circuit part.

When heat is generated inside the battery, the positive electrode, the negative electrode, and the electrolyte constituting the inside of the battery react or burn with each other. This reaction is a very large exothermic reaction and eventually ignites or explodes. Therefore, in such a case, it is necessary to prevent rapid generation of heat inside the battery.

An object of the present invention is to provide an electrochemical device having a container that can ensure the safety of the electrochemical device when a physical shock is applied from the outside, such as compression, impact.

The present invention relates to an electrochemical device in which an electrode assembly including one or more first electrodes, one or more separators, and one or more second electrodes is housed in a container, wherein the container is intentionally separated from the outside by a predetermined pressure or pressure. Or an electrochemical device characterized in that one or more protrusions capable of rupturing both are formed on an inner surface.

Hereinafter, the present invention will be described in detail.

An electrode assembly accommodated by a container according to the present invention includes at least one first electrode, at least one separator and at least one second electrode.

As illustrated in FIG. 1, the electrode assembly may be a wound electrode assembly in which a first separator, a first electrode, a second separator, and a second electrode are stacked and stacked.

In addition, the electrode assembly may be a stacked type in which at least one first electrode, at least one separator, and at least one second electrode are stacked.

The container according to the invention is characterized in that one or more protrusions are formed on the inner surface which can intentionally rupture the membrane, the electrode or both upon pressure pressurization from the outside.

The protrusions may adjust internal or external pressure limits that may rupture the separator, electrode, etc. by adjusting the sharpness and / or strength.

When the protrusion is formed on the inner surface of the container it can exhibit the following effects.

When a physical shock is applied to the outside of the battery, a short circuit occurs inside the battery as the separator for preventing the positive and negative electrode contacts from being torn. In this case, when a short circuit occurs, the battery may ignite or explode because high energy of the battery is concentrated in the micro area where the short circuit occurs and heat due to overcurrent is concentrated in the micro area, causing instantaneous thermal runaway.

Accordingly, the present invention preferably intentionally causes a plurality of short circuits by intentionally rupturing the separator or electrode by the protrusion formed on the inner surface of the container when the external impact is applied, thereby distributing the short circuit current to the plurality of short circuit sites. By dissipating the generated current and / or heat into the vessel, it is intended to avoid situations where the cell is at risk from thermal runaway.

In this case, in order to intentionally generate a plurality of short circuits by the protrusions formed on the inner surface of the container, the protrusion may rupture the separator adjacent to the container when the pressure is exerted by a predetermined pressure from the outside, or the first separator, the second electrode plate, 2 The membrane should be able to rupture.

In order to intentionally generate a short circuit by only the membrane rupture, the container is made of an electrically conductive material and is electrically connected to the second electrode. In general, the container should be insulated from the first electrode plate by the first separator. .

An example of such a container is an assembly having a can and a cap sealing the can. In this case, the can is made of a material having electrical conductivity and may serve as a second electrode terminal electrically connected to the second electrode (see FIG. 1).

On the other hand, when the first separator, the second electrode plate and the second separator are ruptured in order to intentionally generate a short circuit, the container is insulated from the electrode terminal.

Referring to FIGS. 1 and 2, an example of the present invention may include a battery can 5 having one or more protrusions formed on an inner surface thereof that may rupture the separator when the pressure is exerted from the outside. The material is electrically connected to the second electrode tab 12 provided in the second electrode. Normally, the battery can electrically connected to the second electrode is insulated from the first electrode by the first separator, and when the pressure is applied from the outside by a predetermined pressure, the first separator is ruptured at one or more portions by the protrusion. This can intentionally generate a short circuit between the container and the first electrode. Thus, by dispersing the short-circuit current into a plurality of short-circuit sites and by dispersing it into the battery can 5, a situation in which the battery is dangerous due to thermal runaway can be avoided (see FIG. 2).

It is preferable that the container according to the present invention is an electrically conductive material. If the container is made of an electrically conductive material, a short circuit current can be distributed to the container through the one or more protrusions. Non-limiting material of the container is a metal material such as stainless steel, titanium, nickel, aluminum.

In addition, the container is preferably made of a thermally conductive material. This is because heat generated at the time of short circuit can be disperse | distributed to a container (refer FIG. 2).

Only the protrusions may be provided using a material different from that of the container substrate.

The height of the protrusion in the container is about 0.1 to 1mm, preferably 0.1 to 0.5mm, more preferably 0.1 to 0.3mm, most preferably 0.1 to 0.2mm, the protrusion is not bad when inserting the jelly roll It is good to form.

It is preferable that the protrusions are uniformly distributed on the entire inner surface of the container in view of safety effect.

The electrochemical device of the present invention configured as described above to improve safety includes all devices that undergo an electrochemical reaction, and specific examples thereof include all kinds of primary, secondary, fuel cells, solar cells, or capacitors. and the like. In particular, a lithium secondary battery including a lithium metal secondary battery, a lithium ion secondary battery, a lithium polymer secondary battery or a lithium ion polymer secondary battery among the secondary batteries is preferable. However, the present invention is applicable to all electrochemical devices such as nickel hydrogen batteries and nickel cadmium batteries in addition to lithium ion batteries. In addition, it is also applicable to the development of a new battery to replace the lithium ion battery in the future.

In addition, the shape of the electrochemical device used in the present invention is not particularly limited and may be of various sizes. In addition to the cylindrical shape, it may have various sizes and / or shapes such as thin and large, and the same may be applied to the pack case, the hard pack, and the soft pack.

General matters related to the electrochemical device other than the container according to the present invention will be described in more detail with reference to an example of a battery for lithium charging and discharging.

The lithium charging / discharging battery includes a positive electrode including a lithium composite oxide as an active material, a negative electrode capable of adsorbing and releasing lithium, a nonaqueous electrolyte, and a separator.

The positive electrode active material may be a conventional positive electrode active material that can be used for the positive electrode of the conventional electrochemical device, non-limiting examples thereof, such as LiM _x O _y (M = Co, Ni, Mn, Co _a Ni _b Mn _c ) Lithium transition metal composite oxides (for example, lithium manganese composite oxides such as LiMn ₂ O ₄ , lithium nickel oxides such as LiNiO ₂ , lithium cobalt oxides such as LiCoO ₂ , and some of manganese, nickel and cobalt oxides thereof Or a vanadium oxide containing lithium or the like, or a chalcogen compound (for example, manganese dioxide, titanium disulfide, molybdenum disulfide, or the like). Preferably LiCoO ₂ , LiNiO ₂ , LiMnO ₂ , LiMn ₂ O ₄ , Li (Ni _a Co _b Mn _c ) O ₂ (0 <a <1, 0 <b <1, 0 <c <1, a + b + c = 1), LiNi _1-Y Co _Y O ₂ , LiCo _1-Y Mn _Y O ₂ , LiNi _1-Y Mn _Y O ₂ (where 0 ≦ Y <1), Li (Ni _a Co _b Mn _c ) O ₄ (0 <a <2, 0 <b <2, 0 <c <2, a + b + c = 2), LiMn _2-z Ni _z O ₄ , LiMn _2-z Co _z O ₄ ( Here, 0 <Z <2), LiCoPO ₄ , LiFePO _4, or a mixture thereof is mentioned. More preferably Li _x MO ₂ , wherein M is Ni, Co, or Mn, and x is 0.05 ≦ x ≦ 1.10.

Subsequently, the positive electrode is configured by binding the positive electrode active material to a positive electrode current collector, that is, a foil manufactured by aluminum, nickel, or a combination thereof.

The negative electrode active material may be a conventional negative electrode active material that can be used for the negative electrode of the conventional electrochemical device, non-limiting examples of lithium metal or lithium alloy, carbon, petroleum coke, activated carbon, Lithium adsorbents such as graphite or other carbons. The negative electrode is constituted by binding the negative electrode active material to a negative electrode current collector, that is, a foil made of copper, gold, nickel or a copper alloy or a combination thereof.

The separator is a polyethylene (polyethylene), a polypropylene (polypropylene) having a microporous structure, or a multilayer film produced by a combination of these films, or polyvinylidene fluoride (polyvinylidene fluoride), polyethylene oxide (polyethylene oxide) And polymer films for solid polymer electrolytes or gel polymer electrolytes such as polyacrylonitrile or polyvinylidene fluoride hexafluoropropylene copolymers.

The electrolyte is A ⁺ B ^- and may be a salt of such a structure, A ⁺ is Li ^+, Na ^+,, and comprising an alkali metal cation or an ion composed of a combination thereof, such as K ⁺ B ^- is PF ₆ ^{- _{, BF 4 -, Cl -,}} Br -, I -, ClO 4 -, ASF 6 -, CH 3 CO 2 -, CF 3 SO 3 -, N (CF 3 SO 2) 2 -, C (CF 2 SO 2 ) ₃ ^- and means a salt containing the same anion, ion consisting of a combination thereof. Specific examples of the lithium salt include propylene carbonate (PC), ethylene carbonate (EC), diethyl carbonate (DEC), dimethyl carbonate (DMC) and dipropyl carbonate (dipropyl). carbonate, DPC), dimethyl sulfoxide, acetonitrile, dimethoxyethane, diethoxyethane, tetrahydrofuran, N-methyl-2-pyrrolidone ( N-methyl-2-pyrrolidone (NMP), ethyl methyl carbonate (ethyl methyl carbonate, EMC), gamma butyrolactone (γ-butyrolactone) or dissolved in an organic solvent consisting of a mixture thereof is dissociated.

Hereinafter, the present invention will be described in detail through examples. However, the following examples are intended to illustrate the present invention and are not intended to limit the invention.

Comparative example  One

LG lithium ion cylindrical secondary battery (trade name: ICP18650, 2400mAh) was used. In this case, LiCoO ₂ was used as the positive electrode active material, graphite was used as the negative electrode active material, and a polypropylene separator was used as the separator, and a stainless steel battery can was used.

Example  One

As shown in FIG. 2, a battery having the same component as that of Comparative Example 1 was assembled except that a battery can having an embossed protrusion uniformly distributed on the inner surface of the battery can was used. At this time, the height of the embossed protrusion was 0.3 mm.

<Experiment>

The lithium ion cylindrical batteries prepared in Comparative Examples 1 and 1 were charged only 4.2V and then subjected to crushing experiments.

In the crushing test, a cell-shaped structure was installed under a 30 cm diameter disk, and the test was conducted by hydraulic pressure at a speed of 3 to 4 mm / sec until the pressure reached 3000 pounds, and the recorded temperature and voltage were observed. The results for Comparative Example 1 and Example 1 are shown in FIGS. 3 and 4, respectively.

As shown in FIG. 3, the size of the short circuit becomes wider and the voltage gradually decreases as the pressure of the cell increases, so that the heat generated in the local part rapidly rises in a short time. The battery will ignite.

However, as shown in FIG. 4, it can be seen that the battery of Example 1 has an instantaneous voltage drop due to a large area short circuit, and the maximum internal temperature of the battery also rises to less than 100 ° C. This is because, according to the present invention, an electric can formed with one or more protrusions on the inner surface causes a large area short circuit, thereby suppressing heat generation of the battery because the short circuit current is dispersed.

As described above, using the container with a protrusion formed on the inner surface in accordance with the present invention, it is possible to intentionally generate a short circuit by the protrusion when a predetermined pressure or more from the outside. As a result, the situation in which the electrochemical device becomes dangerous due to thermal runaway can be avoided, thereby ensuring the safety of the electrochemical device.

Claims (12)

In an electrochemical device in which an electrode assembly including at least one first electrode, at least one separator, and at least one second electrode is housed in a container, the container is made of metal and at least one protrusion is formed on an inner surface thereof. And a separator disposed at an outermost side adjacent to the protrusion, and the container is insulated from the first electrode and electrically connected to a second electrode by the separator disposed at the outermost side, and the protrusion is externally attached to the outermost electrode. An electrochemical device, characterized in that the intentionally rupture of the separator disposed in the outermost during the pressure pressurization that can rupture the separator disposed in the. The method of claim 1, wherein when the pressure is pressurized to rupture the separator disposed from the outside from the outside, the separator disposed intentionally arranged at the outermost part is ruptured by the at least one protrusion to distribute the short circuit current. Chemical element. delete delete delete The electrochemical device according to claim 1 or 2, wherein the electrode assembly is a wound electrode assembly in which a first separator, a first electrode, a second separator, and a second electrode are wound after lamination. The electrochemical device according to claim 1 or 2, wherein the electrode assembly is a stacked type in which at least one first electrode, at least one separator, and at least one second electrode are stacked. delete delete 3. An electrochemical device according to claim 1 or 2, wherein said container is an assembly having a can and a cap for sealing said can. The electrochemical device according to claim 1 or 2, wherein the protrusions are evenly distributed on the entire inner surface of the container. The electrochemical device according to claim 1 or 2, which is a lithium secondary battery.

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