KR20180100815A - Electrode for lithium secondary battery and Lithium secondary battery comprising the same - Google Patents

Abstract

The present invention provides an electrode for a lithium secondary battery for solving the phenomenon of clogging of a porous electrode and/or a separation membrane when forming a ceramic coating layer on an electrode for enhancing high-temperature stability of a secondary battery, and a lithium secondary battery comprising the same, and according to the present invention, there is an effect of preventing the phenomenon of clogging of the porous electrode and/or the separation membrane in case of danger such as internal heat, overcharge or internal short circuit.

Description

[0001] The present invention relates to an electrode for a lithium secondary battery,

The present invention relates to an electrode for a lithium secondary battery and a secondary battery having the electrode. More particularly, the present invention relates to a method for forming a ceramic coating layer on an electrode in order to enhance the high temperature stability of the secondary battery, An electrode for a lithium secondary battery and a secondary battery having the same.

In general, the secondary battery includes a nickel cadmium battery, a nickel metal hydride battery, a lithium ion battery, and a lithium ion polymer battery. Such a secondary battery is not only a compact product such as a digital camera, a P-DVD, an MP3P, a mobile phone, a PDA, a portable game device, a power tool and an e-bike, but also a large product requiring high output such as an electric car or a hybrid car, Power storage devices for storing power generation and renewable energy, and backup power storage devices.

The secondary battery may be classified according to how the electrode assembly having the anode / separator / cathode structure is formed. Typically, the jelly-roll having the structure in which the anode and the cathode are wrapped with the separator interposed therebetween, (Stacked) electrode assembly in which a plurality of positive electrodes and negative electrodes cut in units of a predetermined size are sequentially stacked with a separator interposed therebetween, a stacked (stacked) electrode assembly in which a predetermined unit of positive and negative electrodes are stacked A stack / folding type electrode assembly having a structure in which a bicell or full cell stacked with a capacitor is wound.

Recently, a pouch-shaped battery having a structure in which a stacked or stacked / folded electrode assembly is embedded in a pouch-shaped battery case of an aluminum laminate sheet has attracted a great deal of attention due to low manufacturing cost, small weight, And its usage is gradually increasing. Such a secondary battery generally comprises an electrode assembly in which a positive electrode plate and a negative electrode plate are sequentially laminated with a separator interposed therebetween, and a battery case which is a casing for accommodating the electrode assembly. At this time, a plurality of positive electrode tabs extending from a plurality of positive electrode plates and a plurality of negative electrode tabs extending from a plurality of negative electrode plates are formed in the electrode assembly, and the plurality of positive electrode tabs and the plurality of negative electrode tabs are respectively connected to positive lead Welded by an anode lead and an ultrasonic welder. Here, the plurality of positive electrode tabs and the plurality of negative electrode tabs constitute electrode tabs, and the positive electrode lead and negative electrode lead constitute electrode leads.

The positive electrode active material for a lithium secondary battery is a layered LiCoO ₂ . LiCoO ₂ is most widely used because it has excellent lifetime characteristics and charge / discharge efficiency, but its structural stability is low and thus it is limited to be applied to high capacity battery technology. Various lithium transition metal oxides such as LiNiO ₂ , LiMnO ₂ , LiMn ₂ O ₄ , LiFePO _4, and Li (NixCoyMnz) O ₂ have been developed as a cathode active material for replacing them. LiNiO ₂ has the advantage of exhibiting a high discharge capacity of a battery, but it is difficult to synthesize a simple solid phase reaction, and has a low thermal stability and low cycle characteristics. In addition, lithium manganese-based oxides such as LiMnO ₂ or LiMn ₂ O ₄ are excellent in thermal stability and low in cost, but have a problem of low capacity and low temperature characteristics. In particular, in the case of LiMn2O4, but a part to commercialize low cost products, due to Mn ^{+ 3} structure modification (Jahn-Teller distortion) due to the not good life property. In addition, LiFePO ₄ has been studied for hybrid electric vehicle (HEV) at a low cost and safety, but it is difficult to apply it to other fields due to its low conductivity.

Because of such circumstances, the material receiving the spotlight recently as a replacement cathode active material of LiCoO ₂ is Li (NixCoyMnz) O ₂ (In this case, the x, y, z is an atomic fraction of each independent oxide composition element, 0 <x 1, 0 <y? 1, 0 <z? 1, 0 <x + y + z? 1). This material is advantageous in that it can be used at a high capacity and high voltage at a lower cost than LiCoO ₂ , but has a disadvantage in that it has poor rate capability and a long lifetime at high temperature. It is necessary to maintain long-term life, which is safety with high energy and high output. It is required to maintain stable long-term life with high output. In order to secure stability in the environment such as heat generation, overcharge, and internal short-circuit during charging / discharging of a large number of cells in a pack or module unit, a separator for coating a ceramic powder with a polymer binder is used in the separator, There is still a risk of internal short circuit due to high heat shrinkage.

Korean Patent Laid-Open Publication No. 2015-0145046 discloses a surface protective film for a lithium electrode for a lithium secondary battery, wherein the protective film comprises an ion-exchangeable polymer composed of a polymer containing an anionic functional group dissociated in an electrolyte solution of the lithium secondary battery A surface protective film of a lithium electrode for a lithium secondary battery is disclosed. However, the composition of the film type and the slurry amount ratio is not disclosed.

Japanese Patent Application Laid-Open No. 1996-250110 discloses a method for producing an electrode plate for a non-aqueous electrolyte secondary battery by forming an active material layer on a surface of a metal substrate, wherein the active material layer is transferred from the transfer film on which the transferable active material layer is formed to the metal substrate surface And forming an electrode plate for a non-aqueous electrolyte secondary battery. However, a configuration in which a coating layer is transferred onto an anode at a high temperature and a high temperature of 100 占 폚 or more after coating a ceramic powder slurry on a PP or PET film has not been disclosed.

Korean Patent Laid-Open Publication No. 2005-0041661 discloses a negative active material layer of lithium metal or lithium alloy; And a protective film formed on the anode active material layer, wherein the protective film has a structure in which a linear polymer is permeated into a three-dimensionally crosslinked polymer network matrix. However, no configuration has been disclosed in which a ceramic powder slurry is coated on a PP or PET film, and the coating layer is transferred to the anode at a high temperature of 100 ° C or higher and a high pressure.

Japanese Patent Publication No. 4873281 discloses a process for forming an inorganic solid electrolyte thin film on a lithium-containing metal and a process for immediately covering the electrolyte thin film with a flexible protective sheet after forming the electrolyte thin film, And the step of coating the protective sheet are carried out in successive vacuum chambers. However, a configuration in which a coating layer is transferred onto an anode at a high temperature and a high temperature of 100 占 폚 or more after coating a ceramic powder slurry on a PP or PET film has not been disclosed.

In order to secure safety by applying a separator coated with a ceramic powder together with a polymer binder, the heat shrinkage ratio of the separator at high temperature is high, which causes a problem in battery performance such as an internal short circuit. To solve this problem, There is no description of an electrode for a lithium secondary battery in which a ceramic layer coated on an electrode is transferred at high pressure and a secondary battery having the same.

Korean Patent Laid-Open Publication No. 2015-0145046 Japanese Laid-Open Patent Publication No. 1996-250110 Korean Patent Publication No. 2005-0041661 Japanese Patent Publication No. 4873281

SUMMARY OF THE INVENTION It is a primary object of the present invention to solve the problems of the prior art as described above, in order to improve the high-temperature stability of a secondary battery, An electrode for a lithium secondary battery, and a secondary battery having the same.

It is another object of the present invention to provide a secondary battery having improved stability that can prevent an internal short circuit due to contact between an anode and a cathode even if the separator shrinks at a high temperature.

SUMMARY OF THE INVENTION The present invention has been conceived to solve the above-mentioned problems, and provides an electrode formed by transferring the ceramic powder layer at a predetermined temperature and / or pressure using a polymeric transfer film having a ceramic layer formed thereon.

The ceramic layer may include at least one selected from the group consisting of aluminum oxide (Al ₂ O ₃ ), silicon oxide (SiO ₂ ), and titanium dioxide (TiO ₂ ).

In addition, the polymeric transfer film may be formed using any one of high density polyethylene, low density polyethylene, linear low density polyethylene, ultrahigh molecular weight polyethylene, polypropylene, polyethylene terephthalate, polybutylene terephthalate, polyester, polyacetal, polyamide, polycarbonate, Ether ether ketone, polyether sulfone, polyphenylene oxide, polyphenylene sulfide, and polyethylene naphthalate, or a mixture of two or more thereof.

In addition, the high-temperature and high-pressure conditions can be carried out at a temperature of 60 to 180 캜 at a pressure of 0.1 kgf / cm ² to 100 kgf / cm ² .

Also, the transfer may be performed in an electrode rolling apparatus that winds up the polymer transfer film wound on the film feeding roll and the electrode wound on the feeding roll by loosening and laminating the electrodes, and winding the roll on a winding roll.

And a rolling roll for applying a heat and / or pressure to the polymer transfer film and the electrode to be laminated, and transferring the ceramic layer of the polymer transfer film onto the electrode to form a ceramic layer .

The secondary battery device may further include the electrode.

The secondary battery device may be selected from the group consisting of an electronic device, an electric vehicle, a hybrid vehicle, and a power storage device.

It is another object of the present invention to provide a ceramic slurry using a ceramic powder, a polymer binder and a solvent in a predetermined mixing ratio. A second step of coating the ceramic slurry on a polymeric transfer film; A third step of inserting the polymeric transfer film coated with the ceramic slurry and an electrode into a laminating roll at a predetermined temperature and / or pressure; And a fourth step of injecting an electrolyte after assembling the battery including the electrode formed in the third step; And a secondary cell manufacturing method.

The ceramic powder may include at least one selected from the group consisting of aluminum oxide (Al ₂ O ₃ ), silicon oxide (SiO ₂ ), and titanium dioxide (TiO ₂ ).

The slurry may include 10 to 20 parts by weight of the ceramic powder, 0.5 to 5 parts by weight of a polymer binder, and 5 to 15 parts by weight of a solvent.

Further, the predetermined temperature and / or pressure may be conducted at a temperature of 60 to 180 캜 at a pressure of 0.1 kgf / cm ² to 100 kgf / cm ² .

Also, the transfer may be performed in an electrode rolling apparatus that winds up the polymer transfer film wound on the film feeding roll and the electrode wound on the feeding roll by loosening and laminating the electrodes, and winding the roll on a winding roll.

And a rolling roll for applying a heat and / or pressure to the polymer transfer film and the electrode to be laminated, and transferring the ceramic layer of the polymer transfer film onto the electrode to form a ceramic layer .

According to the electrode for a lithium secondary battery and the secondary battery having the same according to the present invention, it is possible to eliminate the phenomenon that the porous electrode and / or the separator is clogged by the ceramic coating layer in a dangerous situation such as internal heat generation, overcharging or internal short circuit .

Further, the present invention has the effect of eliminating internal short circuit due to heat shrinkage of the separator.

In addition, the present invention has the effect of eliminating internal heat or the like by forming a ceramic layer on the electrode using transfer.

1 is a conceptual diagram of transferring a ceramic layer to an electrode using a transfer film including a ceramic layer according to an embodiment of the present invention.
FIG. 2 is a conceptual diagram showing that a ceramic layer is transferred to a transfer film including a ceramic layer by a rolling roll according to an embodiment of the present invention.
3 is a stability test result of a pouch cell formed through transfer according to an embodiment of the present invention.
FIG. 4 is a graph illustrating the relative capacity of an electrode formed through transfer according to an exemplary embodiment of the present invention.
5 is a conceptual diagram of a cross-section and a double-sided electrode in which a ceramic layer formed through transfer is formed according to an embodiment of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. However, the detailed description of known functions and configurations incorporated herein will be omitted when it may unnecessarily obscure the subject matter of the present invention.

The same reference numerals are used for portions having similar functions and functions throughout the drawings. Throughout the specification, when a part is connected to another part, it includes not only a case where it is directly connected but also a case where the other part is indirectly connected with another part in between. In addition, the inclusion of an element does not exclude other elements, but may include other elements, unless specifically stated otherwise.

The present invention will be described in detail with reference to the drawings.

1 is a conceptual diagram of transferring a ceramic layer to an electrode using a transfer film including a ceramic layer according to an embodiment of the present invention.

Referring to FIG. 1, an electrode rolling apparatus for forming a ceramic layer may be composed of a film feeding roll, an electrode feeding roll, a heater, a rolling roll, a rewinder, and a film recovery roll. The film feeding roll and the electrode feeding roll guide the transfer film and the electrode so that they can run along the traveling line. The transfer film and the electrode are heated while passing through the heater, and the heated transfer film and the electrode are rolled by the rolling rolls.

The rewinder cooperates with the film feeding roll and the electrode feeding roll to wind the electrode on which the ceramic layer is rolled.

Further, the film recovery roll is used to wind the film after transferring the ceramic layer. The heater emits near infrared rays in the range of 780 nanometers to 3 micrometers and the transfer film and electrodes are heated to near 60 degrees Celsius to 70 degrees Celsius by near infrared rays. The heated transfer film and electrode are rolled by rolling rolls to a rolling load in the range of 40 kN to 60 kN, which is a relatively small rolling load.

There is provided an electrode formed by transferring the ceramic powder layer at a predetermined temperature and / or pressure using a polymeric transfer film having a ceramic layer formed thereon.

The transfer may form a ceramic layer on one or both surfaces of the electrode.

The electrode may be an anode and / or a cathode. It may preferably be a positive electrode.

The ceramic layer may include at least one selected from the group consisting of aluminum oxide (Al ₂ O ₃ ), silicon oxide (SiO ₂ ), and titanium dioxide (TiO ₂ ).

In addition, the polymeric transfer film may be formed using any one of high density polyethylene, low density polyethylene, linear low density polyethylene, ultrahigh molecular weight polyethylene, polypropylene, polyethylene terephthalate, polybutylene terephthalate, polyester, polyacetal, polyamide, polycarbonate, Ether ether ketone, polyether sulfone, polyphenylene oxide, polyphenylene sulfide, and polyethylene naphthalate, or a mixture of two or more thereof.

In addition, the high-temperature and high-pressure conditions can be carried out at a temperature of 60 to 180 캜 at a pressure of 0.1 kgf / cm ² to 100 kgf / cm ² . The high-temperature and high-pressure conditions can be preferably carried out at a temperature of 80 to 120 ° C at a pressure of 0.2 kgf / cm ² to 10 kgf / cm ² . More preferably at a temperature of 90 DEG C, at a pressure of 0.3 kgf / cm &lt; ² &gt;. If the above conditions are exceeded, the transfer rate of the ceramic powder to the anode is lowered on the film.

Also, the transfer may be performed in an electrode rolling apparatus that winds up the polymer transfer film wound on the film feeding roll and the electrode wound on the feeding roll by loosening and laminating the electrodes, and winding the roll on a winding roll.

And a rolling roll for applying a heat and / or pressure to the polymer transfer film and the electrode to be laminated, and transferring the ceramic layer of the polymer transfer film onto the electrode to form a ceramic layer .

The secondary battery device may further include the electrode.

The secondary battery device may be selected from the group consisting of an electronic device, an electric vehicle, a hybrid vehicle, and a power storage device. The electronic device may be a mobile phone, a portable computer, a smart phone, a smart pad, or a netbook.

It is another object of the present invention to provide a ceramic slurry using a ceramic powder, a polymer binder and a solvent in a predetermined mixing ratio. A second step of coating the ceramic slurry on a polymeric transfer film; A third step of inserting the polymeric transfer film coated with the ceramic slurry and an electrode into a laminating roll at a predetermined temperature and / or pressure; And a fourth step of injecting an electrolyte after assembling the battery including the electrode formed in the third step; And a secondary cell manufacturing method.

The ceramic powder may include at least one selected from the group consisting of aluminum oxide (Al ₂ O ₃ ), silicon oxide (SiO ₂ ), and titanium dioxide (TiO ₂ ).

The slurry may include 10 to 20 parts by weight of the ceramic powder, 0.5 to 5 parts by weight of a polymer binder, and 5 to 15 parts by weight of a solvent. The slurry may preferably contain 12 to 18 parts by weight of the ceramic powder, 1 to 3 parts by weight of the polymer resin, and 8 to 12 parts by weight of the solvent, and more preferably, 16 parts by weight of the ceramic powder, 2 parts by weight of the polymer resin , And 9 parts by weight of a solvent. If the mixing ratio is exceeded, coating on the polymeric transfer film is not smoothly performed.

The ceramic may be aluminum oxide, the polymer resin may be PVDF, and the solvent may be acetone.

Further, the predetermined temperature and / or pressure may be conducted at a temperature of 60 to 180 캜 at a pressure of 0.1 kgf / cm ² to 100 kgf / cm ² .

Also, the transfer may be performed in an electrode rolling apparatus that winds up the polymer transfer film wound on the film feeding roll and the electrode wound on the feeding roll by loosening and laminating the electrodes, and winding the roll on a winding roll.

And a rolling roll for applying a heat and / or pressure to the polymer transfer film and the electrode to be laminated, and transferring the ceramic layer of the polymer transfer film onto the electrode to form a ceramic layer .

(Example 1)

Ceramic powder slurry on the anode was coated on the film, and a pouch cell fabricated by using the cathode was prepared. An electrode assembly was fabricated using a negative electrode and a PE separator manufactured using ordinary natural graphite. The ceramic powder was made of aluminum oxide and the ceramic slurry was made of 16 parts by weight of aluminum oxide, 2 parts by weight of PVDF and 9 parts by weight of acetone. The ceramic slurry was coated on a PET film and then transferred onto a positive electrode to prepare a positive electrode. The electrode assembly using the anode, separator, and cathode was sealed in an aluminum pouch to prepare a battery cell, and an electrolyte solution was injected to evaluate the cell stability performance.

The stability test was carried out at room temperature to evaluate the voltage change when the 3C pulse was applied for 10 seconds in the SOC50. The cell voltage of the 4.2V full charge cell was raised to 150 ° C in the temperature increasing chamber at 5 / And the state after maintenance was confirmed.

(Comparative Example 1)

The pouch cell assembled by using the general anode, the PE separator, and the negative electrode was fabricated in the portion where the ceramic powder of Example 1 was not applied.

(Comparative Example 2)

A pouch cell assembled using a general anode, a PE separator coated with a ceramic powder slurry, and a negative electrode to which the ceramic powder of Example 1 was not applied was fabricated. The ceramic powder used was aluminum oxide.

3 is a stability test result of a pouch cell formed through transfer according to an embodiment of the present invention.

As a result of the experiment, it was confirmed that an internal short circuit occurred in Comparative Examples 1 and 2. The end voltage of the experiment was 0.21 V in Comparative Example 1 and 2.3 V in Comparative Example 2, which was different from 4.115 V in Example 1.

(Example 2)

A positive electrode to which a ceramic layer was transferred under the same conditions as in Example 1 was fabricated. Li-metal and a coin-type battery were fabricated. After reaching 4.25 V at a constant current of 0.3 mA / cm ² , the current value reached 0.06 mA / cm ² The battery is charged at a constant current of 0.3 mA / cm &lt; ² &gt; based on the capacity up to 3V. Next, the discharge capacity was checked in the order of 0.3, 0.6, 1.5, and 3 mA / cm ² , and the relative capacity was compared with the reference capacity in%.

(Comparative Example 3)

The ceramic powder of Example 2 was different from that of the non-applied portion, and a coin reversed paper was fabricated using a general anode, a PE separator, and a cathode.

As a result of the experiment, it can be seen that the relative capacity of Comparative Example 3 is lower than that of Example 2 in the order of 0.3, 0.6, 1.5, and 3 mA / cm ² .

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it is evident that many alternatives, modifications and variations will be apparent to those skilled in the art in light of the above teachings. It is to be understood that such modified embodiments are also within the scope of protection of the present invention as defined by the appended claims.

100: Film feeding roll
110: Polymeric transfer film
120: Ceramic powder layer
200: Electrode feeding roll
210: electrode
211: electrode plate
212: electrode active material layer
300: heater
400a, 400b: rolling roll
500: Rewinder
600: film recovery roll

Claims (14)

An electrode formed by transferring the ceramic powder layer at a predetermined temperature and / or pressure using a polymeric transfer film having a ceramic layer formed thereon.
The method according to claim 1,
Wherein the ceramic layer comprises at least one selected from the group consisting of aluminum oxide (Al ₂ O ₃ ), silicon oxide (SiO ₂ ), and titanium dioxide (TiO ₂ ).
The method according to claim 1,
The polymeric transfer film may be formed of a polymeric material such as high density polyethylene, low density polyethylene, linear low density polyethylene, ultrahigh molecular weight polyethylene, polypropylene, polyethylene terephthalate, polybutylene terephthalate, polyester, polyacetal, polyamide, polycarbonate, Wherein the electrolyte is one selected from the group consisting of ketone, polyethersulfone, polyphenylene oxide, polyphenylene sulfide, and polyethylene naphthalate, or a mixture of two or more thereof.
The method according to claim 1,
Wherein the high-temperature and high-pressure condition is carried out at a temperature of 60 to 180 캜 at a pressure of 0.1 kgf / cm ² to 100 kgf / cm ² .
The method of claim 4,
Wherein the transferring is performed in an electrode rolling apparatus for winding the polymer transcription film wound on the film feeding roll and the electrode wound on the feeding roll by loosening and laminating the electrode, and winding the polymer on the winding roll.
The method of claim 5,
And a rolling roll for applying a heat and / or a pressure to the polymer transfer film and the electrode to be laminated, and transferring the ceramic layer of the polymer transfer film onto the electrode to form a ceramic layer Characterized by the electrodes.
[Claim 7] The method according to any one of claims 1 to 6,
And the electrode.
The method of claim 7,
Wherein the secondary battery device is selected from the group consisting of an electronic device, an electric vehicle, a hybrid vehicle, and a power storage device.
A first step of preparing a ceramic slurry using a ceramic powder, a polymer binder and a solvent in a predetermined mixing ratio;
A second step of coating the ceramic slurry on a polymeric transfer film;
A third step of inserting the polymeric transfer film coated with the ceramic slurry and an electrode into a laminating roll at a predetermined temperature and / or pressure; And
A fourth step of injecting an electrolyte after assembling the battery including the electrode formed in the third step;
&Lt; / RTI &gt;
The method of claim 9,
Wherein the ceramic powder comprises at least one selected from the group consisting of aluminum oxide (Al ₂ O ₃ ), silicon oxide (SiO ₂ ), and titanium dioxide (TiO ₂ ).
The method of claim 9,
Wherein the slurry comprises 10 to 20 parts by weight of the ceramic powder, 0.5 to 5 parts by weight of a polymer binder, and 5 to 15 parts by weight of a solvent.
The method of claim 9,
Wherein the predetermined temperature and / or pressure is maintained at a temperature of 60 to 180 캜 at a pressure of 0.1 kgf / cm ² to 100 kgf / cm ² .
The method of claim 9,
Wherein the transferring is carried out in an electrode rolling apparatus for winding the polymer transcription film wound on the film feeding roll and the electrode wrapped around the feeding roll by rolling in a system in which the electrode is wound and wound on a winding roll, Gt;
14. The method of claim 13,
And a rolling roll for applying a heat and / or a pressure to the polymer transfer film and the electrode to be laminated, and transferring the ceramic layer of the polymer transfer film onto the electrode to form a ceramic layer Wherein the secondary battery is manufactured by a method comprising the steps of:

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