KR101542420B1 - Lithium Ion Battery and Lithium and Manufacturing Method thereof - Google Patents

Abstract

The present invention relates to a lithium secondary battery and a method of manufacturing the same. The present invention relates to a lithium secondary battery and a method of manufacturing the same, And a coating formed on the anode by a side reaction corresponding to the sulfonic material, wherein the cathode is formed of Li ₂ [Ni _{0.6 to 0.9} Co _{0.2 to 0.05} Mn _{0.2 to 0.05} ] O ₂ , and a process for producing the same.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to a lithium secondary battery,

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a lithium secondary battery and a method of manufacturing the same, and more particularly, to a lithium secondary battery having improved anode lifetime and discharge capacity, a lithium secondary battery including the lithium secondary battery and a method of manufacturing the same.

As consumers' demands have changed due to digitization and high performance of electronic products, market demand is changing due to the development of batteries with high capacity due to thinness, light weight and high energy density. In addition, in order to cope with future energy and environmental problems, hybrid electric vehicles, electric vehicles, and fuel cell vehicles are being actively developed, and it is required to increase the size of batteries for automobile power sources.

Lithium secondary batteries have been put to practical use as batteries that can be miniaturized and lightweight and can be charged and discharged with a high capacity. Lithium rechargeable batteries have been commercialized as main power sources for small devices such as mobile phones and notebook computers, and their application to large-sized devices such as electric vehicles and energy storage devices is becoming more visible as the market continues to expand. Such a lithium secondary battery is characterized in that it is exposed to a high temperature environment in the process of being applied to a large-sized apparatus. The lithium secondary battery causes a large deterioration in the performance of the battery because it causes a large amount of oxygen at high temperature and rapid deterioration of the anode material due to elution of the metal.

Accordingly, an object of the present invention is to solve the problem of degradation of electrochemical performance due to deterioration of a lithium composite metal anode at a high temperature by using a sulfone-based electrolyte as an additive or a sole electrolyte to form a film on the surface of the anode, And a lithium secondary battery comprising the lithium secondary battery and a method of manufacturing the same, which can improve safety at a high temperature of a battery composed of a lithium composite metal cathode material by suppressing side reactions occurring between the lithium secondary battery and the anode.

For example, in order to suppress swelling of a battery at a high temperature, the present invention forms a film obtained from an electrochemical oxidation reaction of a sulfonic material on the surface of a cathode, thereby minimizing side reaction through continuous contact of the organic electrolyte and the anode surface, A lithium secondary battery including the lithium secondary battery, and a method of manufacturing the same.

In order to accomplish the above object, the present invention provides a lithium secondary battery component comprising a lithium composite metal anode, and a coating formed on the anode and formed by a side reaction corresponding to a sulfonic substance.

And the coating has an orientation characteristic in a certain direction.

The electrolyte is EC (ethylene carbonate): characterized in that a mixture of 7 + 1.5M PS (1,3-propanesultone ) 2% by weight of the _{LiPF 6: EMC (ethyl methyl carbonate} ) = 3.

The positive electrode is characterized by being Li ₂ [Ni _{0.6 to 0.9} Co _{0.2 to 0.05} Mn _{0.2 to 0.05} ] O ₂ .

The sulfonic material includes sultone compounds represented by the formula (1), sulfone compounds represented by the formula (2) or sulfonate compounds represented by the formula (3).

(화학식 1, R1은 탄소수 1 내지 5의 알킬기 또는 알케닐기)

(Wherein R 1 is an alkyl group or an alkenyl group having 1 to 5 carbon atoms)

(화학식 2, R2 및 R2′는 수소 원자, 할로겐 원자, 탄소수 1 내지 5의 알킬기 또는 알케닐기, 탄소수 1 내지 5의 알킬기 또는 할로겐 원자로 치환 또는 비치환된 페닐기 또는 페녹시기로 이루어진 군으로부터 선택되며, 서로 독립적임)

(2), R 2 and R 2 'are selected from the group consisting of a hydrogen atom, a halogen atom, an alkyl group or an alkenyl group having 1 to 5 carbon atoms, an alkyl group having 1 to 5 carbon atoms, a phenyl group substituted or unsubstituted with a halogen atom, Independent from each other)

(화학식 3, R2 및 R2′는 수소 원자, 할로겐 원자, 탄소수 1 내지 5의 알킬기 또는 알케닐기, 탄소수 1 내지 5의 알킬기 또는 할로겐 원자로 치환 또는 비치환된 페닐기 또는 페녹시기로 이루어진 군으로부터 선택되며, 서로 독립적임)

(3), R 2 and R 2 'are selected from the group consisting of a hydrogen atom, a halogen atom, an alkyl group or an alkenyl group having 1 to 5 carbon atoms, an alkyl group having 1 to 5 carbon atoms or a phenyl group or a phenoxy group substituted or unsubstituted with a halogen atom, Independent from each other)

According to another aspect of the present invention, there is provided a lithium secondary battery including a case, an electrode unit disposed at an inner side of the case at a predetermined interval and including a lithium composite metal anode, and a separator disposed between the plurality of electrode units and an electrolytic solution An electrolyte layer, and a coating formed on the anode and formed by a side reaction corresponding to a sulfonic material.

The present invention also relates to a process for forming a film by depositing an electrode portion including a positive electrode of a lithium metal composite material in an electrolyte solution to form a film, disposing a plurality of electrode portions including the coated electrode on the inside of the case, A step of disposing a separator between the electrode parts, and a step of injecting an electrolyte solution mixed with at least a part of the sulfonic material into the case to form an electrolyte layer. .

The electrolyte solution is the same as the electrolyte solution injected for forming the electrolyte layer.

The method according to any one of the preceding claims, further comprising the step of orienting the film so that the film has a predetermined direction, wherein the orienting process includes flowing the electrolyte in which the electrode part has been settled at a constant flow rate while supplying power to the anode, And moving the electrode part settled in the electrolyte solution.

According to the lithium secondary battery composition of the present invention, a lithium secondary battery including the lithium secondary battery, and a method of manufacturing the same, the present invention provides a lithium secondary battery comprising a sulfonic material as an electrolyte additive or a single electrolyte, Lt; RTI ID = 0.0 > and / or < / RTI > improved lifetime characteristics due to this.

1 is a view for explaining a method of manufacturing a lithium secondary battery according to an embodiment of the present invention.
2 is a view for explaining a method of manufacturing a lithium secondary battery according to another embodiment of the present invention.
3 is a view illustrating a configuration of a lithium secondary battery according to an embodiment of the present invention.
Fig. 4 is a graph showing evaluation of physical properties of Examples and Comparative Examples of the present invention.
FIG. 5 is a graph showing an electrochemical stability evaluation of Examples and Comparative Examples of the present invention. FIG.
6 is a graph showing the high-temperature lifetime characteristics of the pull cells of Examples and Comparative Examples of the present invention.
FIG. 7 is a graph showing cell thickness measurement results obtained after evaluating the full cell lifetime characteristics of Examples and Comparative Examples of the present invention. FIG.
FIG. 8 is a diagram showing an SEM analysis after evaluating the life characteristics of a full-cell according to Examples and Comparative Examples of the present invention. FIG.
FIGS. 9A and 9B are graphs showing the anode impedance analysis after evaluating the pull cell lifetime characteristics of the embodiment of the present invention and the comparative examples. FIG.
10 is a graph showing FT-IR analysis after evaluating the life characteristics of a full-cell of Examples and Comparative Examples of the present invention.

In the following description, only parts necessary for understanding the operation according to the embodiment of the present invention will be described, and the description of other parts will be omitted so as not to disturb the gist of the present invention.

Also, the terms and words used in the present specification and claims should not be construed to be limited to ordinary or dictionary meanings, and the inventor is not limited to the concept of terms in order to describe his invention in the best way. It should be construed in accordance with the meaning and concept consistent with the technical idea of the present invention based on the principle that it can be properly defined. Therefore, the embodiments described in the present specification and the configurations shown in the drawings are merely one preferred embodiment of the present invention, and not all of the technical ideas of the present invention are described. Therefore, It is to be understood that equivalents and modifications are possible.

Embodiments of the present invention will now be described in detail with reference to the accompanying drawings.

1 is a view illustrating a method of manufacturing a lithium secondary battery according to an embodiment of the present invention.

Referring to FIG. 1, in the method of manufacturing a lithium secondary battery of the present invention, a lithium composite metal anode and an anode are first formed on a current collector plate in step S101. At this time, a plurality of electrode substructures may be arranged on the front and rear surfaces of the collector. Here, the lithium composite metal anode may be a nickel excess anode. For example, the nickel overbased anode may be Li ₂ [Ni _0.6 Co _0.2 Mn _0.2 ] O ₂ . Here, the nickel weight in the nickel excess-based anode may be 0.6 to 0.9. The ratio of cobalt and manganese can be changed depending on the nickel weight conversion. For example, the nickel excess-based anode may be Li ₂ [Ni _0.6-0.9 Co _0.2-0.05 Mn _0.2-0.05 ] O ₂ . The cathode may also be graphite.

In step S103, the plurality of electrode parts, in which the electrodes are arranged in the shape of the electrode plate, can be arranged in a state in which they are maintained at a constant interval. The number, size, and shape of the plurality of electrode units may vary according to the purpose of using the lithium secondary battery 100 of the present invention.

In step S105, a separation membrane is disposed between the plurality of electrode units. The separator may be a polyethylene separator. In step S107, a plurality of electrode units on which the separation membrane is disposed are inserted into the case. Then, in step S109, an electrolyte solution prepared according to an embodiment of the present invention is impregnated between the plurality of electrode parts to form an electrolyte layer between the plurality of electrode parts to provide a full cell or a half cell structure.

In this case, an electrolyte solution containing a lithium salt may be used, and an electrolyte solution having an appropriate lithium salt concentration may be used. Here, the concentration of the lithium salt may vary depending on the size and thickness of the lithium secondary battery and the purpose of use, and may be experimentally adopted. In particular, the electrolyte solution used in the present invention may use a sulfonic material as an electrolyte additive or an electrolyte. More specifically, the electrolyte is prepared by mixing ethylene (ethylene carbonate): EMC (ethyl methyl carbonate) = 3: 7 + 1.15M LiPF ₆ as a basic electrolyte and 2 wt% of 1,3-propanesultone To produce an electrolyte.

The lithium secondary battery manufactured by the above-described method can be charged under a constant voltage and current condition so as to be formed on the lithium composite metal system, for example, a nickel overbased anode. Here, the magnitude of the constant voltage and current can be experimentally changed depending on the size and capacity of the rechargeable lithium secondary battery. However, the constant voltage and current can be experimentally defined to form a coating having an appropriate thickness on the anode by a side reaction of the electrolyte solution.

2 is a view illustrating a method of manufacturing a lithium secondary battery according to another embodiment of the present invention.

Referring to FIG. 2, in the method of manufacturing a lithium secondary battery of the present invention, a positive electrode and a negative electrode may be provided in step S201. Here, the positive electrode may be a lithium composite metal positive electrode, and the negative electrode may be a grahite material. The lithium composite metal anode may be a nickel excess anode. For example, the nickel overbased anode may be Li ₂ [Ni _0.6 Co _0.2 Mn _0.2 ] O ₂ . Here, the nickel weight in the nickel excess-based anode may be 0.6 to 0.9. The ratio of cobalt and manganese can be changed depending on the nickel weight conversion.

Next, in step S203, an electrode to be used as an anode is deposited on the electrolyte prepared according to the embodiment of the present invention. Here, the electrolytic solution may be the same electrolytic solution as the electrolytic solution injected after the formation of the separation membrane. For example, as described above, EC (ethylene carbonate): EMC (ethyl methyl carbonate) = 3: 7 + 1M LiPF ₆ is used as a basic electrolyte, and 2 wt% of 1,3-propanesultone It may be a mixed electrolyte.

Then, in step S205, power is supplied to the anode to generate a side reaction by the electrolyte, thereby forming a coating on the surface of the anode in accordance with the side reaction of the electrolyte. In this process, the thickness of the coating formed on the surface of the anode can be experimentally defined depending on the size and capacity of the lithium secondary battery to be manufactured, the characteristics of various constituents, the arrangement environment, and the like. However, it is preferable that the thickness of the coating formed on the anode is such that the deterioration of storage and release of lithium ions through the anode is minimized. On the other hand, in the process of forming the film of the anode, an environment in which the electrolyte in which the anode is deposited can flow with a constant flow rate can be provided. Accordingly, the electrolyte mobility can be applied to the surface of the anode by the flow rate of the electrolyte during the process of forming the coating on the anode. As a result, the film formed on the anode may have a property of being oriented in a certain direction by the flow of the electrolyte solution. As the film formed on the anode is oriented, it is possible to provide more uniform and more stable characteristics during desorption and occlusion of ions while minimizing side reactions with the electrolyte.

Although the environment in which the electrolyte flows is described in the above description, the electrolyte solution may be kept stationary and provide an environment in which the anode moves in a certain direction in a state where it is deposited in the electrolyte solution. The anode may be manufactured in the form of an electrode plate, but it may be manufactured in a cylindrical shape and then rotated within the electrolyte during the film formation period. When a film is formed while the anolyte-deposited anode rotates at a constant speed, a nanostructure having uniform orientation characteristics can be formed on the surface of the anode as a film.

Then, in step S207, the electrode parts including the positive electrode and the negative electrode with the film as described above are formed on the current collector plate. At this time, a plurality of electrode substructures including at least one of the positive electrode and the negative electrode disposed on the front and rear surfaces of the collector may be provided. In step S209, a separation membrane is disposed between the plurality of electrode units. In step S211, a plurality of electrode units in which the separation membrane is disposed are inserted and arranged inside the case. In step S213, the prepared electrolyte is impregnated between the plurality of electrode parts to form an electrolyte layer between the plurality of electrode parts to provide a full-cell or half-cell structure. As described above, the electrolyte used may be a sulfonic material as an electrolyte additive or an electrolyte.

The lithium secondary battery manufactured through the above-described manufacturing method can independently form a film on the nickel over-mass anode, thereby forming the film forming process more precisely and uniformly according to the intention of the manufacturer. Further, an orientation film may be formed by adding a film orientation process in the film formation process of the anode.

3 is a schematic view of a lithium secondary battery 100 according to an embodiment of the present invention

3, the lithium secondary battery 100 of the present invention includes a first electrode unit 110, a second electrode unit 120, an electrolyte layer 40, a separation membrane 50, and a case 70 Lt; / RTI >

In the lithium secondary battery 100 of the present invention having such a structure, the electrolyte layer 40 may be formed using an electrolyte solution containing at least a part of a sulfonic material. Accordingly, the lithium secondary battery 100 of the present invention can suppress a side reaction between an additional positive electrode and an electrolyte by forming a film by side reaction of the electrolyte on the lithium composite metal type anode during the initial charging period.

The first electrode unit 110 is spaced apart from the second electrode unit 120 and disposed to face each other. The first electrode unit 110 may have a current collector 10 at the center thereof and a cathode or an anode may be formed on the front and rear surfaces of the current collector 10. In the drawing, the positive electrodes 21 and 22 are formed on both surfaces of the current collector 10. However, the present invention is not limited thereto. That is, the first electrode unit 110 of the lithium secondary battery 100 may include an electrode unit having a cathode according to the designer's intention. On the other hand, the anodes 21 and 22 may be formed in a form in which a film is formed in advance according to a manufacturing process. The coating film formed on the anode may have orientation properties.

The current collector 10 disposed at the center of the first electrode unit 110 may be made of a porous metal. For example, the current collector 10 may be a two-dimensional expanded foil, a punched foil, or a thin plate without pores as a current collector. Specifically, the current collector 10 may be made of aluminum or titanium titanium foil, an expanded aluminum or titanium foil collector, or other punched aluminum or titanium foil. The current collector 10 may have a three-dimensional structure. The material of the current collector 10 may be Ni, Cu, SUS, Ti, V, Cr, (Mn), iron (Fe), cobalt (Co), zinc (Zn), molybdenum (Mo), tungsten (W), silver (Ag), gold (Au), ruthenium (Ru) , Iridium (Ir), aluminum (Al), tin (Sn), bismuth (Bi), antimony (Sb) and the like.

The material for forming the positive electrodes 21 and 22 may include 5 to 20 wt% of the cathode active material and 80 to 95 wt% of the carbon-based material. At this time, the cathode active material may be a metal thin film of various types including lithium or a composite material to which a metal ion is added. For example, the cathode active material may be a composite material in which metal ions are added to LiCoO ₂ , LiMn ₂ O ₄ , LiNiO _{2, and} LiFePO ₄ . In the embodiment of the present invention, the anode 21 and the anode 22 may be made of, for example, a nickel-based anode as a lithium composite metal system.

In order to manufacture the positive electrodes 21 and 22 formed on the first electrode unit 110, a slurry is formed by combining the positive electrode active material, the conductive material, the binder, and the like, 10 according to a method of forming a uniform electrode. The positive electrodes 21 and 22 may be provided on the current collector 10 in the form of an electrode plate. In addition, a film forming process may be added as described above in the anode manufacturing process, and a film forming process may be applied in the film forming process. The film orientation process may include any one of a process of flowing the electrolyte after fixing the anode and a process of moving the anode after fixing the electrolyte.

Here, the slurry prepared for the production of the positive electrode plate is prepared by adding to the powder of the positive electrode active material a mixture of one or more kinds of additives such as a conductive material (carbonaceous material), a binder, a filler, a dispersant, Or may be prepared by adding two or more kinds of additive components and a suitable solvent (organic solvent). The thus obtained slurry or paste is coated on a collector corresponding to the electrode supporting substrate by using the doctor blade method and dried, and then pressed with a rolling roll or the like to be used as a cathode plate. When the anode plate is formed by coating or rolling on a current collector, a process of depositing a current collector on which a cathode plate is formed and then forming a film may be applied. That is, the film formation process may be changed to a process after the anode plate is formed on the current collector.

Here, graphite, carbon black, acetylene black, Ketjen Black, carbon fiber, metal powder and the like may be used as the conductive material (carbon-based material) used as needed. More specifically, the conductive material used for forming the first electrode unit 110 and the second electrode unit 120 for a lithium secondary battery is a conductive material having a conductive shape and having no pores capable of forming an electric double layer, Carbon black, and specific examples thereof include conductive carbon blacks such as furnace black, acetylene black, and ketjen black. Of these, acetylene black and furnace black are preferred.

As the binder, PVdF, polyethylene or the like can be used. In more detail, the binder for a lithium secondary battery of the present invention may be a compound capable of bonding an electrode active material and a conductive material to each other, and various materials may be used. In particular, the binder may be a dispersion type binder having properties of being dispersed in a solvent. Such a dispersion type binder may, for example, be a polymer compound such as a fluoropolymer, a diene polymer, an acrylate polymer, a polyimide, a polyamide or a polyurethane polymer, and a fluoropolymer, a diene polymer or an acrylate polymer is preferable , A diene polymer or an acrylate polymer, and the like. Such a binder provides an advantage that the withstand voltage and energy density of the lithium secondary battery can be increased.

Herein, the diene polymer may be a conjugated diene copolymer such as a conjugated diene homopolymer such as polybutadiene or polyisoprene, an aromatic vinyl o-conjugated diene copolymer such as carboxy-denatured styrene-butadiene copolymer (SBR), or acrylonitrile-butadiene copolymer Vinyl ㅇ conjugated diene copolymer, hydrogenated SBR, hydrogenated NBR, and the like. And the acrylate polymer is selected from the group consisting of ethyl acrylate, propyl acrylate, isopropyl acrylate, n-butyl acrylate, isobutyl acrylate, t-butyl acrylate, n-amyl acrylate, Acrylate such as acrylic acid novolac, nonyl acrylate, lauryl acrylate and stearyl acrylate; acrylates such as ethyl methacrylate, propyl methacrylate, isopropyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, t-butyl acrylate, n-amyl methacrylate, n-amyl methacrylate, n-nylon methacrylate, 2-ethylhexyl methacrylate, octyl methacrylate, isodecyl methacrylate, lauryl methacrylate, Acrylonitrile, methacrylonitrile, methacrylonitrile, methacrylonitrile, methacrylonitrile, methacrylonitrile, and the like.

The second electrode unit 120 is disposed at a predetermined distance from the first electrode unit 110 and faces the first electrode unit 110. Particularly, the second electrode part 120 may have an electrode having a different polarity from the electrode formed on the first electrode part 110 on the surface facing the first electrode part 110. For example, as described above, when the first and second electrode units 110 and 220 are formed with cathodes 21 and 22, the cathodes 31 and 32 may be disposed on the second electrode unit 120. The second electrode unit 120 may include a current collector 10 disposed at a central portion similar to the first electrode unit 110 and electrodes having a predetermined polarity disposed at front and rear surfaces of the current collector 10.

The cathodes 31 and 32 formed on the second electrode unit 120 constitute a slurry by combining the negative electrode active material, the conductive material and the binder and form a slurry on the current collector 10 The electrode may be formed according to a method of forming a constant electrode. The negative electrode active material may be at least one selected from the group consisting of crystalline or amorphous carbon such as artificial graphite, natural graphite, graphitized carbon fiber, graphitized mesocarbon microbead, petroleum coke, resinous body, carbon fiber and pyrolysis carbon . In the embodiment of the present invention, graphite was used as a cathode.

The electrolyte layer 40 is composed of an electrolytic solution and a solvent. For example, the electrolyte layer 40 can be made of a non-aqueous liquid electrolyte in which a lithium salt is dissolved in an organic solvent, an inorganic solid electrolyte, a composite material of an inorganic solid electrolyte, and the like. For example, the electrolyte layer 40 of the present invention may be formed of a material capable of forming a film of a predetermined thickness on the anode.

As the solvent of the non-aqueous liquid electrolyte, a carbonate, an ester, an ether or a ketone can be used. Examples of the carbonate include dimethyl carbonate (DMC), diethyl carbonate (DEC), dipropyl carbonate (DPC), methyl propyl carbonate (MPC), ethyl propyl carbonate (EPC), ethyl methyl carbonate (EMC) , Propylene carbonate (PC), butylene carbonate (BC), and the like. Examples of esters include butyrolactone (BL), decanolide, valerolactone, mevalonolactone, caprolactone, n-methyl acetate, n-ethyl acetate, n- Propyl acetate and the like can be used. As the ether, dibutyl ether and the like can be used. As the ketone, polymethyl vinyl ketone can be used. The non-aqueous liquid electrolyte according to the present invention is not limited to the kind of the non-aqueous organic solvent. At least some of the electrolytic solution used in the examples and comparative examples of the present invention may be a certain ratio of ethyl methyl carbonate and ethylene carbonate as described above.

Examples of the lithium salt in the nonaqueous _{electrolyte, LiPF 6, LiBF 4, LiSbF} 6, LiAsF 6, LiClO 4, LiCF 3 SO 3, LiN (CF 3 SO 2) 2, LiN (C 2 F 5 SO 2) 2, LiAlO 4 , LiAlCl ₄ , LiN (C _x F _2x + 1 SO ₂ ) (C _y F _2x + 1 SO ₂ ) wherein x and y are natural numbers, and LiSO ₃ CF ₃ . And mixtures thereof. In particular, the electrolytic solution of the present invention can be applied with 1.5M LiPF ₆ . In the electrolyte of the present invention, 2 wt% PS (1,3 propanesultone), which is a sulfonic material, may be mixed to form a coating film of the positive electrode.

Here, the sulfonic substance may be a sultone, a sulfone, a sulfonate or a mixture thereof.

The sultone compound is a saturated hydrocarbon or an unsaturated hydrocarbon sulphone represented by the following formula (1), and examples thereof include propane sultone (PS), propenesol, ethylsaltone, butenesulfone and the like.

In the general formula (1), R 1 is an alkyl group or an alkenyl group having 1 to 5 carbon atoms.

The sulfone compound is represented by the following formula (2), for example, dimethyl sulfone, dimethyl sulfone or divinyl sulfone.

In the general formula (2), R 2 and R 2 'are selected from the group consisting of a hydrogen atom, a halogen atom, an alkyl group or an alkenyl group having 1 to 5 carbon atoms, an alkyl group having 1 to 5 carbon atoms or a phenyl group substituted or unsubstituted with a halogen atom or a phenoxy group , Independent of each other.

The sulfonate compound is represented by the following formula (3), for example, methyl methanesulfonate, ethyl methanesulfonate, and the like.

In formula (3), R 2 and R 2 'are selected from the group consisting of a hydrogen atom, a halogen atom, an alkyl group or an alkenyl group having 1 to 5 carbon atoms, an alkyl group having 1 to 5 carbon atoms or a phenyl group substituted or unsubstituted with a halogen atom or a phenoxy group , Independent of each other.

The separator 50 may be formed of a material capable of insulating between the electrode units 110 and 120 for a lithium secondary battery and allowing positive and negative ions to pass therethrough. The separator 50 may be composed of a polyolefin such as polyethylene or polypropylene, a nonwoven fabric or nonwoven fabric made of rayon or glass fiber, or a porous film mainly composed of pulp called electrolytic capacitor paper. The thickness of the separation membrane 50 may be appropriately selected depending on the purpose of use.

The case 70 includes signal lines that surround the electrode units 110 and 120 and the electrolyte layer 40 and the separator 50 and electrically connect the electrode units 110 and 120, . The case 70 may be formed of a structure sealing the above-described structures, and may be made of a material having corrosion resistance to prevent corrosion of the electrolyte layer 40 due to electrolyte or the like. The case 70 can be formed into various shapes according to the shape of the product to which the lithium secondary battery 100 of the present invention is applied.

Meanwhile, the lithium secondary battery 100 according to the present invention may be formed into a case 70 to be filled with an electrolytic solution after performing a form preparation work such as winding, laminating or folding as necessary, and injecting an electrolyte solution into the case 70 Thereby blocking the entrance. Alternatively, the lithium secondary battery 100 may be manufactured by impregnating the structures with the electrolytic solution in advance to form the electrolyte layer 40, and then housing the structure in which the electrolyte layer 40 is formed, in the case 70. Here, the case 70 may be formed of any one of various shapes such as a coin shape, a cylindrical shape, a rectangular shape, a button, a sheet, and a pouch shape.

FIG. 4 is a graph showing the physical property evaluation of Examples and Comparative Examples of the present invention, and FIG. 5 is a graph showing an electrochemical stability evaluation of Examples and Comparative Examples of the present invention.

In the present invention, the application of a lithium secondary battery is proceeded by using a sulfonic material as an electrolyte additive or an electrolyte. More specifically, as a basic electrolyte, EC (ethylene carbonate): EMC (ethyl methyl carbonate) = 3: 7 + 1.15M LiPF ₆ was selected and 2 wt% of PS (1,3-propanesultone) . In addition, as a comparative example, an electrolyte containing no additive and 2% by weight of VC (vinylene carbonate), SN (succinonitrile) and PST (1,3-propenesultone) Ion conductivity was measured to confirm the physical and chemical performance of the electrochemical evaluation examples and comparative examples, and the ionic conductivity and LSV (linear sweep voltammetry) were measured to confirm the electrochemical performance.

Referring to FIGS. 4 and 5, there was no significant difference according to the presence or absence of additive as a result of ionic conductivity measurement. The electrochemical stability was evaluated by measuring the LSV of the electrolyte prepared by using glassy carbon as the working electrode and the lithium metal as the reference electrode and the counter electrode. As a result, the current flow by the oxidation reaction was observed at around 4.2V. Particularly, in the case of the PS material, a sudden increase in the current was confirmed, which means that the decomposition reaction due to the oxidation reaction is continuously generated in the process of raising the voltage of the PS material, which indicates that a film can be formed on the surface of the anode .

6 is a graph showing the high-temperature lifetime characteristics of the pull cells of Examples and Comparative Examples of the present invention.

Referring to FIG. 6, Li ₂ [Ni _0.6 Co _0.2 Mn _0.2 ] O ₂ material was used for the positive electrode, graphite was used for the negative electrode, and polyethylene separator was used for the negative electrode The evaluation was conducted. Here, the nickel specific gravity can be changed within the range of 0.6 to 0.9, and the specific gravity of other metals such as Co, Mn, etc. can be changed according to the change of the specific gravity of nickel.

The electrochemical evaluation was performed by fabricating a 3450-size pouch cell (3.4 cm x 5.0 cm), and the voltage range was conducted at a temperature of 60 ^° C by applying a current density of 3.0 to 4.2 V and a current density of 0.5 C-rate. In the case of the first charge / discharge curve, it is confirmed that the capacity close to the designed value is expressed regardless of the kind of the electrolyte. However, it can be confirmed that the lifetime characteristics are different according to the electrolyte type as the charge-discharge progresses. When the additive was not included, it was confirmed that the life characteristics after 50 cycles of charging and discharging were significantly lowered, and that the sulfone additive (PS and PST) exhibited an excellent life maintaining rate compared to other additives.

FIG. 7 is a graph showing cell thickness measurement results obtained after evaluating the full cell lifetime characteristics of Examples and Comparative Examples of the present invention. FIG. After the charge and discharge at the high temperature was completed, the cells were collected and the change in the thickness before and after the evaluation was measured by a thickness meter.

Referring to FIG. 7, it was confirmed that the cell containing the sulfonic additive showed a relatively low thickness change, and the comparative example in which the additive was not significantly deteriorated in cell performance showed a change in thickness exceeding 30% .

FIG. 8 is a diagram showing an SEM analysis after evaluating the life characteristics of a full-cell according to Examples and Comparative Examples of the present invention. FIG. Particularly, FIG. 8 shows the SEM analysis results of the deteriorated anodes, cathodes and separators obtained by disassembling the cells after evaluating the pull cell lifetime characteristics of the comparative example and the example.

Referring to FIG. 8, it can be seen that primary particles of the surface of the electrolyte containing no additive are warmed by the side reaction, and the phenomenon that the metal is eluted during the separation membrane analysis can be confirmed. However, in the analysis of the anode, cathode and separator containing the sulfonic electrolyte, it was confirmed that the primary particles were maintained and the elution behavior of the metal did not appear on the separator. As a result, it was confirmed that the sulfonic additive plays a role in controlling the deterioration of the anode.

FIGS. 9A and 9B are graphs showing the anode impedance analysis after evaluating the pull cell lifetime characteristics of the embodiment of the present invention and the comparative examples. FIG. Particularly, FIG. 9 is obtained by analyzing the deteriorated anode by EIS after evaluating the pull cell lifetime characteristics of the comparative example and the example.

Referring to FIGS. 9A and 9B, it can be seen that the resistance of the cathode plate with no additives is significantly increased as compared with that before the high temperature evaluation. On the other hand, in the case of the anode plate subjected to the electrochemical performance evaluation with the sulfonic additive, the increase of the resistance is not significant. This means that the anode membrane introduced from the sulfonic additive suppresses the side reaction of the additional electrolyte, .

10 is a graph showing FT-IR analysis after evaluating the life characteristics of a full-cell of Examples and Comparative Examples of the present invention. Particularly, FIG. 10 is a graph showing the results of FT-IR analysis of the anode material in which deterioration has progressed after evaluating the pull cell lifetime characteristics of the comparative examples and the examples, in order to identify the constituents of the surface coating film.

Referring to FIG. 10, it was confirmed that an alkylsulfone-based coating was formed on the surface of the electrode in the case of the analysis result. Based on the results of the analysis, PS showed that the anode and electrolyte It is possible to judge that the electrochemical performance is improved.

It should be noted that the embodiments of the present invention disclosed in the present specification and drawings are only illustrative of specific examples for the purpose of understanding and are not intended to limit the scope of the present invention. It will be apparent to those skilled in the art that other modifications based on the technical idea of the present invention are possible in addition to the embodiments disclosed herein.

100: lithium secondary battery 110: first electrode part
120: second electrode part 10: current collector
21, 22: anode 31, 32: cathode
40: electrolyte layer 50: separator
70: Case

Claims (7)

case;
A plurality of electrode units disposed at an inner side of the case at regular intervals and including a first electrode unit having a lithium composite metal anode and a second electrode unit having a cathode;
An electrolyte layer composed of a separation membrane disposed between the plurality of electrode units and an electrolyte solution in which at least a portion of the sulfonic material is mixed;
And a coating formed on the anode and formed by a side reaction corresponding to a sulfonic material,
Wherein the anode is a nickel excess-based anode of Li ₂ [Ni _{0.6 to 0.9} Co _{0.2 to 0.05} Mn _{0.2 to 0.05} ] O ₂ . The method according to claim 1,
The coating
Wherein the lithium secondary battery has orientation properties in a constant direction. 3. The method of claim 2,
The electrolyte solution
(LiPF ₆ ) is mixed with 2% by weight of PS (1,3-propanesultone) in a mixture of ethylene carbonate (EC): ethyl methyl carbonate (EC) = 3: 7 + 1.5M. The method according to claim 1,
Wherein the sulfonic material comprises a sultone compound represented by the formula (1), a sulfone compound represented by the formula (2) or a sulfonate compound represented by the formula (3).

(Wherein R 1 is an alkyl group or an alkenyl group having 1 to 5 carbon atoms)

(2), R 2 and R 2 'are selected from the group consisting of a hydrogen atom, a halogen atom, an alkyl group or an alkenyl group having 1 to 5 carbon atoms, an alkyl group having 1 to 5 carbon atoms, a phenyl group substituted or unsubstituted with a halogen atom, Independent from each other)

(3), R 2 and R 2 'are selected from the group consisting of a hydrogen atom, a halogen atom, an alkyl group or an alkenyl group having 1 to 5 carbon atoms, an alkyl group having 1 to 5 carbon atoms or a phenyl group or a phenoxy group substituted or unsubstituted with a halogen atom, Independent from each other) A film forming process for depositing a first electrode portion having an anode of a lithium composite metal material material in an electrolyte to form a film;
Disposing a plurality of electrode portions including a first electrode portion including the coated anode and a second electrode portion including a cathode at a predetermined interval inside the case;
Disposing a separation membrane between the plurality of electrode units;
And injecting an electrolytic solution in which at least a part of the sulfonic material is mixed into the case to form an electrolyte layer,
Wherein the anode is a nickel excess-based anode of Li ₂ [Ni _{0.6 to 0.9} Co _{0.2 to 0.05} Mn _{0.2 to 0.05} ] O ₂ . 6. The method of claim 5,
The electrolyte solution
EC (ethylene carbonate): EMC ( ethyl methyl carbonate) = 3: 7 + 1.5M LiPF 6 to PS (1,3-propanesultone) 2% by weight of process for producing a lithium secondary battery, characterized in that a mixture of a. 6. The method of claim 5,
The film formation process
And orienting the coating so that the coating has a constant directionality.

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