WO2018062698A1

WO2018062698A1 - Lithium secondary battery

Info

Publication number: WO2018062698A1
Application number: PCT/KR2017/009397
Authority: WO
Inventors: 방성용
Original assignee: (주)그리너지
Priority date: 2016-09-28
Filing date: 2017-08-29
Publication date: 2018-04-05

Abstract

A lithium secondary battery according to an embodiment of the present invention may comprise: a first electrode assembly comprising a positive electrode plate having a positive electrode tab and usable as a positive electrode terminal, a negative electrode plate having a serial connection tab, and a separation film provided between the positive electrode plate and the negative electrode plate; and a second electrode assembly provided to be insulated from the first electrode assembly, wherein the second electrode assembly may comprise a positive electrode plate having a serial connection tab, a negative electrode plate having a negative electrode tab and usable as a negative electrode terminal, and a separation film provided between the positive electrode plate and the negative electrode plate, wherein the serial connection tab of the first electrode assembly may be connected to the serial connection tab of the second electrode assembly, and the first electrode assembly and the second electrode assembly may be connected in series by the serial connection tabs.

Description

Lithium secondary battery

The present invention relates to a lithium secondary battery, and more particularly to a lithium secondary battery having excellent charge and discharge characteristics.

With the development of electrical and electronic technologies, the use of portable electronic products that are small, light, and have various functions is rapidly increasing. Batteries are generally used as a power supply device for the operation of portable electronic products, and secondary batteries that can be recharged and used again are mainly used.

Conventional secondary batteries include lead storage batteries, nickel cadmium batteries (Nicd), nickel hydrogen batteries (NiMH), lithium ion batteries (Li-ion), lithium ion polymer batteries (Li-ion polymer), and the like. Secondary batteries offer both economic and environmental advantages over primary batteries that are used once and discarded.

Conventional lithium secondary batteries include a positive electrode having an active material that reversibly occludes and releases lithium ions, a negative electrode and a separator that electrically separates them, and an electrolyte solution interposed between the positive electrode and the negative electrode, and between the two electrodes, Charging and discharging are performed by ions coming and going.

Representative anode active materials include graphite, silicon, silicon composite, and LTO (Lithium Titanium Oxide), and cathode active materials include LCO (Lithium Cobalt Oxide) and NMC (Lithium Nickel Manganese Cobalt Oxide). ), Lithium Nickel Oxide (NCA), and Lithium Iron Phosphite (LFP).

Among the cathode active materials, LTO has a spinel structure, which allows free intercalation / deintercalation of lithium ions in a 3D form, and has excellent charging properties compared to general one-dimensional intercalation of graphite.

LTO has a potential of 1.55V, which does not cause lithium plating and does not cause any safety problems due to lithium plating due to the deterioration of the lifetime seen in the graphite anode, and there is no SEI (Solid Electrolyte Interphase) film. The resistance value is low, and the charge and discharge characteristics at low temperature are excellent in addition to the structural characteristics described above.

In addition, LTO has almost no change in crystal structure during charging and discharging. As a result, the microstructure of the electrode plate is cracked or peeled apart from graphite because the thickness of the electrode plate remains constant while the electrode plate does not expand or contract during charging and discharging. It remains constant without delamination, showing superior lifetime characteristics over graphite. Here, the electrode plate refers to a structure composed of an active material, a binder, and a conductive agent.

In addition, LTO has superior thermal mechanical stability compared to graphite, and the mechanism itself makes the inside of the cell spontaneously safe when the potential itself decreases during external short or internal short due to the difference in conductivity during charging and discharging. This prevents phenomena such as cell ignition or explosion in the worst case.

Meanwhile, in the case of a lithium secondary battery based on a graphite negative electrode, there was only a method of regenerating a small amount of metal after disposal due to a concern about lithium plating during recycling, whereas in the case of a lithium secondary battery based on an LTO negative electrode, Since there is no concern, various methods can be applied to safely and efficiently recycle the desired metal during recycling, and have excellent life characteristics and, unlike NMC, NCA, and LCO, do not contain harmful metals.

However, the LTO negative electrode based lithium secondary battery has a lower specific capacity than the graphite negative electrode, and when designed as the same positive electrode as the graphite secondary lithium based battery, has a lower energy density than the graphite secondary lithium based battery.

The single cell battery in which the graphite negative electrode and various kinds of positive electrodes are combined has, for example, an average voltage of about 3.8 V for the single cell battery of the LCO positive electrode and the graphite negative electrode, and about 3.7 V for the single cell battery of the NMC positive electrode and the graphite negative electrode. It has an average voltage of

On the other hand, a single cell battery in which an LTO negative electrode and various kinds of positive electrodes are combined has, for example, an average voltage of about 2.4 V for a single cell battery of an LCO positive electrode and an LTO negative electrode, and about 2.3 V for a single cell battery having an NMC positive electrode and an LTO negative electrode. It has an average voltage of

As described above, the LTO negative cell-based single cell battery has a problem that it is difficult to have a voltage within a voltage range of a general small battery because the voltage of the battery is lowered due to the high negative electrode potential of the LTO.

Accordingly, the present invention has been made in view of the above circumstances, and has a superior charging characteristics, longer lifespan characteristics, and safety than conventional batteries, and has a new type of jelly roll series connection structure based on an LTO negative electrode having a rated voltage available in a small battery. The object is to provide a lithium secondary battery.

A lithium secondary battery according to an exemplary embodiment of the present invention for achieving the above object is provided between a positive electrode plate in which a positive electrode tab usable as a positive electrode terminal is formed, a negative electrode plate in which a series connection tab is formed, and a positive electrode plate and a negative electrode plate. A first electrode assembly including a separator; And a second electrode assembly provided to be insulated from the first electrode assembly, wherein the second electrode assembly includes: a positive electrode plate in which a series connection tab is formed, a negative electrode plate in which a negative electrode tab usable as a negative electrode terminal is formed; And a separator provided between the positive electrode plate and the negative electrode plate, wherein the series connection tab of the first electrode assembly is connected to the series connection tab of the second electrode assembly, and the first electrode assembly and the second electrode are connected to each other. The assembly may be connected in series by the series connection tabs.

Each of the first electrode assembly and the second electrode assembly is provided in plural to increase battery capacity, and the plurality of first electrode assemblies are stacked on each other with a separator therebetween to form a jellyroll structure, and the plurality of second electrode assemblies are provided. May be stacked on each other with a separator therebetween to form a jellyroll structure.

Each of the first electrode assembly and the second electrode assembly may be wound to form a jellyroll structure.

The first electrode assembly may be disposed to be stacked on the second electrode assembly, and may further include a rectangular case for accommodating the first and second electrode assemblies.

The first electrode assembly is deformed into a cylindrical shape to form an inner cylinder, and the second electrode assembly surrounds an outer circumference of the first electrode assembly to form an outer cylinder, and a cylinder housing the first and second electrode assemblies. It may further include a case of the shape.

The positive electrode plate of the first electrode assembly includes a positive electrode current collector to which one of the positive electrode active materials is applied among LFP, NMC, NCA, and LCO positive electrode active materials, and the positive electrode tab of the first electrode assembly is coated with the positive electrode active material. The first electrode assembly may extend from one side of the positive electrode current collector of the first electrode assembly and may be connected to the positive electrode lead tab to serve as a positive electrode terminal.

The negative electrode plate of the first electrode assembly includes a negative electrode current collector to which an LTO negative electrode active material is applied, and the series connection tab of the first electrode assembly is not coated with the negative electrode active material, and the negative electrode collector of the first electrode assembly is provided. It may be formed extending from one side of the whole.

The series connection tab of the first electrode assembly and the positive electrode tab of the first electrode assembly may be configured not to overlap each other.

The positive electrode plate of the second electrode assembly includes a positive electrode current collector to which LFP, NMC, NCA, and LCO positive electrode active material is applied, and the series connection tab of the second electrode assembly is not coated with the positive electrode active material. It may be formed extending from one side of the positive electrode current collector of the two electrode assembly.

The series connection tab of the first electrode assembly and the series connection tab of the second electrode assembly may overlap each other to electrically connect the first electrode assembly and the second electrode assembly.

The negative electrode plate of the second electrode assembly includes a negative electrode current collector to which the LTO negative electrode active material is applied, and the negative electrode tab of the second electrode assembly is not coated with the LTO negative electrode active material, and the negative electrode collector of the second electrode assembly is provided. It extends from one side of the whole and is connected to the negative lead tab can be used as the negative terminal.

The positive electrode tab of the first electrode assembly and the negative electrode tab of the second electrode assembly may be configured not to overlap each other.

Each of the negative electrode plate of the first electrode assembly, the positive electrode plate of the first electrode assembly, the negative electrode plate of the second electrode assembly, and the negative electrode plate of the second electrode assembly may include aluminum, stainless steel, or copper. Can be.

The first electrode assembly and the second electrode assembly may be self-balanced using an LFP cathode active material and an LTO cathode active material to prevent imbalance between each other.

Therefore, according to the lithium secondary battery according to the embodiment of the present invention, by connecting the two electrode assemblies through a new type of series structure, it is possible to use the LTO negative electrode, which was limited in use due to the low voltage, through which the conventional graphite It has better charging and lower temperature characteristics than the base secondary battery, and can solve safety problems, thereby widening usability in extreme environments, and having a rated voltage available as a small battery.

In addition, since the two electrode assemblies use the LFP positive electrode and the LTO negative electrode, it is possible to solve the problem of electrolyte oxidation and balancing between the electrode assembly, which are problems caused when two electrode assemblies are connected in series in a unit cell.

1 is a plan view of a lithium secondary battery according to an exemplary embodiment of the present invention.

2A, 2B, and 2C are first exploded plan views illustrating a disassembled state of a first electrode assembly of a lithium secondary battery according to an exemplary embodiment of the present invention.

3 is a partial cross-sectional view of the first electrode assembly of FIGS. 2A, 2B, and 2C.

4 is a second exploded plan view illustrating a disassembled state of a second electrode assembly of a lithium secondary battery according to an exemplary embodiment of the present disclosure.

5 is a partial cross-sectional view of the second electrode assembly of FIGS. 4A, 4B and 4C.

FIG. 6 is a plan view of a lithium secondary battery having a rectangular (pouch or metal case) form including a first electrode assembly and a second electrode assembly having a stacking structure according to an exemplary embodiment of the present invention.

7A, 7B, and 7C are cross-sectional views and perspective views of a lithium secondary battery in the form of a square (pouch or metal case) including a first electrode assembly and a second electrode assembly having a winding structure according to an exemplary embodiment of the present invention.

8A, 8B and 8C are perspective views of a cylindrical lithium secondary battery according to an embodiment of the present invention.

9 is a graph illustrating a self-balancing concept between the first and second electrode assemblies according to an exemplary embodiment of the present invention.

10 is a graph showing the filling rate according to the filling rate of LTO and graphite.

11 is a graph showing the discharge characteristics according to the temperature of the conventional secondary battery and the lithium secondary battery according to an embodiment of the present invention.

12 is a graph showing the thermal runaway performance of a conventional secondary battery and a lithium secondary battery according to an embodiment of the present invention.

In order to fully understand the present invention, the operational advantages of the present invention, and the objects achieved by the practice of the present invention, reference should be made to the accompanying drawings which illustrate preferred embodiments of the present invention and the contents described in the accompanying drawings.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings. As those skilled in the art would realize, the described embodiments may be modified in various different ways, all without departing from the spirit or scope of the present invention. In addition, parts irrelevant to the description are omitted in order to clearly describe the present invention, and the same reference numerals in the drawings indicate the same members.

Throughout the specification, when a part is said to "include" a certain component, it means that it may further include other components, without excluding the other components unless otherwise stated.

Referring to FIG. 1, the lithium secondary battery 100 according to an exemplary embodiment of the present invention has excellent charge and discharge characteristics and a rated voltage available as a small battery, and includes a first electrode assembly 110 and a second electrode assembly ( 120).

Lithium secondary battery 100 according to an embodiment of the present invention, each of the first electrode assembly 110 and the second electrode assembly 120 is a slurry containing an electrode coated with a slurry containing the LFP cathode active material and the LTO cathode active material It is provided with a coated electrode and laminated with a separator interposed therebetween to be insulated from each other, and connected to each other in a new type of serial structure through each series connection tab (aT1, cT2), so that even an LTO cathode active material is used. It can have the rated voltage (3.5 ~ 3.9V) available for electronics, and it has excellent low temperature, charging, and life characteristics, stable structure of Lithium Titanate, and electrochemical without Lithium plating. Properties can minimize the risk of explosions during thermal and mechanical abuse.

First, the reason why a new type of series structure is applied to the lithium secondary battery 100 according to the embodiment of the present invention will be described, and then the configuration of the lithium secondary battery 100 according to the embodiment of the present invention will be described in detail.

A structure of making a single cell by connecting two electrode assemblies in parallel is generally known, but a structure of connecting in series is not implemented in a lithium ion battery because there are two serious problems as follows.

First, in the case of commonly used carbonate (carbonate) solvent-based electrolyte (Ethylene carbonate, Propylene carbonate, Dimethyl carbonate, Diethyl carbonate, Ethylmethyl carbonate, etc.), there is a property to decompose at a voltage of more than 4.6V. To solve this problem, it is necessary to use a solid electrolyte or a new ionic liquid. However, there is no electrolyte system that can replace a carbonate-based solvent because of poor ionic conductivity and limited environmental conditions. One electrode assembly (jelly roll), which uses graphite as a cathode, usually has a voltage of 3.3 V or higher, and a voltage of 6.6 V or higher when connected in series with another electrode assembly (jelly roll) in any anode system. You cannot use it.

Second, an imbalancing problem occurs when two electrode assemblies are connected in series. In case of making a series battery using general LCO / Graphite or NMC / Graphite, there is an imbalance between two jelly rolls (electrode assembly), which can cause the difference in voltage of each jelly roll. It causes overdischarge and ultimately accelerates deterioration of the whole unit cell.

In FIG. 9, it can be seen that a typical NMC / Graphite cell has a 20% charge capacity difference due to a 0.2V charge difference. Since the two electrode assemblies are connected in series inside the cell, it is difficult to construct additional external protection circuits in the cell to suppress the imbalance, and each of the electrode assemblies (jelly rolls) may be chemically applied, such as a chemical shuttle. Overcharge and overdischarge can be suppressed by the oxidation and reduction of the chemical shuttle, but the currently available range of the chemical shuttle does not exceed 4V and there is a problem that can degrade other performance.

In addition, when connecting the two electrode assembly (jelly roll) in parallel, the structure is simple, but when connected in series it is difficult to make a serial structure in the form of a common electrode.

Lithium secondary battery 100 according to an embodiment of the present invention is a new type of serial structure is applied to solve the above two problems and the structural complexity when connected in series.

That is, the lithium secondary battery 100 according to the embodiment of the present invention is provided such that the first electrode assembly 110 and the second electrode assembly 120 including the LTO anode active material and the LFP cathode active material are stacked, and have a new shape. By being connected to each other in series, they have a rated voltage of approximately 4.4V, preferably 3.6 to 3.9V, which can be used as a general small battery, and have better charging and low temperature characteristics, longer life, and mechanical and thermal stability than conventional secondary batteries. It can be used for general consumer electronics.

In addition, the lithium secondary battery 100 according to an exemplary embodiment of the present invention may have a self-potential control characteristic using LFP and LTO material characteristics, which cause a sudden change in potential at the end of charge and discharge. 120, the voltage difference between the two electrode assemblies (jelly roll) can be kept to a minimum. As shown in the graph of FIG. 9, the capacity difference due to the potential difference between the two electrode assemblies (jelly roll) during charging and discharging compared to the NMC / Graphite cell can be minimized.

In addition, the lithium secondary battery 100 according to the embodiment of the present invention, in contrast to simply connecting two unit cells in series, the amount of pouch or metal constituting the positive electrode / negative electrode terminal tab terminal and the case is reduced to reduce the cost It is possible to increase the energy density of about 3%.

In addition, the lithium secondary battery 100 according to the exemplary embodiment of the present invention may be manufactured through an existing production process, and does not require additional parts or devices during manufacturing, and may be manufactured through both a winding method and a stacking method. .

Hereinafter, the configuration of the first electrode assembly 110 and the second electrode assembly 120 will be described in detail with reference to FIGS. 2A, 2B, 2C, and 5.

First, a configuration of the first electrode assembly 110 will be described in detail with reference to FIGS. 2A, 2B, 2C, and 3. FIG. 2A is a plan view of a cathode electrode 111 of the first electrode assembly 110, FIG. 2B is a plan view of an anode electrode 113 of the first electrode assembly 110, and FIG. 1 is a plan view illustrating a state in which the positive electrode plate 111 and the negative electrode plate 113 of the electrode assembly 110 are stacked. 3 is a cross-sectional view of the first electrode assembly 110.

The first electrode assembly 110 may include a positive electrode plate 111, a negative electrode plate 113, and a separator 115.

In FIG. 2A, a positive electrode tab cT1 may protrude from a left side of the positive electrode plate 111. In this case, the positive electrode tab cT1 may be formed on the upper side (refer to FIG. 3) on the left side of the positive electrode plate 111.

In FIG. 2B, a series connection tab aT1 may protrude from the left side of the negative electrode plate 113. Here, the series connection tab aT1 may be formed at the central portion of the left side of the negative electrode plate 113. The series connection tab aT1 is preferably formed smaller in size than the positive electrode tab cT1.

In FIG. 2C, the stacked state of the positive electrode plate 111 and the negative electrode plate 113 may be confirmed. Here, the positive electrode tab cT1 and the series connection tab aT1 do not overlap each other. A separator 115 is provided between the positive electrode plate 111 and the negative electrode plate 113 to insulate the positive electrode plate 111 and the negative electrode plate 113. This can be seen in FIG.

Referring to FIG. 3, the stacked structure of the first electrode assembly 110 can be confirmed. The positive electrode plate 111 may include a positive electrode current collector 111 a and a positive electrode tab cT1. The positive electrode current collector 111 a is a part constituting the body of the positive electrode plate 111, and may be formed in a square plate shape as shown in FIGS. 2A, 2B, and 2C. The positive electrode current collector 111 a is preferably made of aluminum or stainless steel.

A slurry (a cathode active material, a binder, and a conductive agent dispersed in a solvent) including the LFP cathode active material 111b may be applied to the lower surface and the upper surface of the cathode current collector 111a. Here, the LFP cathode active material 111b refers to a lithium iron phosphate (LiFePO 4) active material. The LFP cathode active material 111b is generally a material for forming a cathode of a lithium secondary battery, and a detailed description thereof will be omitted. In addition, the LFP cathode active material 111b may be replaced with any one of NMC, NCA, LCO, and LMO cathode active material.

The positive electrode tab cT1 may be formed to extend from the left side of the positive electrode current collector 111a (see FIG. 3). The positive electrode tab cT1 may be made of the same material as the positive electrode current collector 111a. The positive electrode tab cT1 is not coated with the positive electrode active material. The positive electrode tab cT1 may be connected to a lead tab, which is a separate conductive connection component, to be used as a positive electrode terminal of the lithium secondary battery 100.

The negative electrode plate 113 may include a negative electrode current collector 113 a and a series connection tab aT1. The negative electrode current collector 113 a is a part constituting the body of the negative electrode plate 113, and may be formed in the same square plate shape as the positive electrode current collector 111 a. The negative electrode current collector 113 a is preferably made of aluminum, copper, or stainless steel.

On the lower surface and the upper surface of the negative electrode current collector 113a, a slurry (a negative electrode active material, a binder, and a conductive agent dispersed in a solvent) 113b including an LTO negative electrode active material may be applied.

Here, the LTO anode active material 113b refers to lithium titanium oxide (Li 4 Ti 5 O 12). Since the LTO anode active material 113b has been described above, a detailed description thereof will be omitted.

The series connection tab aT1 may be formed to extend from the left side (refer to FIG. 3) of the negative electrode current collector 113a. The series connection tab aT1 may be formed of the same material as the negative electrode current collector 113a. The series connection tab aT1 is not coated with the negative electrode active material. The series connection tab aT1 may be formed so as not to overlap the positive electrode tab cT1. The series connection tab aT1 is preferably formed smaller in size than the positive electrode tab cT1. The series connection tab aT1 is directly connected to the series connection tab aT2 of the second electrode assembly 120 to connect the first electrode assembly 110 and the second electrode assembly 120 in a new form of series structure. Play a role of

The separator 115 may be provided between the positive electrode plate 111 and the negative electrode plate 113 to insulate the positive electrode plate 111 and the negative electrode plate 113. That is, the separator 115 may be provided between the LFP cathode active material 111b on the lower surface of the cathode current collector 111a and the LTO anode active material 113b on the upper surface of the anode current collector 113a.

The separator 115 electrically separates the positive electrode plate 111 and the negative electrode plate 113 and may pass lithium ions through internal pores. The separator 115 is usually manufactured using a polyolefine-based (polyethylene, polypropylene) material or a nonwoven fabric, and includes polyvinylidene fluoride, polyethylene oxide, polyacrylonitrile, and poly It may comprise any one of polyvinylidene fluoride hexafluoropropylene (polyvinylidene fluoride hexafluoropropylene).

A configuration of the second electrode assembly 120 will be described in detail with reference to FIGS. 4A, 4B, 4C, and 5. 4A is a plan view of the positive electrode plate 121 of the second electrode assembly 120, FIG. 4B is a plan view of the negative electrode plate 123 of the second electrode assembly 120, and FIG. 4C is a second electrode assembly 120. Is a plan view showing a state in which the positive electrode plate 121 and the negative electrode plate 123 are stacked. 5 is a cross-sectional view of the second electrode assembly 120.

The second electrode assembly 120 may include a positive electrode plate 121, a negative electrode plate 123, and a separator 125.

In FIG. 4A, a series connection tab cT2 may protrude from the left side of the positive electrode plate 121. Here, the connection tab cT2 may be formed at the center of the left side of the positive electrode plate 121.

In FIG. 4B, a negative electrode tab aT2 may protrude from the left side of the negative electrode plate 123. Here, the negative electrode tab aT2 may be formed to be biased downward (based on FIGS. 4A, 4B, and 4C) on the left side of the negative electrode plate 123. The negative electrode tab aT2 is preferably formed larger in size than the series connection tab cT2.

In FIG. 4C, the stacked state of the positive electrode plate 121 and the negative electrode plate 123 may be confirmed. Here, the series connection tab cT2 and the negative electrode tab aT2 do not overlap each other. A separator 125 is provided between the positive electrode plate 121 and the negative electrode plate 123 to insulate the positive electrode plate 121 and the negative electrode plate 123. This can be seen in FIG.

Referring to FIG. 5, the stacked structure of the second electrode assembly 120 may be confirmed. The positive electrode plate 121 may include a positive electrode current collector 121 a and a series connection tab cT2. The positive electrode current collector 121 a is a part constituting the body of the positive electrode plate 121, and may be formed in a square plate shape as shown in FIGS. 4A, 4B, and 4C. The positive electrode current collector 121 a may be made of aluminum or stainless steel.

On the lower surface and the upper surface of the positive electrode current collector 121a, a slurry including the LFP positive electrode active material 121b (a positive electrode active material, a binder, and a conductive agent dispersed in a solvent) may be applied. Here, the LFP cathode active material 121b is the same as the LFP cathode active material 111b applied to the cathode current collector 111a of the first electrode assembly 110, and a detailed description thereof will be omitted.

The series connection tab cT2 may be formed to extend from the left side (refer to FIG. 5) of the positive electrode current collector 121a. The series connection tab cT2 may be made of the same material as the positive electrode current collector 121a. The series connection tab cT2 is not coated with the positive electrode active material. The series connection tab cT2 may be overlapped with the series connection tab aT1 of the first electrode assembly 110 to electrically connect the second electrode assembly 120 and the first electrode assembly 110 in series. have.

The negative electrode plate 123 may include a negative electrode current collector 123a and a negative electrode tab aT2. The negative electrode current collector 123a is a part constituting the body of the negative electrode plate 123 and may be formed in the same square plate shape as the positive electrode plate 121. The negative electrode current collector 123a may preferably be made of aluminum, copper, or stainless steel.

On the lower surface and the upper surface of the negative electrode current collector 123a, a slurry including the LTO negative electrode active material 123b (a negative electrode active material, a binder, and a conductive agent dispersed in a solvent) may be applied. Here, the LTO negative electrode active material 123b is the same as the LTO negative electrode active material 113b applied to the negative electrode current collector 113a of the first electrode assembly 110, and a detailed description thereof will be omitted.

The negative electrode tab aT2 may be formed to extend from the left side of the negative electrode current collector 123a. The negative electrode tab aT2 may be formed of the same material as the negative electrode current collector 123a. The negative electrode tab aT2 is not coated with the negative electrode active material. The negative electrode tab aT2 may be formed so as not to overlap the series connection tab cT2. The negative electrode tab aT2 is preferably formed larger in size than the series connection tab cT2. The negative electrode tab aT2 may be connected to a lead tab, which is a separate conductive connection component, to be used as a negative electrode terminal of the lithium secondary battery 100.

The separator 125 may be provided between the positive electrode plate 121 and the negative electrode plate 123 to insulate the positive electrode plate 121 and the negative electrode plate 123. That is, the separator 125 may be provided between the LFP cathode active material 121b on the bottom surface of the cathode current collector 121a and the LTO anode active material 123b on the top surface of the anode current collector 123a. The separator 125 may be made of the same material as the separator 115 of the first electrode assembly 110 described above.

Referring to FIG. 6, a plan view of a lithium secondary battery in the form of a square (pouch or metal case) including a first electrode assembly and a second electrode assembly having a stacking structure according to an embodiment of the present invention can be seen.

The first electrode assembly 110 and the second electrode assembly 120 may be stacked with an electrode assembly separator (not shown) therebetween. At this time, the positive electrode plate 111 of the first electrode assembly 110 is disposed at the top.

The positive electrode tab cT1 of the first electrode assembly 110 and the series connection tab cT2 of the second electrode assembly 120 may overlap each other, and thus, the first electrode assembly 110 and the second electrode assembly ( 120 is connected to a new type of serial structure.

The quadrangular case P may accommodate the first electrode assembly 110, the second electrode assembly 120, and the electrode assembly separator. Here, the rectangular case P may include a pouch, a metal can, or the like.

The positive electrode tab cT1 may be connected to a lead tab, which is a separate conductive connection part, to protrude and be disposed outside the rectangular case P, and may be used as a positive electrode terminal of the lithium secondary battery 100. have. In addition, the negative electrode tab aT2 may be connected to a lead tab, which is a separate conductive connection part, to be protruded outside the rectangular case P, and used as a negative electrode terminal of the lithium secondary battery 100. have. In the case P of the rectangular shape may be provided with a gel electrolyte or a solid electrolyte such as a liquid electrolyte or a polymer for the smooth movement of lithium ions.

Meanwhile, each of the first electrode assembly 110 and the second electrode assembly 120 may be formed in a jellyroll structure to increase battery capacity. Here, the jellyroll structure can be formed in two ways.

First, a plurality of first electrode assemblies 110 and second electrode assemblies 120 are provided in plurality, and the plurality of first electrode assemblies 110 are stacked on each other with a separator therebetween to form a jellyroll structure. The second electrode assembly 120 is laminated to each other with a separator therebetween to form a jellyroll structure. Subsequently, when the first electrode assembly 110 having the jellyroll structure is stacked on the second electrode assembly 120 having the jellyroll structure with the electrode assembly separator interposed therebetween, lithium in the form of a square (pouch or metal case) as described above may be used. The secondary battery 110 is completed.

The second jellyroll structure can be seen through FIGS. 7A, 7B and 7C.

7A, 7B, and 7C, cross-sectional views and perspective views of a first electrode assembly and a second electrode assembly of a winding structure and a lithium secondary battery in a square (pouch or metal case) form according to an embodiment of the present invention are shown. You can check it.

7A is a cross-sectional view and a perspective view of the first electrode assembly of the winding structure, and FIG. 7B is a cross-sectional view and a perspective view of the second electrode assembly of the winding structure, and FIG. 7C is a rectangular shape in which the first electrode assembly is stacked on the second electrode assembly. A perspective view of a lithium secondary battery.

In FIG. 7A, the first electrode assembly 110 is wound to form a jellyroll structure, and in FIG. 7B, the second electrode assembly 120 is wound to form a jellyroll structure.

In FIG. 7C, in the lithium secondary battery 100, the first electrode assembly 110 is stacked on the second electrode assembly 120, and the series connection tabs aT1 and cT2 are coupled to each other to form the first electrode assembly 110. And the second electrode assembly 120 may be finally completed by connecting in series. In this case, the positive electrode tab cT1 of the first electrode assembly 110 is connected to the lead tab L1 and used as the positive electrode terminal, and the negative electrode tab aT2 of the second electrode assembly 120 is connected to the lead tab L2. It is used as a negative terminal.

Referring to FIGS. 8A, 8B, and 8C, a lithium secondary battery 100 having a cylindrical shape may be identified. 8A is a perspective view of the first electrode assembly 110 constituting the inner cylinder of the cylindrical lithium secondary battery 100, and FIG. 8B is a second electrode constituting the outer cylinder of the cylindrical lithium secondary battery 100. 8 is a perspective view of a cylindrical lithium secondary battery 100 in a cylindrical form.

In FIG. 8A, the first electrode assembly 110 may be formed as an inner cylinder by holding and winding a positive electrode plate, a negative electrode plate, and a separator using a mandrel.

In FIG. 8B, the second electrode assembly 120 may be formed as an outer cylinder by winding the positive electrode plate, the negative electrode plate, and the separator so as to surround the outer circumference of the first electrode assembly 120.

In the cylindrical lithium secondary battery 100 of FIG. 8C, the first electrode assembly 110, which is an inner cylinder, is surrounded by a second electrode assembly 120 that is surrounded by an outer cylinder, and the series connection tabs aT1 and cT2 are connected to each other. The first electrode assembly 110 and the second electrode assembly 120 may be combined and finally completed in series.

Here, the negative electrode tab aT2 of the second electrode assembly 120 includes the positive electrode tab cT1 of the first electrode assembly 110, the series connection tab aT1 of the first electrode assembly, and the second electrode assembly 120. May be formed in a direction opposite to the direction in which the series connection tabs cT2 are formed.

That is, the positive electrode tab cT1 of the first electrode assembly 110, the series connection tab aT1 of the first electrode assembly 110, and the series connection tab cT2 of the second electrode assembly 120 may have a cylindrical shape. The positive electrode tab cT1 of the first electrode assembly 110 may be disposed to protrude from an upper portion of the lithium secondary battery 100 and may be connected to an upper cap assy 'to form a positive electrode terminal of the battery. The negative electrode tab aT2 of the second electrode assembly 120 is disposed to protrude on the lower portion of the cylindrical lithium secondary battery 100 so as to be connected to the lower portion of the cylindrical metalken so that the metalken itself forms a negative electrode potential. The cap and the lower metalken can be insulated with insulating plastic to electrically insulate the positive and negative terminals.

Meanwhile, the upper and lower ends of the cylindrical lithium secondary battery 100 have a positive electrode tab cT1 of the first electrode assembly 110, a series connection tab aT1 of the first electrode assembly 110, and a second electrode assembly 120. A circular protective cap (not shown) may be coupled to protect the series connection tab cT2 and the negative electrode tab aT2 of the second electrode assembly 120.

9, imbalancing between the first and

second electrode assemblies

110 and 120 of the lithium secondary battery 100 (S2 Cell (LFP / LTO)) according to an embodiment of the present invention is suppressed. Demonstrates the concept of self-balancing.

Hereinafter, the self-balancing characteristics of the lithium secondary battery 100 according to the embodiment of the present invention will be described in comparison with the conventional NMC / Graphite secondary battery.

First, in the case of the conventional NMC / Graphite secondary battery, there is a capacity difference of 20% due to the 0.2V voltage difference (voltage difference). On the other hand, in the case of the lithium secondary battery 100 according to the embodiment of the present invention, the charge capacity difference of 2% due to the 0.2V voltage difference. This shows that self-balancing occurs to minimize the difference in filling amount due to a sudden change of potential in the charging end section.

In addition, the conventional NMC / Graphite secondary battery, the discharge capacity difference of 27% due to the 0.1V voltage difference. On the other hand, the lithium secondary battery 100 according to the embodiment of the present invention, the discharge capacity difference of less than 1% due to the 0.1V voltage difference. This shows that self balancing occurs in the discharge end section.

As such, the lithium secondary battery 100 according to the embodiment of the present invention has a self-balancing at the terminal during charging and discharging, and thus the capacity difference due to the voltage difference between the two electrode assemblies (jelly rolls) compared to the conventional NMC / Graphite secondary battery. It can be minimized.

Hereinafter, with reference to Table 1, a detailed specification of the lithium secondary battery 100 according to an embodiment of the present invention will be described.

전지 종류(Battery Type)Battery Type	종래 기술(Current Technology)Current Technology				본 발명의 실시 예에 따른 리튬 이차 전지Lithium secondary battery according to an embodiment of the present invention
	리튬 코발트 산화물(Lithium cobalt Oxide)Lithium cobalt oxide	리튬 니켈망간코발트(Lithium Nickel Manganese Cobalt Oxide)Lithium Nickel Manganese Cobalt Oxide	리튬 이온인산(Lithium Iron Phosphate)Lithium Iron Phosphate	리튬 타이타 네이트 (Lithium TitanateLithium Titanate
정격 전압(Nominal voltage)Nominal voltage	3.8V3.8 V	3.7V3.7 V	3.3V3.3V	1.9V1.9V	3.8V3.8 V
충전 속도(Charge Rate)Charge Rate	0.7C0.7C	0.7C0.7 C		1C1C		5C5C	5C 5C

충방전 수명(cycle life)Cycle life	500 ~ 1,000 회500 to 1,000 times	1,000 ~ 2,000회1,000 to 2,000 times	1,000 ~ 2,000회1,000 to 2,000 times	3,000 ~ 7,000회3,000 to 7,000	3,000 ~ 7,000회3,000 to 7,000
열폭주(Thermal Runaway)Thermal Runaway	150°C150 ° C	190°C190 ° C	230°C230 ° C	>300°C> 300 ° C	>300°C> 300 ° C
응용분야(Application)Application	모바일, 태블릿, 랩탑, 카메라Mobile, tablet, laptop, camera	모바일 디바이스, 전기차, 산업용 전지Mobile devices, electric vehicles, industrial batteries	전기차, 전기바이크, 산업용 전지Electric cars, electric bikes, industrial batteries	전기저장 시스템(ESS),전기차, 태양열 전지Electric Storage System (ESS), Electric Vehicles, Solar Cells	전기 저장 시스템(ESS), 태양열 전지, 전기차, 전기 바이크, 산업용전지Electric Storage System (ESS), Solar Cell, Electric Vehicle, Electric Bike, Industrial Battery

As shown in Table 1, the lithium secondary battery 100 according to the embodiment of the present invention has a series connection tab aT1 of the first electrode assembly 110 and a series connection tab cT2 of the second electrode assembly 120. By constructing a new direct-connected series structure, it is possible to solve various problems caused by using LTO and LFP as anode active material and cathode active material, thereby lowering the rating of a lithium secondary battery using a conventional LTO anode active material. It can have a high rated voltage (3.8V) to solve the voltage (1.9 ~ 2.4V) problem.

In addition, the lithium secondary battery 100 according to the embodiment of the present invention may have a faster charging speed (for example, 5C) than any conventional secondary battery, and also has superior charging performance even at low temperatures, and is smaller than conventional secondary batteries. It can have more than 3 times longer lifespan and shows safety that shows no thermal runaway even at high temperatures of more than 300 degrees.

10 to 12, the performance of the lithium secondary battery 100 and the conventional secondary battery according to an embodiment of the present invention will be described.

FIG. 10 is a graph showing capacity retention according to charge rates of LTO and graphite used as a negative electrode active material of a secondary battery.

In the graph of FIG. 10, LTO and graphite have a similar charging rate when low-rate charging (0.5C or less) and a specific current flows below 100 mA / g, but when charging with a high-rate current (2C Above), it shows a sudden difference in charging rate, and when the specific current flows over 1000 mA / g, it shows more than 7 times of charging rate difference. As described above, the secondary battery for solving the problem of rapid charging can be improved by using the battery of the present invention.

11 is a graph showing the discharge characteristics according to the temperature of the conventional secondary battery and the lithium secondary battery according to an embodiment of the present invention. Here, the conventional secondary battery includes an NMC / Graphite secondary battery, an LFP / Graphite secondary battery, and an NMC / LTO secondary battery.

In the graph of FIG. 11, the NMC / Graphite secondary battery, the LFP / Graphite secondary battery, the NMC / LTO secondary battery, and the lithium secondary battery (LFP / LTO) according to the embodiment of the present invention show a discharge rate close to 100% near room temperature. The lower the temperature, the lower the discharge performance. At this time, the lithium secondary battery (LFP / LTO) according to the embodiment of the present invention has a discharge rate of about 80% at -30 ° C, and thus has higher characteristics at a lower temperature than other conventional secondary batteries.

12 is a graph showing the thermal runaway performance of a conventional secondary battery and a lithium secondary battery according to an embodiment of the present invention. Herein, the conventional secondary battery includes an LCO / Graphite secondary battery, an NMC / Graphite secondary battery, and an LFP / Graphite secondary battery.

In the graph of Figure 12, the LCO / Graphite secondary battery increases the temperature at a rate of 5 ° C / min from room temperature and when the thermal runaway phenomenon is reached when the temperature reaches approximately 150 ° C, thermal runaway phenomenon will appear.

When the NMC / Graphite secondary battery reaches a temperature of approximately 190 ° C thermal runaway phenomenon will appear.

In the LFP / Graphite secondary battery, when the temperature reaches approximately 230 ° C., thermal runaway occurs.

On the other hand, the lithium secondary battery (LFP / LTO) according to an embodiment of the present invention does not appear thermal runaway phenomenon until the charging temperature reaches 250 ° C.

As described above, the lithium secondary battery according to the exemplary embodiment of the present invention may be charged faster than the conventional secondary battery, has better charge and discharge characteristics than the conventional secondary battery at low temperature, and has stronger heat resistance than the conventional secondary battery.

Accordingly, the lithium secondary battery 100 according to the embodiment of the present invention may have excellent temperature and charge / discharge characteristics of the LTO anode active material and a rated voltage available for general electronics, and structural stability of the LTO anode active material. The risk of explosion due to temperature rise can be reduced due to the electrochemical properties that prevent over-liquidation and can be applied to various fields such as electric storage systems (ESS), solar cells, electric vehicles, electric bikes, industrial batteries and the like.

Although the present invention has been described with reference to the embodiments illustrated in the drawings, this is merely exemplary, and it will be understood by those skilled in the art that various modifications and equivalent other embodiments are possible.

Therefore, the true technical protection scope of the present invention will be defined by the technical spirit of the appended claims.

Claims

A first electrode assembly including a positive electrode plate having a positive electrode tab usable as a positive electrode terminal, a negative electrode plate having a series connection tab formed thereon, and a separator provided between the positive electrode plate and the negative electrode plate; And

A second electrode assembly provided to be insulated from the first electrode assembly;

Including,

The second electrode assembly includes a positive electrode plate in which a series connection tab is formed, a negative electrode plate in which a negative electrode tab usable as a negative electrode terminal is formed, and a separator provided between the positive electrode plate and the negative electrode plate,

The series connection tab of the first electrode assembly is connected to the series connection tab of the second electrode assembly,

And the first electrode assembly and the second electrode assembly are connected in series by the series connection tabs.
The method of claim 1,

Each of the first electrode assembly and the second electrode assembly is provided in plurality in order to increase battery capacity.

The plurality of first electrode assemblies are stacked on each other with a separator therebetween to form a jellyroll structure.

The plurality of second electrode assemblies are laminated to each other with a separator therebetween to form a jellyroll structure, characterized in that the lithium secondary battery.
The method of claim 1,

And each of the first electrode assembly and the second electrode assembly is wound to have a jellyroll structure.
The method according to claim 2 or 3,

The first electrode assembly is disposed to be stacked on the second electrode assembly,

Lithium secondary battery further comprises a case of a rectangular shape accommodating the first and second electrode assembly.
The method according to claim 2 or 3,

The first electrode assembly is deformed into a cylindrical shape to form an inner cylinder,

The second electrode assembly surrounds the outer circumference of the first electrode assembly to form an outer cylinder,

And a cylindrical case accommodating the first and second electrode assemblies.
The method according to claim 2 or 3,

The positive electrode plate of the first electrode assembly includes a positive electrode current collector to which any one positive electrode active material of LFP, NMC, NCA, LCO positive electrode active material is applied,

The positive electrode tab of the first electrode assembly is not coated with the positive electrode active material, extends from one side of the positive electrode current collector of the first electrode assembly, and is connected to the positive electrode lead tab to be used as a positive electrode terminal. Lithium secondary battery.
The method of claim 6,

The negative electrode plate of the first electrode assembly includes a negative electrode current collector to which the LTO negative electrode active material is applied,

The series connection tab of the first electrode assembly is not coated with the negative electrode active material, and extends from one side of the negative electrode current collector of the first electrode assembly, characterized in that the lithium secondary battery.
The method of claim 7, wherein

The series connection tab of the first electrode assembly and the positive electrode tab of the first electrode assembly are configured not to overlap each other, the lithium secondary battery.
The method of claim 8,

The positive electrode plate of the second electrode assembly includes a positive electrode current collector to which LFP, NMC, NCA, LCO positive electrode active material is coated,

The serial connection tab of the second electrode assembly is not coated with the positive electrode active material, and extends from one side of the positive electrode current collector of the second electrode assembly.
The method of claim 9,

The series connection tab of the first electrode assembly and the series connection tab of the second electrode assembly overlap each other to electrically connect the first electrode assembly and the second electrode assembly.
The method of claim 10,

The negative electrode plate of the second electrode assembly includes a negative electrode current collector to which the LTO negative electrode active material is applied,

The negative electrode tab of the second electrode assembly is not coated with the LTO negative electrode active material, extends from one side of the negative electrode current collector of the second electrode assembly, and is connected to the negative electrode lead tab to be used as a negative electrode terminal. Lithium secondary battery.
The method of claim 11,

The positive electrode tab of the first electrode assembly and the negative electrode tab of the second electrode assembly are configured so as not to overlap each other, the lithium secondary battery.
The method of claim 1,

Each of the negative electrode plate of the first electrode assembly, the positive electrode plate of the first electrode assembly, the negative electrode plate of the second electrode assembly, and the negative electrode plate of the second electrode assembly may include aluminum, stainless steel, or copper. A lithium secondary battery, characterized in that.
The method of claim 1,

And the first electrode assembly and the second electrode assembly are self-balanced using an LFP cathode active material and an LTO anode active material to prevent imbalance between each other.