阅读说明：本技术 堆叠-折叠型电极组件和包括该堆叠-折叠型电极组件的锂金属电池 (Stack-folding type electrode assembly and lithium metal battery including the same ) 是由 全映真 于 2019-08-06 设计创作，主要内容包括：本发明涉及一种堆叠-折叠型电极组件和包括该电极组件的锂金属电池。详细地,根据本发明的示例性实施方式,所述锂金属电池实现为堆叠-折叠型,并且绝缘带分别贴附至折叠隔离膜的上侧和下侧,从而解决了在充电和放电过程中在负极表面上产生的锂枝晶和死锂暴露的缺陷。(The present invention relates to a stack-folding type electrode assembly and a lithium metal battery including the same. In detail, according to an exemplary embodiment of the present invention, the lithium metal battery is implemented in a stack-folding type, and insulating tapes are respectively attached to upper and lower sides of a folded separator, thereby solving the defects of lithium dendrite and dead lithium exposure generated on the surface of a negative electrode during charge and discharge.)

1. A stack-folding type electrode assembly comprising:

a plurality of unit cells including a lithium metal anode, a cathode, and a separator disposed between the lithium metal anode and the cathode;

a folded separation film continuously disposed between the unit cells adjacent to each other; and

insulating tapes attached to upper and lower sides of the folded separation film, respectively,

wherein the insulating tape is exposed to the outside.

2. The stack-folding type electrode assembly according to claim 1, wherein

The unit cells are bicells respectively including

Two of the positive electrodes or two of the lithium metal negative electrodes.

3. The stack-folding type electrode assembly according to claim 1, wherein

The width of the insulating tape is equal to a gap (gap) between a vertical length of the lithium metal negative electrode and a vertical length of the folded separation film.

4. The stack-folding type electrode assembly according to claim 1, wherein

The thickness ratio of the insulating tape to the lithium metal negative electrode is 0.1 to 1.

5. The stack-folding type electrode assembly according to claim 1, wherein

The thickness of the insulating tape is 20 μm to 100 μm.

6. The stack-folding type electrode assembly according to claim 1, wherein

The insulating tape includes at least one of Polyimide (PI), polypropylene (PP), and polyethylene terephthalate (PET).

7. The stack-folding type electrode assembly according to claim 1, wherein

Each of the electrode tabs protrudes from the lithium metal negative electrode and the positive electrode, and a part or all of the protruding part is exposed to an upper side of the electrode assembly.

8. The stack-folding type electrode assembly according to claim 1, wherein

The lithium metal anode includes an anode current collector and a lithium metal (Li-metal) thin film disposed on the anode current collector.

9. A lithium metal battery, wherein the stack-folding type electrode assembly of any one of claim 1 through claim 8 is accommodated in a case.

10. The lithium metal battery of claim 9, wherein

The housing is a bag (pouch) type housing.

Technical Field

The application claims priority and benefit of korean patent application No. 10-2018-0094526, filed on 13.8.2018 and korean patent application No. 10-2019-0094560, filed on 2.8.2019, and incorporated herein by reference in their entirety.

The present invention relates to a stack-folding type electrode assembly and a lithium metal battery including the same.

Background

The lithium metal battery corresponds to a battery to which a negative active material made of a lithium metal (Li-metal) or lithium alloy (Li-alloy) material is applied, and may theoretically have a very high energy capacity due to the characteristics of the negative active material, but lithium dendrites grow on the surface of the negative electrode with repeated charge and discharge, and the safety of the battery is lowered.

When a lithium metal battery is obtained according to a generally known stack-folding scheme, lithium dendrites and Dead lithium (lithium) generated on the surface of the negative electrode during charge and discharge, which may no longer participate in charge and discharge, are exposed at the upper and lower sides of the electrode assembly, and a fine short circuit or a complete short circuit may be generated inside the battery. The life of the battery in which the short circuit has occurred may not be further maintained in any form.

Disclosure of Invention

[ problem ] to

The present invention has been made in an effort to provide a stack-folding type lithium metal battery in which lithium dendrite and dead lithium generated on the surface of a negative electrode are prevented from being exposed during charge and discharge by attaching insulating tapes to the upper and lower sides of a folding separator.

[ solution ]

An exemplary embodiment of the present invention provides a stack-folding type electrode assembly, including: a plurality of unit cells including a lithium metal anode, a cathode, and a separator disposed between the lithium metal anode and the cathode; and a folded separation film continuously disposed between the unit cells adjacent to each other.

However, unlike the generally known stack-folding type electrode assembly, the electrode assembly includes insulating tapes attached to the upper and lower sides of the folded separator, respectively, and has a configuration in which the insulating tapes are exposed to the outside.

Drawings

Fig. 1 illustrates a general stack-folding type electrode assembly in a plan view.

Fig. 2a shows that before the lithium metal battery according to the exemplary embodiment of the present invention is stacked-folded, insulating tapes are respectively attached to the upper and lower sides of the folded separator.

Fig. 2b shows an enlarged view of a part of fig. 2a for describing the width of the insulating tape.

Fig. 3 shows one stack-folded side after attaching insulating tapes to the upper and lower sides of the folded separator according to fig. 2, respectively.

Fig. 4 shows electrochemical evaluation results of respective lithium metal batteries according to an exemplary embodiment of the present invention and one comparative example (in detail, fig. 4a shows a charge capacity evaluation result, fig. 4b shows a discharge capacity evaluation result, fig. 4c shows an OCV evaluation result after a charge and discharge pause time (30 minutes), and in respective drawings, comparative example 1 is represented as "reference (Ref.)" and example 1 is represented as "New test (New Exp.)".

Detailed Description

In this specification, unless explicitly described to the contrary, the word "comprise" and variations such as "comprises" or "comprising", will be understood to imply the inclusion of stated elements but not the exclusion of any other elements. "about" and "substantially" as used in the specification refers to values that are the same or close to the particular tolerances permitted in manufacture and materials, and also to prevent unscrupulous infringers from unjustifiably using the present disclosure, where precise or absolute numerical values are mentioned to aid in understanding the specification. As used throughout this specification, "step to" or "step of … …" does not mean "step for … …".

In the present specification, the term "combination thereof" included in the expression of markush form means a mixture or combination of one or more selected from the group consisting of the formulation components described in the markush form representation, and means including one or more selected from the group consisting of the formulation components.

Exemplary embodiments of the present invention will now be described in detail based on the above definitions. However, these embodiments are presented only as examples, and the present invention is not limited thereto but is limited only by the scope of claims described later.

Stack-folding type electrode assembly

The electrode assembly according to an exemplary embodiment is based on a stack-folding type electrode assembly including a plurality of unit cells respectively including: a lithium metal negative electrode; a positive electrode; and a separator disposed between the lithium metal negative electrode and the positive electrode, and the electrode assembly includes a folded separator continuously disposed between the unit cells adjacent to each other.

However, unlike the conventional stack-folding type electrode assembly, the electrode assembly according to the exemplary embodiment includes insulating tapes attached to the upper and lower sides of the folded separator, and has a structure in which the insulating tapes are exposed to the outside.

As shown in fig. 1, when a lithium metal battery is obtained according to a generally known stack-folding scheme, lithium dendrites and Dead lithium (Dead lithium) generated on the surface of a negative electrode during charge and discharge (lithium that may no longer participate in charge and discharge) may be exposed on the upper and lower sides of an electrode assembly.

In detail, lithium dendrites grown on the surface of an anode by repeated charge and discharge are grown or pushed out in a horizontal direction under pressure and are exposed to the upper and lower sides, i.e., the opening portions of the stack-folding type electrode assembly contacting the cathode or the cathode current collector, respectively, thereby causing a fine short circuit or a complete short circuit in the battery. Thus, it has been pointed out that the life of a battery in which a short circuit has occurred may not be maintained in any way.

In contrast, in the exemplary embodiment of the present invention, as shown in fig. 2A, the stack-folding type electrode assembly is obtained by: insulating tapes are attached to the upper and lower sides of the folded separator, a plurality of unit cells are stacked on the folded separator, and they are folded.

In detail, the stack-folding type electrode assembly according to an exemplary embodiment of the present invention is a stack-folding type electrode assembly, and includes: a plurality of unit cells; and a folded separation film included in the unit cells and continuously disposed between the adjacent unit cells.

Specifically, the unit cells respectively include lithium metal cathodes and anodes, insulating tapes are respectively attached to the upper and lower sides of the folded separators, and the insulating tapes respectively attached to the upper and lower sides of the folded separators are disposed at the upper and lower sides of the electrode assembly.

In other words, the insulating tapes attached to the upper and lower sides of the folded separator, respectively, are disposed on the upper and lower sides as the opening portion of the stack-folding type electrode assembly, as shown in fig. 3.

The stack-folding type electrode assembly obtained as described above can improve the life of the battery by suppressing exposure of lithium dendrites and dead lithium generated on the surface of the negative electrode during charge and discharge.

The unit cells may be implemented as a stack-folding type electrode assembly by alternately coupling the unit cells to the first side of one side of the folded separation film or to the first and second sides thereof, bending the folded separation film, or winding it.

Generally, a unit cell is divided into a single cell (mono-cell) and a bi-cell (bi-cell), and the single cell represents a structure in which electrodes at respective ends are stacked to form a positive electrode and a negative electrode, such as a positive electrode/a separator/a negative electrode, or a positive electrode/a separator/a negative electrode/a separator/a positive electrode/a separator/a negative electrode. In contrast, the bicells denote a structure in which electrodes of respective ends are stacked to form the same electrode, and are classified into a negative type bicell formed of a positive electrode/a separation film/a negative electrode/a separation film/a positive electrode, and a positive type bicell formed of a negative electrode/a separation film/a positive electrode/a separation film/a negative electrode.

In the stack-folding type electrode assembly according to the exemplary embodiment of the present invention, as shown in fig. 2A, the unit cell may be a bi-cell including two positive electrodes or two lithium metal negative electrodes.

Implementing the unit cells as the bicells, respectively, may improve battery capacity as compared to the mono-cell (mono-cell), but the exemplary embodiment is not limited thereto.

Further, when lithium dendrites are grown on the surface of a lithium metal negative electrode while driving a battery including a stack-folding type electrode assembly according to an exemplary embodiment, it is necessary to suppress the lithium dendrites from protruding to the outside of the electrode assembly.

For this, the width of the insulating tape may be formed to be equal to a gap (gap) between a vertical length of the lithium metal negative electrode and a vertical length of the folded separation film. Here, the concept of "width of insulating tape" can be understood by referring to fig. 2B which is an enlarged portion of a part of fig. 2A.

When insulating tapes having a width smaller than a gap between a vertical length of the lithium metal negative electrode and a vertical length of the folded separator are attached to upper and lower sides of the folded separator, respectively, lithium dendrites may protrude to the outside of the folded separator, similarly to the case where the insulating tapes are not used, thereby sequentially generating defects such as internal short circuit of the lithium metal battery, reduction in discharge capacity, and reduction in battery life.

In contrast, when the insulating tapes are attached to the upper and lower sides of the folded separator, respectively, and the width of the insulating tapes is controlled to be equal to the gap between the vertical length of the lithium metal negative electrode and the vertical length of the folded separator, lithium dendrites growing on the surface of the lithium metal negative electrode do not protrude to the outside of the electrode assembly, and the life span of the lithium metal battery can be improved as compared to the former case.

For example, the width of the insulating tape may be 500 μm to 5mm, and may be changed according to the respective thicknesses of the negative electrode and the separator established in the battery design.

Further, the thickness of the insulating tape may be determined within a range that does not affect the increase in thickness of the entire stack-folding type electrode assembly. In detail, when the thickness of the insulating tape is equal to or less than that of the anode, the increase in thickness of the entire stack-folding type electrode assembly may not be affected.

In more detail, the thickness of the insulating tape may be 0.1 to 1 (i.e., the thickness of the insulating tape may be 0.1 to 1 times the thickness of the anode) as a relative ratio with respect to the thickness of the lithium metal anode, and it may occupy a thickness of 3-5% of the entire thickness of the stack-folding type electrode assembly.

In more detail, the thickness of the insulating tape may be 20 to 100 μm. The thickness within this range is sufficient to suppress protrusion of dendrites (dendrorite), and may be suitable for appropriately forming the thickness of the entire stack-folding type electrode assembly after assembly. However, the exemplary embodiments are not limited thereto.

The insulating tape is generally used in the field of batteries, and may include at least one of Polyimide (PI), polypropylene (PP), and polyethylene terephthalate (PET). However, the exemplary embodiments are not limited thereto.

The fitting of the electrode assembly other than the insulating tape may be appropriately selected according to what is known to those skilled in the art.

For example, respective electrode tabs protruding from the lithium metal negative and positive electrodes may be included, and a part or the whole of the protruding part may be exposed to the upper side of the electrode assembly.

In an exemplary embodiment, the positive electrode and the lithium metal negative electrode included in each unit cell are not particularly limited, and electrodes manufactured by a conventional method known to those skilled in the art may be used.

The lithium metal anode may include an anode current collector and a lithium metal (Li-metal) thin film disposed on the anode current collector. The lithium metal anode may be produced by placing a lithium metal (Li-metal) thin film on an anode current collector comprising copper, gold, nickel or a copper alloy and pressurizing it.

Further, the positive electrode may be manufactured by: a positive electrode active material and materials such as a binder, a conductive material, etc. are mixed in an organic solvent to manufacture a positive electrode active material slurry, and the slurry is applied to a positive electrode current collector.

Here, aluminum and nickel may be used in a non-limiting example of the positive electrode current collector.

Further, non-limiting examples of the positive active material include lithium manganese oxide, lithium cobalt oxide, lithium nickel oxide, lithium iron oxide, a mixture thereof, or a composite thereof.

Lithium metal battery, battery module, battery pack, and the like

In another exemplary embodiment of the present invention, a lithium metal battery is provided in which a stack-folding type electrode assembly is received in a case.

The housing may be of the bag (pouch) type. In addition, the liquid electrolyte may be impregnated in the folded separator. For example, after the stack-folding type electrode assembly according to the exemplary embodiment is received in the pouch type case, a liquid electrolyte may be injected, and thus a lithium metal battery may be provided.

The lithium metal battery may be used as a unit cell of a power source for small-sized devices, and may also be used as a unit cell in a middle or large-sized battery module including a plurality of battery cells. In addition, a battery pack including the battery module may be configured.

As known to those skilled in the art, a liquid electrolyte may be used by dissolving a lithium salt in a non-aqueous organic solvent. For example, the negative ion of the lithium salt may be selected from F^-、Cl^-、Br^-、I^-、NO₃ ^-、N(CN)^2-、BF₄ ^-、ClO₄ ^-、PF₆-、(CF₃)₂PF₄ ^-、(CF₃)₃PF₃ ^-、(CF₃)₄PF₂ ^-、(CF₃)₅PF^-、(CF₃)₆P^-、CF₃SO₃ ^-、CF₃CF₂SO₃ ^-、(CF₃SO₂)₂N^-、(FSO₂)₂N^-、CF₃CF₂(CF₃)₂CO^-、(CF₃SO₂)₂CH^-、(SF₅)₃C^-、(CF₃SO₂)₃C^-、CF₃(CF₂)₇SO₃ ^-、CF₃CO₂ ^-、CH₃CO₂ ^-、SCN^-And (CF)₃CF₂SO₂)₂N^-。

In the case of a non-aqueous organic solvent, one or a mixture of at least two of Propylene Carbonate (PC), Ethylene Carbonate (EC), diethyl carbonate (DEC), dimethyl carbonate (DMC), Ethyl Methyl Carbonate (EMC), methyl propyl carbonate, dipropyl carbonate, dimethyl sulfoxide, acetonitrile, dimethoxyethane, diethoxyethane, vinylene carbonate, sulfolane, γ -butyrolactone, propylene sulfite, and tetrahydrofuran may be generally used. In particular, among carbonate-based organic solvents, ethylene carbonate and propylene carbonate, which are cyclic carbonates, are organic solvents having high viscosity, having high dielectric characteristics, and well dissociating lithium salts in an electrolyte, and thus they may be preferably used, and when a linear carbonate (e.g., dimethyl carbonate or diethyl carbonate) having low viscosity and low dielectric characteristics is mixed with a cyclic carbonate in an appropriate ratio and then used, an electrolyte solution having high conductivity may be prepared, and may be more preferably used.

Optionally, the liquid electrolyte may further include additives included in conventional liquid electrolytes, such as overcharge inhibitors.

Exemplary embodiments according to the present invention, comparative examples, and test examples for evaluating them will now be described. However, the embodiments to be described below are exemplary embodiments of the present invention, and the present invention is not limited to the embodiments to be described.

Comparative example 1: preparation of a porous folded separator made of polyethylene Material without an insulating tape attached thereto

A porous separation film (width x vertical length x thickness: 461.5mm x 54mm x 12 μm, porosity: 38%) made of a polyethylene material was prepared and used as the folded separation film of comparative example 1.

Comparative example 2: stack-folding type electrode assembly including folded separation film of comparative example 1, and battery including the same Manufacture of lithium metal battery with folding type electrode assembly

By mixing LiNiCoMnO₂(positive electrode active material), Super-P (conductive material), and PVdF (binder) were mixed in a solvent NMP (N-methyl-2-pyrollidone, N-methyl-2-pyrrolidone) at a weight ratio of 96:2:2 to manufacture positive electrode composite slurry. The positive electrode composite slurry was applied to each side or one side of an aluminum foil (thickness: 12 μm) by using a doctor blade (doctor blade) at a condition of 3 m/min. Here, "applying the positive electrode composite slurry to each side or one side of aluminum foils (thickness: 12 μm)" means preparing a plurality of aluminum foils, manufacturing a double-sided positive electrode by "applying the positive electrode composite slurry to" each side of some aluminum foils ", and manufacturing a single-sided positive electrode by" applying the positive electrode composite slurry to "one side of other aluminum foils". The amount of the aluminum foil supported was set to be the same, i.e., 0.478g/25cm²。

The aluminum foil to which the positive electrode composite slurry was applied was dried in a vacuum oven at a temperature of 50 ℃ for 20 minutes and pressed by using a Roll press (Roll press) at a temperature of 90 ℃ and under a pressure condition of 5.0MPa for 3 seconds (sec) to obtain a positive electrode.

On the other hand, lithium foils (thickness: 20 μm) were disposed on respective sides of a copper foil (thickness: 8 μm), and pressed for 3 seconds (sec) at a temperature of 90 ℃ and under a pressure condition of 5.0MPa by using a Roll press (Roll press) to obtain a lithium metal negative electrode.

Seven positive bicells (including two single-sided positive bicells) and four lithium metal negative bicells were assembled, respectively, by using a porous separation film (width x vertical length x thickness: 461.5mm x 54mm x 12 μm, porosity: 38%) made of the same polyethylene material as the folded separation film of comparative example 1.

By using the folded separation film of comparative example 1, a positive electrode bicell and a lithium metal negative electrode bicell were sequentially folded as shown in fig. 1, thereby obtaining an electrode assembly of comparative example 2.

The electrode assembly of comparative example 2 was mounted in a pouch-type battery case, and an electrolyte in which 3.4-M Lithium bis (fluorosulfonyl) imide (LiFSI) as a high concentration Ether (Ether) -based electrolyte was dissolved in 1,2-DIMETHOXYETHANE (1,2-DIMETHOXYETHANE, DME) was injected to complete the Lithium metal battery of comparative example 2.