KR20230019726A - Separator for lithium ion battery containing aluminium oxide and tris(2,4,6-trimethylphenyl)phosphine, manufacturing method thereof and lithium ion battery including the same - Google Patents

Abstract

In the present invention, a radical-scavenging Al_2O_3-TMPP functional PE separator is modified by preparing an Al_2O_3-TMPP composite and embedding the same into a PE separator through a dip coating process. According to SEM, EDS, XRD, and FT-IR analysis, it can be seen that Al_2O_3-TMPP is well coated on the PE separator. The Al_2O_3-TMPP-embedded PE separator has a lower contact angle and a higher electrolyte impregnation rate than a bare PE separator, which indicates that a more hydrophilic surface was developed in the Al_2O_3-TMPP-embedded PE separator. While a cycling cell using an Al_2O_3-TMPP embedded separator shows stable cycling behavior after 150 cycles (59.8 %) at high temperature, the cycling cells using bare PE separators show that the cycling retention rate continues to decrease (47.1 %). Therefore, because the use of the Al_2O_3-TMPP-embedded PE separator can effectively reduce the radical concentration through a chemical scavenging process, it is an effective way to improve cell cycling.

Description

Separator for lithium secondary battery containing aluminum oxide and tris (2,4,6-trimethylphenyl) phosphine, manufacturing method thereof, and lithium secondary battery including the same 6-TRIMETHYLPHENYL)PHOSPHINE, MANUFACTURING METHOD THEREOF AND LITHIUM ION BATTERY INCLUDING THE SAME}

The present invention is a separator for a lithium secondary battery comprising a composite of aluminum oxide (Al ₂ O ₃ ) and tris (2,4,6-trimethylphenyl) phosphine (TMPP), the It is an invention related to a manufacturing method and a lithium secondary battery including the same.

Although the application of lithium ion batteries (LIBs) has grown rapidly from small scale to large scale, increasing the energy density of cells is emerging as an important issue in the battery industry. For this reason, many advanced electrode materials have been developed that can greatly improve the cell's energy density, providing the cell's higher specific capacity and voltage. Layered Ni-Co-Mn oxide materials are currently considered as alternative candidates for improved anode materials based on their high specific capacity. Advanced cathode materials include Li metal or alloy materials (i.e. Si, SiO, Sn) based on specific capacities at least five times higher than conventional graphite cathodes. However, with the increasing use of advanced electrode materials in cells, difficulties arise in achieving stable cycling behavior due to the high reactivity of these advanced materials.

High energy density based cells consist of a higher amount of electrochemically active species in the cell, which accelerates unwanted reactions during the electrochemical charge/discharge process compared to conventional LIBs. From the point of view of the surface reaction occurring at the electrode-electrolyte interface, a much larger amount of unstable charged active species can cause electrolyte decomposition in the cell, rapidly reducing the cycling performance. In particular, when the electrolyte decomposes in the cell, one of the decomposed additives is an unstable radical species derived from an open-ring carbonate, which further chemically decomposes the electrolyte through a chemical reaction.

This means that for LIBs designated to provide high energy densities, controlling the amount of chemically reactive radical species in the cell is very important.

Republic of Korea Patent Publication No. 10-2020-0112749

In the present invention, it is proposed to improve the cycling performance of a high energy density based cell by incorporating a radical reactive functionalized separator. In the present invention, we propose the use of tris(2,4,6-trimethylphenyl)phosphine (TMPP) as a radical scavenger because the low oxidation state of elemental phosphorus (P) readily allows chemical bonding with radical species. However, the possibility of directly embedding the radioactive scavenger into the PE membrane through chemical modification is slim. This is because the PE membrane is composed only of hydrocarbon components with extremely stable chemical moments.

Therefore, since the hydroxyl functional group (-OH) on the surface of Al ₂ O ₃ can serve as a chemical reaction site for the condensation reaction with TMPP, Al ₂ O ₃ is often used to attach TMPP to the PE membrane. . It also strengthens mechanical properties that can spontaneously improve cell safety performance. This means that the development of an Al ₂ O ₃ -TMPP-embedded PE separator can be an effective method for improving electrochemical properties and cell performance.

Here, we present a convenient method for fabricating Al ₂ O ₃ -TMPP composites by one-step condensation through a simple dip coating process. After preparing the PE-Al ₂ O ₃ -TMPP functionalized separator, the basic properties are confirmed through systematic analysis and the electrochemical compatibility is explained using a nickel-rich NCM cathode material that can provide high energy density in the cell.

In order to solve the above technical problem, the present invention includes aluminum oxide (Al ₂ O ₃ ) and tris (2,4,6-trimethylphenyl) phosphine (Tris (2,4,6-trimethylphenyl) phosphine, TMPP) composite It provides a separator for a lithium secondary battery that does.

In the present invention, the radical-scavenging Al ₂ O ₃ -TMPP functional PE separator is modified by preparing an Al ₂ O ₃ -TMPP composite and embedding it in the PE separator through a dip coating process.

The separator for a lithium secondary battery is coated with a composite of aluminum oxide (Al ₂ O ₃ ) and tris (2,4,6-trimethylphenyl) phosphine (TMPP) on the separator. characterized by

The aluminum oxide (Al ₂ O ₃ ) and tris (2,4,6-trimethylphenyl) phosphine (Tris (2,4,6-trimethylphenyl) phosphine, TMPP) composite is characterized by being embedded in the separator .

On the surface of the lithium secondary battery separator, aluminum oxide (Al ₂ O ₃ )-tris (2,4,6-trimethylphenyl) phosphine having an average thickness of 5 μm, TMPP) layer is disposed.

A separator for a lithium secondary battery comprising a composite of aluminum oxide (Al ₂ O ₃ ) and tris (2,4,6-trimethylphenyl) phosphine (TMPP) is aluminum oxide ( The contact angle is reduced compared to a separator for a lithium secondary battery that does not contain a complex of Al ₂ O ₃ and Tris (2,4,6-trimethylphenyl) phosphine (TMPP). to be characterized

According to another embodiment of the present invention, aluminum oxide (Al ₂ O ₃ ) and tris (2,4,6-trimethylphenyl) phosphine (Tris (2,4,6-trimethylphenyl) phosphine, TMPP) through a condensation reaction preparing a composite; And coating the aluminum oxide (Al ₂ O ₃ ) and tris (2,4,6-trimethylphenyl) phosphine (Tris (2,4,6-trimethylphenyl) phosphine, TMPP) composite on the surface of a separator for a lithium secondary battery. Provides a method for manufacturing a separator for a lithium secondary battery comprising;

On the surface of the lithium secondary battery separator, aluminum oxide (Al ₂ O ₃ )-tris (2,4,6-trimethylphenyl) phosphine having an average thickness of 5 μm, TMPP) layer is disposed.

A separator for a lithium secondary battery comprising a composite of aluminum oxide (Al ₂ O ₃ ) and tris (2,4,6-trimethylphenyl) phosphine (TMPP) is aluminum oxide ( Al ₂ O ₃ ) and tris (2,4,6-trimethylphenyl) phosphine (Tris (2,4,6-trimethylphenyl) phosphine, TMPP), the contact angle is reduced compared to the separator for lithium secondary batteries that does not contain the complex to be characterized

According to another embodiment of the present invention, the anode; cathode; and an electrolyte layer and a separator disposed between the positive electrode and the negative electrode, wherein the separator is a separator according to an embodiment of the present invention.

The positive electrode is characterized by including LiNi _0.8 Co _0.1 Mn _0.1 O ₂ (NCM811).

According to SEM, EDS, XRD and FT-IR analysis in the present invention, it can be seen that Al ₂ O ₃ -TMPP is well coated on the PE separator.

The Al ₂ O ₃ -TMPP-embedded PE separator has a lower contact angle and a higher electrolyte impregnation rate than the bare PE separator, indicating that a more hydrophilic surface has been developed in the Al ₂ O ₃ -TMPP-embedded PE separator.

The cycling cell using the Al ₂ O ₃ -TMPP-embedded PE separator showed stable cycling behavior after 150 cycles (59.8%) at high temperature, whereas the cycling cell using the bare PE separator showed a continuous decrease in cycling retention (47.1%). )do.

Therefore, using the Al ₂ O ₃ -TMPP-embedded PE separator is an effective method to improve cell cycling because the radical concentration can be effectively lowered through a chemical scavenging process.

1 is a schematic diagram for the radical scavenging performance of an Al ₂ O ₃ -TMPP embedded PE separator.
Figure 2 is the UV-Vis absorption spectrum of DPPH and DPPH using TMPP (inset: color change before and after chemical reaction with TMPP).
3 shows (a) a SEM image of a bare PE separator and (b) an SEM/EDS image of an Al ₂ O ₃ -TMPP-embedded PE separator. (c) XRD spectrum of bare PE separator and Al ₂ O ₃ -TMPP embedded PE separator, (d) FT-IR spectrum of bare PE separator and Al ₂ O ₃ -TMPP embedded PE separator.
4 is a diagram showing physicochemical properties of a bare PE separator and an Al ₂ O ₃ -TMPP embedded PE separator: (a) contact angle, (b) electrolyte acceptance, (c) ionic conductivity, and (d) Gurley number.
FIG. 5 is a diagram showing the electrochemical performances of a bare PE separator and an Al ₂ O ₃ -TMPP-embedded PE separator at high temperature: (a) potential profile and (b) cycle retention.

Hereinafter, the present invention will be described in more detail through examples. However, these examples are only for helping the understanding of the present invention, and the scope of the present invention is not limited to these examples in any sense.

Experimental Example

The chemical reaction of TMPP was performed as follows: 0.1 g TMPP (Aldrich) was added to 10 mL ethanol followed by 0.02 g 2,2-diphenyl-1-picrylhydrazyl (DPPH, TCI). The mixture was mechanically stirred at room temperature for 1 hour and then analyzed by UV-Vis spectrophotometry (KLAB, OPTZEN POP-V) to confirm the change in the chemical structure of TMPP. The Al ₂ O ₃ -TMPP-embedded PE separator was prepared by first fabricating the Al ₂ O ₃ -TMPP composite as follows: 0.1 g TMPP was placed in a beaker and 0.5 g Al ₂ O ₃ was added. The resulting mixture was kept at 25° C. for 12 hours to allow the condensation reaction to proceed. Upon completion of the condensation reaction, the Al ₂ O ₃ -TMPP compound was recovered by filtration. The Al ₂ O ₃ -TMPP composite was incorporated into the PE separator as follows: 0.5 g poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP) was mixed with 60 mL acetone and 0.5 g Al ₂ O ₃ - TMPP composite was added to PVDF-HFP.

The mixture was mechanically agitated for at least 3 h, then bare PE separators (6 cm Х 3 cm) were immersed in a binder solution and coated with the Al ₂ O ₃ -TMPP composite. The dip-coated PE separator was dried at room temperature for 1 hour. The thickness of the Al ₂ O ₃ -TMPP composite coated PE separator was 20 μm, and the load of the Al ₂ O ₃ -TMPP embedded PE separator was 0.29 ± 0.05 mg cm ^-2 .

The surface morphology of the separator was analyzed by scanning an electron microscope (SEM, JSM-7800F, JEOL) with energy dispersive X-ray spectroscopy (EDS). The structure and chemical composition of the membrane were also analyzed by X-ray diffraction (Cu Kα) (XRD, SmartLab, Rigaku) and Fourier transform infrared spectroscopy (FT-IR, VUCTUS 80V, Bruker). The contact angle and thickness of each separator were measured with a contact angle meter (SEO 300A, SEO Co.) and a micrometer (Mitutoyo, 543-390), respectively. The electrolyte impregnation rate of the separator was calculated by measuring the weight change before and after immersion in the electrolyte.

The ionic conductivity of each separator was measured by electrochemical impedance spectroscopy using Li metal, an electrolyte (EC:EMC=1:2 + 1 M LiPF6, assimilation electrolyte) and a symmetrical cell assembled with each separator. AC impedance was measured using a potentiostat (Wonatech, ZiveMP1) ranging from 1 MHz to 10 ^-1 Hz at an amplitude of 10 mV. The ionic conductivity was calculated by the following equation: σ = d / (R A), where σ = ionic conductivity, d = thickness of the separator, R = electrolyte resistance, and A = area of the separator.

The Gurley number of each membrane was measured with a Gurley formula densitometer (Toyoseiki).

The electrochemical performance was evaluated by preparing an NCM811 positive electrode as follows: 1.8 g NCM811 (LiNi _0.8 Co _0.1 Mn _0.1 O ₂ , L&F), 0.1 g carbon conductive agent (Super P), and 0.1 g poly(vinylidine fluoride). Dispersed in 1.6mL N-methylpyrrolidone (Aldrich) and stirred for 3 hours. NCM811 anode paste was then coated on the Al current collector. The coated NCM811 anode was dried at 120 °C for 3 hours and further dried in a vacuum oven at 120 °C for 12 hours, and the loading of the anode was 9.0 ± 0.3 mg cm ^-2 . A 2032 half-cell composed of NCM811 anode (1.1304 cm ² ), Li cathode (1.5386 cm ² ), electrolyte (150 μL) and each separator (2.5434 cm ² ) was assembled. The cell was pre-charged/discharged at 0.1 C (1.0 C = 180 mA g ^-1 ) current rate for two cycles and cycled at 1.0 C current rate for 100 cycles. Cells were charged/discharged in the range of 3.0 to 4.3V (vs. Li/Li ⁺ ) in constant current-constant voltage (CCCV) mode for charging and constant current (CC) mode for discharging.

Results and discussion

Figure 1 shows a schematic diagram for the radical scavenging performance of the Al ₂ O ₃ -TMPP embedded PE separator. The difficulty in surface functionalization of PE separators is due to their inherent properties (due to the extremely stable properties of PE). Therefore, first, TMPP-embedded Al ₂ O ₃ was prepared by a simple one-step condensation process, and then TMPP-embedded Al ₂ O ₃ was coated on the PE separator by dip coating using PVdF-HFP as a binder. In the present invention, it is assumed that when Al ₂ O ₃ -TMPP is bonded to the PE separator, radical species generated by unwanted reactions occurring during the electrochemical charge/discharge process can be easily scavenged to increase the overall electrochemical performance of the cell. .

In the present invention, DPPH (2,2-diphenyl-1-picrylhydrazyl) is used as an indicator to determine whether TMPP can effectively scavenge radical species by chemical reactions within cells. it was clarified whether DPPH has a reactive radical species on the central N atom, and when it is removed by a chemical reaction, the binding state of DPPH changes rapidly. Therefore, DPPH can serve as an effective indicator to estimate whether radicals have been removed by simply monitoring the color of a DPPH-based solution.

In the case of the present invention, DPPH is initially usually purple in solution, but turns yellow after adding TMPP (FIG. 2). The UV-Vis spectrum shows the maximum wavelength of the DPPH solution at 517 nm, but red-shifted to 459 nm. This means that TMPP reacts with DPPH through a chemical reaction and changes the binding state of the corresponding DPPH according to the proposed mechanism.

Based on these results, the Al ₂ O ₃ -TMPP composite was coated on the PE separator. The thickness of the bare PE separator was 15 μm and increased to 20 μm after coating with the Al ₂ O ₃ -TMPP composite. Successful coating with Al ₂ O ₃ -TMPP was also confirmed by SEM and EDS analysis. That is, on the surface of the lithium secondary battery separator, aluminum oxide (Al ₂ O ₃ )-tris(2,4, It can be seen that a 6-trimethylphenyl) phosphine (Tris (2,4,6-trimethylphenyl) phosphine, TMPP) layer is disposed.

3a and 3b show that Al ₂ O ₃ -TMPP is well distributed in the PE membrane along the PVdF-HFP network. In addition, the XRD pattern confirmed that Al ₂ O ₃ -TMPP was successfully introduced into the PE separator (FIG. 3c).

The Al ₂ O ₃ -TMPP-embedded PE separator (shown in red) shows intrinsic PE peaks at 21.6° and 24° (shown in black) commonly observed for bare PE separators.

Also, the Al ₂ O ₃ -TMPP-embedded PE membrane shows new peaks at 10.3° and 10.8° that can be assigned to Al ₂ O ₃ and TMPP, respectively. CF peaks found at 1405 cm ^-1 , 1185 cm ^-1 , 1031 cm ^-1 (originating from the PVdF-HFP binder) as well as aromatic C=C and CH peaks at 1604 cm ^-1 and 879 cm ^-1 (from TMPP) Since a new peak corresponding to ) is observed, the FT-IR spectrum (FIG. 3d) also provides a spectrum that further confirms that Al ₂ O ₃ -TMPP was successfully introduced into the PE separator. These results indicate that the Al ₂ O ₃ -TMPP-embedded PE separator was well prepared by a simple dip coating process.

4 shows the physicochemical properties of the Al ₂ O ₃ -TMPP-embedded PE separator. In the contact angle analysis of the PE-based separator, the contact angle of the Al ₂ O ₃ -TMPP-embedded PE separator was 42°, lower than that of the bare PE separator (46°) (FIG. 4a). Since the contact angle is measured using a conventional hydrophilic carbonate-based electrolyte and two separators (Al ₂ O ₃ -TMPP-embedded PE separator and bare PE separator), the decrease in the contact angle of the Al ₂ O ₃ -TMPP-embedded PE separator means that the Al This means that the surface of the ₂ O ₃ -TMPP-embedded PE separator has higher hydrophilicity than that of the bare PE separator due to the introduction of Al ₂ O ₃ .

In other words, the Al ₂ O ₃ -TMPP-embedded PE separator overcomes the hydrophobic surface state of the bare PE separator by introducing the hydrophilic Al ₂ O ₃ -TMPP composite, which is more advantageous for the uptake of existing carbonate-based electrolytes. have

In fact, the electrolyte impregnation performance is higher for the Al ₂ O ₃ -TMPP-embedded PE separator (388%) than the bare PE separator (353%) after 1 hour, which is simply the result of using the Al ₂ O ₃ -TMPP composite (Fig. 4b). This means that the wettability between the separator and the electrolyte is significantly improved only by surface modification.

In terms of ion conductivity, the Al ₂ O ₃ -TMPP-embedded PE separator exhibited 0.59 mS cm ^-1 , which slightly increased the ion conductivity compared to the bare PE separator (0.57 mS cm ^-1 ).

Although the Gurley number (time to pass 100 cc of air from one side to the other) of the Al ₂ O ₃ -TMPP-embedded PE separator is 308 seconds 100 cc ^-1 (bare PE separator: 272 seconds 100 cc ^-1 ) However, even when Al ₂ O ₃ -TMPP is additionally formed on the PE separator, it does not significantly affect the movement of Li-ions generated during the electrochemical process.

5 shows the electrochemical performances of bare PE and Al ₂ O ₃ -TMPP embedded PE separators. The initial potential profile shows that the charge and discharge curves of the cells are nearly identical, indicating that no unwanted reactions occur in the electrochemical process.

The cycling performance shows that the cycling retention rate of the cells cycled with the bare PE separator continued to decrease, reaching 47.1% after 150 cycles. It should be noted that electrolyte decomposition continuously occurs even on the NCM811 anode surface due to the instability of the Ni ⁴⁺ species in the charged state.

Once the electrolyte is decomposed, it provides radical intermediates in the cell, which trigger additional decomposition reactions during the electrochemical charge/discharge process. This indicates that the concentration of radical species is not effectively controlled in a cell cycling with a bare PE separator.

Conversely, the cell using the Al ₂ O ₃ -TMPP-embedded PE separator showed stable cycle operation even after 150 cycles at high temperature, and showed a cycle retention rate of 59.8% at the end of the cycle. These results indicate that the use of the Al ₂ O ₃ -TMPP-embedded PE separator is an effective method for improving cell cycle conservation because it can effectively lower the active concentration of radical species through a chemical scavenging process.

conclusion

In order to reduce radical species in the cell, an Al ₂ O ₃ -TMPP functionalized PE separator was proposed. Al ₂ O ₃ is considered an effective material for chemical modification of PE membranes because the hydroxyl functional group (-OH) formed on the surface of Al ₂ O ₃ can serve as a chemical reaction site for the condensation reaction with the radical scavenger. do. Here, TMPP is used as a scavenger because the low oxidation state of P element easily allows chemical bonding with radical species and TMPP also easily combines with Al ₂ O ₃ through condensation reaction. The Al ₂ O ₃ -TMPP composite is easily prepared in a one-step process and coated on the PE separator through a dip coating process.

The success of the Al ₂ O ₃ -TMPP coating was confirmed by SEM, EDS, XRD, FT-IR, and thickness analysis. The Al ₂ O ₃ -TMPP-embedded PE separator exhibited a relatively lower contact angle than the bare PE separator, indicating that the surface of the Al ₂ O ₃ -TMPP-embedded PE separator became more hydrophilic than that of the bare PE separator.

In fact, the Al ₂ O ₃ -TMPP-embedded PE separator exhibits higher electrolyte impregnation performance (388%) than the bare PE separator (353%) after 1 hour, which is simply surface modification with the Al ₂ O ₃ -TMPP composite. This means that the wettability between the separator and the electrolyte is improved.

Based on the improvement in electrolyte wettability, the Al ₂ O ₃ -TMPP-embedded PE separator has improved ion conductivity (0.59 mS cm ^-1 ) compared to the bare PE separator (0.57 mS cm ^-1 ), which indicates that the Al ₂ O ₃ -TMP- This implies that embedded PE separators can be used in existing LIBs.

Cells cycled using bare PE separators show a continuous decrease in cycle retention to 47.1% after 150 cycles at high temperatures. On the other hand, the cell cycled with the Al ₂ O ₃ -TMPP-embedded PE separator showed stable cycle operation even after 150 cycles at high temperature, and a cycle retention rate of 59.8% was observed at the end of the cycle.

These results indicate that the use of the Al ₂ O ₃ -TMPP-embedded PE separator is an effective method for improving the cycle conservation of a cell because it can effectively lower the radical concentration through a chemical scavenging process.

The present invention described above is not limited to the above-described embodiments, since various substitutions and changes can be made to those skilled in the art within the scope of the technical idea of the present invention. .

Claims (10)

A separator for a lithium secondary battery comprising a composite of aluminum oxide (Al ₂ O ₃ ) and tris (2,4,6-trimethylphenyl) phosphine (TMPP).
According to claim 1,
The separator for a lithium secondary battery is coated with a composite of aluminum oxide (Al ₂ O ₃ ) and tris (2,4,6-trimethylphenyl) phosphine (TMPP) on the separator. A separator for a lithium secondary battery, characterized in that.
According to claim 1,
The aluminum oxide (Al ₂ O ₃ ) and tris (2,4,6-trimethylphenyl) phosphine (Tris (2,4,6-trimethylphenyl) phosphine, TMPP) composite is characterized in that embedded in the separator Separator for lithium secondary battery.
According to claim 1,
On the surface of the lithium secondary battery separator, aluminum oxide (Al ₂ O ₃ )-tris (2,4,6-trimethylphenyl) phosphine having an average thickness of 5 μm, A separator for a lithium secondary battery, characterized in that a TMPP) layer is disposed.
According to claim 1,
A separator for a lithium secondary battery comprising a composite of aluminum oxide (Al ₂ O ₃ ) and tris (2,4,6-trimethylphenyl) phosphine (TMPP) is aluminum oxide ( The contact angle is reduced compared to a separator for a lithium secondary battery that does not contain a complex of Al ₂ O ₃ and Tris (2,4,6-trimethylphenyl) phosphine (TMPP). Characterized by a separator for a lithium secondary battery.
Preparing a composite of aluminum oxide (Al ₂ O ₃ ) and tris (2,4,6-trimethylphenyl) phosphine (TMPP) through a condensation reaction; and
Coating the aluminum oxide (Al ₂ O ₃ ) and tris (2,4,6-trimethylphenyl) phosphine (TMPP) composite on the surface of a separator for a lithium secondary battery; containing
Method for manufacturing a separator for a lithium secondary battery.
According to claim 6,
On the surface of the lithium secondary battery separator, aluminum oxide (Al ₂ O ₃ )-tris (2,4,6-trimethylphenyl) phosphine having an average thickness of 5 μm, TMPP) method for manufacturing a separator for a lithium secondary battery, characterized in that the layer is disposed.
According to claim 6,
A separator for a lithium secondary battery comprising a composite of aluminum oxide (Al ₂ O ₃ ) and tris (2,4,6-trimethylphenyl) phosphine (TMPP) is aluminum oxide ( Al ₂ O ₃ ) and tris (2,4,6-trimethylphenyl) phosphine (Tris (2,4,6-trimethylphenyl) phosphine, TMPP), the contact angle is reduced compared to the separator for lithium secondary batteries that does not contain the complex Method for manufacturing a cathode material for a lithium secondary battery, characterized in that
anode; cathode;
Including an electrolyte layer and a separator disposed between the anode and the cathode,
The separator is a lithium secondary battery, characterized in that the separator according to any one of claims 1 to 5.
According to claim 9,
The positive electrode is a lithium secondary battery, characterized in that it comprises LiNi _0.8 Co _0.1 Mn _0.1 O ₂ (NCM811).

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