KR102465701B1 - Separator for lithium secondary battery using inorganic liquid electrolyte - Google Patents

Abstract

The present invention provides a separator for a lithium secondary battery, wherein (a) the lithium secondary battery includes a lithium salt-containing inorganic liquid electrolyte injected with sulfur dioxide; (b) the separator has a coating layer of a polymer material formed on both sides thereof; provides a separator for a lithium secondary battery, characterized in that.
According to the present invention, the wettability of the separator with respect to the electrolyte is greatly improved, and ultimately, the charge/discharge characteristics and cycle life of the lithium secondary battery are remarkably improved. It can be applied to energy storage devices of

Description

Separator for lithium secondary battery using inorganic liquid electrolyte

The present invention relates to a separator for a lithium secondary battery employing an inorganic liquid electrolyte and a method for manufacturing the same, and more particularly, to a separator surface of a lithium secondary battery employing an inorganic liquid electrolyte based on sulfur dioxide is coated with a polymer material It relates to a separator for a lithium secondary battery.

Recently, with the development of technology, the use of batteries is expanding not only in portable electronic devices, but also in power sources of electric vehicles and power storage devices of medium and large-sized energy storage systems. Therefore, studies on lithium secondary batteries that can meet various needs are being conducted, and in particular, battery safety has become an important issue. Specifically, in accordance with the need for high-output, large-capacity batteries in electric vehicles and medium-to-large energy storage systems as well as lightweight and miniaturization of batteries in portable electronic devices, the separator, one of the key components of lithium secondary batteries, has high safety and improved battery performance. Materials that can be improved are required.

In general, a lithium secondary battery includes an electrode assembly comprising a positive electrode, a negative electrode, and a separator disposed between the positive electrode and the negative electrode, and an electrolyte containing lithium salt. In such a lithium secondary battery, charging and discharging proceed while repeating the process of intercalating and deintercalating lithium ions between the positive electrode and the negative electrode. In this case, since the separator includes micropores, it provides a path for lithium ions to move through the pores and physically separates the positive electrode and the negative electrode to perform a function of electrically insulating. On the other hand, as the thickness of the separator decreases, the distance between the positive electrode and the negative electrode decreases, which is good in terms of high output and high energy density of the battery. There is this. On the other hand, when a thick separator is used, the volume of the electrode assembly itself increases, which may cause a problem in that the capacity to volume ratio is lowered.

In addition, even if the physical properties are satisfied, if wettability of the electrolyte is not secured, the electrochemical properties may be deteriorated. If the electrode is partially degraded due to the local depletion of the electrolyte or the reaction is locally concentrated, lithium metal may be precipitated, and there is a risk of dendritic growth of lithium. Therefore, the electrolyte must quickly permeate into the separator, and it must be maintained uniformly even after wet, and the interface between the electrode, the separator, and the electrolyte must be firmly maintained to achieve excellent charge/discharge characteristics and cycle life.

However, in the case of polyolefin-based separators currently commercialized for lithium secondary batteries, they have excellent chemical stability and mechanical strength, but poor affinity with electrolytes, especially inorganic liquid electrolytes, and poor thermal stability. In order to apply it, improvement is needed. For this purpose, conventionally, an example using a composite membrane coated with a polymer material or a ceramic is known as a polyolefin-based separator. However, most of these are developed for lithium secondary batteries using a non-aqueous electrolyte in which lithium salt is added to a mixed solvent of ethylene carbonate or propylene carbonate, which is a high dielectric solvent, and dimethyl carbonate or diethyl carbonate, which is a low-viscosity solvent. And there is a limit to the cycle life, and there have been no reports of cases developed for a lithium secondary battery employing an inorganic liquid electrolyte having excellent wettability of the separator.

Therefore, the present inventors as a separator for a lithium secondary battery employing an inorganic liquid electrolyte in which sulfur dioxide gas is injected into a lithium salt. When the surface of the separator is coated with a polymer material, the wettability of the separator with respect to the electrolyte is greatly improved, so that the sulfur dioxide-based The present invention was completed by focusing on that the charge/discharge characteristics and cycle life of a lithium secondary battery including an inorganic liquid electrolyte and a separator can be remarkably improved.

Patent Literature 1. Korean Patent Publication No. 10-2016-0109227 Patent Document 2. Korean Patent Registration No. 10-1470696 Patent Document 3. Japanese Patent Laid-Open No. 2016-081606

The present invention has been devised in view of the above problems, and an object of the present invention is to greatly improve the wettability of the separator with respect to the inorganic liquid electrolyte, and to significantly improve the charge/discharge characteristics and cycle life of the lithium secondary battery, especially at low temperature An object of the present invention is to provide a separator for a lithium secondary battery employing an inorganic liquid electrolyte based on sulfur dioxide that can be stably operated in the

The present invention for achieving the object as described above, in the separator for a lithium secondary battery, (a) the lithium secondary battery comprises a lithium salt-containing inorganic liquid electrolyte injected with sulfur dioxide; (b) the separator has a coating layer of a polymer material formed on both sides thereof; provides a separator for a lithium secondary battery, characterized in that.

The lithium salt is characterized in that at least one selected from the group consisting of LiAlCl ₄ , LiGaCl ₄ , Li ₂ CoCl ₄ , Li ₂ NiCl ₄ , Li ₂ CuCl ₄ , Li ₂ MnCl ₄ , Li ₂ ZnCl ₄ and LiAlBr ₄ .

The lithium salt-containing inorganic liquid electrolyte injected with the sulfur dioxide is LiAlCl ₄ -3SO ₂ It is characterized in that.

(b) the separator is selected from the group consisting of polyethylene, polypropylene, polyester, polyamide, polyimide, polycarbonate, polyacetal, polyethersulfone, polyetheretherketone, polyphenylene oxide, and polyphenylenesulfide It is characterized in that it is a porous substrate of more than one species.

The polymer material is polyethylene oxide, polyvinylpyrrolidone, polyacrylonitrile, polyvinylidene fluoride, polymethyl methacrylate, polyvinyl acetate, ethylene vinyl acetate copolymer, cellulose acetate, carboxymethyl cellulose and polyimide. It is characterized by at least one selected from the group consisting of.

The coating layer is characterized in that the thickness is 1 ~ 10㎛.

In addition, the present invention is a lithium secondary battery comprising an electrode assembly comprising a positive electrode, a negative electrode, a porous separator disposed between the positive electrode and the negative electrode, and an electrolyte, wherein the porous separator has a polymer material coating layer formed on both sides thereof, The electrolyte provides a lithium secondary battery, characterized in that the lithium salt-containing inorganic liquid electrolyte injected with sulfur dioxide.

In addition, the present invention provides an energy storage device including the lithium secondary battery.

According to the present invention, a polymer material is coated on a conventional porous separator substrate for a lithium secondary battery, and by employing an inorganic liquid electrolyte based on sulfur dioxide, the wettability of the separator to the electrolyte is greatly improved, and ultimately, the charge/discharge characteristics and cycle of the lithium secondary battery The lifespan is remarkably improved, and in particular, it can be operated stably even at low temperatures, so that it can be applied to energy storage devices such as portable electronic devices or electric vehicles.

1 is a scanning electron microscope (SEM) image of the separator according to Example 1 (PEO coated PE separator), Comparative Example 1 (PE separator), and Comparative Example 2 (Glass fiber filter) of the present invention.
FIG. 2 is a real photograph showing the wettability of the separation membranes according to Example 1 (PEO coated PE), Comparative Example 1 (PE), and Comparative Example 2 (Glass fiber filter) of the present invention.
3 is a graph showing the initial battery characteristics of the lithium secondary batteries prepared in Example 1 and Comparative Examples 1 to 3 of the present invention.
4 is a graph showing the charge/discharge cycle capacity and lifespan characteristics of the lithium secondary batteries prepared in Example 1 and Comparative Examples 1 to 3 of the present invention.
5 is a graph showing the coulombic efficiency in the charge/discharge cycle of the lithium secondary batteries prepared in Example 1 and Comparative Examples 1 to 3 of the present invention.
6 shows the initial discharge capacity of the lithium secondary battery prepared from Example 1 of the present invention and the concentration of the polymer solution for coating according to Example 1 (75 wt%, 50 wt%, 25 wt%, 10 Weight %) A graph comparing the initial discharge capacity of the manufactured lithium secondary battery.
7 is a graph comparing the initial discharge capacity of the lithium secondary batteries prepared in Examples and Comparative Examples 1 of the present invention, and Examples 2 and Comparative Examples 4 to 7 by varying the thickness of the coating layer.
8 is a graph showing initial battery characteristics by driving the lithium secondary batteries prepared in Example 1 and Comparative Example 3 of the present invention at a low temperature.

Hereinafter, a separator for a lithium secondary battery employing a sulfur dioxide-based inorganic liquid electrolyte according to the present invention and a lithium secondary battery including the same will be described in detail with accompanying drawings.

The present invention provides a separator for a lithium secondary battery, wherein a) the lithium secondary battery includes a lithium salt-containing inorganic liquid electrolyte injected with sulfur dioxide; (b) the separator has a coating layer of a polymer material formed on both sides thereof; provides a separator for a lithium secondary battery, characterized in that.

Conventional electrolytes for lithium secondary batteries are mainly lithium salt-containing non-aqueous electrolytes, and are composed of a non-aqueous electrolyte and lithium. As the non-aqueous electrolyte, a non-aqueous electrolyte, an organic solid electrolyte, and an inorganic solid electrolyte are used. Examples of the non-aqueous electrolyte include N-methyl-2-pyrrolidinone, ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, gamma-butyrolactone, dimethylformamide, dimethylacetamide, dimethylsulfoxide or tetrahydrofuran. An aprotic organic solvent is used.

In addition, as an organic solid electrolyte, a polymer containing an ionic dissociation group, such as a polyethylene derivative, a polyethylene oxide derivative, a polypropylene oxide derivative, a phosphoric acid ester polymer, and polyvinyl alcohol, etc. are used.

In addition, lithium nitride, halide, sulfate, etc. are used as an inorganic solid electrolyte.

In particular, a non-aqueous electrolyte in which a lithium salt such as LiCl or LiPF ₆ is added to a mixed solvent of ethylene carbonate or propylene carbonate as a high dielectric solvent and dimethyl carbonate or diethyl carbonate as a low-viscosity solvent as a non-aqueous electrolyte is used in lithium secondary batteries. Although it is mainly employed, the need for the development of a new electrolyte has been constantly raised due to limitations in charge/discharge characteristics and cycle life.

Therefore, in the present invention, the wettability of the separator, which is a core component of a lithium secondary battery, was further improved by employing an inorganic liquid electrolyte containing lithium salt injected with sulfur dioxide as a novel type of electrolyte.

At this time, as the lithium salt, at least one selected from the group consisting of LiAlCl ₄ , LiGaCl ₄ , Li ₂ CoCl ₄ , Li ₂ NiCl ₄ , Li ₂ CuCl ₄ , Li ₂ MnCl ₄ , Li ₂ ZnCl ₄ and LiAlBr ₄ is used. , LiAlCl ₄ -3SO ₂ , in which sulfur dioxide is implanted, is more preferably used as the inorganic liquid electrolyte.

In addition, there are many examples of using a commercially available glass fiber filter as a separator for a lithium secondary battery in the prior art, but the lithium secondary battery to which it is applied has a disadvantage in that the capacity retention rate rapidly drops after several tens of cycles, so in the present invention, to replace it (b ) The separator is a group consisting of polyester, polyamide, polyimide, polycarbonate, polyacetal, polyethersulfone, polyetheretherketone, polyphenylene oxide, and polyphenylenesulfide, including polyolefin-based (polyethylene or polypropylene). One or more porous substrates selected from may be used.

However, since the separators (porous substrates) have a disadvantage in that the wettability to the inorganic liquid electrolyte containing lithium salt injected with sulfur dioxide adopted in the present invention is somewhat inferior, in the present invention, by coating both sides of the separator with a polymer material, sulfur dioxide is injected. It greatly improves the wettability to the inorganic liquid electrolyte containing lithium salt.

As the polymer material, polyethylene oxide, polyvinylpyrrolidone, polyacrylonitrile, polyvinylidene fluoride, polymethylmethacrylate, polyvinylacetate, ethylenevinylacetate copolymer, cellulose acetate, carboxymethylcellulose and polyimide are used. At least one selected from the group consisting of is preferably used, and in particular, polyethylene oxide is more preferably used.

At this time, it is preferable that the coating layer of the polymer material has a thickness of 1 to 10 μm. If the thickness of the coating layer is less than 1 μm, the affinity with the inorganic liquid electrolyte is not good, so wettability may be deteriorated, and the thickness of the coating layer is 10 μm If it is exceeded, the initial discharge capacity may be lowered.

In addition, a typical lithium secondary battery is configured to include a positive electrode, a negative electrode, an electrode assembly consisting of a porous separator disposed between the positive electrode and the negative electrode, and an electrolyte, and in the present invention, the positive electrode, the negative electrode, and disposed between the positive electrode and the negative electrode In a lithium secondary battery comprising an electrode assembly comprising a porous separator, and an electrolyte, the porous separator has a polymer material coating layer formed on both sides, and the electrolyte is a lithium salt-containing inorganic liquid electrolyte injected with sulfur dioxide. A lithium secondary battery is provided.

In this case, since the porous separator (substrate), the polymer material coated on both sides of the porous separator, and the lithium salt-containing inorganic liquid electrolyte in which sulfur dioxide is injected are the same as described above, further descriptions will be omitted.

In addition, the lithium secondary battery according to the present invention ultimately improves the charge/discharge characteristics and cycle life of the lithium secondary battery remarkably, and in particular, it can be stably driven even at low temperatures, so it is suitable for energy storage devices such as portable electronic devices or electric vehicles. Since application is possible, the present invention can provide an energy storage device including the lithium secondary battery.

Hereinafter, specific examples and comparative examples will be described in detail.

(Example 1)

A polymer solution (90% by weight) of polyethylene oxide (PEO) powder dissolved in an acetonitrile solvent was coated on both sides of a commercially available porous polyethylene (PE) separator (thickness 16 μm) by a casting method, and then at 40° C. After drying for 2 hours or more, a PEO-coated PE separator was prepared, and the thickness of the coating layer was adjusted to 6 μm. A battery (2032 coin type) was manufactured using LiAlCl ₄ -3SO ₂ as an inorganic liquid electrolyte containing lithium salt injected with sulfur dioxide, and the working electrode used at this time was graphite and the counter electrode was lithium metal.

( Example 2)

A battery (2032 coin type) was manufactured in the same manner as in Example 1, except that the thickness of the coating layer was adjusted to 2 μm.

(Comparative Example 1)

A battery (2032 coin type) was manufactured in the same manner as in Example 1, except that a porous PE separator not coated with PEO was used.

(Comparative Example 2)

A battery (2032 coin type) was manufactured in the same manner as in Example 1, except that a glass fiber filter not coated with PEO was used as the separator.

(Comparative Example 3)

Example 1 and Example 1 except that 1M LiPF ₆ was added to a mixed organic solvent (1:1, volume ratio) of ethylene carbonate (EC)/dimethyl carbonate (DMC) instead of the inorganic liquid electrolyte of the above embodiment In the same way, a battery (2032 coin type) was manufactured.

(Comparative Examples 4 to 7)

In the same manner as in Example 1, except that the thickness of the coating layer was different [12 μm (Comparative Example 4), 20 μm (Comparative Example 5), 28 μm (Comparative Example 6), 34 μm (Comparative Example 7)]] A battery (2032 coin type) was manufactured.

1 shows a scanning electron microscope (SEM) image of the separators according to Example 1 (PEO coated PE separator), Comparative Example 1 (PE separator), and Comparative Example 2 (Glass fiber filter) of the present invention. It can be confirmed that polyethylene oxide (PEO) was uniformly coated on the porous PE separator according to Example 1 of

In addition, FIG. 2 shows real photographs in which the wettability of the separation membranes according to Example 1 (PEO coated PE), Comparative Example 1 (PE), and Comparative Example 2 (glass fiber filter) of the present invention was observed. As shown in FIG. 2 , both of Example 1 and Comparative Examples 1 and 2 show opaque white surfaces in a state not in contact with the electrolyte. However, as soon as the electrolyte is in contact with the electrolyte, Example 1 and Comparative Example 2 are impregnated with the electrolyte and sink, whereas in Comparative Example 1, it can be confirmed that the electrolyte floats on the electrolyte layer without color change. In addition, when the time elapsed from 1 day, 7 days, and 21 days, Example 1 and Comparative Example 2 reacted with the electrolyte and did not melt or shrink and maintain their shape, whereas in Comparative Example 1, affinity with the electrolyte It can be seen that it is still floating without being impregnated.

In addition, FIG. 3 is a graph showing the initial battery characteristics of the lithium secondary batteries prepared in Example 1 and Comparative Examples ¹ to 3 of the present invention. The initial capacity of the lithium secondary battery employing the liquid electrolyte is 356.7 mAh g ^-1 , 354.2 mAh g ^-1 , 356.9 mAh g ^-1 in Comparative Example 1, Comparative Example 2 and Example 1, respectively, the capacity difference is not large. . The flat voltage that appears as lithium is inserted and detached from the graphite is also well seen, and it can be seen that the deviation between the three batteries is not very large.

However, in the lithium secondary battery of Comparative Example 3 employing the organic liquid electrolyte, the initial capacity is 340.9 mAh g ^-1 , which is much lower than that in the case of employing the inorganic liquid electrolyte. It can be seen that, unlike the case of the inorganic liquid electrolyte, when a typical organic liquid electrolyte is employed, as the flat voltage is not clearly distinguished, the polymer material coating layer acts as a lithium movement resistor, thereby increasing the battery resistance element.

In addition, FIG. 4 is a graph showing the charge/discharge cycle capacity and lifespan characteristics of the lithium secondary batteries prepared in Example 1 and Comparative Examples 1 to 3 of the present invention. In Example 1, since a separator having a thinner thickness and improved electrolyte wettability is used and an inorganic liquid electrolyte based on sulfur dioxide is employed, lithium ion conductivity is increased and internal resistance is lowered, thereby improving lifespan characteristics. After 20 cycles, in the case of Comparative Example 1, it can be seen that the capacity retention rate drops sharply, and it can be seen that the capacity retention rate is the lowest compared to Comparative Examples 2 and 1. It shows that the capacity decreased the most with a capacity of 221.1 mAh g ^-1 based on 47 cycles, with a capacity of 61.9% compared to the first cycle. In the case of Comparative Example 2, it can be seen that after 30 cycles, the capacity retention rate drops sharply, and the capacity retention rate of Comparative Example 2 based on 30 cycles maintains a capacity of 98.9% compared to the first cycle with a capacity of 350.5 mAh g ^-1 and However, it shows that the capacity was significantly reduced to 32.5% of the capacity of the first cycle with a capacity of 115.4 mAh g ^-1 based on 100 cycles. On the other hand, from Example 1, a sulfur dioxide-based inorganic liquid electrolyte was employed to maintain a capacity of 99.8% compared to the first cycle with a capacity of 356.5 mAh g ^-1 in 100 cycles, and at the same time, a polymer material with good wettability to the porous separator substrate It was possible to significantly improve the performance of the battery by coating it. In addition, in the case of the lithium secondary battery prepared in Comparative Example 3, the expressed capacity seems to increase over time, but this is the extent to which the capacity that was not expressed due to the high initial resistance factor is recovered.

In addition, FIG. 5 is a graph showing the coulombic efficiency in the charge/discharge cycle of the lithium secondary batteries prepared in Example 1 and Comparative Examples 1 to 3 of the present invention. In Example 1, the efficiency was 97 to 98.8%. On the other hand, Comparative Example 1 is maintained at a low efficiency of 94.5 to 96%, and Comparative Example 2 shows a gradual decrease to 95%. Therefore, it can be seen that the lithium secondary battery prepared in Example 1 has significantly improved battery performance compared to the lithium secondary battery prepared in Comparative Examples 1 and 2. In addition, in the case of the lithium secondary battery prepared in Comparative Example 3, as confirmed in FIGS. 3 and 4, it is seen that the efficiency is maintained high while the capacity is gradually increased due to the initial low capacity expression.

In addition, FIG. 6 shows the initial discharge capacity of the lithium secondary battery prepared from Example 1 of the present invention and the concentration of the polymer solution for coating according to Example 1 (75% by weight, 50% by weight, 25% by weight) , 10 wt%) A graph comparing the initial discharge capacity of the prepared lithium secondary battery is shown. As shown in FIG. 6 , the lithium secondary battery prepared from Example 1 of the present invention (the concentration of the polymer solution for coating is 90% by weight) and the remaining lithium produced by varying the concentration of the polymer solution for coating Since it can be seen that a similar level of discharge capacity is expressed in the secondary battery, it was confirmed that the concentration of the polymer solution for coating does not become a large variable affecting the initial discharge capacity, but among them, the lithium secondary battery manufactured from Example 1 It can be seen that the initial discharge capacity of

7 is a graph showing the initial discharge capacity of the lithium secondary batteries prepared in Example 1 and Comparative Example 1 of the present invention, and in Examples 2 and 4 to 7 by varying the thickness of the coating layer, in FIG. As can be seen, in the case of the expressed discharge capacity, the average capacity difference is not large, but it can be confirmed that the capacity gradually decreases when the thickness of the coating layer exceeds 10 μm, so the thickness of the coating layer is preferably 1 μm to 10 μm do.

In addition, FIG. 8 shows the initial battery characteristics by driving the lithium secondary batteries prepared in Example 1 and Comparative Example 3 of the present invention at a low temperature in a graph. It can be seen that the expression capacity of the lithium secondary battery prepared in step 3 is lowered. Looking at the results at 10° C. to -10° C. shown in FIG. 8, the lithium secondary battery prepared from Example 1 employing the inorganic liquid electrolyte was 357.6 mAh g ^-1 at a capacity of 362.7 mAh g ^-1 , about 98.6%. While the capacity is maintained, in the lithium secondary battery prepared from Comparative Example 3 employing the organic liquid electrolyte, it can be seen that the capacity of 350.3 mAh g ^-1 to 334.4 mAh g ^-1 is greatly reduced to about 95.4%. Therefore, it can be confirmed that the lithium secondary battery employing the inorganic liquid electrolyte maintains higher ionic conductivity than the lithium secondary battery employing the organic liquid electrolyte even at low temperatures, and thus the capacity expressed by the lithium secondary battery is maintained. It can be seen that, as in Example 1, a lithium secondary battery employing an inorganic liquid electrolyte while using a separator having a coating layer formed of a polymer material can be stably driven even at a low temperature.

Therefore, according to the present invention, a polymer material is coated on a conventional porous separator substrate for a lithium secondary battery, and by employing a sulfur dioxide-based inorganic liquid electrolyte, the wettability of the separator to the electrolyte is greatly improved, and ultimately, the charge/discharge characteristics of the lithium secondary battery and The cycle life is remarkably improved, and in particular, it can be operated stably even at low temperatures, so it can be applied to energy storage devices such as portable electronic devices or electric vehicles.

Claims (8)

In the separator for a lithium secondary battery,
(a) the lithium secondary battery is sulfur dioxide injected LiAlCl ₄ , LiGaCl ₄ , Li ₂ CoCl ₄ , Li ₂ NiCl ₄ , Li ₂ CuCl ₄ , Li ₂ MnCl ₄ , Li ₂ ZnCl ₄ and LiAlBr ₄ selected from the group consisting of at least one lithium salt containing inorganic liquid electrolyte;
(b) on both sides of the separator, polyethylene oxide, polyvinylpyrrolidone, polyacrylonitrile, polyvinylidene fluoride, polymethylmethacrylate, polyvinylacetate, ethylenevinylacetate copolymer, cellulose acetate, carboxymethylcellulose and a coating layer having a thickness of 1 to 10 μm made of one or more polymer materials selected from the group consisting of polyimide; a separator for lithium secondary batteries, characterized in that. delete The separator for a lithium secondary battery according to claim 1, wherein the lithium salt-containing inorganic liquid electrolyte injected with sulfur dioxide is LiAlCl ₄ -3SO ₂ . According to claim 1, (b) The separator is polyethylene, polypropylene, polyester, polyamide, polyimide, polycarbonate, polyacetal, polyether sulfone, polyether ether ketone, polyphenylene oxide, polyphenylene sulfide A separator for a lithium secondary battery, characterized in that it is at least one porous substrate selected from the group consisting of. delete delete In a lithium secondary battery comprising a positive electrode, a negative electrode, an electrode assembly comprising a porous separator disposed between the positive electrode and the negative electrode, and an electrolyte,
The porous separator has polyethylene oxide, polyvinylpyrrolidone, polyacrylonitrile, polyvinylidene fluoride, polymethylmethacrylate, polyvinylacetate, ethylenevinylacetate copolymer, cellulose acetate, carboxymethylcellulose and polyethyl A coating layer having a thickness of 1 to 10 μm is formed of at least one polymer material selected from the group consisting of mide, and the electrolyte is LiAlCl ₄ , LiGaCl ₄ , Li ₂ CoCl ₄ , Li ₂ NiCl ₄ , Li ₂ CuCl ₄ , Li ₂ MnCl ₄ , Li ₂ ZnCl ₄ And LiAlBr ₄ Lithium secondary battery, characterized in that the inorganic liquid electrolyte containing at least one lithium salt selected from the group consisting of. An energy storage device comprising the lithium secondary battery according to claim 7.

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