Polymer solid electrolyte composition for lithium secondary battery and use thereof

Abstract

The present invention is characterized in that the polymer solid electrolyte composition for a lithium secondary battery contains a polymer component, an organic solvent, a lithium salt, and a polymer component having [Chemical Formula 1] WOxNy (in Chemical Formula 1, x and y are each 0.5 to 2.5. ), and the mesoporous tungsten oxynitride nano material is prepared.

Description

Technical Field

[0001] The present invention relates to a polymer solid electrolyte composition for a lithium secondary battery and its use.

[0002] Specifically, the present invention relates to a polymer solid electrolyte composition for a lithium secondary battery, a polymer solid electrolyte for a lithium secondary battery, and a lithium secondary battery. Background Art

[0003] The demand for secondary batteries is increasing in various fields such as PCs, mobile phones, electric vehicles, and energy storage devices. Among secondary batteries, lithium secondary batteries in particular have a higher capacity density than other secondary batteries and operate at high voltages.

[0004] A lithium secondary battery generally consists of an anode (reduction electrode, cathode), a cathode (oxidation electrode, anode), and an electrolyte containing a lithium salt interposed between the anode and the cathode. This electrolyte is either a non-aqueous liquid electrolyte or a solid electrolyte. The non-aqueous liquid electrolyte penetrates into the interior of the anode. Therefore, the non-aqueous liquid electrolyte can easily form an interface between the active material of the anode and the electrolyte, thereby imparting high electrical performance.

[0005] However, since the non-aqueous liquid electrolyte uses a flammable organic solvent, it is prone to catching fire due to overcurrent caused by a short circuit, etc. Therefore, the non-aqueous liquid electrolyte requires a separate safety device, selection of special battery materials, etc., and limits the battery structure design. This is the reason for the increase in the manufacturing cost and the decrease in the productivity of lithium secondary batteries.

[0006] All-solid-state batteries use a solid electrolyte instead of a liquid electrolyte. All-solid-state batteries do not have the disadvantages caused by the use of flammable organic solvents. Therefore, all-solid-state batteries have the advantages of low manufacturing cost and excellent productivity. In addition, all-solid-state batteries have a simple structure. Therefore, the advantages brought by the structure of all-solid-state batteries are excellent stability and high capacity and output.

[0007] The types of solid electrolytes include sulfide solid electrolytes, oxide solid electrolytes, polymer solid electrolytes, etc. Sulfide solid electrolytes and oxide solid electrolytes must be compressed at high temperature and high pressure due to their high interfacial resistance. Polymer solid electrolytes can be manufactured under normal conditions (room temperature and atmospheric pressure), which is advantageous.

[0008] However, the disadvantages of polymer solid electrolytes are insufficient conductivity and mechanical strength. In particular, there is a trade-off relationship between the conductivity and mechanical strength of polymer electrolytes, so it is difficult to improve both properties simultaneously.

[0009] Patent Document 1 describes the addition of mesoporous tungsten oxide. However, the content of Patent Document 1 is not sufficient to simultaneously and sufficiently improve the conductivity and mechanical strength of all-solid-state batteries.

[0010] [Prior Art Documents]

[0011] [Patent Documents]

[0012] (Patent Document 1) JP 5382634 B2 (October 11, 2013) Summary of the Invention

[0013] Technical Problem

[0014] The present invention aims to simultaneously improve the conductivity and mechanical strength of a polymer electrolyte.

[0015] Means for Solving the Problem

[0016] The polymer solid electrolyte composition for a lithium secondary battery of the present invention includes a polymer component, an organic solvent, a lithium salt, and a mesoporous tungsten oxynitride nanomaterial having the composition represented by the following Chemical Formula 1:

[0017] [Chemical Formula 1]

[0018] WO x N y

[0019] In Chemical Formula 1, x and y are each from 0.5 to 2.5.

[0020] In addition, the polymer solid electrolyte for a lithium secondary battery of the present invention includes a polymer component, a lithium salt, and a mesoporous tungsten oxynitride nanomaterial having the composition represented by the following Chemical Formula 1:

[0021] [Chemical Formula 1]

[0022] WO x N y

[0023] In Chemical Formula 1, x and y are each from 0.5 to 2.5.

[0024] In addition, the lithium secondary battery of the present invention includes: a solid electrolyte layer containing the polymer solid electrolyte for a lithium secondary battery; an anode layer disposed on one side of the solid electrolyte layer; and a cathode layer disposed on the other side in a manner opposite to the anode layer with respect to the solid electrolyte layer.

[0025] Advantages of the Invention

[0026] The present invention can simultaneously improve the conductivity and mechanical strength of a polymer electrolyte. Brief Description of the Drawings

[0027] Figure 1 It is a photograph of the polymer solid electrolyte composition of the example.

[0028] Figure 2 It is a photograph of the polymer solid electrolyte of the example.

[0029] Figure 3 It is a photograph of the polymer solid electrolyte of the example. Detailed implementation mode

[0030] Polymer solid electrolyte composition for lithium secondary battery

[0031] The present invention relates to a polymer solid electrolyte composition for a lithium secondary battery.

[0032] The composition of the present invention is a polymer solid electrolyte composition for a "lithium secondary battery", and thus contains a lithium salt.

[0033] The present invention places no restrictions on the type of lithium salt. The lithium salt can be, for example, LiPF6, LiBF4, LiCF3SO3, Li(CF3SO2)2N, Li(CF3SO2)3C, LiC2F5SO3, Li(FSO2)2N, LiC4F9SO3, LiN(SO2CF2CF3)2, LiN(CN)2, etc.

[0034] The present invention places no restrictions on the content of the lithium salt. The above lithium salt can be appropriately added according to the degree to which the above electrolyte exhibits sufficient activity.

[0035] The composition of the present invention is a "polymer" solid electrolyte composition for a lithium secondary battery, and thus contains a polymer component.

[0036] The present invention places no restrictions on the type of polymer component. The above polymer component can be, for example, poly(ethylene oxide) (PEO), poly(vinyl chloride) (PVC), poly(methyl methacrylate) (PMMA), polyacrylonitrile (PAN), poly(vinylidene fluoride) (PVDF), poly(vinylidene fluoride - hexafluoropropylene) (PVDF - HFP), etc.

[0037] The present invention has no limitation on the content of the polymer component. With respect to 100 parts by weight of the above organic solvent, the content of the above polymer component is in the range of 5 parts by weight to 15 parts by weight. The lower limit of the above range (unit: part by weight) is 6, 7, 8, 9 or 10. The upper limit of the above range (unit: part by weight) is 14, 13, 12, 11 or 10.

[0038] The composition of the present invention is a polymer solid electrolyte "composition" for a lithium secondary battery, and thus contains an organic solvent.

[0039] The present invention has no limitation on the type of the organic solvent. The above organic solvent can be, for example, N-methyl-2-pyrrolidone, propylene carbonate, ethylene carbonate, butylene carbonate, dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, γ-butyrolactone, 1,2-dimethoxyethane, 1,2-diethoxyethane, tetrahydroxy franc, 2-methyltetrahydrofuran, dimethyl sulfoxide, 1,3-dioxolane, 4-methyl-1,3-dioxene, diethyl ether, formamide, dimethylformamide, dioxolane, acetonitrile, nitromethane, methyl formate, methyl acetate, triphosphate, trimethoxymethane, dioxolane derivative, sulfolane, methylsulfolane, 1,3-dimethyl-2-imidazolidinone, propylene carbonate derivative, tetrahydrofuran derivative, ether, methyl propionate and ethyl propionate, etc. Preferably, the above organic solvent is ethylene carbonate.

[0040] The composition of the present invention is used to manufacture a polymer solid electrolyte for a lithium secondary battery. Specifically, if the composition of the present invention is dried to volatilize the organic solvent, a polymer solid electrolyte can be obtained.

[0041] As described above, the conductivity and mechanical strength of the polymer electrolyte are insufficient, and it is difficult to improve both properties simultaneously. The composition of the present invention can simultaneously improve the conductivity and mechanical strength of the polymer electrolyte by further containing a specific component in the above components. The composition of the present invention contains a mesoporous tungsten oxynitride nanomaterial. The mesoporous tungsten oxynitride nanomaterial can reduce the crystallinity of the polymer component and improve the conductivity of the polymer electrolyte. In addition, the mesoporous tungsten oxynitride nanomaterial can be effectively dispersed in the electrolyte to improve the material strength of the polymer electrolyte.

[0042] The mesoporous tungsten oxynitride nanomaterial refers to a substance having mesoscopic pores, tungsten oxynitride, and a size in the nanometer unit.

[0043] Mesoporous materials, i.e., mesoporous bodies, refer to materials with pore sizes in the range of 2 nm to 20 nm. The pore sizes of the mesoporous tungsten oxynitride nanomaterials used in the present invention can be within a specific range. For example, the pore sizes of the above-mentioned mesoporous tungsten oxynitride nanomaterials can be within the range of 3 nm to 10 nm.

[0044] The mesoporous tungsten oxynitride nanomaterials used in the present invention are specific tungsten oxynitrides. Specifically, the mesoporous tungsten oxynitride nanomaterials have a specific composition formula. The above-mentioned mesoporous tungsten oxynitride nanomaterials have the composition of the following Chemical Formula 1:

[0045] [Chemical Formula 1]

[0046] WO x N y

[0047] In Chemical Formula 1, x and y are each 0.5 to 2.5. Preferably, the above x and y are each 1.

[0048] The mesoporous tungsten oxynitride nanomaterials used in the present invention can have a specific specific surface area. In a specific example, the specific surface area of the mesoporous tungsten oxynitride nanomaterials can be in the range of 1 m 2 / g to 500 m 2 / g. The lower limit of the above range (unit: m 2 / g) can be 5, 10, 15, 20 or 25. The upper limit of the above range (unit: m 2 / g) can be 400, 300, 200, 100, 90, 80, 70, 60 or 50.

[0049] The present invention can further improve the conductivity and mechanical strength simultaneously by adjusting the content of the mesoporous tungsten oxynitride nanomaterials. In other words, the present invention can improve the conductivity and mechanical strength of the polymer solid electrolyte by applying the mesoporous tungsten oxynitride nanomaterials, and further improve the improvement degree by controlling its content (and / or morphology).

[0050] For example, relative to 100 parts by weight of the above polymer component, the content of the above mesoporous tungsten oxynitride nanomaterials can be in the range of 5 parts by weight to 30 parts by weight. Within this range, the conductivity and mechanical strength of the polymer solid electrolyte can be improved simultaneously to the maximum extent. As will be described later, this range can be further specified according to the morphology of the mesoporous tungsten oxynitride nanomaterials.

[0051] In the present invention, the mesoporous tungsten oxynitride nanomaterials used can mainly have two forms. Specifically, the above-mentioned mesoporous tungsten oxynitride nanomaterials can be at least one of mesoporous tungsten oxynitride nanofibers and mesoporous tungsten oxynitride nanoparticles. That is, the above-mentioned mesoporous tungsten oxynitride nanomaterials can be mesoporous tungsten oxynitride nanofibers, mesoporous tungsten oxynitride nanoparticles, or a mixture of mesoporous tungsten oxynitride nanofibers and mesoporous tungsten oxynitride nanoparticles.

[0052] Mesoporous tungsten oxynitride nanofibers refer to materials in the above-mentioned mesoporous tungsten oxynitride nanomaterials that are in the form of fibers and have a size in the nanometer range. For example, the average size of the above-mentioned mesoporous tungsten oxynitride nanofibers can be in the range of 1 nm to 100 nm. The lower limit of the above size (unit: nm) can be 10, 20, 30, 40, 50, 60, 70, or 80.

[0053] Mesoporous tungsten oxynitride nanoparticles refer to materials in the above-mentioned mesoporous tungsten oxynitride nanomaterials that are in the form of particles and have a size in the nanometer range. For example, the average size of the above-mentioned mesoporous tungsten oxynitride nanoparticles can be in the range of 1 nm to 100 nm.

[0054] As described above, the content can be additionally controlled according to the form of the mesoporous tungsten oxynitride nanomaterials to further improve the conductivity and mechanical strength. Specifically, when the mesoporous tungsten oxynitride nanomaterials are mesoporous tungsten oxynitride nanofibers, the range will also be controlled differently from the above range. At this time, relative to 100 parts by weight of the above polymer component, the content of the mesoporous tungsten oxynitride nanofibers can be in the range of 10 parts by weight to 20 parts by weight. The lower limit of the above range (unit: parts by weight) can be 13, 15, 17, or 19.

[0055] In addition, if the mesoporous tungsten oxynitride nanomaterials are mesoporous tungsten oxynitride nanoparticles, the range will also be controlled differently from the above range. At this time, relative to 100 parts by weight of the above polymer component, the content of the mesoporous tungsten oxynitride nanoparticles can be in the range of 5 parts by weight to 20 parts by weight. The lower limit of the above range (unit: parts by weight) can be 6, 7, 8, 9, or 10. The upper limit of the above range (unit: parts by weight) can be 15, 14, 13, 12, 11, or 10.

[0056] Furthermore, if the mesoporous tungsten oxynitride nanomaterials are a mixture of mesoporous tungsten oxynitride nanofibers and mesoporous tungsten oxynitride nanoparticles, the range will also be controlled differently from the above range. In this case, it is preferable to simultaneously adjust the content of the mixture itself in the composition and the mixing ratio of the nanoparticles and nanofibers in the mixture.

[0057] Among them, relative to 100 parts by weight of the above-mentioned polymer component, the content of the mixture of the above-mentioned mesoporous tungsten oxynitride nanofibers and mesoporous tungsten oxynitride nanoparticles can be in the range of 15 to 25 parts by weight. The lower limit of the above range (unit: part by weight) can be 16, 17, 18, 19 or 20. The upper limit of the above range (unit: part by weight) can be 25, 24, 23, 22, 21 or 20.

[0058] In addition, in the mixture of the above-mentioned mesoporous tungsten oxynitride nanofibers and mesoporous tungsten oxynitride nanoparticles, the weight ratio (NF / NP) of the above-mentioned mesoporous tungsten oxynitride nanofibers (NF) to the above-mentioned mesoporous tungsten oxynitride nanoparticles (NP) can be in the range of 0.7 to 1.5. The lower limit of the above ratio can be 0.8, 0.9 or 1.0. The upper limit of the above ratio can be 1.4, 1.3, 1.2, 1.1 or 1.0.

[0059] The polymer solid electrolyte composition for a lithium secondary battery of the present invention may further contain other known components other than the above components within the range of ensuring the effects of the present invention.

[0060] Polymer solid electrolyte for lithium secondary battery

[0061] The present invention is a polymer solid electrolyte for a lithium secondary battery. In the present invention, the solvent is removed from the polymer solid electrolyte composition for a lithium secondary battery. Therefore, the electrolyte of the present invention includes: a polymer component; a lithium salt; and a mesoporous tungsten oxynitride nanomaterial having the composition of Chemical Formula 1. In addition, the content mentioned in the composition of the present invention also applies to this electrolyte. Therefore, if the constitution mentioned when describing the composition of the present invention also exists in the electrolyte of the present invention, the same content can be applied.

[0062] The electrolyte of the present invention can be manufactured from the composition of the present invention. For example, the electrolyte of the present invention can be manufactured by drying the above composition.

[0063] The polymer solid electrolyte for a lithium secondary battery of the present invention may further contain other known components other than the above components within the range of ensuring the effects of the present invention.

[0064] Lithium secondary battery

[0065] The present invention is a lithium secondary battery. Specifically, the present invention is an all-solid-state lithium secondary battery. More specifically, the present invention is a lithium secondary battery including the above polymer solid electrolyte.

[0066] The lithium secondary battery of the present invention uses the polymer solid electrolyte of the present invention as the electrolyte in a lithium secondary battery with a known structure. Therefore, the lithium secondary battery of the present invention includes: a solid electrolyte layer containing a polymer solid electrolyte for a lithium secondary battery; an anode layer disposed on one side surface of the solid electrolyte layer; and a cathode layer disposed on the other side surface in a manner opposite to the anode layer with respect to the solid electrolyte layer.

[0067] The lithium secondary battery of the present invention may further include other known components other than the above-described components within the scope of ensuring the effects of the present invention.

[0068] Hereinafter, the present invention will be described in more detail using examples. However, the following examples do not limit the scope of protection of the present invention.

[0069] [Example 1]

[0070] 1. Materials

[0071] (1) As the polymer component, PAN (Aldrich) is used.

[0072] (2) As the lithium salt, LiPF6 (Aldrich) is used.

[0073] (3) As the organic solvent, ethyl carbonate is used.

[0074] (4) Preparation of mesoporous tungsten oxynitride nanomaterials is as follows.

[0075] 1) Commercially available mesoporous tungsten oxide (Aldrich) is obtained and heat-treated with ammonia gas to prepare mesoporous tungsten oxynitride particles.

[0076] 2) Commercially available mesoporous tungsten oxide (Aldrich) is obtained, electrospun into a fibrous form and heat-treated, and then heat-treated with ammonia gas to prepare mesoporous tungsten oxynitride fibers.

[0077] 3) The composition of the mesoporous tungsten oxynitride nanomaterials is analyzed by EDS and XPS. TEM-EDS is performed using an HR-TEM, FEI Talos F200X device. At this time, the sample is applied by being dispersed in ethanol. XPS is performed using a thermo VG Scientific K-Alpha. In XPS, the sample is not pretreated separately.

[0078] The characteristics of the mesoporous tungsten oxynitride nanoparticles and mesoporous tungsten oxynitride nanofibers used in the present invention are summarized in Table 1 below. Among them, the pore size and specific surface area of the nanoparticles and nanofibers are measured by BET analysis. BET is performed using a Micromeritics 3Flex device. At this time, the sample is applied after being dried and pretreated at 100 °C.

[0079] [Table 1]

[0080]

[0081]

[0082] 2. Evaluation

[0083] (1) Ionic conductivity

[0084] The polymer solid electrolytes of the examples and comparative examples were placed between 20 mm diameter ionic conductivity measurement cells with SUS plates on the upper and lower surfaces and bonded to produce test pieces. The impedance of the test piece was measured to obtain the resistance value. The obtained resistance value was substituted into the formula "Ionic conductivity = Thickness / (Area * Resistance)", thereby measuring the ionic conductivity of the polymer solid electrolyte.

[0085] (2) Tensile strength

[0086] The polymer solid electrolytes of the examples and comparative examples were cut into transverse * longitudinal (1 cm * 5 cm) to produce test pieces. For the test pieces, the tensile strength was measured using a tensile strength tester (Instron UTM machine) according to the ASTM D638 standard.

[0087] (3) Discharge capacity retention measurement

[0088] Button cells were fabricated using the polymer solid electrolytes of the examples and comparative examples. Specifically, the anode of the button cell was an NCM811 electrode and the cathode was a lithium metal electrode. Using a button cell charger / discharger (product of Warnatech), the polymer electrolyte thus fabricated was cyclically charged and discharged at 0.3C, and the discharge capacity that decreased with the increase in the number of charge and discharge cycles was measured. Then, the measured discharge capacity was converted into a % ratio based on the initial discharge capacity.

[0089] 3. Manufacturing

[0090] (1) Polymer solid electrolyte composition

[0091] In a container filled with an organic solvent, 10 parts by weight of a polymer component was dissolved with respect to 100 parts by weight of the solvent. After the polymer component was completely dissolved, 6 parts by weight of a lithium salt was further dissolved in the container based on 100 parts by weight of the solution. In the container in which the polymer component and lithium were dissolved, 5 parts by weight of nanoparticles were added with respect to 100 parts by weight of the polymer component. It was dispersed using a ball mill for 3 minutes to obtain a polymer solid electrolyte composition. Figure 1 This is a photograph of the polymer solid electrolyte composition thus manufactured.

[0092] (2) Polymer solid electrolyte

[0093] The polymer solid electrolyte composition was doctor - blade coated on a glass plate with a thickness of 50 μm. After coating, it was dried in a vacuum oven at 95 °C for 1 hour to obtain the polymer solid electrolyte. Figure 2 and Figure 3 is a photograph of the polymer solid electrolyte of the example.

[0094] [Examples 2 to 9 and Comparative Examples]

[0095] The composition of the polymer solid electrolyte composition was changed to the compositions described in Tables 2 and 3, and other than that, the same process as in Example 1 was repeated.

[0096] 4. Results

[0097] Tables 2 and 3 show the compositions and evaluation results of the examples and comparative examples.

[0098] [Table 2]

[0099]

[0100] [Table 3]

[0101]

[0102] The conductivity (ionic conductivity) and mechanical strength (tensile strength) of the polymer solid electrolyte made from the composition defined in the present invention are significantly superior to those made from the composition not defined in the present invention.

Claims

1. A polymer solid electrolyte composition for a lithium secondary battery, comprising: a polymer component; an organic solvent; a lithium salt; and a mesoporous tungsten oxynitride nanomaterial having a composition represented by Chemical Formula 1 below, [Chemical Formula 1] WO x N y In Chemical Formula 1, x and y are each from 0.5 to 2.

5.

2. The polymer solid electrolyte composition for a lithium secondary battery according to Claim 1, wherein the pore size of the mesoporous tungsten oxynitride nanomaterial is in the range of 3 nm to 10 nm.

3. The polymer solid electrolyte composition for a lithium secondary battery according to Claim 1, wherein the content of the mesoporous tungsten oxynitride nanomaterial is in the range of 5 parts by weight to 30 parts by weight with respect to 100 parts by weight of the polymer component.

4. The polymer solid electrolyte composition for a lithium secondary battery according to Claim 1, wherein the mesoporous tungsten oxynitride nanomaterial is at least one of mesoporous tungsten oxynitride nanofibers and mesoporous tungsten oxynitride nanoparticles.

5. The polymer solid electrolyte composition for a lithium secondary battery according to Claim 4, wherein the mesoporous tungsten oxynitride nanomaterial is mesoporous tungsten oxynitride nanofibers, and the content of the mesoporous tungsten oxynitride nanofibers is in the range of 10 parts by weight to 20 parts by weight with respect to 100 parts by weight of the polymer component.

6. The polymer solid electrolyte composition for a lithium secondary battery according to Claim 4, wherein the mesoporous tungsten oxynitride nanomaterial is a mixture of mesoporous tungsten oxynitride nanofibers and mesoporous tungsten oxynitride nanoparticles, the content of the mixture of the mesoporous tungsten oxynitride nanofibers and the mesoporous tungsten oxynitride nanoparticles is in the range of 15 parts by weight to 25 parts by weight with respect to 100 parts by weight of the polymer component, and in the mixture of the mesoporous tungsten oxynitride nanofibers and the mesoporous tungsten oxynitride nanoparticles, the weight ratio of the mesoporous tungsten oxynitride nanofibers NF to the mesoporous tungsten oxynitride nanoparticles NP, i.e., NF / NP, is in the range of 0.7 to 1.

5.

7. A polymer solid electrolyte for a lithium secondary battery, comprising: a polymer component; a lithium salt; and a mesoporous tungsten oxynitride nanomaterial having a composition represented by Chemical Formula 1 below, [Chemical Formula 1] WO x N y In Chemical Formula 1, x and y are each from 0.5 to 2.

5.

8. A lithium secondary battery, comprising: a solid electrolyte layer containing the polymer solid electrolyte for a lithium secondary battery according to Claim 7; an anode layer disposed on one side of the solid electrolyte layer; and a cathode layer disposed on the other side in a manner opposite to the anode layer with respect to the solid electrolyte layer.

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