Polymer electrolyte membrane for lithium secondary battery and lithium secondary battery comprising same

Abstract

The polymer electrolyte membrane for a lithium secondary battery according to the present invention comprises a copolymer. The copolymer has: a main chain comprising a first repeating unit and a second repeating unit; a fluoroalkyl group which is bonded to the main chain by a side chain; and a polymer segment that is bonded to the main chain in a side chain and contains oxygen. The lithium secondary battery according to the present invention comprises the polymer electrolyte membrane for a lithium secondary battery.

Description

Technical Field

[0001] The present invention provides a polymer electrolyte membrane for lithium secondary batteries and a lithium secondary battery including the same. Background Technology

[0002] Rechargeable batteries are batteries that can be repeatedly charged and discharged. With the development of the information communication and display industries, rechargeable batteries are widely used as power sources for portable electronic communication devices such as portable cameras, mobile phones, and laptops (PCs). In addition, in recent years, battery packs that include rechargeable batteries have been developed for use as power sources for environmentally friendly vehicles such as electric vehicles.

[0003] Lithium-ion batteries, a type of secondary battery, have high operating voltage and energy density per unit weight, and are advantageous for charging speed and lightweight design, so they are being actively researched and developed.

[0004] In recent years, research and development have focused on lithium-ion rechargeable batteries with high energy density and fast charging characteristics. However, during repeated charging and discharging, heat can accumulate inside the battery, potentially causing a fire.

[0005] Using solid or semi-solid electrolytes can improve battery fire stability. Compared to liquid electrolytes, solid or semi-solid electrolytes may have lower fluidity and less thermal deformation, thus improving battery stability.

[0006] However, to achieve higher capacity and larger size of batteries, structural modifications, treatments, and improvements in the physical properties of the electrolyte layer may be necessary to improve the lifespan and stability of lithium batteries. Summary of the Invention

[0007] (a) Technical problems to be solved

[0008] One technical problem of the present invention is to provide a polymer electrolyte membrane for lithium secondary batteries with improved electrochemical properties.

[0009] One technical problem of the present invention is to provide a lithium secondary battery including the polymer electrolyte membrane for the lithium secondary battery.

[0010] (II) Technical Solution

[0011] The polymer electrolyte membrane for lithium secondary batteries according to the present invention comprises a copolymer. The copolymer has: a main chain comprising a first repeating unit represented by the following chemical formula 1 and a second repeating unit represented by the following chemical formula 2; a fluoroalkyl group bonded to the main chain by a side chain; and polymer segments bonded to the main chain by a side chain and comprising oxygen.

[0012] [Chemical Formula 1]

[0013]

[0014] [Chemical Formula 2]

[0015]

[0016] In chemical formulas 1 to 2, R1 and R2 are each independently hydrogen or an alkyl group having 1 to 10 carbon atoms, and R3 to R5 can each be independently hydrogen, an alkyl group having 1 to 60 carbon atoms, an alkenyl group having 2 to 60 carbon atoms, an alkynyl group having 2 to 60 carbon atoms, or an arylthio group having 6 to 60 carbon atoms. For example, R3 and R4 can be hydrogen or an alkyl group having 1 to 5 carbon atoms. n, m, and p are each independently 0 or an integer from 1 to 4. q is an integer from 2 to 4. This is the bond point.

[0017] In an exemplary embodiment, the chemical formula 1 may be represented by the following chemical formula 1-1.

[0018] [Chemical Formula 1-1]

[0019]

[0020] In an exemplary embodiment, chemical formula 2 may be represented by chemical formula 2-1 or chemical formula 2-2.

[0021] [Chemical Formula 2-1]

[0022]

[0023] [Chemical Formula 2-2]

[0024]

[0025] In an exemplary embodiment, the ratio of the number of the second repeating units to the number of the first repeating units can be from 0.1 to 10.

[0026] In an exemplary embodiment, the fluoroalkyl group may have a structure in which at least one of the hydrogen atoms of an alkyl group having 1 to 10 carbon atoms is substituted with fluorine.

[0027] In an exemplary embodiment, the fluoroalkyl group may include at least one selected from trifluoromethyl, pentafluoroethyl, trifluoroethyl, and heptafluoropropyl.

[0028] In an exemplary embodiment, the fluoroalkyl group can be directly bonded to the main chain.

[0029] In an exemplary embodiment, the polymer segment may include a polyether segment or a poly(meth)acrylate segment.

[0030] In an exemplary embodiment, the polyether segment may be represented by the following chemical formula 3.

[0031] [Chemical Formula 3]

[0032]

[0033] In the aforementioned chemical formula 3, L can be a direct bond or an alkylene group having 1 to 10 carbon atoms, R6 can be an alkyl group having 1 to 10 carbon atoms, R7 can be an alkylene group having 1 to 10 carbon atoms, and r can be an integer from 5 to 20. It can be a bonding point with the main chain.

[0034] In an exemplary embodiment, the main chain may include a third repeating unit represented by the following chemical formula 4.

[0035] [Chemical Formula 4]

[0036]

[0037] In the chemical formula 4, R f R6 can be a fluoroalkyl group with 1 to 10 carbon atoms, R7 can be an alkylene group with 1 to 10 carbon atoms, and r can be an integer from 5 to 20. It can be a bond point.

[0038] In an exemplary embodiment, the weight-average molecular weight of the copolymer can be from 10 kg / mol to 400 kg / mol.

[0039] In an exemplary embodiment, the polymer electrolyte membrane for lithium secondary batteries may have a thickness of 20 μm to 100 μm.

[0040] In an exemplary embodiment, the polymer electrolyte membrane for the lithium secondary battery may have a density of 0.2. 10 -6 S / cm to 100 10 -6 Ionic conductivity in S / cm.

[0041] In an exemplary embodiment, the polymer electrolyte membrane for lithium secondary batteries may contain a lithium salt. The lithium salt content in the total weight of the polymer electrolyte membrane for lithium secondary batteries may be from 50% to 90% by weight.

[0042] The lithium secondary battery according to the present invention includes: a positive electrode; a negative electrode disposed opposite to the positive electrode; and a polymer electrolyte membrane for the lithium secondary battery disposed between the positive electrode and the negative electrode.

[0043] (III) Beneficial Effects

[0044] The polymer electrolyte membrane for lithium secondary batteries according to an exemplary embodiment of the present invention may contain copolymers having a high molecular weight. Therefore, the durability of the polymer electrolyte membrane for lithium secondary batteries can be improved.

[0045] The copolymer of the polymer electrolyte membrane for lithium secondary batteries may contain oxygen-containing polymer segments that can interact with lithium ions. Therefore, the ionic conductivity and electrochemical stability of lithium ions in the polymer electrolyte membrane for lithium secondary batteries can be improved, and the degree of dissociation of lithium salts in the polymer electrolyte membrane for lithium secondary batteries can be increased.

[0046] The copolymer of the polymer electrolyte membrane for lithium secondary batteries can contain polymer segments as side chains. Therefore, it can have high bending and rotational autonomy of the copolymer chains and reduced crystallinity, thereby further improving the ionic conductivity of the polymer electrolyte membrane for lithium secondary batteries.

[0047] The lithium secondary battery according to an exemplary embodiment of the present invention can have improved rate performance. Attached Figure Description

[0048] Figure 1 and Figure 2 The proton nuclear magnetic resonance spectra of the copolymers of Synthesis Example 2 and Synthesis Example 1 are respectively. 1 ¹H-NMR results.

[0049] Figure 3 The results are Fourier transform infrared (FT-IR) spectroscopic analysis results of the copolymers of Synthetic Example 1 and Synthetic Example 2.

[0050] Figure 4 The results are DSC analysis of the copolymers from Synthesis Example 1 and Synthesis Example 2.

[0051] Figure 5 These are the strain-stress curves of the copolymers of Synthetic Example 1 and Synthetic Example 2.

[0052] Figure 6 These are the TGA analysis results of the polymer electrolyte membranes from Examples 1 to 4.

[0053] Figure 7These are the electrochemical impedance spectroscopy (EIS) results of the polymer electrolyte membranes of Examples 1 to 4. Detailed Implementation

[0054] This invention provides a polymer electrolyte membrane for lithium secondary batteries comprising a copolymer having oxygen-containing polymer segments bonded to the main chain by side chains. Furthermore, this invention provides a lithium secondary battery comprising the aforementioned polymer electrolyte membrane.

[0055] The present invention will now be described in detail. However, this is merely exemplary, and the present invention is not limited to the specific embodiments described herein.

[0056] According to an exemplary embodiment, a polymer electrolyte membrane for lithium secondary batteries (hereinafter, may be simply referred to as polymer electrolyte membrane) comprises a copolymer having a main chain comprising a first repeating unit and a second repeating unit.

[0057] The first repeating unit is represented by the following chemical formula 1.

[0058] [Chemical Formula 1]

[0059]

[0060] In the chemical formula 1, R1 and R2 are each independently hydrogen or an alkyl group having 1 to 10 carbon atoms. In some embodiments, R1 and R2 may each be independently hydrogen or an alkyl group having 1 to 3 carbon atoms. For example, R1 and R2 may each be methyl.

[0061] The first repeating unit may contain a fluorene moiety. Therefore, the free volume between copolymer chains can be increased, and the rate of increase in copolymer crystallinity can be reduced. Thus, high molecular weight copolymers can be achieved, thereby improving the durability of the polymer electrolyte membrane.

[0062] In Formula 1, R3 and R4 can each be hydrogen, an alkyl group having 1 to 60 carbon atoms, an alkenyl group having 2 to 60 carbon atoms, an alkynyl group having 2 to 60 carbon atoms, or an arylthio group having 6 to 60 carbon atoms. For example, R3 and R4 can be hydrogen or an alkyl group having 1 to 5 carbon atoms.

[0063] In the chemical formula 1, n and m are each independently 0 or an integer from 1 to 4. For example, n and m can each be independently 0 or 1.

[0064] In the chemical formula 1, This is a bonding point. Repeating units of chemical formula 2 or chemical formula 3, etc., can be bonded to this bonding point.

[0065] According to an exemplary embodiment, the chemical formula 1 can be represented by the following chemical formula 1-1.

[0066] [Chemical Formula 1-1]

[0067]

[0068] The second repeating unit is represented by the following chemical formula 2.

[0069] [Chemical Formula 2]

[0070]

[0071] In the chemical formula 2, R5 can be hydrogen, an alkyl group having 1 to 60 carbon atoms, an alkenyl group having 2 to 60 carbon atoms, an alkynyl group having 2 to 60 carbon atoms, or an arylthio group having 6 to 60 carbon atoms. For example, R5 can be hydrogen or an alkyl group having 1 to 5 carbon atoms.

[0072] In the chemical formula 2, p is 0 or an integer from 1 to 4. For example, p can be 0 or 1.

[0073] In the chemical formula 2, q is an integer from 2 to 4. For example, q can be 2 or 3.

[0074] In the chemical formula 2, This is a bonding point. Repeating units of chemical formula 1 or the following chemical formula 3, etc., can be bonded at this bonding point.

[0075] According to an exemplary embodiment, the chemical formula 2 may be represented by the following chemical formula 2-1 or chemical formula 2-2.

[0076] [Chemical Formula 2-1]

[0077]

[0078] [Chemical Formula 2-2]

[0079]

[0080] The second repeating unit may include a biphenyl moiety or a terphenyl moiety. Therefore, the copolymer chains can rotate, thereby improving the formability of the polymer electrolyte membrane.

[0081] According to an exemplary embodiment, the ratio of the number of the second repeating units to the number of the first repeating units can be from 0.1 to 10. According to some embodiments, the ratio of the number of the second repeating units to the number of the first repeating units can be from 1 to 10 or from 4 to 9.

[0082] Within the aforementioned range, the polymer electrolyte membrane can be formed into a film, and its durability can be improved.

[0083] The copolymer according to an exemplary embodiment has fluoroalkyl groups and polymer segments bonded as side chains to the main chain. The polymer segments contain oxygen and are bonded as side chains to the main chain, thereby promoting the dissociation of lithium salts contained in the polymer electrolyte membrane. Furthermore, the oxygen-containing polymer segments can actively interact with lithium ions, thus improving the ionic conductivity and electrochemical stability of the polymer electrolyte membrane.

[0084] According to an exemplary embodiment, the fluoroalkyl group may have a structure in which at least one of the hydrogen atoms of an alkyl group having 1 to 10 carbon atoms is substituted with fluorine. For example, the fluoroalkyl group may have a structure in which one or more or all of the hydrogen atoms of an alkyl group having 1 to 10 carbon atoms are substituted with fluorine.

[0085] For example, the fluoroalkyl group may include trifluoromethyl, pentafluoroethyl, trifluoroethyl, heptafluoropropyl, etc. For example, the fluoroalkyl group may include trifluoromethyl.

[0086] According to an exemplary embodiment, the fluoroalkyl group can be directly bonded to the main chain. For example, the carbon atom of the fluoroalkyl group can be directly bonded to the carbon atom of the main chain.

[0087] According to an exemplary embodiment, the polymer segment can be bonded to the main chain via a linking group. The "linking group" can be a divalent organic group, which has one end bonded to the polymer segment and the other end bonded to the main chain, thereby bonding the polymer segment to the main chain.

[0088] According to an exemplary embodiment, the polymer segment may comprise a polyether segment or a poly(meth)acrylate segment. The polymer segment, by containing at least one oxygen atom, can exhibit high polarity and can increase the degree of dissociation of the lithium salt.

[0089] According to an exemplary embodiment, the polyether segment can be represented by the following chemical formula 3.

[0090] [Chemical Formula 3]

[0091]

[0092] In the chemical formula 3, L can be a direct bond or an alkylene group having 1 to 10 carbon atoms. In some embodiments, L can be an alkylene group having 2 to 5 carbon atoms; for example, L can be propylidene.

[0093] In the chemical formula 3, R6 can be an alkyl group having 1 to 10 carbon atoms. In some embodiments, R6 can be an alkyl group having 1 to 5 carbon atoms. For example, R6 can be a methyl group.

[0094] In the chemical formula 3, R7 can be an alkylene group having 1 to 10 carbon atoms. In some embodiments, R7 can be an alkylene group having 1 to 5 carbon atoms; for example, R7 can be an ethylene group.

[0095] In the chemical formula 3, r can be an integer from 5 to 20. In some embodiments, r can be an integer from 5 to 10.

[0096] In the chemical formula 3, It can be a bonding point with the main chain.

[0097] According to an exemplary embodiment, the fluoroalkyl group and the polymer segment may be bonded to a single carbon atom. According to some embodiments, the main chain may contain a third repeating unit represented by the following chemical formula 4.

[0098] [Chemical Formula 4]

[0099]

[0100] In the chemical formula 4, R f It can be a fluoroalkyl group having 1 to 10 carbon atoms. The fluoroalkyl group can be the same as described above.

[0101] In the chemical formula 4, L, R6, R7 and r can be the same as those described in chemical formula 3.

[0102] In the chemical formula 4, These can be bonding points. Repeating units of chemical formula 1 or chemical formula 2, etc., can be bonded to these bonding points.

[0103] According to an exemplary embodiment, the third repeating unit may be disposed between the first repeating units, between the second repeating units, and / or between the first repeating units and the second repeating units. For example, the third repeating unit may be disposed between the first repeating units and / or the second repeating units.

[0104] According to an exemplary embodiment, the content of the first repeating unit in the total number of moles of the first repeating unit, the second repeating unit, and the third repeating unit can be from 3 mol% to 20 mol%. According to some embodiments, the content of the first repeating unit in the total number of moles of the first repeating unit, the second repeating unit, and the third repeating unit can be from 4 mol% to 10 mol.

[0105] According to an exemplary embodiment, the content of the second repeating unit in the total number of moles of the first repeating unit, the second repeating unit, and the third repeating unit can be from 30 mol% to 50 mol%. According to some embodiments, the content of the second repeating unit in the total number of moles of the first repeating unit, the second repeating unit, and the third repeating unit can be from 35 mol% to 45 mol%.

[0106] According to an exemplary embodiment, the content of the third repeating unit in the total number of moles of the first repeating unit, the second repeating unit, and the third repeating unit can be from 30 mol% to 70 mol%. According to some embodiments, the content of the third repeating unit in the total number of moles of the first repeating unit, the second repeating unit, and the third repeating unit can be from 40 mol% to 60 mol% or from 45 mol% to 55 mol.

[0107] Within the aforementioned range, both the durability and flexibility of the polymer electrolyte membrane can be improved simultaneously.

[0108] According to an exemplary embodiment, the weight-average molecular weight of the copolymer can be from 10 kg / mol to 400 kg / mol. According to some embodiments, the weight-average molecular weight of the copolymer can be from 20 kg / mol to 400 kg / mol. Within the above range, the mechanophysical properties of the polymer electrolyte membrane can be further improved.

[0109] According to an exemplary embodiment, the thickness of the polymer electrolyte membrane can be from 20 μm to 100 μm. According to some embodiments, the thickness of the polymer electrolyte membrane can be from 25 μm to 70 μm.

[0110] According to an exemplary embodiment, the ionic conductivity of the polymer electrolyte membrane can be 0.2. 10 -6 S / cm to 100 10 -6 S / cm. According to some embodiments, the ionic conductivity of the polymer electrolyte membrane can be 0.5 × 10⁻⁶. - 6 S / cm up to 5×10 -6 S / cm. Within the above range, the rate characteristics of lithium secondary batteries including the polymer electrolyte membrane can be improved.

[0111] The copolymer can be prepared by introducing polymer segments into a prepolymer prepared from a monomer mixture comprising fluorenyl monomers, polyphenyl monomers and fluoroalkyl ketone monomers.

[0112] The fluorene monomer can be represented by the following chemical formula 5.

[0113] [Chemical Formula 5]

[0114]

[0115] The fluorene monomer can be a dialkylfluorene, which can be represented by the following chemical formula 5-1.

[0116] [Chemical Formula 5-1]

[0117]

[0118] In chemical formula 5 and chemical formula 5-1, R1 to R4, n and m can be the same as those described in chemical formula 1.

[0119] For example, the fluorene monomer can be dimethylfluorene.

[0120] The polyphenyl monomer can be represented by the following chemical formula 6.

[0121] [Chemical Formula 6]

[0122]

[0123] In the chemical formula 6, q' can be 1 or 2, p' can be 0 or an integer from 1 to 4, R5 can be the same as that described in chemical formula 2, and s can be 0 or an integer from 1 to 4.

[0124] The polyphenyl monomer can be represented by the following chemical formula 6-1 or chemical formula 6-2.

[0125] [Chemical Formula 6-1]

[0126]

[0127] [Chemical Formula 6-2]

[0128]

[0129] For example, the polyphenyl monomer can be biphenyl.

[0130] The fluoroalkyl ketone monomer can be represented by the following chemical formula 7.

[0131] [Chemical Formula 7]

[0132]

[0133] In the chemical formula 7, R f L can be the same as that described in chemical formula 4, and X can be a halogen. For example, X can be Cl, F, Br, etc.

[0134] According to an exemplary embodiment, the content of the fluorenyl monomer in the total molar number of the fluorenyl monomer, polyphenyl monomer, and fluoroalkyl ketone monomer can be from 3 mol% to 20 mol%. According to some embodiments, the content of the fluorenyl monomer in the total molar number of the fluorenyl monomer, polyphenyl monomer, and fluoroalkyl ketone monomer can be from 4 mol% to 10 mol.

[0135] According to an exemplary embodiment, the content of the polyphenyl monomer in the total molar number of the fluorenyl monomer, polyphenyl monomer, and fluoroalkyl ketone monomer can be from 30 mol% to 50 mol%. According to some embodiments, the content of the polyphenyl monomer in the total molar number of the fluorenyl monomer, polyphenyl monomer, and fluoroalkyl ketone monomer can be from 35 mol% to 45 mol%.

[0136] According to an exemplary embodiment, the content of the fluoroalkyl ketone monomer in the total molar number of the fluorenyl monomer, polyphenyl monomer, and fluoroalkyl ketone monomer can be from 30 mol% to 70 mol%. According to some embodiments, the content of the polyphenyl monomer in the total molar number of the fluorenyl monomer, polyphenyl monomer, and fluoroalkyl ketone monomer can be from 40 mol% to 60 mol% or from 45 mol% to 55 mol%.

[0137] The monomer mixture may further contain a solvent. The solvent content may be from 10 to 40 parts by weight relative to 100 parts by weight of the total weight of the fluorenyl monomer, polyphenyl monomer, and fluoroalkyl ketone monomer.

[0138] For example, the solvent may contain dichloromethane.

[0139] The monomer mixture can be reacted in the presence of a catalyst to form a prepolymer. The catalyst is not particularly limited, but acidic catalysts such as trifluoromethanesulfonic acid can be used.

[0140] The monomer mixture can be stabilized at a relatively low temperature before reacting.

[0141] For example, the monomer mixture can be stabilized by placing it at a temperature of 0°C to 15°C for about 10 to 60 minutes. After stabilization, the monomer mixture is placed at 20°C to 40°C for about 3 to 5 hours to form a prepolymer.

[0142] The dispersion containing the prepolymer, unreacted monomer, and solvent can be precipitated and dried to obtain the prepolymer.

[0143] The copolymer can be prepared by introducing oxygen-containing polymer segments into the prepolymer. The copolymer can also be prepared by reacting the prepolymer with an oxygen-containing polymer.

[0144] For example, the oxygen-containing polymer can be polyether, poly(meth)acrylate, etc.

[0145] The oxygen-containing polymer can be used in excess compared to the prepolymer. For example, the weight ratio of the oxygen-containing polymer to the prepolymer can be 2 to 5.

[0146] The prepolymer and the oxygen-containing polymer can react in the presence of a catalyst. The catalyst is not particularly limited, but an alkaline catalyst, such as sodium hydroxide, can be used.

[0147] The reaction solution containing the prepolymer and the oxygen-containing polymer may further contain a solvent. The solvent content may be from 10 to 40 parts by weight relative to 100 parts by weight of the total weight of the prepolymer and the oxygen-containing polymer.

[0148] The solvent may contain, for example, dimethylacetamide.

[0149] The reaction solution can be stabilized at a relatively low temperature before the reaction can proceed.

[0150] For example, the reaction solution can be stabilized by placing it at about 60°C to 90°C for 30 to 90 minutes. After stabilization, the reaction solution can be placed at about 100°C to 150°C for 2 to 5 hours to form the copolymer.

[0151] The copolymer can be obtained by precipitating and drying the dispersion containing the copolymer, unreacted reactants and the solvent.

[0152] The preparation method of the copolymer is exemplary, and its preparation method is not particularly limited as long as a copolymer with the above structure can be formed.

[0153] According to an exemplary embodiment, the polymer electrolyte membrane may further comprise a lithium salt. The lithium salt is a component that directly participates in the current movement of the lithium secondary battery and may comprise lithium cations and organic / inorganic anions.

[0154] According to an exemplary embodiment, the lithium salt content in the total weight of the polymer electrolyte membrane can be from 50% to 90% by weight. According to some embodiments, the lithium salt content in the total weight of the polymer electrolyte membrane can be from 50% to 80% by weight or from 60% to 70% by weight.

[0155] Within the aforementioned range, the lithium-ion conductivity of the polymer electrolyte membrane can be further improved. Furthermore, the rate performance of the lithium secondary battery including the polymer electrolyte membrane can be further improved.

[0156] The lithium salt is not particularly limited, but can be Li + X - Indicated. The anion (X) of the lithium salt is... - ), can be listed as 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 (CF3CF2SO2)2N - wait.

[0157] For example, the lithium salt can be Li(FSO2)2N, i.e., lithium bis(fluorosulfonyl)imide (LiFSI).

[0158] According to an exemplary embodiment, the polymer electrolyte membrane may further include electrolyte additives, inorganic solid electrolytes, organic solid electrolytes, etc.

[0159] For example, the electrolyte additive may include unsaturated carbonate compounds, fluorinated carbonate compounds, sulcinolone compounds, cyclic sulfate compounds, cyclic sulfite compounds, phosphate compounds, borate compounds, etc.

[0160] The unsaturated carbonate-based compounds may include vinylene carbonate (VC), vinyl ethylene carbonate (VEC), etc.

[0161] The fluorinated carbonate compounds may include fluoroethylene carbonate (FEC), etc.

[0162] The sulfonyl compounds may include 1,3-propane sultone, 1,3-propene sultone, 1,4-butane sultone, etc.

[0163] The cyclic sulfate-based compounds may include 1,2-ethylene sulfate, 1,2-propylene sulfate, etc.

[0164] The cyclic sulfite-based compounds may include ethylene sulfite, butylene sulfite, etc.

[0165] The phosphate-based compounds may include lithium difluorobis-oxalato phosphate, lithium difluorophosphate, etc.

[0166] The borate-based compounds may include lithium bis(oxalate) borate, etc.

[0167] The inorganic solid electrolyte may include sulfide-based solid electrolyte or oxide-based solid electrolyte.

[0168] The sulfide-based solid electrolyte may include Li2S-P2S5, Li2S-P2S5-LiCl, Li2S-P2S5-LiBr, Li2S-P2S5-LiCl-LiBr, Li2S-P2S5-Li2O, Li2S-P2S5-Li2O-LiI, Li2S-SiS2, Li2S-SiS2-LiI, Li2S-SiS2-LiBr, Li2S-SiS2-LiCl, Li2S-SiS2-B2S3-LiI, Li2S-SiS2-P2S5-LiI, Li2S-B2S3, and Li2S-P2S5-Z. m S n(m and n are positive numbers, Z is Ge, Zn, or Ga), Li2S-GeS2, Li2S-SiS2-Li3PO4, Li2S-SiS2-Li p MO q (p and q are positive numbers, M is P, Si, Ge, B, Al, Ga, or In), Li 7-x PS 6-x Cl x (0≤x≤2), Li 7-x PS 6-x Br x (0≤x≤2), Li 7-x PS 6-x I x (0≤x≤2), etc. These can be used individually or in combination of two or more.

[0169] The oxide-based solid electrolyte may include garnet compounds (e.g., LLZO-based compounds), sodium superionic conductors (NASICON) compounds, and perovskite compounds, etc.

[0170] The LLZO-based compound can be an oxide containing lithium, lanthanum, and zirconium. The LLZO-based compound may further contain Al, Ga, In, Sc, Ba, Nb, etc. For example, it may contain Li7La3Zr2O. 12 wait.

[0171] The sodium superionic conductor compound can be a compound having a sodium superionic conductor crystal structure or a sodium superionic conductor-like crystal structure, for example, it can include LATP-based compounds, LAGP-based compounds, etc.

[0172] The LATP-based compound can be a phosphate containing lithium, aluminum, and titanium. For example, it can include Li 1.3 Al 0.3 Ti 1.7 (PO4)3, etc.

[0173] The LAGP-based compound can be a phosphate containing lithium, aluminum, and germanium. For example, it can include Li... 1.5 Al 0.5 Ge 1.5 (PO4)3, etc.

[0174] The perovskite compound is a compound having a perovskite crystal structure or a perovskite-like crystal structure, and may include LLTO-based compounds.

[0175] The LLTO-based compound can be an oxide containing lithium, lanthanum, and titanium. For example, it can include Li. 0.31 La 0.56TiO3, etc.

[0176] The polymer electrolyte membrane can be formed from a composition comprising the copolymer, the lithium salt, and a solvent.

[0177] In the composition, the content of the lithium salt can be from 90 parts by weight to 500 parts by weight relative to 100 parts by weight of the copolymer.

[0178] The solvent is not particularly limited, but may include, for example, N,N-dimethylformamide (DMF).

[0179] For example, the composition can be dried at a temperature of about 60°C to 100°C for about 40 hours to 100 hours to prepare a polymer electrolyte membrane.

[0180] According to the present invention, a lithium secondary battery comprising the polymer electrolyte membrane is provided.

[0181] The lithium secondary battery includes: a positive electrode; a negative electrode disposed opposite to the positive electrode; and a polymer electrolyte membrane disposed between the positive electrode and the negative electrode. The polymer electrolyte membrane can physically separate the negative electrode and the positive electrode while also functioning as a migration medium for lithium ions.

[0182] The positive electrode may include a positive electrode current collector and a layer of positive electrode active material disposed on at least one side of the positive electrode current collector.

[0183] The positive electrode current collector may include stainless steel, nickel, aluminum, titanium, or alloys thereof. The positive electrode current collector may also include aluminum or stainless steel surface-treated with carbon, nickel, titanium, or silver.

[0184] The positive electrode active material layer may contain a positive electrode active material. The positive electrode active material may contain a compound capable of reversibly inserting and deintercalating lithium ions.

[0185] According to an exemplary embodiment, the positive electrode active material may comprise a lithium-nickel metal oxide. The lithium-nickel metal oxide may further comprise at least one of cobalt (Co), manganese (Mn), and aluminum (Al).

[0186] In some embodiments, the positive electrode active material or the lithium-nickel metal oxide may include a layered structure or a crystal structure represented by the following chemical formula 8.

[0187] [Chemical Formula 8]

[0188] Li x Ni a M b O2+Z

[0189] In chemical formula 8, the values ​​can be 0.9≤x≤1.2, 0.6≤a≤0.99, 0.01≤b≤0.4, and -0.5≤z≤0.1. As mentioned above, M can include Co, Mn, and / or Al.

[0190] The chemical structure represented by Formula 8 indicates the bonding relationships contained in the layered or crystalline structure of the positive electrode active material, and does not exclude other additional elements. For example, M includes Co and / or Mn, and Co and / or Mn can be provided together with Ni as the main active element of the positive electrode active material. Formula 8 is provided to represent the bonding relationships of the main active elements and should be understood as a formula that includes the introduction and substitution of additional elements.

[0191] In one embodiment, in addition to the primary active element, auxiliary elements may be further included to enhance the chemical stability of the positive electrode active material or the layered / crystal structure. These auxiliary elements may be incorporated into the layered / crystal structure and form bonds; this should be understood to also include the chemical structures represented by Formula 8.

[0192] The auxiliary element may include at least one of, for example, Na, Mg, Ca, Y, Ti, Hf, V, Nb, Ta, Cr, Mo, W, Fe, Cu, Ag, Zn, B, Al, Ga, C, Si, Sn, Sr, Ba, Ra, P, or Zr. The auxiliary element may act as an auxiliary active element, together with Co or Mn, to contribute to the capacity / power activity of the positive electrode active material; for example, Al.

[0193] For example, the positive electrode active material or the lithium-nickel metal oxide may include a layered structure or a crystal structure represented by the following chemical formula 8-1.

[0194] [Chemical Formula 8-1]

[0195] Li x Ni a M1 b1 M2 b2 O 2+z

[0196] In chemical formula 8-1, M1 may include Co, Mn and / or Al. M2 may include the aforementioned auxiliary elements. In chemical formula 8-1, the values ​​can be 0.9≤x≤1.2, 0.6≤a≤0.99, 0.01≤b1+b2≤0.4, and -0.5≤z≤0.1.

[0197] The positive electrode active material may further include coating elements or doping elements. For example, elements that are substantially the same as or similar to the auxiliary elements described above can be used as coating elements or doping elements. For example, one or more combinations of the elements described above can be used as coating elements or doping elements.

[0198] The coating element or doping element may exist on the surface of the lithium-nickel metal oxide particles, or may penetrate through the surface of the lithium-nickel metal composite oxide particles and be contained within the bonding structure represented by the chemical formula 8 or chemical formula 8-1.

[0199] The positive electrode active material may contain nickel-cobalt-manganese (NCM)-based lithium oxide. In this case, NCM-based lithium oxide with increased nickel content can be used.

[0200] Ni can be provided as a transition metal related to the power and capacity of lithium secondary batteries. Therefore, as described above, by using a high-content (High-Ni) composition for the positive electrode active material, a high-capacity positive electrode and a high-capacity lithium secondary battery can be provided.

[0201] However, with increasing Ni content, the long-term storage stability and lifetime stability of the cathode or secondary battery may decrease relatively, and side reactions with the electrolyte may also increase. However, according to an exemplary embodiment, conductivity can be maintained by including Co, while lifetime stability and capacity retention characteristics can be improved by including Mn.

[0202] The Ni content in the NCM-based lithium oxide (e.g., the mole fraction of nickel in the total moles of nickel, cobalt, and manganese) can be 0.6 or more, 0.7 or more, or 0.8 or more. In some embodiments, the Ni content can be 0.8 to 0.95, 0.82 to 0.95, 0.83 to 0.95, 0.84 to 0.95, 0.85 to 0.95, or 0.88 to 0.95.

[0203] In some embodiments, the positive electrode active material may further comprise lithium cobalt oxide-based active material, lithium manganese oxide-based active material, lithium nickel oxide-based active material, or lithium iron phosphate (LFP)-based active material (e.g., LiFePO4).

[0204] In some embodiments, the positive electrode active material may include, for example, a manganese-rich (Mn-rich) based active material having a chemical structure or crystal structure represented by Formula 9, a lithium-rich layered oxide (LLO) / over-lithiated oxide (OLO) based active material, or a cobalt-less based active material.

[0205] [Chemical Formula 9]

[0206] p[Li2MnO3]·(1-p)[Li q JO2]

[0207] In Chemical Formula 9, 0 < p < 1, 0.9 ≤ q ≤ 1.2, and J may include at least one element selected from Mn, Ni, Co, Fe, Cr, V, Cu, Zn, Ti, Al, Mg, and B.

[0208] The positive electrode active material layer may further contain a binder or a conductive material. The binder may agglomerate the positive electrode active material particles and may improve the adhesion between the positive electrode current collector and the positive electrode active material layer, and the conductive material may improve the conductivity of the positive electrode active material layer.

[0209] The binder may include polyvinylidene fluoride (PVDF), poly(vinylidene fluoride-co-hexafluoropropylene), polyacrylonitrile, polymethylmethacrylate, nitrile rubber (NBR), polybutadiene rubber (BR), styrene-butadiene rubber (SBR), etc. In one embodiment, the positive electrode active material layer may contain a PVDF-based binder as the binder.

[0210] The conductive material may include carbon-based conductive materials such as graphite, carbon black, acetylene black, Ketjen black, graphene, carbon nanotubes, vapor-grown carbon fiber (VGCF), carbon fiber, etc. and / or metal-based conductive materials including perovskite materials such as tin, tin oxide, titanium oxide, LaSrCoO3, LaSrMnO3, etc., but is not limited thereto.

[0211] According to an exemplary embodiment, a positive electrode active material layer may be formed on the positive electrode current collector using a positive electrode paste containing the positive electrode active material. The positive electrode paste may contain the positive electrode active material and a solvent, and may further contain a binder and / or a conductive material.

[0212] The solvent may include N-methyl-2-pyrrolidone (NMP), dimethylformamide, dimethylacetamide, N,N-dimethylaminopropylamine, ethylene oxide, tetrahydrofuran, etc. These may be used alone or in combination of two or more.

[0213] The positive electrode slurry may further contain thickeners and / or dispersants. As one embodiment, the positive electrode slurry may contain thickeners such as carboxymethyl cellulose (CMC).

[0214] The positive electrode slurry can be coated onto one side of the positive electrode current collector, and then dried and calendered to form a positive electrode active material layer. The coating can be performed by methods such as gravure coating, slot extrusion coating, multi-layer simultaneous die coating, embossing, doctor blade coating, dip coating, bar coating, and casting, and is not limited to these methods.

[0215] The negative electrode may include a negative electrode current collector and a negative electrode active material layer disposed on at least one side of the negative electrode current collector. Alternatively, the negative electrode may include a lithium metal layer.

[0216] The negative electrode current collector may include copper foil, nickel foil, stainless steel foil, titanium foil, nickel foam, copper foam, polymer substrate coated with conductive metal, etc.

[0217] The negative electrode active material layer may contain a negative electrode active material. A substance capable of adsorbing and desorbing lithium ions can be used as the negative electrode active material. For example, the negative electrode active material may be carbon-based materials such as crystalline carbon, amorphous carbon, carbon composites, and carbon fibers; lithium metal; lithium alloys; silicon (Si)-containing materials; or tin (Sn)-containing materials.

[0218] Examples of amorphous carbon include hard carbon, soft carbon, coke, mesocarbon microbeads (MCMB), and mesophase pitch-based carbon fiber (MPCF).

[0219] Examples of crystalline carbon include natural graphite, artificial graphite, graphitized coke, graphitized MCMB, graphitized MPCF, and other graphite-based carbons.

[0220] The negative electrode active material layer may include a lithium-containing metal layer. In one embodiment, the lithium-containing metal layer deposited or coated on the negative electrode current collector can be used as the negative electrode active material layer. In one embodiment, a lithium thin film layer can also be used as the negative electrode active material layer. The lithium-containing metal layer may comprise a lithium alloy, or it may consist solely of lithium metal.

[0221] Elements included in the lithium alloy may include aluminum, zinc, bismuth, cadmium, antimony, silicon, lead, tin, gallium, or indium.

[0222] The negative electrode may include a lithium metal layer. In this case, the negative electrode may not include a negative electrode current collector. For example, the negative electrode may include a lithium foil.

[0223] According to an exemplary embodiment, a negative electrode active material layer can be formed on the negative electrode current collector using a negative electrode slurry containing the negative electrode active material. The negative electrode slurry may contain the negative electrode active material and a solvent, and may further contain a binder and / or a conductive material.

[0224] The solvent may include water, pure water, deionized water, distilled water, ethanol, isopropanol, methanol, acetone, n-propanol, tert-butanol, etc.

[0225] The aforementioned substances, which can be used in the manufacture of the positive electrode, can be used as the adhesive, conductive material, and thickener.

[0226] In some implementations, styrene-butadiene rubber (SBR) based adhesives, carboxymethyl cellulose (CMC), polyacrylic acid based adhesives, and poly(3,4-ethylenedioxythiophene) (PEDOT) based adhesives can be used as negative electrode binders.

[0227] The negative electrode slurry is coated onto one side of the negative electrode current collector, and then dried and calendered to form a negative electrode active material layer. The coating can be performed by methods such as gravure coating, slot extrusion coating, multi-layer simultaneous die coating, embossing, doctor blade coating, dip coating, rod coating, casting, etc., and is not limited to these methods.

[0228] According to some implementation schemes, the negative electrode can be prepared from lithium foil. Alternatively, the negative electrode can be manufactured by forming a lithium metal layer on at least one side of the negative electrode current collector through methods such as electrodeposition, plating, or deposition.

[0229] According to an exemplary embodiment, a positive electrode, a polymer electrolyte membrane, and a negative electrode can be sequentially and repeatedly arranged to form an electrode assembly. In some embodiments, the electrode assembly can be of the winding type, stacking type, z-folding type, or stack-folding type.

[0230] The lithium secondary battery may include the electrode assembly built into the casing. The casing may be a pouch-type casing, a prismatic casing, a cylindrical casing, a coin-type casing, etc.

[0231] The embodiments of the present invention will be further described below with reference to specific experimental examples. The embodiments and comparative examples included in the experimental examples are only for illustrating the present invention and are not intended to limit the scope of the claims. Various changes and modifications can be made to the embodiments within the scope of the present invention and the technical concept, which will be obvious to those skilled in the art, and such variations and modifications also fall within the scope of the claims.

[0232] Synthesis example 1

[0233]

[0234] 9,9-Dimethylfluorene (1 g, 5.15 mmol), biphenyl (7.14 g, 46.33 mmol), and 7-bromo-1,1,1-trifluoroheptan-2-one (13.99 g, 56.62 mmol) were used as monomers, and trifluoromethanesulfonic acid (TFSA) (77.25 g, 514.75 mmol) was used as a catalyst. 23 parts by weight of dichloromethane (DCM) were used as a reaction solvent, relative to 100 parts by weight of the total monomers. The mixture was kept at 5 °C for 30 minutes and reacted at room temperature (25 °C) for 3 hours and 30 minutes to synthesize the copolymer.

[0235] After the reaction, the dispersion containing the copolymer was precipitated in methanol (1300 ml), then washed several times with methanol and dried in a vacuum oven at 40 °C to obtain the copolymer.

[0236] Synthesis example 2

[0237]

[0238] The copolymer of Synthetic Example 1 (2 g, 5.16 mmol) and polyethylene glycol methyl ether (poly(ethylene glycol) methyl ether 400) (6.20 g, 15.4 mmol) containing 8 repeating polyethylene oxide units were used as reactants, and NaOH (0.62 g, 15.49 mmol) was used as a catalyst. 17 parts by weight of dimethylacetamide (DMAc) were used as a reaction solvent relative to 100 parts by weight of the total weight of the reactants. The mixture was kept at 70°C for 1 hour and reacted at 130°C for 3 hours to synthesize the copolymer (weight average molecular weight of 200 kg / mol to 250 kg / mol, polydispersity index (PDI): 3).

[0239] After the reaction, the dispersion containing the copolymer was precipitated in distilled water, then washed several times with distilled water, and then dried in an oven at 40°C to obtain the copolymer.

[0240] Experimental Example 1: Structure Confirmation of the Copolymer

[0241] (1) 1 H-NMR analysis

[0242] Confirmation of copolymers from Synthetic Example 1 and Synthetic Example 2 1 H-NMR results.

[0243] Figure 1 and Figure 2 The copolymers of Synthetic Example 2 and Synthetic Example 1 are respectively 1 ¹H-NMR results. Analysis was performed on the dispersion containing the copolymer and solvent, using CDCl₃ as the solvent.

[0244] Reference Figure 1 and Figure 2 The copolymers of Synthetic Example 1 and Synthetic Example 2 showed peaks (7-8 ppm) of phenyl-derived polymer backbone and peaks (1-3.5 ppm) of alkylene (linking groups that bond polymer segments of side chains to the backbone) and fluorene methyl groups in the polymer backbone.

[0245] Furthermore, in the copolymer of Synthetic Example 1, the peak intensity of the methylene group (carbon 11) bonded to Br changed in the spectrum of the copolymer of Synthetic Example 2, and it was shown that the peaks of carbons 12 and 13, derived from the polyether segment, added to the copolymer of Synthetic Example 2 had high intensities. Integration of the peaks derived from carbon 11 and those derived from carbons 12 and 13 confirmed that the copolymer of Synthetic Example 1 was converted to the copolymer of Synthetic Example 2 at a conversion rate of 77 mol%.

[0246] (2) FT-IR analysis

[0247] The FT-IR analysis results of the copolymers of Synthetic Example 1 and Synthetic Example 2 were confirmed.

[0248] Figure 3 These are the FT-IR analysis results of the copolymers from Synthetic Example 1 and Synthetic Example 2.

[0249] Reference Figure 3 The analysis results of the copolymer of Synthetic Example 2 showed peaks (1450-1465 cm⁻¹) originating from vinyl and methyl groups contained in the polyether segments. -1 2840-3000cm -1 ) and peaks originating from carbon-oxygen bonds (1085-1150 cm⁻¹) -1 ).

[0250] Experimental Example 2: Evaluation of the thermal stability of copolymers

[0251] (1) Differential scanning calorimetry (DSC) analysis

[0252] For the copolymers of Synthesis Example 1 and Synthesis Example 2, the temperature was increased from room temperature (25°C) to 120°C at a rate of 20°C / min and held at 120°C for 1 minute. Then, the temperature was decreased to -70°C at a rate of 20°C / min and held for 10 minutes to stabilize them.

[0253] The temperature was then increased to 120°C at a rate of 20°C / min, and the glass transition temperature (Tg) of the copolymer was measured under a nitrogen atmosphere.

[0254] Figure 4 The results are DSC analysis of the copolymers from Synthesis Example 1 and Synthesis Example 2.

[0255] Reference Figure 4 The inflection point (arrow) of the DSC curve was confirmed as the glass transition temperature. The copolymer of Synthetic Example 1 had a glass transition temperature of 177.9 °C, and the copolymer of Synthetic Example 2 had a glass transition temperature of 148.9 °C. The copolymer of Synthetic Example 2 exhibited suitable thermal stability while showing improved flexibility compared to the copolymer of Synthetic Example 1.

[0256] (2) Thermogravimetric analysis (TGA)

[0257] The copolymers of Synthetic Example 1 and Synthetic Example 2, as well as polyethylene glycol (mPEG) as a reference, were heated from room temperature (25°C) to 120°C at a rate of 20°C / min and held at 120°C for 10 minutes to remove residual moisture and stabilize them.

[0258] The temperature was then lowered to 60°C at a rate of 20°C / min, and then increased from 60°C to 800°C at a rate of 10°C / min. The weight change of the copolymer was measured under a nitrogen atmosphere to perform thermogravimetric analysis (TGA).

[0259] The analysis results showed that the 5% wt% decomposition temperature (the point at which the weight decreases to 95%) of the copolymer of Synthetic Example 2 was 331.4℃, while the 5% wt% decomposition temperature of the copolymer of Synthetic Example 1 was 338.2℃. Compared with the copolymer of Synthetic Example 2, the copolymer of Synthetic Example 1 exhibited higher thermal stability.

[0260] Experimental Example 3: Evaluation of the mechanical and physical properties of copolymers

[0261] The copolymers of Synthetic Example 1 and Synthetic Example 2 were used to manufacture ASTM D 638 type V specimens (dog-bone shape).

[0262] After connecting the 250N load sensor to the LLOYD UTM LS1 equipment, secure the test piece.

[0263] Five specimens made using the copolymer of Synthetic Example 1 were stretched at an elongation of 5 mm / min to obtain strain-stress curves, and tensile strength and elongation at break were calculated.

[0264] Five specimens made using the copolymer from Synthesis Example 2 were stretched at an elongation of 5 mm / min to obtain strain-stress curves, and tensile strength and elongation at break were calculated.

[0265] For the five specimens, calculate the average value and standard deviation of tensile strength and elongation at break, respectively.

[0266] Figure 5 These are the strain-stress curves of the copolymers of Synthetic Example 1 and Synthetic Example 2.

[0267] Reference Figure 5 The copolymer of Synthetic Example 1 has a tensile strength of 31.8 ± 5.4 MPa and an elongation at break of 49.8 ± 2.0%. On the other hand, the copolymer of Synthetic Example 2 has a tensile strength of 1.1 ± 0.4 MPa and an elongation at break of 1574.0 ± 279.0%. Therefore, the copolymer of Synthetic Example 2 has low tensile strength and high elongation at break, thereby providing improved flexibility. More specifically, the copolymer of Synthetic Example 2 has a significantly lower tensile strength than the copolymer of Synthetic Example 1, while having a significantly higher elongation at break compared to the copolymer of Synthetic Example 1.

[0268] Examples 1 to 4: Manufacturing of Polymer Electrolyte Membranes

[0269] Add 0.1 g of the polymer from Synthesis Example 2 to a 10 mL vial, then mix with 2 mL of N,N-dimethylformamide (DMF) and disperse completely in a stirrer at 80 °C to prepare a polymer dispersion.

[0270] In 2 mL vials, 0.1 g, 0.15 g, 0.23 g, and 0.4 g of lithium bis(fluorosulfonyl)imide (LiFSI) were dissolved in 1 mL of DMF to prepare lithium salt solutions.

[0271] While stirring the polymer dispersion, the lithium salt solution is added dropwise using a syringe to prepare a polymer electrolyte membrane manufacturing composition containing 50%, 60%, 70%, or 80% lithium salt in the solid form.

[0272] After membrane formation, to facilitate separation, the above-mentioned polymer electrolyte membrane manufacturing composition was poured into polytetrafluoroethylene (PTFE) petri dishes and dried in a vacuum oven at 80°C for 48 to 96 hours to produce polymer electrolyte membranes of Examples 1 to 4 with a thickness of about 30 μm to 40 μm.

[0273] The manufacturing process is carried out in a glove box.

[0274] [Comparative Example 1]

[0275] When using the polymer of Synthesis Example 1, the polymer electrolyte membrane could not be manufactured in the same manner as in the Examples due to the reduction in the physical properties of the polymer.

[0276] Experimental Example 4: Evaluation of the thermal stability of electrolyte membranes

[0277] The weight change of the polymer electrolyte membrane of the example was measured by thermogravimetric analysis (TGA) at a temperature of 10°C / min from room temperature (25°C) to 800°C under a nitrogen atmosphere.

[0278] Figure 6 These are the TGA analysis results of the polymer electrolyte membranes from Examples 1 to 4.

[0279] Experimental Example 5: Evaluation of the ionic conductivity of electrolyte membranes

[0280] The bulk impedance of the electrolyte membrane is measured by electrochemical impedance spectroscopy (EIS), and then the ionic conductivity is measured by the bulk impedance.

[0281] Specifically, in order to measure impedance, the polymer electrolyte membrane of the embodiment was cut into a circle with a diameter of 1.9 cm, and a 2023 coin-shaped battery was manufactured with stainless steel electrodes placed on both sides of the electrolyte membrane in a symmetrical configuration, and the measurement was performed using an electrochemical workstation (SP-150, ProDigitek, Australia).

[0282] The measurement conditions were as follows: at room temperature (25℃), the frequency of the alternating current was varied from 1.00MHz to 0.1Hz and the impedance was measured. The ionic conductivity was then calculated using the following formula.

[0283] [Mode]

[0284] Ionic conductivity (σ) [Scm] -1 ]=L / RS

[0285] In the formula, L is the thickness of the polymer electrolyte membrane, R is the volume resistance value, and S is the area (diameter of 15 mm) of the stainless steel (SUS) (blocking electrode) used in the manufacture of the coin-shaped battery.

[0286] Figure 7 These are the EIS results of the polymer electrolyte membranes of Examples 1 to 4.

[0287] Table 1 below shows the ionic conductivity of the polymer electrolyte membranes of the embodiments.

[0288] [Table 1]

[0289]

[0290] Reference Figure 7 As shown in Table 1, the ionic conductivity of the polymer electrolyte membrane in the embodiment is improved.

[0291] In particular, the polymer electrolyte membranes of Examples 2 to 3, which contain polymers and lithium salts, have higher ionic conductivity at appropriate contents.

[0292] The above description is merely an example of applying the principles of this invention. Other configurations may be further included without departing from the scope of this invention.

Claims

1. A polymer electrolyte membrane for lithium secondary batteries, comprising a copolymer, said copolymer having: The main chain comprises a first repeating unit represented by the following chemical formula 1 and a second repeating unit represented by the following chemical formula 2; Fluoroalkyl groups, wherein the fluoroalkyl groups are bonded to the main chain as side chains; and Polymer segments, which are side-chain bonded to the main chain and contain oxygen: [Chemical Formula 1] [Chemical Formula 2] In chemical formulas 1 to 2, R1 and R2 are each independently hydrogen or an alkyl group having 1 to 10 carbon atoms. R3 to R5 are each independently hydrogen, an alkyl group having 1 to 60 carbon atoms, an alkenyl group having 2 to 60 carbon atoms, an alkynyl group having 2 to 60 carbon atoms, or an arylthio group having 6 to 60 carbon atoms. n, m, and p are each independently 0 or an integer from 1 to 4. q is an integer from 2 to 4. This is the bond point.

2. The polymer electrolyte membrane for lithium secondary batteries according to claim 1, wherein, The chemical formula 1 is represented by the following chemical formula 1-1: [Chemical Formula 1-1] 。 3. The polymer electrolyte membrane for lithium secondary batteries according to claim 1, wherein, Chemical formula 2 is represented by either chemical formula 2-1 or chemical formula 2-2: [Chemical Formula 2-1] [Chemical Formula 2-2] 。 4. The polymer electrolyte membrane for lithium secondary batteries according to claim 1, wherein, The ratio of the number of the second repeating units to the number of the first repeating units is 0.1 to 10.

5. The polymer electrolyte membrane for lithium secondary batteries according to claim 1, wherein, The fluoroalkyl group has a structure in which at least one of the hydrogen atoms of an alkyl group having 1 to 10 carbon atoms is substituted with fluorine.

6. The polymer electrolyte membrane for lithium secondary batteries according to claim 1, wherein, The fluoroalkyl group includes at least one selected from trifluoromethyl, pentafluoroethyl, trifluoroethyl and heptafluoropropyl.

7. The polymer electrolyte membrane for lithium secondary batteries according to claim 1, wherein, The fluoroalkyl group is directly bonded to the main chain.

8. The polymer electrolyte membrane for lithium secondary batteries according to claim 1, wherein, The polymer segments include polyether segments or poly(meth)acrylate segments.

9. The polymer electrolyte membrane for lithium secondary batteries according to claim 8, wherein, The polyether segment is represented by the following chemical formula 3: [Chemical Formula 3] In the aforementioned chemical formula 3, L is a direct bond or an alkylene group having 1 to 10 carbon atoms, R6 is an alkyl group having 1 to 10 carbon atoms, R7 is an alkylene group having 1 to 10 carbon atoms, and r is an integer from 5 to 20. This is the bonding point with the main chain.

10. The polymer electrolyte membrane for lithium secondary batteries according to claim 1, wherein, The main chain contains a third repeating unit represented by the following chemical formula 4: [Chemical Formula 4] In the chemical formula 4, R f R6 is a fluoroalkyl group with 1 to 10 carbon atoms, R7 is an alkylene group with 1 to 10 carbon atoms, and r is an integer from 5 to 20. This is the bond point.

11. The polymer electrolyte membrane for lithium secondary batteries according to claim 1, wherein, The copolymer has a weight-average molecular weight of 10 kg / mol to 400 kg / mol.

12. The polymer electrolyte membrane for lithium secondary batteries according to claim 1, wherein, The polymer electrolyte membrane for lithium secondary batteries has a thickness of 20 μm to 100 μm.

13. The polymer electrolyte membrane for lithium secondary batteries according to claim 1, wherein, The polymer electrolyte membrane for the lithium secondary battery has a density of 0.2%. 10 -6 S / cm to 100 10 -6 Ionic conductivity in S / cm.

14. The polymer electrolyte membrane for lithium secondary batteries according to claim 1, wherein, The polymer electrolyte membrane for the lithium secondary battery contains a lithium salt. The lithium salt content in the total weight of the polymer electrolyte membrane for the lithium secondary battery is 50% to 90% by weight.

15. A lithium secondary battery, comprising: positive electrode; The negative electrode is positioned opposite to the positive electrode. as well as The polymer electrolyte membrane for a lithium secondary battery according to claim 1, wherein the polymer electrolyte membrane for a lithium secondary battery is disposed between the positive electrode and the negative electrode.

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