KR20240086226A - Solid electrolyte composition, solid electrolyte formed from the composition and lithium secondary battery including the same electrolyte - Google Patents

Abstract

The present invention relates to a thiourethane compound represented by the following formula (1); lithium salt; and a cross-linking agent containing two or more thiol groups. A solid electrolyte composition containing a can be provided.
[Formula 1]

_{In Formula 1 , ​ ​} It is one of an alkylene group, a substituted or unsubstituted C ₃ -C ₁₆ cycloalkylene group, and a substituted or unsubstituted C ₆ -C ₁₆ arylene group, and n is a natural number in the range of 10 to 1000.

Description

Solid electrolyte composition, solid electrolyte formed therefrom, and lithium secondary battery comprising the same

The present invention relates to a solid electrolyte composition, a solid electrolyte formed therefrom, and a lithium secondary battery containing the same, and specifically, the low-temperature output characteristics of the secondary battery are improved and electrochemical stability is improved by suppressing crystallization at low temperatures. It relates to a solid electrolyte, a composition comprising the same, and a lithium secondary battery containing the same.

Various methods are being explored to increase the energy density of lithium-ion batteries, and one of them is the use of lithium metal in the cathode. However, lithium ion batteries using lithium metal negative electrodes have a problem in which battery performance is significantly reduced due to the lithium dendrite phenomenon that occurs during charging/discharging. In addition, existing lithium-ion batteries have a problem with low battery stability due to the use of flammable liquid electrolytes. To improve this, research is being actively conducted on the development of solid-state batteries using solid electrolytes with high ionic conductivity and high electrochemical stability.

In general, in all-solid-state batteries, linear polymers or cross-linked polymers of homopolymer or copolymer with ethylene oxide as the basic unit are mainly used as ion conductive polymers for forming solid electrolytes, but these polymers are not crystallized. There is a problem that the output characteristics and electrochemical characteristics of the all-solid-state battery are reduced due to low ionic conductivity at low temperatures.

Therefore, there is a need for the development of a solid electrolyte with improved output characteristics at low temperatures and excellent ionic conductivity.

The invention was made to solve the above-mentioned problems. The object of the present invention is to provide a solid electrolyte composition with improved lithium ion mobility, suppressed crystallization at low temperatures, excellent ionic conductivity, and excellent electrochemical stability. The aim is to provide a solid electrolyte formed therefrom.

The object of the present invention is to provide a lithium secondary battery with excellent output characteristics at low temperatures and excellent electrochemical stability and safety by introducing the above-described solid electrolyte.

In order to solve the above-described problems, the present invention provides a thiourethane compound represented by the following formula (1); lithium salt; and a cross-linking agent containing two or more thiol groups. A solid electrolyte composition containing a can be provided.

[Formula 1]

_{In Formula 1 , ​ ​} It is one of an alkylene group, a substituted or unsubstituted C ₃ -C ₁₆ cycloalkylene group, and a substituted or unsubstituted C ₆ -C ₁₆ arylene group, and n is a natural number in the range of 10 to 1000.

In one example of the present invention, the , , and It may be one or more selected from the group consisting of.

In addition, A is , , , , and It may be one or more selected from the group consisting of.

In one embodiment of the present invention, the crosslinking agent is , , , , , and It may include one or more selected from the group consisting of.

Additionally, the cross-linking agent may be included in the range of 1% to 30% by weight based on the content of the thiourethane compound.

Meanwhile, the lithium salt may be included in the range of 10% by weight to 70% by weight based on the total composition.

In one embodiment of the present invention, the solid electrolyte composition according to the present invention may further include a plasticizer.

In one embodiment of the present invention, the solid electrolyte composition according to the present invention may further include a thiourethane compound represented by the following formula (2).

[Formula 2]

_{In Formula 2 , ​} It is one of a C ₁₂ alkylene group, a substituted or unsubstituted C ₃ -C ₁₆ cycloalkylene group, and a substituted or unsubstituted C ₆ -C ₁₆ arylene group, and m is a natural number in the range of 10 to 1000.

At this time, X' of Formula 2 is different from X of Formula 1, A' of Formula 2 is different from A of Formula 1, or X' of Formula 2 is different from A' in Formula 2 may be different from A in Formula 1.

In one example of the present invention, X' is , , and It may be one or more selected from the group consisting of.

In addition, the A' is , , , , and It may be one or more selected from the group consisting of.

Meanwhile, in one embodiment of the present invention, the compound represented by Formula 2 may be included in an amount of 1% by weight or more and 50% by weight or less based on the total composition.

In another embodiment of the present invention, the present invention can provide a solid electrolyte comprising units derived from the above-described solid electrolyte composition. The solid electrolyte is a thiourethane compound represented by the following formula (1); lithium salt; and a crosslinking agent containing two or more thiol groups.

[Formula 1]

_{In Formula 1 , ​ ​} It is one of an alkylene group, a substituted or unsubstituted C ₃ -C ₁₆ cycloalkylene group, and a substituted or unsubstituted C ₆ -C ₁₆ arylene group, and n is a natural number in the range of 10 to 1000.

Additionally, the solid electrolyte according to the present invention may include a crosslinking of the thiourethane compound and a crosslinking agent containing two or more thiol groups.

At this time, the cross-linking may be dynamic cross-linking.

In one embodiment of the present invention, , , and At least one selected from the group consisting of, wherein A is , , , , and It may be one or more selected from the group consisting of.

In one example of the present invention, the crosslinking agent is , , , , , and It may include one or more selected from the group consisting of.

In one embodiment of the present invention, the present invention can provide a lithium secondary battery including the solid electrolyte, an anode, and a cathode.

The solid polymer electrolyte according to the present invention suppresses crystallization, improves the mobility of lithium ions, improves ion conductivity, and has excellent electrochemical stability, which can contribute to improving the stability and output of lithium secondary batteries.

The lithium secondary battery according to the present invention has excellent output characteristics at low temperatures and excellent electrochemical stability and safety, making it suitable for use in electric vehicles.

Before describing the present invention in more detail, the meaning of terms used in this specification will be defined.

In this specification, unless otherwise stated, the fact that a substituent is “substituted or unsubstituted” means that the substituent includes both cases where the substituent is substituted by a functional group to be described later and cases where the substituent is not substituted.

Here, the functional group in case of substitution is, for example, alkyl, acyl, cycloalkyl (including dicycloalkyl and tricycloalkyl), haloalkyl, aryl ( aryl), heteroaryl, heteroalicyclic, hydroxy, alkoxy, azide, amine, ketone, ether, amide (amide), ester, triazole, isocyanate, arylalkyloxy, aryloxy, mercapto, alkylthio, arylthio , cyano, halogen, carbonyl, thiocarbonyl, O-carbamyl, N-carbamyl, O-thiocarbamyl (O-thiocarbamyl), N-thiocarbamyl, C-amido (C-amido), N-amido (N-amido), S-sulfonamido (S-sulfonamido), N- Sulfonamido (N-sulfonamido), C-carboxy (C-carboxy), O-carboxy (O-carboxy), isocyanate, thiocyanate, isothiocyanate, nitro ( nitro, silyl, trihalomethane sulfonyl, pyrrolidinone, pyrrolidine, piperidine, piperazine, morpholine ), aldehyde, phosphorus, sulfur, phosphate, phosphite, sulfate, disulfide, oxy; and aminos containing hydrocarbylmono- and di-(hydrocarbyldi-) substituted amino groups, and derivatives thereof, but are not limited thereto and include various functional groups commonly used in the art. do. Also, substituted means that the functional group is bonded to at least one carbon of the substituent.

As used herein, “alkyl group” refers to a monovalent aliphatic hydrocarbon group. The alkyl groups include linear (unbranched) and branched (branched). Alkyl groups include, for example, methyl, ethyl, propyl, isopropyl, n-butyl, n-pentyl, and n-hexyl. It may be one or more selected from the group consisting of (n-hexyl), but is not necessarily limited thereto.

As used herein, “cycloalkyl group” refers to a monovalent aliphatic cyclic hydrocarbon group. The cycloalkyl group is, for example, cyclobutyl, cyclopentyl, cyclohexyl, cycloheptyl, cyclooctyl, cyclononyl, and cyclodecyl. It is selected from the group consisting of (cyclodecyl). However, it is not necessarily limited to this.

Additionally, in this specification, “alkylene group” refers to a divalent aliphatic hydrocarbon group. The alkylene group represents, for example, one selected from methylene, ethylene, propylene, butylene, pentylene, and hexylene. However, it is not necessarily limited to this.

As used herein, “cycloalkylene group” refers to a divalent aliphatic cyclic hydrocarbon group. The positional relationship of the bivalent bond arm is not mattered. For example, it may be selected from the group consisting of 1,2-cycloalkylene group, 1,3-cycloalkylene group, 1,4-cycloalkylene group, and 1,5-cycloalkylene group. The cycloalkylene group is, for example, 1,2-cyclobutylene, 1,3-cyclobutylene, and 1,2-cyclopentylene. , 1,3-cyclopentylene, 1,2-cyclohexylene, 1,3-cyclohexylene, 1, 4-cyclohexylene, 1,2-cycloheptylene, 1,3-cycloheptylene, 1,4-cycloheptyl Len group (1,4-cyclohelptylene), 1,2-cyclooctylene group (1,2-cyclooctylene), 1,3-cyclooctylene group (1,3-cyclooctylene), 1,4-cyclooctylene group (1,4 -cyclooctylene), and 1,5-cyclooctylene (1,5-cyclooctylene), but is not limited thereto.

As used herein, “heteroalkyl group” means that one or more carbon atoms in the carbon chain of the alkyl group are replaced with a hetero atom.

As used herein, “heteroalkylene group” means that one or more carbon atoms in the carbon chain of an alkylene group are substituted with a heteroatom. Also, of C _{a ~} C _b A heteroalkylene group refers to a heteroalkylene group having a to b carbon atoms among heteroalkylene groups.

As used herein, “cycloheteroalkylene group” means that one or more carbon atoms in the carbon chain of a cycloalkyl group are replaced with a hetero atom.

As used herein, “heteroatom” means an atom other than carbon and hydrogen.

In this specification, an "aryl group" is an aromatic substituent having a univalent shared π electron system, and includes a monocyclic or polycyclic group of two or more rings, and a ring This means that all elements are made of carbon. Aryl groups include both substituted and unsubstituted groups. Examples of aryl groups include , , , , , and However, it is not necessarily limited to this.

In this specification, “arylene group” refers to a divalent aromatic substituent that has one additional bonding arm in the aryl group.

In this specification, “heteroaryl group” refers to an aromatic substituent having a univalent shared pi electron system, and at least one of the atoms forming the ring is a heteroatom. Examples of heteroaryl groups include: , , , , , , , , , , , , , , , , , , , , , , , and Examples include, but are not limited to, these.

Here, R ^m is H, a C _1-20 alkyl group, or a C ₃ to C ₁₄ heteroaryl group.

Additionally, in this specification, a “heteroarylene group” refers to an aromatic substituent having a divalent shared pi electronic system, and represents a form in which the heteroarylene group has one more bonding arm.

As used herein, “haloalkyl group” specifically refers to an alkyl group in which one or more hydrogens are replaced with halogen (F, Cl, Br, I) atoms. Additionally, the haloalkyl group of C _{a to} C _b refers to a haloalkyl group having a to b carbon atoms. “Haloalkylene group” means an alkylene group in which one or more hydrogens have been replaced with a halogen atom.

Additionally, in this specification, “haloalkylene group” specifically means an alkylene group in which one or more hydrogens are replaced with a halogen atom. Additionally, the haloalkylene group of C _a to C _b refers to a haloalkylene group having a to b carbon atoms.

Additionally, in this specification, “amide group” refers to a -C(O)NH- bond, and the hydrogen bonded to nitrogen in the amide bond may be substituted or unsubstituted.

In addition, in this specification, “no substituent exists” means a form in which both atoms are directly bonded without the corresponding substituent. For example, when substituent A is not present in a molecule of the form CH ₃ -A-CH ₃ , the chemical formula of the molecule is CH ₃ -CH ₃ .

Hereinafter, the present invention will be described in more detail with reference to specific embodiments. This is not intended to limit the technology described herein to specific embodiments, but should be understood to include various modifications, equivalents, and/or alternatives to the embodiments of the present invention. In connection with the description of the drawings, similar reference numbers may be used for similar components.

In order to clearly explain the present invention in the drawings, parts that are not relevant to the description are omitted, and the thickness is enlarged to clearly express various layers and regions, and components with the same function within the scope of the same idea are referred to by the same reference. It can be explained using symbols.

In this specification, expressions such as “have,” “may have,” “includes,” or “may include” refer to the presence of the corresponding feature (e.g., a numerical value, function, operation, or component such as a part). , and does not rule out the existence of additional features.

As used herein, expressions such as “A or B,” “at least one of A or/and B,” or “one or more of A or/and B” may include all possible combinations of the items listed together. . For example, “A or B”, “at least one of A and B”, or “at least one of A or B” (1) includes at least one A, (2) includes at least one B, or (3) it may refer to all cases including both at least one A and at least one B.

Hereinafter, the configuration and effects of the present invention will be described in detail.

1. Solid electrolyte composition

The present inventors developed the present invention to solve the problem of poor output of secondary batteries, such as a significant decrease in ionic conductivity at low temperatures due to crystallization of ion-conducting polymers at low temperatures in conventional solid electrolytes for all-solid-state batteries. reached.

In one embodiment of the present invention, the solid electrolyte composition according to the present invention includes a thiourethane compound represented by the following formula (1); lithium salt; and a crosslinking agent containing two or more thiol groups.

[Formula 1]

_{In Formula 1 , ​ ​} It is one of an alkylene group, a substituted or unsubstituted C ₃ -C ₁₆ cycloalkylene group, and a substituted or unsubstituted C ₆ -C ₁₆ arylene group, and n is a natural number in the range of 10 to 1000.

1) Thiourethane compound

The solid electrolyte according to the present invention may include a thiourethane compound represented by Formula 1 above. The thiourethane compound contains two or more thiourethane bonds within one repeating unit, and can form crosslinks with a crosslinking agent described later. The upper limit of thiourethane bonds contained in one repeating unit is not particularly limited, but may be, for example, 8 or less. Specifically, the thiourethane compound and the cross-linking agent can be bonded through a thiol-ene reaction through a double bond and a thiol group, and cross-linked by hydrogen bonding and/or ionic interaction through ion clusters. can form a network structure.

In one example of the present invention, X of the thiourethane compound is , , and It may be one or more selected from the group consisting of.

In addition, according to one embodiment of the present invention, A of Formula 1 is , , , , and It may be one or more selected from the group consisting of.

The thiourethane compound forms the skeleton of the solid electrolyte through crosslinking and may be included in an amount of 20% by weight or more and/or 85% by weight or less based on the total electrolyte composition. If the content of the thiourethane compound is less than 20% by weight, it may be difficult to manufacture an electrolyte of a fixed shape, and if it exceeds 85% by weight, the content of lithium salt, etc. may be too low and ionic conductivity may decrease.

Additionally, the weight average molecular weight of the thiourethane compound may be 1,000 g/mol or more and/or 1,000,000 g/mol or less. If the weight average molecular weight of the thiourethane compound is less than 1,000 g/mol, the mechanical properties as a solid electrolyte may decrease and the electrochemical stability of the electrolyte may decrease. Conversely, if it exceeds 1,000,000 g/mol, the electrochemical stability of the electrolyte may decrease. There may be a problem in that the ionic conductivity decreases and the crystallinity increases at low temperatures, resulting in a decrease in battery output.

In one embodiment of the present invention, the solid electrolyte composition according to the present invention may further include a thiourethane compound represented by the following formula (2).

[Formula 2]

_{In Formula 2 , ​} It is one of a C ₁₂ alkylene group, a substituted or unsubstituted C ₃ -C ₁₆ cycloalkylene group, and a substituted or unsubstituted C ₆ -C ₁₆ arylene group, and m is a natural number in the range of 10 to 1000.

At this time, at least one of X' and X of Formula 1 and A' and A of Formula 1 may be different from each other. That is, X' and X in Formula 1 are different from each other, A' and A in Formula 1 are different from each other, or X' and can do.

In one example of the present invention, X' of the thiourethane compound represented by Formula 2 is , , and It may be one or more selected from the group consisting of.

In addition, according to one embodiment of the present invention, A' in Formula 2 is , , , , and It may be one or more selected from the group consisting of.

When the solid electrolyte composition according to the present invention further includes a thiourethane compound represented by Formula 2, the thiourethane compound represented by Formula 2 is present in an amount of 1% by weight or more and/or 50% by weight or less based on the total composition. may be included within the scope of. When the solid electrolyte composition according to the present invention includes the compound represented by Formula 2, the total content of the thiourethane compound represented by Formula 1 and the thiourethane compound represented by Formula 2 is 20% by weight or more relative to the total solid electrolyte composition. and/or may be included within the range of 85% by weight or less, and at the same time, the content of the thiourethane compound represented by Formula 2 may be within the range of 1% by weight or more and/or 50% by weight or less based on the total composition. .

2) Cross-linking agent

The solid electrolyte composition according to the present invention may include a crosslinking agent containing two or more thiol groups. The cross-linking agent may form a network-like structure by combining with the above-described thiourethane compound through a plurality of thiol groups.

In one example of the present invention, the crosslinking agent of the solid electrolyte composition according to the present invention is , , , , , and It may include one or more selected from the group consisting of.

The crosslinking agent may contain two or more thiol groups, as well as an aromatic ring, a heterocycloalkylene group, and/or a double bond. Through this, the crosslinking agent can form a dynamic crosslinking bond with the thiourethane compound described above, and the solid electrolyte prepared from the solid electrolyte composition according to the present invention can have the properties of a vitrimer.

In one example, the crosslinking agent of the solid electrolyte composition according to the present invention may be included in an amount of 1% by weight or more and/or 30% by weight or less relative to the content of the thiourethane compound. The content of the cross-linking agent may be 1% by weight, 3% by weight, or 5% by weight, and 30% by weight or less, 25% by weight, 23% by weight, or 20% by weight or less, based on the content of the thiourethane compound. there is. If the content of the cross-linking agent is insufficient, the crystallinity of the polymer may increase due to the strong hydrogen bonding force of thiourethane, which may cause a problem of lowered ionic conductivity due to a decrease in segmental motion of the polymer. If the content of the cross-linking agent exceeds the above range, bulky Structural problems with the crosslinking agent may deteriorate the mechanical properties of polythiourethane.

3) Lithium salt

The lithium salt can be used as an electrolyte salt in a lithium secondary battery. The lithium salt can function as a medium for transferring ions and includes lithium cations (Li ⁺ ), F ^- , Cl ^- , Br ^- , I ^- , NO ₃ ^- , N(CN) ₂ ^- , ClO ₄ ^- , BF ₄ ^- , AlO ₄ ^- , AlCl ₄ ^- , PF ₆ ^- , SbF ₆ ^- , AsF ₆ ^- , BF ₂ C ₂ O ₄ ^- , BC ₄ O ₈ ^- , (CF ₃ ) ₂ PF ₄ ^- , (CF ₃ ) ₃ PF ₃ ^- , (CF ₃ ) ₄ PF ₂ ^- , (CF ₃ ) ₅ PF ^- , (CF ₃ ) ₆ P ^- , CF ₃ SO ₃ ^- , C ₄ F ₉ SO ₃ ^- , CF ₃ CF ₂ SO ₃ ^- , (CF ₃ SO ₂ ) ₂ N ^- , (FSO ₂ ) ₂ N ^- , CF ₃ CF ₂ (CF ₃ ) ₂ CO ^- , (CF ₃ SO ₂ ) ₂ CH ^- , (SF ₅ ) ₃ C ^- , (CF ₃ SO ₂ ) ₃ C ^- , CF ₃ (CF ₂ ) ₇ SO ₃ ^- , CF ₃ CO ₂ ^- , CH ₃ CO ₂ ^- , SCN ^- and (CF ₃ CF ₂ SO ₂ ) ₂ N ^- It may contain one or more anions selected from the group consisting of, but is not necessarily limited to this.

The lithium salt can be appropriately changed within the range commonly used, but in order to obtain the optimal effect of forming an anti-corrosion film on the electrode surface, the content of the lithium salt is 10% by weight or more and/or 70% by weight or less in the solid polymer electrolyte composition. may be included.

The solid polymer electrolyte composition of the present invention includes a lithium salt in the content within the above range, resulting in high lithium cation (Li ⁺ ) ion transport characteristics (i.e., cation transport rate ( transference number)) can be secured, and the effect of reducing the diffusion resistance of lithium ions can be achieved to improve cycle capacity characteristics. At this time, when the lithium salt content is less than 10% by weight, it is difficult to secure sufficient ionic conductivity of lithium ions due to the relatively low lithium ion content. In addition, if the concentration of the lithium salt exceeds 70% by weight, the lithium salt is not solvated in the polymer matrix and a large amount of lithium salt forming an ion-pair exists, so there is no significant increase in effectiveness and it is economical. Since it is disadvantageous, it is desirable to appropriately adjust it to suit the purpose within the above content range.

4) Plasticizer

The solid polymer electrolyte composition according to the present invention may further include a plasticizer.

Plasticizers serve to facilitate the transfer of lithium ions at low temperatures by lowering the crystallinity between polymer chains forming a solid polymer electrolyte, improve the processability of the solid polymer electrolyte, and make it easier to control mechanical strength.

The plasticizer is preferably succinonitrile, glutaronitrile, polyethylene glycol dimethylether, tetraethylene glycol, ethylene carbonate, and propylene carbonate. ), tetraethylene

Glycol dimethyl ether (tetraethylene glycol dimethylether, tetraglyme), dimethyl phthalate, diethyl phthalate, dibutyl phthalate, dioctyl phthalate, cyclic phosphate ), 1-ethyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide [1-ethyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide], 1-butyl-3-methylimidazolium bis( Trifluoromethanesulfonyl)imide [1-butyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide], N-methyl-N-propylpiperidinium bis(trifluoromethanesulfonyl)imide [N-methyl-N -propylpiperidinium bis(trifluoromethanesulfonyl)imide], 1-ethyl-3-methylimidazolium trifluoromethanesulfonate, N-butyl-N-ethylpyrrolidinium bis(trifluoride) It may include one or more selected from lomethanesulfonyl)imide [N-butyl-Nethylpyrrolidinium bis(trifluoromethanesulfonyl)imide], but is not necessarily limited thereto.

The content of the plasticizer may be 10 to 80% by weight of the total solid polymer electrolyte composition. If the content of the plasticizer is less than 10% by weight, the crystallinity of the solid polymer electrolyte may increase at low temperatures, which may cause a problem of lowering ionic conductivity. If it exceeds 80% by weight, the mechanical properties of the solid polymer electrolyte may deteriorate. There may be a problem.

The content of the plasticizer may be preferably 15 to 75% by weight, more preferably 20 to 70% by weight.

5) Solvent

In a preferred embodiment of the present invention, the solid polymer electrolyte composition may further include an organic solvent to adjust viscosity or to improve solubility between monomers used. Organic solvents that can be used include tetrahydrofuran (THF), 2-methyl tetrahydrofuran, dimethylformamide (DMF), acetonitrile, N-methyl-2-pyrrolidone (NMP), and dimethyl sulfoxide ( DMSO), dimethylacetamide (DMAc), dichloromethane, acetone, isopropyl alcohol, methyl ethyl ketone (MEK), etc., but are not necessarily limited to these, and include one or more of these. You can select and use.

2. Solid electrolyte

Additionally, the present invention provides a solid electrolyte formed by curing the solid electrolyte composition.

The curing method in the present invention can form a polymer solid electrolyte membrane through crosslinking through dynamic bonding exchange along with solvent drying. Specifically, a solid electrolyte can be manufactured by coating the solid electrolyte composition on the surface of a film or electrode and curing the solid electrolyte composition through heat treatment.

The coating method may use known coating methods such as slot die, gravure coating, spin coating, spray coating, roll coating, casting, screen printing, or inkjet printing.

The solid electrolyte according to the present invention prepared by this method can exhibit high ionic conductivity even at low temperatures.

4. Lithium secondary battery

In addition, the present invention is an anode; cathode; and a lithium secondary battery comprising the solid electrolyte according to the present invention.

The lithium secondary battery can be manufactured according to conventional methods known in the art. For example, it can be manufactured by applying the solid electrolyte composition on the positive electrode, curing the composition, and stacking the negative electrode.

1) anode

The positive electrode current collector is not particularly limited as long as it is conductive without causing chemical changes in the battery. For example, stainless steel, aluminum, nickel, titanium, calcined carbon, or carbon on the surface of aluminum or stainless steel, Surface treatment with nickel, titanium, silver, etc. can be used.

The positive electrode active material is a compound capable of reversible intercalation and deintercalation of lithium, and may specifically include a lithium composite metal oxide containing lithium and one or more metals such as cobalt, manganese, nickel, or aluminum. there is. More specifically, the lithium composite metal oxide is lithium-manganese-based oxide (for example, LiMnO ₂ , LiMn ₂ O ₄ , etc.), lithium-cobalt-based oxide (for example, LiCoO ₂ , etc.), lithium-nickel-based oxide. (for example, LiNiO ₂ etc.), lithium-nickel-manganese oxide (for example, LiNi _1-Y Mn _Y O ₂ (where 0<Y<1), LiMn _2-z Ni _z O ₄ ( Here, 0<Z<2), etc.), lithium-nickel-cobalt-based oxide (for example, LiNi _1-Y 1Co _Y1 O ₂ (here, 0<Y1<1), etc.), lithium-manganese-cobalt oxides (for example, LiCo _1-Y 2Mn _Y2 O ₂ (where 0<Y2<1), LiMn _2-z1 Co _z1 O ₄ (where 0<Z1<2), etc.), lithium-nickel -Manganese-cobalt based oxide (for example, Li(Ni _p Co _q Mn _r1 )O ₂ (where 0<p<1, 0<q<1, 0<r1<1, p+q+r1= 1) or Li(Ni _p1 Co _q1 Mn _r2 )O ₄ (where 0<p1<2, 0<q1<2, 0<r2<2, p1+q1+r2=2), etc.), or lithium- Nickel-cobalt-transition metal (M) oxides (e.g. Li(Ni _p2 Co _q2 Mn _r3 MS ₂ )O ₂ (where M is Al, Fe, V, Cr, Ti, Ta, Mg and Mo) selected from the group consisting of, p2, q2, r3 and s2 are each independent atomic fraction of elements, 0 <p2 <1, 0 <q2 <1, 0 <r3 <1, 0 <s2 <1, p2+q2 +r3+s2=1)), etc., and any one or two or more of these compounds may be included.

Among these, in that the capacity characteristics and stability of the battery can be improved, the lithium composite metal oxide is LiCoO ₂ , LiMnO ₂ , LiNiO ₂ , lithium nickel manganese cobalt oxide (for example, Li(Ni _1/3 Mn _1/3 Co _{1 /3} )O ₂ , Li(Ni _0.6 Mn _0.2 Co _0.2 )O ₂ , Li(Ni _0.5 Mn _0.3 Co _0.2 )O ₂ , Li(Ni _0.7 Mn _0.15 Co _0.15 )O ₂ and Li(Ni _0.8 Mn _0.1 Co _0.1 )O ₂ , etc.), or lithium nickel cobalt aluminum oxide (for example, Li(Ni _0.8 Co _0.15 Al _0.05 )O ₂ , etc.).

The positive electrode active material may be included in an amount of 80% to 99% by weight based on the total weight of solids in the positive electrode slurry.

The binder is a component that assists in the bonding of the active material and the conductive material and the bonding to the current collector, and is usually added in an amount of 1 to 30% by weight based on the total weight of solids in the positive electrode slurry. Examples of such binders include polyvinylidene fluoride (PVDF), polyvinyl alcohol, carboxymethylcellulose (CMC), starch, hydroxypropylcellulose, regenerated cellulose, polyvinylpyrrolidone, and tetrafluoride. Roethylene, polyethylene, polypropylene, ethylene-propylene-diene termonomer (EPDM), sulfonated EPDM, styrene-butadiene rubber, fluorine rubber, and various copolymers.

The conductive material is typically added in an amount of 1 to 30% by weight based on the total weight of solids in the positive electrode slurry.

These conductive materials are not particularly limited as long as they are conductive without causing chemical changes in the battery. For example, carbon black, acetylene black (or Denka black), Ketjen black, channel black, furnace black, lamp black, or carbon powder such as thermal black; Graphite powder such as natural graphite, artificial graphite, or graphite with a highly developed crystal structure; Conductive fibers such as carbon fiber and metal fiber; Metal powders such as carbon fluoride, aluminum, and nickel powder; Conductive whiskers such as zinc oxide and potassium titanate; Conductive metal oxides such as titanium oxide; Conductive materials such as polyphenylene derivatives may be used.

The positive electrode slurry may include a solvent. The solvent may include an organic solvent such as NMP (N-methyl-2-pyrrolidone), and may be used in an amount that provides a desirable viscosity when including the positive electrode active material and optionally a binder and a conductive material. For example, the solid content concentration in the slurry containing the positive electrode active material and, optionally, the binder and the conductive material may be 50% by weight to 95% by weight, preferably 70% by weight to 90% by weight.

2) cathode

Additionally, the negative electrode can be manufactured by forming a negative electrode mixture layer on the negative electrode current collector. The negative electrode mixture layer can be formed by coating a negative electrode slurry containing a negative electrode active material, a binder, a conductive material, and a solvent on a negative electrode current collector, followed by drying and rolling.

The negative electrode current collector generally has a thickness of 3 to 500 μm. This negative electrode current collector is not particularly limited as long as it has high conductivity without causing chemical changes in the battery, and for example, copper, stainless steel, aluminum, nickel, titanium, calcined carbon, copper or stainless steel. Surface treatment with carbon, nickel, titanium, silver, etc., aluminum-cadmium alloy, etc. can be used. In addition, like the positive electrode current collector, the bonding power of the negative electrode active material can be strengthened by forming fine irregularities on the surface, and can be used in various forms such as films, sheets, foils, nets, porous materials, foams, and non-woven materials.

In addition, the negative electrode active material is lithium metal, a carbon material capable of reversibly intercalating/deintercalating lithium ions, a metal or an alloy of these metals and lithium, a metal complex oxide, and a material capable of doping and dedoping lithium. It may include at least one selected from the group consisting of a material and a transition metal oxide.

As the carbon material capable of reversibly intercalating/deintercalating lithium ions, any carbon-based anode active material commonly used in lithium ion secondary batteries can be used without particular restrictions, and representative examples include crystalline carbon, Amorphous carbon or a combination thereof can be used. Examples of the crystalline carbon include graphite such as amorphous, plate-shaped, flake-shaped, spherical or fibrous natural graphite or artificial graphite, and examples of the amorphous carbon include soft carbon (low-temperature calcined carbon). Alternatively, hard carbon, mesophase pitch carbide, calcined coke, etc. may be mentioned.

The metal complex oxides include PbO, PbO ₂ , Pb ₂ O ₃ , Pb ₃ O ₄ , Sb ₂ O ₃ , Sb ₂ O ₄ , Sb ₂ O ₅ , GeO, GeO ₂ , Bi ₂ O ₃ , Bi ₂ O ₄ , Bi ₂ O ₅ , Li _x Fe ₂ O ₃ (0≤x≤1), Li _x WO ₂ (0≤x≤1), and Sn _x Me _1-x Me' _y O _z (Me: Mn, Fe , Pb, Ge': Al, B, P, Si, group 1, 2, and 3 elements of the periodic table, 0<x≤1; 1≤z≤8) Any selected from the group may be used.

Materials capable of doping and dedoping lithium include Si, _SiO It is an element selected from the group consisting of rare earth elements and combinations thereof, but not Si), Sn, SnO ₂ , Sn-Y (where Y is an alkali metal, an alkaline earth metal, a Group 13 element, a Group 14 element, a transition metal, and a rare earth elements selected from the group consisting of elements and combinations thereof, but not Sn), and the like, and at least one of these may be mixed with SiO ₂ . The element Y includes Mg, Ca, Sr, Ba, Ra, Sc, Y, Ti, Zr, Hf, Rf, V, Nb, Ta, Db, Cr, Mo, W, Sg, Tc, Re, Bh, Fe, Pb, Ru, Os, Hs, Rh, Ir, Pd, Pt, Cu, Ag, Au, Zn, Cd, B, Al, Ga, Sn, In, Ge, P, As, Sb, Bi, S, Se, It may be selected from the group consisting of Te, Po, and combinations thereof.

Examples of the transition metal oxide include lithium-containing titanium complex oxide (LTO), vanadium oxide, and lithium vanadium oxide.

The negative electrode active material may be included in an amount of 80% to 99% by weight based on the total weight of solids in the negative electrode slurry.

The binder is a component that assists in bonding between the conductive material, the active material, and the current collector, and is usually added in an amount of 1 to 30% by weight based on the total weight of solids in the negative electrode slurry. Examples of such binders include polyvinylidene fluoride (PVDF), polyvinyl alcohol, carboxymethylcellulose (CMC), starch, hydroxypropylcellulose, regenerated cellulose, polyvinylpyrrolidone, and tetrafluoride. Roethylene, polyethylene, polypropylene, ethylene-propylene-diene polymer (EPDM), sulfonated-EPDM, styrene-butadiene rubber, fluorine rubber, and various copolymers thereof.

The conductive material is a component to further improve the conductivity of the negative electrode active material, and may be added in an amount of 1 to 20% by weight based on the total weight of solids in the negative electrode slurry. These conductive materials may be the same as or different from the conductive materials used in manufacturing the anode, for example, carbon black, acetylene black (or Denka black), Ketjen black, channel black, furnace black, lamp black, or thermal black. carbon powder, etc.; Graphite powder such as natural graphite, artificial graphite, or graphite with a highly developed crystal structure; Conductive fibers such as carbon fiber and metal fiber; Metal powders such as carbon fluoride, aluminum, and nickel powder; Conductive whiskers such as zinc oxide and potassium titanate; Conductive metal oxides such as titanium oxide; Conductive materials such as polyphenylene derivatives may be used.

The negative electrode active material slurry may further include a solvent. The solvent may include water or an organic solvent such as NMP or alcohol, and may be used in an amount that provides a desirable viscosity when including the negative electrode active material and optionally a binder and a conductive material. For example, the solid content concentration in the slurry containing the negative electrode active material and optionally the binder and the conductive material may be 50% by weight to 95% by weight, preferably 70% by weight to 90% by weight.

A lithium secondary battery comprising the positive and negative electrodes described above and the solid electrolyte according to the present invention maintains the electrochemical stability of the solid polymer electrolyte, but crystallization of the electrolyte is suppressed at low temperatures, so the output of the battery does not significantly decrease even at low temperatures, and has excellent It has the advantage of maintaining lithium ion mobility and excellent ion conductivity.

Below, the present invention will be described in more detail through specific examples. However, it does not mean that the scope of the present invention is limited to the scope of the examples, and the examples are merely specific application examples of the present invention to aid understanding, and those skilled in the art will be able to understand the scope of the present invention. It should be understood that the same technical idea can be implemented by changing, deleting, or adding configuration.

Synthesis Example 1. Synthesis of polythiourethane (PTU1)

A solution was prepared by dissolving 10 g of 2,2'-Thiodiethanethiol in 100 mL of DMSO (Dimethyl sulfoxide). While maintaining the solution at 70°C, 5 drops of dibutyltin dilaurate were added, and 1.03 equivalents of hexamethylene diisocyanate was slowly added dropwise while stirring to proceed with the reaction.

After adding all of the hexamethylene diisocyanate, the reaction was continued with stirring for 4 hours to obtain polythiourethane. The molecular weight of the obtained polythiourethane was 23,000 g/mol.

Synthesis Example 2. Synthesis of Polythiourethane (PTU2)

Polythiourethane (PTU2) was obtained by synthesis in the same manner as in Synthesis Example 1, except that 2,2'-(Ethylenedioxy)diethanethiol was used instead of 2,2'-Thiodiethanethiol in Synthesis Example 1. The weight average molecular weight of the polythiourethane obtained at this time was 18,000 g/mole.

Synthesis Example 3. Synthesis of polythiourethane (PTU3)

Polythiourethane (PTU3) was obtained by synthesizing in the same manner as in Synthesis Example 1, except that 1,3,4-Thiadiazole-2,5-dithiol was used instead of 2,2'-Thiodiethanethiol in Synthesis Example 1. The weight average molecular weight of the polythiourethane obtained at this time was 35,000 g/mole.

Synthesis Example 4. Synthesis of polythiourethane (PTU4)

Polythiourethane was obtained in the same manner as in Synthesis Example 1, except that isophorone diisocyante was used as diisocyanate instead of hexamethylene diisocyanate. The weight average molecular weight of the polythiourethane obtained at this time was 20,000 g/mole.

Synthesis Example 5. Synthesis of polythiourethane (PTU5)

Polythiourethane was obtained in the same manner as in Synthesis Example 2, except that methylene diphenyl diisocyanate was used instead of hexamethylene diisocyanate. The weight average molecular weight of the polythiourethane obtained at this time was 25,000 g/mole.

Example 1: Solid electrolyte production and coin cell production

Based on the weight of the thiourethane compound prepared in Synthesis Example 1, 3% by weight of Pentaerythritol tetrakis (3-mercaptopropionate) was stirred to be uniformly mixed with the thiourethane compound. Afterwards, LiTFSI was mixed with lithium salt at a weight ratio of polythiourethane/LiTFSI = 50/50, and the solid content in the solvent DMSO was adjusted to 10% to prepare a solid electrolyte composition.

The prepared solid electrolyte composition was applied on a polystyrene substrate, dried at 80°C for 1 hour, and then dried in a vacuum oven at 50°C for 1 hour to prepare a 100㎛ thick solid electrolyte film. This was peeled from the polystyrene substrate and laminated between two SUS (Steel Use Stainless) plates to produce a 2032 coin cell. Ion conductivity and electrochemical stability were measured using the manufactured coin cell as in Experimental Examples 1 and 2.

Example 2: Solid electrolyte production and coin cell production

Based on the weight of the thiourethane compound prepared in Synthesis Example 2, 5% by weight of Trimethylolpropane tris(3-mercaptopropionate) was stirred to be uniformly mixed with the thiourethane compound. Afterwards, LiTFSI was mixed with lithium salt at a weight ratio of polythiourethane/LiTFSI = 70/30, and the solid content in the solvent DMSO was adjusted to 10% to prepare a solid electrolyte composition.

The subsequent solid electrolyte film and coin cell were manufactured in the same manner as in Example 1, and ionic conductivity and electrochemical stability were measured as in Experimental Examples 1 and 2.

Example 3: Solid electrolyte production and coin cell production

Based on the weight of the thiourethane compound prepared in Synthesis Example 3, 5% by weight of Trimethylolpropane tris(3-mercaptopropionate) was stirred to uniformly mix with the thiourethane compound. Afterwards, LiTFSI was mixed with lithium salt at a weight ratio of polythiourethane/LiTFSI = 40/60, and the solid content in the solvent DMSO was adjusted to 10% to prepare a solid electrolyte composition.

The subsequent solid electrolyte film and coin cell were manufactured in the same manner as in Example 1, and ionic conductivity and electrochemical stability were measured as in Experimental Examples 1 and 2.

Example 4: Solid electrolyte production and coin cell production

Based on the weight of the thiourethane compound prepared in Synthesis Example 4, 5% by weight of Trimethylolpropane tris(3-mercaptopropionate) was stirred so that it was uniformly mixed with the thiourethane compound. Afterwards, LiTFSI was mixed with lithium salt at a weight ratio of polythiourethane/LiTFSI = 40/60, and the solid content in the solvent DMSO was adjusted to 10% to prepare a solid electrolyte composition.

The subsequent solid electrolyte film and coin cell were manufactured in the same manner as in Example 1, and ionic conductivity and electrochemical stability were measured as in Experimental Examples 1 and 2.

Example 5: Solid electrolyte production and coin cell production

Based on the weight of the thiourethane compound prepared in Synthesis Example 5, 5% by weight of Trimethylolpropane tris(3-mercaptopropionate) was stirred to uniformly mix with the thiourethane compound. Afterwards, LiTFSI was mixed with lithium salt at a weight ratio of polythiourethane/LiTFSI = 50/50, and the solid content in the solvent DMSO was adjusted to 10% to prepare a solid electrolyte composition.

The subsequent solid electrolyte film and coin cell were manufactured in the same manner as in Example 1, and ionic conductivity and electrochemical stability were measured as in Experimental Examples 1 and 2.

Example 6: Solid electrolyte production and coin cell production

Based on the weight of the thiourethane compound synthesized in Synthesis Example 2, 5% by weight of Trimethylolpropane tris(3-mercaptopropionate) was stirred to uniformly mix with the thiourethane compound. Afterwards, LiTFSI was used as a lithium salt and Succinonitrile as a plasticizer was mixed to a weight ratio of polythiourethane/LiTFSI/Succinonitrile = 40/30/30, and the solid content in the solvent DMSO was adjusted to 10% to prepare a solid electrolyte composition. did.

The subsequent solid electrolyte film and coin cell were manufactured in the same manner as in Example 1, and ionic conductivity and electrochemical stability were measured as in Experimental Examples 1 and 2.

Example 7: Solid electrolyte production and coin cell production

The thiourethane synthesized in Synthesis Example 2 and Synthesis Example 3 were stirred so that they were mixed at the same weight ratio. 5% by weight of Trimethylolpropane tris(3-mercaptopropionate) was added based on the total weight of the mixed thiourethane and stirred to mix. Afterwards, LiTFSI was mixed with lithium salt at a weight ratio of polythiourethane/LiTFSI = 70/30, and the solid content in the solvent DMSO was adjusted to 10% to prepare a solid electrolyte composition.

The subsequent solid electrolyte film and coin cell were manufactured in the same manner as in Example 1, and ionic conductivity and electrochemical stability were measured as in Experimental Examples 1 and 2.

Comparative Example 1: Manufacturing of lithium secondary battery

The monomer Poly(ethylene glycol) diacrylate (PEGDA, Mw: 700) with two functional groups, Trimethylolpropane ethoxylate triacrylate (ETPTA) as a crosslinker, LiTFSI as a lithium salt, and Succinonitrile (SN) as a plasticizer are used, and these are used as PEGDA/ETPTA/LiTFSi/ A coin cell was manufactured in the same manner as Example 1, except that it was mixed at a weight ratio of SN = 50/10/30/10.

Comparative Example 2: Manufacturing of lithium secondary battery

Polyethylene oxide (PEO, Mw: 10,000) is used as an ion conductive polymer, LiTFSI is used as a lithium salt, and Succinonitrile (SN) is used as a plasticizer, and the respective contents are mixed at a weight ratio of PEO/LiTFSI/SN = 20/30/50. It was dissolved and mixed in the solvent THF and casted on a glass plate. A solid electrolyte membrane was prepared by volatilizing the solvent at a temperature of 50°C. A coin cell for measuring ionic conductivity and a coin cell for measuring electrochemical stability were manufactured in the same manner as in Example 1.

Experimental Example 1: Measurement of ion conductivity

The ionic conductivity of the solid electrolyte can be obtained by measuring the impedance and using Equation 1 below. The coin cell for measuring ionic conductivity manufactured according to Examples and Comparative Examples was brought into contact with the substrate, and then an alternating current voltage was applied through electrodes on both sides of the sample. At this time, the measurement frequency was set to an amplitude range of 1.0 MHz to 0.1 Hz as the applied condition, and the impedance was measured using VMP3 from BioLogic. The resistance of the bulk electrolyte was calculated from the intersection where the semicircle or straight line of the measured impedance trace meets the real side, and the ionic conductivity of the solid electrolyte membrane was calculated from the area and thickness of the sample.

[Equation 1]

.

σ: Ion conductivity (S/cm)

R: Intersection between the impedance trace and the real axis

A: Area of solid polymer electrolyte membrane

t: Thickness of solid polymer electrolyte membrane

Experimental Example 2: Electrochemical stability measurement

To measure electrochemical stability, a coin cell was manufactured by using SUS as the measuring electrode and lithium metal as the counter electrode, inserting the manufactured electrolyte membrane between these electrodes, and linear scanning voltammetry up to 6V at a scan rate of 5mV/s ( Electrochemical measurements were made through Linear Sweep Voltammetry (LSV).

The ionic conductivity and electrochemical stability of the examples and comparative examples are summarized in Tables 1 and 2.

Mixing ratio (% by weight) Ion conductivity
(mS/cm) electrochemical
stability (v) polythiourethane lithium salt
(content)
plasticizer type content Example 1 PTU1 50wt% 50wt% - 0.3 4.5 Example 2 PTU2 70wt% 30wt% - 0.4 4.6 Example 3 PTU3 40wt% 60wt% - 0.1 4.6 Example 4 PTU4 40wt% 60wt% - 0.3 4.7 Example 5 PTU5 50wt% 50wt% - 0.4 4.6 Example 6 PTU2 40wt% 30wt% 30wt% 0.6 4.3 Example 7 PTU2/PTU3 70wt% 30wt% 0.4 4.5

Mixing ratio (% by weight) Ion conductivity
(mS/cm) electrochemical
stability (v) Ion conductive material crosslinking agent lithium salt plasticizer Comparative Example 1 PEGDA 50 wt% ETPTA 10wt% LiTFSI 30wt% SN 10wt% 0.04 4.2 Comparative Example 2 PEO 20wt% - LiTFSI 30wt% SN 50wtT 0.02 4.2

As shown in [Table 1], it can be seen that the polythiourethane-based solid electrolyte exhibits an ionic conductivity of 1 x 10 ^-4 S/cm or more. Due to the hydrogen bonding power of the thiourethane group, it is believed to have a strong bond with the anion of the lithium salt, making it easy for lithium ions to exist in a free ion state, showing high ionic conductivity. In addition, it can be seen that it has higher electrochemical stability by forming a cross-linked structure.

On the other hand, in the case of Comparative Examples 1 and 2 in [Table 2], segmental motion is hindered due to the strong crystallinity of the ethylene oxide group, and the lithium salt has a structure without a chemical characteristic group that facilitates dissociation, making it difficult for lithium ions to move. Therefore, it is judged to have low ionic conductivity.

Considering the above results, it can be confirmed that the solid electrolyte formed from the solid electrolyte composition containing a thiourethane compound and a cross-linking agent according to the present invention has very excellent ionic conductivity compared to the comparative example using a conventionally used PEO polymer. It can be seen that electrochemical stability is also higher than that of conventional solid electrolytes.

Although the embodiments of the present invention have been described in detail above, the present invention is not limited by the above-described embodiments and the attached drawings, but is intended to be limited by the appended claims. Accordingly, various forms of substitution, modification, and change may be made by those skilled in the art without departing from the technical spirit of the present invention as set forth in the claims, and this also falls within the scope of the present invention. something to do.

Claims (15)

A thiourethane compound represented by the following formula (1);
lithium salt; and
A solid electrolyte composition comprising a crosslinking agent containing two or more thiol groups:
[Formula 1]

_{In Formula 1 , ​ ​} It is one of an alkylene group, a substituted or unsubstituted C ₃ -C ₁₆ cycloalkylene group, and a substituted or unsubstituted C ₆ -C ₁₆ arylene group, and n is a natural number in the range of 10 to 1000.
According to paragraph 1,
The X above is , , and At least one solid electrolyte composition selected from the group consisting of.
According to paragraph 1,
The above A is , , , , and At least one solid electrolyte composition selected from the group consisting of.
According to paragraph 1,
The cross-linking agent is , , , , , and A solid electrolyte composition comprising at least one selected from the group consisting of.
According to paragraph 1,
The solid electrolyte composition wherein the crosslinking agent is contained in the range of 1% to 30% by weight based on the content of the thiourethane compound.
According to paragraph 1,
A solid electrolyte composition wherein the lithium salt is contained within the range of 10% by weight to 70% by weight based on the total composition.
According to paragraph 1,
A solid electrolyte composition further comprising a plasticizer.
According to paragraph 1,
It further includes a thiourethane compound represented by the following formula (2),
X' in Formula 2 below is different from X in Formula 1, A' in Formula 2 below is different from A in Formula 1, or X' in Formula 2 below is different from A solid electrolyte composition wherein A' is different from A of Formula 1:
[Formula 2]

_{In Formula 2 , ​} It is one of a C ₁₂ alkylene group, a substituted or unsubstituted C ₃ -C ₁₆ cycloalkylene group, and a substituted or unsubstituted C ₆ -C ₁₆ arylene group, and m is a natural number in the range of 10 to 1000.
According to clause 8,
The X' is , , and At least one solid electrolyte composition selected from the group consisting of.
According to clause 8,
The A' is , , , , and At least one solid electrolyte composition selected from the group consisting of.
According to clause 8,
A solid electrolyte composition containing the compound represented by Formula 2 in an amount of 1% by weight or more and 50% by weight or less based on the total composition.
A solid electrolyte comprising a unit derived from the solid electrolyte composition of claim 1.
According to clause 12,
The unit derived from the solid electrolyte composition of claim 1 is a solid electrolyte comprising a crosslinking of a thiourethane compound and a crosslinking agent containing two or more thiol groups.
According to clause 13,
The solid electrolyte wherein the crosslinking is dynamic crosslinking.
A lithium secondary battery comprising a solid electrolyte, a positive electrode, and a negative electrode according to any one of claims 12 to 14.