Ionic organic framework electrolyte for all-solid-state secondary battery, comprising multiple components, preparation method therefor, and all-solid-state secondary battery comprising same

Abstract

Provided is an ionic organic framework electrolyte for an all-solid-state secondary battery, the ionic organic framework electrolyte for an all-solid-state secondary battery comprising: a crystalline organic framework having pores; and a glycol-based compound bonded to the organic framework, wherein the glycol-based compound is covalently bonded to the crystalline organic framework.

Description

Ionic organic framework electrolyte for all-solid-state secondary batteries containing multiple components, method for producing the same, and all-solid-state secondary batteries containing the same

[0001] The present invention relates to an ionic organic framework electrolyte for an all-solid-state secondary battery comprising multiple components, a method for producing the same, and an all-solid-state secondary battery comprising the same. More specifically, the present invention relates to an ionic organic framework electrolyte for an all-solid-state secondary battery comprising multiple components, which has a very simple synthesis process and a high synthesis yield, exhibits very high ionic conductivity and lithium ion transport number at room temperature, and has very excellent thermal / electrochemical stability, a method for producing the same, and an all-solid-state secondary battery comprising the same.

[0002] The lithium-ion secondary batteries currently in use have a very high risk of fire and explosion due to the use of liquid electrolytes, and the development of high-voltage / high-energy-density lithium-ion batteries is impossible due to the low thermal / electrochemical stability of the liquid electrolytes.

[0003] Therefore, to solve these limitations, the development of all-solid-state lithium secondary batteries is actively underway, and to realize this, the development of a solid electrolyte with excellent ionic conductivity and electrochemical stability is essential. However, the existing inorganic solid electrolytes are very difficult to manufacture and process, have poor contact with the electrode surface, resulting in very high contact resistance, and have limitations such as low electrochemical stability.

[0004] To overcome the shortcomings of such inorganic solid electrolytes, organic solid electrolytes based on amorphous polymers are being developed. However, they still have problems such as low room-temperature ionic conductivity, thermal / electrochemical instability, and low lithium ion transport number, which leads to side reactions such as dendrites and uneven SEI layer formation, resulting in very poor charge-discharge stability, making practical application difficult.

[0005] The technical problem to be achieved by the present invention is to provide an electrolyte for an all-solid-state secondary battery, which exhibits very high ionic conductivity and lithium ion transport number at room temperature and has excellent thermal / electrochemical stability, and a method for manufacturing the same.

[0006] In order to solve the above problem, the present invention provides an ionic organic framework electrolyte for an all-solid-state secondary battery, comprising: a crystalline organic framework having pores; and a glycol-based compound bonded to the organic framework, wherein the glycol-based compound is covalently bonded to the crystalline organic framework.

[0007] In one embodiment of the present invention, the crystalline organic framework having the pores includes a plurality of pyridium ions as a basic component of the organic framework.

[0008] In one embodiment of the present invention, the glycol compound is diethylene glycol (DEG), and the diethylene glycol (DEG) is covalently bonded to the pyridinic N site nitrogen of the pyridium.

[0009] In one embodiment of the present invention, the movement of metal ions in the ionic organic framework electrolyte for the all-solid-state secondary battery includes movement (hopping behavior) of the metal ions at the oxygen site of the diethylene glycol (DEG).

[0010] In one embodiment of the present invention, the movement of metal ions in the ionic organic framework electrolyte for the all-solid-state secondary battery includes the movement (vehicle behavior) of the diethylene glycol (DEG) itself.

[0011] In one embodiment of the present invention, the ionic organic framework electrolyte for the all-solid-state secondary battery further comprises ionic succinonitrile.

[0012] In one embodiment of the present invention, the crystalline organic framework having the pores comprises at least one of the following structural formulas.

[0013] (1)

[0014] (2)

[0015] In one embodiment of the present invention, the ionic organic framework electrolyte for the all-solid-state secondary battery further comprises lithium bis(trifluoromethanesulfonyl)imide.

[0016] The present invention also provides an all-solid-state secondary battery comprising the above-described ionic organic framework electrolyte for an all-solid-state secondary battery.

[0017] In one embodiment of the present invention, the all-solid-state secondary battery is a lithium all-solid-state secondary battery.

[0018] The present invention also provides a method for producing an ionic organic framework electrolyte for an all-solid-state secondary battery, comprising the steps of: producing a crystalline organic framework having pores; and binding a glycol-based compound to the organic framework, wherein the glycol-based compound is covalently bonded to the crystalline organic framework.

[0019] In one embodiment of the present invention, the step of preparing the crystalline organic skeleton includes the step of reacting triformylbenzene and a pyridine compound, wherein the glycol compound is diethylene glycol (DEG).

[0020] In one embodiment of the present invention, the diethylene glycol (DEG) covalently bonds with the pyridinic N site nitrogen of pyridium in the organic skeleton.

[0021] The electrolyte according to the present invention has a structure of a solid electrolyte based on a so-called multicomponent covalent organic framework, in which a “cation functional group” that enables effective dissociation of lithium ions and a “flexible diethylene glycol (DEG)” and an “ionic liquid (succinonitrile)” that can promote lithium ion diffusion by pressing / vehicle / free diffusion are all covalently bonded to a crystalline covalent organic framework (COF) having a porous structure that allows rapid lithium ion diffusion. This provides the advantages of a very simple synthesis process and a high synthesis yield, as well as very high ionic conductivity and lithium ion transport number at room temperature, and excellent thermal / electrochemical stability. In addition, an all-solid-state lithium metal secondary battery manufactured using the electrolyte (MC-PCOF) solid electrolyte according to the present invention has excellent cycling performance and high energy density.

[0022] Figures 1 and 2 are schematic diagrams of the process and structure for producing a covalently bonded organic skeleton with multiple components introduced according to one embodiment of the present invention.

[0023] Figures 3 to 6 are the results of physical structure analysis of a covalently bonded organic skeleton into which a multicomponent is introduced according to one embodiment of the present invention.

[0024] Figures 7 to 9 show the results of chemical structure analysis of a covalently bonded organic skeleton into which a multicomponent is introduced.

[0025] Figures 10 to 16 show the electrochemical characteristics and ionic conductivity analysis results of MC-PCOF-A based solid electrolytes.

[0026] Figures 17 and 18 are the analysis results confirming the lithium ion transport method of the MC-PCOF-A-based all-solid-state electrolyte through molecular dynamics simulation. In Figure 18, the mechanism of lithium ion diffusion through the distance between oxygen and lithium ions over time (ac) was confirmed.

[0027] Figures 19 to 23 are the results of performance analysis of an all-solid-state lithium metal battery using an all-solid-state electrolyte based on MC-PCOF-A. Figure 19 shows the structure of an assembled all-solid-state lithium metal battery. Figure 20 shows the results of checking the change in charge / discharge capacity according to the number of cycles. Figure 21 shows the results of checking the cycle stability at room temperature. Figure 22 shows the results of checking the capacity and coulombic efficiency stability at various charge / discharge rates. Figure 23 shows the results of checking the change in capacity at various charge / discharge rates.

[0028] The present invention is susceptible to various modifications and embodiments. Specific embodiments are illustrated in the drawings and described in detail in the following detailed description. However, this is not intended to limit the present invention to specific embodiments, but rather to encompass all modifications, equivalents, and alternatives falling within the spirit and technical scope of the present invention. In describing the present invention, detailed descriptions of related known technologies will be omitted if they are deemed to obscure the gist of the present invention.

[0029]

[0030] In order to solve the above-described problem, the present invention introduces a glycol compound such as DEG into a crystalline covalent organic framework (COF) having a porous structure, thereby exhibiting very high ionic conductivity and lithium ion transport capacity at room temperature and having excellent thermal / electrochemical stability, which will be described in more detail below.

[0031]

[0032] The solid electrolyte according to the present invention is manufactured by first synthesizing a crystalline organic skeleton containing a pyridine compound as a basic component by reacting a pyridine compound with triformylbenzene, and then 2) covalently bonding a glycol compound to the nitrogen (pyridium) of the pyridine compound. Therefore, various types of solid electrolytes can be manufactured depending on the structure of the pyridine compound, and examples of two types of synthesis are described below, but the scope of the present invention is not limited thereto.

[0033] Synthesis of PCOF-A

[0034] 1. 1,3,5-Triformylbenzene and 2,6-diaminopyridine were dissolved in a mixture of mesitylene and 1,4-dioxane solution (1:1 v / v) in a three-necked round-bottom flask under an argon atmosphere.

[0035] 2. The above mixture was sonicated for 10 minutes and acetic acid (6 M) was added to the reaction mixture at room temperature.

[0036] 3. The reaction was carried out at 120 oC for 72 hours.

[0037] 4. The solution was centrifuged at 12,000 rpm to obtain the resulting porous organic framework (PCOF), and the obtained PCOF was washed three times with tetrahydrofuran.

[0038] 5. PCOF was dispersed in NMP (N-methyl-2-pyrrolidone) and then neutralized by adding NaOH aqueous solution (pH 8.0).

[0039] 6. After stirring the solution for 10 minutes, centrifugation was performed at 12,000 rpm for 10 minutes to obtain neutralized PCOF, which was washed three times with water and acetone, respectively.

[0040] 7. The collected powder was dried in high vacuum for 12 hours.

[0041]

[0042] Synthesis of PCOF-B

[0043] 1. 1,3,5-Triformylbenzene and 2,2-bipyridine-5,5-diamine were dissolved in a mixture of mesitylene and 1,4-dioxane solution (9:1 v / v) in a three-necked round-bottom flask under an argon atmosphere.

[0044] 2. The above mixture was sonicated for 10 minutes and acetic acid (4 M) was added to the reaction mixture at room temperature.

[0045] 3. The reaction was carried out at 80 oC for 72 hours.

[0046] 4. The solution was centrifuged at 12,000 rpm to obtain the resulting porous organic framework (PCOF), and the obtained PCOF was washed three times with tetrahydrofuran.

[0047] 5. PCOF was dispersed in NMP (N-methyl-2-pyrrolidone) and then neutralized by adding NaOH aqueous solution (pH 8.0).

[0048] 6. After stirring the solution for 10 minutes, centrifugation was performed at 12,000 rpm for 10 minutes to obtain neutralized PCOF, which was washed three times with water and acetone, respectively.

[0049] 7. The collected powder was dried in high vacuum for 12 hours.

[0050]

[0051] Synthesis of multicomponent porous organic frameworks (MC-PCOFs) and fabrication of all-solid-state electrolytes

[0052] 1. PCOF-A and PCOF-B obtained above were dispersed in NMP in a three-necked round-bottom flask under an argon atmosphere and then sonicated for 10 minutes.

[0053] 2. Diethylene glycol 2-bromoethyl methyl ether was added to the above PCOF solution, and the resulting mixture was stirred at 120 oC for 24 hours.

[0054] 3. After cooling the reaction solution, an excess of ethyl acetate was added to precipitate the desired product.

[0055] 4. The product MC-PCOF was obtained by centrifugation at 12,000 rpm for 10 minutes and washed three times with ethyl acetate.

[0056] 5. The dried MC-PCOF was mixed with succinonitrile, lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), and PVDF, and NMP was added to make it into a pellet form. The pellet was then dried at 80 degrees Celsius for 24 hours to produce an all-solid-state electrolyte.

[0057]

[0058] Figures 1 and 2 are schematic diagrams of the process and structure for producing a covalently bonded organic skeleton with multiple components introduced according to one embodiment of the present invention.

[0059] Referring to Figures 1 and 2, it can be seen that upon treatment with diethylene glycol 2-bromoethyl methyl ether, pure pyridine-rich COF (PCOF) is converted to MC-PCOF in the form of DEG-modified pyridium. DEG is predominantly introduced into the pyridinic N site of PCOF rather than the anilinic N site, due to the much higher nucleophilicity of the pyridinic N (see Figure 2).

[0060] The MC-PCOF, which is the basic structure of the multi-component introduced organic framework (MC-PCOF) according to one embodiment of the present invention, is designed to easily dissociate Li salts and provide multiple pathways for rapid lithium ion transport in the all-solid-state LMB. That is, the introduction of DEG into the organic framework in the present invention provides the advantages of high room temperature ionic conductivity (σ = 1.71 × 10-4 Scm-1), room temperature lithium ion transfer number (tLi+ = 0.61), and a wide electrochemical stability range, and the pyridium component of MC-PCOF has high polarity and electrochemical stability, thereby promoting the dissociation of a lithium ion pair into two mobile ionic species.

[0061] In addition, in one embodiment of the present invention, diethylene glycol (DEG), which is one of the multi-components introduced into the covalent organic framework electrolyte having a rigid crystalline skeleton and rich in pyridine, has flexible and polar characteristics and can effectively transport Li ions through hopping and vehicle movement in the solid electrolyte.

[0062] Furthermore, the succinonitrile component introduced into the MC-PCOF pore channels promotes additional lithium ion diffusion in all-solid-state batteries. To demonstrate this, density functional theory (DFT) and molecular dynamics (MD) simulations were performed, confirming an effective lithium ion dissociation mechanism and demonstrating long-term cycling performance.

[0063]

[0064] Experimental example

[0065] Figures 3 to 6 are the results of physical structure analysis of a covalently bonded organic skeleton into which a multicomponent is introduced according to one embodiment of the present invention.

[0066] In Fig. 3, (ab) is a TEM image of PCOF-A, (cd) is a TEM image of MC-PCOF-A, Fig. 4 is the XRD analysis result of PCOF-A, Fig. 5 is the pore size distribution by BET analysis, and Fig. 6 is the analysis result regarding the laminated structure of PCOF-A and MC-PCOF-A.

[0067] Referring to FIGS. 3 to 6, it can be seen that the multi-component organic skeleton still maintains pore size and crystallinity with the introduction of DEG.

[0068] Figures 7 to 9 are chemical structure analysis results of covalently bonded organic skeletons with multicomponents introduced. In Figure 7, (ab) XPS analysis of PCOF-A and (cd) XPS analysis results of MC-PCOF-A.

[0069] Also, Fig. 8 shows the 13C-NMR analysis results of MC-PCOF-A, and Fig. 9 shows the FT-IR analysis results of PCOF and MC-PCOF-A.

[0070] Referring to FIGS. 7 to 9, it can be seen that the solid electrolyte according to the present invention maintains its structure identical / similar to that before introduction even after introduction of DEG.

[0071]

[0072] Figures 10 to 16 show the electrochemical characteristics and ionic conductivity analysis results of MC-PCOF-A-based solid electrolytes. Figure 10 shows the ionic conductivity at room temperature using a Nyquist plot, Figure 11 shows the ionic conductivity stability at 450 K, Figure 12 shows the ionic conductivity depending on temperature using an Arrhenius plot, Figure 13 shows the lithium ion transport number confirmed through chronoamperometry analysis of a Li|MC-PCOF-A|Li symmetric cell at room temperature, Figure 14 shows the oxidation stability confirmed through oxidation potential analysis, Figure 15 shows the lithium ion attachment and detachment stability confirmed, and Figure 16 shows an SEM image of the electrode interface after 100 cycles.

[0073] Referring to FIGS. 10 to 16, it can be seen that the solid electrolyte according to the present invention has higher performance (ionic conductivity, lithium ion transport number, oxidation stability, dendrite inhibition) than the existing polymer electrolyte. In particular, it can be confirmed from the above results that the introduction of the organic framework of DEG results in high room temperature ionic conductivity (σ = 1.71 × 10-4 Scm-1) and room temperature lithium ion transfer number (tLi+ = 0.61).

[0074] Figures 17 and 18 are the analysis results confirming the lithium ion transport method of the MC-PCOF-A-based all-solid-state electrolyte through molecular dynamics simulation. In Figure 18, the mechanism of lithium ion diffusion through the distance between oxygen and lithium ions over time (ac) was confirmed.

[0075] Referring to Figures 17 and 18, lithium ion diffusion in the solid electrolyte (MC-PCOF) according to the present invention occurs through three modes: hopping, vehicle, and free diffusion behaviors. MD simulations show that the diffusion behavior of Li ions can be classified as follows depending on their interaction with the DEG chain.

[0076]

[0077] 1. Hopping behavior

[0078] Referring to Fig. 5 (a), which analyzes the average distance of O-Li by time, the behavior of dissociated lithium ions hopping between oxygen sites of adjacent DEG chains, lithium ions adjacent to chain 1 jump to neighboring chain 2, and occasionally move completely in about 375 ps, maintaining the average distance.

[0079] 2. Vehicle behavior

[0080] Additionally, during this hopping motion, a single DEG chain can move lithium ions from a neighboring chain through a behavior similar to vehicle movement (vehicle behavior), as shown in Fig. 5b.

[0081] 3. Free diffusion behavior

[0082] Due to the limited chain length of the DEG group, the diffusion range is limited to vehicle behavior such as car behavior, and thus, in the final stage, lithium ions move in a free diffusion behavior as shown in (c) of Fig. 5.

[0083]

[0084] Therefore, in the case where there is no introduction of DEG according to the present invention, lithium will move according to free diffusion behavior, but the DEG according to the present invention provides additional movement behaviors such as 1) lithium ion movement between oxygen sites of DEG and 2) lithium ion movement through movement of the DEG chain itself.

[0085] Therefore, it can be confirmed that the solid electrolyte according to the present invention moves lithium ions through a diffusion mechanism, and this is believed to be the effect of a glycol compound introduced in the form of a covalent bond to the pyridium-rich organic skeleton.

[0086] Figures 19 to 23 are the results of performance analysis of an all-solid-state lithium metal battery using an all-solid-state electrolyte based on MC-PCOF-A. Figure 19 shows the structure of an assembled all-solid-state lithium metal battery. Figure 20 shows the results of checking the change in charge / discharge capacity according to the number of cycles. Figure 21 shows the results of checking the cycle stability at room temperature. Figure 22 shows the results of checking the capacity and coulombic efficiency stability at various charge / discharge rates. Figure 23 shows the results of checking the change in capacity at various charge / discharge rates.

[0087] Referring to FIGS. 19 to 23, it can be seen that the solid electrolyte according to the present invention has excellent cycle stability and charge / discharge efficiency.

[0088] While specific aspects of the present invention have been described in detail above, it will be apparent to those skilled in the art that these specific descriptions merely represent preferred embodiments and are not intended to limit the scope of the present invention. Therefore, the substantial scope of the present invention is defined by the appended claims and their equivalents.

[0089] The present invention relates to a solid electrolyte (MC-PCOF), which can be applied to an all-solid-state lithium metal secondary battery, and thus has industrial applicability.

Claims

1. Ionic organic framework electrolyte for all-solid-state secondary batteries, A crystalline organic framework having pores; An ionic organic framework electrolyte for an all-solid-state secondary battery, comprising a glycol compound bonded to the organic framework, wherein the glycol compound is covalently bonded to the crystalline organic framework.

2. In paragraph 1, An ionic organic framework electrolyte for an all-solid-state secondary battery, characterized in that the crystalline organic framework having the above pores comprises a plurality of pyridium ions as basic components of the organic framework.

3. In paragraph 1, An ionic organic framework electrolyte for an all-solid-state secondary battery, characterized in that the glycol compound is diethylene glycol (DEG).

4. In paragraph 1, An ionic organic framework electrolyte for an all-solid-state secondary battery, characterized in that the above diethylene glycol (DEG) is covalently bonded to the pyridinic N site nitrogen of the above pyridium.

5. In paragraph 4, An ionic organic framework electrolyte for an all-solid-state secondary battery, characterized in that the movement of metal ions in the ionic organic framework electrolyte for an all-solid-state secondary battery includes movement (hopping behavior) of the metal ions at the oxygen site of the diethylene glycol (DEG).

6. In paragraph 4, An ionic organic framework electrolyte for an all-solid-state secondary battery, characterized in that the movement of metal ions in the ionic organic framework electrolyte for an all-solid-state secondary battery includes the movement (vehicle behavior) of diethylene glycol (DEG) itself.

7. In paragraph 6, The above-mentioned all-solid-state secondary battery ionic organic framework electrolyte is characterized in that it further contains ionic succinonitrile.

8. In paragraph 7, An ionic organic framework electrolyte for an all-solid-state secondary battery, characterized in that the crystalline organic framework having the above pores comprises at least one of the following structural formulas. (1) (2) 9. In paragraph 6, An ionic organic framework electrolyte for an all-solid-state secondary battery, characterized in that the above-mentioned ionic organic framework electrolyte further comprises lithium bis(trifluoromethanesulfonyl)imide.

10. An all-solid-state secondary battery comprising an ionic organic framework electrolyte according to any one of claims 1 to 9.

11. In paragraph 10, An all-solid-state secondary battery, characterized in that the above all-solid-state secondary battery is a lithium all-solid-state secondary battery.

12. A method for manufacturing an ionic organic framework electrolyte for an all-solid-state secondary battery, A step of manufacturing a crystalline organic framework having pores; and A method for producing an ionic organic framework electrolyte for an all-solid-state secondary battery, comprising a step of bonding a glycol-based compound to the organic framework, wherein the glycol-based compound is covalently bonded to the crystalline organic framework.

13. In paragraph 12, A method for producing an ionic organic framework electrolyte for an all-solid-state secondary battery, characterized in that the step of producing the above-mentioned crystalline organic framework includes a step of reacting triformylbenzene and a pyridine compound.

14. In paragraph 13, A method for manufacturing an ionic organic framework electrolyte for an all-solid-state secondary battery, characterized in that the glycol compound is diethylene glycol (DEG).

15. In paragraph 14, A method for producing an ionic organic framework electrolyte for an all-solid-state secondary battery, characterized in that the above diethylene glycol (DEG) is covalently bonded with the pyridinic N site nitrogen of pyridium in the organic framework.

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