KR102610969B1 - Method for designing of sulfide-based solid electrolyte using computer simulations and all-solid-state battery containing solid electrolyte designed thereby - Google Patents

Abstract

The present invention relates to a design method of a sulfide-based solid electrolyte using computer simulation and an all-solid-state battery containing a sulfide-based solid electrolyte designed thereby. According to the present invention, the development period of a sulfide-based solid electrolyte is shortened by using computer simulation. This can increase commercial feasibility, and by performing computer simulations using the phase under an electric field rather than the stationary phase, results consistent with actual sulfide-based solid electrolytes can be obtained.

Description

Method for designing of sulfide-based solid electrolyte using computer simulations and all-solid-state battery containing solid electrolyte designed thereby }

The present invention relates to a design method for a sulfide-based solid electrolyte using computational simulation and an all-solid-state battery containing a sulfide-based solid electrolyte designed thereby. Specifically, the present invention relates to a method for designing a sulfide-based solid electrolyte using computerized simulation and to an all-solid-state battery including a sulfide-based solid electrolyte designed using the same. This relates to a method of designing a sulfide-based solid electrolyte with improved ionic conductivity.

Secondary batteries that can be charged and discharged are used not only in small electronic devices such as mobile phones and laptops, but also in large transportation vehicles such as hybrid cars and electric cars. Most existing secondary batteries are based on organic liquid electrolytes, showing limitations in improving stability and energy density.

Meanwhile, all-solid-state batteries using solid electrolytes have recently been in the spotlight because they do not use organic solvents and can be constructed in a safer and simpler form.

Inorganic solid electrolytes are divided into oxide-based and sulfide-based. Sulfide-based solid electrolytes have higher lithium ion conductivity and excellent ductility compared to oxide-based solid electrolytes, making them easier to process, so they have the advantage of being applicable to a variety of purposes. There is.

In general, there are two methods to improve the ionic conductivity of sulfide-based solid electrolytes. The first is to improve the diffusion of lithium ions by controlling the crystal structure, and the second is to improve the diffusion of lithium ions by doping other atoms in the crystal structure. In the case of some sulfide-based solid electrolytes, it has been reported that the ionic conductivity of the solid electrolyte increases by 2 to 100 times using a doping method.

Existing experiment-based research to produce the sulfide-based solid electrolyte as described above has the problem of requiring several years of development time by repeatedly performing experiments and analysis.

Accordingly, there is a demand for the development of technology to shorten the development period by utilizing computer simulation in developing sulfide-based solid electrolytes.

patent literature

Korean Patent No. 10-0918387 (2009.09.15)

The problem to be solved by the present invention is a method of designing a sulfide-based solid electrolyte with excellent ionic conductivity by simulating and analyzing structural changes due to doping of a sulfide-based solid electrolyte using computational simulation, and a sulfide-based solid electrolyte designed thereby. To provide an all-solid-state battery containing.

The present invention includes a structural modeling step of modeling the molecular structure of a sulfide-based solid electrolyte based on information registered in a database;

A charge distribution change modeling step of calculating and modeling the charge density distribution of the sulfide-based solid electrolyte;

A displacement calculation step of calculating the displacement of at least one atom included in the molecular structure of the sulfide-based solid electrolyte that has undergone the charge distribution change modeling step; and

A design method for a sulfide-based solid electrolyte using computational simulation including an ionic conductivity prediction step of calculating ionic conductivity using the calculated atomic displacement is provided.

In addition, an all-solid-state battery containing a sulfide-based solid electrolyte designed by the above-described sulfide-based solid electrolyte design method is provided.

The present invention relates to a method of designing a sulfide-based solid electrolyte doped with halogen atoms having high ionic conductivity using computer simulation. By using computer simulation, the development period of the sulfide-based solid electrolyte can be shortened and its commercial potential can be increased.

In addition, the design method of a sulfide-based solid electrolyte using computational simulation according to the present invention can obtain results that correspond to an actual sulfide-based solid electrolyte by performing computer simulation using a phase under an electric field rather than a stationary phase.

Figure 1 is a flowchart showing an analysis method of a sulfide-based solid electrolyte using computer simulation according to an embodiment of the present invention.
Figures 2 to 4 are images modeling the structure of a sulfide-based solid electrolyte in the structural modeling step of the analysis method of a sulfide-based solid electrolyte using computer simulation according to an embodiment of the present invention.
Figures 5 to 7 are images modeled by calculating the charge density distribution of the sulfide-based solid electrolyte in the charge distribution change modeling step of the analysis method of the sulfide-based solid electrolyte using computer simulation according to an embodiment of the present invention.
Figures 8 to 10 are images modeled by calculating the diffusion path width of the sulfide-based solid electrolyte in the diffusion path calculation step of the analysis method of the sulfide-based solid electrolyte using transfer simulation according to an embodiment of the present invention.
Figure 11 is a graph showing the diffusion path width of the sulfide-based solid electrolyte calculated for each doping atom in the diffusion path calculation step of the analysis method of the sulfide-based solid electrolyte using transfer simulation according to an embodiment of the present invention.
Figure 12 is a graph showing the calculated amplitude of the mean square displacement of lithium and sulfur of the sulfide-based solid electrolyte in the charge distribution change modeling step of the analysis method of the sulfide-based solid electrolyte using computer simulation according to an embodiment of the present invention.
Figure 13 is a graph showing the diffusion coefficient of the sulfide-based solid electrolyte in the ionic conductivity prediction step of the analysis method of the sulfide-based solid electrolyte using transfer simulation according to an embodiment of the present invention.

Hereinafter, in order to explain the present invention in more detail, preferred embodiments according to the present invention will be described in more detail with reference to the attached drawings. However, the present invention is not limited to the embodiments described herein and may be embodied in other forms.

Most studies have interpreted that doping atoms simply widen the diffusion path and accelerate the diffusion of lithium, thereby increasing ionic conductivity. However, in reality, the difference between the atomic diameters of sulfur (S) and chlorine (Cl) is not significant, so there is a limit to the interpretation that doping with chlorine (Cl) expands the width of the diffusion path.

In addition, the distribution of diffusion channels was calculated on average to have a width between 0.6 and 0.8 Å, but the diameter of lithium ions is larger at 1.52 Å. Therefore, the interpretation that the diffusion path is expanded by simply using a dopant in the stationary phase is contradictory.

As shown in Figure 1, the present invention is a sulfide-based solid electrolyte using computational simulation including a structure modeling step (S100), a charge distribution change modeling step (S200), a displacement calculation step (S300), and an ionic conductivity prediction step (S400). A design method and an all-solid-state battery including a sulfide-based solid electrolyte designed thereby are provided.

In addition, the design method of the sulfide-based solid electrolyte according to the present invention may further include a diffusion path calculation step (S220) between the charge distribution change modeling step (S200) and the displacement calculation step (S300).

The design method of a sulfide-based solid electrolyte using computer simulation according to the present invention selects materials and dopants that can widen the diffusion path of ions in the solid electrolyte by reducing the structural stability of the sulfide-based solid electrolyte compound through computer simulation. This relates to a method of designing a sulfide-based solid electrolyte with high ionic conductivity.

Conventionally, by simply adding a dopant, a dopant, such as chlorine (Cl), is substituted in place of S in the tetrahedral structure, and the effect of increasing ionic conductivity by the dopant is achieved with the view that the dopant thereby widens the width of the diffusion path for lithium ions. It has been explained. On the other hand, the radius of the sulfur atom is approximately 1.81 Å, and the radius of the chlorine atom is approximately 1.84 Å, which are similar in size and do not differ significantly even before substitution. In addition, as a result of calculating the distribution of diffusion paths on average for LGPS (Li ₁₀ GeP ₂ S ₁₂ ), a sulfide-based solid electrolyte for all-solid-state lithium secondary batteries, and sulfide-based solid electrolyte doped with chlorine atoms in LGPS, both were similar, 0.6~ It was confirmed to have a width of between 0.8Å, which means that the diameter of the lithium ion is also smaller than 1.52Å.

That is, the reason for the increase in ionic conductivity due to the addition of dopants in the conventional sulfide-based solid electrolyte was that there were limits to appropriate analysis of the increase in structural width or diffusion path width due to the dopant.

On the other hand, the design method of the sulfide-based solid electrolyte using computational simulation according to the embodiment of the present invention is not a simple method like the conventional analysis, but rather uses the following computerized simulation to determine the diffusion path of lithium ions in the actual sulfide-based solid electrolyte. It is possible to determine whether the width of is increasing. Therefore, by proposing a chemical formula with high ionic conductivity for the sulfide-based solid electrolyte applied to the all-solid lithium secondary battery, the electrochemical properties and lifespan characteristics of the all-solid lithium secondary battery can be improved.

Specifically, the design method of the sulfide-based solid electrolyte using computer simulation according to the present invention can be obtained by reflecting the vibration of atoms in the compound rather than the stationary phase of the compound used as the sulfide-based solid electrolyte. there is. Specifically, when an electric field is applied to a compound used as a sulfide-based solid electrolyte, phase distortion of the compound with a tetrahedral structure occurs, resulting in a change in charge distribution and increased vibration, thereby reducing the structural stability of the compound. It was confirmed through experiments that the diffusion path of lithium ions can be expanded and the mobility of lithium ions can be improved. Based on this, a design method for a sulfide-based solid electrolyte using computer simulation is provided.

The structural modeling step (S100) is a step of modeling the molecular structure of the sulfide-based solid electrolyte based on information registered in the database. For example, in the structural modeling step (S100), when information (hereinafter referred to as chemical formula) of the compound constituting the sulfide-based solid electrolyte, such as chemical formula or structural formula, is input, the sulfide-based solid electrolyte according to the chemical formula entered through the database The molecular structure of can be modeled.

Typically, the sulfide-based solid electrolyte is mainly used as an electrolyte in all-solid-state lithium secondary batteries. The sulfide-based solid electrolyte is a solid state made by mixing powder and additives and compressed into a pellet form, and is a liquid state made of existing organic compounds. Although safety was improved compared to electrolytes, there was a problem that the mobility of lithium ions was low.

On the other hand, the design method of the sulfide-based solid electrolyte using computer simulation according to this embodiment provides numerical values for the actual lithium ion movement path that can be obtained by reflecting atomic vibrations depending on the type of compound of the sulfide-based solid electrolyte. can be provided. Therefore, it is possible to provide a design method for a sulfide-based solid electrolyte with improved mobility of lithium ions in an all-solid lithium secondary battery, thereby improving the lifespan characteristics and electrochemical properties of the all-solid lithium secondary battery.

More specifically, the structural modeling step (S100) can model the molecular structure of the sulfide-based solid electrolyte of the following Chemical Formula 1 or Chemical Formula 2 using the Quantum Espresso program based on first principles calculation:

[Formula 1]

Li _a P _c S _d X _e

[Formula 2]

Li _a M _b P _c S _d X _e

In Formula 1 or Formula 2,

X is at least one of fluorine (F), chlorine (Cl), bromine (Br), iodine (I), selenium (Se), and tellurium (Te),

M is silicon (Si), germanium (Ge), tin (Sn), or lead (Pb),

7≤a≤12, 1≤b≤2, 1≤c≤3, 10≤d≤12, 0<e≤2.

Specifically, in Formula 1 or Formula 2, ), germanium (Ge), tin (Sn), or lead (Pb), and 9≤a≤12, 1≤b≤2, 1≤c≤2, 10≤d≤12, 0<e≤2. More specifically, in Formula 1, a is 7, c is 3, d is 10, and e is 1, and in Formula 2, a may be 10, b may be 1.5, c may be 1.5, d may be 11.5, and e may be 0.5. .

Additionally, in the sulfide-based solid electrolyte of Formula 1 or Formula 2, X may be bromine (Br). For example, when You can. The width of the diffusion path may be the width of the channel through which lithium ions move.

Figures 2 to 4 model the molecular structure of the sulfide-based solid electrolyte of Chemical Formula 1, Figure 2 shows the structure of Li ₇ P ₃ S ₁₀ Cl ₁ , Figure 3 shows the structure of Li ₇ P ₃ S ₁₀ Br ₁ , and Figure 4 models the structure of Li ₇ P ₃ S ₁₀ I ₁ . Specifically, looking at Figures 2 to 4, Li ₇ P ₃ S ₁₁ halogen atom When each of chlorine (Cl), bromine (Br), and iodine (I) is doped, the overall crystal structure is maintained without collapsing, but the structure of the tetrahedron doped with halogen atoms is distorted. Specifically, Li ₇ P _{3 S 10} The molecular structure of the sulfide-based solid electrolyte may be a mixture of the regular tetrahedron of PS4 and the tetrahedron of PS3X where X is substituted in PS4. Here, the PS3X may be structurally distorted (distorted) by doping with halogen atoms.

The charge distribution change modeling step (S200) is a step of calculating and modeling the charge density distribution of the sulfide-based solid electrolyte based on the molecular structure of the sulfide-based solid electrolyte obtained in the structure modeling step (S100).

The charge distribution change modeling step (S200) is a step of calibrating the difference between the charge distribution of each atom included in the molecular structure of the sulfide-based solid electrolyte and the charge distribution of the molecular structure itself of the sulfide-based solid electrolyte.

For example, the charge distribution change modeling step (S200) is for calculating the effect of the charge distribution of each atom included in the molecular structure of the sulfide-based solid electrolyte on the molecular structure of the sulfide-based solid electrolyte. The change in charge distribution can be measured by applying an electric field to the sulfide-based solid electrolyte to calculate the charge density distribution of the sulfide-based solid electrolyte.

Specifically, the charge density distribution of the sulfide-based solid electrolyte can be calculated using DFT theory (Density functional theory). Plane-wave basis set and norm-conserving pseudopotentials are performed in Quantum Espresso to calculate the charge density distribution of the sulfide-based solid electrolyte.

Figures 5 to 7 are images modeled by calculating the charge density distribution of the sulfide-based solid electrolyte in the charge distribution change modeling step of the analysis method of the sulfide-based solid electrolyte using computer simulation according to an embodiment of the present invention. Specifically, Figures 5 to 7 model the charge distribution change for the molecular structure of the sulfide-based solid electrolyte of Figures 2 to 4, and Figure 5 shows the charge density distribution of Li ₇ P ₃ S ₁₀ Cl ₁ (Figure 2 ), Figure 6 shows the charge density distribution of Li ₇ P ₃ S ₁₀ Br ₁ (Figure 3), and Figure 7 shows the charge density distribution of Li ₇ P ₃ S ₁₀ I ₁ (Figure 4). In Figures 5 to 7, the circled parts show the charge density distribution of the parts where Cl, Br, and I are substituted, respectively. The red part means the part with high charge density, and the blue part means the part with low charge density. It can be seen that the charge density gradually decreases in the order of Cl, Br, and I, and this is because electronegativity decreases as Cl, Br, and I go.

The diffusion path calculation step (S220) can be derived by calculating the width of the diffusion path through which lithium ions can diffuse through the charge distribution change modeling step (S200).

As shown in FIGS. 8 to 11, the diffusion path calculation step (S220) can represent the shape by calculating the width of the diffusion path after doping with the sulfide-based solid electrolyte. Looking at FIGS. 8 to 10, it can be seen that when doping halogen atoms compared to the existing sulfide-based solid electrolyte (Li ₇ P ₃ S ₁₁ ), the width of the diffusion path increases.

Specifically, Figure 8 shows that the width of the diffusion path increases over a wide area in the solid electrolyte of Li ₇ P ₃ S ₁₀ Cl doped with chlorine atoms, and Figure 9 shows that the width of the diffusion path increases over a wide area, and Figure 9 shows the solid electrolyte of Li ₇ P ₃ S ₁₀ Cl doped with bromine atoms. In the solid electrolyte, the width of the diffusion path increased in a very wide area, and in Figure 10, it was confirmed that in the solid electrolyte of Li ₇ P ₃ S ₁₀ I doped with iodine atoms, the width of the diffusion path increased in a narrow area. In other words, it was confirmed that the width of the lithium ion diffusion path increased by doping Cl, Br, and I, with Br increasing to the widest area and I increasing to the narrowest area.

Looking at Figure 11, the diffusion path of the existing sulfide-based solid electrolyte (Li ₇ P ₃ S ₁₁ ) is 0.2 to 0.3 Å, whereas the solid electrolyte of Li ₇ P ₃ S ₁₀ Cl doped with chlorine atoms has a diffusion path over a wide area. The width of the Li ₇ P ₃ S ₁₀ Br solid electrolyte doped with bromine atoms is on average 0.55 to 0.7 Å, and the width of the diffusion path in a wide area is on average 0.55 to 0.7 Å, and the Li ₇ P ₃ S ₁₀ Br doped with iodine atoms has an average width of 0.55 to 0.7 Å. In the solid electrolyte of I, the width of the diffusion path is on average 0.4 to 0.5 Å in some areas, which shows that the width of the diffusion path is greatly improved compared to the existing undoped solid electrolyte.

Doping of the chlorine atom improves the width of the diffusion path to approximately ~0.08Å in a wide area, iodine atom greatly improves the width of the diffusion path to approximately ~0.12Å in some areas, and bromine atoms diffuse to a very wide area. It greatly improves the width of the passageway to approximately ~0.3Å.

Considering the degree to which the width of the diffusion path has increased and the area where the increased diffusion path is provided, the average value is that the width of the diffusion path in a large area of the chlorine atom-doped Li ₇ P ₃ S ₁₀ Cl solid electrolyte is Compared to the existing solid electrolyte, the width of the diffusion path in the Li ₇ P ₃ S ₁₀ I solid electrolyte doped with iodine atoms is 0.1 to 0.15 Å larger than that of the existing solid electrolyte, and the width of the diffusion path is 0.1 to 0.15 Å larger than that of the existing solid electrolyte. It was confirmed that the diffusion path width of the atomically doped Li ₇ P ₃ S ₁₀ Br solid electrolyte was 0.15 to 0.4 Å larger in a wide area compared to the existing solid electrolyte.

The displacement calculation step (S300) is a step of calculating the displacement of at least one atom included in the molecular structure of the sulfide-based solid electrolyte that has undergone the charge distribution change modeling step.

Specifically, in the displacement calculation step (S300), the amplitude can be obtained by calculating the displacement of at least one atom included in the molecular structure of the sulfide-based solid electrolyte that has undergone the charge distribution change modeling step.

More specifically, the displacement calculation step (S300) uses the following formula 1 through Car-Parrinello molecular dynamics to calculate at least one atom among the atoms included in the molecular structure of the sulfide-based solid electrolyte. You can calculate the mean square displacement (MSD) of:

[Equation 1]

In Equation 1, t _o is the reference time (time origin), n _t is the total number of t _o , N is the total number of atoms, and t is the measurement time. R _i (t) is the position of the i ^th atom at t.

The displacement calculation step (S300) is the displacement of the mean square of lithium and sulfur atoms included in the molecular structure of the sulfide-based solid electrolyte using Equation 1 through Car-Parrinello molecular dynamics. (MSD) can be calculated. Specifically, in the displacement calculation step (S300), the MSD is measured for all atoms included in the molecular structure of the sulfide-based solid electrolyte. For example, the MSD of sulfur means the MSD for all sulfur atoms in the sulfide-based solid electrolyte.

Figure 12 calculates the mean square displacement of sulfur atoms and lithium of the sulfide-based solid electrolyte of Chemical Formula 1 (Li ₇ P ₃ S ₁₀ Cl ₁ , Li ₇ P ₃ S ₁₀ Br _1, and Li ₇ P ₃ S ₁₀ I ₁ ). This is a graph expressed in terms of amplitude.

The upper drawing of FIG. 12 is a graph showing the mean square displacement of each sulfur (S) atom when chlorine (Cl), bromine (Br), and iodine (I) are doped in a sulfide-based solid electrolyte, and the lower drawing is a graph showing the mean square displacement of each sulfur (S) atom. This is a graph showing the mean square displacement of each lithium (Li) atom when chlorine (Cl), bromine (Br), and iodine (I) are doped in a sulfide-based solid electrolyte.

Specifically, looking at Figure 12, the mean square displacement (MSD) of sulfur atoms and the mean square displacement (MSD) of lithium atoms increased the most for bromine, followed by iodine and chlorine.

Referring to the MSD of sulfur, it was confirmed that the structural stability of the solid electrolyte was relatively reduced due to doping of halogen elements, with bromine (Br) showing the lowest structural stability and chlorine (Cl) showing the highest structural stability. indicated. Referring to the MSD of lithium, it was confirmed that diffusion of cations occurs simultaneously with the vibration of the tetrahedron within the solid electrolyte. In other words, it was confirmed that the easier the tetrahedron vibrates (lower the structural stability), the faster the diffusion of cations proceeds.

Through this, it can be seen that in the solid electrolyte doped with bromine (Br), sulfur (S) atoms vibrate the most (top drawing), and the more sulfur (S) atoms vibrate in the solid electrolyte, the higher the diffusivity of lithium. It was confirmed that this increased (lower drawing).

The ionic conductivity prediction step (S400) is a step of predicting ionic conductivity by calculating ionic conductivity using the calculated atomic displacement.

In the ion conductivity prediction step (S400), the diffusion coefficient (D) of lithium ions can be calculated using the following equation 2:

[Equation 2]

In Equation 2, Δr(t) is the average displacement (MSD) during the measurement time (t), and D is the diffusion coefficient of lithium ions. The measurement time (t) refers to the time for the movement of atoms through CP-MD calculations. For example, when t = 120ps, it means moving (vibrating) the atoms for 120ps.

In addition, in the ionic conductivity prediction step (S400), the ionic conductivity (σ) of the sulfide-based solid electrolyte of Chemical Formula 1 or Chemical Formula 2 is calculated using the diffusion coefficient (D) of lithium ions obtained by Equation 2 using Equation 3 below. You can:

[Equation 3]

In Equation 3 above, ρ is the molar density of lithium ions diffusing in the unit cell,

z is the charge of lithium ion (+1), D is the diffusion coefficient of lithium ion calculated in Equation 2 above, F is Faraday's constant, R is the gas constant, and T is the temperature of the tested environment expressed in absolute temperature. represents.

The unit cell refers to one all-solid lithium secondary battery, and T is the temperature of the tested environment and may be 223 to 363 K.

Figure 13 is a graph showing the diffusion coefficient of the sulfide-based solid electrolyte in the ionic conductivity prediction step of the analysis method of the sulfide-based solid electrolyte using transfer simulation according to an embodiment of the present invention.

Referring to Figure 13, it was confirmed that the diffusion coefficient (D) of lithium ions was the largest for bromine (Br), followed by chlorine (Cl) and iodine (I), and the ionic conductivity was determined by the diffusion coefficient of lithium ions ( Since it is directly proportional to D), it was confirmed that it appears in the same order.

After the ionic conductivity prediction step (S400), a step of selecting a sulfide-based solid electrolyte with relatively high ionic conductivity from the sulfide-based solid electrolyte based on the predicted ionic conductivity may be further included.

In the step of selecting the sulfide-based solid electrolyte, a sulfide-based solid electrolyte with relatively high ionic conductivity can be selected by comparing the predicted ionic conductivity of the sulfide-based solid electrolyte of Formula 1 or Formula 2 using the computer simulation of the present invention. there is.

In addition, the present invention provides an all-solid-state battery containing a sulfide-based solid electrolyte designed by the above-described sulfide-based solid electrolyte design method.

The all-solid-state battery according to the present invention includes a positive electrode containing a positive electrode active material; A solid electrolyte layer containing a sulfide-based solid electrolyte; And it may include a negative electrode containing a negative electrode active material.

Specifically, the all-solid-state battery includes a positive electrode containing a positive electrode active material; A solid electrolyte layer formed on the anode and containing a sulfide-based solid electrolyte; and a negative electrode formed on the solid electrolyte layer and including a negative electrode active material.

The sulfide-based solid electrolyte included in the solid electrolyte layer may be a sulfide-based solid electrolyte of the following Chemical Formula 1 or Chemical Formula 2:

[Formula 1]

Li _a P _c S _d X _e

[Formula 2]

Li _a M _b P _c S _d X _e

In Formula 1 or Formula 2,

X is at least one of fluorine (F), chlorine (Cl), bromine (Br), iodine (I), selenium (Se), and tellurium (Te),

M is silicon (Si), germanium (Ge), tin (Sn), or lead (Pb),

7≤a≤12, 1≤b≤2, 1≤c≤3, 10≤d≤12, 0<e≤2.

Specifically, in Formula 1 or Formula 2, ), germanium (Ge), tin (Sn), or lead (Pb), and 9≤a≤12, 1≤b≤2, 1≤c≤2, 10≤d≤12, 0<e≤2. More specifically, in Formula 1, a is 7, c is 3, d is 10, and e is 1, and in Formula 2, a may be 10, b may be 1.5, c may be 1.5, d may be 11.5, and e may be 0.5. .

Additionally, in the sulfide-based solid electrolyte of Formula 1 or Formula 2, X may be bromine (Br). As described above, when .

The positive electrode can be manufactured by coating and drying a positive electrode slurry formed by mixing a positive electrode active material, sulfide-based solid electrolyte particles, a conductive material, a binder, and a solvent on a metal substrate such as aluminum foil. Additionally, the positive electrode slurry may further include an ionic liquid.

The positive electrode active material may be a metal oxide containing lithium that can electrochemically insert or desorb lithium through a redox reaction. For example, the positive electrode active material is lithium cobalt-based such as LiCoO2, lithium nickel-based such as LiNiO2, and lithium such as LiMn2O4. It may include manganese-based, lithium vanadium-based such as LiV2O5, and lithium iron-based such as LiFeO2. Additionally, NCM material may be used as the positive electrode active material. That is, the positive electrode active material can be LiNixCoyMnzO2 (x+y+z=1), LiNixCoyMnzMaO2 (x+y+z+a=1), where M is B, Al, Ga, In, Si, Ge, Sn, Pb. , As, Sb, Bi, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Y, Zr, Nb, Mo, Tc, Ru, Rh, Pd, Ag, Hf, Ta, or W, etc. You can.

The sulfide-based solid electrolyte particles may include the same material as the solid electrolyte according to Chemical Formula 1 or Chemical Formula 2 described above.

The conductive material is not particularly limited as long as it is a conductive material used in batteries, but includes graphene, carbon nanotubes, Ketjen black, activated carbon, Super p carbon in powder form, Denka in rod form, or vapor grown carbon fiber (VGCF). ) may include.

As a binder, polymer compounds of fluorine-based, diene-based, acrylic-based, and silicone-based polymers can be used. For example, the binder includes nitrile butadiene rubber (NBR), polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF), It may be carboxymethyl cellulose (CMC), styrene butadiene rubber (SBR), polyimide, etc.

Ionic liquids have little reactivity with sulfide-based solid electrolyte particles and are materials with excellent thermal stability, and can provide an additional ion transfer path by being distributed in the pores between sulfide-based solid electrolyte particles. The ionic liquid may include at least one cation and at least one anion.

The negative electrode can be manufactured by coating and drying a negative electrode slurry formed by mixing a negative electrode active material, sulfide-based solid electrolyte particles, a conductive material, a binder, and a solvent on copper foil, etc. Additionally, the cathode slurry may further include an ionic liquid.

The negative electrode active material may be a material capable of electrochemically inserting or desorbing lithium through a redox reaction. For example, the negative electrode active material may include metallic lithium or a LiAl-based, LiAg-based, LiPb-based, LiSi-based, or LiIn-based alloy alloyed with lithium.

In addition, the negative electrode active material can be made of general carbon materials such as non-graphitized carbon obtained by carbonizing graphite or resin, graphitized carbon obtained by heat-treating coke, and fullerene, and TiO ₂ and SnO ₂ with a potential relative to lithium of less than 2 V. The same metal oxide may be used, but it is not limited thereto. In particular, graphite, carbon fiber, activated carbon, etc. can be used as the negative electrode active material.

The negative electrode may be manufactured using the same materials and methods as the positive electrode except for the negative electrode active material.

The anode may include a positive electrode current collector on one side of the positive electrode, and may include a negative electrode current collector on one side of the negative electrode, and the negative electrode current collector may include one or more selected from copper, nickel, silver, and stainless steel (SUS), , the positive electrode current collector may include one or more types selected from aluminum, aluminum alloy, titanium, and stainless steel (SUS).

Claims (10)

A method of designing a sulfide-based solid electrolyte for an all-solid lithium secondary battery using transfer simulation,
A structural modeling step of modeling the molecular structure of the sulfide-based solid electrolyte;
A charge distribution change modeling step of calculating and modeling the charge density distribution of the molecular structure of the sulfide-based solid electrolyte;
A displacement calculation step of calculating the displacement of at least one atom included in the molecular structure of the sulfide-based solid electrolyte that has undergone the charge distribution change modeling step; and
It includes an ionic conductivity prediction step of calculating ionic conductivity using the calculated atomic displacement,
In the structural modeling step, the sulfide-based solid electrolyte includes the following Chemical Formula 1,
The structural modeling step uses the Quantum Espresso program based on first principles calculations,
The charge distribution change modeling step includes calibrating the difference between the charge distribution of each atom included in the sulfide-based solid electrolyte and the charge distribution of the sulfide-based solid electrolyte, and applying an electric field to the sulfide-based solid electrolyte to generate the charge. Including measuring changes in distribution,
The ionic conductivity prediction step uses computer simulation to calculate the diffusion coefficient (D) of lithium ions using Equation 2 below,
The ionic conductivity prediction step is to calculate the ionic conductivity (σ) of the sulfide-based solid electrolyte of Formula 1 from the calculated diffusion coefficient (D) of lithium ions using Equation 3 below. Sulfide-based solid electrolyte using computer simulation Design method:
[Formula 1]
LiaPcSdXe
In Formula 1,
X is at least one of chlorine (Cl), bromine (Br), and iodine (I),
7≤a≤12, 1≤c≤3, 10≤d≤12, 0<e≤2.
[Equation 2]

In Equation 2, Δr(t) is the average displacement (MSD) during the measurement time (t), and D is the diffusion coefficient of lithium ions.
[Equation 3]

In Equation 3 above, ρ is the molar density of lithium ions diffusing in the unit cell,
z is the charge of lithium ion (+1), D is the diffusion coefficient of lithium ion calculated in Equation 2 above, F is Faraday's constant, R is the gas constant, and T is the temperature of the tested environment expressed in absolute temperature. represents. delete delete delete According to paragraph 1,
A method for designing a sulfide-based solid electrolyte using computational simulation further comprising a diffusion path calculation step between the charge distribution change modeling step and the displacement calculation step. According to paragraph 1,
The displacement calculation step is the mean square displacement (mean) of at least one of the atoms included in the molecular structure of the sulfide-based solid electrolyte using Equation 1 below through Car-Parrinello molecular dynamics. Design method of sulfide-based solid electrolyte using computer simulation to calculate square displacement:
[Equation 1]

In Equation 1, t _o is the reference time (time origin), n _t is the total number of t _o , N is the total number of atoms, and t is the measurement time. R _i (t) is the position of the i ^th atom at t . delete delete According to paragraph 1,
In Formula 1, X is bromine (Br). Design method of a sulfide-based solid electrolyte using computer simulation. An all-solid-state battery comprising a sulfide-based solid electrolyte designed according to any one of claims 1, 5, 6, and 9.