KR20190088333A - Electrode for solid electrolyte battery and solid electrolyte battery including the same - Google Patents

Abstract

The present invention relates to an electrode for a solid electrolyte battery comprising an electrode current collector and an electrode active material layer formed on the electrode current collector. The electrode active material layer comprises: an electrode active material; a conductive material; a solid electrolyte; and an electrolyte salt. The present invention relates to an electrode for a solid electrolyte battery further comprising a powder layer coated on the electrode active material layer and made of a plasticizer present in a solid phase at 15-25°C, and to a solid electrolyte battery comprising the electrode. According to the present invention, life characteristics of the solid electrolyte battery can be prevented from being lowered.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to an electrode for a solid electrolyte cell and a solid electrolyte cell including the electrode.

The present invention relates to an electrode for a solid electrolyte cell and a solid electrolyte cell including the electrode. More particularly, the present invention relates to an electrode for a solid electrolyte cell capable of imparting ion conductivity to a gap generated at an interface between the electrode and the separator, .

A lithium ion battery using a liquid electrolyte is a structure in which a cathode and an anode are partitioned by a separator, so that if the separator is damaged due to deformation or external impact, a short circuit may occur, which may lead to overheating or explosion. Therefore, development of a solid electrolyte capable of ensuring safety in the field of lithium ion secondary batteries is a very important task.

The lithium secondary battery using the solid electrolyte has an advantage that the safety of the battery is enhanced, leakage of the electrolyte is prevented, reliability of the battery is improved, and a thin-type battery is easily manufactured. In addition, since lithium metal can be used as a cathode, the energy density can be improved. Accordingly, a small-sized secondary battery and a high-capacity secondary battery for an electric automobile are expected to be applied to the next generation battery.

On the other hand, in the case of a solid electrolyte cell to which a solid electrolyte is applied, since both the electrode and the separator are in a solid state and do not contain a liquid electrolyte, voids are generated at the interface between the electrode (anode and / or cathode) and the separator. These voids exist in a dead space without ionic conductivity.

Particularly, when the surface of the electrode active material layer is uneven due to the shape of the electrode active material, the bunching of the conductive material, and the floating of the polymer binder, more voids are generated and the resistance between the electrode and the separator becomes large. And it is a problem.

Accordingly, a problem to be solved by the present invention is to provide an electrode for a solid electrolyte battery which enables penetration of an electrolyte into a gap formed at an interface between an electrode (electrode active material layer) and a separator, such as a liquid electrolyte cell, And a solid electrolyte cell.

According to an aspect of the present invention, there is provided an electrode for a solid electrolyte cell including an electrode current collector and an electrode active material layer formed on the electrode current collector, wherein the electrode active material layer includes an electrode active material, a conductive material, a solid electrolyte, And a powder layer formed on the electrode active material layer and made of a plasticizer present in a solid phase at 15 to 25 ° C. The present invention also provides an electrode for a solid electrolyte battery.

The plasticizer may be selected from the group consisting of ethylene carbonate (EC), polyethylene glycol (PEG) having a weight average molecular weight of 1,000 or more, succinonitrile (SN) and cyclic phosphate (CP) Or a mixture of two or more thereof.

The powder layer may be 0.1 to 30 wt% of the total weight of the electrode active material layer.

The electrode active material may be a positive electrode active material or a negative electrode active material.

According to another aspect of the present invention, there is provided a solid electrolyte battery including a positive electrode, a negative electrode, and a separator interposed between the positive electrode and the negative electrode, wherein the positive electrode or the negative electrode is formed of a material for a solid electrolyte battery according to the present invention Wherein the solid electrolyte is an electrode.

At this time, the solid electrolyte cell may be such that the powder layer is phase-changed into a liquid phase, and penetrates into the gap formed between the electrode active material layer and the separator.

A battery module including the solid electrolyte battery according to the present invention as a unit cell and a battery pack including the same are provided.

According to an embodiment of the present invention, a powder layer made of a solid plasticizer additionally provided on an electrode for a solid electrolyte battery is phase-changed into a liquid phase during the activation process during the manufacturing process of the solid electrolyte battery, It can penetrate the voids formed on the interface and impart ion conductivity to the voids.

As a result, it is possible to prevent the resistance from increasing at the interface between the electrode and the separator, and to prevent deterioration of the life characteristics of the solid electrolyte battery.

In addition, the plasticizer of the present invention has a high ion conductivity and can further improve the output performance of the battery. Also, the oxidation reactivity is higher than that of the anode, so that it can be used stably on the anode.

BRIEF DESCRIPTION OF THE DRAWINGS The accompanying drawings, which are incorporated in and constitute a part of the specification, illustrate preferred embodiments of the invention and, together with the description of the invention given above, serve to further the understanding of the technical idea of the invention, It should not be construed as limited.
1 is a graph showing capacity retention ratios of batteries according to Examples 1 and 2 and Comparative Example.

Hereinafter, the present invention will be described in detail with reference to the drawings. The terms and words used in the present specification and claims should not be construed as limited to ordinary or dictionary terms and the inventor may appropriately define the concept of the term in order to best describe its invention It should be construed as meaning and concept consistent with the technical idea of the present invention.

Therefore, the embodiments described in the present specification and the constitutions described in the drawings are merely the most preferred embodiments of the present invention, and are not intended to represent all of the technical ideas of the present invention. Therefore, It is to be understood that equivalents and modifications are possible.

An electrode for a solid electrolyte battery according to an aspect of the present invention is an electrode for a solid electrolyte battery including an electrode current collector and an electrode active material layer formed on the electrode current collector, And a powder layer comprising a solid electrolyte and an electrolyte salt and being coated on the electrode active material layer and made of a plasticizer present in a solid phase at 15 to 25 占 폚.

The powder layer made of the plasticizer is exposed to a temperature environment at or above the melting point of the plasticizer during the activation process during the manufacturing process of the battery so that the plasticizer changes into a liquid phase and penetrates into voids formed at the interface between the electrode and the separator , Ion conductivity can be imparted to the pores. As a result, it is possible to prevent the resistance from increasing at the interface between the electrode and the separator, and to prevent deterioration of the life characteristics of the solid electrolyte battery.

The plasticizer is present in a solid phase at room temperature, but any material capable of being changed into a liquid state at a high temperature can be used. Specifically, ethylene carbonate (EC) having a melting point of about 37 캜, a melting point of about 35 캜 (Ethylene glycol) (PEG) having a weight average molecular weight of 1,000 or more, succinonitrile (SN) having a melting point of about 57 占 폚, and cyclic phosphate (CP) having a melting point of about 65 占 폚. Or a mixture of two or more thereof.

Propylene carbonate (PC) having a melting point of about -49 ° C, polyethylene glycol (PEG) having a weight average molecular weight of 600 or less, polyethylene glycol dimethyl ether, PEGDME), dioctyl phthalate (DOP) having a melting point of about -50 ° C, and diethyl phthalate (DEP) having a melting point of about -4 ° C exist in a liquid state at room temperature, It is difficult to apply it as a plasticizer of the present invention.

As an example of the plasticizer according to the present invention, the melting point of ethylene carbonate is about 37 占 폚, and it exists in a solid state at room temperature. When a battery is exposed to a temperature environment higher than the melting point of ethylene carbonate in the course of manufacturing a solid electrolyte cell including an electrode provided with a powder layer made of ethylene carbonate, Is phase-changed into a liquid phase, reacts with the electrolyte salt in the electrode, and then remains in a liquid phase even at 37 ° C or lower. This state is changed into a liquid phase so that it penetrates into the voids formed at the interface between the electrode and the separator, and ion conductivity can be imparted to the voids. As a result, it is possible to prevent the resistance from increasing at the interface between the electrode and the separator, and to prevent deterioration of the life characteristics of the solid electrolyte battery.

The ethylene carbonate is used in general non-aqueous electrolytes, and is applicable to most batteries and has an advantage of being free of impurities. In particular, such ethylene carbonate has a high ion conductivity and can further improve the output performance of the battery. Also, the oxidation reactivity (6.2 V) is higher than that of the anode, which is advantageous in that it can be used stably in the anode.

Polyethylene glycol, succinonitrile (SN) and cyclic phosphate (CP) having a weight average molecular weight of not less than 1,000 and used as the plasticizer of the present invention as well as the above ethylene carbonate have a similar performance to that of the ethylene carbonate .

Here, the powder layer may be 0.1 to 30 wt% of the total weight of the electrode active material layer.

If the content of the powder layer is less than the above-described range, the effect is insignificant. If the content of the powder layer is more than the above-mentioned range, it is similar to a battery using a liquid electrolyte.

In the present invention, the electrode active material may be a positive electrode active material or a negative electrode active material.

Here, the positive electrode active material may be any material that can be used as a positive electrode active material of a lithium secondary battery. For example, a layered compound such as lithium cobalt oxide (LiCoO ₂ ) or lithium nickel oxide (LiNiO ₂ ) or a compound substituted with one or more transition metals; The formula Li _{1 + x} Mn _{2 - x} O ₄ (Where x is 0 to 0.33), lithium manganese oxides such as LiMnO ₃ , LiMn ₂ O ₃ and LiMnO ₂ ; Lithium copper oxide (Li ₂ CuO ₂ ); Vanadium oxides such as LiV ₃ O ₈ , LiFe ₃ O ₄ , V ₂ O ₅ and Cu ₂ V ₂ O ₇ ; Formula _{LiNi 1 - x M x O 2} ( where, the M = Co, Mn, Al, Cu, Fe, Mg, B or Ga, x = 0.01 ~ 0.3 Im) Ni site type lithium nickel oxide which is represented by; Formula _{LiMn 2-x M x O 2} ( where, M = Co, Ni, Fe , Cr, and Zn, or Ta, x = 0.01 ~ 0.1 Im) or Li ₂ Mn ₃ MO ₈ (where, M = Fe, Co, Ni, Cu, or Zn); A lithium manganese composite oxide having a spinel structure represented by LiNi _x Mn _{2 - x} O ₄ ; LiMn ₂ O _{4 in} which a part of Li in the formula is substituted with an alkaline earth metal ion; Disulfide compounds; Fe ₂ (MoO ₄ ) ₃ , LiNi _{0 . 8} Co _{0 . 1} Mn _{0 . 1} O ₂ , and the like. However, the present invention is not limited to these.

The negative electrode active material can be used without limitation as long as it can be used as a negative electrode active material of a lithium secondary battery. Carbon, such as, for example, non-graphitized carbon, graphite carbon (natural graphite, artificial graphite); _{Li x Fe 2 O 3 (0≤x≤1} ), Li x WO 2 (0≤x≤1), Sn x Me 1 - x Me 'y O z (Me: Mn, Fe, Pb, Ge; Me' : Metal complex oxides such as Al, B, P, Si, Group 1, Group 2, Group 3 elements of the periodic table, Halogen, 0 < x < Lithium metal; Lithium alloy; Silicon-based alloys; Tin alloy; _{SnO, SnO 2, 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, and Bi ₂ O ₅ ; Conductive polymers such as polyacetylene; Li-Co-Ni-based materials; Titanium oxide; Lithium titanium oxide, and the like can be used. In one specific embodiment, the negative electrode active material may include a carbon-based material and / or Si.

In the present invention, the electrode current collector may exhibit electrical conductivity such as a metal plate or the like, and may be appropriately used depending on the polarity of the collector electrode known in the secondary battery field.

The electrode may further include a polymer binder depending on the kind of the solid electrolyte and the desired performance. The content of the binder may be 1 to 20 parts by weight, preferably 1 to 20 parts by weight, based on 100 parts by weight of the electrode active material. 10 parts by weight.

Examples of the polymeric binder include polyvinylidene fluoride-hexafluoropropylene (PVDF-co-HFP), polyvinylidene fluoride (PVDF), polyacrylonitrile, poly Various kinds of binders such as polymethyl methacrylate, styrene butadiene rubber (SBR), and carboxyl methyl cellulose (CMC) can be used.

In addition, the conductive material is not particularly limited as long as it has electrical conductivity without causing chemical changes in the battery, for example, graphite such as natural graphite or artificial graphite; Carbon black such as carbon black, acetylene black, ketjen black, channel black, furnace black, lamp black, and summer black; 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; Polyphenylene derivatives, and the like, or a mixture of two or more thereof.

The solid electrolyte of the present invention preferably uses a solid electrolyte having excellent oxidation stability in the case of a positive electrode and a solid electrolyte having excellent reduction stability in the case of a negative electrode. Since the solid electrolyte of the present invention mainly plays the role of transferring lithium ions in the electrode, any material having a high ion conductivity, for example, 10 ^-5 s / m or more, preferably 10 ^-4 s / m or more And is not limited to specific components.

Here, the solid electrolyte may be a polymer solid electrolyte formed by adding a polymer resin to a solvated electrolyte salt, or a polymer containing an organic electrolyte, an ionic liquid, a monomer, or an oligomer containing an organic solvent and an electrolyte salt in a polymer resin Gel electrolyte, and may be a sulfide-based solid electrolyte having a high ion conductivity or an oxide-based solid electrolyte having an excellent stability.

Here, the polymer solid electrolyte may be, for example, a polyether polymer, a polycarbonate polymer, an acrylate polymer, a polysiloxane polymer, a phosphazene polymer, a polyethylene derivative, an alkylene oxide derivative, a phosphate ester polymer, Agitation lysine, polyester sulfide, polyvinyl alcohol, polyvinylidene fluoride, polymers including ionic dissociation groups, and the like. The polymer solid electrolyte may be a branched polymer in which amorphous polymers such as PMMA, polycarbonate, polysiloxane (pdms) and / or phosphazene are copolymerized with a comonomer in a main chain of PEO (poly ethylene oxide) as a polymer resin, a comb-like polymer, and a crosslinked polymer resin, and may be a mixture of the polymers.

In addition, the polymer gel electrolyte includes an organic electrolyte including an electrolyte salt and a polymer resin, and the organic electrolyte includes 60 to 400 parts by weight of the polymer resin. The polymer to be applied to the gel electrolyte is not limited to a specific component but may be, for example, a polyether polymer, a PVC polymer, a PMMA polymer, a polyacrylonitrile (PAN), a polyvinylidene fluoride (PVdF) Poly (vinylidene fluoride-hexafluoro propylene: PVdF-HFP, and the like. And may be a mixture of the above polymers.

The electrolyte salt may be represented by Li ⁺ X ^- as an ionizable lithium salt. The lithium salt is preferably LiTFSI, LiCl, LiBr, LiI, LiClO 4, LiBF 4, LiB 10 Cl 10, LiPF 6, LiAsF 6, LiSbF 6, LiAlCl 4, LiSCN, LiCF 3 CO 2, LiCH 3 SO 3, LiCF ₃ SO ₃ , LiN (SO ₂ CF ₃ ) ₂ , LiN (SO ₂ C ₂ F ₅ ) ₂ , LiC ₄ F ₉ SO ₃ , LiC (CF ₃ SO ₂ ) ₃ , (CF ₃ SO ₂ ) Lithium chloroborate, lithium lower aliphatic carboxylate, lithium imide 4-phenylborate, and combinations thereof. And more preferably lithium bistrifluoromethanesulfonimide (LiTFSI).

On the other hand, the electrode for a solid electrolyte battery can be manufactured by coating an electrode active material slurry on an electrode current collector and then drying the electrode active material slurry.

At this time, the coating method may be a known coating method such as slot die, gravure coating, spin coating, spray coating, roll coating, curtain coating, extrusion, casting, screen printing, or inkjet printing.

Also, the electrode active material slurry may be dried by heating, evaporating the solvent by irradiating heat, E-beam, gamma ray, or UV (G, H, I-line)

Through such drying, the dispersion medium in the electrode active material slurry is volatilized and removed, but the remaining components remain unvolatilized and form an electrode active material layer.

At this time, the dispersion medium which can be used is not particularly limited as long as it is usually used in the production of an electrode active material slurry. Specifically, it may be isopropyl alcohol, N-methylpyrrolidone (NMP), acetone, or the like.

According to another aspect of the present invention, there is provided a solid electrolyte battery comprising a positive electrode, a negative electrode, and a separator interposed between the positive electrode and the negative electrode, wherein the positive electrode or the negative electrode comprises the electrode for a solid electrolyte battery according to the present invention .

At this time, the ethylene carbonate powder layer is phase-changed into a liquid phase through the general evaluation condition or the charging / discharging process of the solid electrolyte cell, and penetrates into the gap formed between the electrode active material layer and the separator, The ionic conductivity can be imparted. As a result, it is possible to prevent the resistance from increasing at the interface between the electrode and the separator, and to prevent deterioration of the life characteristics of the solid electrolyte battery.

The separator according to the present invention is interposed between a negative electrode and a positive electrode, and serves to electrically insulate the positive electrode from the negative electrode and to pass lithium ions. The separator is not particularly limited as long as it is used as a polymer separator membrane used in a conventional solid electrolyte battery field.

According to another aspect of the present invention, there is provided a battery module including the lithium secondary battery as a unit battery, a battery pack including the battery module, and a device including the battery pack as a power source.

Here, specific examples of the device may include, but not limited to, an electric vehicle, a hybrid electric vehicle, a plug-in hybrid electric vehicle, or a power storage system.

Hereinafter, the present invention will be described in further detail with reference to the following examples. However, the following examples are for illustrative purposes only and are not intended to limit the scope of the present invention.

1. Example 1

(1) Preparation of positive electrode

2 parts by weight of PVDF as a binder was dissolved in an acetonitrile solvent to prepare a binder solution, and 3 parts by weight of carbon black (Super C65) as a conductive material was added to the binder solution to prepare a mixed solution.

Thereafter, the mixed solution _{NCM811 (LiNi 0. 8 Co 0} . 1 Mn 0. 1 O 2) 80 parts by weight, as a solid electrolyte of polyethylene oxide (PEO) 9 parts by weight of an electrolyte salt LITFSI 5 parts by weight as a positive electrode active material After the addition, a solvent was further added in consideration of viscosity to prepare a cathode active material slurry. The cathode active material slurry thus prepared was applied to an aluminum current collector having a thickness of 20 탆, and then vacuum dried at 120 캜 for 24 hours to prepare a cathode.

Subsequently, a liquid ethylene carbonate plasticizer was applied on the dried cathode active material layer, and then the electrode was left at room temperature to form an ethylene carbonate powder layer on the electrode. At this time, the powder layer was made to be 1 wt% based on the total weight of the electrode active material layer.

(2) Manufacture of batteries

A coin type half cell was fabricated using the prepared positive electrode and a lithium metal negative electrode. Specifically, a battery was fabricated with a polymer separator film (PEO + LiFSI, 20: 1 (molar ratio)) having a thickness of 50 mu m interposed between the positive electrode and the negative electrode.

2. Example 2

2 parts by weight of PVDF as a binder was dissolved in an acetonitrile solvent to prepare a binder solution, and 3 parts by weight of carbon black (Super C65) as a conductive material was added to the binder solution to prepare a mixed solution.

Thereafter, the mixed solution _{NCM811 (LiNi 0. 8 Co 0} . 1 Mn 0. 1 O 2) 80 parts by weight, as a solid electrolyte of polyethylene oxide (PEO) 9 parts by weight of an electrolyte salt LITFSI 5 parts by weight as a positive electrode active material After the addition, a solvent was further added in consideration of viscosity to prepare a cathode active material slurry. The cathode active material slurry thus prepared was applied to an aluminum current collector having a thickness of 20 탆, and then vacuum dried at 120 캜 for 24 hours to prepare a cathode.

Subsequently, a liquid succinonitrile plasticizer was applied on the dried cathode active material layer, and then the electrode was allowed to stand at room temperature to form a succinonitrile powder layer on the electrode. At this time, the powder layer was made to be 1 wt% based on the total weight of the electrode active material layer.

(2) Manufacture of batteries

A coin type half cell was fabricated using the prepared positive electrode and a lithium metal negative electrode. Specifically, a battery was fabricated with a polymer separator film (PEO + LiFSI, 20: 1 (molar ratio)) having a thickness of 50 mu m interposed between the positive electrode and the negative electrode.

3. Comparative Example

A positive electrode and a battery were produced in the same manner as in Example 1, except that no ethylene carbonate powder layer was formed during the production of the positive electrode.

4. Measurement of battery capacity retention rate

The cells prepared in Examples 1 and 2 and Comparative Example were stored at 60 DEG C for 10 minutes. Through this process, the ethylene carbonate and succinonitrile contained in the batteries of Examples 1 and 2 were converted into a liquid phase.

Thereafter, the batteries of Examples 1 and 2 and Comparative Example were charged / discharged and the capacity retention rate was measured and shown in Fig. At this time, charging / discharging was carried out at a temperature of 60 ° C at 0.1 C, a charging voltage was 4.25 V, and a discharging voltage was 3.0 V.

Referring to FIG. 1, as the charge / discharge of the battery progressed, the capacity retention rate of the batteries of the Examples was larger than that of the comparative example, and the difference in the capacity retention rate tended to increase as the number of cycles increased.

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it is to be understood that the invention is not limited to the disclosed exemplary embodiments. It will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention.

Claims (8)

An electrode current collector, and an electrode active material layer formed on the electrode current collector. The present invention relates to an electrode for a solid electrolyte battery,
Wherein the electrode active material layer includes an electrode active material, a conductive material, a solid electrolyte, and an electrolyte salt,
Further comprising a powder layer formed on the electrode active material layer and made of a plasticizer present in a solid phase at 15 to 25 占 폚. The method according to claim 1,
The plasticizer may be selected from the group consisting of ethylene carbonate (EC), polyethylene glycol (PEG) having a weight average molecular weight of 1,000 or more, succinonitrile (SN) and cyclic phosphate (CP) Or a mixture of two or more thereof. The method according to claim 1,
Wherein the powder layer is 0.1 to 30 wt% of the total weight of the electrode active material layer. The method according to claim 1,
Wherein the electrode active material is a positive electrode active material or a negative electrode active material. A solid electrolyte battery comprising a positive electrode, a negative electrode, and a separator interposed between the positive electrode and the negative electrode,
The solid electrolyte battery according to any one of claims 1 to 3, wherein the anode or the cathode is an electrode for a solid electrolyte cell. 6. The method of claim 5,
In the solid electrolyte cell,
Wherein the powder layer is phase-changed into a liquid phase and penetrates into the gap formed between the electrode active material layer and the separator. A battery module comprising the solid electrolyte battery according to claim 5 as a unit cell. A battery pack comprising the battery module according to claim 7.

Images